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COVER STORY
The primary effect of ice on a helicopter’s blades is drag and loss of lift. During
temperatures between 0 and -3C, ice will form on the leading edge from the root
outwards toward the tip, covering about 70% of the blade, as kinetic energy or the
heat from the blade tip inboard typically inhibits ice accumulation in that area.
root outwards toward the tip, covering a Land As Soon As Possible decision. ter is snow. Snow has caused many heli-
about 70% of the blade, as kinetic energy Icing conditions also pose a danger to copter accidents during takeoff and level
or the heat from the blade tip inboard typ- turbine engines. While many of our heli- flight, and during landings due to whiteout
ically inhibits ice accumulation in that copters have engine anti-ice systems, these conditions and loss of situational aware-
area. This kinetic energy benefit decreases systems are meant for light icing and ice ness. Prior to departing from a snow-cov-
with temperatures below -3C. Ice accu- may accumulate at the throat near the first ered ramp or helipad, whiteout should be
mulating on a blade will cause vibration – compressor stage. This in itself will not considered. In fresh snow, pulling just
from very slight to significant dependant cause the engine to fail or flameout, it is the enough pitch to become light on the land-
on the type of blade and the rate of accu- breaking of this ice and its being ingested ing gear can cause the snow to blow away
mulation. The increase in the torque re- into the engine that can cause damage and from the aircraft. Depending on the heli-
quired to sustain level flight is an posssible flameout. Engine manufactures copter model, I teach our flight crews to
indication of significant accumulation. If have conducted testing and found that as use the chin bubble as a reference point,
in icing conditions, it is helpful to know little as 350cc of water – at one time—into as it seems ground contact can often be
that the faster the helicopter is traveling, the engine can cause a flameout. Aircraft seen through this window during takeoff
the faster ice accumulates. Any indication with particle separators are less susceptible and landing even when a snow cloud is
of ice on typical law enforcement heli- to these engine induction hazards. obscuring the primary windows.
copters, any vibration, should be cause for Perhaps a more common danger in win- Off-site landings and takeoff’s pose a
problem of their own we must consider.
In addition to the whiteout described
above, landing in snow-covered fields can
become a dangerous situation as the snow
may be masking uneven terrain or haz-
ardous obstructions.
Similarly, landing on frozen snow can
be dangerous, as just after landing the
weight of the aircraft can break through the
frozen snow and in both cases the PIC may
not be ready for a slope situation that may
exceed the helicopter’s limitations. After
landing in a field, and sitting for some time,
when departing, a skid may freeze to the
ground and dynamic rollover situation may
occur. The best prevention during off-air-
port landings is to have a ground support
officer assist in assessing the landing area,
and in all cases, land slowly and treat each
snow covered landing and takeoff as you
would a slope landing.
The increased use of Night Vision Gog-
gles requires us to be ever vigilant of light
snow, as while flying with NVG’s in light
snow, the snow may only be seen as a
slight increase in the graininess or amount
of “visual static” in the goggles, thus al-
lowing us to see through light snow. As
we fly in remote country areas with ambi-
ent light sources few and far between, dur-
ing times of low moon illumination from
one second to the next, the snow can in-
crease and when viewed unaided we can
14 ROTORCRAFT PROFESSIONAL • Heli-Expo 2010 Preview Issue
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