Aircraft Electric & Electronics

Aircraft Electrical & Electronic Systems

K.N.S Acharya

© 2010 Infosys Technologies Limited © 2010 Infosys Technologies Limited

Agenda: Aircraft systems – 1. Avionic Systems • • •

Navigation System, Flight deck and cockpit systems Communication System

2. Flight Control System, 3. Aircraft Electrical System

© 2010 Infosys Technologies Limited

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What is Avionics? • Avionics is actually a combination of Aviation & Electronics. • Represents the field of technology that encompasses the electronic equipment and systems that are used on aircraft and aircraft components. • Avionics equipment is usually thought of as different from electrical or electromechanical aircraft equipment but the lines between electrical systems and avionics systems are not always distinct, especially in the more modern aircraft. • Supports the goal of helping flight crews get safely from point to point. • Avionics helps pilots with their responsibilities in the cockpit to • Aviate (Tracking and Controlling Aircraft Pitch, roll and yaw) • Navigate (track position, way point estimates, deviation from desired course, avoiding collision with obstacles, in all weather conditions) • Communicate (communicate flight progress with others who need to know – other crew members, ATC, other aircraft, Flight Service Stations and airlines).


What are the functions of Avionics? • Function of Avionics Systems is to receive, compute and display • Navigation data, • sense flight parameters, • correlate information, • consolidate and present information to crew, • support crew by automating functions like flight control and flight management, • enhance safety, • improve flight performance, • permit communication with external elements. • Help crews manage their workload, onboard systems and the flight situation The Goal of avionics is to help the aircraft get from one location to another location in almost any weather condition.


Terminologies used in Avionics • • • • • • • • • • • • • • • • • • •

ADF Automatic Direction Finder NDB – Non directional Beacon VOR - VHF omnidirectional range DME – Distance Measuring Equipment TACAN TACtical Air Navigation VORTAC A special VOR which combines VOR T TCAN RNAV Area Navigation RMI Radio Magnetic Indicator HSI Horizontal Situation Indicator LORAN C Long Range Navigation INS / IRS – Inertial Navigation System / Reference DNS: Doppler Navigation System GPS: Global positioning System ALS: Approach Lighting System VASIS: Visual Slope Indicator System ILS: Instrument Landing System MB: Marker beacon MLS: Microwave landing System DGPS: Differential GPS


20 Popular Avionics Abbreviations

Best way to learn Avionic Systems is using 5 Ws + H 1. What: is the purpose of this system 2. Who is permitted use this system? (Military – Civil Etc) 3. Where: is the system situated? Ground , Aircraft or space? 4. Why is this system Good or Bad? 5. When: was the system certified for use in avionics & Future? 6. How: does this system function?

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Aircraft Navigation Systems • Finding the way from one place to another is called NAVIGATION. • Moving of an aircraft from one point to another is the most important part for any kind of mission. Plotting on the paper or on the map a course towards a specific area of the earth , in the past, used to be a task assigned to a specialized member of the aircraft's crew such a navigator. Such a task was quite complicated and not always accurate. Since it depended on the observation , using simple maps and geometrical instruments for calculations. • Today, aerial navigation has become an art which nears to perfection. Both external Navaids (Navigational Aids) and on-board systems help navigate any aircraft over thousand of miles with such accuracy that could only be imagined a few decades ago.


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Methods of Navigation The following are the main methods of air navigation. There are: 1. Pilotage , 2. Dead Reckoning , 3. Radio. 4. Celestial Navigation 5. Satellite Navigation

1. Pilotage or Piloting: ( Based on Visual Landmarks) is the most common method of air navigation. This method, the pilot keeps on course by following a series of landmarks on the ground. Usually before take-off, pilot will making pre-flight planning , the pilot will draws a line on the aeronautical map to indicate the desired course. Pilot will note various landmarks , such as highways , railroad tracks, rivers , bridges . As the pilot flies over each of landmark , pilot will checks it off on the chart or map. If the plane does not pass directly over the landmark , the pilot will know that he has to correct the course.


