Navigation for Profesional Pilots

Navigation for Professional Pilots

Ray Preston

2010


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Introduction:

This text was created for use in the course Avia 160 as part of the Selkirk College Professional Aviation Program, which leads to the Canadian Commercial Pilot License with Multi-engine and Instrument Rating. This text is intended as an adjunct to a 48 hour lecture series on the topic of navigation. Assignments, tests, and exams supplement this text and the lectures. Flight planning exercises include both VFR and IFR cross-countries. Students will become expert at preparing VNC maps and completing navlogs for VFR cross countries. They will also use LO charts and the Canada Air Pilot to plan IFR cross-countries. This book explains both theoretical and practical principles of flight navigation, including visual and radio navigation based on VOR, ADF, and DME. This course covers principles of intercepting and maintaining a radio course. It also covers flying DME arcs. An introduction to procedure turns is included. The text is supplemented by several computer simulations of the Selkirk College Aviation Intranet, which is on the web at Selair.selkirk.ca. Students in this course are expected to become expert at the use of the CR(or 6) navigation computer. This text was written based on the assumption that readers hold a private pilot license and as such have certain basic knowledge about aviation in general and navigation in particular.

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Table of Contents: Chapter 1 .......................................................................................................................................................13 Text Overview ...........................................................................................................................................13 Pilotage, Dead Reckoning and Radio Navigation .....................................................................................14 Sample Questions 1 ..................................................................................................................................16 Pressure and Density Altitude ...................................................................................................................18 The International Standard Atmosphere .........................................................................................18 Pressure Altitude .............................................................................................................................19 Density Altitude ...............................................................................................................................21 Sample Questions 2 ..................................................................................................................................23 Cold Temperature Corrections ..................................................................................................................23 Performance Charts ..................................................................................................................................28 Interpolation and Accurate Drawing Skill ........................................................................................28 Electronic Charts for the C-172P......................................................................................................29 Electronic Charts for the Travelair ...................................................................................................29 Performance Rules of Thumb ....................................................................................................................30 Weight and Balance Shift..........................................................................................................................31 Chapter 2 .......................................................................................................................................................35 Mass – Distance – Time, The Fundamental Concepts of Physics ..............................................................35 Definition of Velocity, and two useful deductions from the definition .................................................35 Velocity Expressed as Airspeed........................................................................................................35 True Airspeed (TAS) .........................................................................................................................36 Equivalent Airspeed (EAS) ...............................................................................................................37 Indicated and Calibrated Airspeed (IAS and CAS) ............................................................................37 ICE-T ................................................................................................................................................38 Heading (True, and Magnetic) ..................................................................................................................39 Page 5


Compass Deviation ...............................................................................................................................39 Wind and Drift ..........................................................................................................................................39 Wind Triangle: GS = TAS + Wind..........................................................................................................40 Definitions: Crosswind and Headwind..................................................................................................45 Drift Angle Defined ..........................................................................................................................46 Groundspeed Defined ......................................................................................................................46 Calculation of Crosswind and Tailwind ................................................................................................47 Determining XW, TW, da, and GS with a CR ........................................................................................48 Sample Problems: ............................................................................................................................49 Drift Estimation .........................................................................................................................................49 Estimate XW and TW ...........................................................................................................................50 Magic Number .....................................................................................................................................54 Estimation of Drift Based on Crosswind and Magic Number ...............................................................55 Two-bit Math ...................................................................................................................................56 Drift Estimation Challenge ........................................................................................................................58 Drift Estimation Summary ...............................................................................................................58 Chapter 3 .......................................................................................................................................................59 Introduction to Radio Navigation .............................................................................................................59 VOR, ILS, and DME Channel Pairing ..........................................................................................................59 VOR Reception Range ..........................................................................................................................61 VOR, ADF, DME – Final Thoughts..............................................................................................................63 GPS Navigation ....................................................................................................................................64 Bracketing .................................................................................................................................................64 Establishing the Brackets .....................................................................................................................66 “Beating” the Computerized Flying Instructor ................................................................................72 Break-out Logic ...............................................................................................................................72

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Bracketing Summary .......................................................................................................................73 Flying a DME ARC......................................................................................................................................74 DME Groundspeed During an ARC ..................................................................................................78 Intercepting a Course (PDT) ......................................................................................................................81 Outbound PDTs .........................................................................................................................................89 Random PDT practice................................................................................................................................91 Tracking and Intercepting Summary ....................................................................................................92 Chapter 4 .......................................................................................................................................................95 IFR Charts ..................................................................................................................................................95 LO Charts ..............................................................................................................................................95 HI Charts...............................................................................................................................................96 Overview of IFR System .............................................................................................................................96 Separation of IFR Aircraft .....................................................................................................................96 Preferred IFR Routes ............................................................................................................................96 IFR Alternate Airport ............................................................................................................................97 Chapter 5 .................................................................................................................................................... 101 The CR Computer ................................................................................................................................... 101 A Ratio Machine ........................................................................................................................... 101 Unit Conversions ........................................................................................................................... 103 Celsius to Fahrenheit Temperature Conversion ............................................................................ 106 Mach Number............................................................................................................................... 106 Speed Ratios – I.E. Groundspeed Checks ........................................................................................... 107 Miles per Minute .......................................................................................................................... 109 Time to a Station – ARC Speed ..................................................................................................... 109 Two IMPORTANT two-step CR Ratio Problems ............................................................................ 115 Standard Decent Gradient is 3° ......................................................................................................... 121

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TAS and CAS Conversions .................................................................................................................. 122 Derive CAS given TAS and Forecast Temperature ............................................................................. 124 Procedure for “Slow and Low” Airplanes...................................................................................... 125 Procedure for “Fast and High” Airplanes ..................................................................................... 127 Comparing Procedure for slow and fast Airplanes ....................................................................... 131 Sample Questions 5 ............................................................................................................................... 133 Chapter 6 .................................................................................................................................................... 137 The Canada Flight Supplement .............................................................................................................. 137 Weather and NOTAMS........................................................................................................................... 137 Chapter 7 .................................................................................................................................................... 139 Navigation Theory ................................................................................................................................. 139 Shape of the Earth............................................................................................................................. 139 Latitude ........................................................................................................................................ 139 Longitude...................................................................................................................................... 141 Great-circles ...................................................................................................................................... 143 Small Circles.................................................................................................................................. 144 Convergence ................................................................................................................................. 146 Rhumb-Line .................................................................................................................................. 146 Map Theory ....................................................................................................................................... 147 Lambert Conformal Conic Projection............................................................................................ 148 Transverse Mercator projection ................................................................................................... 151 True and Magnetic North (Variation) ........................................................................................... 153 Compass Deviation ....................................................................................................................... 155 Contour Lines and Hypsometric Tints ........................................................................................... 156 Map Legend.................................................................................................................................. 157 Map Scale ..................................................................................................................................... 158

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Grid Navigation ................................................................................................................................. 158 Grivation ....................................................................................................................................... 163 Plotting Lines of Position (LOP) .............................................................................................................. 163 Chapter 8 .................................................................................................................................................... 169 Flight Planning ....................................................................................................................................... 169 Definition of a Leg ............................................................................................................................. 169 Fly-by and Fly-over Waypoints ..................................................................................................... 169 Introduction to Nav-logs ........................................................................................................................ 171 Navlog Leg Groups ............................................................................................................................ 172 Ramp Fuel and Fuel Remaining ......................................................................................................... 175 Choosing a Set Heading Point (SHP) ............................................................................................. 175 Filling in the Navlog........................................................................................................................... 176 First Enroute leg (to TOC) ............................................................................................................. 178 Cruise Legs – Between Enroute Checkpoints ................................................................................ 179 Selection of Cruising Altitude ................................................................................................................. 182 Top of Descent .............................................................................................................................. 183 Contingencies ............................................................................................................................... 183 Approach at Destination .............................................................................................................. 184 Checkpoints leading to Alternate Airport ..................................................................................... 185 Approach at Alternate Airport ...................................................................................................... 185 Reserve ......................................................................................................................................... 185 Tips for the Electronic Nav-Log .............................................................................................................. 186 VFR Map Preparation Techniques.......................................................................................................... 186 Drawing a Line Across a 2-Sided Chart ......................................................................................... 188 Measuring Track and Distance .......................................................................................................... 188 Filling in a Flight Plan Form .................................................................................................................... 189

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Chapter 9 .................................................................................................................................................... 193 Mountain Cross Country ........................................................................................................................ 193 DR vs. Pilotage in Mountain Flying ................................................................................................... 193 Good-weather Mountain Cross-country ........................................................................................... 193 Set Heading Point(s) in the Mountains ......................................................................................... 193 Descent Point in the Mountains ................................................................................................... 194 Poor Weather Mountain Cross-country (Valley Crawl) ..................................................................... 194 In-flight Valley Navigation Procedures ......................................................................................... 195 Chapter 10 .................................................................................................................................................. 199 Time Saving Flight Planning Techniques ................................................................................................ 199 Block Flight Planning ......................................................................................................................... 199 Climb Penalty Planning ..................................................................................................................... 199 Chapter 11 .................................................................................................................................................. 203 Enroute Navigation Skills ....................................................................................................................... 203 Map Reading ................................................................................................................................ 203 Time Awareness ........................................................................................................................... 204 Reorienting if Lost ........................................................................................................................ 204 Navlog keeping ............................................................................................................................. 205 Top of Descent .............................................................................................................................. 206 Diversions ..................................................................................................................................... 206 Position Reports and Amending Flight Plan ................................................................................. 207 Hybrid Navigation Procedure – Landfall ................................................................................................ 208 Chapter 12 .................................................................................................................................................. 211 Oceanic Flight ........................................................................................................................................ 211 Point of No Return (PNR) .............................................................................................................. 211 Critical Point (CP) .......................................................................................................................... 214

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Appendix 1– C-172 Interpolation Tables ................................................................................................ 217 Appendix 2 - Inbound PDT Practice Sheet .............................................................................................. 219 Appendix 3 - Outbound PDT Practice Sheet ........................................................................................... 221 Appendix 4 – Definitions ........................................................................................................................ 223

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Chapter 1 Text Overview Everyone knows what it means to “have a plan.” In “flight planning” we develop a plan for a flight. For example your plan might require knowing: When we will leave When we will arrive Who will be on board What route we will take What will the weather be like What navigation equipment (from eyeballs, to VOR, to GPS, etc.) will be used What condition the airplane and its systems will be in What we will do if various contingencies such as weather, mechanical, or medical difficulties occur. Where we will park upon arrival Customs and other passenger handling arrangements Food and refreshments arrangement prior, during, and post flight Accommodation at destination Aircraft servicing at destination Customs arrangements ETC

The above list is not complete; the point being made here is that flight planning is a large undertaking covering many different items of concern regarding a flight. At an airline many people are employed to ensure that all the passenger handling aspects of flight planning are looked into. Experts also plan routes for optimum advantage (cost) taking wind, ATC fees, departure and arrival fees, etc. into account. The process can be very complex. For example, many international airline flights don’t fly by the shortest route for two reasons: For one every nation they over fly charges a fee, so flights may detour around some


airspace spending more money on fuel, but saving in the long run by avoiding high ATC fees. In addition, the shortest route is not always the quickest, if a strong tailwind (jet stream) can be located, or a strong headwind avoided. By the end of this course you must be fully competent at planning VFR flights, but, most commercial airline flights are IFR flights, and as such are governed by a set of regulations that you will learn to take into account during this course. For example, one requirement is to have an alternate airport to divert to in the event that landing at the primary destination becomes impossible. By the end of this course you will be fully competent to plan an IFR flight from any point within Canada to any other point. International flights will covered in second year. In this course we will concentrate on the planning time and fuel for a flight. Route selection will be comparatively simple. We will consider the preferred IFR routes published in the Canada Flight Supplement, and terrain and weather. We won’t usually concern ourselves with avoiding ATC fees or political boundaries because most of our flights will be domestic. Airline flight planners often adjust to avoid these, but we will concentrate on choosing an altitude that is optimum for the wind given a specified route. Flight logistics such as arranging food for passengers, where to park and service the airplane, etc won’t receive a lot of attention due to our limited time. But you must recognize that these things are crucial to real world commercial flight operations. You will learn where to find the required information, and some of these matters will be included in the exercises. After graduation, expect passenger handling and logistics aspects of flight planning to take considerably more of your time than calculating time and fuel. By the end of this course you should be able determine time and fuel for a given flight within a few minutes. For your commercial pilot flight test you are allowed 45 minutes, but that should be twice as much time as you actually need. Your skill at doing this level of basic flight planning quickly and accurately will free up the time for the logistics aspects of flight planning that your employer will expect you to master.

Pilotage, Dead Reckoning and Radio Navigation Two terms that will come up over and over are “pilotage” and “dead-reckoning.” Pilotage means flying from point to point by visually following features on the ground. It is the way you drive your car and it is often a practical way to fly an airplane. For example: to fly from Castlegar to Revelstoke simply follow the Columbia River. Dead-reckoning (DR) means to determine the one heading and time that will take the airplane directly to a point, allowing for wind. DR is by definition flight along a straight line path. Most of this course is devoted to learning how to dead-reckon. Radio navigation means that the location of the airplane is determined by referring to instruments such as VOR, ADF, or GPS. This is necessary when flying IFR. In this course you will learn the basics of IFR radio

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navigation. Radio navigation is NOT distinct from pilotage or DR; in fact both can be applied to radio navigation. In real-world VFR navigating, pilots use a combination of pilotage and DR. DR dominates on long flights, especially over terrain that lacks distinctive features. Any VFR flight over water must be a DR flight for example. Pilotage dominates on shorter flights, but it can only be used when the ground has distinctive features so that the pilot can accurately determine position visually. Even on a long flight some portions of all VFR flights require pilotage. Usually the leg just after takeoff until established at the set heading point requires pilotage. And the final circuit joining and landing is also a pilotage leg. DR is the most efficient means of navigation, but if the terrain has good, distinctive, features some pilotage is practical especially when doing things such as diverting around poor weather or special use airspace. Often some radio navigation will be used, even on a VFR flight – thus most flights require pilotage, DR, and radio navigation. In this course we will generally keeps these techniques separated for instructional purposes, but in the real world they should be used together to achieve an efficient flight with the lowest possible workload for the pilot.

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Sample Questions 1 1.

2.

3.

4.

A pilot sees a local shopping mall and flies toward it. a.

This is DR navigation

b.

This is pilotage navigation

c.

This is radio navigation

d.

This is two or more of the above

A pilot is over a town s/he recognizes and turns south to join left base for the active runway a.


b.


c.


d.


A pilot tunes a VOR and determines the track to the station is 030°. S/he then turns to that heading without concern for the strong westerly wind. The pilot turns left, then right, then left again, following the VOR needle until s/he gets to the station. a.


b.


c.


d.


A pilot is trying to find a small lake. S/he flies a heading of 220 until the lake comes into sight, then flies directly to the lake. a.


b.


c.


d.


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5.

A pilot follows a road to a particular intersection then flies heading 360 until the airport comes into view. a.


b.


c.


d.


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Pressure and Density Altitude

The International Standard Atmosphere One of the valuable benefits of the International Standard Atmosphere (ISA) is that it makes it possible for manufacturers of aircraft to provide data for pilots to use in flight planning. An aircraft’s Pilot Operating Handbook (POH) specifies how the aeroplane performs under standard, i.e. ISA conditions. To use the POH data pilots must determine what pressure altitude (PA) and density altitude (DA) the aeroplane will fly at. The ISA is simply a temperature model, i.e. it specifies how temperature changes in the atmosphere. The ISA is divided into temperature layers known as the troposphere, stratosphere, and thermosphere. The standard temperature is 15 C at sea level and decreases 1.98 C per thousand feet in the troposphere. By 36,100 feet the temperature has reached -56 C. In the Stratosphere temperature remains isothermal (constant temperature) at -56 C. In the thermosphere temperature begins to rise again, but no civilian aeroplanes fly that high so we will ignore the thermosphere. The chemical makeup of the atmosphere does not change with altitude. The temperature, chemistry of the atmosphere, and the force of gravity collectively determine the pressure and density of the air throughout the ISA. It is important to realize that temperature, pressure, and density are inextricably connected to each other by a law of physics called the gas law. The gas law states that pressure is proportional to density and temperature. You can find more details on this in your aerodynamics text.

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Aircraft performance depends on air density but airplanes do not come with an instrument to measure it. They do however have a thermometer to measure temperature and an altimeter, which measures air pressure. The gas law relates air density to these two values. In the ISA the following values apply:

ISA Altitude

Temp C

0

Pressure Inches Hg

Density 3 slugs / ft

15.00

29.92

0.002377

1,000

13.02

28.86

0.002308

2,000

11.04

27.82

0.002241

3,000

9.06

26.82

0.002175

4,000

7.08

25.84

0.002111

5,000

5.10

24.90

0.002048

6,000

3.12

23.98

0.001987

7,000

1.14

23.09

0.001927

8,000

-0.84

22.23

0.001869

9,000

-2.82

21.39

0.001811

10,000

-4.80

20.58

0.001756

11,000

-6.78

19.79

0.001701

12,000

-8.76

19.03

0.001648

13,000

-10.74

18.30

0.001596

14,000

-12.72

17.58

0.001545

15,000

-14.70

16.89

0.001496

Pressure Altitude The most convenient instrument available to pilots for measuring air pressure is the aircraft altimeter. Pilots do not have a barometer (an instrument for measuring air pressure) to measure pressure in units of inches of mercury. When a pilot sets the altimeter scale to 29.92 it reads an altitude, but in effect it is giving the air pressure from the table above. Once set to 29.92 altimeter reads an altitude called pressure altitude. If the pressure altitude is 4,000’ the air pressure is 25.84 as shown in the table above. Fill in the values for air pressure in the table below:

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Pressure Altitude

Air pressure Inches Hg

Sea level 3000’ 5,000’ 7,000 9,000

The only way to get a precise pressure altitude is to set a calibrated altimeter to 29.92 and read the value on the instrument. This is not convenient for flight planning however, so we need a method to estimate pressure altitude. Notice that in the ISA pressure drops about one inch of mercury for every thousand feet up to 10,000’. This is an approximation, but it is pretty close. Armed with this knowledge it is possible to calculate the pressure altitude without using an actual altimeter. This is convenient since it means we can flight plan without needing access to an altimeter. To calculate pressure altitude we need to know the current altimeter setting and the actual altitude of the altimeter setting source. First a very simple example: An airport at sea level (such as CYVR) reports an altimeter setting of 28.86. In this case the air pressure is 28.86 and the pressure altitude is 1000’ as we can see from the table above. How would we calculate this mathematically? Standard setting:

29.92

Altimeter setting:

28.86

Difference

+1.06

Correction equals 1.06 x 1000 = +1060.

Therefore pressure altitude =

altimeter source altitude + correction Sea level + 1060 = 1060

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Notice that the calculation gives a value of 1060’ when the correct value is 1000’. This small error is acceptable for flight planning purposes. You should keep in mind that the calculation of pressure altitude results in estimation. To get a precise pressure altitude you must use a calibrated altimeter. Below is a more complex pressure altitude calculation in which the altimeter source is not at sea level. Altimeter source altitude: 3456 feet Altimeter setting:

30.67

Standard setting: 29.92 Altimeter setting 30.67 Difference

-0.75

Correction = -0.75 x 1000 = -750

Pressure altitude = altimeter source altitude + correction Pressure altitude = 3456 – 750 = 2706

Rounding off, estimate pressure altitude as 2700 feet.

TIP: You may find it hard to remember whether to add or subtract the correction from the altimeter source altitude. Remember that when the altimeter setting is more than 29.92 it is like flying at a lower altitude, and vice versa.

Density Altitude Density altitude represents the altitude in the ISA with the equivalent air density. Once you know the pressure altitude (in effect the air pressure) and air temperature, density altitude can be calculated in accordance with the gas law, which states that air density is proportional to air pressure and inversely proportional to air temperature.

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Many Pilot Operating Handbooks are designed so that it is not necessary to calculate density altitude since the manufacturer provides performance charts based on pressure altitude and temperature. This is wise on their part because calculating density altitude accurately requires a complex formula. The C-172 and King Air manuals you will use in this course have charts based on pressure altitude and temperature. In effect the density altitude calculation is incorporated into the charts. For these airplanes it is not necessary to calculate density altitude. Our B95 charts are based on density altitude, and therefore you must calculate its value. Because temperature is usually close to standard a reasonable estimation of density altitude can be made by adjusting pressure altitude 120 feet for every degree the temperature varies from standard. For example if the temperature is 3 C colder than ISA then density altitude will be 3 x120 = 360 lower than the pressure altitude. If air temperature is 5 C above standard then density altitude will be 600 feet higher than the pressure altitude.

DA = PA + 120ΔT

[ΔT is deviation from standard temperature]

TIP: Warm air is less dense air and thus density altitude is greater when the air is warm.

TIP: The KLN90b GPS has a built in density altitude calculator. You can use it to get a more accurate density altitude. The KLN90b in the piston simulators can be used just as well as the ones in the airplanes.

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Sample Questions 2 1.

The altimeter source altitude is 1000, altimeter setting is 28.92, temperature at 1000 feet is 15 C. Calculate the pressure altitude (PA) and the density altitude (DA)

2.


3.


4.

altimeter source altitude is 1624, altimeter setting is 30.35, temperature at 1624 feet is 18 C. Calculate the pressure altitude (PA) and the density altitude (DA)

5.


Cold Temperature Corrections The altimeter in an airplane does not actually read altitude; it reads static air pressure and displays this as an altitude based on the following assumed pressure/altitude correspondence: Indicated

ISA

pressure

Measured

Altitude

Ps(Hg)

difference

Pressure

0

29.92

1.10

29.92

1,000

28.86

1.06

28.86

2,000

27.82

1.03

27.82

3,000

26.82

1.00

26.82

4,000

25.84

0.97

25.84

5,000

24.90

0.95

24.90

6,000

23.98

0.92

23.98

7,000

23.09

0.89

23.09

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8,000

22.23

0.86

22.23

9,000

21.39

0.84

21.39

10,000

20.58

0.81

20.58

11,000

19.79

0.79

19.79

12,000

19.03

0.76

19.03

13,000

18.30

0.74

18.30

14,000

17.58

0.71

17.58

15,000

16.89

0.69

16.89

16,000

16.22

0.67

16.22

17,000

15.57

0.65

15.57

18,000

14.95

0.63

14.95

19,000

14.34

0.61

14.34

20,000

13.76

0.59

13.76

This table is correct for an altimeter set with the Colesman scale on 29.92 The table shows that an altimeter “assumes” pressure will drop 1.10 inches of Mercury between sea level and 1000 feet and then drop 1.06 between 1000’ and 2000’ etc. Consequently an altimeter set to 29.92 will read 7000 feet when the air pressure is 23.09 regardless of how high the airplane really is. The Colesman scale on the altimeter simply “slips” the above scale to reset the zero point, as shown in the diagram below, which is for an altimeter set to 30.44

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Indicated

ISA

pressure

Measured

Altitude

Ps(Hg)

difference

Pressure

0

29.92

1.10

30.44

1,000

28.86

1.06

29.38

2,000

27.82

1.03

28.34

3,000

26.82

1.00

27.34

4,000

25.84

0.97

26.36

5,000

24.90

0.95

25.42

6,000

23.98

0.92

24.50

7,000

23.09

0.89

23.61

8,000

22.23

0.86

22.75

9,000

21.39

0.84

21.91

10,000

20.58

0.81

21.10

11,000

19.79

0.79

20.31

12,000

19.03

0.76

19.55

13,000

18.30

0.74

18.82

14,000

17.58

0.71

18.10

15,000

16.89

0.69

17.41

16,000

16.22

0.67

16.74

17,000

15.57

0.65

16.09

18,000

14.95

0.63

15.47

19,000

14.34

0.61

14.86

20,000

13.76

0.59

14.28

This table is correct for an altimeter with the Colesman scale set to 30.44. When the actual air pressure is 30.44 the altimeter reads zero.

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IMPORTANT: altimeter settings are determined with an instrument located at the airport. Taking the above table as an example, if a particular airport is at 3000 asl an altimeter adjusted to read 3000 at that airport will “report” an altimeter setting of 30.44. The pressure difference between 3000 and sea level shown in the above table (30.44 – 27.37) is only hypothetical. The actual sea level pressure may not be 30.44 on that day, but the altimeter will read 0 feet if the actual air pressure is 30.44. Since this is only a hypothetical possibility it is not important. The thing to realize is that an altimeter setting permits the altimeter to read the correct altitude at the airport (3000 in the example), because that is where the altimeter setting instrument is located. Any temperature correction that an over flying airplane makes need only be applied to the atmosphere between ground level and the true altitude of the airplane. In the table above you can see that when the air pressure is 18.82 the altimeter reads 13,000 feet. This will happen regardless of the true altitude. If the air pressure between ground level and 13,000 drops exactly as shown in the table the altitude will be correct. More likely the pressure drop will vary from that shown and thus the true altitude will not correspond to the indicated altitude. If the air pressure declines with altitude more rapidly than the above table the true altitude will be lower than the indicated altitude. This is very dangerous for any pilot flying in instrument conditions and using the altimeter to avoid mountain tops. Pressure decreases more rapidly in cold dense air. Thus we must correct for temperature error any time the temperature is cold. RAC 9.17 specifies our legal obligation to calculate a temperature correction. A correction is required any time temperatures are significantly below standard. Normal practice among pilots is to make a correction anytime ground temperature is 0°C or colder. Three methods of making the correction will be presented in this course. In order of preference in use they are: 1.

Equation from RAC 9.17

2.

Table in CAP GEN

3.

CR

RAC 9.17 recommends allowing 4% height increase for every 10°C below standard temperature. This rule of thumb should only be used down to temperatures of -15°C. Memorize the rule of thumb and be able to use it; the corresponding formula is: Temperature Correction = .04 x (ISA deviation) / 10 x (Height AGL) [RAC 9.17]

The above formula gives the required correction, which should then be added to the desired altitude to get the indicated altitude you will fly in order to be safe. Remember to keep ATC informed of what altitude you are flying. This is particularly important if you will deviate from any specified altitude such as a missed approach altitude or an altitude on a DME arc, etc. RAC 9.17 specifies that you should also report deviations from FAF crossing altitude and MDA, but as these are minimum altitudes that you Page 26


can choose to be above on any approach most pilots do not report these deviations. However, you must consider carefully whether any conflict with other traffic could result from your temperature correction and keep ATC informed as necessary. For temperature colder than -15°C use the table in the CAP GEN. This table can also be used for temperatures of 0°C and -10°C; however it is based on an airport at sea level and therefore gives conservative corrections for airports that are higher than sea level. If you use the equation above you get a more accurate correction for airports that are above sea level. To use the table in the CAP GEN follow the instructions provided with the table. Note that RAC 9.17 states that the table is not valid for heights more than 5000 ASL. Many mountain approaches however have procedure turn and intermediate segment altitudes higher than 5000 AGL. It is common practice among pilots to use the table by summing values, for example adding 5000 and 3000 to get 8000. When doing this always round up each value obtained in order ensure safety.

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Performance Charts You must master the use of all the performance graphs, charts, and tables in the C-172P POH, Beechcraft Travelair Pilot Information Manual, and your Alsim (King Air) manual. Supplements to the C-172P POH are found in Appendix 14 of your Program Manual. A complete explanation of how to use each chart, table, and graph cannot be provided here, but most are self explanatory. Assignments are provided for you to practice using these planning aids and to confirm that you are using them accurately. The aviation Intranet provides links to many electronic aids that ease your flight planning chores, making it possible to plan a flight in a much shorter time. You will be using these aids daily as you prepare for flights but it is CRITICAL that you can perform the calculations without them should the need arise. Consequently the assignments in this course – and the quizzes and exams – are to be completed without these online aids, unless the instructions indicate otherwise. Normal aviation industry practice is for flight departments to establish a cruise power setting and use it for all but “special” flight situations. A special situation is one in which either an unusually long range is needed, or an unusually high speed, or some other situation requires a non-standard power setting. For example you might be asked to ferry an airplane over a distance that exceeds its normal range, but that can be achieved if slower than normal speeds are used. Alternatively, you might be asked to brake-in a new engine by operating it at 75% power for a certain number of hours. In such cases you must flight plan for a power setting different from that normally used.

Interpolation and Accurate Drawing Skill To use the various charts in your aircraft POHs you must learn two skills: 1.

2.

Accurately drawing lines on graphical performance charts a.

BE95

b.

King Air Manual

c.

Other Transport category aircraft

Accurately interpolate tabular data a.

C-172 manual

b.

King Air cruise tables

c.

CAP GEN temperature Correction charts

Both these skills are vital. You will be given assignments to practice these skills, but if these are not enough you must practice until you perfect the skill. Practice these skills using the computer simulations provided for that purpose.

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Electronic Charts for the C-172P The paper charts described above are all that you need to plan for any flight. On all your exams you will ONLY be permitted to use these paper charts, so be sure to master them. In all your assignments in Avia 160 use the paper charts. On our Intranet website several electronic aids have been provided. These electronic planning aids are much quicker and easier to use than the paper products. They are similar to the professional flight training aids used by modern airlines. You will use these electronic aids for your day-to-day flight operations in the aviation program. For the C-172P you will find: C-172 Electronic Takeoff Chart Electronic Navlog (ENL) –includes weight and balance

The Normal Takeoff distance graph is an electronic version of the two graphs in the C-172 Flight Planning Supplement. It gives Normal Takeoff Distance, and Accelerate Stop Distance. It is much quicker and easier to use, and always gives the correct answer. Use it prior to all flights to get your normal takeoff distance. Use the tables on pages 5-12 and 5-13 when short field operation is called for. The ENL has a built in weight and balance sheet, a cruise performance calculator, and a Navlog calculator. The weight and balance calculator eliminates the need to use the charts in section 6 of the POH. The navlog automatically determines TAS, CAS, IAS, rpm, eliminating the need to use any charts in section 5 of the POH. It also calculates drift, groundspeed, ETE and fuel required for the flight i.e. it performs the functions of a flight computer. Navlogs are covered later in this course. TIP: Remember that even though you will be using the electronic navlog for your day-to-day flying, which makes things very quick, easy, and accurate, you must be able to do all the calculations long-hand when needed. On your exams you will have to calculate without the electronic aid. When doing assignments you should do all the calculations by hand and then use the electronic navlog to see if you made a mistake.

