PREFLIGHT INSPECTION
Begin the preflight inspection with a thorough review
of the existing local weather, destination weather, and
water conditions. This weather evaluation should
include the direction and speed of the wind to deter-
mine their effects on takeoffs, landings, and other
water operations.
The preflight inspection of a seaplane is somewhat dif-
ferent from that of a landplane. Inspecting a seaplane
on the water is complicated by the need to reposition
the seaplane to gain access to all parts of the airframe.
On the other hand, preflighting a seaplane on land may
create certain challenges because the wings and tail
surfaces may be out of reach and difficult to inspect
when standing on the ground.
The following preflight description omits many items
that are identical in landplanes and seaplanes in order
to emphasize the differences between the two proce-
dures. The process and the equipment to be checked
vary from airplane to airplane, but the following
description provides a general idea of the preflight
inspection for a typical high wing, single-engine float-
plane. As always, follow the procedures recommended
in the Airplane Flight Manual (AFM) or Pilot’s
Operating Handbook (POH).
If the seaplane is in the water during the preflight, take
a good look at how it sits on the surface. This can pro-
vide vital clues to the presence of water in the floats, as
well as to the position of the center of gravity. Is the
seaplane lower in the water than it should be, given its
load? Is one wing lower than the other, or is one float
riding noticeably lower in the water than the other? Are
the sterns of the floats low in the water? If any of these
signs are present, suspect a flooded float compartment
or an improperly loaded seaplane. At more than 8
pounds per gallon, even a relatively small amount of
water in a float compartment can seriously affect both
useful load and center of gravity (CG).
In the cockpit, verify that the throttle is closed, the
mixture control is full lean, and the magnetos and
master switch are turned off. Lower the water rudders
and check for any stiffness or binding in the action of
the cables. Check that necessary marine and safety
equipment, such as life vests, lines (ropes), anchors,
and paddles are present, in good condition, and
stowed correctly. Obtain the bilge pump and fuel
sample cup.
Standing on the front of the float, inspect the propeller,
forward fuselage, and wing. Check the usual items,
working from the nose toward the tail. Water spray dam-
age to the propeller looks similar to gravel damage, and
must be corrected by a mechanic. Check the oil and fuel
levels and sample the fuel, ensuring that it is the proper
grade and free of contaminants. Naturally, the most
likely contaminant in seaplane fuel tanks is water. Pay
extra attention to the lubrication of all hinges. Not only
does lubrication make movement easier, but a good coat-
ing of the proper lubricant keeps water out and prevents
corrosion. Look for any blistering or bubbling of the
paint, which may indicate corrosion of the metal under-
neath. Check the security of the float struts and their
attachment fittings. Be careful moving along the float,
and pay attention to wing struts, mooring lines, and other
obstacles. If the seaplane is on land, do not stand on the
floats aft of the step or the seaplane may tip back.
Next, inspect the float itself. Water forces can create
very high loads and lead to cumulative damage. Look
carefully for signs of stress, such as distortion or buck-
ling of the skin, dents, or loose rivets. The chines
should form a continuous smooth curve from front to
back, and there should be no bends or kinks along the
flange. If the floats are made of fiberglass or composite
materials, look carefully for surface cracks, abrasions,
or signs of delamination. Check the spreader bars
between the floats, and look at the bracing wires and
their fittings. Any sign of movement, loose fasteners,
broken welds, or a bracing wire that is noticeably
tighter or looser than the others is cause for concern.
Check for signs of corrosion, especially if the seaplane
has been operated in salt water. Although corrosion is
Ch 04.qxd 8/24/04 10:48 AM Page 4-1
less of an issue with composite floats, be sure to check
metal fittings and fasteners. [Figure 4-1]
Use the bilge pump to remove any accumulated water
from each watertight compartment. The high dynamic
water pressure and the physical stresses of takeoffs and
landings can momentarily open tiny gaps between float
components, allowing small amounts of water to enter.
