SKIPLANE OPERATIONS
This chapter introduces pilots to the procedures
required in the operation of skiplanes. Since most
skiplane operations and training are conducted in
single-engine airplanes with a conventional gear
(tailwheel) configuration, this information is based
on operating skiplanes of this type. [Figure 7-1]
A skiplane configuration affects the overall operation
and performance of an airplane in several different
ways, including ground handling, takeoff, landing, and
flight operations. Some manufacturers provide recom-
mended procedures and performance data in the
Airplane Flight Manual (AFM) and/or Pilot’s
Operating Handbook (POH).
Title 14 of the Code of Federal Regulations (14 CFR)
part 61 does not require specific pilot training and
authorization to operate skiplanes; however, it is
important to train with a qualified skiplane flight
instructor.
Since most skiplanes operate in a wide variety of con-
ditions, such as landing on frozen or snow-covered
lakes and sloping glaciers, with varying qualities of
snow, it is important to know how performance is
affected. Use the performance data provided by the
manufacturer.
CONSTRUCTION AND MAINTENANCE
Modern airplane ski designs are a compromise for the
various forms and conditions of snow and ice. For
example, a long, wide ski is best for new fallen, pow-
dery, light snow, whereas a sharp, thin blade is best
for hard-packed snow or smooth ice. Many ski
designs feature a wide, flat ski with aluminum or steel
runners on the bottom. Airplane skis may be made
from composites, wood, or aluminum, and some have
a polyethylene plastic sheathing bonded or riveted to
the bottom surfaces. Ski designs fall into two main
categories: plain and combination. Plain skis can only
be used on snow and ice, while combination skis also
allow the wheels to be used to land on runways.
PLAIN SKI TYPES
•W heel Replacement— Wheels are removed and
ski boards are substituted. [Figure 7-2]
• Clamp-On— Skis that attach to the tires and
benefit from the additional shock absorbing
qualities of the tires.
• Roll-On or Full Board— Similar to the clamp-on
type except the tires are bypassed and do not carry
side or torque loads. Only the tire cushioning
effect is retained with this installation.
COMBINATION SKI TYPES
• Retractable Ski— Can be extended into place for
snow operations or retracted for non-snow opera-
tions. This is accomplished by either a hydraulic
pump or crank.
Figure 7-1. Skiplane.
Figure 7-2. Wheel replacement ski.
Ch 07.qxd 8/25/04 11:20 AM Page 7-1
•P enetration Ski— The wheel extends down par-
tially below the ski, allowing the skiplane to
operate from both snow and non-snow surfaces.
This type of ski gives poor ground clearance on
non-snow surfaces and causes extra drag when
on snow. [Figure 7-3]
The plastic polyethylene sheathing on the bottoms of
the skis may be punctured by sharp objects, including
ice. It also may shatter from impacts in extremely cold
temperatures. Replacing the bonded type sheathing is
very difficult in the field. If the sheathing is riveted,
machine screws may be used to secure loose sheathing,
but the screw holes must provide for expansion and
contraction. Follow the manufacturer’s recommen-
dations for patching limited sheathing damage. If
damage is extensive, the entire ski bottom may need
new covering.
Shock cord bungees used in ski rigging deteriorate
rapidly when left under tension. When parking the
skiplane overnight, detach the bungees at the lower
fitting and allow them to hang free. Reattaching the
bungees normally requires two or more people.
Hydraulic ski retracting mechanisms usually function
well in cold environments, but the small, abrupt change
of ski attitude occurring at touchdown imposes a severe
load on the external hydraulic lines leading to the skis.
These lines are a more prevalent source of trouble than
the internal parts.
Use low temperature oils and greases to lubricate fric-
tion points. For lubrication requirements, see the
AFM/POH or the ski manufacturer’s manual.
The condition of the limiting cables and their fasten-
ings is important to safety in flight. Be sure there is no
fraying, kinking, rusting, or other defective condition
before each flight.