Electronic Charts for the Travelair The aviation Intranet contains several electronic aids for B95 flight planning. They work essentially the same as the ones for the C-172. The BE95 Electronic Takeoff Chart also calculates accelerate go and accelerate stop distance, as well as single engine climb performance. The ENL contains a weight and balance calculator for quick, easy and accurate weight and balance calculations.

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Performance Rules of Thumb In the section above you learned to precisely use the charts that come with your airplane. However, the charts do not cover all situations. Most manuals do not provide charts for soft or rough fields and most light aircraft charts do not allow for a sloped runway for instance. Below are some rules of thumb that Transport Canada put together a number of years ago. A change in weight of 10% changes takeoff distance by 20% (ratio 1:2) Most “good” grass runways require 25% more distance than a paved runway Long grass (more than 4 inches) requires 30% more runway Soft surface mud, snow, etc. requires 75% more runway add 10% for 1 degree of up slope add 20% for 2 degree of up slope Subtract 5% for 1 degree of down slope 90% - (headwind component / rotation speed)% = percent change in takeoff roll and distance to clear obstacle. (e.g. 12 knot headwind and Vr = 94 therefore 90% - 12/94 = 77% 110% + (tailwind component / rotation speed)% = percent change in takeoff roll and distance to clear obstacle. In Avia 100 you will learn to use the above rules of thumb to make reasonable go – no go decisions in tricky takeoff situations.

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Weight and Balance Shift As a licensed pilot you know how to calculate a weight and balance, but an important exercise you may not be familiar with is shifting a CG by a specified amount. For example, if you calculate the weight and balance for an airplane and discover that it weights 5000 pounds and the CG is at 47 inches aft of the datum, but the aft CG limit is 45 inches what do you do? In simple terms the answer is easy; you shift some freight forward. Let’s say you have 400 pounds to shift forward, how far do you need to move it? The above question is a Transport Canada favorite on the commercial pilot and ATPL exams. The solution is quite simple if you remember the meaning of the concept known as moment. A moment is: weight x arm. At present we know the moment of the airplane is: Mcurrent = 5000 x 47 = 23,500 The secret is to realize that the desired moment is: Mdesired = 5000 x 45 = 22,500 The difference in moment, which is 1000 could be created by an infinite number of possible weight shift. For example we could shift 1000 pounds forward 1 inch, or 500 pounds by 2 inches, etc. In this case we have been told to shift 400 pounds of freight, so it must be moved 1000/400 = 2.5 inches. An important point to notice is that it makes no difference what the current location of this freight is, only that we move it forward at least 2.5 inches. In summary: Step 1: Calculate the current moment and desired moment, subtract to get the desired moment shift. Step 2: Move the freight by an amount equal to moment-shift / weight-of-freight

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Here is a typical transport Canada exam question, choose the correct answer: An airplane weighs 9000 pounds. The CG is 73 inches aft of the datum, The aft CG limit is 71 inches aft of the datum. There is 600 pounds of freight at 104 inches aft of the datum. Shift this weight to at least: a) 85 b) 75 c)

65

d) 55

Your calculations should reveal that: Mcurrent = 9000 x 73 = 657000 Mdesired = 9000 x 71 = 639000 M-change = 18000 CG-shift = 18000 / 600 = 30

The answer is therefore: 104 – 30 = 74. Most people will therefore choose b, but that is WRONG. If you move the weight to arm 75 it is still one inch too far back. Since the next lowest option is 65 that is the correct choice on this multiple choice question.

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Chapter 2 This chapter introduces you to the fundamental concepts of navigation. Everything in this chapter is vital. If you don’t understand and retain it 100% there will be a problem, so review this material often.

Mass – Distance – Time, The Fundamental Concepts of Physics In Newtonian Physics there are three fundamental concepts upon which everything else is based: 1.

Mass

2.

Distance

3.

Time

All other concepts from simple ones live velocity and acceleration to complex concepts such as work, power, energy, etc. are all composites of these three concepts. Even concepts that may not at first appear to be composites of the above three actually are, for example temperature is really just a measure of the velocity of particles, which in turn is the composite of distance and time.

Definition of Velocity, and two useful deductions from the definition Velocity is the simplest of the composite concepts in physics: V = d/t [d = distance, t = time] Velocity is a vector quantity. In other words it has both magnitude and direction. The direction is imparted to the velocity by the orientation of the distance. Think about what this means and we will discuss it in class. From the above definition come two crucial deductions: d = Vt T = V/d

Velocity Expressed as Airspeed Velocity is THE fundamental concept in navigation. To be more precise Groundspeed and direction of flight are the fundamental concepts in navigation. Once we know our groundspeed (GS) and track-made-good over the ground (TMG) we know everything we need to know to predict the time it will take to complete a flight. Unfortunately there is a confusing array of speeds that we must learn to sort through:


1.

Groundspeed (GS) (which is TAS + wind)

2.

Indicated airspeed (IAS)

3.

Calibrated airspeed (CAS)

4.

Equivalent airspeed (EAS)

5.

True airspeed (TAS)

Accurate flight planning requires accurate knowledge of TAS and GS. You should already know that an airspeed indicator (ASI) does not show TAS. It is NOT desirable to have an ASI show TAS even if it could. What a pilot actually requires to fly safely is the Equivalent Airspeed (EAS.) An airplane always stalls at a certain EAS, and we always fly our approach at a certain EAS. Think of EAS as the pressure you would feel on your face if the airplane had an open cockpit. Unfortunately airspeed indicators do not show EAS either, so we must learn to convert indicated airspeed (IAS) to Calibrated Airspeed (CAS) and then to EAS and finally TAS. In summary – life for pilots would be much better if there was only EAS and TAS. Unfortunately we must learn to deal with the undesirable IAS and CAS

True Airspeed (TAS) True airspeed tells us how fast the airplane moves through the air. This value is normally forecast in the POH for the airplane. You can also determine TAS in flight by reading your IAS and applying correction for: Position error (aka, calibration error) Compression error Density error See diagram below for the hierarchy of airspeed errors.

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Equivalent Airspeed (EAS) The equivalent airspeed compares flight at altitude to flight at sea level. When we say that an airplane is cruising at 300 KEAS we are saying that it experiences the same dynamic pressure as an airplane flying at 300 knots at sea level on a standard day. TAS = EAS at sea level TAS > EAS at all altitudes above sea level. Mathematically:

TAS = EAS/√σ

[σ is the density ratio, i.e. density of air divided by sea level standard density]

Indicated and Calibrated Airspeed (IAS and CAS) In an ideal world the airspeed indicator would show EAS. Unfortunately airspeed indicators are not perfect. So we must learn how to convert indicated airspeed (IAS) into EAS. The good news is that there is usually not much difference between IAS and EAS. Most of the time it is reasonable to assume that the indicated speed is the same as equivalent speed. At very slow speeds (high angle of attack) there will be a significant error, and also at very high speeds and high altitudes, above 200 knots and 20,000 feet there will an error. Indicated airspeed is by definition the speed shown on the airspeed indicator. Like any instrument and airspeed indicator is imperfect and as such a calibration chart must be provided. The calibration chart is found in the POH. The calibration chart compensates for the imperfect measurement of Pitot tube and static port on the airplane. Once you apply the correction factor you will have calibrated airspeed (CAS.) Most of the calibration error is due to the position of the static vent on the fuselage, therefore calibration error is frequently called position error. Calibrated airspeed is pretty close to equivalent airspeed in most cases. In fact the difference between EAS and CAS is less than one knot for airplanes flying less than 200 knots and less than 20,000 feet. That covers both the C-172P and Travelair. So, for these airplanes you may feel free to say that EAS = CAS.

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For any airplane flying above 20,000 feet (which includes the King Air) it will be necessary to apply a compression correction factor. Compression refers to the fact that air entering a Pitot tube is compressed and thus its pressure rises; consequently airspeed indicators always over read. CAS is always more than EAS. So an airplane flying at 250 KCAS at 30,000 feet is experiencing less than 250 KEAS. Your CR flight computer automatically applies compression correction, if you use the “professional method” for converting CAS to TAS. The “simple method” DOES NOT allow for compression error.

ICE-T To convert from IAS to TAS it is necessary to apply the corrections in the proper order. Always convert IAS to CAS, then CAS to EAS, then EAS to TAS. To remember the sequence, use the pneumonic ICE-T. Remember that with the CR you go directly from CAS to TAS, but that is because the EAS compensation is built into the computer. We cover use of the CR later.

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Heading (True, and Magnetic) Heading is the direction that TAS acts. Heading is expressed as an angle from north. Heading can be expressed in magnetic, true, or grid, but always in units of degrees. The earth spins around an axis that passes through the north and south poles. Straight lines drawn between the poles are called meridians of longitude. These lines define true north. Meridians appear on your map and you will learn to orient your protractor to these lines of longitude when measuring the true track (TT.) In the northern domestic airspace pilots set their heading indicators to true. In that case the headings displayed on the heading indicator are true headings. In the southern domestic airspace, pilots set their heading indicators to magnetic. The magnetic North Pole is many miles from the real North Pole and thus there is a difference between magnetic headings and true headings. The difference is called variation, and you will find it marked on your maps. We will be covering map theory in detail later. When flying over the poles neither true nor magnetic heading reference is satisfactory. In such cases another reference system known as grid is used.

Compass Deviation Like any piece of equipment a compass is never calibrated perfectly. The error in the compass is called deviation. Each aircraft compass comes with a deviation card that shows the extent of the error. As a pilot you must consult the deviation card and take it into account when setting the heading indicator to correspond to the compass.

Wind and Drift Imagine stepping outside with a helium-filled balloon and letting it float away. If the air is perfectly calm it will float straight up, but on most days you will see it drift sideways. This horizontal motion results from the air mass moving relative to the ground. Movement of the air is wind. Imagine that your balloon rises a few hundred feet and then maintains that altitude. You follow it and discover that it more-or-less drifts in a straight line. This is important because it will be difficult to flight plan if air moves in random fashion. Fortunately it generally moves in a steady continuous fashion, at least over a distance of a few miles. The primary complication in navigation planning involves allowing for this movement of the air (wind) i.e. allowing for drift. Wind is described by specifying the direction the air is coming from and how fast. When we say the wind is north at 15 knots we are saying that it is coming from the north, i.e. moving south, 15 nautical miles every hour. If you release your balloon into this air mass it will be 15 NM south after one hour, 30 NM south after two hours, etc. Page 39


Most people find it pretty easy to visualize a balloon drifting in the wind. The main difficulty is in realizing that wind is a large scale phenomenon not a stream within the air but the whole air. Do NOT think of wind as something that happens in the air but as a property of the whole air mass you fly in. While it is obvious that a balloon drifts it is equally true, if less obvious, that an airplane does also. An airplane moves through the air, which a balloon does not, but the movement of the air (wind) adds to the net movement of the airplane never-the-less. An airplane’s net motion is the sum of true airspeed and wind. True airspeed is a vector quantity that expresses how quickly an airplane moves through the air, and in what direction. To explore the meaning of drift examine the simulation called Drift on the Intranet website.

Wind Triangle: GS = TAS + Wind The most fundamental concept of navigation is: Groundspeed = True Airspeed + Wind GS = TAS + wind All three of these entities are vectors. So, all we have to do is remember how to add two vectors.

When dead reckoning you start with a known true airspeed and a forecast wind plus a track you wish to fly. Your task is to determine the heading that is required to maintain that track and the resulting groundspeed (so that you can calculate time to destination.) We will now learn the simplest method of solving the above problem. No calculators or mathematics is required. We will simply draw a picture. But it must be an accurate picture so get out your navigation-ruler and protractor and follow along. For our first sample problem we wish to fly from airport A to airport B. The distance between them is 240 NM and the true track is 050°. The wind is from 270° at 20 knots. The airplane flies at a true airspeed of 100 knots. Get a blank piece of paper and complete the following steps: 1.

Draw a vertical line roughly in the center of the paper which we will use to represent a meridian of longitude (i.e. it represents true north.)

2.

Make a small “x” in the lower left quadrant of the sheet to represent airport A. We put it in the lower left quadrant because we are going to fly north-east so we want to allow room to draw the line to airport B.

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3.

Center your protractor on airport A and orient it to north using the line of longitude. Mark 050° and then draw a line from airport A in the direction 050°. At this point your paper should look like the one below:

The line represents the track to airport B. We call this the track-made-good (TMG.) We don’t need to mark on airport B.

4.

Next we will draw a vector representing the wind. Place your protractor on the TMG somewhere in the upper right quadrant. (When drawing TAS-Wind triangles always place the wind vector near the destination end of the TMG.) Orient your protractor using the meridian and then mark a dot at the center of your protractor and another mark at 270° (the wind direction.)

5.

Take your ruler and laying it accurately from the wind dot to the 270° mark measure the distance 20 NM from the TMG in the direction of the wind. Your sheet should now look like the one below:

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The most accurate way to perform the next step is with a measuring instrument known by geometers as a compass. If you don’t have one it is possible to measure with a ruler, but it will likely be less accurate.

6.

Set your measuring compass (shown above) to exactly 100 NM (the TAS.) Put the tip of the compass at the beginning of the wind vector and draw an arc that intersects the TMG near airport A. Your diagram should now look like the one below:

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To work properly a TAS-Wind triangle must be drawn accurately. The TMG must be exactly 050°, the wind vector must be exactly 20NM long and the arc must be exactly 100NM long. If these conditions are met you will get an accurate wind triangle.

7.

Draw a line from the point where the arc cuts the TMG to the beginning of the wind vector. This line is exactly 100 NM long and it represents the true airspeed. The diagram is now complete, and it should look like the one below:

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The angle labeled (da) above is called the drift angle. The heading you must fly is represented by the TAS vector and you can measure it with your protractor. If you drew your diagram accurately true heading is 042°, and drift angle is 8°.

Measure the distance from the arc to the point where the wind vector intersects the TMG. This represents the distance flown in one hour – i.e. it is your groundspeed. The distance is 115 NM. We now have all the items we set out to determine:

True heading: 042° Ground speed 115 Knots

From this we can calculate the amount of time it takes to fly the 240Nm from airport A to airport B. It is NOT necessary to draw the full picture but if we did it would look like the one below:

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The purpose of the above diagram is to convince you that the net drift for the entire trip is proportional to drift for one hour. The flight from airport A to airport B takes 2:05 during which time the airplane drifts a total of 42 NM, which is represented by the line labeled “wind/whole trip” above. But, as you can see it is in proportional to the length of the trip, so da is the same in both triangles.

Definitions: Crosswind and Headwind TAS-Wind triangles are excellent for visualizing drift and determining groundspeed, but they are a bit unwieldy for practical flight planning. Thus we will introduce a mathematical model for determining drift and groundspeed. This model can be applied using an electronic calculator or a CR flight computer.

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The wind vector in the above diagram has been broken into two components, crosswind (XW) and tailwind (TW) that are perpendicular and parallel to TMG respectively. It is critical to remember that XW and TW are by definition relative to TMG not TAS, this is a common mistake. In slang pilots refer to tailwind as “wind on the tail” which implies that it is relative to the airplane, but this is NOT correct. Tailwind, headwind, and crosswind are all relative to the TMG, which is the course that is to be flown. To see an active version of this definition examine the simulation called Crosswind, tailwind, tailwind, drift angle definitions on the Intranet website.

Drift Angle Defined From the diagram above the relationship between drift-angle (da) crosswind (XW) and TAS is easy to see. Rather than memorize this you should be able to reproduce the defining diagram and extract the definition from it:

da = Sin-1(XW/TAS)

Groundspeed Defined The following diagram extends the one above to define groundspeed (GS)

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Note that TAS forms the hypotenuse of a right-triangle the base of which equals cos(da) x TAS. To this value the tailwind must be added to get groundspeed. The formula is:

GS = cos(da) x TAS + TW

It is very worthwhile to realize that as long as da is small there is not much difference between cos(da) x TAS and TAS. That is to say that cosine of a small angle is almost one. Thus when performing a quick estimate of groundspeed it is usually acceptable to add tailwind directly to TAS, but to get the precise value the cosine of drift angle must be applied. It is quite obvious that you can do this with an electronic calculator, but the CR also makes this allowance as we will see.

Calculation of Crosswind and Tailwind The above definitions show how we will use crosswind and tailwind to determine drift angle and groundspeed. What is missing is a method of determining crosswind and tailwind. To do that we must know the relative wind angle (rwa) as defined in this diagram:

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The relative wind angle is the absolute value of the angle between the wind direction and the track made good. In the example above the wind direction is 090° and the track made good is 050°. The relative wind angle is therefore 40°. Once we know the relative wind angle the crosswind and tailwind can be calculated by simple trigonometry as:

XW = sin(rwa) x Windspeed TW = cos(rwa) x Windspeed

The above formulae can be used to determine crosswind and tailwind with an electronic calculator. The CR flight computer performs the same calculation. In the example problem the wind speed is 20 knots and the relative wind angle is 40° therefore XW = sin(40) x 20 = 13 knots and TW = cos(40) x 20 = 15 knots. Using these values the drift angle and -1 groundspeed can be calculated, as described above. Drift angle is da = sin (13/100) = 7° and groundspeed is GS = cos(7) x 100 + 15 = 115 knots. Note that these values match the ones previously determined using the TAS-Wind Triangle.

Determining XW, TW, da, and GS with a CR Now that we know the mathematical formulae and can apply them with any electronic calculator (or spreadsheet) we will learn to more easily evaluate them using the wind side of the CR computer. The CR performs the calculations described above by taking advantage of the mathematical fact that when multiplying two numbers, say A x B = C then Log(A) + Log(B) = Log(C). The CR has a “wind disc” that allows you to visually determine XW and TW and a logarithmic outer scale that determines da and cos(da) x TAS. The explanation of how to use the CR wind side starts on page 30 of the Jeppesen CR manual.

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There are a few minor terminology differences between your CR manual and those used in this text. For example TMG is the same as what Jeppesen calls true course (TC.) Jeppesen draws a distinction between drift angle and crab-angle; we will use the term drift angle for both. Read pages 30 to 50 doing all the sample problems (the short section on addition and subtraction on page 32 can be skipped.) Once you have worked through the CR manual try the following sample problems:

Sample Problems: Given TAS, wind, and desired true course (TC) determine XW, TW, da, and GS:

TAS

True Wind

TC

100

270/20

050

100

270/20

330

100

270/20

130

100

270/20

220

155

330/30

300

155

330/30

180

350

080/15

100

350

080/15

010

80

120/25

090

80

120/25

210

460

320/140

270

460

320/140

170

XW

TW

Da

GS

Drift Estimation The accurate mathematical calculation of drift angle and groundspeed as explained above can be performed with an electronic calculator, a CR, a spreadsheet, or a computer program. However, when flying it is often necessary to change course without the opportunity to accurately recalculate the drift. Numerous IFR examples come to mind, for example when cleared to hold or to do an approach the pilot must establish a designated course (TMG) or when the assigned route is changed drift must be determined on the new route. In VFR flight you are already familiar with the need to plan a diversion should weather Page 49


or some other circumstance require you to change course. It is therefore extremely valuable to have a technique for estimating drift and groundspeed using only mental calculation (estimations.)

Estimate XW and TW The first step is to estimate crosswind and tailwind. You will need to know the magnetic wind. A good pilot always knows the wind direction and speed. Remember that the upper wind forecast is in true, so you must apply variation to get the magnetic wind. To estimate crosswind and headwind use your heading indicator (HI) or preferably and HSI, as though it is a CR. If your aircraft has an HSI set the desired course on the course-bar. Locate the magnetic wind direction on the heading indicator and determine how many degrees from the nose or tail of the course bar the wind is. The is the relative wind angle. Now you must memorize the following three proportions:

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In the above diagrams it is assumed that the pilot turned so that the desired course TC or TMG is “on the nose.” (This point is covered again below in the description of the simulation called Drift Estimation Challenge.) If the wind is 30° from the course or tail then 50% of it is crosswind and 90% tailwind or headwind. If the wind is 45° from the course or tail then 70% is crosswind and 70% is tailwind or headwind. And finally, if the wind is 60° from the course or tail then 90% is crosswind and 50% is headwind or tailwind. These percentages must be memorized. If there is a 30 knot wind and 50% is crosswind and 90% is headwind then crosswind is 15 knots and headwind is 27 knots. This example corresponds to a wind 30° from the course. Had the wind been 30° from the tail (reciprocal of course) the only difference would be that the tailwind would be 27 knots. Use this method to estimate the XW and TW for the following sample problems: Wind speed

Angle from nose or tail

20

30 from course

20

45 from course

20

60 from course

30

30 from tail

30

45 from tail

30

60 from tail

40

On the course

40

On the tail

40

“On the wingtip” i.e. 90° from course

XW

HW

Note that when the wind is “on the nose” it is all headwind with zero crosswind. When “on the tail” it is all tailwind with no crosswind. Similarly, if the wind is “on the wingtip” it is all crosswind with no headwind or tailwind. It is crucial to realize that in this case we are using the word nose to represent the course, not the heading. Once we know the headwind or tailwind we can estimate the groundspeed by subtracting or adding to the true airspeed. We learned previously that we should first multiply TAS by cos(da) but this typically makes only one or two knots difference, so for estimation purposes we can say that GS = TAS + TW or GS = TAS – HW. -

It seems like it will be much more difficult to estimate da since we need to evaluate the equation da = sin 1 (XW/TAS). While this sounds impossible to do in your head there is a simple mathematical trick that

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makes it quite simple. To explain we will review the definition of the angle unit called radians, and the formula for circumference of a circle.

It is important to recognize the close relationship between arc-length and the subtended angle (ra.) The angle ra can be precisely determined, in units of radians, by dividing arc-length by radius. To convert ra to units of degrees multiply by 180 and divide by pi. This may not be sounding like something that will be easy to do in your head but stick with me. Note that so far no approximations have been made, i.e. the above definitions are precisely valid. Next we will look at how we can substitute the definition of the radian as an approximation for estimating drift angle.

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Examine the diagram above that redefines XW as the wind component perpendicular to TMG. The point to notice is that the length of XW is very nearly the same as the length on an arc drawn from TAS to TMG. For small values of da it is reasonable to say that acr-length = XW. That being the case da in radians equals XW/TAS. Since we want da in units of degrees the formula becomes: Da = (XW x (180/Π)) / TAS

You may be thinking, “This still doesn’t seem too easy to do in my head.” There is one final step that transforms the above equation into a simple method; it is called the “Magic Number.” Since TAS is the same from day-to-day we can calculate the value TAS time pi divided by 180 and memorize this number, we call it the magic number. Once you know the magic number for your airplane drift is easy to estimate, it is simply:

da = XW / Magic Number

Magic Number Magic number was introduced in the previous section. Magic number is simply TAS x Π / 180 i.e. TAS / 57.3. It is important for you to memorize the magic number of the airplanes you fly. It is helpful to know

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your magic number for both cruise and hold/approach speeds so that you can estimate drift in cruise as well as holds and approaches. Since magic number is used for estimations there is no sense in calculating it overly accurately. For true airspeeds up to 180 KTAS determine magic number to the nearest ½, above 180 KTAS determine magic number to the nearest whole number. In the table below some magic numbers corresponding to the C-172, Travelair, and King Air have been left blank for you to fill in, other examples have been provided: Aircraft type

True airspeed

Magic Number

Piper cub

60 KTAS

Cessna 172

85 KTAS on approach

Cessna 172

105 KTAS in cruise

Piper Arrow

140 KTAS in cruise

Beech 95

105 KTAS on approach

Beech 95

150 KTAS in cruise

King Air

120 KTAS on approach

King Air

220 KTAS in cruise

4

Dash 8

300 KTAS in cruise

5

Lear Jet

440 KTAS in cruise

8

Airliner

480 KTAS in cruise

8

1 1.5

2.5

2.5

Estimation of Drift Based on Crosswind and Magic Number Once you commit your magic number to memory estimating drift angle is easy. Simply estimate crosswind, as previously covered, then drift angle equals crosswind divided by magic number. If you are flying a Piper cub with a 20 knot crosswind drift is 20°, what would it be in a King Air. The answer is 5° (20/4.) What would drift be in a jet airliner with a magic number of 8? The answer is 2.5° (20/8.)

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Complete the following drift estimations: Magic Number

Crosswind

Estimated drift angle (da)

(Knots) 1

25

1

30

2

20

2

30

2

45

3

25

4

30

6

30

8

30

Two-bit Math The magic number of a Beech 95 in cruise is 2.5, therefore drift equals XW/2.5. You may find it challenging to divide by 2.5 in your head but there is a simple trick that makes it easy. Answer the following question: You go to the 7-11 store to by a snack for $1.67. You reach into your pocket and discover you have a bunch of quarters. How many do you give the clerk? You probably had no trouble realizing you needed seven quarters to pay for your snack. You do this particular calculation so often that it seems trivial to you, but you have actually just divided 1.67/0.25. You would have freaked if I had asked you to divide 1.67 by 0.25 in your head, but it seemed simple when you think of it as money. You most likely just remember that each dollar is four quarters and you know that one additional quarter covers items up to 25 cents, two are required for items up to 50 cents, and three for items up to 75 cents. Anything over 75 cents would have required an eighth quarter. And so on. Now compare the above calculation to the one you wish to do in your head XW/2.5. This is the same as saying (XW/10)/0.25. Of course dividing any number by 10 is very simple since all you have to do is shift the decimal one place left, for example 20/10 is 2, 33/10 is 3.3, etc. Can you see how to use this trick to estimate drift angle? Simply take the XW and divide it by 10, then think of the result as the price of your snack and pay for it in quarters. For example if the crosswind is 15 knots, that becomes $1.50, which will take six quarters; therefore da = 6°. Try the following examples for yourself:

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Magic Number

Crosswind

Dollar amount

Estimated drift angle (da)

(Knots) 2.5

10

$1.00

2.5

15

$1.50

2.5

17

$1.70

2.5

20

2.5

22

2.5

24

2.5

28

2.5

32

2.5

36

4

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Drift Estimation Challenge From the Intranet website you should now examine the simulation called Drift Estimation Challenge. Follow the instructions below. Work your way through the first 7 sections and then do the challenge in section 8 until you can quickly score an at “ATPL” level of skill.

Drift Estimation Summary In this simulation you developed the skill to estimate wind drift reliably to within two or three degrees. In the next simulation you will learn a technique called bracketing that will pick up from this point and allow you to determine drift to the nearest degree. The drift estimation techniques from this simulation combined with the bracketing technique in the next simulation will give you all the skills you need to efficiently navigate IFR.

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Chapter 3 Introduction to Radio Navigation In this section you will learn how VOR, ADF, DME, and GPS work. These radio aids are used to guide pilots during the enroute phase of flight. When doing radio navigation a VOR, ADF, or GPS is used to define a track over the ground, i.e. the desired course (TC, or TMG.) Once a course is established drift theory, covered above, applies. Your task is to calculate the heading that will keep you on course and the groundspeed. It is important to realize that there is no difference at all in the objectives or methods of flight planning for IFR flight and VFR flight. It is important to have a basic understanding of how VOR, ADF, DME and GPS work. On the Intranet, under Sim-Multimedia there are several interactive tutorials covering: “How VOR Works” “How ADF Works” and “How DME Works.” You will find further clarification about how DME works by reviewing the simulations: “DME Jitter” and “Squitters, and Auto-standby.” AFTER you have reviewed all the simulations continue with the following. Read all of section 2 (Navigation Systems) in your Instrument Procedures Manual before continuing; this will explain all the navigation aids.

VOR, ILS, and DME Channel Pairing VOR receivers in airplanes are able to tune frequencies between 108.00 and 117.75. VOR stations with frequencies less than 112.0 are classified as terminal VORs and usually transmit on a lower power output. They normally are not part of the airway structure, they are used for approaches, approach transitions etc. VORs for use on airways have frequencies 112.0 to 117.75 and are powerful enough for use up to 100 NM (provided the airplane is high enough – because VOR requires line of sight.) On the KLN-90B GPS (in the B-95 and piston simulators) the map “super-nav 5 mode” can be set to VOR TLH. T stands for terminal VORs, which are the ones between 108.00 and 111.85. L stands for low altitude, which are all the VORs on Victor airways (see LO charts below.) H stands for high altitude, which are all the VORs used on high altitude airways (see HI charts below.) Between 108.00 and 111.75 those frequencies in which the first digit after the decimal is odd are ILS frequencies, while those where the first digit is even are VORs. From 112.0 to 117.75 all frequencies are VOR. To help you grasp what I mean look in your CAP and write down the frequencies for the following ILS transmitters:


Airport

Runway

ILS Ident

Frequency

Vancouver (CYVR)

26R

Vancouver (CYVR)

26L

IFZ

110.70

Vancouver (CYVR)

08R

IVR

109.50

Vancouver (CYVR)

08L

Victoria (CYYJ)

09

Victoria (CYYJ)

27

Abbotsford (CYXX)

07

Kelowna (CYLW)

16

Calgary (CYXC)

16

IEM

109.30

Calgary (CYXC)

28

Calgary (CYXC)

34

Lethbridge (CYQL)

05

IQL

To confirm your understanding of the frequency allocation system complete the following table: Frequency

VOR/ILS

Comment

107.85

n/a

Not a valid freq

109.15

ILS

109.20

VOR

111.30

ILS

109.45

VOR

Terminal – low power

112.15

VOR

Airway. Note above 112.0 so not an ILS

Terminal - low power

107.55 111.60

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115.30 117.95 109.85 112.15 114.70

There are a total combined 200 VOR and ILS frequencies, 40 ILS and 160 VOR. Because of the numbering protocol there are two VOR frequencies then two ILS frequencies, etc. up to 112.00. DME channels are numbered according to the military TACAN channel. There are more TACAN channels than VOR channels so the first DME channel used in civilian flying is 17 and TACANs 57 to 66 inclusive are not used either. DME channels alternate between X and Y, with X channels corresponding to VOR and ILS frequencies that end in decimal 00 while the Y channels correspond to VOR and ILS frequencies that end in decimal 05. Operationally there is no difference between an X channel and a Y channel – both transmit squitters on the same frequency but listen for interrogation on different frequencies therefore they will interfere with each other and must not be used in the same area. By convention, on LO charts and in the CAP the X is dropped from DME channels – only the Y is shown; for example YVR frequency 115.9 corresponds to DME channel 106X, but if you look on the map it just says DME Channel 106. But ILS 26R is frequency 111.95, which corresponds to DME channel 56Y, which is shown on the charts. There is no reason to memorize the DME channel assignments although you should understand how the frequencies are assigned. It is important to realize that a specific DME channel always goes with a specific VOR / ILS frequency and that is how your Nav radio is able to tune the DME without you needing to input the DME channel. The complete list is found in your CFS section D2.