Conversely, sitting idle in the water also results in a
small amount of seepage and condensation. While it is
normal to pump a modest amount of water from each
compartment, more than a quart or so may indicate a
problem that should be checked by a qualified aircraft
mechanic experienced in working on floats. Normal is
a relative term, and experience will indicate how much
water is too much. [Figure 4-2]
If pumping does not remove any water from a compart-
ment, the tube running from the bilge pump opening to
the bottom of the compartment may be damaged or
loose. If this is the case, there could be a significant
amount of water in the compartment, but the pump is
unable to pull it up. [Figure 4-3] Be sure to replace the
plugs firmly in each bilge pump opening.
At the stern of the float, check the aft bulkhead, or tran-
som. This area is susceptible to damage from the water
rudder moving beyond its normal range of travel.
Carefully check the skin for any pinholes or signs of
damage from contact with the water rudder or hinge
hardware. Inspect the water rudder retraction and steer-
ing mechanism and look over the water rudder for any
damage. Remove any water weeds or other debris
lodged in the water rudder assembly. Check the water
rudder cables that run from the float to the fuselage.
[Figure 4-4]
Figure 4-1. A preflight inspection with the seaplane on land
provides an opportunity to thoroughly examine the floats
below the waterline. Note the spray rail on the inboard chine
of the far float in this photo.
Figure 4-2. Bilge pump openings are closed with a soft rub-
ber ball.
Figure 4-3. Be suspicious if pumping does not remove a
small amount of water. If the bilge pump tube is damaged,
there may be water in the compartment that the pump can-
not remove.
Figure 4-4. Inspect the water rudders, cables, springs, and
pulleys for proper operation.
Ch 04.qxd 8/24/04 10:48 AM Page 4-2
engine. With oil pressure checked, idle r.p.m. set, and
the seaplane taxiing in the desired direction, the pilot
then fastens the seatbelt and shoulder harness, secures
the door, and continues preparing for takeoff.
When a qualified person is available to help launch the
seaplane, the pilot can strap in, close the door, and start
the engine while the helper holds the seaplane. In most
situations, the helper should position the seaplane so it
is facing outward, perpendicular to the dock. It is very
important that the helper have experience in the proper
handling of seaplanes, otherwise an innocent mistake
could cause serious damage to the seaplane or to
nearby boats, structures, or other seaplanes.
TAXIING AND SAILING
One major difference between taxiing a landplane and
taxiing a seaplane is that the seaplane is virtually
always in motion, and there are no brakes. When
idling, a landplane usually remains motionless, and
when moving, brakes can be used to control its speed
or bring it to a stop. But once untied, the seaplane
floats freely along the water surface and constantly
moves due to the forces of wind, water currents,
propeller thrust, and inertia. It is important that the
seaplane pilot be familiar with the existing wind and
water conditions, plan an effective course of action,
and mentally stay ahead of the seaplane.
There are three basic positions or attitudes used in
moving a seaplane on the water, differentiated by the
position of the floats and the speed of the seaplane
through the water. They are the idling or displacement
position, the plowing position, and the planing or step
position.
IDLING POSITION
In the idling position or displacement position , the
buoyancy of the floats supports the entire weight of
the seaplane and it remains in an attitude similar to
being at rest on the water. Engine r.p.m. is kept as low
as possible to control speed, to keep the engine from
overheating, and to minimize spray. In almost all cir-
cumstances, the elevator control should be held all the
way back to keep the nose as high as possible and min-
imize spray damage to the propeller. This also
improves maneuverability by keeping more of the
water rudder underwater. The exception is when a
strong tailwind component or heavy swells could
allow the wind to lift the tail and possibly flip the
seaplane over. In such conditions, hold the elevator
control forward enough to keep the tail down.
[Figure 4-5 on next page]
To check the empennage area, untie the seaplane, gen-
tly push it away from the dock, and turn it 90 ° so the
tail extends over the dock. Take care not to let the water
rudders contact the dock. In addition to the normal
empennage inspection, check the cables that connect
the water rudders to the air rudder. With the air rudder
centered, look at the back of the floats to see that the
water rudders are also centered. (On some systems,
retracting the water rudders disengages them from the
air rudder.) If the seaplane has a ventral fin to improve
directional stability, this is the time to check it. Spray
frequently douses the rear portion of the seaplane, so
be particularly alert for signs of corrosion in this area.