OPERATIONAL CONSIDERATIONS
In the air, skiplane flight characteristics are similar to
those of airplanes with standard landing gear, except
for a slight reduction in cruising speed and range.
Leaving the skis in the extended position in flight pro-
duces no adverse effect on trim, but may cause a slight
loss of speed. Consult the operator’s manual for
skiplane performance data, and weight and center of
gravity considerations.
The AFM/POH skiplane supplement may provide lim-
itations including limiting airspeeds for operation with
skis in flight and for other wheel/ski configurations.
These speeds may be different from the wheel-type
landing gear configuration, depending on the type of
ski and the tension of the springs or bungees holding
the fronts of the skis up.
Understand both the limitations and advantages of the
ski equipment. Compared to the standard wheel
equipped airplane that incorporates individual brakes
for steering, skis are clumsy and the airplane is less
maneuverable while on the ground. Like a floatplane,
a skiplane has a tendency to weathervane with the
wind and needs considerable space to maneuver.
Maneuvering on the ground and parking require spe-
cial techniques which are acquired only through
practice.
TYPES OF SNOW
•P owder Snow— Dry snow in which the water
content and ambient temperature are low.
•W et Snow— Contains high moisture and is
associated with warmer temperatures near the
freezing point.
•G ranular Snow— Wet snow that has had a
temperature drop causing the snow to ball up
and/or crust.
TYPES OF ICE
•G laze Ice— Snow that has been packed down and
frozen to a solid ice pack, or frozen snow.
•G lare Ice— A smooth sheet of ice that is exceed-
ingly slippery with no deformities, cracks, or
other irregularities in the surface. This ice lacks
any kind of traction, with a coefficient of friction
near zero.
• Clear Ice— Ice that forms smoothly over a sur-
face and has a transparent appearance.
Figure 7-3. Penetration ski.
Ch 07.qxd 8/25/04 11:20 AM Page 7-2
attracting attention and signaling for help in both
daylight and darkness; and treatment of injuries.
Obtain appropriate survival training and know how
to make effective use of the equipment. Whether the
cause is a forced landing or an engine that fails to
restart after landing at a remote location, the survival
gear and clothing should keep the pilot and passen-
gers alive until help arrives.
When planning for an overnight stay away from an air-
port, or if the skiplane is routinely parked outside, other
items may be added to the equipment carried on the
skiplane. These might include portable tiedowns, a
flashlight, a shovel, and a broom. Wing and fuselage
covers can prevent the buildup of frost and snow, sim-
plifying the preflight. In temperatures below 0 ° F, an
engine cover and a catalytic heater may be necessary to
preheat the engine compartment. If the pilot carries
appropriate hand tools and a bucket, the crankcase oil
can be drained from the engine and kept indoors. It may
also be helpful to remove the battery and keep it in a
warmer location. Many pilots carry burlap sacks, plastic
garbage bags, or wooden slats to place under the skis to
prevent them from freezing to the surface. Some carry a
can of non-stick cooking spray to use on the bottom of
the ski to avoid sticking or freezing to the surface.
Depending on the needs of the skiplane, it may be nec-
essary to carry extra engine oil, hydraulic fluid, or
deicer fluid. Markers such as red rags, colored flags, or
glow sticks may come in handy, as well as 50 feet of
nylon rope, and an ice pick or ice drill. Select equip-
ment according to the situation, and know how to use it.
If a skiplane has been sitting outside overnight, the
most important preflight issues are to ensure that the
airframe is free of snow, ice, and frost and that the skis
are not frozen to the ground. Often, while sitting on
the ground, precipitation may fall and cover the
skiplane. Temperatures on the ground may be slightly
colder than in the air from which the precipitation
falls. When liquid precipitation contacts the colder air-
craft structure, it can freeze into a coating of clear ice,
which must be removed completely before flight.