VOR Reception Range To receive a VOR you must be high enough to have line of sight to it. This means that you must be above the horizon of the VOR, as shown in the diagram below. (See COM 3.5 in your AIM.) In the diagram that follows no shadow effect is considered, but in reality if the VOR signal is blocked by building, mountains, etc the reception range will be less than indicated by the formula.

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In the diagram it is clear that the aircraft’s altitude plus the radius of the earth forms the hypotenuse of a right triangle with r and distance from VOR (s) as the other sides. Using Pythagoras’ theorem and solving for s results in an equation. But actual reception range is not zero when at ground level. Thus the recommended formula is:

S = 1.23(alt).5 + 9

[alt in feet, s is in NM]

To receive a VOR you must be within the slant range (s) given by the equation above. A few sample values are: Altitude (agl)

S - VOR reception range (NM)

1,500

50

5,000

87

10,000

123

20,000

VOR range may be limited to 150 NM by power

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30,000

150+ NM – dependent of power

VOR, ADF, DME – Final Thoughts Perhaps the most important thing to be aware of about VORs is that VOR receivers determine what radial you are on but have NO WAY of knowing the relative bearing to the VOR. Consequently an RMI needle can only point accurately at a VOR if the heading indicator is accurate. If a heading indicator fails or is set incorrectly an RMI will NOT point at the VOR. An RMI needle rotates so that the tail of the needle corresponds to the radial the airplane is on; it always does this even if the heading indicator is wrong. This is distinctly different than ADF, discussed below. The simulations show that an RMI does not always point at the station. An ADF, if working properly, always points at the station. It does so even if the heading indicator is set incorrectly. As a result you will be flying on the WRONG course if your heading indicator is not accurate. On the other hand, you can always find your way to the station even with a failed heading indicator, which you cannot do with a VOR. The bottom line for pilots is to know and understand the differences between VOR and ADF in normal and heading-reference-failed modes of flight. Usually you use your ADF radio with non-directional beacons (NDBs) but it can also tune commercial AM radio stations. The ADF in Selkirk College airplanes can tune frequencies up to 1200 (higher bands are not useable.) A complete list of every radio station in Canada is on page D27 of your CFS. It is important to know that DME gives “slant-range” which is the actual distance from the airplane to the DME station. When you fly over the station a DME shows your altitude in nautical miles. Because of the slant range error groundspeeds calculated by a DME are not accurate when close to the station. The rule of thumb is to consider DME based groundspeed accurate only when distance from station in nautical miles is greater than altitude in thousands of feet. In other words, if you are at 4000 agl you need to be at least 4NM away to get an accurate groundspeed, but if you are at 40,000 feet you need to be 40NM away to get an accurate groundspeed. There is a simulation on Intranet that fully explains the indications of the various navigation displays you will encounter in this program. It examines the most common navigation indicators: Horizontal Situation Indicator (HSI) Standard VOR/ILS indicator Radio Magnetic Indicator (RMI) Fixed Card Indicator

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Each navigation display has its advantages. You will learn what each of these indicators looks like, what it displays and what it doesn’t. You will see for example that as wonderful as an HSI is it doesn’t work with ADF. You will also see that while an RMI is a great thing to have, it doesn’t work with ILS, etc. In the following description of the Nav Displays simulation marker beacons and ILS is mentioned for completeness. The theory of their operation is not part of this course. They will be covered in Avia 260.

GPS Navigation The basic operating principles of GPS are explained in a slide-show on our Intranet. The link can be found under Avia 100, Avia 160, and Avia 260. Read this entire slide show before continuing. Also read section 2.2 (Navigation systems) in the Instrument Procedures Manual. An important thing to realize is that a properly functioning GPS is a very accurate source of time. Pilots should always set their clock (watch) accurately for IFR flight, and your GPS is a legal source of accurate time. Take every opportunity to set your watch to the GPS in the airplane. (Note: the GPS in the simulators does not give accurate time.) When using VOR and ADF navigation accuracy is greatest close to the stations and less accurate farther away. Since GPS has no stations, the accuracy of GPS is the same regardless of where you are on the airway. Consequently GPS is more accurate than VOR or ADF for the enroute phase of flight. A major problem with GPS is that it can fail in certain ways without giving a warning to the pilot. RAIM is one method of improving warning that a failure has occurred. You will learn all the legal requirements for RAIM in Avia 120 and 220. This material is also covered in the readings assigned above. Distance values displayed on a GPS are horizontal, i.e. they are NOT slant range. Thus GPS gives accurate groundspeed even when close to “the station” (of course there really is no station, so this is obvious when you stop to think about it.) GPS gives distance off track rather than angle off track (VOR and ADF give angle off track.) There are pros and cons to this and you MUST learn to translate between both in your mind (more on that later.)

Bracketing It might not seem so at first but radio navigation can be done in accordance with the principles of DR or pilotage. When we defined these terms (review if you don’t remember the meanings) we said that DR is a more sophisticated form of navigation. Sadly, many pilots use pilotage anyway. Pilotage in terms of VOR or ADF navigation means “chasing the needles.” If you simply turn so as to push the needle back where it belongs (centered for a standard VOR indicator) you will stay on course, but you won’t determine the heading that keeps you on track and will thus tend to chase wildly back and forth when you get further from the station where the signal is less sensitive, and you will also have a very hard time avoiding wild swings in close proximity to the station where the needle can move very quickly due to increased sensitivity.

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The secret to avoiding needle chasing is to use a technique called Bracketing. This is covered in a simulation on the Intranet. Load the simulation called Bracketing – Tracking Technique In the previous simulation we learned to estimate wind drift based on the forecast wind. This is an invaluable technique and one you should use every day as an IFR pilot, but it can only get you roughly to the correct heading. Because winds aloft forecasts are not perfect you will need to adjust your heading enroute until you find the exact amount of drift. The technique used to find the exact amount of drift is called bracketing. In the simulation, just to make things more challenging, you are not given any wind information at all. You will see that even in this worst-case scenario you can use bracketing to figure out drift. Sadly many IFR pilots never master bracketing. They just wallow around the sky chasing needles back and forth. But, you won’t be one of those guys, will you? To master bracketing one thing that is needed is to fly precisely, so you can observe which way the airplane is drifting. In the simulation flying accurately is easy, in the real world it can be more challenging, although it is easy if you use the autopilot. When you fly the airplane you must try to fly headings as precisely as possible. If you can’t fly precisely you won’t be able to take full advantage of the procedures you are learning in this course. The other thing you must do when bracketing is remember what headings you have been flying. It should be pretty easy to remember them, but for the first few times through this simulation you might like to have a pad of paper and write down what you have done. Examining a written record of the headings you have flown will show whether you are “zeroing in” on the required heading, or wallowing. There are several secret codes built into this simulation. The main ones are: A = All H = HSI S = Standard VOR Indicator R = RMI F = Fixed Card Indicator

You may choose any navigation display you wish. However, I recommend that you start with HSI or ALL, as these are easier to see drift on.

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Establishing the Brackets

The following explanation will take you through a tutorial using the Bracketing simulation – please complete this section while using the simulation. Press the 2-key The secret code places the airplane on course 090, 12 miles west of the navaid. Set time compression to 1X unless you have a very slow computer. The flying instructor is flying. Read the “instructors mind” (the green box at the lower right.) Initially it says that the instructor is evaluating the heading 090. I.E. the instructor is waiting to see which way the airplane will drift.

Pretty soon the instructor sees that the needle is moving left (picture above.) Therefore he knows that 090 is too far right. Whatever heading is needed to stay on course it MUST be less than this heading.

Set time compression to zero (0X.) The “instructor’ mind” says 090 is the maximum heading he will ever fly. We call this the right hand bracket. Tip: as you observe the simulation you should press the 2-key to restart the sequence if it gets ahead of your reading. Tip: set time compression to zero to freeze the motion after each turn the instructor makes, so you can keep up with the process. The instructor has begun searching for a left limit (see comment in instructor’s mind.) Page 66


Here is what you will see. First the instructor turns 5 degrees left. He then waits to see what the needle does.

The IMPORTANT point is that it only matters WHICH WAY THE NEEDLE IS MOVING. So, the instructor flies heading 085 for a few seconds until he realizes that the CDI is still moving left. Next he tries heading 080, but the needle still moves left. So, he tries 075. All this time the instructor’s mind says, “searching for left limit.” The needle still moves very slightly left on heading 075, so the instructor tries heading 070. After a few seconds on heading 070 the instructor sees that the CDI has begun to move to the right. Watch the instructor complete the above-described procedure. If you miss part of process, or just want to see it happen again, either press the 2-key again, or click the “Start Over” button.

When the airplane is on heading 070 set time compression to zero. Read the instructor’s mind. It should now say: Minimum: 070 Evaluating: 080 Maximum: 090

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Comments: Left-limit established

If it doesn’t say the above you need to give the instructor a few more seconds to think, so increase time compression until he has time to think, then return time compression to zero. Reading the instructor’s mind you now see that he realizes that heading 070 is less than the heading that WILL be required to stay on course. His mind now states that the minimum heading will be 070. This is called the left hand bracket. NOTE: The instructor will remain on heading 070 until the CDI re-centers. NOTE: Whenever the airplane is off course always fly the corresponding bracket heading until back on course. To recap what has happened so far:

1.

The instructor realized the airplane was drifting right on heading 090, so he established 090 as the maximum heading (right hand bracket)

2.

After searching, the instructor discovered that 070 was the first heading to the left that caused the CDI to move to the right. So, he establishes 070 as the minimum heading (left hand bracket)

Based on the above, the instructor knows FOR SURE that the required heading to keep on course is between 070 and 090. Note that whenever the airplane gets off course the instructor will always go to (but NEVER beyond) the brackets – and will hold that heading until the airplane gets back on course. This commitment prevents wild chasing of the needle back and forth (a common mistake of new IFR pilots.) A really good pilot could tell from all that has happened so far that the correct heading is closer to 070 than 090 (see comments below about “beating” the computerized flying instructor.) However, the instructor is programmed to just split the bracket into half. In this case the brackets are 070 and 090 so the instructor decides that when he gets back on course he will try heading 080. In his mind he indicates 080 as the heading he is evaluating.

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The instructor remains on the left bracket (070) until back on course, and then tries heading 080 to see what happens:

Increase time compression Watch the instructor. He will fly heading 070 until he gets back on course. As soon as he is on course he will turn to the evaluation heading, 080.

Set time compression to zero once the instructor gets to heading 080. Now read the instructor’s mind. He still states that the brackets (minimum and maximum) are 070 and 090. The comment in his mind says that he is “trying evaluation heading.” i.e. he on course and flying heading 080. There are only three possible outcomes to this situation: 1.

The CDI does not move, indicating that 080 is the required heading.

2.

The CDI moves right, indicating there is less than 10-degrees of drift.

3.

The CDI moves left, indicating there is more than 10-degrees of drift.

Increase time compression from zero to see what happens. See how long it takes for you to realize the CDI is moving. After a few seconds the CDI moves a bit to the left. The instructor immediately turns to his left bracket heading of 070.

Set time compression to zero again, and read his mind. First, notice that as soon as the instructor realizes he is drifting off he turns to the bracket heading (but not beyond the bracket.) The instructor now realizes that 080 is not the correct heading to stay on course. In fact he now knows, for sure, that the CDI moves left on heading 080. So, he revises his maximum heading (right hand bracket) to 080 (From now on, even if he gets left of course at some point there is no need to fly a heading more than 080.) Read the instructors mind. The revised brackets are 070 and 080. So, he chooses the midpoint, 075, as the heading he will evaluate next, once he is back on course.

Increase time compression from zero and watch what happens. Page 69


After a few seconds on the left bracket (070) the CDI is again centered and the instructor turns to heading 075. His mind now says that he is evaluating heading 075 (i.e. guessing that there is 15-degrees of drift.) After one bracketing cycle the brackets have been reduced from a 20 degree span to 10 degrees. Can you now see how things keep going? Each time we evaluate a heading we reduce the span of the brackets in half. Soon they will span only 5 degrees, then 2½ (in theory.) Usually there is no practical need to get the brackets closer than 5 degrees to each other, although the instructor will keep going as far as he can. Now the instructor is flying heading 075. The same three possibilities exist: 1.

The CDI does not move, indicating that there is exactly 15-degrees of drift.

2.

The CDI moves right, indicating there is less than 15-degrees of drift.

3.

The CDI moves left, indicating there is more than 15-degrees of drift.

The brackets are at 070 and 080 respectively. So no matter what happens we will have narrowed down the drift to a five-degree range. If the CDI moves left the brackets will again be adjusted, becoming 070 & 075, if it moves right the brackets will become 075 & 080.

Increase time compression again to see what happens. The CDI remains centered for a long time. This tells the pilot that the drift MUST be very close to 15 degrees. Eventually the CDI starts to move right, slowly. This tells the instructor that there is less than 15 degrees of drift. A wise pilot would take the amount of time it took the CDI to move into account and revise the drift estimate to 14-degrees. See comments below about beating the computerized flying instructor. The computerized flying instructor is a stickler for purity so he revises the brackets to 075 and 080 and revises his drift estimate to 12.5 degrees (heading 077.5.) He now turns to his right bracket heading of 080 to get back on course and then tries heading 078. Once the airplane is within a mile of the station it is best to STOP bracketing and simply fly the evaluation heading until a mile beyond the station. Increase time compression and watch the instructor fly past the station.

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Theoretically the process continues exactly the same on the outbound leg. However, because you usually are slightly off course (just a few feet, we hope) at station passage it is wise to “open up” the brackets slightly once bracketing begins again on the outbound leg. The computerized flying instructor is programmed to open the brackets by +/- 3-dgrees. Outbound bracketing then continues exactly as before If you use bracketing faithfully you can establish drift within one or two degrees in short order. After that all you have to do is maintain heading accurately and you have things made.. Repeat secret code 2 as many times as you need to until you fully understand all the logic of bracketing. Make liberal use of setting time compression to zero, usually after each turn, so you can think about what the logic is. Bracketing is a foolproof system, if only you will use it.

Try secret coed 3, 4, and 5 for more practice. All the computerized flying instructor to demonstrate if you like. If you “blow” a particular attempt use the “Start Over” button to try again. You can click the “You have control” button at anytime to have the computerized flying instructor take over and demonstrate the procedure to you.

Use ALL the Navigation Displays If you followed the advice above you started by practicing bracketing with an HSI. However, you MUST master bracketing with: Standard VOR Indicator RMI Fixed Card Indicator

Press the S-key to switch to standard VOR indicator and practice bracketing. Press the R-key to switch to RMI and practice bracketing. Press the F-key to switch to Fixed Card Indicator and practice bracketing. I fully expect that you will spend several hours with this simulation before you are comfortable with bracketing, but it will be time very well spent. Page 71


Hide the Visual Aids By default the wind is hidden but all the other visual aids are visible. However, most airplanes don’t have moving map displays, so you need to be able to navigate with only “raw” navigation data. So, click the “Hide All” button at the bottom of the simulation to make the process more challenging.

Include Outbound By default the computer generates inbound bracketing exercises. However, if you check the box at the lower left of the simulation the computer will randomly include some outbound bracketing exercises for you. As you have seen, there is no real difference between bracketing inbound and outbound, but you should still do some outbound bracketing practice.

“Beating” the Computerized Flying Instructor Computers are dumb. People are smart. In secret code 2, above, when the instructor tries heading 075 and the CDI doesn’t move for a long time any human would realize that the drift is close to 15, and would only revise the heading to 076. Similarly a human would move the left bracket NOT from 070 to 075 but only to about 073 (or so.) Review secret code 2 above until what I have said here makes sense. The point is that you don’t always have to divide each bracket exactly in half. Use common sense (something the computerized flying instructor never does.)

Break-out Logic A FUNDAMENTAL principle of bracketing is that you commit to NEVER fly outside the brackets. This prevents the wild chasing of the CDI or RMI needle that commonly plagues new IFR pilots. The idea of bracketing is that you always have two brackets in mind that you KNOW FOR SURE make the CDI move left and right (but only just.) But, if the wind changes, or your heading indicator precesses, the brackets won’t work anymore. IMMEDIATELY that you notice you are off course always turn to the relevant bracket heading. Within a few seconds the CDI should start to slowly come back to center. If it doesn’t what do you do? If you have a manual HI check the compass and reset it. If precession is not the culprit then there are only two possibilities: Page 72


1.

The navigation display is wrong

2.

The wind changed

If you have no reason to believe the wind changed then test the navigation radios. Check the Morse code identifier to make sure the station has not gone off the air. If the radio has a test button press it. (For example the ADF radio can be switched from ADF to ANT then back to ADF. See if that changes the indication. For a CDI turn the OBS a few degrees, then reset the OBS.) ADF is particularly prone to giving false indications so if you have no reason to believe the wind has changed just keep flying your heading for a minute and see what happens. Usually the false indication will go away and you will see that you were on course the whole time. VOR and ILS are much less likely to give false indications, although it is amazing how many ILS approaches have bows in them caused by electronic interference on the ground. Once you determine that the off course indication is real, if your bracket heading does not center the CDI you must CHANGE the bracket. In computer programming this is called breakout logic. The computerized flying instructor has breakout logic. If he flies the bracket heading for 30 seconds and does not get at least 0.25 degrees closer to course he moves the bracket out by three degrees. The question is, when you move the bracket should you change the evaluation heading? That depends on what you think caused the problem. If it was a wind shift then you should change the evaluation heading in the same direction you opened the bracket, but half as much. If you think the problem was a temporary navigation signal deflection then don’t change the evaluation heading, also stand ready to close the bracket back in to where it was before.

Bracketing Summary Bracketing is a fundamental tracking procedure. In this simulation the bracket always starts from the zero point, with a totally unknown wind. In the real world you should always know roughly what the wind is. Therefore you start with your best estimate of the heading to stay on course, using the technique of drift estimation covered earlier. Then you set your initial brackets at +/- 10-degrees from there. With this head start you should have a near perfect heading bracketed out within a couple of minutes. If you start with a +/- 10-degree bracket it should only take a minute until you can tell whether you need to adjust your evaluation heading left or right. When you do, move the bracket in, but NOT all the way to your original evaluation heading. Pretty soon you will have adjusted your heading and brackets so that you have two brackets about +/-5 degrees from your best estimated heading. You then react to even small CDI deflections by turning to the appropriate bracket immediately. Using your judgment you revise your estimated heading, tweaking it one degree at a time. Note: you can only tweak the evaluation heading one degree at a time if you can fly your heading accurately enough to make such judgments.

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Because bracketing is so powerful you can easily see that when combined with the drift estimation technique covered earlier you can perform very accurate DR radio navigation even in the absence of completely precise wind forecasts.

Flying a DME ARC So far we have been concentrating on flying in a perfectly straight line. Now we will learn to fly a perfectly circular path. DME arcs are used on many IFR approaches and terminal arrival procedures. They allow airplanes to get lined up for approaches without the high workload (for controllers) of radar vectors. DME arcs are normally flown using an RMI. Therefore the simulation includes an RMI. The navigation display also includes an HSI, a standard VOR indicator and an RMI. If an airplane has an HSI but no RMI you can still do an arc by manually turning the HSI to keep it centered, so that it acts like an RMI. If you have neither RMI nor HSI it is not good practice to fly DME arcs. I have not provided the option for doing arcs without an RMI in this simulation. DME arcs can be assigned at any distance from a DME station from 7.0NM up. Smaller arcs are never used. To fly an arc you must first fly a path that crosses the arc. The simplest way to do this is to fly directly toward the VOR until you reach the desired distance to arc. Another common way is to be vectored until you intercept the arc. Once you intercept the arc turn so that the RMI needle points at the wingtip. If you are arcing right, that means the RMI points at the right wingtip. A left arc means the RMI points at the left wingtip. The easiest way to explain arcing is through an example. Please load the simulation and follow along with the example below.

Load the simulation called “Flying a DME ARC.” This simulation is for practicing DME arcs. You can also fly arcs using the Alsim simulation, but it is best to master this simulation first.

Press the 1-key This secret code brings up a clearance that reads: “Pilot 200, you are cleared for a practice DME arc. Intercept the 8 DME arc from the 120 radial and arc counter-clockwise to intercept the course 180. Your lead radial will be 014.” Page 74


The picture below shows the computerized flying instructor about half way through complying with this clearance.

Let’s start by breaking down the clearance to make sure we understand it. 8 DME arc means that the airplane must fly a circular orbit around the VORTAC at a distance of 8.0 Nm. (Indicated on DME radio.) From the 120 radial means that the arc starts at the 120 radial Counter-clockwise is the direction or orbit. Intercept course 180 means that the objective is to wind up flying inbound on the 000 radial. Lead radial will be 014 means that when the airplane crosses the 014 radial it will be 2 NM from the assigned course. Think of lead radials like a wakeup call. When you get to the lead radial you are almost at your assigned course, so you generally stop arcing and turn to intercept the assigned course (at 45°.)

Watch the Flying Instructor demonstrate the arc. (Press the 1-key to restart if necessary.) Set time compression as required and watch the entire demonstration. Initially the airplane is flying outbound along the 120 radial, which is the designated start radial. (Later we will do an example where the airplane flies inbound on the 120 radial.) Page 75


The instructor’s mind can be read at the lower right. He states that he intends to lead the turn onto the arc. He plans to turn when the DME reads 7.2 (the value will be different if you chose a cruise speed other than 150 KIAS.)

The above diagram shows that the turn to intercept an arc should start at a distance equal to the radius of turn of the airplane. Assuming that the turn will be at rate one a simple mathematical formula for radius of turn can be derived:

R = Groundspeed / 200 In other words: r = .5% of Groundspeed

For example an airplane flying 156 Knots groundspeed would need to lead the turn by about .8 Nm. (1% = 1.6 Nm, so ½% is about .8 Nm.) Keep in mind that the airplane must be in the turn at the designated distance. Allowing about six seconds to get up to rate one turn, you should add an extra 0.1 to 0.2 to the calculated value. In this demonstration the wind is zero, so the groundspeed equals the TAS. At the calculated lead distance the instructor starts his turn. The pilot must turn so that the RMI is on the left wingtip. Simply look at the tip of the RMI needle and turn 90° from that. In the example the RMI points to 300 so the first heading must be 300 + 90 = 390 degrees – but that is 030. Watch the flying instructor. At 7.2 Nm he makes a left turn to heading 030. If the lead was correct the DME should read 8.0 Nm as he rolls out on that heading.

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The only instruments needed to arc are the RMI and DME. To understand an arc you must remember what your high school math teacher taught you; a line tangent to a circle is always at right angles to the radius. Consequently the RMI needle, which shows your radial, must always be at or near the wingtip when flying an arc. In this case we are flying a counter-clockwise arc so the RMI needle must point near the left wingtip. In zero wind all you need do, in theory, is keep the RMI needle on the wingtip and the DME will not change. The airplane would fly a perfect arc. Unfortunately it is not possible to do such a perfect arc. Therefore, we use a technique of making a series of short straight legs that approximate the arc. Watch the flying instructor fly the demonstration and note how it is done. The instructor turns so that the RMI needle is five degrees ahead of the left wingtip. He then maintains a constant heading until the RMI needle drops to five degrees behind the wingtip. He then turns 10 degrees left, bringing the RMI needle five degrees ahead of the wingtip again. This pattern repeats over and over. What do we do if we drift off the designated DME distance? The instructor constantly monitors the DME. If the airplane gets a bit wide (DME reads 8.1 or more) he turns so that the RMI needle is MORE than 5 degrees in front of the wingtip. As long as the RMI needle is kept in front of the wingtip the airplane will move in, closer to the VORTAC. If the DME is remains at more than 8.0 as the RMI needle approaches the wingtip the instructor will turn to keep the needle ahead of the wingtip. If the DME drops to 7.9, the instructor realizes that he is inside the designated arc. Correcting this is simple. Just like a rock on the end of a string moves out instantly if you let go of the string the instructor realizes that if he simply stops turning, (i.e. maintains whatever heading he is on) the airplane will move out on the arc. As this happens the RMI needle will move past the wingtip. Once the needle is below the wingtip DME will start to increase. Once the DME reaches 8.0 the instructor resumes the usual arc procedure by turning to bring RMI needle near the wingtip again. The HSI and OBS are not needed to fly the arc. Therefore, once the airplane is established on the arc the instructor will set the HSI to the assigned course (180 in this example) and set the OBS to the lead radial (014 in this example.) With the HSI set the pilot can visualize how the arc is going. The airplane will be slightly more than 90degrees from the final course when the lead radial is reached, and that is easy to see on the HSI. The #2 CDI will center as the airplane crosses the lead radial. (Prior to reaching the lead radial the CDI always deflects to the center of the arc.)

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As the airplane crosses the lead radial the instructor will STOP arcing and turn to make a 45-degree intercept of the assigned course. He simply holds the 45-degree intercept heading until on the course, then tracks inbound using the usual bracketing technique.

DME Groundspeed During an ARC As you watch the instructor fly the arc notice the DME groundspeed readout. Every time the RMI needle passes the wingtip the groundspeed reads zero. Remember we learned in chapter two that DME actually shows closing speed, not groundspeed. So when the DME reads a speed of zero the airplane is NOT moving in or out on the arc. I.E. we are flying a prefect arc. Whenever the RMI needle is ahead of the wingtip there is a small DME groundspeed. Common sense tells us that we are “cutting in” on the arc, and DME is telling you how quickly. Whenever the RMI needle is behind the wingtip there is a small DME groundspeed. In this case we are moving away from the DME station at the indicated rate. An important to rule to note is that if the groundspeed is decreasing the airplane is getting closer to the VORTAC. If the groundspeed is increasing the airplane is getting further away from the VORTAC. These statements are only true if the airplane is flying straight (i.e. not turning.)

Press the 1-key, again. Then press the “I Have Control” button. Now it is your turn to fly the arc. Practice the procedure until you can keep the DME within 0.1 of the assigned value. You will find it impossible to prevent 0.1 variations, but you should not permit 0.2 deviations from the assigned DME. Tip: remember to set the HSI to 180 and the OBS to 014 once you are established on the arc.

Press the 2-key The assigned practice arc is exactly the same as the previous one. The only difference is that this time the airplane is flying inbound to the arc along the 120 radial. Once again the instructor calculates that 0.8 Nm lead is needed, so he starts the turn at 8.8 Nm. As before the first turn is to heading 030. From this point on the demonstration is exactly the same as before.

Press the 2-key, again. Then press the “I Have Control” button. Now try the intercept from outside the arc on your own.

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Press the 3-key This time the same arc clearance is issued, BUT the difference is a 30-knot west wind. From the map you can see that the wind is going to blow the airplane wide on the arc. What adjustments to the previous procedure will be needed? First notice that the groundspeed as we fly along the 120 radial is almost 180 knots. So, we must lead the turn to the arc by 0.9 Nm this time (these values will be different if you chose a different cruise speed.) A wise pilot would realize that the first heading should not be 030, because of wind drift. But, the computerized flying instructor has not been blessed with common sense. Watch and see what happens when he turns to 030. As the airplane is blown wide on the arc the instructor sees the DME reach 8.1. At that point he turns to move the RMI needle 10 degrees ahead of the wingtip. He then monitors the DME. If the distance does not decrease he turns to move the RMI needle further in front of the wingtip. Eventually he discovers an amount that causes the DME do decrease. He then keeps turning to maintain the RMI needle ahead of the wingtip until the DME returns to 8.0

Watch the DME groundspeed. In the previous example, when the wind was zero, we saw that the closing speed was zero when the RMI was exactly on the wingtip. But, in this case the closing speed is zero when the RMI is slightly ahead of the wingtip. And, the “zero point” changes as the airplane proceeds around the arc, because the angle the wind makes to the arc keeps changing. A wise pilot would use this information to arc better. Rather than using the wingtip as the zero reference use the point where the groundspeed reads zero. Unfortunately the computerized flying instructor doesn’t know that, so every time he gets back on the arc he turns to place the RMI only 5-degrees in front of the wingtip, and that is not enough. So, he keeps being blown outside the arc. When it is your turn you will do better. Right? The good news is that even with his limited intelligence the instructor keeps the airplane within half a mile of the arc, and most of the time within ¼ mile. That is good, but not excellent. See if you can do better.

Press the 3-key, again. Then press the “I Have Control” button. Now it is your turn to try arcing with a wind blowing you outside the arc. Repeat this exercise until you can stay within 0.2 Nm of the arc (i.e. until you are better than the instructor.

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Hide the visual aids. Having the moving map to help you judge the arc makes it easier. Unfortunately most airplanes don’t have this feature. So, click the “Hide All” button at the bottom of the page and try repeating the arc with no map to help you.

Turn the visual aids on again. Then, press the 4-key Once again we have the exact same arc clearance, but now the wind is 30 knots from the east. Watch the instructor demonstrate this arc. This time the groundspeed along the 120 radial is only 130 knots, so the arc need only be lead by 0.6 Nm. The wind will keep blowing the airplane inside the arc. The instructor will therefore keep flying straight legs, allowing the RMI needle to drop further behind the wingtip to get back on the arc. Take note of the groundspeed on the DME (too bad the instructor doesn’t do that.) A wise pilot would realize that in this situation the RMI needle should be kept behind the wingtip. But, the instructor is a bit too dense for that. Every time he gets back on the arc he turns to put the RMI needle five degrees ahead of the wingtip (as you would in zero wind.) Predictably he is blown back inside the arc and has to correct again.

Press the 4-key, again. Then press the “I Have Control” button. Now it is your turn to try arcing with a wind blowing you into the arc. Learn from the instructor’s mistakes. You can do better than he. Try keeping the RMI needle further behind the wingtip than you did with zero wind. You should be able stay within 0.2 Nm of the arc.