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Dead Reckoning • 2. Dead Reckoning is the primary navigation method used in the early days of flying. It is the method on which Lindberg relied on his first trans-Atlantic flight. A pilot used this method when flying over large bodies of water, forest, deserts. It demands more skill and experience than pilotage does. It is based on time, distance, and direction only. • The pilot must know the distance from one point to the next, the magnetic heading to be flown. Pilot works on the pre-flight plan chart , pilot plan a route in advance. Pilot calculate the time to know exactly to reach the destination while flying at constant speed. In the air, the pilot uses compass to keep the plane heading in the right direction. Dead reckoning is not always a successful method of navigation because of changing wind direction. It is the fundamental of VFR flight. . © 2010 Infosys Technologies Limited

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DR – Ground Speed estimation


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Radio Navigation, Celestial Navigation, Satellite Navigation • 3. Radio Navigation is used by almost all pilots. Pilots can find out from an aeronautical chart what radio station they should tune to in a particular area. They can then tune their radio navigation equipment to a signal from this station. A needle on the navigation equipment tells the pilot where they are flying to or from station, on course or not • 4. Celestial Navigation: Based on Navigational reference to heavenly bodies, Sun, Moon, planets, stars, satellites etc • 5. Satellite Navigation: Navigation through use of data broadcast by a Satellite (SAT) based transmitter


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Navigating Across Oceans • Pilots have special methods for navigating across oceans. Three commonly used methods are: 1. Inertial Guidance: This system has computer and other special devices that tell pilots where are the plane located. 2.LORAN: Long Range Navigation The plane has equipment for receiving special radio signals sent out continuous from transmitter stations. The signals will indicate the plane location 3.GPS Global Positioning System: is the only system today able to show your exact position on the earth any time, anywhere, and any weather. The system receiver on the aircraft will receives the signals from satellites around the globe.


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Presenting information to Crew - Display system Purpose & Functions Provides situational awareness to the pilot by displaying flight critical information for successful completion of the mission. • Type of Information displayed • Primary flight performance - Airspeed, Attitude, Altitude, Heading, Vertical Speed, Radio Direction & Distance, etc. • Navigation – Flight plan, approach, VOR, moving map, Situation awareness, … • Engines – Torque, Np, Ng, ITT (Turbine inlet temperatures) , Oil Pressure, Oil Temperature, Fuel Pressure, Fuel Flow, Fuel Qty (different tanks) • Aircraft Utility System • Pressurization/ air conditioning • Hydraulic Power • Auxiliary Power unit


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A Typical Flight Deck – A380 Flight deck


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Boeing 777 Flight Deck


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DISPLAY FORMATS – WHY PFD , ND ? Ideas of Orthographic Projection Top View Front View Profile View

Front View in PFD

Top View in ND

Profile View in VSD as part of ND

DESIGN for 3 Dimensional Situational Awareness


Flight deck


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EFIS • An Electronic Flight Instrument System (EFIS) is a flight deck instrument display system in which the display technology used is electronic rather than electromechanical. EFIS normally consists of a primary flight display (PFD), multi-function display (MFD) and Engine Indicating and Crew Alerting System (EICAS) display. Although cathode ray tube (CRT) displays were used at first, liquid crystal displays (LCD) are now more common.

Olden Days – Electromechanical Displays – Glass Tube display


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Basic Flight instruments


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PFD/ND Format

PFD - Basic “T”

MACH Airspeed Tape

Attitude Indicator Horz. Situation Ind.


Vert. Altitude Speed Tape Tape

ND - VOR

EFIS Format

Basic “T”

Mach/Airspeed Ind. Radio Dist. Mag. Ind. © 2010 Infosys Technologies Limited

Attitude Indicator Horz. Situation Ind.

NAV Display

Altimeter Vertical Speed Ind.