Wing and tail surfaces must be completely frost free.
Any frost, ice, or snow destroys lift and also can cause
aileron or elevator flutter. Aerodynamic flutter is
extremely dangerous and can cause loss of control or
structural failure.
The preflight inspection consists of the standard aircraft
inspection and includes additional items associated with
the skis. The AFM or POH contains the appropriate
supplements and additional inspection criteria. Typical
inspection criteria include:
• Skis— Examine the skis for damage, delamina-
tion, sheathing security, and overall condition.
SURFACE ENVIRONMENTS
• Glaciers— Sloping snow or ice packs.
•F r o z en Lakes— Frozen bodies of water with or
without snow cover.
•T undra— A large area of grass clumps support-
ing snow cover.
PREFLIGHT
Before departing on any trip, it is important to do
proper preflight planning. A good preflight should
include a review of the proposed route as well as
possible alternate routes; terrain; local, en route, and
destination weather; fuel requirements; facilities
available at the destination; weight and balance; and
takeoff and landing distance requirements.
Obtain a complete weather briefing for each leg, and
file a flight plan with appropriate remarks. For local
flights, always inform someone at home of the area of
operation and the expected time of return if a flight
plan is not filed.
Include good Aeronautical Decision Making (ADM)
procedures, such as running a personal minimums
checklist, and think PA VE (Pilot, Aircraft,
Environment, and External Pressures) during the
preflight phase.
Cold weather is implicit in flying a skiplane, so
preflight planning must also include preparations
for possible contingencies unique to cold weather
operations. This is especially important for flights
in bush country, where facilities are scarce and
emergency assistance may be limited or nonexistent.
Evaluate all passengers’ clothing for suitability in the
conditions expected. Consider the passenger when
making this evaluation. Children and older people need
more protection from the environment than a middle-
aged person in good health. Every occupant should be
dressed for a long walk, including adequate boots or
rubber-bottomed shoes and an arctic parka. Sunglasses
are highly recommended, even on cloudy days. Pilots
can be blinded by the brightness of the snow, and glare
can destroy depth perception.
Survival equipment is required by some states and
countries, and many areas require specific items for
even the shortest local flights. The requirements usu-
ally vary between winter and summer months. Be sure
to check the current requirements for the particular
jurisdiction. Beyond the minimum requirements, use
good judgment to select and carry any other equipment
that could help occupants survive an unplanned stay in
the specific terrain and environmental conditions along
the route of flight. Always consider means of provid-
ing warmth, shelter, water, and food; methods of
Ch 07.qxd 8/25/04 11:20 AM Page 7-3
• Hardware— Inspect the condition and security
of the clamping bolts, cotter keys, diaper pins,
limiting cables, and bungees. Be sure cables and
bungees are adjusted properly.
• Retracting Mechanism— (if equipped)—Check
the hydraulic fluid level and examine the
hydraulic lines for leaks. Inspect all cables for
fraying and check cable ends for security. Do not
cycle the retracting mechanism while on the
ground.
• Ski Freedom— Be sure the skis are free to move
and are not frozen to the surface. If the ambient
temperature approaches the melting point, the
skis can be freed easily. Gentle swinging of the
tail at the rear fuselage, or rocking the airplane at
the struts may free the skis. If this does not work,
dig the skis out.
•T ire Pressure— Check the tire pressure when
using skis that depend on the tires for shock
absorption, as well as for combination skis. This
is especially important if moving a skiplane from
a warm hangar to cold temperatures outdoors, as
tires typically lose one pound of pressure for
every ten-degree drop in ambient temperature.
•T ailwheel— Check the tailwheel spring and tail
ski for security, cracks, and signs of failure.
Without a tail ski, the entire tailwheel and rudder
assembly can be easily damaged.
