DITCHING GENERAL BRIEFING
V1.1
18 January 2007
DITCHING
TABLE OF CONTENTS DITCHING DITCHING - GENERAL GENERAL DISCUSSION DISCUSSION .................................. .................................................... ................................ .............. 3 SEA EVALUATION AND CONDITIONS CONDITIONS ........................... ......................................... ............................ ....................... ......... 3 SELECTING SELECTING THE OPTIMUM OPTIMUM HEADING FOR DITCHING DITCHING ..................................... ..................................... 5 DITCHING DITCHING PROCEDURES PROCEDURES ........................... ......................................... ............................. ............................. ........................... ............. 5 SELECTION SELECTION OF DITCHING DITCHING HEADING HEADING ..................................... ........................................................ ............................ ......... 6 SELECTION SELECTION OF TOUCHDOWN TOUCHDOWN POINT POINT ......................... ...................................... .......................... .......................... ............. 8
Page 1 of 8
DITCHING GENERAL BRIEFING
V1.1
18 January 2007
Revision Record Version
Date
Source
Change
1
30/12/02
FOT
Original Issue transferred from original EP Manual
Capture information
All
1.1
23/02/07
Introduction of General Briefing Format
Online FOT Library introduction.
All
P. Donazzan
Subject Matter unchanged
Reason
Page/s
Disclaimer:
This briefing remains the property of QANTAS. Copying for other than student’s own use is illegal. The subject content of this brief is correct at the time of publishing. In any case, the Flight Crew Operations Manuals are the authoritative documents. It is the responsibility of users to ensure that they are aware of changes or corrections to subject matter circulated by QANTAS.
Page 2 of 8
DITCHING GENERAL BRIEFING
V1.1
18 January 2007
DITCHING - GENERAL DISCUSSION Model tests, which have been confirmed by the ditching of B377 Stratocruisers, K C- 97 Refuelling Tankers and a Russian TU124, indicated that an airplane when ditched at the proper nose up attitude should land smoothly in the water without skipping There are two principle factors which cause skipping. One is that the lifting capability of the wing is increased when the aircraft's attitude is changed from a low angle at the approach, to a higher angle after touchdown of the aft body. This change in attitude, or rotation is caused by a suction force created by the upsweeping lines of the aft body entering the water. If the speed of the aircraft has not been sufficiently reduced due to contact with the water, the increased lift will cause the aircraft to skip. The reaction force caused by the aircraft striking the water with a large surface area may also induce skipping. This is the same principle that causes flat stones to skip across the water when thrown at a flat angle. An aircraft ditched at the recommended attitude and speed, should touchdown with a small surface area and should be incapable of developing enough additional lift, due to rotation, to bounce clear of the water. The attitude at touchdown will cause the loss of the trailing edge flaps, and this will also reduce the available lift of the wings to prevent the aircraft from bouncing off the water. Type Specific Information Please refer to your FCOM for type specific procedures and information.
SEA EVALUATION AND CONDITIONS The pilot must know the sea and wind conditions to select a suitable ditching heading. If an emergency occurs shortly after darkness he/she should have an estimate of the best ditching heading from observations made during the daylight. It is for this reason that pilots when flying into the dusk must note the sea conditions and determine a ditching heading prior to darkness. Many ships at sea send frequent weather reports including sea conditions. This information may sometimes be obtained through an air ground station. It should be realised however, that a forecast based on scattered ship reports and changing weather conditions is subject to error. To judge sea condition from the air, the pilot must have knowledge of what forces combine to create the disturbance of the surface. The ‘sea state’ is the condition of the surface that is the result of waves, swells and wind direction. Waves Wave (or chop) is the condition of the surface caused by local winds. It is characterised by its irregularity, short distance between crests, whitecaps and breaking motion. The waves move in the same direction as the local wind and do not exist for long unless the wind is blowing. When the waves leave the area in which they were generated their energy is slowly dissipated and at the same time their wavelength, period and velocity gradually increase. For both of these reasons, the height decreases. The shorter waves have Page 3 of 8
DITCHING GENERAL BRIEFING
V1.1
18 January 2007
less energy, and therefore disappear relatively quickly. The longer waves become more regular.