Press the 5-key This time there is a new arc clearance. This arc goes clockwise. It is also at a different distance, 10.0 DME. Watch as the instructor flies the arc. The start radial is 270, so the first turn is to heading 270 + 90 = 360. There is a 20-knot wind from the southeast so the wind is blowing the airplane outside the arc. As usual the instructor doesn’t keep the RMI needle far enough ahead of the wingtip, so he keeps blowing outside the arc.

Press the 5-key, again. Then press the “I Have Control” button.

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Now it is your turn to try the clockwise arc. All the procedures you have learned so far still apply. Remember that with the wind blowing you out of the arc you need to keep the RMI needle slightly in front of the wingtip.

Click the “Do Another” button. At this point we have covered all the techniques of arcing. What you need now is lots of practice. Every time you click the “Do Another” button the computer generates a random arc clearance with a random wind. The arcs are at distances from 6 miles to 12 miles. The two checkboxes at the bottom of the simulation labeled “Inside Intercept” and “Outside Intercept” are both checked by default. Thus you will get both intercepts from inside and outside the arc. If you wish to limit your practice to only one of these situations adjust the checkboxes. Make sure you are practicing successfully with all the visual aids hidden before moving on. If you are able to arc successfully with this simulation you should be ready to try it in the real airplane.

Intercepting a Course (PDT) Every IFR fling involves establishing yourself on an airway and an approach. The process of intercepting a particular course is called a PDT (Pre-determined Intercept.) It is one of your most fundamental skills. You will be mastering two separate skills: 1.

Intercepts Inbound

2.

Intercepts Outbound

To intercept a course inbound we use a simple little saying, “Desired to the head, plus 30.” You will soon see what that means. You can only complete an inbound intercept if you are currently within 60 degrees of the course you wish to intercept. If you are off course more than that go directly to the station and perform a procedure turn to establish yourself on the assigned course. To intercept a course outbound we use another simple little saying, “Tail to desired, plus 30.” Outbound intercepts can be completed regardless of how many degrees you are currently off course.

Load the simulation called “Intercepting a Course – Procedure Turn” As usual choose your cruise speed before clicking the “begin” button to start the simulation.

Choose a Navigation Display Before we begin you must choose a navigation display. You can make your choice from:

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A = All H = HSI S = Standard VOR Indicator R = RMI F = Fixed Card Indicator

The procedure for conducting predetermined intercepts (PDT) and flying procedure turns is exactly the same regardless of what navigation display you have. However it is MUCH easier with an HSI and RMI than without. Indeed the very reason people spend so much money to have HSI in airplanes is to make intercepts easier to visualize. Therefore I recommend you start with the option “A” for all, or “H” for HSI. By default the simulation generates a random inbound intercept. Leave the checkbox at the bottom of the simulation set to “Within 60 PDTs” for now. At the right side of the screen the red box contains the clearance.

Press the 1-key The clearance reads: “Pilot 200, you are cleared to intercept the 180 degree radial inbound to the YPB VOR.” Alternatively, if you have chosen either the “R” for RMI or “F” for fixed card navigation displays the clearance reads: “Pilot 200, you are cleared to intercept the course 360 inbound to the CM beacon.” Note the difference in terminology. When dealing with VOR or VORTAC navaids the controller (red box) uses the terminology radial to refer to the course. But when dealing with NDBs the controller uses the term course.

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The clearance requests the pilot to intercept the 180 radial inbound, as depicted in the picture above. From the picture it is pretty easy to see that we need to fly eastward. But, in a real airplane there won’t be a map (in most cases) so we must learn to figure out which direction to fly by looking at the HSI, standard VOR, or RMI indicators. As you are reading this, the instructor is flying. He figures out that he needs to fly a heading of 070 to intercept the course. Once on heading 070 everything falls into place. The question is; how does he know that he should fly heading 070? We must define: 1.

Assigned Course

2.

Desired Course

3.

Present Bearing (head)

4.

Present Radial (tail)

5.

Head

6.

Tail

7.

Track Error

8.

“Within 60”

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For an inbound intercept the assigned course is always the direction TO the station. Therefore if the controller has assigned the intercept in terms of radial you must take the reciprocal to get the assigned course. For an outbound intercept the assigned course is always the direction FROM the station. There is no need to take a reciprocal when dealing with outbound courses. Desired course is a synonym for assigned course. The present bearing is the direction that, at present, would take you to the station. If you have an RMI the present bearing is the direction the RMI needle is pointing. If you have only a standard VOR indicator you must center the CDI with a TO flag to get the present bearing. The present radial is the direction that, at present, you are FROM the station. If you have an RMI it is found by reading the tail of the RMI needle. If you have only a standard VOR indicator it is the bearing you get when you center the CDI with a FROM flag. The arrowhead of the RMI is called the Head. The opposite end of the RMI needle is called the Tail. The difference between the assigned course and the present bearing is called the track error. (It is easy to visualize on an RMI/HSI combination instrument (see picture below), as the angle between the RMI needle and the Course bar.) If track error is less than 60-degrees we say we are within 60.

The PDT procedure we are about to learn only works if you are within 60 degrees. If track error is more than 60 you must fly directly to the station and do a procedure turn. Your first task is to set the HSI to the assigned course (if you have an HSI.) For a radial put the tail of the course bar on the assigned radial to set the inbound course. Page 84


Next, make sure you are within 60. Usually in a real world context you will know how far the airway you are trying to intercept is away from you, so this will be an obvious step. But, in the context of this simulation you must find your present bearing (head) and compare that to the desired course (arrow on HSI) confirming the difference is less than or equal to 60. Once you know you are within 60 you simply following the little rhyme “Desired to head plus 30.” This simply means that you locate your desired course on the HSI then move your eyes to the head of the RMI needle, then move your eyes a farther 30 degrees. That is the heading you need to turn to.

Press the 1-key again. Now that you know the procedure watch the computerized flying instructor execute it. Make use of the time compression, setting it to zero, when you need time to read the instructor’s mind, or observe where he is pointing. As the instructor does the PDT he points at the HSI (if available) or the RMI if there is no HSI, or the heading indicator if there is neither. It is much easier to follow his explanations if there is an HSI, so I recommend starting with that navigation display. Later you can have him demonstrate the procedure with other navigation displays.

Notice that the instructor sets the HSI to the assigned course right away. Next he locates the present bearing on the RMI and compares that to the course bar. Look at where his finger is pointing (between the course bar and RMI head.) Then he returns his finger to the desired course (head of course bar. See picture above.)

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Then he moves his finger to the head of the RMI needle. (Labeled in picture above.) Then he moves his finger another 30-degrees. In this example that is a heading of 070. (See picture above.) Finally he turns to the heading of 070 and flies that heading until he is on the assigned course. That is all there is to it. NOTE: When we say plus 30, we mean 30 beyond the desired course.

Press the 1-key, again. Then press the “I Have Control” button. Now repeat the PDT yourself. Make sure you go through the procedure methodically. After confirming you are within 60 say to yourself “desired, to head, plus 30.” When that makes sense to you move on.

Set Time Compression = 0, then press the 2-key The airplane is back at the exact same starting point, and the exact same clearance is given. Because you set time compression to zero the instructor is on hold. Repeat the rhyme to yourself and try it. The desired bearing is 360, the head is at 040, so once again the required heading is 070. It is important to realize that the heading you must turn to depends on where you are, but NOT on your start heading.

Set time compression to a value greater than zero. Watch the computerized flying instructor do the PDT. Because the airplane is moving the present bearing is more than 040 by the time the instructor gets around to checking it. Therefore the heading he decides to turn to is more than 070. The other thing that probably surprised you is that he decided to turn left, rather than right. Why does he do that?

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The picture above shows what the instructor does. The picture below shows what you might have expected him to do.

You can see that if he had turned right he would have intercepted the course much closer to the station. That could be a good thing in many cases. But, if the airplane is already close to the station it can create difficulties. I find that in real world IFR flying you never really need to worry about this sort of thing. Just turn the most direct way to the chosen heading. But, if you and your instructor are practicing PDTs and remaining within 10 miles or so of the station you will find it prudent to take care which way you turn. The rule programmed into the computerized flying instructor is that if the RMI needle is ahead of the wingtip he simply turns to the chosen heading. But, if the RMI needle is behind the wingtip he will never turn through the RMI needle. In the example given he is turning to heading 080 but the RMI needle points to about 050. So, if he turned right he would fly right through heading 050. Since he is programmed not to do that he turns the other way.

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Press the 3-key Once again the clearance is to intercept the same course. But, this time we are on the other side of the course. The procedure however is exactly the same. Watch the instructor do the PDT. Pay attention to his finger. Set time compression to zero when you need time to analyze what he is doing.

Press the 3-key, again. Then press the “I Have Control” button. Now repeat the PDT yourself.

Press the 4-key Once again we are assigned to intercept the same course. And we are at the same starting point as the previous secret code. But the airplane is flying northeast bound, so things are changing. As in secret code 2 the instructor will turn the long way around.

Press the 4-key, again. Then press the “I Have Control” button. Here is your chance to see what happens if you turn left rather than right. Do so at your own discretion.

Use the “Do Another” button Before moving on to do outbound PDTs you will need lots (and lots and lots) of practice doing inbound PDTs. Keep the checkbox at the bottom of the simulation set to “Within 60 PDTs” only, and do lots of PDTs. When you are feeling confident with the procedure:

Hide all the visual aids. It’s a lot harder with the map hidden. Click the “Hide All” button at the bottom of the simulation. I recommend mastering PDTs fully with HSI before using the other navigation displays. However, if you wish to do some PDTs with the RMI, standard VOR indicator or Fixed Card indicator you may do so now. If you do, allow the computerized flight instructor to demonstrate the differences in where you must look to get the required information. Note that the procedure is always the same. The difference is only in where you get the required information, and in how easy it is to visualize. TIP: When you first start doing PDTs you should set time compression = 0 BEFORE clicking the “Do Another” button. That way you have all the time you need to figure out what heading you want to turn to. However, once you are getting the PDTs correctly you need to be able to do them in real time. You can even challenge yourself by setting the time compression to more than real time. Page 88


Outbound PDTs Now we will learn to intercept a course outbound from the station. The good news is that this is even easier than inbound intercepts.

Turn the Visual Aids On. Reset navigation display to “All” or “HSI.” If you have the visual aids turned off click the button at the bottom of the simulation labeled “Show All.” I also recommend returning to the “A” for all or “H” for HSI navigation display.

Press the 5-key The clearance reads: “Pilot 200, you are cleared to intercept the 000 degree radial outbound from the YPB VOR.” The picture below shows the objective pictorially.

When intercepting the course outbound I will teach you to use an intercept of 30-degrees. NOTE: there is NO within 60 limit for outbound intercepts. To perform an outbound intercept we have a different rhyme. “Tail to Desired plus 30.”

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Notice that this is a different rhyme than for inbound intercepts. In this one we start at the tail of the RMI, then we move our eyes to the desired outbound course (set on the HSI) then move our eyes a further 30degrees to find the required heading. (If you wish to do a 45-degree intercept just move your eyes 45 past the desired instead.)

Press the 5-key again. Watch the flying instructor perform the PDT. First he sets the assigned course (000) on the HSI. Then he looks at the tail of the RMI. Then he looks at the HSI course. Then he looks a further 30 degrees. The required heading in this example is 330. You may be thinking to yourself that all these steps are not really needed. All you actually have to do is look at the HSI. If the CDI were deflected left you fly a heading 30 left of the desired course, if the CDI were deflected right you would fly a heading 30 right of the desired course. This is true. But, I recommend checking the RMI for two reasons. The first is that without doing this you don’t know if you are off track 11 degrees, or 111 degrees.

The second reason is that only the procedure described here will work with an RMI or Fixed Card indicator. The picture above shows the instructor demonstrating the same PDT but with an RMI indicator. To see this press the R-key then click the “Start Over” button. Now, you will see that you MUST do the procedure as described above. Page 90


Return to the HSI display by pressing the A-key or H-key, then:

Press the 6-key This time we are assigned the same course to intercept and we are at the same starting point. But, our start heading is different. Despite this the instructor comes up with the same intercept heading, 330. Set Time Compression = 0. Then Press the 6-key With the airplane frozen you now have all the time you need to go through the procedure. Keep saying to yourself “tail to desired plus 30.” When you are ready:

Click the “I have control” button, then set time compression to more than zero. Fly the PDT yourself.

Use the “Do Another” button. Change the checkbox at the bottom of the simulation to “Include Outbound.” If you wish to do only outbound PDTs turn off the “Within 60 PDTs” checkbox. Make sure the “Over 60 PDTs” checkbox is NOT selected. Initially set the time compression to zero before clicking the “Do Anther” button so you will have time to think the procedure through. Then set time compression to more than zero when you know what heading you want to turn to. Do several PDTs until you are getting comfortable with the procedure.

Hide the Visual Aids Practice outbound PDTs with no visual aids. If you desire, practice outbound PDTs with standard VOR indicator, RMI and Fixed Card indicator.

Random PDT practice Now it is time for you to practice all the skills you have learned in this chapter. At the bottom of the simulation there are three checkboxes labeled:

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1.

Include Outbound

2.

Within 60 PDTs

3.

Over 60 PDTs

Check all three of these check boxes then:

Click the “Do Another” button at the top of the simulation. If the instructor is flying click the “I have control” button. Every time you click the “Do Another” button the computer will generate a random PDT. Some will be over 60, some won’t. Some will be inbound and some outbound. Read the clearance carefully then try to comply. If you need a demonstration you can give the instructor control at any time.

Use Time Compression as needed Initially feel free to set time compression to zero to give yourself time to think what you should do. But, you must work your way up to doing the exercise in real time.

Hide the visual aids. Most airplanes don’t have a moving map. Using the map makes it far too easy to do PDTs. So, once you understand the procedure hide the visual aids and practice with only the navigation instruments.

Use all the navigation displays. Be sure to practice PDTs with all the navigation displays. If you decide not to use a particular display, such as the Fixed Card indicator you must be certain you won’t encounter one in your real world IFR flying. If you know for certain that the airplane you are doing your IFR rating in has an RMI you may consider skipping Fixed Card indicator – perhaps returning to learn how to use it later.

Tracking and Intercepting Summary You now know how to track accurately along any assigned course. You can estimate the drift and then use bracketing to zero in on the exact amount of drift. You also know how to fly a circular arc around a VORTAC using a DME and RMI. You know what a lead radial is and how to set up the HSI and OBS when flying an arc. Page 92


You know how to intercept any course, inbound or outbound, from a VOR or an NDB. When an inbound course is within 60 degrees you can go right to it. When the course is more than 60-degrees from your present bearing you know how to fly to the station and perform a procedure turn. With the above skills you have all the knowledge you need to master holds and approaches. In the next chapter we will learn to perform holds. Keep your bracketing skills at the ready. In chapter 6 we will learn to do approaches where you will be able to use al l the skills you have just learned, including arcs and procedure turns.

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Chapter 4 IFR Charts Read section Map 3.2 in your AIM. The charts you will use regularly in this course are: LO HI Terminal

These are explained in your AIM, section MAP 3.0.

LO Charts LO charts are used for enroute navigation within the low level airspace. They show the “low altitude” airways and air routes, which are for airplanes flying less than 18,000’. High level airways are shown on the HI charts discussed below. Airways are based on either VOR or ADF. Even if you are navigating with GPS or Loran-C the airways you fly on are based on the positions of VORs and NDBs. The LO charts give the magnetic tracks for these airways. The charts also show distances so no ruler or protractor is necessary when flight planning with LO charts. To fly IFR on an airway you need an IFR clearance, which is explained below. LO charts also show air routes, which are similar to airways but uncontrolled. You will learn the regulations governing these in Avia 130. If you have worked through the designated simulations you know how to tune and interpret VOR and ADF radios with either HSI or standard VOR indicators and fixed card or RMI. If not then review that material before proceeding. In Canada all airways are based on either VOR or ADF. The VOR airways are called “Victor airways.” All Victor airways have a number which is preceded by the letter V, for example V100, or V302. In an IFR clearance these would be referred to as Victor one zero zero and Victor three zero two. ADF airways are commonly called “Low frequency airways,” they are always designated with the letter A,B,G, or R. The standard phonetic terminology is used, for example airway B22 is referred to as “Bravo two two.” Review the legend on your LO1 chart and then do the assignment to confirm you know all the symbols on the charts.


HI Charts HI Charts are used for enroute navigation in the high altitude airspace, i.e. at and above 18,000 feet in the southern domestic airspace (all flight in high level airspace is IFR.) Most high altitude airways are based on VORs but some are based on NDBs, all are named with a letter “J” followed by a number, for example J585. In a clearance this is referred to as “Jet five eight five.” Examine the legend of your HI altitude chart and then do the assignment to confirm you understand it. Note that HI charts do not symbolically indicate which direction corresponds to even and odd cruise altitudes because these altitudes change according to the cruising altitude orders. You will learn about this in Avia 130 and Avia 260.

Overview of IFR System This course is NOT designed to teach you IFR procedures, but you will learn how to prepare an IFR nav-log and flight plan. To do that you need to understand the basics of how the “IFR system” operates.

Separation of IFR Aircraft IFR airplanes are allowed to fly in clouds, unlike VFR airplanes. When in cloud pilots cannot see other aircraft. In Avia 260 you will learn all about IFR separation; in this course you need to know that IFR procedures are for the purpose of keeping airplanes from colliding with one another. Separation must be lateral (side to side) or vertical. Airways are like highways and like highways they must sometimes cross each other. Indeed airways are generally laid out like spokes on a wheel radiating out from VORs and NDBs. On highways traffic lights and stop signs prevent collisions at intersection. In IFR flight the ATC system takes on that task Airplanes flying along airways in opposite direction cannot pass the way cars on a highway do. Cars pass each other at combined speeds of 200+ KPH missing head-on collisions by four or five feet (pretty terrifying when you stop to think about it. Imagine trying to do it blindfolded.) Airplanes are separated by having opposite direction airplanes at least 1000 feet apart vertically. Eastbound airplanes fly at “odd thousand” altitude (1000, 3000, 5000, etc.) while westbound flights are at “even thousand” altitudes. VFR airplanes are “separated” from IFR by 500 feet (you already know the cruise altitudes for VFR.) This system works well for airplanes in cruise but is problematic when many airplanes need to climb or descend. Obviously an airplane climbing to 9000 feet (eastbound flight) must climb through 2000, 4000, 6000, and 8000 creating a risk of colliding head-on with westbound traffic in each case. Air traffic controllers are charged with making sure no collision takes place (and your life depends on them doing it, every time.) Cruising altitude rules for separating opposite direction flights is not satisfactory in the vicinity of busy airports because large numbers departing and arriving airplanes are climbing and descending creating a night-mare scenario for the controller. Preferred IFR routes, STARs, and SIDs are the answer. These are not unlike one-way streets you find in big cities.

Preferred IFR Routes

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When planning an IFR flight one task you must obviously do is choose a route. It might seem obvious that you would simply look at the LO or HI chart (LO for airplanes that cruise below 18,000 and HI for airplanes that cruise at and above) and choose the airway(s) that most directly take you from your departure airport to the destination. Before doing that however you should look to see if there is a published “preferred route.” This is the aeronautical equivalent of one-way streets that you have probably driven on in large cities. ATC finds it easier to control the flow of climbing and descending traffic (departures and arrivals) when outbound airplanes take one route (or set of routes) and inbound airplanes another. Departing airplanes can be cleared to climb without fear of opposite direction traffic, and similarly arrivals can be permitted to descend. The controller only needs to ensure that faster and slower airplanes don’t “overrun” each other, which is still a substantial task for ATC, but at least one problem is eliminated. Preferred IFR routes are published starting on page C98 of your CFS. If a preferred route exists you should use it. While the CFS indicates that the system is not mandatory you will find it impossible to get a clearance that does not comply unless you indicate a safety concern (bad weather) or a special operational need (lack of pressurization, special ferry flight, etc.) The bottom line is to use preferred routes. When departing from a small airport there is often no listed preferred route but if you are headed for a major airport you should use common sense and pickup a preferred route; for example departing Castlegar for Vancouver intercept the preferred route for Calgary to Vancouver.

IFR Alternate Airport In Avia 130 you will learn all the regulations about IFR alternate airports. In all your flight planning in Avia 260 you will have to allow for an alternate airport. In this course you are also expected to designate an alternate on IFR flight plans. To clarify why, the following highly simplified explanation of IFR flight is provided to get you started. The full set of considerations will become clear during the Professional Pilot Program. IFR flight makes it possible for airplanes to fly in cloud from departure to destination, thus largely removing weather as an impediment to flight. A few problems arise when flying in cloud however: 1.

Airplanes cannot see each other in flight, so some method of separating them must exist

2.

Airplanes cannot see the ground, so some method of avoiding it must exist

3.

Airplanes cannot see the runway, so some method of descending and establishing visual contact with the runway is needed in order to land

The ATC system exists PRIMARILY to keep airplanes from colliding during flight. Some aspects of this task have been indicated above. Any other services that controllers provide are secondary to the primary function. In short the ATC system solves only problem 1 above. Pilots follow prescribed procedures and climb at specified climb gradients to avoid terrain during departure and when enroute they fly above minimum enroute altitudes (MEA.) MEAs are shown on LO charts. The key word in the previous sentence is procedure and we say that terrain avoidance in IFR flight

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is “procedural.” Note that it is NOT the responsibility of ATC to prevent terrain collision. Pilots are responsible for that through the correct application of IFR procedures. IFR approach procedures are published in the Canada Air Pilot (CAP) which you have purchased. These are for the purpose of making a safe descent (taking terrain into account) to a point where the pilot MUST see the runway in order to land on it. So problem 2 and 3 above are both solved procedurally. It is always possible that the weather will be so bad that the pilot does not see the runway at the end of an IFR approach procedure. In this case an alternate airport, where the weather is good, is needed. You will learn all the regulations for this elsewhere, but it should be obvious that the alternate airport must have good weather so that there is NO CHANCE of being unable to land there. You will learn to assess the FORECAST to determine that an airport is a “legal alternate.” The required weather is specified in the CAP GEN and in RAC 3.14. On all IFR nav-logs you will include time and fuel to get to an alternate airport.

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Chapter 5 The CR Computer You have already learned to use the wind side of the CR, now it is time to master the front-side. Work through your CR manual from page 1 to 29 (you should already have done the rest of the book.)

A Ratio Machine The outer two rings on the front-side of the CR are a “ratio-machine.” You will learn to do many useful ratios all of which have practical application in your flying. First a quick review of what a ratio is: ½ = 2/4 = 3/6 = 18/36, etc. These are simple examples of ratios and fractions, for our purposes, ratios should be thought of as fractions. One half equals two quarters, three sixths, and eighteen thirty-sixths, and an infinite number of other ratios. The CRUCIAL thing to realize is that you can set any ONE of these ratios on your CR and it will give you ALL the others. In the photo below you can see that all the ratios are given. Get out your CR and set one of the above ratios and see that you have them all.

Before we go further it is important to note how numbers are displayed on the CR. On a CR 10 can represent 1, 10,100, 1000, etc. Thus 10/20 in the photo above represents ½ as well as 10/20, 100/200 and so on. 18/36 also represents 180/360 and 1.8/3.6 and so on. It is your job to keep track of the decimal


points when using your CR. It is important to know that not only does ½ = 2/4 also equals 20/40 and 2000/4000, etc. From the photo above, or your own CR, you can see that ½ equals 17/34 and 17.5/35 and an infinite number of other ratios not previously listed. But in a given situation only a few of these ratios are of practical interest – even so it is important to understand that there are an infinite number of equivalent ratios The secret to making good use of a CR is in knowing which ratios are interesting. This depends on what question you are trying to answer. A common problem is time and distance, which we will deal with under the topic of speed ratios below. But there are many other ratios of importance in aviation. For example climb gradients, distance to a radio navaid, unit conversions, etc. Solving problems with a CR requires you to ask, what relationships are relevant? For example IFR departures require a minimum climb gradient of 200 feet per nautical mile (ft/NM.) To use a CR effectively you must realize that this is a ratio (200/1.) A good clue is the word “per”; when you know that something happens “per” something else it is probably a ratio that you can solve with a CR. For example if you are paid $14 per hour and want to know how much you earn in 40 hours the CR can tell you. The photo below shows that you earn $560 dollars in (per) 40 hours. How many dollars do you earn in 8 hours?

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Unit Conversions Most unit conversions are simple ratios. Examples include pounds/kilograms, liters/gallons, statutemiles/kilometers and nautical-miles/kilometers. If you establish ANY relevant ratio relating these values you can use it to determine ALL others, using your CR. For example you may have noticed on the speedometer of your car that 80kph equals 50 mph – set this ratio up on your CR and fill in the table below: 40kph

_______ mph

90kph

_______ mph

800kph

_______ mph

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100kph

_______ mph

120kph

_______ mph

To solve the above problem we started with the ratio 80/50 which we remembered from the speedometer of a car – but the CR has most of the common ratios marked on its face. Remember that any ratio will do, so Jeppesen simply marks the ratios wherever they fit without cluttering the face of the computer too much.

The photo above shows a ratio for km/sm. Once this ratio is set all others can be read. The KM and Statute markings are found on both the outer and inner ring so you can set the CR up either way.

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Ratios can also be found for: Liters to gallons (both imperial and US) Feet to meters Pounds to Kilograms

Remember that if you know a conversion ratio from memory you can save the need to locate one on the CR. For example if you know that 2.2 pounds equals one kilogram simply set that ratio on the CR to save the trouble of locating the marked ratio shown below:

Set the above ratio and confirm that 2.2/1 is an equivalent ratio.

How many pounds in five kilograms? How many pounds in 16 kilograms? The CR does not have a conversion from Nautical miles to feet. You will often need to know that 1.0NM = 6080 feet. If you forget you can figure it out with a CR through a two-step process. First determine how many KM = 1NM and then convert from meters to feet. Try it yourself to confirm you get the expected value. The same process can be used to discover there are _______ feet in a statute mile. Page 105


Celsius to Fahrenheit Temperature Conversion You may need to convert from Celsius to Fahrenheit – this is NOT a ratio. -40°C = -40°F but 1°C does not equal 1°F. The reason ratios don’t work is that 0°C does not equal 0°F. For all the other conversions we looked at so far the zero points match. That is a requirement for using ratios as a conversion method. The CR has a temperature conversion scale on the front face (see photo below.)

You can see that -40°C = -40°F but that 0°C = 32°F. 20°C = ____?

Mach Number You will use Mach number extensively in flight planning. It is a ratio. Mach = TAS / speed of sound, by definition (this is a ratio.) Assume the speed of sound is 600 knots and set the ratio 600/1 on your CR, as shown below.

With your CR set as above 1200 knots is what Mach number? The answer is 2.0 Page 106


A C-172 cruising at 105 knots has what Mach number? What is the Mach number of a King Air cruising at 240 knots? The above conversions from TAS to Mach number are simple but only accurate if the ratio 600/1 is correct. In fact this ratio is only approximately correct; the real speed of sound varies with air temperature. You will notice that once you set 600/1 on the CR a Mach index is visible that allows you to “fine tune” the ratio for the actual air temperature. You can see the index in the photo below.

Set the Mach index to -25°C (the ISA temperature at 20,000’.) What is the speed of sound? This amounts to 1 saying what TAS corresponds to Mach 1.0 . An airplane cruising at Mach 2.0 has a TAS of _____ knots. An airliner cruising at Mach 0.8 has a TAS of _____ knots. What would the TAS of the airliner be if the air 2 temperature was -56°C?

Speed Ratios – I.E. Groundspeed Checks We will now explore a series of time and distance ratios. It is CRUCIAL to realize that “speed” is simply a ratio of distance over time. Let’s start with what pilots commonly call a “ground speed check.” You have just flown 17NM in 11 minutes, what is your groundspeed? Setup your CR with the ratio 17/11, as shown below.

1

610 KTAS

2

490 KTAS

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To be cheeky you could say, “My speed is 17 miles per 11 minutes.” That is a pretty weird unit, but it is indeed your groundspeed. It is however traditional to specify speed in units of Knots. Knot is defined as NM

per hour, but in reality it is NM per 60 minutes. It is VITAL to realize that the symbol, even though it has 1:00 written on it, actually represents six (6) or 60 on the CR, as you can see in the photo below:

Thus we would say that our groundspeed is 93 knots, which means 93/60. How far do we go in 30 minutes, how far in 12 minutes? You can determine these and an infinite number of other ratios once17/11 has been set – it’s just that you don’t usually think to ask such questions. There are however other ratios that are important beyond the simple 93/60 ratio that is “our groundspeed.” For example how many miles do we go in one minute. The photo that shows the 17/11 ratio also shows the ratio 1.54/1. This is an important value to know, sometimes. The airplane is covering 1.54 NM every minute. If the total length of the trip is 170 NM, how long will it take to get there? Note that since we are responsible for the decimal points the same ratio 17/11 gives the answer. Common sense says that it will Page 108

Navigation for Professional Pilots 3

take 110 minutes to fly 170 NM. How long would it take to fly 88NM? How long would it take to fly 214NM? Make up your own distances and confirm that you can find the time for any distance you choose.

Miles per Minute Nautical Miles per minute is a value that you will use in many situations so you need to become familiar with it. In the previous example the airplane flew 1.54 NM/min. If your speed is 90 knots how many miles 4 per minute are you covering? To find out, set 90/60 and then look up x/1. What is x? To approach this problem from the other direction, if you are flying 1 nautical mile per minute what is your groundspeed? In this case set 1/1 and look up x/60. Note that the answer is 60 KTAS. At 60 knots how long does it take to fly 18NM? How long for 78NM? How long for 156NM? The answer to all these is trivial and you should not require your computer. 60 knots – i.e. 1.0 NM/min is an IMPRORTANT speed that we will use extensively so you must remember it. If you are flying 2 miles per minute your groundspeed is _____ Knots. If you are flying 3 miles per minute your groundspeed is _____ Knots. 150 knots is _____ miles per minute.