Pitot instruments


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Vertical Speed Indicator


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Navigation Systems -Methods Terrestrial or

Pilotage

Satellite

Radio Navigation

Navigation

Dead Reckoning Inertial Navigation System (INS)

Celestial Navigation

ADF VOR

ILS MLS

DME TACAN

Hyperbolic Navigation


LORAN OMEGA

Precision Landing Aids

Self contained

GPS GLONAS

ADF & VORs ADF Provides Aircraft bearing with respect to a Ground station called NDB

VORs: Provides Aircraft radial W.R.T a ground station


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DME Distance measuring Equipment provides distance between Aircraft and DME ground station. Ideally we want a ground distance between Aircraft and DME station, but DME normally provides the slant distance


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RMI Indicator Showing VOR, HDG and ADF


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Question Question: Why do you require 3 Navigational Aids DME, ADF and VORs? Can we do with one?


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Over/Under Engine Format Center Upper Display Unit

Primary Engine Display © 2010 Infosys Technologies Limited

Center Lower Display Unit

Secondary Engine Display

Navigation Aids Air navigation needs 1.

Earth model for reference

2.

A co-ordinate system to identify position/fixes and to compute distances

3.

Navigational aids for reducing the workload of Navigator/pilot

Basic Navigation aids Aeronautical Charts: specialized maps that show more than geographical features 1.

Navigation aids and airways which are highways in the air

2.

location of airports, Land marks like mountains, rivers, lakes etc.

3.

National borders

Magnetic compass


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Aeronautical Map / Chart

Understanding Aeronautical MapsVideo


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Ex: Symbols – Navigational Aids VOR, short for VHF omnidirectional radio range


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Airspace Structure


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Airspace


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Class C & Class D


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Class E & G


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CNSA Systems •Navigation Helps in en route navigation

•Communication Infrastructure providing connectivity between AirGround and Ground-Ground systems

•Surveillance Helps gathering weather reports, collision detection etc.

•ATM Managing Air Traffic Integrated CNS Architecture to improve ATM


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Aircraft Communication Systems


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Aviation Communication Applications :Voice and Data • Air Traffic Management (ATM) – Air Traffic Control (ATC)

– Air Traffic Services (ATS) – Communication, Navigation, & Surveillance (CNS) • Airline Operational Communications (AOC) – Flight Operations

– Maintenance – Airport Operations • Airline Administrative Communications (AAC) • Airline Passenger Communications (APC)Management (ATM)


Aviation Communication Equipment • Voice Communication from Aircraft to Ground Station (ATC) and other aircraft using • Digital Audio Control Panel • VHF Radio • HF Radio • SATCOM…. For Passenger Telephony services

• Data Communication from Aircraft to Ground Station (GSPs) and in turn to ATC & Airlines (Terminal services) using • ACARS/CMU (Aircraft Communications Addressing and Reporting System) • VHF Radio • HF Radio • SATCOM


Fundamentals Of Modulation • To Transmit Information Over Long Distances High Frequency Carriers Are Required • Higher the Frequency, Smaller the Wavelength & Smaller the Antenna Dimensions • For Example, Wavelength at 100MHz is 3 Meters • To Send Information (Voice &/or Data) we have to alter some Characteristic of the Carrier Waveform as a Function of Information. This is called Modulation. • Modulation can be Analog (Voice or Digital) • Carrier Frequencies are Allocated Internationally & Nationally for Various Services Ex: Cellular Comm., TV, FM Radio, Air/Ground Communications • Air/Ground Comm. Frequency Band is 118 MHz to 137 MHz.


Analog Communications Overview • Modulating signal m(t) • Carrier = A Sin (ωct+φ) • Modulation schemes • Amplitude Modulation • Frequency Modulation • Phase Modulation


Surveillance Systems


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Surveillance Systems in Civil Aircraft For all weather operation, Surveillance Systems needed in Civil Aircraft are for:• Enhanced Ground Proximity Warning System (EGPWS) – Most of the accidents happen under poor visibility and pilot is unaware of the terrain and flies into it. • Traffic Collision Avoidance System (TCAS) TCAS provides advisories • Traffic (indicating the presence of other aircraft) and • Resolution (indicating the maneuver, climb or descend)

• Weather Hazards (Weather Radar/EO Sensor) to indicate the direction and location of Hazards such as Thunderstorms, Turbulence, Windshear, so that the pilot can steer the aircraft away.


