Seaplane Skiplane Flying Menu > Seaplane Operations ? Landings >Landing >Glassy
Flat, calm, glassy water certainly looks inviting
and may give the pilot a false sense of safety. By its nature,
glassy water indicates no wind, so there are no concerns about
which direction to land, no crosswind to consider, no weathervaning,
and obviously no rough water. Unfortunately, both the visual
and the physical characteristics of glassy water hold potential
hazards for complacent pilots. Consequently, this surface condition
is frequently more dangerous than it appears for a landing seaplane.
The visual aspects of glassy water make it
difficult to judge the seaplane’s height above the water.
The lack of surface features can make accurate depth perception
very difficult, even for experienced seaplane pilots. Without
adequate knowledge of the seaplane’sheight above the surface,
the pilot may flare too high or too low. Either case can lead
to an upset. If the seaplane flares too high and stalls, it
will pitch down, very likely hitting the water with the bows
of the floats and flipping over. If the pilot flares too late
or not at all, the seaplane may fly into the water at relatively
high speed, landing on the float bows, driving them underwater
and flipping the seaplane. [Figure 6-6]
Besides the lack of surface features, the smooth,
reflecting surface can lead to confusing illusions as clouds
or shore features are reproduced in stunning detail and full
color. When the water is crystal clear and glassy, the surface
itself is invisible, and pilots may inadvertently judge height
by using the bottom of the lake as a reference, rather than
the water surface.
The lack of surface texture also presents a
physical characteristic that adds slightly to the risk of glassy
water landings. A nice smooth touchdown can result in faster
deceleration than expected, for the same reason that the floats
seem to stick to the surface during glassy water takeoffs: there
is less turbulence and fewer air bubbles between the float bottoms
and the water, which effectively increases the wetted surface
area of the floats and causes higher drag forces. Naturally,
this sudden extra drag at touchdown tends to pull the nose down,
but if the pilot is expecting it and maintains the planing attitude
with appropriate back pressure, the tendency is easily controlled
and presents no problem.
There are some simple ways to overcome the
visual illusions and increase safety during glassy water landings.
Perhaps the simplest is to land near the shoreline, using the
features along the shore to gauge altitude. Be certain that
the water is sufficiently deep and free of obstructions by performing
a careful inspection from a safe altitude. Another technique
is to make the final approach over land, crossing the shoreline
at the lowest possible safe altitude so that a reliable height
reference is maintained to within a few feet of the water surface.
When adequate visual references are not available,
make glassy water landings by establishing a stable descent
in the landing attitude at a rate that will provide a positive,
but not excessive, contact with the water. Recognize the need
for this type of landing in ample time to set up the proper
final approach. Always perform glassy water landings with power.
Perform a normal approach, but prepare as though intending to
land at an altitude well above the surface. For example, in
a situation where a current altimeter setting is not available
and there are few visual cues, this altitude might be 200 feet
above the surface. Landing preparation includes completion of
the landing checklist and extension of flaps as recommended
by the manufacturer. The objective is to have the seaplane ready
to contact the water soon after it reaches the target altitude,
so at approximately 200 feet above the surface, raise the nose
to the attitude normally used for touchdown, and adjust the
power to provide a constant descent rate of no more than 150
feet per minute (f.p.m.) at an airspeed approximately 10 knots
above stall speed. Maintain this attitude, airspeed, and rate
of descent until the seaplane contacts the water. Once the landing
attitude and power setting are established, the airspeed and
descent rate should remain the same without further adjustment,
and the pilot shouldclosely monitor the instruments to maintain
this stable glide. Power should only be changed if the airspeed
or flare, but let the seaplane fly onto the water in the landing
attitude. [Figure 6-7]
Upon touchdown, apply gentle back pressure
to the elevator control to maintain the same pitch attitude.
Close the throttle only after the seaplane is firmly on the
water. Three cues provide verification through three different
senses—vision, hearing, and body sensation. The pilot
sees a slight nose-down pitch at touchdown and perhaps spray
thrown to the sides by the floats, hears the sound of the water
against the floats, and feels the deceleration force. Accidents
have resulted from cutting the power suddenly after the initial
touchdown. To the pilot’s surprise, a skip had taken place
and as the throttle closed, the seaplane was 10 to 15 feet in
the air and not on the water, resulting in a stall and substantial
damage. Be sure all of the cues
Figure 6-6. The consequences
of misjudging altitude over glassy water can be catastrophic.
Figure 6-7. Hold the
landing attitude, airspeed, and 150 f.p.m. rate of descent all
the way to the surface.
indicate that the seaplane is staying on the
water before closing the throttle. After the seaplane settles
into a displacement taxi, complete the after-landing checklist
and lower the water rudders.
An accurately set altimeter may allow the pilot
to set up for the touchdown at an altitude somewhat closer to
the surface. If the pilot can be certain that the landing configuration
and 150 f.p.m. descent will be established well above the water’s
surface, starting the final glide nearer the surface shortens
the descent time and overall landing length.
This technique usually produces a safe, comfortable
landing, but the long, shallow glide consumes considerable landing
distance. Be certain there is sufficient room for the glide,
touchdown, and water run.