Time to a Station – ARC Speed The procedure for flying a DME arc was covered previously on page 74. Arcs are common in IFR arrival procedures, and the theory behind them applies in other situations that we will discuss shortly. Consider the diagram below:

3

57 minutes

4

1.5 NM/min

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The airplane in the diagram is flying around a circle. At the moment shown it has flown 17° of arc in 11 minutes. What is the arc-speed? Arc-speed has units of degrees per hour, which of course really means degrees per 60 minutes. Simply set your CR for the ratio 17/11 and lookup the answer. The result is exactly the same as the groundspeed example above in which the airplane flew 17NM in 11 minutes, but this time the arc-speed is 93 degrees/hour. How long will it take to fly 20 degrees? How long will it take to fly 60 degrees? Hopefully your reaction to the above is that it is trivially obvious (but you may be thinking it is unimportant – trust me it is VERY IMPORTANT.) Be sure to examine the above until you fully understand it. Here are a few sample problems for you to work through just to be sure: You fly 14 degrees in 7 minutes; your arc-speed is ______ degrees/hour. It will take _____ minutes to fly 60 degrees; it will take ______ minutes to fly 57.3 degrees. Page 110


You fly 37 degrees of arc in 3 minutes. Your arc-speed is _____ degrees/hour. It will take ______ minutes to fly 60 degrees; it will take ______ minutes to fly 57.3 degrees. It is now time to review some high school trigonometry. First recall what an equilateral triangle is:

An equilateral triangle is one that has all three sides the same length and all three angles equal. The three angles must all be 60 degrees (the sum of the three angles in every triangle is 180°) The three sides of an equilateral triangle are equal to each other. In the diagram above distances AB = AC = BC. Now examine the following diagram:

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The diagram above is the same as the previous one with an arc added. The center point of the arc is B. Look at the diagram and estimate the length of the arc compared to AC. Obviously the arc is longer, but how much - 1%, 10%, what do you think? The difference is less than 5%. It should be obvious that there is some angle, just a bit less than 60°, such that the length of the arc is the same as the length of the sides AB and BC. Obviously AC will have to be shortened, consequently the triangle will not be exactly equilateral any more, but it will be close. Consider the diagram below.

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In the diagram above the angle through which the arc sweeps is reduced to 57.3 degrees. This is the “special” angle for which the length of the arc is exactly equal to the radius. I.E. AB = AC’ = arc. AB and AC’ have been labeled r in the diagram to remind us that they are the radius of the arc. 57.3° is known as one radian. The sample problems above asked you to determine the time to fly 60 and 57.3 degrees of arc, we will now examine why. Returning to a previous example in which the airplane few 17° of arc in 11 minutes (setup your CR for the ratio 17/11.) The time to fly 57.3° of arc is 37 minutes. But, since the length of the arc equals the radius it obviously also takes 37 minutes to fly directly to the center of the arc (point B.) The time to fly 60° is 39 minutes. Most pilots use this as the answer because it is a lot easier to remember 60 rather than 57.3 (57.3 = 180/Π.) Time to the station is a common problem in aviation. You will even more commonly need to know distance to the station, but that is a two-step process which we will cover in just a moment. First let us consider the most common situation in which the above theoretical facts comes into actual practice.

In the above diagram the airplane is flying an eastbound track that passes north of a VOR. The pilot wishes to know how long it would take to get to the VOR if s/he turned southbound directly to it. To find out, without the need to actually do it, record the time from A to B and the angle X. To be effective AB must approximate flying an arc, so the station must be essentially abeam the airplane (as in the diagram.) The angle X is usually fairly small, typically less than 15° (but not too small or there will be “round off error.”) Angle X is arbitrary, so it doesn’t matter if it is 4°, 7°, 11°, 15°, etc. simply time whatever is convenient. Once you have a “time / x-degrees” ratio setup on your CR all you do is lookup time for 57.3°or 60°. Neither will be precisely accurate, but either will give an answer that is within 5% of the correct value. The above use of “arc-speed” to determine time to a station when flying abeam is one of the most common uses of arc-speed theory. As you can see, it is an approximation since the airplane actually flies a

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straight line forming a triangle with the station, but the previous analysis that showed an equilateral triangle is very similar to a one-radian arc. It is recommended that in these calculations you use 60° as the reference angle rather than 57.3 (i.e. think of the equilateral triangle analogy to help you remember how to do it.) Next we will consider a more precise use of arc-speed theory. Consider the modified approach plate 5 below :

To fly this arc you start at the point marked and maintain a constant 9 DME arc to intercept the 087 radial (which lines you up for landing on runway 09.) On the right side of the plate a Lead Radial (LR) is published, but its value has been erased on the above photo. The LR is always 2NM prior to intercept of the final approach course (087 radial in this case.) What should the LR be? See if you can figure it out based on arc-theory before reading the next paragraph. To answer the question we need to realize that 57.3° of arc will be 9NM, since it is a 9 DME arc. So set the ratio 9/57.3 on your CR and look up 2/a. The answer is 12.7°. Note that if you had used 9/60 as your ratio you would get 13.3°. Either way you will round off to 13° and predict the 074 radial as your answer.

5

The original is in the CAP3 under Brandon

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Imagine you are flying the above arc arrival and wish to slow down and start your pre-landing checklist 5NM prior to intercepting the final approach track, what radial should you start to slow down at? If you kept your CR set to 9/57.3 the answer is right in front of you. Look it up before reading the next paragraph. With your CR set to the ratio 9/57.3 lookup 5/a. The answer is 32°. So you will need to slow down at the 055 radial. The above uses of arc-speed are very typical of ones you will experience everyday as a commercial pilot. Learn them well and get comfortable with them. Imagine the above DME arc had been 14NM instead of 9. What would the lead radial have been?

Two IMPORTANT two-step CR Ratio Problems There are two very important two-step CR calculations that we will cover next. One is distance to a station, which extends the time to station calculation previously covered. The second is gradient to rate which is very important for IFR departure and arrival planning. Both demand full mastery of the ratio concepts covered so far, so be sure you fully understand the above before moving on.

Distance to Station Below the same diagram previously examined has been repeated.

It is much more likely that the pilot wishes to know the distance to the VOR rather than time to the VOR. Imagine the situation in which the flight plan route passes a certain number of miles north of the VOR. The pilot wishes to determine if s/he is on track (the airplane could be in IFR weather conditions, over water, or featureless terrain, so that this method is the only method of fixing position. If the airplane is equipped with DME the position check would be easy, the pilot would simply note the distance as s/he passed abeam the VOR, but this particular airplane does not have a DME so we will have to do it the “hard way.”



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First, it is important to note that we cannot solve this problem unless we already know the groundspeed of the airplane. We will assume that the pilot has been doing his/her job well and knows the groundspeed. Assume the following data and follow along with your CR. The airplane crossed the 355 radial at time 0:00 and crossed the 005 radial 7:00 minutes later. The groundspeed is known to be 144 knots. How far north of the VOR are we? This is going to be a two-step process. What is the first relevant ratio? Think it through on your own before reading the next paragraph. (Tip: what is the angle X?) The airplane has flown through an angle of 10° in 7 minutes. Setup the ratio 10/7 on the CR. Now determine how long it would take to fly 60°. The answer is 42 minutes (10/7 = 60/42.) So time to the station is 42 minutes. In the second step we will determine distance to the station. We know it would take 42 minutes to get there, but how far is it? We know that groundspeed is 144 knots. What ratio do we need to setup? Reason it out before reading the next paragraph. We setup the ratio 144/60 which represents distance in 60 minutes. The relevant ratios are 144/60 = a/42, where a represents the answer. The answer is 101 nautical miles. In summary: When flying abeam a station, calculate distance to the station by: 1.

Determining how long it would take to fly a 60° arc (or one side of an equilateral triangle.)

2.

Second, determine how much distance is represented by step 1

NOTE: You must already know your groundspeed.

Gradient to Rate Conversion Many IFR departure plates have notes that specify a required climb gradient, in units of ft/NM. Even when 6 none is specified all departures must achieve a climb gradient of 200 ft/NM . Pilots routinely plan arrivals at a descent gradient of 320 ft/NM (which corresponds to 3°.) Often other descent gradients are required, especially for non-precision approaches in mountainous environments. We will thoroughly examine gradients in what follows. Keep in mind that climb gradient and descent gradient theory is fully interchangeable. Anything you learn about planning descent rates can be applied to climb rates, and vice versa.

6

This relates to the “procedural” terrain separation previously mentioned in the Overview of IFR Flight

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Unfortunately climb and descent gradients are not directly usable by pilots. Our aircraft are equipped with rate instruments, not gradient instruments. We have an airspeed indicator and often a DME or GPS all of which give our speed (a rate) and we have a vertical speed indicator (VSI) that gives our rate of climb and descent. Our challenge is to translate the published climb and descent gradients into useable verticalspeed/airspeed ratios (rates.) You will find it necessary to remember that 1.0NM = 6080 ft. We will start with a very simple problem, but one that applies to all IFR departures. As stated previously the minimum acceptable climb gradient is 200 ft/NM, as shown in the diagram below.

We can quite simply answer questions such as; what is the minimum safe altitude 5NM after takeoff? Can you setup the required ratio? Try to do so before reading the next paragraph. The ratios are 200/1 = a/5, where a is the answer. The answer is 1000 feet, i.e. you must be at least 1000’ agl 5NM after takeoff to meet the gradient. When you reach 2000’ agl the maximum distance you should be from the airport is ______ NM. The problem we most need to solve is; what vertical speed must we maintain to safely meet the gradient? This is almost trivially simple to answer if you remember that 60 knots is 1.0 NM/min (previously I said that you needed to remember that fact.) If you forget then set your CR to the ratio 1/1 to remind yourself that 1.0 NM/min means 60 miles per 60 minutes. Examine the above diagram and imagine the airplane climbing along the flight path at a groundspeed of 60 knots. After one minute it would be at the 1.0 NM point and its altitude would be 200 feet. After two minutes it would be at the 2.0NM point and its altitude would be 400 feet, etc. It must be clear to you that it requires a vertical speed of 200 fpm. To make rate conversions it is CRUCIAL to realize that an airplane with a groundspeed of 60 knots requires a climb rate equal to the gradient. In this case the relevant ratio is therefore 60/200. What climb rate do you need at 75 knots? Figure it out on your own before reading the next paragraph.

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Set the CR to the ratio 60/200 and lookup 75/a. The answer is 250 fpm. At 85 knots the minimum safe 7 vertical speed is _____ fpm. At 95 knots it is _____ fpm. At 105 knots it is _____ fpm . At 120 knots it is _____ fpm. Not all departures can be made safely at a gradient of 200 ft/NM. When a larger gradient is required the departure chart will specify the required value. The plate below is an example:

You can find the above plate in your CAP2 under Victoria International, Mill Bay SID. Depending on which transition ATC assigns, a climb gradient of 330 ft/NM or 220 ft/NM applies. Let’s work out the required vertical speed for each case – starting with 330 ft/NM. What ratio should you setup on your CR? Try to figure it out before reading the next paragraph. We must realize that at 60 knots the required vertical speed is 330 fpm. So set the ratio 60/330 and lookup your-speed/a. [Tip: it makes no difference whether you setup 330/60 or 60/330 as long as you keep track of whether groundspeed or vertical speed is on the top of the ratio.] If your groundspeed is 75 knots the required vertical speed is 415 fpm. At 85 knots it is ______ fpm. At 105 8 knots it is ______ fpm . Repeat the above calculations for a climb gradient of 220 ft/NM. Make sure that the above calculations are effortless for you. You must routinely check the minimum climb rate for IFR departures. Before we move on to the next important point it should be pointed out that you can approach the above problems from the opposite direction. If you know your groundspeed and vertical speed you can use the CR

7

350 fpm

8

580 fpm

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to determine your actual climb gradient. This is also helpful for flight planning purposes. We will use it quite often, so it is worth covering now. Imagine that you know your groundspeed is 115 knots and that your vertical speed is 800 fpm. What is your climb gradient? What ratio should you setup, and how do you get the answer? Figure it out before reading the next paragraph. The relevant ratio is 115/800 = 60/a. The secret is to realize that the ratio groundspeed/vertical speed, i.e. 115/800 establishes the gradient. To get the value in units of ft/NM remember that 60 knots is 1.0 NM/min, and look up the vertical speed at 60 knots. In this case the answer is 416 ft/NM. As long as this value exceeds the published climb gradient the pilot need not worry. This calculation can also easily be extended to answer questions of the form; what altitude will this airplane be at when 6.4 miles after takeoff? [Tip: this is step two of a two-step problem.] Try to figure out the answer before reading the next paragraph. We know the climb gradient is 416 ft/NM so setup the ratio 416/1 and lookup a/6.4. The answer is 2660 feet. A particular airplane climbs at 160 knots and 1000 fpm. What is the climb gradient, and what altitude will it be at 3.7NM after takeoff? The first ratio is 160/1000 = 60/a. This gives a climb gradient of 222 ft/NM. The second step is to use the climb gradient, so set the ratio 222/1 = a/3.7. The airplane will be at 830agl 3.7NM after takeoff. You can see that the above two-step calculation is quite useful for flight planning. Go over it until it makes complete sense to you. Next we examine a very important, but not significantly different, situation related to approach planning. Consider the following approach plate, which is quite typical.

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The approach plate above can be found in your CAP2 under Abbotsford NDB RWY 07. On this approach the airplane must cross the XX NDB at 1700 (or above) and then land on runway 07, which has a touch down zone elevation (TDZE) of 174. The XX beacon is 4.3NM from the runway. All this information is presented on the above plate; be sure you can locate it for yourself. The airplane must descend 1526 feet (1700 – 174.) The pilot will of course not land exactly at the runway threshold; normal touchdown is made about 0.2NM past the threshold, so the descent must be completed in 4.5NM. What is the descent gradient? Try to figure it out yourself before reading the next paragraph. The relevant ratio is 1526/4.5 = a/1. The answer is 340 ft/NM. What vertical speed is needed? Try to setup the required ratio on your own before reading the next paragraph. The relevant ratio is 60/340 because at 60 knots 340 fpm would be required. The required vertical speed depends on your groundspeed such that 60/340 = groundspeed/a. If you fly the approach at 105 knots the vertical speed must be 600 fpm. At 90 knots the vertical speed must be ______ fpm. At 140 knots the vertical speed must be ______ fpm. The above calculation will be needed for every non-precision IFR approach you fly, so it is important to become comfortable with it. You should open your CAP at random and calculate the descent gradient for the final approach segment of many non-precision IFR approaches (i.e. not ILS approaches), and resulting vertical speed at your airplane’s approach groundspeed, until you can do the calculation quickly and effortlessly. Examining the Abbotsford approach plate once again, we see that in the intermediate approach segment the airplane must descend from 2500 to 1700. How far back from the XX NDB should this descent begin if the pilot wishes to maintain a descent gradient of 340 ft/NM (the previously calculated gradient for the final segment)? Setup your CR as required before reading the next paragraph. Page 120


The airplane must descend 700 feet (2500 – 1700.) The relevant ratio is 340/1 = 700/a. The answer is about 2.1NM. If the pilot wishes to limit the intermediate segment to a gradient of 320 ft/NM the descent should start ______ NM from the XX beacon.

Standard Decent Gradient is 3° The gradient to rate conversion discussed above is primarily applicable to non-precision approaches. The importance of the calculations demonstrated should be obvious. On a precision approach (e.g. an ILS) a glidepath indicator directs the pilot to the runway so calculation is not as necessary. It is however beneficial to examine the required descent rates, which we will do now. Most precision approaches are set to a descent angle of 3°, which is a gradient of 320 ft/NM. Some precision approaches use other gradients. Legally a precision approach can have glidepaths in the range 2.5° to 4.0°.

The above diagram shows a 3° descent, which corresponds to 320 ft/NM. This can be calculated using basic trigonometry. Tan (3) = a/6080 (recall that 1.0NM is 6080 feet.) Using an electronic calculator a equals 318.7, which we will round off to 320. How many nautical miles are required for a descent of 1000 feet on an ILS? Setup the required ratio on your CR before reading the next paragraph. The required ratio is 320/1 = 1000/a. The answer is 3.1NM. The above relationship is VERY IMPORTANT. However, most pilots round it off to 1000 feet per 3.0NM, which is close enough for typical purposes and allows quick and easy calculations in your mind without needing a CR. Below are some typical applications. Work them out based on the ratio 1000/3; if you like you can rework them based on the more accurate 320/1 to see if the difference is significant. The tower asks you to report 2NM on final; what altitude will you be at? Setup your CR before reading the next paragraph.

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The ratio is 1000/3 = a/2. You should report 2.0 final when you are 666 above ground level (note that you can thus report 2.0 final even if your airplane is not equipped with DME.) If you had used the more precise ratio 320/1 your answer would be 640agl. From a practical point of view reading the difference on your altimeter and then reporting would be impossible. You are going to intercept the glidepath at 3000agl, how far from touchdown will you be? Setup your CR before going on. If you set 1000/3 = 3000/a; the calculation is so simple you hardly need a CR. You will be 9.0NM from touchdown. If you set the more precise ratio 320/1 the answer is 9.4NM. This is the actual distance, but since your primary purpose in such calculations is usually just to keep a mental image of how far you are from touchdown the difference between 9.0 and 9.4 is probably not significant. You are flying an ILS approach with a groundspeed of 120 knots, what vertical speed do you require? Setup your CR before reading the next paragraph. The required ratio is 60/320 = 120/a. The answer is 640 fpm. This is an important calculation, but given that positive guidance is provided by the glidepath it is really only necessary to approximate this calculation. With your CR set to 60/320 what is the value of 1/a. Note that a equals 5.3. This ratio tells us that we need 5.3 fpm for every knot of groundspeed. Pilots routinely round this off to 5.0. From this comes the rule of thumb that vertical speed should be 5 x groundspeed. Using the 120 knot example we get 5 x 120 = 600 fpm. We know the correct answer is 640, but 600 fpm will get you started close enough, you then follow the glidepath indicator, which will take you directly to the runway. Summarizing what we have learned about flying 3° precision approaches. In order to facilitate mental calculations while flying ILS approaches pilots use the ratio 1000/3 or 100/.3 to approximate the descent gradient. Pilots also use the formula 5 x groundspeed to approximate the descent rate. Use the approximations to answer the following questions without using your CR or any other calculator. Your company SOP is to call 100 above as you approach the glidepath check altitude. You will be ____ NM from the checkpoint when you make this call. You will intercept a glidepath 600 feet above the glidepath check altitude. That will be _____ NM from the FAF. Your groundspeed is 100 knots; the required descent rate is ______ fpm. Your groundspeed is 85 knots; the required descent rate is ______ fpm. You are 400 agl when the tower asks, “How far back” you are. Your answer is _____ NM.

TAS and CAS Conversions The situation is that you are flying along in your King-Air at FL250. You read the airspeed indicator and it says 170 KIAS. You look at the thermometer and it says -21°C. What is your TAS?

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It is important to know that the actual air temperature is NOT -21°C; the friction of the air rushing past the temperature probe causes an error and the actual temperature is colder than -21°C. We will see how much colder shortly. FL250 means that your altimeter is set to 29.92, so your pressure altitude is 25,000’. From the King-Air POH we look at the calibration chart to see what our CAS is. At 170KIAS there is no error, so our speed is 170 KCAS. On the CR (CAS window) set 170 KCAS opposite 25,000’ pressure altitude, as shown below.

Keeping the CR in that position, rotate it so you can look at the TAS window. Set the indicated temperature hairline to -21°C and read the TAS on the scale, see photo below.

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TAS is 252 or 253 KTAS and the Mach number is 0.415. Temperature rise (see photo below) is 8.2°C, in other words the actual temperature is -29.2°C.

There are lots of sample problems like the one above in the assignments. Remember that when doing this sort problem with your CR you would be in flight and checking that your TAS is working out as flight planned.

Derive CAS given TAS and Forecast Temperature In this situation we are doing flight planning, i.e. we are still on the ground. From the POH we find the true airspeed and the FD forecast gives us the temperature. Our job is to predict the indicated airspeed (IAS.)

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It is much simpler to do this for airplanes that fly less than 200 knots and less than 20,000 feet because we can disregard compression error. The CR has two techniques: 1.

A quick and simple technique that does NOT compensate for compression; for aircraft slower than 200 knots

2.

A two-step procedure that accurately allows for compression. This can be used for all airplanes, both fast and slow; but MUST be used for fast airplanes.

You are expected to learn both procedures and apply the two-step procedure when needed (i.e. for any airplane flying faster than 200 knots, or higher than 20,000 feet.) Of course you can always use it, but it takes longer and is not needed for slow airplanes like the C-172 or B95; for the King Air you must use procedure 2. Obviously jet pilots always use procedure 2.

Procedure for “Slow and Low” Airplanes In your CR manual this is referred to as the “old method” and is described on page 21; even though it is called the old method, use if for the C-172 and B95 because it is quick and easy. The error will be 1 knot or less. A comparison between this and the professional method below confirms this claim. For a C-172P the following data apply: Altimeter setting 30.35 Cruise altitude 8500 indicated Forecast temperature at altitude -12°C 65% power

Given the above, Pressure altitude in cruise is 8070’ From the POH, TAS will be 111 KTAS

Predict the IAS?

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Line up the temperature of -12°C with the PRESSURE ALTITUDE of 8070’, as shown in the photo above.

Take care to keep the above values aligned while you locate the TAS on the outer ring. CAS appears directly below it; in this case 111KTAS equals ~101 KCAS.

To get the indicated airspeed look in the calibration chart on page 5-8 of the POH. In this case indicated airspeed is about 2 knots more than calibrated so the final answer is 103 KIAS.

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You will be using the above procedure over and over, on all your flight plans for the C-172P and Beech 95, so make sure you can do it without hesitation.

Procedure for “Fast and High” Airplanes In your CR manual this is referred to as the professional method. Once you get good at it you can do it quite quickly even though it requires two steps: 1.

Determine cruise Mach number

2.

Use Mach number to determine CAS

3.

You can then also determine temperature rise if needed

The procedure works because temperature affects calibrated airspeed and the speed of sound equally and therefore the effects offset. For a given Mach number there is one CAS for each pressure altitude, regardless of TAS. An IMPORTANT point to note before we go further is that since the TAS window on the CR works with INDICATED temperature (see photo below) and indicated is NOT the same as actual air temperature, you cannot use the TAS window to predict CAS by reversing the procedure covered above.

The proper procedure is to first determine your Mach number. To do that you need to know TAS and the speed of sound. Your POH gives you TAS and the CR gives you the speed of sound. For a King-Air the following data apply: Altimeter setting 29.92

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Cruise altitude FL230. TAS 276 KTAS Forecast temperature at altitude -30°C

What is the CAS and IAS?

Mach number is simply the ratio TAS/speed-of-sound. Using the method described earlier reveal the Mach Index by setting 600 knots over 1 on the outer scales (this is shown below.)

Next set the actual air temperature on the Mach index to get the “real” speed of sound. The photo below shows the Mach index set to -30°C. On the outer scale you should now see that Mach 1.0 corresponds to 606 knots. If you were at Mach 2.0 your TAS would be 1212 KTAS, what is your TAS if you are at Mach 0.8, 9 what is it a Mach 1.4?

9

850 KTAS

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Returning to our problem, we know that our TAS is 277. What is the Mach number? You can read it on the scale as shown below.

Locate the TAS on the outer scale and read the Mach number. In this example true airspeed of 276 corresponds to Mach 0.455. Notice that when air temperature changes Mach number changes, but altitude per se is irrelevant. You are now ready for the second step. Go to the TAS window and set the Mach number as shown below.

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With the Mach number set look in the calibrated airspeed window across from 23,000’ pressure altitude to get the CAS. The photo below shows the result.

In this example CAS is 195 KCAS, which is roughly 197 KIAS according to the POH. This procedure works because ANY airplane at FL230 and Mach 0.455 has a calibrated airspeed of 195 KCAS, regardless of temperature. You will be using the above procedure many times in flight planning so make sure you go over it until you can do it without hesitation.

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Comparing Procedure for slow and fast Airplanes First, use the professional method on the C-172P problem previously solved with procedure slow airplane procedure. Setting the Mach index to -12°C the speed of sound becomes 628 knots. More importantly cruising at 111 KTAS corresponds to Mach 0.1765. Set this in the TAS window as shown below:

In the CAS window locate the pressure altitude, which is 8070’ and read the calibrated airspeed, as shown below:

The result is ~100 KCAS, which is exactly what we got using the slow airplane procedure. So both procedures clearly work for the C-172P. Now let’s find out what happens if we use the slow airplane procedure for the King Air problem. Page 131


In the pressure altitude window set the temperature of -30°C over the pressure altitude of 23,000 as shown below:

Now locate the TAS of 276 on the outer scale and read the CAS. This is shown below:

The value of less than 192 is obviously wrong. We know the correct value is 196. The four knot error may not seem like a big deal, but it is certainly enough to get the wrong answer on your ATPL written exams. The error gets larger as you fly higher (as in jets.) So we have confirmed that we cannot use the slow airplane procedure for the King Air.

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Sample Questions 5 Use the “Professional Method” to complete the last two columns of the table below: CAS

Pressure Altitude

Indicated OAT

145

5,000

2°C

315

25,000

-12°C

280

30,000

-15°C

280

40,000

-15°C

TAS

Mach number

Read the section labeled “Old” Method on page 21 of the CR Handbook. Repeat the calculations using the old method. This time you do not need to determine Mach number: CAS

Pressure Altitude

Indicated OAT

145

5,000

2°C

315

25,000

-12°C

280

30,000

-15°C

280

40,000

-15°C

TAS

Actual Air Temp

105

12°C

105

-20°C

145

5°C

235

-12°C

380

-56°C

440

-56°C

Mach number

Fill in the right hand column:

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TAS

Error


Mach Number

Pressure Altitude

0.16

8,500

0.17

8,500

0.224

6,000

0.373

21,000

0.67

32,000

0.775

38,000

CAS

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Chapter 6 The Canada Flight Supplement The Canada Flight Supplement (CFS) is one of the most important documents for flight planning. You must become familiar with all the information it contains and be able to locate what you need quickly and efficiently. The most used part of the CFS is section B, which gives data about all the registered airports and aerodromes in Canada. However, to get maximum value from this data you must use the index in the general section, part A. Get to know the codes used to describe public facilities (PF) lighting, etc. You will be given a number of assignments to develop expertise in decoding the CFS. As mentioned previously the CFS contains many useful pieces of information in the later sections. This includes preferred IFR routes for both high and low altitude. In the assigned cross country flights you will need to consult these. These can be found in section C, Flight Planning. Section D contains a lot of useful information about the location of navigation radios, VOR/DME frequency allocations etc. Section E is perhaps the most neglected yet vital section. It contains various emergency procedures such as intercept orders and procedures in the event of an emergency landing. Every pilot should read and understand this section. Become familiar with all the information in the CFS. Expect questions drawn from the CFS on all your exams.

Weather and NOTAMS Checking weather and NOTAMS before flight is essential for flight safety. You will learn to decode weather in Avia 120 and NOTAMs in Avia 130. They will not be covered here.


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Chapter 7 Navigation Theory In this section you will learn about the compass, the shape of the earth, maps and globes and other theory elements that impact on navigation.

Shape of the Earth The earth is very close to being a perfect sphere, but due to its spin the equator bulges slightly, which makes the shape an oblate spheroid. The earth spins around an axis that astronomers can locate. This defines the north and south poles. We will learn about the magnetic North and South Pole later. For now simply realize that the true North and South Poles are based on the spin of the earth and are NOT the same as the Magnetic Poles. The original definition of the metric distance unit “meter” was that the distance from the equator to the pole is 10 million meters, i.e. 10,000 Km. Therefore the circumference of the earth is 40,000 Km measured around the poles. Because the equator is a bit fatter, as mentioned above, the equatorial circumference is 40,076 Km. The aviation unit of distance is the nautical mile, which is also defined in accordance with the circumference of the earth. Every degree of latitude is by definition 60 NM, so the circumference of the earth is 360 x 60 = 21,600 Nm, measured around the poles. The distance around the equator is an extra 41 NM. From the above discussion you should memorize the definition of the nautical mile and take note that the difference in circumference of the earth around the poles vs. the equator is less than .00002%. If the earth was shrunk down to the size of a billiard ball it would be a smoother rounder billiard ball than any you will find in a pool hall. The earth spins around an axis that runs through the north and south poles. It spins once every 24 hours, which defines one day. Due to the gravitational effect of the moon and sun the earth’s spin is gradually slowing down, but it will take billions of years before it stops spinning relative to the sun. The rate of slowing is however enough for atomic clocks, such as those in GPS satellites, to measure so they must be resynchronized with the rotation of the earth every 1000 weeks (roughly every 20 years.) Other clocks are synchronized just before midnight on December 31 each year making the last day of the year the longest by a few millionths of a second. An interesting anomaly that results from this variant resynchronization is that earth clocks and GPS clocks move out of synchronization over the 1000 week GPS cycle. A computer program in your GPS receiver calculates the difference so that the time displayed to you is approximately equal to earth time, and different than “GPS time.”

Latitude


A grid system known as latitude and longitude has been devised so that the location of any spot on the earth can be specified, rather like the (x,y) Cartesian coordinate system you already know. Take note that the latitude/longitude system is devised on a model of the earth that assumes a perfect sphere. As mentioned above the earth is not a perfect sphere, but the difference is such a tiny fraction of 1% that it can be ignored for our purposes. Lines of latitude run around the earth east to west and exactly parallel to each other and perpendicular to the earth’s axis of rotation. Latitude is measured as the angle from the center of the earth with the equator defined as zero degrees, and therefore the North Pole is 90°N latitude and the South Pole is 90°S latitude. This is shown in the diagram below.

Every degree of latitude is 60 NM. The subunits of latitude are called minutes. There are sixty minutes per degree, so each minute of latitude is one nautical mile. If you know the latitude of two places you can calculate the north/south distance between them. Castlegar is at N49 17.76 while Prince George is N53 53.37 (note the format, more on that shortly.) The difference is Page 140


4 degrees 35.61 minutes. 4 degrees equals 240 NM and 35.61 minutes equals 35.61 NM so the total distance is 275.61 NM. Please note that this is the north/south distance only, there is also an east/west component that we turn to next.

