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heading is downwind and down the secondary swell;
and the other is 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.
18.4Wind
18.4.1The simplest method of estimating the wind
direction and velocity is to examine the wind streaks
on the water. These appear as long streaks up and
down wind. Some persons may have difficulty
determining wind direction after seeing the streaks in
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
AIP
United States of America
GEN 3.6−18
15 MAR 07
Nineteenth Edition Federal Aviation Administration
direction is easily determined. Wind velocity can be
accurately estimated by noting the appearance of the
whitecaps, foam and wind streaks.
18.5Preditching Preparation
18.5.1A successful aircraft ditching is dependent on
three primary factors. In order of importance they are:
18.5.1.1Sea conditions and wind.
18.5.1.2Type of aircraft.
18.5.1.3Skill and technique of pilot.
18.5.2The 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.
18.5.3When 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 that
the seas are short and rough. 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.
18.5.4Touchdown should be at the lowest 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.
18.6Ditching
18.6.1Once preditching preparations are completed,
the pilot should turn to the ditching heading and
commence letdown. 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
noseup 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 over shooting and will
touchdown with less chance of planing off into a
second uncontrolled landing. Most experienced
seaplane pilots prefer to make contact with the water
in a semi−stalled attitude, cutting power as the tail
makes contact. This technique eliminates the chance
of misjudging altitude with a resultant heavy drop in
a fully stalled condition. Care must be taken not to
drop in a fully stalled condition. Care must be taken
not to drop the aircraft from too high altitude, or to
balloon due to excessive speed. The altitude above
water depends on the aircraft. Over glassy smooth
water, or at night without sufficient light, it is very
easy for even the most experienced pilots to misjudge
altitude by 50 feet or more. Under such conditions,
carry enough power to maintain 9 to 12 noseup
attitude, and 10 to 20 over stalling speed until
contact is made with the water. The proper use of
power on the approach is of great importance. If
power is available on one side only, a little power
should be used to flatten the approach; however, the
engine should not be used to such an extent that the
aircraft cannot be turned against the good engines
right down to the stall with a margin of rudder
movement available. When near the stall, sudden
application of excessive unbalanced power may
result in loss of directional control. If power is
available on one side only, a slightly higher than
normal glide approach speed should be used. This
will insure good control and some margin of speed
after leveling off without excessive use of power. The
　
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