EGPWS- Basic Functions

7 modes of EGPWS

Mode 1: Excessive Descent Rate Mode 2: Excessive Closure to Terrain Mode 3: Altitude Loss after Takeoff Mode 4: Unsafe Terrain Clearance Mode 5: Excessive Glideslope Deviation Mode 6: Advisory Callout/Bank Angle Mode 7: Wind shear Alerting

EGPWS: Video


Air Traffic Management


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Air Traffic Management 1.

Air traffic is monitored/ managed through highly structured systems 2. Pilots are governed by Flight traffic Rules 3. Controllers instructs pilots during every stage of the flight 4. Ensures safety, avoids collisions, chaos


Flight Profile

Preflight : •Pilot fills flight plan •Gets weather info •Performs checks •Taxis Aircraft from terminal gate to designated runway


Flight Profile Take Off : •Pilot receives permission from Local Control (Tower) to take off •Powers Up aircraft •Begins take off roll


Flight Profile Departure : •Departure Control takes over (TRACON) •Pilot is issued with altitude and route clearance


Flight Profile Enroute : •Pilot receives instructions on what altitude maintain what frequencies to switch etc.


Flight Profile Descent : •Pilot contacts Descent control. •Receives instruction to descent and change heading towards destination airport


Flight Profile Approach : •Pilot receives Approach clearance. •Files flight procedure to get designated runway •Control changes from TRACON to Local Tower for landing clearance


Flight Profile Landing : •Pilot receives clearance for landing on the designated runway • On touching the ground the control is transferred to ground controller • Ground controller directs the pilot across taxiways to reach the terminal gate


Flight Service Station (FSS)

FSS provides following services to private pilots •Preflight briefings • Weather information departure airport, route and destination airport •Three types of briefings •Standard •Complete initial info

•Abbreviated •Updates to standards

•Outlook •Forecast information •Emergency Assistance • Aircraft loses its way • Emergency Landing


Local Control ( Tower )

Control towers provide safe, orderly flow of air traffic at airport and its vicinity. There are four major classifications of control towers 1. Flight Data controller ( Pre flight ) • •

2.

Clearance Delivery controller ( Pre flight ) •

3.

Is responsible for the ground movement of aircraft taxiing or vehicles operating on taxiways or inactive runways

Local controller ( Take off and Approach) • •


Responsible for obtaining and relaying departure clearances to pilots

Ground Controller ( Preflight Taxiing) •

4.

Relays Weather info and NOTAM ( Notice to Air Men) Operates Flight Data processing equipment

Provides safety sequencing of Arrivals and departures Maintains separation between Arrivals and departures

TRACON- ( Terminal Radar Approach Control)

Bay Area Class B airspace


• TRACON controllers direct aircraft during descent and departure • One TRACON can handle multiple Air ports • Aim is to maintain separation between the flights •Equipped with Radars, monitor Radar screens and maintain Voice/Data communication with Pilot • Hands off control to next TRACON at the edge of Air Space

Center ( ARTCC) • Center or Air Route Traffic Control Center directs Aircraft during en route •Three controller positions •Radar controller •Controller in-charge •Ensures separation between Aircrafts •Lateral – 5 miles •Vertical – 1000ft ( below 29000 ft 2000ft ( Above 29000 ft)

•Associate controller •Receives Flight Plan 5 - 20 min before Aircraft arrives the sector airspace

•Radar Handoff •Assists Radar controller during heavy traffic


Working Together

• During pre flight • • • •

Flight plan is filed Weather info is obtained Departure clearance is obtained Receives instructions from the ground controller to reach the designated take off run way