Longitude Because the earth has poles there was no controversy about setting up a latitude system. The lines of latitude run parallel to each other and are equidistant apart. But there is no equivalent to the equator to act as a starting point for a grid system in the perpendicular orientation. All locations on the earth are equal in the sense that the earth spins once per day so every spot on earth has a noon and a midnight, these are different for each location. In the historical period when accurate measuring of the earth first became possible the British were the dominant world force, therefore the PRIME MERIDIAN runs through London England, specifically the Greenwich observatory. Meridians of longitude are straight-lines that run north/south through the poles. Every location on the earth has one, but the one that runs through Greenwich is designated as 0° longitude. Every other location is therefore specified as east or west of the Prime Meridian with 180E or 180W (the same place) being the maximum longitude. 180W is about the middle of the Pacific Ocean, and runs very close to New Zealand, so it is true to say that New Zealand is on the opposite side of the earth to England. Castlegar is W117 37.95, i.e. 117 degrees and 37.95 minutes west of the Prime Meridian. Meridians of longitude DO NOT run parallel to each other. Every one passes through the North and South Poles, so the distance between them is zero at the poles. What is the distance between them at the equator? Based on the model of the earth that says it is a perfect sphere the distance between lines of longitude at the equator is 60NM. What is the distance between lines of longitude in Castlegar?

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Castlegar is at N49 latitude and so is Gander Newfoundland. The picture above shows a view of the globe from above the North Pole, the outer ring represents the equator, so both Castlegar and Gander are on the th 49 parallel of latitude. The diagram is drawn to scale, so it might seem odd to you that N49 is closer to the equator than the North Pole, but a sphere’s circumference does not vary linearly, it varies with the cosine of the latitude. Castlegar is at W117, which means it is 117° west of the prime meridian in Greenwich England (Greenwich is about N52 latitude, but that doesn’t matter.) Gander is only 54° west of Greenwich, so it is a lot closer to England than Castlegar. Between Castlegar and Gander the difference is 63° degrees of longitude. How many nautical miles is that? If Castlegar and Gander were on the equator each degree would be 60NM so it would be easy to figure how far apart they are. But clearly each degree of longitude is less than 60NM in Castlegar. The distance between degrees of longitude is given by: 60cosine(latitude). The cosine of 49° is about .66 so each degree of longitude equals ~39 NM at that latitude. The distance from Castlegar to Gander is 2598 NM. Page 142


Given the latitude and longitude of any two places on earth the distance between them can be estimated using Pythagoras theorem. The diagram below shows two points marked by Xs and the east-west distance 10 (EWD) and north-south distance (NSD) between them. NSD is very easy to figure out as we have seen. EWD is almost as easy to figure – you should use the mid-latitude between the two points when taking the 2 2 0.5 cosine of the latitude. Distance is simply (EWD + NSD ) .

The ENL has a latitude-longitude calculator that uses the above formula. It also determines true track between the points, but we will defer discussion of that until we examine some map theory.

Great-circles A Great-circle is a circle on the surface of the earth whose center passes through the center of the earth.

10

The technical term for EWD is “departure.”

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A segment of a Great-circle is the shortest distance between two points. The equator is a Great-circle but the other lines of latitude are NOT. All the meridians of longitude are semi-great-circles, i.e. half Great-circles. An important fact about Great-circles is that, except for the meridians and equator, they change direction (angle) relative to true north as you fly along them. To visualize look at the diagram below and remember that true track is the angle between meridians and the desired track (DTK.) Any eastbound flight must change heading to the right continuously to stay on the Great-circle. A westbound flight must continuously turn left.

Small Circles Any circle on the surface of the earth whose center does not pass through the center of the earth is a small circle. An important point to note here is that no circle can be drawn on the surface of the earth that is larger than a Great-circle, so all other circles are smaller than Great-circles, hence the name. Page 144


All the parallels of latitude except the equator are small circles. Is a segment of a small circle the shortest th distance between two points? For example the 49 parallel runs from Trail to Vancouver, and can be visually seen in flight because the trees have been cut down along it. If you fly this line, on a true heading of 270°, is that the shortest distance between Trail and Vancouver?

th

The answer is no. Imagine that the 49 parallel as a ring resting on the globe (see photo above); it is a small circle. Imagine what you must do to change this small circle into a Great-circle. You must enlarge the circle and rotate it so its center passes through the center of the earth (and keep Trail and Vancouver as th points on the circle.) In the process the Great-circle line would arc north of the 49 parallel. Following this Great-circle track would be the shortest route to Vancouver, but you would no longer be able to fly a constant heading. We turn to that matter next.

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Photo shows wire stretched around globe to represent a Great-circle.

Convergence Convergence is the angle that a Great-circle track changes over its length. In the above diagram DTK 1 is 030° and DTK4 is 100° so convergence is 70°. The pilot must change heading by 70° from the start of the flight to the end in order to follow the Great-circle route. Convergence can be estimated as: Convergence = Δ Longitude x sine (average latitude) A flight along the equator (latitude 0; sine (0) is 0) has no convergence, but a flight near the poles has a great deal (sine (90) is 1, so convergence equals change in longitude at the poles.) A flight from Castlegar to Gander has a convergence of _______. Try to figure it out yourself before turning the page. The lat and long of each airport is given above. Convergence Castlegar to Gander = 63 x sine (49) The convergence between Castlegar and Gander is 48° What is the convergence between Castlegar and Vancouver? Longitude in Castlegar is W117 and Vancouver is W123 (difference of 6°.) Convergence Castlegar to Vancouver = 6 x sine (49) The convergence between Castlegar and Vancouver is 4.5° To fly a Great-circle from Castlegar to Vancouver the true track start as 272.25°, half-way the track is 270° and as the airplane flies into Vancouver the track is 267.75°. The total change in heading is 4.5°, and as previously noted a westbound flight must change heading to the left. Try to figure out for yourself the initial, mid, and final heading to fly the Great-circle from Castlegar to Gander. Most pilots would say that it is much more convenient to fly on constant heading for the entire flight however. We turn to that point next.

Rhumb-Line A Rhumb-line is a constant-track line between two points. In other words it is a line that crosses all the meridians along the route at the same angle. The advantage of a Rhumb-line is that you can fly one true-heading (TH) to get from departure to 11 th destination . In the Castlegar to Vancouver example above, following the 49 parallel, and maintaining a

11

Note that the magnetic heading will still change if variation differs along the route (as it usually does.) Page 146


true heading of 270°, constituted flying a Rhumb-line. Pilots generally find this much more satisfactory than constantly changing heading as they must to fly a Great-circle. The distance penalty for flying a Rhumb-line as opposed to a Great-circle is not significant for flights up to 500 NM at moderate latitudes (i.e. flights not near or over the poles.) Therefore on short flights pilots routinely fly Rhumb-lines. On longer flights, such as international airline flights, a Great-circle can be approximated by plotting a series of checkpoints along the Great-circle 500NM or less apart and then flying Rhumb-lines between them.

In the above diagram a long-range airline flight approximates a Great-circle by flying over a series of checkpoints (Xs) along the Great-circle but a constant heading is flown between these checkpoints. I.E. a Rhumb-line is flown between the checkpoints. The pilot has a nav-log showing checkpoints and one heading between checkpoints (just what pilots like.) In the days before flight management systems (FMS) this was the normal navigation method. Modern FMS makes accurate navigation along Great-circles feasible, and that is now the norm. Notice that the Great-circle track is ALWAYS closer to the pole than the Rhumb-line, or if you prefer, the Rhumb-line is always closer to the equator. Remembering this will help you figure out which way heading must be adjusted to fly a Great-circle.

Map Theory Now that we know all about Great-circles and Rhumb-lines it is time to talk about maps. It is not practical to flight plan using a globe, and we certainly can’t take one in the airplane, so we need a map, which is a flat piece of paper representing the surface of the earth. Obviously there is a problem because the surface of the earth is curved, NOT FLAT. Imagine cutting open a tennis ball and trying to spread it out flat. You Page 147


could not do it. Therefore ALL MAPS ARE DISTORTED. The method of creating the map determines what type of distortion, but all maps are distorted. All maps are created by “projection” which you can visualize as meaning that a glass globe is created with all the surface features on it. A light is placed at the center of the globe and photographic paper is then held over or wrapped around the globe. The surface features of the earth are therefore projected onto the photograph and a map is created. The only difference between one map and another is the way the photographic paper is wrapped around the globe. The dominant projection used in Aviation is the Lambert Conformal, Conic projection. In Canada it is used for: VFR navigation Charts (VNC) World Aeronautical Charts (WAC) LO and HI IFR charts

The other projection that is widely used is the Transverse Mercator. In Canada it is used for: VFR Terminal Charts (VTA) IFR Terminal Charts (T1 T2) Polar charts

We will now examine each of these projections.

Lambert Conformal Conic Projection

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The photo above is from a Vancouver VNC chart, commonly used for VFR navigation. Circled is the note that it is a Lambert Conformal Conic Projection. Lambert is the name of the person who invented it. We will examine what conformal and conic mean. The word “conform,” according to the dictionary means: “to be similar or identical.” A conformal map is one that shows the earth in the same shape that it has in the real world. We already said that this is impossible however, so a more technical definition is needed. A map is conformal if at every location on the map the scale distortion north and south equals the scale distortion east and west. Lambert’s conic projection comes very close to meeting this standard. It is not perfect, but good enough to be designated conformal. On a perfectly conformal map a straight-line is a Great-circle. On a Lambert Conformal Conic projection a straight-line can be accepted as “close enough” to a Great-circle for navigation purposes. The error is less than 0.5%. To be useful a map must have a scale. You obviously don’t want a map that is as large as the earth. The photo above shows the scale on a VNC is 1:500,000, which means that one inch on the map equals 500,000 inches in the real world (1cm equals 500,000 cm etc.) 500,000 inches equals 6.9 NM so one inch on the map equals 6.9 nautical miles. On a perfectly conformal map the scale is constant throughout the map, but real maps are never perfectly conformal. The scale of 1:500,000 is therefore the average scale of the map. In the middle of the map it is a bit more, but near the top and bottom it is a bit less. The difference is less than 0.5% and therefore you can ignore it. Let’s see why there is an error at all.

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Imagine a sheet of photographic paper formed into a cone and set over the globe (like a hat) with its apex at above the North-pole. This would be a standard conic projection, and it would touch the earth along only one parallel of latitude. Lambert’s innovation was to sink the cone into the earth so that it touches along two parallels of latitude, as shown in the photo above. Between the standard parallels the surface of the real earth is above the cone, and north and south of the standard parallels the surface of the earth is below the cone. The consequence of this to map scale is shown below.

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The diagram above shows projection lines emanating from the center of the earth and passing through the surface of the earth and the map. It is important to consider where a given point on the actual surface of the earth appears on the map. North and south of the standard parallels points on the map are further apart than on the earth’s surface (if you measure a distance of say 100 NM on the map the real distance on the surface of the earth is less.) Between the parallels the opposite effect takes place. Along the standard parallels the scale of the map is precise. The photograph at the beginning of this section showed that the standard parallels for the Vancouver VNC are N49 20 and N54 40. Along these lines map scale is accurate. As stated previously the scale error over the entire map is about 0.5% so you can feel free to measure distance anywhere on the VNC for navigation planning purposes. Different standard parallels are used on VNCs to suit the latitude of the area depicted. Summary of Lambert Conformal Conic Projection 1.

Straight lines are Great-circles (close enough)

2.

Scale is constant throughout (close enough)

3.

Rhumb-lines are NOT straight

Because Rhumb-lines are not straight, if you want to fly a Rhumb line you must measure the true track at mid-leg. At mid-leg a Rhumb-line track and a Great-circle track are equal.

Transverse Mercator projection Page 151


Originally Mercator projections were developed for use near the equator. The Lambert Conic projection does not work for areas near the equator. In the original Mercator (not a transverse Mercator) the photographic paper is rolled into a cylinder rather than a cone. This cylinder is wrapped around the earth so that it touches along the equator.

On the Mercator projection the lines of latitude and longitude come out perpendicular to each other. This has the advantage that a straight-line drawn on the map is a Rhumb-line, but the map is NOT CONFORMAL. In other words it distorts shapes, and a straight-line is NOT a Great-circle. At the equator the lines of longitude and latitude really lie perpendicular to each other so the Mercator map is relatively conformal near the equator; but is not useable in Canada. The Transverse Mercator also wraps the globe in a cylinder but it is rotated 90 degrees so that it touches the earth along a meridian of longitude rather than the equator. The cylinder can be rotated so that it touches on any of the 360 meridians. The map scale is accurate only along the reference meridian.

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A transverse Mercator map is NOT conformal, but as long at only a small section, close the reference meridian, is used the distortion is minor. It has the advantage of creating a grid in which lines of latitude and longitude cross perpendicular to each other. Consequently a straight-line drawn on the map is a Rhumb-line. The Transverse Mercator projection is only suitable for small scale maps such as terminal charts. It is used for VTA and IFR terminal charts.

True and Magnetic North (Variation) So far all discussion about tracks has been in relation to true north, i.e. the North and South Poles. Meridians of longitude run north/south by definition. When measuring a true track on a map you must align north on the protractor with a meridian. st

In the 21 century as GPS navigation becomes dominant it is probable (or at least possible) that true tracks and true north will become the only references used for navigation. But, not all airplanes have such equipment today, so a magnetic compass must be used. Unfortunately the Magnetic North Pole is not collocated with the real North Pole. The photo below shows the location of the Magnetic North Pole.

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A compass points at the Magnetic North Pole. A compass on the white line in the photograph also points at the true North Pole. But a compass in British Columbia, as shown in the photograph, points too far east. The error is called variation, and it is the angle between true north and magnetic north. The variation shown in the photograph is easterly; in Montreal variation is westerly. On a line running through Manitoba there are locations where variation is zero (as shown in the photograph.) An isogonic line joins locations with equal variation. All aeronautical maps have isogonic lines printed on them. These lines are labeled as shown in the photo below.

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In the above case variation is 23° East. In flight the heading indicator is normally set to magnetic north and all heading are referred to as magnetic headings. Flight planning is normally done in true however, so true heading must be converted to magnetic before the flight. The following rhyme may help you remember whether to add of subtract variation. Variation East, magnetic is least Variation West, magnetic is best

This means that when variation is easterly the magnetic heading is always less than true heading. When variation is westerly magnetic heading is always more than true. Even though the above rhyme is fairly simple it is best to use your CR to convert between magnetic and true so that no mistake is made. This procedure was demonstrated previously.

Compass Deviation The topic of deviation is out of place here since it is not related to map theory, but it does fit logically here because of its relationship to variation. Deviation is an error in the compass of the airplane. As such deviation is specific to an individual airplane. It is caused by the magnetic fields of the metal parts of the airplane and is significantly affected by electrical equipment such as the alternator. These things cause an error in the compass known as deviation. Deviation changes from time to time. That is to say that the magnetic field of the airplane changes over time. Consequently it must be measured and recorded on a regular basis. The process of measuring

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deviation is called a compass swing. A compass swing is required every year and also any time electrical equipment is removed or replaced in the airplane. An AME performs the compass swing and provides a compass card in the cockpit which the pilot uses to correctly set the heading indicator. The pilot should read the compass then the deviation card and set the heading indicator to the corrected magnetic heading. Deviation is seldom more than 2 or 3 degrees so ignoring it, as most pilots do, results in only minor error.

Contour Lines and Hypsometric Tints Maps for aviation MUST show the height of the ground. This is one of the most important details for flight safety. Contour lines and hypsometric tinting are used for this purpose. Contour lines are lines that join points of equal elevation above sea level.

The above photo shows contour lines on a VNC. On VNC charts there is a 500’ contour but from 1000’ and above contours are every 1000’. The contour interval is described at the bottom of the Hypsometric scale, explained next. To make terrain easier to visualize Hypsometric tinting is used, according to scale below:

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The above scale is found on the white edge of every VNC. At the top of the scale you find the maximum elevation for the map. The example above is 19,524’ asl, the highest point in Canada; located at N60 34 W140 24, also shown just above the hypsometric tint scale. A 500’ intermediate contour line appears within the lowest hypsometric tint, and intermediate contours at 4000’, 6000’, 8000’, 10,000 and 11,000 are also plotted. Use these to refine the information provided by the tinting.

Map Legend Every map has a legend printed along the edge that shows all the symbols used on the map. All the symbols are important but will not be covered here as you can read the legend for yourself.

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Airport data is provided on VNC charts but this should only be used for preliminary planning. Always look in a current CFS for up-to-date airport data.

Map Scale The scale of the map is always printed on the map. The picture below shows the scale on the Vancouver VNC chart is 1:500,000. The same scale is used on all VNC charts in Canada.

WAC charts use a scale of 1:1,000,000. VTA charts have a scale of 1: 250,000.

An appropriate Navigation ruler must be used to measure distances on these maps. Make sure you use the correct scale. Always measure distance in Nautical Miles, not statute miles. The inner scale is used on VNC and the outer scale on WAC charts. For a VTA chart use the VNC ruler scale then double the distance.

Grid Navigation The picture below is of a globe from above the North Pole. Imagine you wish to fly from the checkpoint marked as departure to the one marked as destination. What is the true track?

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If you are willing to fly a Rhumb line, then heading of 090 true would take you to the destination along the line shown below:

But this is clearly not the shortest route. The desired route is “over the pole.” Page 159


In the diagram below the desired Great-circle route is drawn in as well as some lines of longitude for reference. We already know that in order to fly a Great-circle we must change heading as we fly, make a table of required true headings for the locations marked with the Xs. Remember that each line of longitude represents a true track of north (0°.) I.E. you must orient your Douglas protractor to north on each line of longitude.

The true tracks are as follows: Location

True Track

X1

019

X2

045

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X3

082

X4

137

X5

160

Imagine what would be happening on the flight deck as you make this flight. The airplane departs on a heading of 019° (essentially northbound) and flies a straight-line. But, the heading indicator must be adjusted so that as the airplane passes X2 it reads 045°. At X3 the HI is rotated to 082°; at X4 to 137°. When the airplane arrives at destination it has made no turns, but the heading must be 160° true (essentially southbound.) For ideal effectiveness HI would be continuously updated for convergence, in practice it is usually updated every 6° change in longitude. An alternate method of navigating over the poles is to use Grid navigation. Every flight over the poles starts off “northbound” and finishes “southbound.” Pilots must accept that brain teaser, but grid navigation eliminates the need to continuously update the HI enroute. Examine the diagram below.

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A rectangular grid is laid over the pole as shown in the diagram above. This grid can be oriented to by reference to any meridian, but the standard procedure is to use the Prime meridian as the reference. To use the grid simply put your Douglas protractor on the grid with north aligned with the Prime meridian. For the track in the example the track is 219G (read “219 Grid.”) Examine the diagram to convince yourself that the Grid heading is simply the true heading plus west longitude, or minus east longitude. The 160E median has been labeled in the diagram. You should label the other meridians corresponding to X2, X3, X4, and X5.

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To use Grid navigation, as the airplane approaches the departure point (it probably took off somewhere much further south) the pilot switches the HI to grid. This amounts to rotating the HI an amount equal to the longitude of the airplane. In practice grivation is applied to the magnetic compass. Once the HI is adjusted to Grid the pilot can maintain a constant heading for several hours (in the example s/he maintains 219°.) Even though this is usually considered a southbound heading the airplane is obviously still heading north. But things will work out in the end. The pilot holds this grid heading for a few hours until arriving at the destination (point where the transition back to magnetic headings will be made) at which point the heading is reset to magnetic by changing it from 219 to about 160° plus variation. Note that despite all these adjustments the airplane actually flies a straight line the whole time.

Grivation Grivation is by definition the difference between magnetic track and grid track. As previously noted the difference between true and grid tracks equals the longitude (from the reference meridian.) Therefore mathematically grivation equals longitude plus variation. Lines on a map joining points of equal grivation are called isogrivs. Pilots can use these to set the HI to Grid the same way they use variation to set the compass to true. However, the magnetic compass is quite unreliable in the extreme Polar Regions so it is much more common to use INS as the reference (the INS “knows” the airplanes true track) eliminating the need to use grivation. The two relevant equations are: Grid track = Magnetic Track plus E grivation or minus W grivation Grid track = True Track plus W longitude or minus E longitude You will examine grid navigation a bit more in Avia 240. For now this simple introduction to the concept is all that you need. You should see that grid navigation is necessary because of the extreme amount of convergence in polar crossings. Keep in mind that basing the grid to the Prime meridian is arbitrary. For some purposes it could be preferable to establish a grid based on a different meridian. For a Canadian arctic survey expedition might find it desirable to have a grid oriented to a meridian within Canada. Can you see the benefit of this? If they used the Prime meridian instead what direction would it be to fly from the Yukon to Greenland (east or west)? When they are done exploring the polar region do they fly north or south to return to Vancouver?

Plotting Lines of Position (LOP) A common task in navigation is to locate your position on a map based on a bearing from a VOR or NDB. Such a bearing is referred to as a line of position (LOP.) We will consider LOP from both VOR and NDB. Two LOP are needed to define a position fix.

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In the above diagram radial 1 represents one LOP and radial 2 is the second. Where they cross is the “fixed” position, or fix for short. Pilots frequently refer to the procedure as taking a fix. The process is quite straight forward, but there are a few important details. Most importantly fixes should be plotted using true bearings, not magnetic. But, most VORs are oriented to magnetic north, which means the nav radio tells you the magnetic radial you are on. Let’s say in the above example that radial 1 is 010R and radial 2 is 290R. You CANNOT put a protractor on each VOR and draw two lines based directly on these bearings. Each radial must be converted to a true bearing by applying variation. What variation should be applied to radial 1; which to radial 2? Choose your answer before reading the next paragraph. The important thing to realize is that you must apply the variation at the VOR, NOT at the airplane. Therefore radial 1 must be adjusted by 12° and radial 2 by 10°. Use the wind side of your CR to make sure you don’t make any mistakes.

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In the above photograph the 010R is set across from 12E variation. The true course is clearly 022°. Repeat the same process for 290R with variation 10E to confirm the true course is 300°. Plot the two tracks 022 and 300 by putting a Douglas protractor over each VOR in turn and aligning it with meridian 1 and 3 respectively. Draw the lines carefully to find the fix. To obtain an LOP from a VOR it is essential to center the CDI needle with a FROM indication. This gives a direct reading of the radial. If you center the needle with a TO indication you need to take the reciprocal (but it is safer to simply rotate the OBS knob until a FROM flag shows.) In the arctic VORs are oriented to true north, which eliminates the need to make the conversion demonstrated above. It is could be the case that you must plot a fix based on one VOR in magnetic and another in true. This is not difficult, just be careful to convert the magnetic radial to true while making no adjustment to the true radial. Do not attempt to plot a fix by extending the markings on the compass roses on the VNC. These are not accurate enough. IMIPORTANT. The legend of your VNC and LO chart warns you that in some cases VOR symbols are offset from their actual position, but the compass rose is centered on the actual location of the station. Check this carefully to ensure you are plotting the fix from the actual location of the VOR. Expect to see questions of the above type on Transport Canada’s Commercial Pilot Written exam. Watch for tricks such as offset VOR locations (previous paragraph) and mixed magnetic and true VORs (also mentioned above.) Now we will consider the process of establishing a fix based on bearings from two NDBs. There are two or three differences to note, but the overall process is the same.

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The diagram below is deliberately identical to the one above expect that the VORs have been replaced with NDBs. The first difference to think about is the process by which the pilot determines what bearing 1 and 2 are. How is this done? Formulate your answer before reading the next paragraph.

The basic process of obtaining a bearing from an NDB is the same regardless of the equipment the airplane has, but it is much easier with an RMI than with a fixed card ADF (Note that if you have a GPS this whole process is redundant since it will provide your current latitude and longitude, which you can plot to fix your position without the need to do any of this process. We therefore assume you have no such equipment available.) With an RMI read the bearing from the tail of the RMI needle. Good airmanship demands that you confirm the HI is set accurately before accepting this bearing. Usually the HI is set to magnetic so the bearing is a magnetic bearing. If you happen to be flying in the arctic with your heading indicator set to true then the bearing is true. And if your HI is set to grid you have a grid bearing. If you have a fixed card ADF you must follow the usual procedure to convert relative bearing to magnetic bearing. MB = RB + Heading. Since the diagram above is identical to the previous VOR based one, and the airplane is in the same location, you may expect that the magnetic bearings will be 010 and 290. They will NOT be. Think why before reading the next paragraph.

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In reality an ADF may not be accurate enough to detect the theoretical difference here, but the radio wave from the ground stations come to the airplane along straight-lines corresponding to Great-circles (both VOR and NDB.) This amounts to saying that the true bearings will be the same, but not the magnetic bearings. The variation correction for the VOR is applied at the station, while that for the NDB is applied in the airplane. Therefore both NDB bearings must be corrected by 11E. Go back and examine the VOR example above if you have forgotten which variation was applied in that case. Therefore magnetic bearing 1 is 013 and bearing 2 is 289 magnetic. Correct each of these magnetic bearings by variation of 11E exactly as described above for the VOR case. What values to you get? Once again the true bearings are 022° and 300°. Plot these exactly as before to get the fix. Summary: When plotting a fix convert all bearings to true. Apply variation at the station for VOR and at the airplane for ADF. Use the CR for converting between true and magnetic to avoid mistakes. Use a Douglas protractor centered on the station to plot the true bearing. Make sure the protractor really is centered on the station by checking the compass rose. Extend the lines until they cross, giving you a fix. On a Lambert Conic chart the straight-lines are Great-circles, which correspond to radio waves so this procedure works. On a Mercator chart straight-lines are Rhumb lines so an error equal to convergence is introduced, which you must correct for. Fortunately Mercator charts are only used for VTA and T charts in Canada, where position fixing is an unlikely procedure. It is quite possible to obtain a fix from one VOR and one ADF bearing. The process is identical to that described above. Just remember where to apply the variation. Watch out for combinations of true, magnetic, and grid navaids, especially on exams.

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Chapter 8 Flight Planning In this section we will take all the knowledge we have developed and use it to plan flights. It must be stated that we presume that dead reckoning (DR) will be the dominant form of navigation, with pilotage used only for brief periods usually on departure and arrival. In the section on mountain flying toward the end of the text some comments about planning for a flight when pilotage is dominant are included.

Definition of a Leg All flights are broken into legs. A leg is a defined path the airplane follows. Most legs are either straightlines or arcs. Future navigation systems may define paths that have more complex shapes, but that is beyond the scope of this text. Modern flight management systems (FMS) are programmed by entering a series of legs beginning at the airport of departure and ending at the destination. The entire route must be input as a series of continuous legs with no breaks at any point. The FMS computer recognizes a variety of leg types, which the pilot selects from a menu. When a flight is fully defined by a series of legs with no breaks we say the flight plan is closed.

Fly-by and Fly-over Waypoints Waypoints are designated as either Fly-by or Fly-over. The difference is sometimes quite important. The diagram below explains the difference more clearly than words can.


If a waypoint is designated Fly-over, you must fly directly over it before turning to the next leg. At a Fly-by waypoint you start to turn prior to the waypoint so that you intercept the next leg without overshooting it. You should normally treat waypoints as Fly-by unless they are specified as Fly-over. An exception is when using NDBs as waypoints, without GPS for assistance. It is far too easy to be misled about station passage with an NDB so it is preferable to treat all NDBs as Fly-over waypoints. In recent years it has become very common for aircraft to be equipped with GPS and or other types of precision navigation equipment that provide extremely accurate range information. These systems provide horizontal distance rather than the slant range the older DME systems provide. When the pilot has this type of instrumentation available it is possible to precisely determine when to turn for a Fly-by waypoint. The diagram below shows the required formula. The equation r=.0053 is fully explained in the aerodynamics text Aerodynamics for Professional Pilots.

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The formula might not seem user friendly but all you have to do is calculate .0053TAS once and memorize it. You already have memorized values for the sine of several angles for the purpose of estimating drift (see page 50.) To calculate .0053 TAS take TAS and divide by 100 then divide by two. For example if your airplane cruises at 120 knots divide by 100 to get 1.2 then divide by 2 to get 0.6. Remember this number. When approaching a 90° turn lead by 0.6NM. For a 45° turn lead by 70% of 0.6, i.e. about 0.4NM, etc.

Introduction to Nav-logs A nav-log is a document that helps you organize your flight planning so that you don’t forget any important details. It should chronicle your entire flight from takeoff to destination and then to the alternate airport if IFR. A nav-log should also include time and fuel allocations for contingencies (unavoidable delays due to weather, traffic, etc.), approaches, and reserve (reserve is a legal as well as practical requirement.) In this course you will prepare nav-logs both electronically and manually. On your commercial pilot flight test you are required to prepare the nav-log manually, and of course exams, most assignments, and ALL quizzes and tests in this course require manually generated nav-logs. On your actual cross-country flights and simulator exercises you are encouraged to use the ENL because it is quicker, easier, neater, and less

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likely to contain math errors. You were introduced to the ENL when we examined cruising altitudes, although we only scratched the surface on using it. Further details are provided later. Nav-logs are usually laid out in a grid with columns representing the parameters to be evaluated (planned) and with rows representing “legs.” .

Navlog Leg Groups The legs on your navlog can be divided into groups: 1.

Departure legs

2.

Enroute legs

3.

Arrival legs

4.

Approach

5.

Missed approach (IFR only)

6.

Enroute to alternate

7.

Arrival at alternate

8.

Approach at alternate

All these groups are needed for every IFR navlog. Groups 5 to 8 are not needed for VFR navlogs. On Selkirk College navlogs the departure, arrival, and approach leg groups are usually simplified so that one line on the navlog represents the entire group. We normally group the arrival legs with either the enroute or approach. The approach group is normally reduced to a single leg (for both IFR and VFR navlogs.) Departure legs can also be called “climb legs.” The departure legs end at the Set Heading Point (SHP.) The SHP is usually specified in an IFR departure procedure, but must be chosen by the flight planner for VFR flight. Advice on choosing a SHP is given below. There is a variable point at which the airplane reaches top of climb which is conveniently labeled as top of climb (TOC.) TOC may come before or after SHP. If after then it is technically part of the enroute group. On occasion TOC and SHP are the same point. Some VFR pilots find it convenient to “rig” the situation so that this happens. In this case label the point as SHP or SHP/TOC (preferred.) The largest part of most navlogs consists of several enroute-legs (also called cruise-legs.) These legs run from turning point to turning point. i.e. a new leg should start at every point where the track changes. The arrival legs end at an initial approach fix (IAF) for IFR flight plans. For VFR flight plans arrival legs end when the aircraft joins the circuit at the destination airport. Sometimes it is expedient to just treat these legs as cruise legs rather going to the trouble of estimating the reduced fuel flow used during the descent.

