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landing. In that situation, the seaplane may stall and
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6-4
path. As the seaplane touches down on the upwind
float, the water drag will quickly slow the seaplane and
the other float will touch down as aerodynamic lift
decreases. Close the throttle, and as the seaplane’s
speed dissipates, increase aileron to hold the upwind
wing down. The seaplane is most unstable as it is coming
off the step and transitioning through the plowing
phase. Be ready for the seaplane to weathervane into the
wind as the air rudder becomes less effective. Many
pilots make a turn to the downwind side after landing to
minimize weathervaning until the seaplane has slowed
to taxi speed. Since the seaplane will weathervane
sooner or later, this technique reduces the centrifugal
force on the seaplane by postponing weathervaning until
speed has dissipated. Once the seaplane settles into the
displacement attitude, lower the water rudders for better
directional control. [Figure 6-4]
Another technique used to compensate for crosswinds
(preferred by many seaplane pilots) is the downwind
arc method. Seaplanes need not follow a straight path
during landing, and by choosing a curved path, the pilot
can create a sideward force (centrifugal force) to offset
the crosswind force. This is done by steering the seaplane
in a downwind arc as shown in figure 6-5. During
the approach, the pilot merely plans a curved landing
path and follows this path to produce sufficient centrifugal
force to counter the wind force. During the
landing run, the pilot can adjust the amount of centrifugal
force by varying rudder pressure to increase or
decrease the rate of turn. This technique allows the
pilot to compensate for a changing wind force during
the water run.
Figure 6-5 shows that the tightest curve of the downwind
arc is during the time the seaplane is traveling at
low speed. Faster speeds reduce the crosswind effect,
and at very slow speeds the seaplane can weathervane
into the wind without imposing large side loads or
stresses. Again, experience plays an important part in
successful operation during crosswinds. It is essential
that all seaplane pilots have thorough knowledge and
skill in these maneuvers.
Figure 6-3. Improper technique or excessive crosswind forces can result in an accident.
Vertical
Component
Horizontal
Component
Angle Exaggerated
for Clarity.
Figure 6-4. Dropping the upwind wing uses a horizontal component
of lift to counter the drift of a crosswind.
Ch 06.qxd 8/25/04 10:45 AM Page 6-4
6-5
DOWNWIND LANDING
Although downwind landings often require significantly
more water area, there are occasions when they
are more convenient or even safer than landing into the
wind. Sometimes landing upwind would mean a long,
slow taxi back along the landing path to get to the dock
or mooring area. If winds are less than 5 knots and there
is ample room, landing downwind could save taxi time.
Unless the winds are light, a downwind landing is seldom
necessary. Before deciding to land downwind, the
pilot needs a thorough knowledge of the landing characteristics
of the seaplane as well as the environmental
factors in the landing area.
As with a downwind landing in a landplane, the main
concern for a seaplane is the additional groundspeed
added by the wind to the normal approach speed. The
airspeed, of course, is the same whether landing
upwind or downwind, but the wind decreases groundspeed
in upwind landings and increases groundspeed
in downwind landings. While a landplane pilot seldom
thinks about the additional force placed on the landing
gear by a higher groundspeed at touchdown, it is a serious
concern for the seaplane pilot. A small increase in
water speed translates into greatly increased water drag
as the seaplane touches down, increasing the tendency
of the seaplane to nose over. In light winds, this usually
presents little problem if the pilot is familiar with how
the seaplane handles when touching down at higher
speeds, and is anticipating the increased drag forces. In
higher winds, the nose-down force may exceed the
ability of the pilot or the flight controls to compensate,
and the seaplane will flip over at high speed. If the
water’s surface is rough, the higher touchdown speed
also subjects the floats and airframe to additional
pounding.
If there is a strong current, the direction of water flow
is a major factor in choosing a landing direction. The
speed of the current, a confined landing area, or the surface
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