With the empennage inspection complete, continue
turning the seaplane to bring the other float against the
dock, and tie it to the dock. Inspect the fuselage, wing,
and float on this side. If the seaplane has a door on only
one side, turn the seaplane so the door is adjacent to the
dock when the inspection is complete.
When air temperatures drop toward freezing, ice
becomes a matter for concern. Inspect the float com-
partments and water rudders for ice, and consider the
possibility of airframe icing during takeoff due to
freezing spray. Water expands as it freezes, and this
expansion can cause serious damage to floats. A large
amount of water expanding inside a float could cause
seams to burst, but even a tiny amount of water freez-
ing and expanding inside a seam can cause severe
leakage problems. Many operators who remove their
floats for the winter store them upside down with the
compartment covers off to allow thorough drainage.
When the time comes to reinstall the floats, it’s a good
idea to look for any bugs or small animals that might
have made a home in the floats.
STARTING THE ENGINE
Compared to a landplane, a seaplane’s starting proce-
dures are somewhat different. Before starting the
engine, the seaplane usually needs to be pushed away
from the dock, and quite often, it is the pilot who
pushes off. Therefore, the pilot should perform as
many of the items on the starting checklist as possible
prior to shoving off. This includes briefing passengers
and seeing that they have fastened their seatbelts. The
passenger briefing should include procedures for evac-
uation, the use of flotation gear, and the location and
operation of regular and emergency exits. All passen-
gers are required to be familiar with the operation of
seatbelts and shoulder harnesses (if installed). When
the engine is primed and ready to start, the pilot leaves
the cockpit, shoves off, returns to the pilot’s seat,
quickly turns on the master switch and magnetos, veri-
fies that the propeller area is clear, and starts the
Ch 04.qxd 8/24/04 10:48 AM Page 4-3
Use the idling or displacement position for most taxi-
ing operations, and keep speeds below 6-7 knots to
minimize spray getting to the propeller. It is especially
important to taxi at low speed in congested or confined
areas because inertia forces at higher speeds allow the
seaplane to coast farther and serious damage can result
from even minor collisions. Cross boat wakes or swells
at a 45 ° angle, if possible, to minimize pitching or
rolling and the possibility of an upset.
PLOWING POSITION
Applying power causes the center of buoyancy to shift
back, due to increased hydrodynamic pressure on the
bottoms of the floats. This places more of the sea-
plane’s weight behind the step, and because the floats
are narrower toward the rear, the sterns sink farther
into the water. Holding the elevator full up also helps
push the tail down due to the increased airflow from
the propeller. The
plowing position
creates high drag,
requiring a relatively large amount of power for a
modest gain in speed. Because of the higher r.p.m.,
the propeller may pick up spray even though the nose
is high. The higher engine power combined with low
cooling airflow creates a danger of heat buildup in the
engine. Monitor engine temperature carefully to avoid
overheating. Taxiing in the plowing position is not
recommended. It is usually just the transitional phase
between idle taxi and planing. [Figure 4-6]
PLANING OR STEP POSITION
In the planing position , most of the seaplane’s weight
is supported by hydrodynamic lift rather than the
buoyancy of the floats. (Because of the wing’s speed
through the air, aerodynamic lift may also be support-
ing some of the weight of the seaplane.)
Hydrodynamic lift depends on movement through the
water, like a water ski. As the float moves faster
through the water, it becomes possible to change the
pitch attitude to raise the rear portions of the floats
clear of the water. This greatly reduces water drag,
allowing the seaplane to accelerate to lift-off speed.
This position is most often called
on the step
. [Figure
4-7]
There is one pitch attitude that produces the minimum
amount of drag when the seaplane is on the step. An
experienced seaplane pilot can easily find this “sweet
spot” or “slick spot” by the feel of the floats on the
water, but the beginning seaplane pilot usually needs
to rely on gauging the position of the nose on the hori-
zon. If the nose is considerably high, the rear portions
of the floats contact the water, drag increases, and the
Figure 4-5. Idling position.The engine is at idle r.p.m., the seaplane moves slowly, the attitude is nearly level, and buoyancy sup-
ports the seaplane.
Figure 4-6. Plowing position.
