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is a slight crosswind. Another option is to find a lee area
(protected area), where there are no wind drifts and
land in this area.
Other problems that may be encountered are beaver
dams, houses, or other hidden obstructions that have
been covered with snow and have become invisible,
especially in flat lighting situations.
A condition known as “overflow” can present problems
on landing and takeoff. The overflow is water, in
a liquid state, that is cooled below its freezing point.
The moment a ski or any other part of the skiplane
touches this supercooled water, it freezes solid. As the
water freezes, it will provide a rapid deceleration.
Overflow may exist on frozen lakes and rivers with or
without snow cover. Thin ice also creates a problem
because it is not always obvious. It may be thick
enough to support a layer of snow or other material,
but not a skiplane.
It is easier to see obstacles on lakes and rivers that are
frozen without snow cover. Spider holes are ports
formed by escaping air from under the ice, forming a
weak area or bubble at the surface. These may or may
not support the skiplane. Avoid running over spider
holes.
Clear ice, under certain conditions, can be extremely
slick and will not allow directional control once the
aerodynamic controls become ineffective due to the
loss of airflow. This becomes critical in crosswind
landing conditions.
Avoid landing near the shoreline where rivers or sewer
lines empty into lakes. The ice is likely to be very thin
in those areas.
TUNDRA
Tundra is probably the least desirable landing surface
since most of the above hazards can exist. Tundra is
typically composed of small clumps of grass that can
support snow and make ridge lines invisible. They also
hide obstacles and obscure holes that may be too weak
to support skiplanes. Avoid tundra unless the area is
well known. [Figure 7-6]
LIGHTING
Pilots routinely encounter three general lighting
conditions when flying skiplanes. They are flat
lighting, whiteout, and nighttime. The implications
Figure 7-6.Tundra.
Ch 07.qxd 8/25/04 11:20 AM Page 7-6
7-7
of nighttime are obvious, and in the interest of
safety, night operations from unlighted airstrips are
not recommended.
Flat lighting is due to an overcast or broken sky
condition with intermittent sunlight. Hills, valleys, and
snow mounds take on varying shades of white, and may
appear taller, shorter, or wider than they really are. This
indirect lighting alters depth perception. The pilot may
not realize that depth perception has been compromised,
and this can cause serious consequences when
operating skiplanes near hilly terrain. When flat
lighting is encountered, avoid or discontinue flight
operations, especially at an unfamiliar strip.
Whiteout can occur when flying in a valley with both
walls obscured by snow or fog. Clear sky conditions
can exist, but references cannot be established.
Reference to attitude gyro instruments helps when this
condition is encountered. Climb out of the valley so
additional visual references can be established.
Takeoffs and landings should not be attempted under
flat lighting or whiteout conditions.
LANDINGS
Landing a skiplane is easy compared to landing
with wheels; however, for off-airport landings,
extra precautions are necessary. Be careful in
choosing a landing site. Before landing, evaluate
the site to be sure a safe departure will be possible.
Upon arriving at a prospective landing site, a pass
should be made over the landing area to determine
landing direction, and to determine if a safe approach
and landing can be completed. A trial landing should
be accomplished to determine the best approach, subsequent
departure path, and the quality of the surface.
To perform the trial landing, plan and configure for a
soft-field landing with a stable approach. Then perform
a gentle soft-field touchdown, controlled with
power, while remaining near takeoff speed for
approximately 600 to 800 feet, and then initiating a
go-around.
Atrial landing is very helpful in determining the depth
and consistency of the snow, evaluating surface conditions,
and looking for possible hazards. Be prepared to
go around if at any time the landing does not appear
normal or if a hazard appears. Do not attempt to land
if the ski paths from the trial landing turn black. This
indicates “overflow” water beneath the snow wetting
the tracks.
When landing on a level surface, and the wind can be
determined, make the landing into the wind. If landing
　
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