• Fuel Sump— During fuel sump checks, some-
times moisture can freeze a drain valve open,
allowing fuel to continue to drain. Ice inside the
fuel tank could break loose in flight and block
fuel lines causing fuel starvation. If the manufac-
turer recommends the use of anti-icing additives
for the fuel system during cold weather opera-
tions, follow the ratio and mixing instructions
exactly.
• Survival Equipment— Check that all required
survival equipment is on board and in good con-
dition.
STARTING
Adequately preheat the engine, battery, and the cockpit
instruments before startup and departure. Sometimes
engine oil may require heating separately. Check the
manufacturer’s recommendation for starting the
engine when ambient temperatures are below freezing.
Batteries require special consideration. In cold climates
a strong, fully charged battery is needed. With just a lit-
tle cold-soaking, the engine may require three times the
usual amperage to crank the engine.
Another consideration is the electrolyte freezing point. A
fully charged battery can withstand temperatures of -60
to -90° F since the electrolyte’s specific gravity is at a
proper level. Conversely, the electrolyte in a weak or
discharged battery may freeze at temperatures near 32°
F. If a fully charged battery is depleted by an unsuccess-
ful start, it may freeze as it cools to ambient
temperature. Later, when the engine is started and the
battery is receiving a charge, it could explode.
After start, a proper warmup should be completed
prior to a runup and high power settings. Perform
the warmup according to the engine manufac-
turer’s recommendations. Some manufacturers
recommend a minimum of 1,000 r.p.m. to ensure
adequate lubrication.
If the skiplane is parked on heavily crusted snow or
glaze ice with the skis frozen to the surface, it may be
possible to start the engine and perform the runup in
the parking area. Be sure the area behind the skiplane
is clear, so as not to cause damage with the propeller
wash. If a ski should become unstuck during the
runup, reduce power immediately. Then use one of the
following procedures to secure the airplane.
Tie down or chock the skiplane prior to engine start,
warmup, and runup. Keep all ropes, bags, etc., clear of
the propeller. After warmup is complete, and if no
assistance is available, shut down the engine to untie
and unchock the skiplane, then restart as quickly as
possible. If a post, tree, boulder, or other suitable
object is available, tie a rope to an accessible structural
component in the cockpit, take the end around the
anchor object, bring it back to the cockpit, and tie it off
with a quick-release knot. When the warmup and
runup are complete, release the knot and pull the rope
into the cockpit as the skiplane begins to taxi.
If tiedowns or chocks are not available, build small
mounds of snow in front of each ski. The mounds must
be large enough to prevent the skiplane from taxiing
over them during engine start and warmup, but small
enough to allow taxiing when power is applied after
the warmup is complete. If tiedowns or means to block
the skis are not available, the runup can be accom-
plished while taxiing when clear of obstacles or other
hazards. [Figure 7-4]
Figure 7-4. Engine warmup.
Ch 07.qxd 8/25/04 11:20 AM Page 7-4
TAXIING
Taxiing a skiplane on snow and ice presents some
unusual challenges. With little or no brakes for stop-
ping or turning, and the ability to skid sideways, a
skiplane normally requires more maneuvering room
and space to turn than an airplane with wheels.
The tailwheel ski provides marginal directional control
on ice and hard packed snow. In such conditions, direc-
tional control comes from airflow over the rudder.
Adding power and forward elevator control pressure
can often help turn the skiplane. The goal is to lighten
the tail to help the turn without putting the skiplane on
its nose.
Taxiing in strong crosswinds can be difficult. Skiplanes
tend to weathervane into the wind. Drifting sideways in
the direction of the wind is also commonplace. Taxi in
a skid or let the skiplane weathervane partly into the
wind during crosswind operations to compensate.
[Figure 7-5] A short blast of power may be required to
turn the skiplane from upwind to downwind. It is nor-
mal to drift sideways in turns. Preplan the taxi track so
as to remain clear of drifts, ridges, or other
obstructions.
When taxiing in crosswinds on glare ice, get a helper at
each wingtip to help with turns and aligning the
skiplane for takeoff.