Ch 04.qxd 10/25/04 2:01 PM Page 4-4
seaplane tends to start settling back into more of a
plowing position. If the nose is held only slightly
higher than the ideal planing attitude, the seaplane
may remain on the step but take much longer to accel-
erate to rotation speed. On the other hand, if the nose
is too low, more of the front portion of the float con-
tacts the water, creating more drag. This condition is
called dragging, and as the nose pulls down and the
seaplane begins to slow, it can sometimes feel similar
to applying the brakes in a landplane.
To continue to taxi on the step instead of taking off,
reduce the power as the seaplane is eased over onto the
step. More power is required to taxi with a heavy load.
However, 65 to 70 percent of maximum power is a
good starting point.
Taxiing on the step is a useful technique for covering
long distances on the water. Carefully reducing power
as the seaplane comes onto the step stops acceleration
so that the seaplane maintains a high speed across the
water, but remains well below flying speed. At these
speeds, the water rudders must be retracted to prevent
damage, but there is plenty of airflow for the air rudder.
With the seaplane on the step, gentle turns can be made
by using the air rudder and the ailerons, always main-
taining a precise planing attitude with elevator. The
ailerons are positioned into the turn, except when
aileron into the wind is needed to keep the upwind wing
from lifting.
Step taxiing should only be attempted in areas where the
pilot is confident there is sufficient water depth, no float-
ing debris, no hidden obstructions, and no other water
traffic nearby. It can be difficult to spot floating hazards
at high speeds, and an encounter with a floating log or
other obstruction could tear open a float. Your seaplane
is not as maneuverable as craft that were designed for
the water, so avoiding other vessels is much more diffi-
cult. Besides the obvious danger of co llision, other
water traffic creates dangerous wakes, which are a
much more frequent cause of damage. If you see that
you are going to cross a wake, reduce power to idle
and idle taxi across it, preferably at an angle. Never
try to step taxi in shallow water. If the floats touch
bottom at high speed, the sudden drag is likely to flip
the seaplane.
From either the plowing or the step position, when
power is reduced to idle, the seaplane decelerates quite
rapidly and eventually assumes the displacement or
idle position. Be careful to use proper flight control
pressures during the deceleration phase because as
weight is transferred toward the front of the floats and
drag increases, some seaplanes have a tendency to nose
over. Control this with proper use of the elevator.
TURNS
At low speeds and in light winds, make turns using the
water rudders, which move in conjunction with the air
rudder. As with a landplane, the ailerons should be
positioned to minimize the possibility of the wind lift-
ing a wing. In most airplanes, left turns are somewhat
easier and can be made tighter than right turns because
of torque. If water rudders have the proper amount of
movement, most seaplanes can be turned within a
radius less than the span of the wing in calm conditions
or a light breeze. Water rudders are usually more effec-
tive at slow speeds because they are acting in compar-
atively undisturbed water. At higher speeds, the stern
of the float churns the adjacent water, causing the water
rudder to become less effective. The dynamic pressure
of the water at high speeds may tend to force the water
rudders to swing up or retract, and the pounding can
cause damage. For these reasons, water rudders should
be retracted whenever the seaplane is moving at high
speed.
The weathervaning tendency is more evident in seaplanes,
and the taxiing seaplane pilot must be constantly aware of
the wind’s effect on the ability to maneuver. In stronger
winds, weathervaning forces may make it difficult to turn
Figure 4-7. On the step. The attitude is nearly level, and the weight of the seaplane is supported mostly by hydrodynamic lift.
Behind the step, the floats are essentially clear of the water.
Ch 04.qxd 8/24/04 10:48 AM Page 4-5
downwind. Often a short burst of power provides suf-
ficient air over the rudder to overcome weathervan-
ing. Since the elevator is held all the way up, the
airflow also forces the tail down, making the water
rudders more effective. Short bursts of power are
preferable to a longer, continuous power application.
With continuous power, the seaplane accelerates,
increasing the turn radius. The churning of the water
in the wake of the floats also makes the water rudders
less effective. At the same time, low cooling airflow
may cause the engine to heat up.
During a high speed taxiing turn, centrifugal force
tends to tip the seaplane toward the outside of the turn.