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Selkirk College nav-logs also contain rows allocating time for contingencies, and reserve (both explained below.) There is logic to the order that navlog rows are laid out that results in the pilot having the required information at hand in flight to make decisions about fuel status. Consider the nav-log below, which is for a flight in a Beech 95. Even though you have never flown one before answer the following questions by referring to the nav-log. 1.

As you taxi out in Calgary your fuel quantity should read _________ gal.

2.

As you pass YNY your fuel quantity should read ________ gal.

3.

As you reach BOOTH your fuel reads 35 gallons – is fuel remaining as expected?

4.

Upon arrival at BASRA, if ATC requires you to hold (perhaps because a runway is closed) your contingency fuel is used up when your fuel gauges read _______ gal (assume you wish to retain 13 50 minutes reserve.)

12

Notice that you can answer these questions quite easily because of the logic by which the nav-log is laid out.

12

No. You are supposed to have 37.8, so either the gauges are not accurate, or you have used a couple of gallons more than expected. You should assume the later. 13

27.2

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Ramp Fuel and Fuel Remaining As you saw above the fuel remaining column is one of the most important for in-flight decision making. When completing a nav-log you have two situations: 1.

The fuel for the trip is specified in advance and you determine consequent reserve

2.

You plan for a desired amount of contingency and reserve fuel and determine how much ramp fuel you need for the flight

If situation 1 applies, begin by filling out the ramp fuel in the upper right corner of your nav-log. As you complete each leg subtract the fuel used to get fuel remaining; whatever you have when you get to reserve, which is always the last row, is your reserve. Assess reserve fuel value to confirm that it is adequate before committing to the flight. If situation 2 applies, leave ramp-fuel and fuel-remaining blank until all legs have been planned. Fill out the reserve fuel and work backwards until you determine the required ramp fuel.

Choosing a Set Heading Point (SHP) A crucial task when preparing a nav-log is determining the checkpoints, in other words establishing what the legs will be. Most checkpoints will be pretty obvious, but choosing a suitable SHP is sometimes a problem, especially for VFR flights (Note that IFR flights require an SHP also, but usually it is obvious where it should be.) The first fixed checkpoint is called the set heading point (SHP) on a DR cross-country and choosing it requires considerable thought. For VFR flight you should select a SHP that is easy to locate and relatively close to the departure airport. Exactly how close depends on several factors: 1.

Availability of distinctive ground features for pilotage to the SHP

2.

Traffic congestion at the airport

3.

How well you know the area and the SHP checkpoint

On a VFR flight you normally use pilotage to find your way to the SHP. On IFR flights the SHP is usually a navaid such as a VOR or NDB so finding your way there is straight forward. VFR pilots can also use beacons and VORs for navigation but before doing so consider whether you will conflict with IFR traffic. It is frequently safer to choose a visual point rather than a radio navigation point when VFR. Because pilotage is used to locate the SHP be sure to pick one that has distinctive ground features leading to it. An ideal SHP is on a road, railway, river, or other similar feature that you can follow to locate it. A Page 175


SHP must also be distinct so that you can visually identify it. It must also be small enough to constitute a point – for example using “the city of Vancouver” as a SHP is not acceptable. Instead pick a particular point such as the intersection of two major roads, a park on a particular road, etc. If the ground around the departure airport lacks distinctive navigation features, as is often the case with small airports in northern Canada, use the airport as the SHP. This is called an “overhead departure.” You simply takeoff and climb over the airport to set course. Weather permitting you should be 2000agl or higher when you reach the center of the airport in order to avoid conflict with any circuit traffic. If you were making a closed navlog the first and third checkpoints would both be the airport and the second checkpoint would be 1000 feet. In reality you will probably open the navlog and only have one leg, i.e. the first and second checkpoints will be the airport of departure but the distance flown must represent that to fly out to 1000 and then return while climbing to 2000. Traffic congestion is a factor in choosing a SHP for two reasons. In the case of an airport with very little traffic it is quite feasible to make an overhead departure or use a SHP very close by. The lack of traffic means that no conflict will result. But, at a busy airport it may not be possible to do an overhead departure or use a nearby point as SHP; traffic congestion could force you to choose a SHP clear of the airport zone, i.e. more than 5 miles from the airport. In this case make sure to choose a SHP on a very prominent pilotage feature that you will have no trouble seeing and flying to. A point on a major road, river, or shoreline would be a good choice. Of course a radio navigation beacon could also be a practical choice if the airplane is suitably equipped. How well you know the area is a factor in choosing a SHP. At an airport you know well you can locate SHPs that would be too obscure if you didn’t know the area well; for example the intersection of two minor roads. Keep in mind that some objects that look prominent on a map are in fact quite difficult to see on the ground. For example locating a radio transmission tower, in daylight, is quite difficult and thus does not make a good SHP. But, if you know the tower well and can identify it relative to other local landmarks it may be an acceptable SHP.

Filling in the Navlog Now that we have a SHP it is time to fill out the nav-log. Normally we will have only one or two departure legs. It is very important however not to underestimate how much distance is flown when departing. Most pilots vastly underestimate this. Consider the example of taking off from CYCG and using the town of Robson as your SHP. Robson is only fly 3 miles from the center of the airport but the route and distance to get there is quite different depending on whether you takeoff on runway 33 or 15. It is best to plan the longer route, i.e. departure on runway 15, unless you know for sure that runway 33 will be used. A crucial thing to realize is that the distance you fly is more than the straight-line distance from the airport to the SHP, because you must allow for maneuvering to depart the circuit.

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Normally the above closed departure would be opened up by collapsing it into two legs, as shown below.

An interesting special case involves setting up the navlog for an overhead departure (remember this means using the departure airport as SHP) If you are doing an overhead departure the distance flown is certainly not zero (the straight-line distance) it is likely 5NM or more. An ENL navlog showing an overhead departure is shown below to demonstrate this.

When opening the departure on a nav-log: 1.

Estimate the distance to the SHP

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2.

Lookup altitude, time, and fuel corresponding to that distance

3.

Collapse the departure into one or two legs (more if needed for clarity.)

Once you have the distance use the time fuel and distance to climb chart to figure out what your altitude will be at the end of leg 1. Estimate the average wind in this calculation. Enter the fuel used and the time in the appropriate columns of. In 99% of cases, especially in the mountains, the distance required to climb to altitude will exceed the distance to the SHP. Therefore the first enroute leg will also be a climb leg (leading to TOC) as described below. When using the ENL, for departure legs, estimate how high you will be when you reach the SHP. The ENL determines distance, time, and fuel. If the resulting distance does not match your estimated distance to the SHP revise the altitude estimate.

First Enroute leg (to TOC) The first enroute leg is frequently a straight-line from SHP to TOC. The only exception would be on a flight where you reach TOC at or before SHP. In most cases you do not reach your final cruise altitude before SHP and therefore will be climbing enroute. The trick is figuring out how far after. If you did a reasonable job of estimating your distance and altitude to the SHP then the remainder of the climb must be allocated to this leg. For example if you estimated you would be at 5000 over Robson and you are climbing to 8500 then this leg is for a climb from 5000 to 8500. Use the charts in your POH to determine: 1.

Time to climb

2.

Fuel to climb

3.

Distance to climb

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The only complication is allowing for wind. It is critical for you to realize that wind will NOT AFFECT time or fuel to climb, it only affects distance. Don’t move on until you have reasoned that claim out and are convinced that it is true. It is necessary to allow for wind in the climb or your flight planning will not be accurate. Wind changes as you climb so it can be quite different at 5000 than at 8500. In addition true and indicated airspeeds change as you climb in accordance with the climb charts (previously covered.) We need a rule of thumb to determine distance covered in a climb. For normally aspirated piston airplanes such as the C-172P and Travelair rate of climb drops off quickly with altitude so that mid-time in a climb happens at higher than mid-altitude. You should therefore determine your groundspeed at 2/3 of the way up to your cruise altitude and calculate distance covered using that value (remember you know the climb time.) Using the example of climbing from 4500 to 8500 the difference is 4000 feet and 2/3 of that is 2700, so determine GS at 7200 (4500 + 2700.) Once you know this GS, and given the time to climb, use your CR to calculate distance. In turbo-charged and turbo-prop airplanes climb rate does not drop off as quickly so determine GS halfway up to cruise altitude and calculate distance covered based on that (in the example, calculate GS at 6500.) Once you know how many miles past SHP it is to TOC use your ruler and mark TOC on the map and then measure the distance from TOC to the next waypoint (mystery lake in the navlog shown above.) This distance is used on the next leg. In the example navlog the total distance from Robson to mystery lake is 50NM, so the distance from TOC to mystery lake is 37NM. When using the ENL enter the altitude that is 2/3 or ½ your cruise altitude with wind and temperature for that altitude. Initially enter the distance from your time to climb chart, but once the ENL calculates groundspeed and time you will have to increase or decrease the distance until the time and fuel match what you determined from the climb chart.

Cruise Legs – Between Enroute Checkpoints The first cruise leg starts at TOC and goes to the next checkpoint. Subsequent legs run in straight lines from checkpoint to checkpoint until the last checkpoint. The last checkpoint could be the destination airport Page 179


(circuit joining point) or in the case of an IFR navlog it is usually the location where the IFR approach will begin. Flights should be broken into manageable legs. A 1000 mile VFR leg is hard to fly and is subject to problems covered previously in map theory. Even transoceanic airliners fly from checkpoint to checkpoint over the ocean so don’t be afraid to break your trip into manageable legs. On the other hand don’t make the legs too short or your nav-log will be so extensive it will over-load the airplane. Use your ruler to measure the length of each leg in nautical miles. Use a protractor to measure the true track (covered below.) When planning with an LO or HI chart read the distance and magnetic track directly from the chart and use the CR to determine the true track. For example the LO1 chart below shows the track from CG to WHATS on R119 is 301°M and the distance is 41 NM. Variation is 18°E (the dashed line just south of WHATS.)

To get the true track use the back-side of your CR. Set the magnetic track (301M) opposite variation (18E) as shown below. The true track (TC) is 319.

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IFR checkpoints are VORs, NDBs, or intersections; every location where your track changes is a checkpoint (WHATS is an intersection.) VFR checkpoints should be distinct geographical features you can positively identify yourself over and thereby confirm you are on course (and start the next leg accurately.) Towns, airport, small lakes, etc make good checkpoints. Normally true-track changes (at least slightly) over a checkpoint. Draw a straight line with a pencil between each checkpoint. Measure the length of the line with a ruler of the appropriate scale. Measure the true track by aligning your protractor to north with a line of longitude near the midpoint of the leg. In cruise TAS speed and fuel flow are in accordance with the cruise performance charts. Be sure to write the power setting and fuel-flow in the proper column for reference. Fill in the actual wind and temperature at your cruising altitude and use your CR to determine GS and true heading based on the TAS. Remember that you will need to determine pressure altitude and or density altitude to determine TAS. Fill in the variation and then calculate the magnetic heading. Remember the old saying: Variation east, magnetic is least. Variation west, magnetic is best. This means that with easterly variation (such as in British Columbia) magnetic heading is always less than true heading. In eastern Canada, where variation is west, magnetic heading is always more than true heading. To avoid any chance of a mistake it is safer to use the back-side of your CR when converting between true and magnetic, as shown in the photo above.

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Use your CR to determine CAS, and then use the calibration chart in the POH to determine IAS. You need this so that you can check in flight that the airplane is performing as planned. Of course you also use the CR to determine time and fuel for the leg.

Selection of Cruising Altitude Many pilots pick their cruising altitude without much rational consideration. Many choose cruise altitudes that are too low, perhaps because the short cross-countries typical of private pilot training are best done at low altitude. In this section we will investigate which altitude is optimum for cruise. To conduct this investigation we will use the Selkirk College electronic-nav-log (ENL). By the end of this section you will understand that there is an optimum cruise altitude and be familiar with the ENL. All airplanes fly faster, for a given amount of fuel flow, at a higher altitude. However, fuel is used climbing to altitude, so there is an altitude above which further climb increases the total time for the flight. The criteria for saying on altitude is “optimum” could be saving time or fuel. Most commercial air operations place a premium on time rather than fuel. The optimum altitude is therefore either: 1.

The altitude that results in the least time for the flight

2.

The altitude that results in the least fuel used for the flight

The factors that determine which altitude is optimum are: 1.

Aircraft type

2.

Power setting

3.

Air temperature and pressure

4.

Weight (aircraft load)

5.

Distance to be flown (length of the flight)

6.

Wind

For piston engine airplanes the benefits of flying at a higher altitude are very minimal in terms of saving fuel. Only on very long flights is any fuel saved at all – so in most cases you can fly at any altitude you wish as far as fuel consumption is concerned. Therefore it is best to decide your cruising altitude based on other factors such as the improved safety of flying higher in a single-engine airplane. Of course it is important to avoid headwinds, so try to avoid climbing into a strong headwind aloft unless safety demands you do so (as it often does in British Columbia.) Climbing to high altitude to pick up a strong tailwind is however always a good idea. In a turbine engine airplane flying at a higher altitude is much more advantageous. The resons will be covered in your aerodynamics course. It is very worthwhile for you to examine the cruise performance

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charts for the King Air, which you have an FIM for, and calculate the specific range foe the airplane at various altitude. You will quickly see that it is much better at high altitude

Top of Descent What goes up must come down, so the saying goes. But with an airplane the pilot has control of when to come down and this is a matter that deserves more thought than it is sometimes given. If descent is started too late then the airplane arrives at the airport too high to land and must circle down, wasting time, or requiring a high descent rate that is uncomfortable for passengers and may cause damage to the engine in some cases. The turbocharged engines typical of working airplanes are quite sensitive to large power reductions. The shock-cooling will damage the engine. Thus professional pilots learn to start descent early enough that a gentle descent with gradual reductions in power can be made. Conversely, pilots of turboprop and jet airplanes can close the throttle without fear of damage to the engine. For these airplanes descent is delayed as long as reasonable in order to take advantage of the better fuel economy at altitude. In single-engine mountain-flying it is particularly unwise to descend early. The terrain is rugged, with few places to land in the event of an engine failure. The ideal descent is usually one that reaches circuit altitude just slightly before joining the circuit. At times it may even be necessary to plan to circle down over the airport, although this should be avoided if possible. The most commonly used descent gradient is 1000 feet every 3 nautical miles. This is used by most jet and turboprop pilots and also works reasonably well in the C-172 and B95. For high performance turbocharged airplanes a gentler gradient such as 1000 feet every 4 nautical miles may be more appropriate. It is important for you to get to know what is best for your airplane. Once you have established the ideal descent gradient designating a top of descent (TOD) is straight forward. To designate a TOD calculate the altitude to be lost in thousands of feet then multiply by 3 (or 4 as the case may be.) Assuming you are planning to join the circuit the altitude to be lost is obtained by subtracting circuit altitude from cruise altitude. If you are planning a straight-in landing then subtract field elevation from cruise altitude. The value should be rounded to the nearest thousand feet. For example if descending from 8500 to join the circuit in Castlegar at 2600 you get 6 thousand feet. Multiply 6 x 3 to get 18 Nautical miles. Your TOD is 18 miles form where? The answer is; from the place you wish to reach circuit altitude. This is likely 3 miles from the airport, so start descent 21 miles out. TOD should be calculated in flight, but need not appear on your navlog.

Contingencies RAC 3.13 requires pilots to allow for contingencies when flight planning. Even if no such regulation existed it would only be prudent to do so. We have already seen that flying at a different altitude than planned affects required fuel. Obviously the wind can be different than forecast. There are a great many factors that can affect your flight. The longer the flight the more likely it is that errors in planning will arise, yet it is the long flights that have the least margin for error.

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If you are headed for a small airport with only one runway is there any chance the runway could be unusable when you arrive there? Of course there is. An airplane could land gear-up while you are enroute, or any number of other things could happen. It is pretty much a guarantee that these things will happen to you a few times in your life. If you don’t leave yourself with some options (exactly what contingencies means) then you will be, as we say, SOL. Often our flights have lots of options built into them. A flight in a C-172 from Castlegar to Boundary Bay can equally well land in Langley, Abbotsford, Delta, etc. So a gear-up on a runway in Boundary Bay is not a circumstance that requires contingency planning. But, you may well have to divert due to weather enroute and wind up flying farther than planned in the process. Contingency time should be allocated for this purpose. Transport Canada has a poster that says in big letters:

That’s Time in Your Tank The point being made is that allocating contingency time means allocating fuel. Simply ask yourself how much extra time you might need for contingencies, then calculate the fuel for that time based on cruise power. It is important to realize that if you actually need to use your contingency fuel you DO NOT have to burn it at the “normal” cruise rate. For example if you are holding (VFR you might be circling while the runway is plowed) you should fly at less than 65% power and thus you would have more contingency time than you indicated on your nav-log. This is where it is nice to have accurate fuel gauges so you can tell when you are reaching the end of your contingency fuel. Most turbo-prop and jet airplanes have reliable fuel gauges, but most small piston airplanes do not. Note that contingency time should not be included in time enroute you file on your flight plan. Filing flight plans is covered later. On the ENL set an amount of contingency time and the ENL allocates the required fuel at the normal cruise power setting. Note that contingency time is NOT included in time enroute.

Approach at Destination For VFR flights your last enroute checkpoint is normally the destination airport, i.e. the point where you join the circuit (if the airport has a published VFR arrival procedure it should be the point where that procedure begins, as for example in Kelowna or Victoria For IFR flights the last enroute checkpoint is usually the IAF (initial approach fix) which is where you start your instrument approach (explained previously.) Therefore time and fuel must be allocated for the approach, and possible missed approach. If your last checkpoint is the beginning of the arrival procedure then you must also allocate time for the arrival as well as the approach (circuit if VFR). You must learn to estimate this time reasonably accurately. A single VFR

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circuit takes about 6 minutes. If you require a low pass and a second circuit before landing the time will double, or more. So apply a suitable estimate for approach and landing time. On VFR flights approach and landing time should be included in the time you file on your flight plan. We will discuss this further later. On IFR flight plans you DO NOT include approach time in the filed time. The ENL does not include approach time in the IFR enroute time but it does in the VFR time enroute.

Checkpoints leading to Alternate Airport All IFR flights require an alternate airport; therefore your nav-log should include a route to it. The process of laying this out is just like the primary flight plan already covered. VFR flights don’t legally require an alternate, and don’t generally need one. But, in some cases it might be wise. For example if you are going to a remote strip where you intend to make a precautionary approach and land (time for the precautionary would be in contingencies) then you will need an alternate in case you determine that you cannot land.

Approach at Alternate Airport This has the same considerations as approach at destination.

Reserve The last row of every nav-log is “Reserve.” There are legal requirements for reserve fuel. Normally this is the value that should go on this line. Extra reserves that you wish to carry should be entered under contingencies on the navlog. Reserve is the amount of fuel that you plan to have left in your tanks when you land. Its purpose is NOT for contingencies – those must be planned and allowed for separately. Reserve is really just for calculation and operational errors. It is almost impossible to set the power to exactly the planned value, and no one ever gets the mixture set 100% perfect, etc. Reserve simply gives you a margin for error. The law requires 30 minutes for day VFR and 45 minutes for night VFR and IFR flights. You are stuck with these values, but realistically reserve should be more on a long flight, especially in a light airplane with inaccurate fuel gauges. An important point to think about for light aircraft operation is in initial loading of the airplane. You might calculate that you should depart with 23 gallons of fuel, but how do you get exactly that amount in the tanks. On a C-172P with standard tanks it would be just a bit more than ½ tanks, but just how much? You can’t really trust the fuel gauges, so you do your best to dip the tanks but there is bound to be some error. Most pilots try to fill the tanks to “at least” the intended amount, but it can be quite difficult. Consequently the reserve you enter on your navlog has considerable error in it. Take note on page 4-17 of the C-172P POH that you can get 4% greater range than the cruise performance charts predict if you lean the mixture to peak EGT. At Selkirk College we don’t normally do that, but it is worth knowing in case an emergency should arise. Here is something to think about: if an adjustment of 50°F in EGT makes a 4% difference in range and this corresponds to about 25rpm change how accurately would you say you normally lean the mixture and what is your percent error? Page 185


Tips for the Electronic Nav-Log Use the TT-Navlog for VFR flights and the MT-Navlog for IFR flights. The only difference between these navlogs is that on the TT-Navlog you enter the true track and the navlog calculates magnetic track, and vice versa on the MT-Navlog. In both cases wind should be entered in true. Use the TAB-KEY to advance through the nav-log, that way you won’t miss anything. Read the “balloons” that pop-up as you tab through the nav-log, these tell you how to fill it in. Wind, temperature, and variation are automatically copied from one row to the next to save the time required for entering these values on each row. However, should a value change you can enter a new value any time and it will propagate throughout the remainder of the navlog. After filling in reserve time the next TAB-STOP is for airport data at the lower left of the nav-log. Typing in this data is much neater than filling it in by hand. When the ENL is completely filled out hide all unused rows in order to avoid clutter – but be sure they contain no data before hiding them.

VFR Map Preparation Techniques We will now go over how to prepare your VNC map for a VFR cross country flight. Various lines and markings are required on the map. The map preparation technique describe here is for DR cross countries. Later we will discuss mountain cross countries, specifically “valley crawling” which is a pilotage type of navigation. For pilotage navigation there is no need to draw drift lines as described here. Locate the departure and destination airports on your VNC. If you aren’t sure which VNC you need lookup the airport in the CFS where the REF section tells you which VNC and WAC chart the airport is on, as well as which LO chart if you are IFR. Locate a suitable SHP, taking into account the factors discussed above. If the flight is in the mountains, or there is restricted airspace near the destination locate a descent point (DP.) Descent points are discussed in detail later under the topic of mountain cross countries. If the trip is more than 300 NM choose some intermediate checkpoints so that no leg is longer than 300NM. This reduces convergence to an insignificant factor and allows us to plan each leg as a Rhumb line. You may also find it practical to choose intermediate checkpoints in order to avoid directly over flying restricted airspace, high terrain, etc. Note that if you are planning a very long flight, say 1000NM or more, you will need a large scale planning chart if you wish to establish a Great-circle route. Once you have chosen your route draw straight track lines, starting at the SHP between each pair of checkpoints with the last track line ending at the destination airport (or DP if applicable. See mountain

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flying below for more information about DP.) When a track-line must cross from one side of a VNC or WAC to the other use the procedure described in the next section to draw the line. Once the track lines are drawn make 10NM reference marks along each line, as shown below.

Next, make 10° drift lines at each checkpoint, starting with the SHP. Note that if you have two SHP, as is sometimes the case in mountain flying, the drift lines should start at the second SHP. Make drift lines for each leg with the last set of closing drift lines at the destination airport or DP as the case may be.

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Drawing a Line Across a 2-Sided Chart

VNC charts are printed on two sides. It is therefore often necessary to draw a straight line between two points that are on opposite sides of the chart. In the figure below imagine that you want to fly directly from point A, on the north side of the chart, to point B on the south side.

The procedure, step by step is:

1.

Layout a separate piece of paper over the north chart and mark point A. In addition mark TWO points that are common to both the north and south side of the chart; these are points D and E.

2.

Position the paper on the common points on the south side of the chart, as shown above.

3.

Draw the straight line from point B to point A on the separate paper.

4.

Mark a point C on the straight line on the south chart that is common to the north chart.

5.

Draw the line from point C to point A on the north chart (not shown in the diagram.)

Measuring Track and Distance

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As you can see it only takes a few minutes to prepare the map for a VFR cross country. Once the map is prepared you are ready to start filling in the navlog. You will of course need to measure the true track and length of each leg. Measure the length of each leg, using an ICAO ruler, and enter it on your navlog. Then measure the true track by placing your protractor at the midpoint of each leg. (Remember the theory of convergence, covered previously, where you learned that at the midpoint of each leg a Great-circle track and Rhumb line are equal.) You navlog should now have all the required information. Simply proceed as already covered to fill in the rest of the data and you will be ready to go.

Filling in a Flight Plan Form Instructions for filling in the Transport Canada flight plan form are in the Aeronautical Information Manual (AIM) section RAC 3.15 and 3.16. You should also read RAC 3.6 to 3.14 for an overview of the purpose and procedures relating to the use of flight plans in Canada. In this section I will comment on a few common errors or oversights in filling out flight plans. It is assumed that you understand the basics as described in RAC 3.15 and 3.16 It is quite common when filling a VFR flight plan to include an intermediate stop. Normally this is not permitted IFR, although it can be done if the IFR flight is in uncontrolled airspace. The rules regarding this are in RAC 3.10. Two points that seem to be missed by many pilots are that the intermediate stop is indicated in the route section of the flight plan in the form shown below. And the total duration of the flight must include the intermediate stop. I have noticed that many pilots who lack experience in long trips vastly underestimate the time required for an intermediate stop. A fuel stop can only be completed in ½ an hour if everything is precisely arranged and organized. A more typical fuel stop takes 45 minutes to an hour. So, allow sufficient time. Pay particular attention to the rules for filing changes to altitude and true airspeed. This is covered in RAC 3.16.6. On many of the flight plans assigned in this course you will change cruise altitude and consequently cruise speed. You are expected to know how to record this properly on the flight plan form. A common mistake is to put arrows or similar symbols in the route section. This is NOT acceptable. Read RAC 3.16.6 carefully and follow the prescribed format. Also, see the examples provided at the end of the section. In the Canadian format no symbols or words are required between checkpoints when the route is direct. If the route in an airway you should name the airway. It is as simple as that, so don’t make it complicated by adding anything else.

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The sample flight plan shown to the left shows an intermediate stop of one hour and thirty minutes in CZGF. Note the format. The flight plan also shows the proper format for filling speed and altitude. Please take note. The time enroute is 3 hours and 40 minutes which is from the time the flight plan is opened until it is to be closed. In this case just before takeoff until just after landing.

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The sample to the left shows how to format a speed and altitude change. At BUICK the airplane will speed up to 160 KTAS and climb to 6000 feet. The time enroute in this case is from takeoff at CYXX to the YCD beacon, which is the IAF for the approach.

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Chapter 9 Mountain Cross Country There is an entire section in your FTM/IPM on mountain flying that you must read. In this text I will only make some remarks about the considerations for laying out a navlog and filing a flight plan for a VFR mountain cross-country. By far the most important aspect of mountain flying is selecting an appropriate route and determining that the weather is adequate for the flight. This is discussed in the FTM/IPM and not repeated here.

DR vs. Pilotage in Mountain Flying Near the beginning of this text I stated that DR is a more sophisticated type of navigation than pilotage. Pilotage takes a lot of effort and frequently results in a somewhat winding route. But by far the greatest limitation of pilotage is that it simply cannot be done without numerous easy to identify geographic features. In the mountains distinctive, rivers, and valleys, peaks, roads, railways, etc. provide the ideal circumstance for pilotage navigation. When the ceilings are low VFR pilots must fly in the valleys, if they are to fly at all, and in such cases pilotage becomes the only viable form of navigation. Even when ceilings are high and DR is used it is very easy to slip back and forth between DR and pilotage due to the numerous easy to identify geographic features. Any experienced mountain pilot soon becomes a master of pilotage. But it is important not to turn your back totally on DR. The ideal form of mountain navigation weaves pilotage and DR into a seamless, almost effortless, procedure.

Good-weather Mountain Cross-country As mentioned in the FTM/IPM, when the weather is good enough to climb above the mountain tops and fly in a straight-line there is really no significant difference between mountain flying and any other type of flying. In this situation you should prepare your navlog pretty much as I have described previously. The primary complication you will face is planning a departure and an arrival route that allows you to leave and arrive at the airport, which is almost always at the bottom of a valley, without conflicting with any mountains.

Set Heading Point(s) in the Mountains SHP is defined as the first fixed point on a DR cross-country. By definition the enroute legs commence after the SHP and the implication is that pilotage is used prior to the SHP and DR is used after it. In the mountains you will often be below the tops of the mountains when you pass the SHP and as such you may be unable to fly the calculated heading. What should we do?


The first tip is pretty obvious. Try to pick an SHP such that the subsequent track follows a valley so that you can climb on the pp-leg as planned. What if you can’t do that though? Again the answer is pretty obvious. You will have to use pilotage until you clear the top of the mountains. In this case we recommend that you plan a second SHP from which you can begin DR. It is always much more accurate to begin DR from a specific SHP. Sometimes pilots skip the procedure of selecting the second SHP, but this is usually because they are overcommitted to pilotage. In other words, they are not going to do DR at all. I recommend this only for relatively short trips on familiar routes. But, if the route is less familiar and you want to achieve efficient navigation always have a specific SHP and use DR. This frequently means having two SHPs.

Descent Point in the Mountains Normal procedure is to plan the enroute legs so that the last leg ends at the destination airport. The pilot must determine a top of descent point (TOD) at which to begin down for landing. This is discussed below under Enroute Navigation Skills. But, TOD is a completely different concept than descent point (DP) which we are discussing here. DP is primarily of concern in the mountains where it is quite common that terrain prevents descent to circuit altitude when desired. Occasionally in non-mountainous areas the same problem may arise due to restricted airspace. When the route directly to an airport crosses high terrain you should always check that a descent to the airport will be possible. If it is not possible then on alternative is simply to circle down over the airport, and time for this should be allocated, normally under approach and landing on the navlog. But, circling down over the airport is seldom the most efficient way to handle the situation. Take the example of an airplane arriving in Castlegar from Vancouver. The straight-line route runs over the ridge just west of the airport and would leave the airplane at 7000’ or so within a mile of two of the airport. Pilots almost naturally divert slightly off this straight-line route and descend along the Arrow Lake. In short they plan the flight NOT to CYCG but to a DP at Deer Park. In all mountain cross-countries be sure to examine the route and determine if you need a DP.