• Pilot receives “Cleared for Departure” from the local tower for the take off

• After take off pilot is instructed to change the frequency to contact Departure controller in TRACON. Aircraft is routed away from airport through assigned heading with climb clearance for new altitude •Now aircraft is handed over to Center controller for en route direction. Center controller monitors and gives instructions to pilot throughout his airspace from sector to sector


Working Together • Once the aircraft is around 150 miles from destination Airport it starts descent phase. • It moves from cruising altitude to a lower altitude • Around 50 miles from airport it is handed over to TRACON controller where the aircraft enters Approach phase • Approach controller blends different streams of aircraft into a single line for landing in run ways

• Flight is then handed over to Local Tower controller who give clearance for landing in the designated runway. •After landing the control is given to the ground controller who directs the pilot across taxi ways to the terminal gate London Heathrow Take off

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5 3


2 4

Flight Control Systems


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Flight Control Systems

1. Basic Object Motions. 2. Aircraft Motions & Control Surfaces. 3. Other flight control Surfaces. 4. Classification of Flight Control Surfaces. 5. Flight Control System.


Basic Object Motions

1. Translation 2. Rotation


Basic Object Motion - Translation

We live in a world that is defined by three spatial dimensions and one time dimension. Objects move within this domain in two ways. An object translates, or changes location, from one point to another. •And an object rotates, or changes its attitude. In general, the motion of any object involves both translation and rotation. The translations are in direct response to external forces. The rotations are in direct response to external torques or moments (twisting forces)


Basic Object Motion – Translation and Rotation


Control of Vehicles •There are many types of vehicles used to transport people and objects from place to place on Earth. How are these vehicles guided to a destination? For Car :- Turning the steering wheel changes a car's direction.


Control of Vehicles For Boat :- The rudder is used to control the direction of a boat.


Control of Vehicles For Bicycle :- A bicycle is controlled by turning the handle bars and shifting the rider's weight.


The Wright 1902 Glider- Flight control


Control surfaces and aircraft six degrees of freedom


Vertical Stabilizer

Horizontal Stabilizer

Rudder Elevator

Airbrake / Spoilers

Aileron


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Airplane Parts - Control Surfaces


Flight Control System 1. Conventional Control System 2. Fly-By-Wire Control System 3. AutoPilot


Flight Control System and its top level needs •The flight control system is the system which controls the plane. This system consists of mechanical and electronic parts, and the pilot. • It has to improve safety by means of a high degree of fault tolerance, and also by relieving the tasks of the pilot: •· Reduce the pilot’s workload by providing an intuitive user interface and by performing some functions automatically. •· Prevent the crew from inadvertently exceeding the aircraft’s controllability limits. •· Act to maintain the aircraft within its normal range of operation. •· Prevent the pilot from inadvertently entering a stall condition. Mission: The flight control system has to be highly unlikely to fail (effectively fault tolerant) so the plane can have safe flights. Use profile: The system has to operate during each flight (from takeoff to landing). Lifecycle: Same as lifecycle of the plane, which is somewhere around 2030years.


Flight Control System •To achieve flight control we require the capability to control the forces and moments acting on the vehicle; if we can control these, then we have control of accelerations and hence velocities, translations and rotations. •Direct mechanical linkages were used between the pilot’s cockpit controls (pitch/roll stick and rudder pedals) and the control surfaces that maneuver aircraft, which are : tail plane, ailerons and rudder. Advantages •This arrangement is inherently of high integrity, in terms of probability of loss of aircraft control, and provides us with a very visible baseline for explaining FCS developments. Issues Pilot(s) work load is more Non-optimized handling qualities Maintenance costs are high. © 2010 Infosys Technologies Limited

Mechanical Flight Controls

On aircraft of the A300 and A310 type, the pilot commands are transmitted to the servo-controls by an arrangement of mechanical components (rods, cables, pulleys, etc.). In addition, specific computers and actuators driving the mechanical linkages restore the pilot feels on the controls and transmit the autopilot commands


Electrical Flight Controls - FBW

The term fly-by-wire has been adopted to describe the use of electrical rather than mechanical signaling of the pilot’s commands to the flying control actuators. One can imagine a basic form of fly-by-wire in which an airplane retained conventional pilot’s control columns and wheels, hydraulic actuators (but electrically controlled), and artificial feel as experienced in the 1970s with the Concorde program. The fly-by-wire system would simply provide electrical signals to the control actuators that were directly proportional to the angular displacement of the pilot’s controls, without any form of enhancement.