When turning from an upwind heading to a downwind
heading, the wind force acts in opposition to centrifu-
gal force, helping stabilize the seaplane. On the other
hand, when turning from downwind to upwind, the
wind force against the fuselage and the underside of
the wing increases the tendency for the seaplane to lean
to the outside of the turn, forcing the downwind float
deeper into the water. In a tight turn or in strong winds,
the combination of these two forces may be sufficient
to tip the seaplane to the extent that the downwind float
submerges or the outside wing drags in the water, and
may even flip the seaplane onto its back. The further
the seaplane tips, the greater the effect of the cross-
wind, as the wing presents more vertical area to the
wind force. [Figure 4-8]
When making a turn into the wind from a crosswind
condition, often all that is necessary to complete the
turn is to neutralize the air rudder and allow the sea-
plane to weathervane into the wind. If taxiing directly
downwind, use the air rudder momentarily to get the
turn started, then let the wind complete the turn.
Sometimes opposite rudder may be needed to control
the rate of turn.
Stronger winds may make turns from upwind to down-
wind more difficult. The plow turn is one technique for
turning downwind when other methods are inadequate,
but this maneuver is only effective in certain seaplanes.
It takes advantage of the same factor that reduces a
floatplane’s yaw stability in flight: the large vertical area
of the floats forward of the center of gravity. In the
plowing attitude, the front portion of each float comes
out of the water, presenting a large vertical surface for
the wind to act upon. This tends to neutralize the weath-
ervaning force, allowing the turn to proceed. At the
same time, the center of buoyancy shifts back. Since
this is the axis around which the seaplane pivots while
Wind Force
Centrifugal
Force
Wind Force
Centrifugal
Force
Centrifugal
Force
Wind
Force
Centrifugal
Force
Wind
Force
Figure 4-8. Wind effects in turns. When the wind and centrifugal force act in the same direction, the downwind float can be
forced underwater. When the wind is countered by centrifugal force, the seaplane is more stable.
Ch 04.qxd 8/24/04 10:49 AM Page 4-6
on the water, more of the fuselage is now forward of
the axis and less is behind, further decreasing the
weathervaning tendency. In some seaplanes, this
change is so pronounced in the plowing attitude that
they experience reverse weathervaning, and tend to
turn downwind rather than into the wind. Experienced
seaplane pilots can sometimes use the throttle as a
turning device in high wind conditions by increasing
power to cause a nose-up position when turning down-
wind, and decreasing power to allow the seaplane to
weathervane into the wind. [Figure 4-9]
To execute a plow turn, begin with a turn to the right,
then use the weathervaning force combined with full
left rudder to turn back to the left. As the seaplane
passes its original upwind heading, add enough power
to place it into the plow position, continuing the turn
with the rudder. As the seaplane comes to the down-
wind heading, reduce power and return to an idle taxi.
From above, the path of the turn looks like a question
mark. [Figure 4-10]
Plow turns are useful only in very limited situations
because they expose the pilot to a number of potential
dangers. They should not be attempted in rough water
or gusty conditions. Floatplanes are least stable when
in the plowing attitude, and are very susceptible to
capsizing. In spite of the nose-high attitude, the high
power setting often results in spray damage to the
propeller. In most windy situations, it is much safer
to sail the seaplane backward (as explained in the
next section) rather than attempt a plow turn.
When the seaplane is on the step, turns involve careful
balancing of several competing forces. As the rate of
turn increases, the floats are being forced to move
somewhat sideways through the water, and they resist
this sideways motion with drag, much like an airplane
fuselage in a skidding turn. More power is required to
overcome this drag and maintain planing speed. This
skidding force also tends to roll the seaplane toward
the outside of the turn, driving the outside float deeper
into the water and adding more drag on that side. To
prevent this, use aileron into the turn to keep the out-
side wing from dropping. Once full aileron into the
step turn is applied, any further roll to the outside can
only be stopped by reducing the rate of turn, so pay
careful attention to the angle of the wings and the feel
of the water drag on the floats to catch any indication
that the outside float is starting to submerge. When
stopping a step turn, always return to a straight path
before reducing power.
At step taxi speeds, the centrifugal force in a turn is far
greater than at idle taxi speed, so the forces involved in
turning from downwind to upwind are proportionately
more dangerous, especially in strong winds. Chances
are, by the time a pilot discovers that the outside float
is going under, the accident is almost inevitable.