As a general rule, power settings and taxi speeds should
be kept as low as possible on ice or crusted snow. On
loose or powder snow, add enough power to maintain
forward motion and keep the skis on top of the snow.
The skiplane may even be step-taxied in a manner sim-
ilar to a floatplane, staying below takeoff speed. If the
skiplane is allowed to sink into soft snow, it may stop
moving and become stuck. When the snow is wet and
sticky, work the rudder and elevator to get the skiplane
moving and maintain forward motion to prevent the
skis from sticking again. If the skis are freed during
preflight, but stick again before starting the engine and
beginning to taxi, free the skis again and pull the
skiplane onto tree branches, leaves, or anything that
will prevent the skis from sticking. Burlap bags can
be used by tying a line to the bags and pulling them
into the cockpit after the skiplane has taxied forward.
Keep all ropes, bags, etc., clear of the propeller. Rapid
rudder movement will usually break the skis free if
they begin to stick during a slow taxi. Use a short
blast of power to create more airflow over the tail. A
thin coat of engine oil or non-stick cooking spray also
prevents sticking if the bottoms of the skis are easily
accessed.
At some snow-covered airports, airport managers or
fixed base operators spray red or purple dye onto taxi
routes and snow banks as visual aids. They may even
imbed pine boughs in the snow at regular intervals to
help define taxiways and runways or mark hazardous
areas. These helpful aids simplify ground operations
and improve safety.
TAKEOFFS
Since skiplanes operate from a variety of surfaces, it is
important to remember that many takeoff areas can
contain unforeseen hazards; therefore, it is important to
always plan for the unexpected.
If the condition of the takeoff path is unknown, walk
or taxi the full length of the takeoff area and back to
check the surface for hazards and help pack the snow.
It is better to discover any irregularities before
attempting a takeoff than to encounter them at high
speeds during takeoff.
Most takeoff distances are greater on snow than for
wheel-equipped airplanes on cleared runways and
other hard surfaces. On wet or powder snow, two or
three times the normal distance may be required. Be
sure to remove any frost or crusted snow from the skis
before takeoff. Such accumulations increase drag and
weight, resulting in a greater takeoff distance.
Select a takeoff direction that provides an adequate
distance to lift off and clear any obstructions. Use
headwinds or a downhill slope for takeoff when
possible to ensure best performance. When turning into
the wind, keep moving and turn in a wide arc. Trying to
turn too sharply can cause a ski to dig in, resulting in a
groundloop or noseover.
Plan and configure for a soft-field takeoff. Soft-field
procedures are recommended because the lack of
contrast and surface detail or glare off snow or ice
may hide possible hazards. Undetected drifts or soft
sticky spots can cause sudden deceleration and even
a possible noseover.
Direction
of Movement
Figure 7-5. Crosswind taxi.
Ch 07.qxd 8/25/04 11:20 AM Page 7-5
When lining up to depart, have the skiplane configured
properly and keep moving. Do not stop before adding
takeoff power because the skiplane may settle into soft
snow and limit acceleration. If this happens, it may be
necessary to taxi the takeoff path again to pack the
snow.
Crosswind takeoffs require the standard procedures and
techniques. Be aware that the skiplane may be sliding
in a crab during takeoff acceleration. On glaze ice an
increase in lateral drift may be seen on takeoff.
OFF-AIRPORT LANDING SITES
Landings on unprepared areas can be accomplished
safely if the proper precautions are followed.
Evaluating each new landing site thoroughly, obtaining
advice from well-qualified pilots already familiar with
the area, and staying within the limitations of personal
skill and experience can all contribute to safety and
reduce risks.
GLACIERS
There are a number of factors that must be consid-
ered when operating from glaciers. There can be
many hidden hazards.
