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for the expert pilot.
Figure 3-1. The size of waves is determined by the speed of the wind.
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can subject the floats to hard pounding as they strike
consecutive wave crests. Operating on the surface in
rough conditions exposes the seaplane to forces that
can potentially cause damage or, in some cases,
overturn the seaplane. When a swell is not aligned
with the wind, the pilot must weigh the dangers
posed by the swell against limited crosswind
capability, as well as pilot experience.
On the other hand, calm, glassy water presents a different
set of challenges. Since the wind is calm, taxiing and
docking are somewhat easier, but takeoffs and landings
require special techniques. Takeoff distances may be
longer because the wings get no extra lifting help from
the wind. The floats seem to adhere more tenaciously to
the glassy water surface. When landing, the flat,
featureless surface makes it far more difficult to
gauge altitude accurately, and reflections can create
confusing optical illusions. The specific techniques
for glassy water operations are covered in Chapter
4, Seaplane Operations–Preflight and Takeoffs, and
Chapter 6, Seaplane Operations–Landing.
Tides are cause for concern when the airplane is
beached or moored in shallow water. A rising tide can
lift a beached seaplane and allow it to float out to sea if
the airplane is not properly secured. Depending on the
height of the tide and the topography of the beach, an
outgoing tide could leave a beached seaplane stranded
far from the water. [Figure 3-2]
While waves are simply an up and down undulation of
the water surface, currents are horizontal movements
of the water itself, such as the flow of water downstream
in a river. Currents also exist in the oceans,
where solar heating, the Earth’s rotation, and tidal
forces cause the ocean water to circulate.
WATER EFFECTS ON OPERATIONS
Compared to operations from typical hard-surface
runways, taking off from and landing on water presents
several added variables for the pilot to consider.
Waves and swell not only create a rough or uneven
surface, they also move, and their movement must be
considered in addition to the wind direction.
Likewise, currents create a situation in which the
surface itself is actually moving. The pilot may
decide to take off or land with or against the current,
depending on the wind, the speed of the current, and
the proximity of riverbanks or other obstructions.
While a landplane pilot can rely on windsocks and
indicators adjacent to the runway, a seaplane pilot
needs to be able to read wind direction and speed from
the water itself. On the other hand, the landplane pilot
may be restricted to operating in a certain direction
because of the orientation of the runway, while the seaplane
pilot can usually choose a takeoff or landing
direction directly into the wind.
Even relatively small waves and swell can complicate
seaplane operations. Takeoffs on rough water
Figure 3-2. An outgoing tide can leave a seaplane far from the water. A rising tide can cause a beached seaplane to float away.
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Many of the operational differences between landplanes
and seaplanes relate to the fact that seaplanes
have no brakes. From the time a seaplane casts off,
it is usually in continuous motion due to the wind
and current, so the pilot must take deliberate action
to control this movement. Often these forces can be
used to the pilot’s advantage to help move the seaplane
as desired. Starting the engine, performing the engine
runup, and completing most pre-takeoff checks are all
accomplished while the seaplane is in motion. The
seaplane continues moving after the engine is shut
down, and this energy, along with the forces of wind
and current, is typically used to coast the seaplane to
the desired docking point.
As with land airplanes, the wind tends to make the
airplane weathervane, or yaw, until the nose points
into the wind. This tendency is usually negligible on
landplanes with tricycle landing gear, more pronounced
on those with conventional (tailwheel) gear,
and very evident in seaplanes. The tendency to
weathervane can usually be controlled by using the
water rudders while taxiing, but the water rudders are
typically retracted prior to takeoff. Weathervaning
can create challenges in crosswind takeoffs and
landings, as well as in docking or maneuvering in
close quarters.
SEAPLANE BASE OPERATIONS
In the United States, rules governing where seaplanes
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