Hydraulic System For Flight Control On Boeing 727 Aircraft


Control surfaces & Cockpit controls connectivity


Control surfaces & Cockpit controls connectivity



Flight Controls Pitch Trim Pointer Pitch Trim Digital Readout Stabilizer Position Display

Pitch Trim Scale Left Elevator Position

Right Elevator Position

Rudder Position Right Ground Spoiler Position

Left Ground Spoiler Position

Right Flight Spoiler Position

Left Flight Spoiler Position

Right Aileron Position

Left Aileron Position

Right Flap Position

Left Flap Position

Right Flap Detent Digital Readout

Left Flap Detent Digital Readout Left Tire Graphic

Right Tire Graphic Right WOW Status Annunciation

Left WOW Status Annunciation

Nose Tire Graphic


Combined WOW Status Annunciation

Nose WOW Status Annunciation

Static Stability of Aircrafts If the airplane is disturbed, for example, by atmospheric turbulence, and noses up slightly (angle of attack increases), the airplane is no longer in equilibrium. If the new forces and moments, caused by the angle-of-attack increase, produce a tendency to nose up still further, the airplane is statically unstable and its motion will diverge from equilibrium. If the initial tendency of the airplane is to hold the disturbed position, the airplane has neutral static stability. On the other hand, if restoring forces and moments are generated by the airplane that tend initially to bring it back to its equilibrium straight and level condition, it is statically stable


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Dynamic Stability of Aircrafts If it is assumed that the airplane is statically stable, it may undergo three forms of motion with time. (1) It may nose down, overshoot, nose-up, overshoot to a smaller degree, and eventually return to its former equilibrium condition of straight and level flight. This type of decaying oscillatory motion indicates that the airplane is dynamically stable. (2) It may continue to nose up and down thereafter at a constant amplitude. The airplane is said to have neutral dynamic stability. Or, in the worst case, (3) it may nose up and down with increasing magnitude and be dynamically unstable. © 2010 Infosys Technologies Limited

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Digital Fly-By-Wire flight control system

In Summary…

• Conventional aircraft control systems rely on mechanical and hydraulic links between the aircraft’s controls and the flight surfaces on the wings and tail. The controls and flight surfaces are directly connected. Mechanical links are also used for the engine control. • In fly-by-wire systems, the cockpit controls generate electronic signals that are interpreted by a computer system and are then converted into outputs that drive the hydraulic system connected to the flight surfaces. Engine control is also mediated by the FCS computers.


Advantages of ‘fly-by-wire’

Advantages of Fly By Wire

•

Pilot workload reduction • The fly-by-wire system provides a more usable interface and takes over some computations that previously would have to be carried out by the pilots.

•

Airframe safety • By mediating the control commands, the system can ensure that the pilot cannot put the aircraft into a state that stresses the airframe or stalls the aircraft.

•

Weight reduction • By reducing the mechanical linkages, a significant amount (and hence fuel) is saved.


of weight

Aircraft control surface servo model


Aircraft control surface servo model

Hydraulic actuator © 2010 Infosys Technologies Limited

Autopilot • Basic Function of autopilot is to control the flight of the aircraft and maintain it on a predetermined path in space without any action being required by the pilot, once the pilot has selected the appropriate control mode of the autopilot. • The autopilot can thus relieve the pilot from the fatigue and tedium of having to maintain continuous control of aircraft’s flight path on a long duration flight. • A well designed autopilot, properly integrated with FCS can achieve a faster response and maintain a more precise flight path than the pilot. .