Poor Weather Mountain Cross-country (Valley Crawl) Let us now assume that ceilings are below the mountain tops (or within 1000’ of the mountain tops.) In this case Pilotage, not DR, is the dominant navigation technique. These valley cross-countries are sometimes called “valley crawls.” The creation of a navlog, as described so far, is based on the presumption of DR. When we open the flight plan, as we have recommended for departure and arrival, we are really saying that pilotage will be used in these phases of flight. Now we are saying that pilotage is to be used throughout the flight, so the navlog must be very open. On a valley crawl legs should be grouped (that’s what open means.) Heading obviously changes every few minutes as the pilot follows a valley. Having a leg for every change in heading is totally unrealistic. Instead

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the legs are chosen based only on major changes of direction and or between major checkpoints such as large towns, lakes, etc. This is a very open format. The track in this case requires a bit more consideration than usual. A single track from departure direct to destination usually doesn’t provide enough reference, while a separate leg for each little twist and turn is too cumbersome to plan and to execute. We need something in between. As a practical example, a valley crawl from Castlegar to Grand Forks could be planned as three legs: One from the Keenleyside dam to Renata, one south to Christina and one east to Grand Forks. The usual method of measuring the length of a leg, by using a ruler, will not give an accurate distance. You must learn to estimate the actual distance flown due to weaving around the snaking turns of the valley. You should certainly start by measuring the straight-line distance from the beginning of the leg to the end, with a ruler, but then you must add an estimated amount to allow for the turns of the valley. There is NO SENSE calculating wind drift, drift angle, and heading for the leg. Indeed you can only estimate the average track (because it changes continually as you fly.) Don’t worry about drift, your eyes will keep you on track using pilotage. There is no need to put drift lines on the map. Groundspeed must be estimated in order to calculate time and fuel for the flight. Based on your average track and the wind you can estimate the average groundspeed. The hard part is often determining what the wind will actually be. FD forecasts are of limited applicability. Reported ground winds and winds aloft are obviously used to estimate wind at your chosen cruise altitude. Keep in mind that under the circumstances of a valley crawl you often have to change cruise altitude frequently enroute. Wind normally is funneled to follow the valley, so your main task is to guess whether there will be a headwind or tailwind and how strong it will be; if in doubt always estimate low for tailwinds and high for headwinds. In the wind column of the navlog write only the headwind or tailwind estimate – e.g. +10 or -5. You will be given several assignments to plan valley cross-countries to develop the skills described above. It is crucial that you learn to efficiently open your flight planning so that you can prepare the navlog in only a few minutes, because by far the most important part of valley crawl planning has nothing to do with making a navlog. The most important aspect of valley crawl planning is route analysis. You must examine the route looking for difficult points, such as passes, and most important of all, looking for alternate routes. In the discussion about diversions later in this text it is pointed out that a safe diversion in the mountains is only possible if you have planned for it in advance. Given that diversions are very common you must have every safe route option in your mind before you go on a flight. It is very common that the shortest route for a mountain flight is not the one with the lowest terrain. There is nothing wrong with planning the shorter route, but if you run into low ceilings and decide to divert to the longer lower route you want to have figured out ahead of time that you have enough fuel for that. You must know that if you don’t have enough fuel for a particular diversion option, where you will make fuel stops, etc. Don’t set out on a mountain cross country in marginal weather without all the above thoughts and options sorted out in your mind.

In-flight Valley Navigation Procedures Once airborne, housekeeping becomes very important. Since the heading information is only approximate, considerable attention must be paid to map reading as the pilot follows – although rarely Page 195


accurately maintains – the intended track. This makes it all too easy to lose track of time and over fly a turning point. While it might be difficult to imagine a pilot missing the turn at Christina (for Grand Forks) and picking up the road to Republic, some 20 miles south, it is not impossible and it is really easy, when following Highway 3 west from Cranbrook, to miss the turn at Yahk and continue on Highway 95, going south-east down to Copeland. This is not a complete disaster but in marginal VFR conditions it is very disconcerting and re-orientation can take several minutes. There is little need to recalculate headings, since that information is only approximate to start with. It is important, however, to update the ground speed information – again, in order to monitor the progress along the track. If the leg is long enough to warrant a couple of 10-mile marks then these can be used just as they are on a regular navigation leg. More often however, the legs are barely long enough to justify one 10-mile mark so it is more appropriate to wait until reaching the next turning point, where the pilot can either compare the ETE to the actual time enroute (ATE) in order to derive a time differential or simply divide the distance by the ATE for a ground speed. In either case, it is important to remember that a headwind component on one leg can easily become a tailwind component on the next leg: With winds aloft out of the north, a tailwind on a leg headed south east could well become a head wind if the valley makes a turn around to the north east. Situational awareness is always critical while valley crawling. There is a full section giving advice on valley flying in the FTM/IPM.

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Chapter 10 Time Saving Flight Planning Techniques In all that we have done so far we have planned flights by breaking flights into climb, cruise and descent legs. We have simplified our task by opening the flight plans, and this is an important time saving procedure. There are some other commonly used “short cuts” to flight planning that I would like you to be aware of.

Block Flight Planning Block flight planning is commonly used to get a quick estimate, usually for the purpose of quoting a charter. The company determines an average distance and fuel used for the airplane each hour. Often the accuracy is improved by establishing a distance and fuel for the first hour and then a different figure for subsequent hours. For example an airplane may use 500lb of fuel and cover 180 NM in the first hour and burn 300lb while covering 220NM in subsequent hours. The airplane charters for $2000 per hour. Assume a client calls for a 600NM charter, what would you quote? The calculation is straight forward: Hour one covers 180NM. Subsequent 420NM require 1.9 hours (420/220.) Total trip time is therefore 2.9 hours, which will cost $5800.

If the customer says, “yes” to your quote you quickly file the flight plan for 3.9 hours and have 1070 lb of fuel, plus contingencies and reserve loaded. The fuel is calculated as 500 + 1.9 x 300.

Block flight planning is only safe when the airplane always flies at essentially the same cruise altitude and wind is not a factor. This is clearly a dangerous assumption, so block planning must be used with great consideration.

Climb Penalty Planning Pilots, being rather lazy, find it onerous to lookup the time fuel and distance to climb to cruise altitude. Some people try to avoid this task by developing rules of thumb. An important point I must make before explaining how this is done is that it doesn’t work. In other words, climb penalty planning is a myth. Still, it is so commonly used that you need to know the concept if for no other reason than so you can see its limitations. (Actually, we will conclude that penalties work in the right circumstance.) Climb penalty planning starts by saying, “wouldn’t it be easy to flight plan if the departure airport was on a mountain exactly at the cruise altitude for the trip. This imaginary situation is shown in the picture below:


If the above situation actually existed there would be no need to plan a climb leg. The airplane would already be at cruise at the moment of liftoff. The next step in climb penalty planning is to ask what the difference in time and fuel for the trip would be in the following situation:

Obviously the airplane in this situation must climb from the departure runway to the cruise altitude. Taking a C-172P as an example, it will climb at 85KIAS (TAS is higher) and then cruise at about 105KTAS (the exact value depends on the cruise altitude.) This airplane will “fall behind” the other airplane at about 15 knots. Obviously the trip will take longer this way. Similarly it will use more fuel, due to the higher rate of fuel flow in the climb, and the slightly longer flight time.

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The idea behind climb penalty planning is simply to determine the difference between the above cases and then add that onto case I as a penalty. We can do this quite easily using the ENL.

First examine the third leg of the above navlog. It shows a cruise leg of 100NM. The airplane is level for this entire leg, so it corresponds to the part I diagram above. The leg requires 55 minutes and consumes 6.6 gallons. Next examine the first two legs of the above navlog. Together they also cover a distance of 100 NM, but the airplane climbs from sea level to the cruise altitude of 6000 feet. This takes 58 minutes and 7.9 gallons are consumed. This corresponds to the part II diagram above. The time penalty is obviously 3 minutes per 6000 feet, i.e. 30 seconds per thousand feet. The fuel penalty is 1.3 gallons per 6000 feet, which is a bit less than ¼ gallon per thousand feet. To use the penalties for a C-172P simply plan the trip as though the entire flight was in cruise, i.e. as though the part I diagram applies. Once you have done this add a penalty of 30 seconds and .25 gallons for each thousand feet the cruise altitude is above the takeoff altitude. Repeat the above ENL analysis for the B95 and determine the climb penalties for that airplane. At the beginning of this section I said that the real problem with climb penalties is that they don’t work. Can you spot the flaw in the logic behind this procedure? Think about it before reading the next paragraph. In our earlier cruise altitude analysis we learned that depending on the length of a trip there not only is no penalty for climbing, there is a penalty for not climbing. Take the airplane on the 500NM cross country on page Error! Bookmark not defined. a pilot planning this flight for cruise at 9500’ and then adding a penalty would be completely mislead. Climb penalties are only applicable to flights at relatively low altitudes and over relatively short distances. In this case they do reflect the penalty due to climbing that we already discovered on page Error! Bookmark not defined..

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Chapter 11 Enroute Navigation Skills This section covers several navigation skills that you will need to develop and apply in flight. The primary emphasis in this course is on preflight planning, most of the in-flight skills are developed in Avia 100 and 200, but there are some things you should keep in mind.

Map Reading Its pretty obvious that a fundamental skill in navigating VFR is the ability to interpret a VNC chart and locate the corresponding geographic features on the ground. The first principle of map reading is work from map to ground, NOT the other way around. In other words you locate a geographic feature on the map and then look out the window until you spot the same feature on the ground. You do NOT spend time with your eyes down on the map trying to find some feature, such as a small lake or road that you have spotted out the window. The latter procedure results in too much time with eyes in the cockpit. Good airmanship is to have your eyes out the window 99% of the time. You must learn which features will be distinctive “out the window” and which won’t. on the map certain things such as VORs, NDBs, towers, runways, small town, and power lines are quite distinctive, but out the window they are nearly impossible to see. There are exceptions of course. For example power lines over mountain ridges can be quite easy to see because a wide swath of trees is cut down along the line. And radio towers are very easy to see at night. The specifics of night cross countries are discussed in your FTM/IPM and are covered in Avia 201; they will not be covered further here. The best procedure is to choose four or five geographic points on your map and then look out the window until you spot them. These could be a town, a river, a road, and a mountain or valley. Once you have this “list” of items gleaned from the map you scan the ground until you locate the corresponding locations. There are of course lots of towns, rivers, roads and mountains in the world so how do you tell one from another? The key here is to analyze the map and develop a mental image of the distinctive characteristics of the ones you are looking for. For example does the town have a river running though it? How many roads run in and out? And is there a nearby mountain? Try to have at least three distinctive features that will distinguish the location you are looking for from others. These features can be anything, as described above, as well as relative position, size, etc. A common mistake is to choose geographic points that are too close to the airplane. In flight you can see a long way and you should take advantage of that. It is much easier to locate a geographic point that is 5 or 10 miles ahead rather than one directly below you (the airplane doesn’t have a glass floor.) You can often see large geographic features, such as distinctive mountains, lakes and rivers, 30 or more miles away. Doing so reduces a lot of navigation effort, so it is highly recommended.


Another frequent mistake is becoming too obsessive about spotting a particular geographic point. For example you may be looking for a small town but not seeing it. Some pilots will keep looking and looking and looking for this town until they are completely lost. This is due to a lack of time awareness, discussed next.

Time Awareness When you choose a geographic point on your map that you will be looking for a critical thing to do is estimate roughly how long it will take until you reach the point. To do this simply be aware of how many miles per minute (roughly) you are covering. Most airplanes cover at least 2 miles per minute, and many go much faster than that. Therefore a geographic point 6 miles ahead will be beneath you in 3 minutes. If you haven’t spotted it by then you’ve missed it. It isn’t critical to identify every point, so don’t worry about it. In light of the above, it is important to always be looking for more than one geographic point. Usually three is a good number. If you miss one it won’t really matter. Also, finding one often makes it easier to spot the others. Most importantly, be aware of time passing. If logic says you are past a checkpoint then forget it, choose another one and look for that. Failure to follow this advice is what will get you lost.

Reorienting if Lost The first question you must ask is; am I really lost? As a new pilot you may feel lost if you miss one checkpoint, but you really aren’t. This was mentioned above. Don’t panic. As long as you fly a straight-line you can always find your way back by simply “doing a 180.” But it is important that you fly the specific heading on your navlog. The best way to get lost is to wander around on random headings that are not recorded. As long as you are flying one heading (as opposed to wandering) you can do a 180 and go back. Of course if you have a working GPS you can read the latitude and longitude and immediately locate yourself on the VNC. So, we will assume you don’t have such equipment. If you are truly “lost” stay calm and keep your wits about you (which means you mustn’t panic.) When you think about it you really aren’t “totally lost.” You can state your location in a hierarchy such as that you are in Canada, B.C., Southern B.C. east of Vancouver, and so on. You probably know where you are within a few miles tolerance. You could draw a circle on the map and say, “I am somewhere in here.” From this known area of probability there are several things you can do: If you have been flying a steady heading you can simply reverse it and go back to where you came from. Remember to write down the time you turn around so you can estimate how long it will take to get back to the starting point. Your previously recorded departure time will give you all the information you need. Lucky you always record these things, right? If the weather is suitable, climb to a higher altitude so you can see farther. If you can climb high enough to get ATC on the radio you will be able to get radar or DF assistance from them. Radar is available in most of southern Canada, but if you happen to be lost in the far north there is also the defense radar system. The procedure for using this in the event of an emergency is covered in section F of your CFS. Page 204


If you have been wandering around, which got you lost, consider using the navigation technique called landfall, which is described below. It is almost always possible to use a landfall to reorient yourself. If your desired destination is not on an extended geographic feature suitable for landfall then pick an interim destination from which you will be able to continue on. In the prairies most small towns have the town name written on their grain elevator. If you fly any direction you will come across a road within a short time. Follow it to a town and as you fly by you can read the name on the elevator to identify your location. Keep track of your fuel. If you brought lots of reserve you will be fine, but if fuel gets low and you are still lost you may have to do a precautionary approach. Much more likely however is that you will reorient yourself and be able to continue your flight. But be sure to recalculate your reserves. If they have shrunk too low divert to another location and refuel. Most fuel starvation incidents follow getting lost.

Navlog keeping On your navlog you must record the takeoff time and time past each checkpoint enroute. You should also record ETA revised ETA for each checkpoint. These are standard procedures applicable to any log keeping exercise. In addition your company may require many other pieces of information be recorded. On the Selkirk College navlog we write the takeoff time in the designated location just before takeoff. Once clear of the departure airport we then write down the ETA and Fuel Expiry time in the designated locations. We then fill out the ETA column so that we have the ETA for each checkpoint. The final checkpoint ETA should match the previously calculated destination ETA. If it does not then an adding mistake has been made, which you must locate and correct. Selkirk College navlog keeping involves writing down the time we pass each checkpoint enroute in the ATA column. The ATA should be quite close to the ETA previously filled in. At a glance you will be able to see that you are ahead of or behind schedule. If the groundspeed is revised pencil the corrected value over the value on the navlog, then enter a revised ETA in the designated column. TIP: it is really quite rare for the winds aloft forecast to be wrong by more than 5 knots. This amounts to saying that you normally will have a groundspeed within 5 knots of the planned value. If your calculated groundspeed is substantially different than the flight planned value you should recheck your calculations before jumping to any conclusions. When the wind is substantially different than the forecast there is usually evidence such as turbulence or un-forecast storm activity. TIP: when doing a groundspeed check your calculations are subject to round-off error. For example, you measure a distance of 11NM and then measure a time of 4 minutes. Based on this your CR tells you that the groundspeed is ____ Kts. Ask yourself what tolerance you would apply to this value. Consider this before reading the next paragraph. The groundspeed according to your CR is 165 kts. But the distance is rounded off to the nearest nautical mile and the time is rounded off to the nearest minute. This amounts to saying that the actual distance is

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between 10.4 and 11.4 and the time is between 3:31 and 4:29. Using these values your groundspeed could be anywhere between 149 and 196 kts! (Check these values for yourself with a CR.) That is a very large spread of “correct” values. If your navlog predicted a groundspeed of 150 knots should you revise your ETA or not? The answer is that you don’t have an accurate enough groundspeed to decide. To make an accurate groundspeed check you need more accurate data. The best you can usually do is measure distance plus or minus ½ nautical mile Even after you do this you will find it difficult specify the precise moment you pass the checkpoint, which adds another error bringing distance tolerance to at least 1 NM. You can use a stopwatch to get a more accurate time value, but it is still difficult to achieve an accuracy right down to the second (see previous point.) Consequently, if you want a groundspeed check accurate to the nearest knot you would have to fly a groundspeed check of at least one hour (60 minutes.) Put another way, a six minute groundspeed check is at best accurate to plus or minus 10 knots. And a 3 minute groundspeed check is accurate plus or minus 20 knots, which is to say just about useless. So, make sure you use fairly long groundspeed checks (10 to 15 minutes minimum), and know the tolerance of their accuracy (4 or 5 knots at best.) If the obtained value lies within the tolerance of your flight planned speed it is usually wise to take this as confirmation of the navlog and make no revision to your ETA.

Top of Descent At some point you must start a descent from your cruise altitude so that when you reach the destination airport you are at the desired altitude. This is the top of descent point (TOD.) Choosing it wisely is important. A lot of VFR pilots are in the habit of descending quite early. If you are approaching a major airport with a lot of traffic, and in an area with lots of good forced approach sites, it might be wise to descend to circuit altitude 10 miles before the airport (I am thinking about single engine airplanes here.) But in more rugged terrain you want to reach circuit altitude only one or two miles prior to joining the circuit, in order to keep as many safety options open as possible. On the other hand, you don’t want to descend too late, if you reach the airport well above circuit altitude you will have to circle down (which wastes time and fuel) or will dive (which is uncomfortable for passengers and you.) Most pilots plan descents based on a certain gradient. Three miles per thousand feet is the most common. If you are flying a turbo-charged piston airplane it might be better to use four miles per thousand feet. Simply calculate how may thousand feet you need to descend and multiply by three (or four) then start your descent that number of miles from the location you which to reach circuit altitude.

Diversions A diversion means changing your route and or destination while in flight. Diversions are very very common occurrences in both IFR and VFR flight. IFR flights routinely divert around areas of bad weather. The specific techniques for this however will be deferred to Avia 260 Page 206


VFR flights also often divert around areas of bad weather. It is not always necessary to change destination when bad weather is encountered, frequently you can skirt the area of poor weather and re-intercept the route beyond the area affected. But you must keep track of time so that you don’t run low on fuel. When diverting around weather you are by definition using your contingency fuel, so as long as your navlog shows that you have lots of contingency fuel you are fine. But if you have not allowed contingency fuel then you will have to change your destination in order to refuel. Transport Canada has established a specific diversion exercise that you must demonstrate on the commercial pilot flight test. It is important to realize that this is only an exercise. It actually bears almost no resemblance to 99% of real life diversion scenarios. On the flight test exercise you are required to draw a free-hand line to a designated destination then estimate the heading and distance without using a protractor or a ruler. You must then calculate (estimate) the time enroute in your head without a flight computer. This is a great exercise in mental approximation but it is important for you to realize that if you are actually doing a diversion there is nothing wrong with using a ruler, or a calculator. To meet the Transport Canada diversion challenge most pilots estimate the distance by using the minute marks on the VNC’s lines of longitude as a scale. Your instructor will show you how to do this if you haven’t done it before. In the real world, just use a ruler if you have one. To estimate the track to the destination you can just “eye-ball-it” or use a VOR rose to help you be a bit more accurate. You will be surprised how closely you can eye-ball-it with a bit of practice. This is however a skill that requires practice. The best thing to do is estimate all tracks before putting a protractor on them. To estimate the time enroute if you don’t have a CR computer there are numerous mathematical tricks. These are laid out on the ProfessionalPilot.ca website in the miscellaneous section. Anyone can do it, it just takes a bit of practice, and it is well worth the effort. When diverting in the mountains, on a valley crawl, usually means taking a totally different route. The secret to success is in knowing all the routing options before you takeoff. Scanning the map looking for an alternate route once you have run into poor weather is a recipe for disaster. I am sure than many of the pilots who have killed themselves in the mountains (and there are a lot of them) did so when they had to divert but were unprepared to do so. If you run into bad weather in the mountains and have to divert then there should only be two possibilities. You either divert to an alternate route that you have previously analyzed and planned, or you do a 180 back to the last suitable airport and land there until you get organized to go on. NEVER plan a substantial diversion in-flight in the mountains.

Position Reports and Amending Flight Plan No one likes to think about having an accident enroute and not making it to destination, but this is a possibility. To facilitate quickly locating you in the event you do not arrive at destination you should file position reports frequently during your flight. An even better idea is to avail yourself of radar surveillance enroute. Radar surveillance is covered in the AIM RAC 5.7. The contents of a VFR position report are listed on the back cover of your CFS. Ideally position reports should be made about every half hour on a cross country. In the mountains there are often limited opportunities to make position reports, especially on valley crawl trips. In such cases the Page 207


best advice is to make every position report that you can. This sometimes means making two reports only 10 minutes apart and then other times an hour or more might pass due to lack of ground stations. It is vital to realize that when you make a position report the information is recorded, for use if you don’t arrive at your destination, but it DOES NOT update your flight plan. Many pilots misunderstand this fact. For example, if you are falling behind schedule and will arrive 45 minutes late, if you file a position report in which you give an ETA for your destination that correctly predicts your new arrival time FSS will still initiate a search for you at the original ETA based on your flight plan. To prevent this you must specifically request that your flight plan be amended to your revised ETA.

Hybrid Navigation Procedure – Landfall There is a navigation procedure that falls between pilotage and true DR called “laying a landfall.” This is a technique that goes back centuries to the days of sailing ships. Despite its age it is quite useful at times in modern aviation. Imagine you wish to sail a ship across the ocean from France to Montreal. The ocean currents present the same problem for ship navigation that wind does for pilots. In modern times you would use GPS or Loran-C th to navigate accurately in a straight-line between the ports. But imagine it is the 16 century and no such system exists. If you sail west from France you are most definitely going to hit North America. When you do sailors say they have “made landfall.” But you are probably going to drift so if you aimed directly at the Saint Lawrence there is no way to know if you are north or south of it. The strategy used is to deliberately aim to one side or the other of the intended destination so that when you do make landfall you know for sure which side of the desired point you are on and can follow the coast to your destination. The same technique can be used by pilots. For example if you are in Kelowna and fly east you really cannot miss the Arrow Lake. Once you find the lake you can follow it to Castlegar. The first step is a rough DR (just accurate enough to guarantee you don’t miss the target (Arrow Lake)) the second leg is pilotage (follow Arrow Lake to Castlegar.) Laying a landfall only works if the destination is on an extended geographically distinct feature that you can lay landfall for and be certain you won’t miss. The Arrow Lake meets that criterion. Many airports in the Prairies are along major highways, which can be used the same way, other towns are on railway tracks, and so on. If you are going to lay landfall simply estimate a heading that will put you one-way-orthe-other from your intended destination. Once you make landfall use pilotage to find the destination. This technique is often practical on a diversion around poor weather or for reorienting yourself if you get “slightly” lost.

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Chapter 12 Oceanic Flight The full details of oceanic flight are beyond the scope of this course. You will learn more about them in second year. However, two points of navigation, which are usually considered important for oceanic flight, will be covered here. These are the point of no return (PNR) and critical point (CP.) Each of these concepts can be applied to any flight, even a short over land flight in a C-172; but they really don’t make a lot of sense in that context. Still, the mechanics of doing the calculation is the same no matter what type of airplane you fly.

Point of No Return (PNR) Imagine you lift off from New York headed for Paris France. A passenger becomes ill 30 minutes into the flight; do you have enough fuel to return to New York? Obviously you do. But, what if the illness arises four hours into the flight; can you still return to New York? On many of the short flights you have made in C-172 and similar airplanes in your flying career you probably carried enough fuel to fly all the way to destination and then return to departure point. In such a case you never reached a point of no return (PNR.) PNR is simply what the name says, the point beyond which you do not have enough fuel to return to the departure aerodrome. PNR depends on the airplane’s Endurance, Speed, and the wind.

Endurance Eu We will represent endurance with a capital E. E is the amount of time in hours that the airplane can fly. Et is the total endurance to dry tanks. For example a C-172 with standard tanks has 38.9 gallons at takeoff and an endurance of 5:18. It would be very unwise to calculate PNR based on this number however because that would imply proposing to return and land just as fuel runs out – a very scary idea. Eu will represent the useable endurance, which must include at least reserve fuel, and possibly some contingency fuel. For the C-172 with standard tanks we could set the value of Eu at 4:40 for example. If there was no wind the airplane would reach PNR by flying out to half its endurance, or in other word PNR would equal total range divided by two.

Groundspeed GSout and GShome The groundspeed of the airplane is an important factor in determining PNR. We will define GS out as the groundspeed when the airplane is outbound from departure, i.e. enroute to destination. GShome will be the groundspeed after a 180° turn, to come back to the departure point.


We also define engine-out-PNR in which we assume all engines operating prior to the 180° turn and one engine out after the turnaround. I.E. GS home-SE will be based on the engine out performance, but GS out is always based on all engines operating normally.

PNR Formula In zero wind PNR is determined very easily by calculating total range (E x GS) and dividing by two:

PNRzero wind = (Eu x GS) / 2 It is always a good idea to do the above calculation as a first estimate; then use the formula below to account for wind. The result is always a distance LESS than the zero wind distance above. I.E. wind always reduced PNR. For example an airplane with a zero wind GS of 100 Kts and an endurance of 4 hours has a PNR of 4 x 100 / 2 = 200. Now let us consider the formula that accounts for wind:

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If the airplane in the previous example experiences a 20Kt tailwind outbound the PNR will be 4.5 x 120 x 80 / (120+80) = 216Nm. As expected, this is slightly less than the zero wind DPNR. Important: PNR with wind is always less than PNR with no wind. Note that PNR questions will be on the ATPL and IATRA written exams IMPORTANT: if a question asks for engine-out-PNR calculate GSout with all engines operating normally and GShome with one engine inoperative. Note that you can always apply the DPNR formula to any flight but in many cases the PNR is beyond the destination. I.E. the airplane can turn around at any point on the flight and return to departure point. This is good to know; therefore PNR should be routinely calculated and if it is beyond destination – great. Here is the “proof” of the formula. It is not necessary for you to memorize the proof but you should know the first line, i.e. the definition, and the last line. By using only the first line you can find the correct answer from among a selection on a multiple choice exam. Page 213


Critical Point (CP) There is some point on every trip you make where it would take the same amount of time to turn around and return to the departure point or to continue on to destination. This is known as the critical point (CP.) It should be obvious that in zero wind the CP is exactly at the mid-point of the flight. In other words on a 1000 NM flight CP is 500 NM. But CP will move into the wind. I.E. if there is a tailwind you will reach CP before the mid-point or if there is a headwind you will reach CP after the midpoint – see if you can visualize why this is so. CP can be calculated for all engines operating normally and also for engine-inoperative. In the later case the CP represents the, on one engine, to return to base or continue to destination IMPORTANT: when calculating CP always use the speed as it will be after the CP. Thus, if you are asked for the single-engine CP use single engine speeds, if asked for all engines CP use all engine speeds – NEVER mix speeds in a CP calculation (this is different than a PNR calculation.) The formula for CP is given in the diagram below:

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Effect of Tailwind and Headwind on CP In a previous example we flew an airplane with GS of 100 knots in zero wind. On a 400Nm flight zero-windCP is 200 Nm. Let’s calculate where CP is with a 20 Knot tailwind outbound. GSon is 120 KT and GSreturn 80KT. Therefore CP = 400 x 80 / (120 + 80) = 160. So, with a tailwind CP comes before the halfway point. Let’s calculate where CP is with a 20 Knot headwind outbound. GS on is 80 KT and GSreturn is 120KT. Therefore CP = 400 x 120 / (120 + 80) = 240. So, with a headwind CP move to beyond halfway point. SUMMARY: CP always moves into the wind.

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Appendix 1– C-172 Interpolation Tables Power setting

___________ feet ___________ temp

RPM

TAS

___________ feet ___________ temp

RPM

TAS

___________ feet ___________ temp

RPM

TAS

___________ feet ___________ temp

RPM

TAS

_______% 65% ______%

Power setting

_______% 65% ______%

Power setting

_______% 65% ______%

Power setting

_______% 65% ______%

________ feet

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________ feet ________ feet

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Appendix 2 - Inbound PDT Practice Sheet In the sheet below fill in the heading you must turn to, or if it is an over-60 write down PT (for procedure turn.)

Bearing to beacon

Desired inbound bearing

150

100

300

280

240

290

040

120

135

165

Heading to steer

In the table below fill in a random selection of bearings to beacon in the first column:

Bearing to beacon

Desired bearing

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Heading to steer

Next fill in desired bearings considering the first column and making the bearing within 60 most of the time.

Finally, fill in the third column

Repeat above MANY times.

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Appendix 3 - Outbound PDT Practice Sheet In the sheet below fill in the heading you must turn to. There is no “over 60” limit for outbound PDTs.

Bearing from beacon

Desired outbound bearing

210

250

340

240

005

320

140

180

280

270

Heading to steer

In the table below fill in a random selection of bearings from beacon in the first column:

Bearing to beacon

Desired bearing

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Heading to steer

Next fill in desired bearings in the second column. There is no 60 degree limit, but normally the desired should be within 180 (to make sense.)

Finally, fill in the third column

Repeat above MANY times.

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Appendix 4 – Definitions

Deviation: The difference between actual magnetic heading and the compass indications. This error is shown on a compass correction card.

Variation: The difference between magnetic track and true track. This due to the magnetic north pole NOT being at the actual north pole. Variation is shown on both IFR and VFR charts as lines of equal variation, known as isogonic lines.

Convergence: Meridians of longitude converge at the north and south poles, as such they are not quite parallel to each other. The angle at which they converge is known as convergence. Convergence is zero at the equator and increases the closer to the pole you fly. An aircraft flying along a Great Circle route much change heading to compensate for convergence.

Great Circle: A line on the surface of the earth that when extended completely encircles the earth and has its center coincident with the earths center. Such a line is the shortest distance along the surface of the earth between any two points on the line.

Rhumb Line: A line on the surface of the earth between two points such that the true track along the line is constant. A Rhumb Line is only coincident with a great circle if it is also a Meridian, or the equator. All other Rhumb lines vary from the Great Circle (see above definition.) Rhumb Lines are popular with pilots because you can fly a constant heading rather than changing headins as you would on a Great Circle.

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Navigation for Profesional Pilots

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