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6/17/21 

AIM 

11.  Swell Height. 

The height between crest 

and trough, measured in feet. The vast majority of 
ocean swells are lower than 12 to 15 feet, and swells 
over 25 feet are not common at any spot on the 
oceans. Successive swells may differ considerably in 
height. 

c. 

In order to select a good heading when ditching 

an aircraft, a basic evaluation of the sea is required. 
Selection of a good ditching heading may well 
minimize damage and could save your life. It can be 
extremely dangerous to land into the wind without 
regard to sea conditions; the swell system, or systems, 
must be taken into consideration. Remember one 
axiom

 

AVOID THE FACE OF A SWELL. 

1. 

In ditching parallel to the swell, it makes little 

difference whether touchdown is on the top of the 
crest or in the trough. It is preferable, however, to land 
on the top or back side of the swell, if possible. After 
determining which heading (and its reciprocal) will 
parallel the swell, select the heading with the most 
into the wind component. 

2. 

If only one swell system exists, the problem 

is relatively simple

even with a high, fast system. 

Unfortunately, most cases involve two or more swell 
systems running in different directions. With more 
than one system present, the sea presents a confused 
appearance. One of the most difficult situations 
occurs when two swell systems are at right angles. 
For example, if one system is eight feet high, and the 
other three feet, plan to land parallel to the primary 
system, and on the down swell of the secondary 
system. If both systems are of equal height, a 
compromise may be advisable

select an intermediate 

heading at 45 degrees down swell to both systems. 
When landing down a secondary swell, attempt to 
touch down on the back side, not on the face of the 
swell. 

3. 

If the swell system is formidable, it is 

considered advisable, in landplanes, to accept more 
crosswind in order to avoid landing directly into the 
swell. 

4. 

The secondary swell system is often from the 

same direction as the wind. Here, the landing may be 
made parallel to the primary system, with the wind 
and secondary system at an angle. There is a choice 
to two directions paralleling the primary system. One 
direction is downwind and down the secondary swell, 
and the other is into the wind and into the secondary 

swell, the choice will depend on the velocity of the 
wind versus the velocity and height of the secondary 
swell. 

d. 

The simplest method of estimating the wind 

direction and velocity is to examine the windstreaks 
on the water. These appear as long streaks up and 
down wind. Some persons may have difficulty 
determining wind direction after seeing the streaks on 
the water. Whitecaps fall forward with the wind but 
are overrun by the waves thus producing the illusion 
that the foam is sliding backward. Knowing this, and 
by observing the direction of the streaks, the wind 
direction is easily determined. Wind velocity can be 
estimated by noting the appearance of the whitecaps, 
foam and wind streaks. 

1. 

The behavior of the aircraft on making 

contact with the water will vary within wide limits 
according to the state of the sea. If landed parallel to 
a single swell system, the behavior of the aircraft may 
approximate that to be expected on a smooth sea. If 
landed into a heavy swell or into a confused sea, the 
deceleration forces may be extremely great

resulting 

in breaking up of the aircraft. Within certain limits, 
the pilot is able to minimize these forces by proper sea 
evaluation and selection of ditching heading. 

2. 

When on final approach the pilot should 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 short 
and rough seas. Touchdown in these areas is to be 
avoided. Select and touchdown in any area (only 
about 500 feet is needed) where the shadows and 
whitecaps are not so numerous. 

3. 

Touchdown should be at the l

owest

 speed and 

rate of descent which permit safe handling and 
optimum nose up attitude on impact. Once first 
impact has been made, there is often little the pilot can 
do to control a landplane. 

e. 

Once preditching preparations are completed, 

the pilot should turn to the ditching heading and 
commence let

down. The aircraft should be flown 

low over the water, and slowed down until ten knots 
or so above stall. At this point, additional power 
should be used to overcome the increased drag caused 
by the nose up attitude. When a smooth stretch of 
water appears ahead, cut power, and touchdown at the 
best recommended speed as fully stalled as possible. 
By cutting power when approaching a relatively 
smooth area, the pilot will prevent overshooting and 

Distress and Urgency Procedures 

6

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