The first consideration is the condition of the snow and
its suitability for landing. To evaluate a new area, fly
downhill with the skis on the surface, just touching the
snow, as slowly as possible above stall speed. This
helps determine the snow condition. If unsure of the
quality of the snowpack, look for a gentle slope and
land up the slope or hill. This situation will allow the
airplane to accelerate easily on a downslope takeoff.
If the slope angle of the landing area is very steep,
always evaluate the area for the possibility of an ava-
lanche. Avoid landing near the bottom of a valley
because ice falls may exist and provide rough and
unusable terrain.
Glaciers are very deceptive. It is advisable to train with
an experienced glacier pilot and become comfortable
before departing alone. Use extreme caution, as just a
few clouds overhead can totally change the picture of
the intended landing area.
LAKES AND RIVERS
Snow-covered frozen lakes and rivers can provide a
number of obstacles. Wind causes snow to form into
ripple-shaped wind drifts. Wind also breaks snow into
smaller particles, which bond quickly together to form
solid ridges. These ridges can be so rough that they can
damage or destroy the landing gear and skiplane. The
best plan is to land parallel to ridge rows, even if there
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 prob-
lems 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
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 compro-
mised, 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, sub-
sequent 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 per-
form 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.
A trial landing is very helpful in determining the depth
and consistency of the snow, evaluating surface condi-
tions, 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
on a slope, an uphill landing is recommended. To
avoid a hard landing, fly the skiplane all the way to the
surface and add some power just before touchdown.
Be sure to turn the skiplane crosswise to the slope
before it stops. Otherwise it may slide backward down
the slope.
When using combination skis to land on solid ice with-
out the benefit of snow, it is better to land with the
wheels extended through the skis to improve the ground
handling characteristics. Solid or clear ice surfaces
require a much greater landing distance due to the lack
of friction. The skiplane also needs more area for turns
when taxiing. If the surface has little or no friction, con-
sider the possibility of a groundloop, since the center of
gravity is typically behind the main skis and the tail ski
may not resist side movement. Keep the skiplane
straight during the runout, and be ready to use a burst of
power to provide airflow over the rudder to maintain
directional control.
Under bright sun conditions and without brush or trees
for contrast, glare may restrict vision and make it diffi-
cult to identify snowdrifts and hazards. Glare can also
impair depth perception, so it is usually best to plan a
soft-field landing when landing off airports.
After touchdown on soft snow, use additional power to
keep the skiplane moving while taxiing to a suitable
parking area and turning the skiplane around. Taxi
slowly after landing to allow the skis to cool down prior
to stopping. Even though they are moving against cold
surfaces, skis warm up a few degrees from the friction
and pressure against the surface. Warm skis could thaw
the snow beneath them when parked, causing the skis to
freeze to the surface when they eventually cool.
PARKING/POSTFLIGHT
Skiplanes do not have any parking brakes and will
slide on inclines or sloping surfaces. Park perpendicu-
lar to the incline and be prepared to block or chock the
skis to prevent movement.
When parked directly on ice or snow, skis may freeze
to the surface and become very difficult to free. This
happens when there is liquid water under the skis that
subsequently freezes. If both the surface and the skis
are well below freezing, there will be no problem, but
if the skis are warm when the airplane stops, they melt
the surface slightly, then the surface refreezes as the
heat flows into the ground. Similarly, the weight of
the skiplane places pressure on the skis, and pressure
generates heat. If the ambient temperature goes up to
just below freezing, the heat of pressure can melt the
surface under the skis. Then as the temperature drops
again, the skis become stuck.
If parking for a considerable amount of time, support
the skis above the snow to prevent them from sticking
or freezing to the surface. Place tree boughs, wood
slats, or other materials under the skis to help prevent
Ch 07.qxd 8/25/04 11:20 AM Page 7-7
them from becoming frozen to the surface. [Figure 7-7]
Some pilots apply a coat of non-stick cooking spray or
engine oil to the polypropylene ski surface to prevent
ice or snow from sticking during the next takeoff.
