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Seaplane Skiplane Flying Menu > Water Characteristics and Seaplane Base Operation
>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 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]
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.
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.
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