However, immediate full rudder out of the turn and
power reduction may save the situation by reversing
Engine Idling
Water Rudder Down
Elevator Full Up
Add Power to Assume
Plowing Attitude.
Full Right Aileron
Elevator Full Up
Full Right Rudder
Full Left Aileron
Elevator Full Up
Full Left Rudder
Full Left Aileron
Elevator Full Up
Reduce Power to Idle
Rudder as Needed
to Maintain Heading
Full Left Rudder, Full Right Aileron,
Elevator Full Up
Figure 4-9. In the plowing position, the exposed area at the
front of the floats, combined with the rearward shift of the
center of buoyancy, can help to counteract the weathervan-
ing tendency.
Figure 4-10. Plow turn from upwind to downwind.
Ch 04.qxd 8/24/04 10:49 AM Page 4-7
the centrifugal force and allowing the buried float to
come up.
SAILING
Landplane pilots are accustomed to taxiing by pointing
the nose of the airplane in the desired direction and
rolling forward. In seaplane operations, there are often
occasions when it is easier and safer to move the seaplane
backward or to one side because wind, water conditions,
or limited space make it impractical to attempt a turn. If
there is a significant wind, a seaplane can be guided into
a space that might seem extremely cramped to an inexpe-
rienced pilot.
Sailing
is a method of guiding the seaplane
on the water using the wind as the main motive force. It is
a useful technique for maneuvering in situations where
conventional taxiing is undesirable or impossible. Since
the seaplane automatically aligns itself so the nose points
into the wind, sailing in a seaplane usually means moving
backward.
In light wind conditions with the engine idling or off, a
seaplane naturally weathervanes into the wind. If the
pilot uses the air rudder to swing the tail a few degrees,
the seaplane sails backward in the direction the tail is
pointed. This is due to the keel effect of the floats,
which tends to push the seaplane in the direction the
sterns of the floats are pointing. In this situation, lift the
water rudders, since their action is counter to what is
desired. When sailing like this, the sterns of the floats
have become the front, as far as the water is concerned,
but the rear portions of the floats are smaller and there-
fore not as buoyant. If the wind is strong and speed
starts to build up, the sterns of the floats could start to
submerge and dig into the water. Combined with the
lifting force of the wind over the wings, the seaplane
could conceivably flip over backward, so use full for-
ward elevator to keep the sterns of the floats up and
the seaplane’s nose down. Adding power can also
help keep the floats from submerging.
If enough engine power is used to exactly cancel the
backward motion caused by the wind, the seaplane is
not moving relative to the water, so keel effect disap-
pears. However, turning the fuselage a few degrees left
or right provides a surface for the wind to push against,
so the wind will drive the seaplane sideways in the
direction the nose is pointed. Combining these tech-
niques, a skilled pilot can sail a seaplane around obstacles
and into confined docking spaces. [Figure 4-11]
Figure 4-12 shows how to position the controls for the
desired direction of motion in light or strong winds.
With the engine off, lowering the wing flaps and open-
ing the cabin doors increases the air resistance and
thus adds to the effect of the wind. This increases sail-
ing speed but may reduce the effect of the air rudder. If
sailing with the engine off results in too much motion
downwind, but an idling engine produces too much
thrust, adding carburetor heat or turning off one mag-
neto can reduce the engine power slightly. Avoid using
carburetor heat or running on one magneto for
extended periods. Instead, start the engine briefly to
slow down.
Where currents are a factor, such as in strong tidal
flows or a fast flowing river, sailing techniques must
With Left Rudder and Left
Aileron Down, Seaplane
Moves Downwind to the Right
With Rudder and Ailerons
Neutral, Seaplane Moves
Straight Downwind
Engine Thrust to
Balance Wind Motion
With Right Rudder
and Right Aileron
Down, Seaplane
Moves Downwind
to the Left
Water
Rudders Up
Figure 4-11. When the seaplane moves through the water, keel effect drives it in the direction the tail is pointed. With no motion
through the water, the wind pressure on the fuselage pushes the seaplane toward the side the nose is pointed.