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ERDC/CRREL TR-02-13
6
OVERCOMING ICING'S IMPACT
ON ARMY AVIATION OPERATIONS
As indicated, one reason for the very low accident rate of Army aircraft in
icing conditions is that strict regulations require that aircraft not fly in icing
conditions beyond the rating of the aircraft. However, the accident rate may be
potentially lowered, and Army's ability to fly more frequently in icing-prone
weather could be improved by a variety of technological improvements.
In-flight icing
Only two Army helicopters, the Black Hawk and the Apache AH-64A, have
blade deicing systems that allow them to fly in icing at the moderate severity
level and below. The newer Apache Longbow AH-64D does not have blade
deicing. The AH-64A deicing system was considered a maintenance headache,
was costly to repair, and was not considered very effective in icing conditions
according to interviews with pilots and aircrew. The Black Hawk deice system
has been included on all models of the helicopter, and will likely be maintained
on the upgraded UH-60M Black Hawk. It has been considered an effective
system according to most pilots and aircrews participating in this study.
Despite the success of the Black Hawk deicing system, there is a need for
improved blade deicing/anti-icing systems. The Black Hawk and Apache AH-
64A blade deicing systems are electrothermal. Blade leading edges are heated by
wires imbedded in the leading edge composite under the titanium wear strip.
Wires burn out, and if controllers fail, leading edges can overheat, causing
damage to composites and blade delamination. Leading edge damage from
excessive heat has been a problem for the Apache AH-64A. Major airframe
manufacturers, small businesses, and the National Rotorcraft Technology Center
and Rotorcraft Industry Technology Association (NRTC/RITA) are actively
seeking nonthermal solutions to helicopter blade deicing. However, it is unlikely
that blade deicing systems will be developed that will allow helicopters to fly
into any icing conditions with impunity. This is because other portions of the
aircraft that cannot be easily anti-iced or deiced, such as antennas and weapons
systems, will also ice. A helicopter that can fly in icing, but cannot prevent icing
of its antennas and weapons to avoid their being rendered nonfunctional,
becomes more susceptible to threats when arriving at the area of responsibility.
Traditionally, the most effective method of coping with icing conditions is to
avoid them. This is accomplished by using guidance provided by weather fore-
casts, or by detecting icing conditions ahead of aircraft from pilot reports. Icing
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