Autopilot Loop Flight Path Deviation Commanded Flight Path

+

Autopilot -

Flight Control Loop

Flight Path Kinematics

Sensors

Autopilot –guidance function in outer loop- generates commands for FCS in inner loop These are generally attitude commands which operate the aircraft’s control surfaces through a closed loop control system so that the aircraft rotates about the pitch and roll axes until the measured pitch and bank angles are equal to the commanded values. The changes in the aircraft attitude then cause the flight path to change through flight path kinematics. © 2010 Infosys Technologies Limited

Autopilot Loop • To correct a vertical deviation from the desired flight path, pitch attitude is controlled to increase or decrease the angular inclination of the flight path to the horizontal. The resulting vertical velocity component thus causes the aircraft to climb or dive so as to correct the vertical displacement from the desired flight path. • To correct a lateral displacement from the desired flight path requires the aircraft to bank in order to turn and produce a controlled change in heading so as to correct the error. • The pitch attitude control loop and the heading control loop, with its inner loop commanding the aircraft bank angle, are fundamental inner loops in various autopilot modes. • The outer autopilot loop is thus an essentially a slower, longer period control loop compared with the inner flight control loops which are faster, shorter period loops.


Autopilot modes • Height Control • Heading Control • ILS/MLS Coupled autopilot


Autopilot


Aircraft Electrical System


Aircraft Electrical Systems • The function of the aircraft electrical system is to generate, regulate and distribute electrical power throughout the aircraft • New-generation aircraft rely heavily on electrical power because of the wide use of electronic flight instrument systems


Electrical Power Uses • Aircraft electrical power is used to operate: • Aircraft Flight Instruments • Essential Systems • Passenger Services


Aircraft Electric Power Aircraft AircraftElectric Electric Power Power

Power Power Generation Generation

AC AC Generation Generation

DC DC Generation Generation


Power Power Distribution Distribution

External External Power Power

Standby Standby Power Power Distribution Distribution

Primary Primary Power Power Distribution Distribution

Secondary Secondary Power Power Distribution Distribution

Power Used • Aircraft electrical components operate on many different voltages both AC and DC • However, most of the systems use: • 115 VAC @ 400 Hz • 28 VDC

• 26 VAC is also used in some aircraft for lighting


Electrical Power Uses (cont.) • Essential power is power that the aircraft needs to be able to continue safe operation • Passenger services power is the power that used for: • Cabin lighting • Operation of entertainment systems • Preparation of food


Power Sources • There are sever different power sources on large aircraft to be able to handle excessive loads, for redundancy, and for emergency situations. • These power sources include: • Engine driven AC generators • Auxiliary Power Units • External power • Ram Air Turbines


Engine Driven AC Generators • Each of the engines on an aircraft drives an AC generator • The power produced by these generators is used in normal flight to supply the entire aircraft with power


APU Power • Most often the APUs power is used while the aircraft is on the ground during maintenance or for engine starting • However, most aircraft can use the APU while in flight as a backup power source


External Power • External power may only be used with the aircraft on the ground • This system utilizes a Ground Power Unit (GPU) to provide AC power through an external plug on the nose of the aircraft • GPUs may be either portable or stationary units


Electric Equipment Placement in Aircraft Primary Power Distribution Panels

Secondary Power Distribution Panels

Main Generator

Static Inverter

APU Starter Converter

Standby Power Distribution Panel APU Generator

Battery

APU Battery

Generator Control Units

Transformer Rectifier Units Main Generator Ram Air Turbine

Component Installations on a Generic Airplane © 2010 Infosys Technologies Limited

Secondary Power Distribution Panels

Type of aircraft voltages Type

Description

115Vac, 400Hz

v

t

Sources • •

400Hz

•

115Vac, Variable Frequency 28Vdc

v

•

t •

350-800Hz •

v t

•

Reason to Use

Converter (AC-AC) Lower distribution losses Ram Air Turbine Inverter (DC-AC) Many loads use this AC Generator Saves cost of Ram Air Turbine conversion from generation source Battery Reliable supply Converter (AC-DC Safer voltage level •

• •

• •

or DC-DC)

270Vdc

•

v

•

t

•

DC Generator Lower distribution Ram Air Turbine losses Converter (AC-DC) •

All systems use multiple power sources for redundancy!!