If the skis are the retractable type and the frozen sur-
face will support the wheels, place the skis in the UP
position. Next, dig the snow out from around the skis
until ready to depart. This keeps the skis away from
the surface. When parking on a hill, pay attention to
the position of the fuel selector valve. Typically, the
uphill tank should be selected to prevent fuel from
transferring to the lower wing and subsequently
venting overboard.
EMERGENCY OPERATIONS
When operating a skiplane, carry an adequate survival
kit. A good rule of thumb is to carry what is needed to
be comfortable. Alaska, Canada, and Sweden provide
lists on the internet of the survival equipment required
for flights in northern areas. In addition to communi-
cating the current requirements for specific
jurisdictions, these lists can help pilots choose
additional equipment to meet their needs, beyond the
minimum required. Also be sure to check for any
restrictions on the carriage of firearms if they are part
of your survival kit.
SKI MALFUNCTION
If skis are not rigged properly, or when recommended
airspeeds are exceeded, it is possible that a ski will tuck
down and give a momentary downward rotation of the
nose of the skiplane. This is generally caused by spring
or bungee tension not being sufficient to hold ski tips
up. The immediate fix is to reduce power and reduce
the speed of the skiplane. When the air loads are
decreased below the tension of the spring or bungee,
the ski will pitch back into place and the control prob-
lem will go away. Have a maintenance shop correctly
adjust the spring or bungee tension and avoid exceed-
ing the speed limits specified for the skis.
A precautionary landing may be necessary for events
such as a broken ski cable or broken hydraulic line. If a
ski cable breaks, the front of the ski will tip down. This
creates an asymmetrical drag situation, similar to a
large speed brake on one side of the skiplane. This con-
dition is controllable; however, it will take skill to
maintain control. Not only does the tilted ski create a
lot of drag, it also complicates the landing, since the
front of the ski will dig in as it contacts the surface,
causing abrupt deceleration and severe damage to the
landing gear. If efforts to get the ski into a stream-
lined position fail, a landing should be made as soon
as practical.
To attempt to streamline the ski, slow to maneuvering
speed or less. It may be possible for a passenger to use a
long rod such as a broom handle to push down on the
back end of the ski, aligning it with the airflow and mak-
ing possible a relatively normal landing. If the skis are
retractable, try to ensure that they are both in the UP posi-
tion (for a pavement landing) and land on pavement.
If it is not possible to get the ski to trail correctly, the
skiplane must be landed in such a way as to minimize
danger to the occupants. This usually means trying to
land so that the hanging ski breaks off quickly rather
than digging in and possibly destroying the skiplane. Fly
to an area where help is available, since damage is virtu-
ally inevitable. It is often best to land on a hard surface
to increase the chances of the ski breaking away.
With a broken hydraulic line, a condition of one ski up
and one ski down may develop. Again, the skiplane is
controllable with proper rudder and braking technique.
NIGHT EMERGENCY LANDING
A night landing should never be attempted at an unfa-
miliar location except in an emergency. To increase
the likelihood of a successful landing, perform the
checklist appropriate for the emergency, and unlatch
the doors prior to landing to prevent jamming due to
airframe distortion in the event of a hard landing. If
time permits, make distress calls and activate the
emergency locator transmitter (ELT).
When selecting a landing area, frozen lakes and rivers
are a good choice if the ice is thick enough to support
the aircraft. If the ice is thin or the thickness unknown,
a landing in an open field would be a better option.
After selecting a landing area, perform a reconnais-
sance and look for obstructions, field condition, wind
direction, and snow conditions if possible. Fly over the
landing area in the intended direction of touchdown and
drop glow sticks 2 seconds apart along the length of the
touchdown zone. Use the glow sticks to aid in depth per-
ception during final approach. Make the touchdown
with power, if available, and as slow as possible.
Figure 7-7. Supporting the skis above the surface prevents
them from freezing in place.