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AIM

10/12/17

6

−3−4

Distress and Urgency Procedures

FIG 6

−3−5

Wind

−Swell−Ditch Heading

GOOD

GOOD !!

BACK SIDE

POOR!!!

FACE

GOOD

FAIR

BEST

BEST

DIRECTION OF

SWELL MOVEMENT

Landing parallel to the major swell

Landing on the face and back of swell

a.

A successful aircraft ditching is dependent on

three primary factors. In order of importance they are:

1. Sea conditions and wind.

2. Type of aircraft.

3. Skill and technique of pilot.

b. Common oceanographic terminology.

1. Sea.

The condition of the surface that is the

result of both waves and swells.

2. Wave 

(or Chop). The condition of the

surface caused by the local winds.

3. Swell.

The condition of the surface which

has been caused by a distance disturbance.

4. Swell Face.

The side of the swell toward the

observer. The backside is the side away from the
observer. These definitions apply regardless of the
direction of swell movement.

5. Primary Swell.

The swell system having the

greatest height from trough to crest.

6. Secondary Swells.

Those swell systems of

less height than the primary swell.

7. Fetch.

The distance the waves have been

driven by a wind blowing in a constant direction,
without obstruction.

8. Swell Period.

The time interval between the

passage of two successive crests at the same spot in
the water, measured in seconds.

9. Swell Velocity.

The speed and direction of

the swell with relation to a fixed reference point,
measured in knots. There is little movement of water
in the horizontal direction. Swells move primarily in
a vertical motion, similar to the motion observed
when shaking out a carpet.

10. Swell Direction.

The direction from which

a swell is moving. This direction is not necessarily the
result of the wind present at the scene. The swell may
be moving into or across the local wind. Swells, once
set in motion, tend to maintain their original direction
for as long as they continue in deep water, regardless
of changes in wind direction.