Stages of electric power

Generation + • AC Generators • DC Generators • RAT • Turbo Generators • EPU • Battery


Conversion • Variable Speed Constant Frequency • DC-DC • AC-DC • DC-AC • Starter Generator Converter

+

Distribution

+

• Power Distribution Units • Embedded Bus • Smart Contactors • Remote Contactors • Circuit Breakers • Solid State Power Controls (SSPC)

Control • Bus Power Control (BPCU) • Generator Control Unit (GCU) • Electrical Load Control (ELCU)

Utilization • Motors • Motor Controls • Actuation

Ram Air Turbine • Some aircraft are equipped with Ram Air Turbines, or “RATs” • These may be used, in the case of a generator or APU failure, as an emergency power source • When necessary, the RAT may be deployed to be used as an AC power source


Aircraft Batteries • The aircraft’s nickel cadmium battery is final source of backup power • The battery provides 28 VDC • It is also possible to change the 28 VDC into 115 VAC 400Hz with the use of a static inverter • When using the battery, power usage is limited by the short life of the battery


Electrical Power System Components • AC Generator • Constant Speed Drive • Integrated Drive Generator • Transformer Rectifier Unit • Generator Control Unit


Constant Speed Drive • The purpose of the Constant Speed Drive (CSD) is to take rotational power from the engine and, no matter the engine speed, turn the generator at a constant speed • This is necessary because the generator output must be 400Hz • CSD Operation • The engine turns the CSD which uses a differential assembly and hydraulic pumps to turn the generator


Integrated Drive Generator • Another method of regulating the generator speed is with the use of an Integrated Drive Generator (IDG) • An IDG is simply a CSD and generator combined into one unit • There are two ways to mount the IDG: • Co-axially • Side-by-side


Transformer Rectifier Unit • Transformer Rectifier Units (TRUs) are utilized to 115 VAC, 400Hz into 28 VDC • A transformer is used to reduce the voltage from 115 volts to 28 volts • At this point the 28 volts is still AC current • To change the current from AC to DC, a rectifier is used • Each aircraft AC bus feeds a TRU which feeds a DC bus


Other Generator Controls and Monitoring Devices • A Generator Control Unit (GCU), or voltage regulator, is used to control generator output • Generator circuit protection monitors electrical system parameters • Voltage • Frequency • Overcurrent • Undercurrent • Differential Fault


Other Generator Controls and Monitoring Devices • Load controls sense real system load to provide a signal to the CSD for frequency control • Current transformers are used for current load sensing and differential fault protection • The electrical system control panel may be found either on the pilot’s overhead panel or on the flight engineer’s panel


Function of System Components • The basic functions of the electrical system’s components are to: • • • •

Generate Power Control Electrical Power Protect the Electrical System Distribute Electrical Power Throughout the Aircraft


Aircraft Lighting system

Wing tip lights indicates direction of flight © 2010 Infosys Technologies Limited

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References 1. 2. 3. 4.

http://www.navfltsm.addr.com/basic-nav-general.htm http://www.luizmonteiro.com/Index.aspx http://www.thaitechnics.com/nav/nav_intro.html http://en.wikipedia.org/wiki/Electronic_Flight_Instrument_System


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Thank you

“The contents of this document are proprietary and confidential to Infosys Technologies Ltd. and may not be disclosed in whole or in part at any time, to any third party without the prior written consent of Infosys Technologies Ltd.” “© 2010 Infosys Technologies Ltd. All rights reserved. Copyright in the whole and any part of this document belongs to Infosys Technologies Ltd. This work may not be used, sold, transferred, adapted, abridged, copied or reproduced in whole or in part, in any manner or form, or in any media, without the prior written consent of Infosys Technologies Ltd.”


Aircraft Electric & Electronics

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