VELOCITY KNOTS
SEA INDICATION
Calm 1-3 4-6
Like a mirror Ripples with the appearance of scales Small wavelets; crests have glossy appearance and do not break Large wavelets; crest begin to break. Foam of glossy appearance Small wavelets, becoming longer. fairly frequent whitecaps Moderate waves making a pronounced long foam many whitecaps Large waves begin to form, white foam crests are more extensive; some spray Sea heaps up and white foam from breaking waves begin to be blown in streaks along the direction of waves
7 - 10 11 - 16 17 - 21
22 - 27
28 - 33
34 - 40
41 - 47
48 - 55
Moderately high waves of greater length; edges of crests break into spindrift; foam blown in well marked streaks in direction of the wind High waves. Dense streaks of foam; sea begins to roll; spray affects visibility Very high waves with overhanging crest; foam in great patches blown in dense white streaks. Whole surface of sea takes on a white appearance. Visibility is affected
HEIGHT OF WAVES (FT) 0 1/2 1 2 5 10
15
20
25
30
35
Page 4 of 8
DITCHING GENERAL BRIEFING
V1.1
18 January 2007
SELECTING THE OPTIMUM HEADING FOR DITCHING The objective is to select a landing direction that will result in the minimum relative speed between the aircraft and the swell system. The best heading for ditching is usually parallel to the major swell system. There is a choice of two headings paralleling the primary system: • Downwind and down the secondary swell. • Into the wind and into the secondary swell. The choice of heading will depend on the velocity of the wind versus the velocity and height of the secondary swell. The next best heading for ditching is parallel to the minor swell system and down the major swell system. The choice of these will be determined by the heading that gives the greatest component of wind on the nose of the aircraft. A descent is then made to 200 feet and the aircraft flown on successive headings each decreased by 45 degrees until the full 360 has been evaluated. The heading on which the sea appears the smoothest should be noted and checked against the direction of the main swell system as observed at 2,000 feet. The final heading should parallel the main system with minor adjustments to accommodate the secondary systems and at the same time taking advantage, where possible, of the wind. Look for a relatively smooth area. Also, look ahead for extra rough areas and try to avoid them.
DITCHING PROCEDURES Ditching • • • • •
Note or sketch this information: MAJOR SWELL direction. MINOR SWELL direction. WIND. DITCH HEADING.
Page 5 of 8
DITCHING GENERAL BRIEFING
V1.1
18 January 2007
SELECTION OF DITCHING HEADING Average run out on ditching requires 250-700 feet taking approximately 5 – 8 seconds. 1st Choice: LAND PARALLEL TO THE SWELL OR AS NEAR AS POSSIBLE
Page 6 of 8
DITCHING GENERAL BRIEFING
V1.1
18 January 2007
2nd Choice: LAND GROUND SWELL This choice depends on length of swell. The aircraft touching down on the crest must come to rest short of the next crest. In the long swells of the Pacific this technique would be a logical one . However, in the Atlantic, shorter swell lengths ordinarily prevent this heading except when landing down a secondary swell system. (In some cases selection of a ditching heading to parallel a major swell system may require landing down swell on minor system.)
Page 7 of 8
DITCHING GENERAL BRIEFING
V1.1
18 January 2007
SELECTION OF TOUCHDOWN POINT On final approach look ahead and observe the surface of the sea. There may be shadows and whitecaps - signs of large seas. Shadows and whitecaps close together indicate that the seas are rough and short - avoid these seas. Select and touch down in an area (only about 500 feet is needed) where the shadows and whitecaps are not so numerous.
Page 8 of 8
