Because of restricted or limited areas
of operation, it is
not always possible to take off or land the seaplane
directly into the wind. Such restricted areas may be canals
or narrow rivers. Therefore, skill must be acquired in
crosswind techniques to enhance the safety of seaplane
The forces developed by crosswinds during takeoffs or
landings on water are almost the same as those developed
during similar operations on land. Directional control is
more difficult because of the more yielding properties of
water, less surface friction, and lack of nosewheel, tailwheel,
Though a water surface is more yielding
than solid land, a seaplane has no shock absorbing capability,
so all the shock is absorbed by the hull or floats and
transmitted to the aircraft structure.
As shown in Figure 10, a crosswind tends to push the
seaplane sideways. The drifting force, acting through the
seaplane's centre of gravity, is opposed by the water reacting
on the area of the floats or hull in contact with the
water. This results in a tendency to weathervane into the
wind. Once this weathervaning has started, the turn continues
and is further aggravated by the addition of centrifugal
force acting outward from the turn, which again is
opposed by the water reaction on the floats or hull. If
strong enough, the combination of the wind and centrifugal
force may tip the seaplane to the point where the
downwind float will submerge and subsequently the
wingtip may strike the water and capsize the seaplane.
This is known as a "waterloop" similar to a "groundloop"
Figure 10: Crosswind landing technique
Because of the lack of clear reference
lines for directional
guidance, such as are found on airport runways, it is
difficult to quickly detect sidedrift on water. Fortunately,
early detection of sidedrift is not really essential, because
the seaplane takeoff and landing can be made without
maintaining a straight line while in contact with the water.
A turn should be made toward the downwind side after
landing. This will allow the seaplane to dissipate its forward
speed prior to its weathervaning into the wind. By
doing this, centrifugal force while weathervaning will be
kept to a minimum and better aircraft control will result
with less turnover tendency.
One technique sometimes used to compensate for
crosswinds during water operations is the same as that
used on land; that is, by lowering the upwind wing while
holding a straight course with rudder. This creates a slip
into the wind to offset the drifting tendency.
wing is held in the lowered position throughout the touchdown
and until completion of the landing.
Another technique used to compensate for crosswinds
(preferred by many seaplane pilots) is the downwind arc
method. Using this method, the pilot creates a sideward
force (centrifugal force) that will offset the crosswind
force. This is accomplished by steering the seaplane in a
downwind arc as shown in Figure 10. The pilot merely
plans an arced path and follows this arc to produce sufficient
centrifugal force so that the seaplane will tend to lean
outward against the wind force. During the run, the pilot
can adjust the rate of turn by varying rudder pressure,
thereby increasing or decreasing the centrifugal force to
compensate for a changing wind force.
In practice, it is quite simple to plan sufficient curvature
of the takeoff path to cancel out strong crosswinds,
even on very narrow rivers.
As illustrated in Figure 11, the
takeoff is started at the lee side of the river with the seaplane
heading slightly into the wind. The takeoff path is
then gradually made in an arc away from the wind and the
liftoff accomplished on the downwind edge of the river.
This pattern also allows for more climbout space into the
Figure 11: Crosswind takeoff and
It should be noted that the greatest
degree of the downwind
arc is during the time the seaplane is travelling at the
slower speeds of takeoff or landing. At the faster speeds,
the crosswind effect lessens considerably, and at very slow
speeds the seaplane can weathervane into the wind with no
Unless the current is extremely swift, crosswind or
calm wind takeoffs and landings in rivers or tidal flows
should be made in the same direction as the current. This
reduces the water forces on the floats or hull of the seaplanes.
Again, experience will play an important part in successful
operation during crosswinds. It is essential that all
seaplane pilots have thorough knowledge and skill in these manoeuvres.