Army Aircraft Icing
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tial location and severity to at least 20 km ahead of an aircraft. This should
provide pilots with sufficient time to interpret cockpit displays and avoid the
conditions. NASA is evaluating a commercial, ground-based system built, in
part, with Army funding. NOAA is constructing a ground-based radar and radio-
meter system. An airborne system would probably serve Army aviation best
because the Army typically does not operate near airfields, especially in wartime
environments. ERDCCRREL is developing an aircraft-mounted radiometer
system, and NASA is developing an airborne radar system. Prototype systems
may be ready to fly within the next 510 years.
Preflight deicing
The questionnaires indicate that it can take up to six hours to deice Army
helicopters before flight. The Army has not developed standardized methods of
deicing entire helicopter airframes. As a result, if heated hangars are not avail-
able, units must use creative methods to prepare aircraft for flight after snow
or ice events. Though often effective, these methods typically require a large
amount of time, and have resulted in damage to airframe components and, most
seriously, composite rotor blades. A summary of blade deice procedures is given
in Appendix H.
ERDCCRREL has been evaluating and developing improved methods for
deicing Army helicopters before flight, with the goal of preparing a snow- or ice-
covered aircraft for flight within 3045 min. The two approaches to solving these
problems being explored are improved deicing fluids and thermal deicing.
Fluids used to deice commercial aircraft and military fixed-wing aircraft are
typically ethylene or propylene glycol-based. Ethylene glycol is toxic and is
hazardous to the environment. Propylene glycol is not toxic and is used, for
example, as a food additive and for skin care products. However, it is harmful to
the environment because it has a high biological oxygen demand (BOD). That is,
when it enters surface water supplies it degrades so rapidly that oxygen is de-
pleted sufficiently to injure aquatic life, and to drive water bodies to eutrophica-
tion. In addition, glycols may harm composite materials and emulsify greases.
Therefore, glycol deice fluids are banned by the Army for use on helicopter
rotorheads where grease could be washed from bearings, thus causing failure.
Industry is developing an environmentally friendly, helicopter-acceptable
deicing fluid that should be usable on Army helicopters, and which may not need
recovery to protect the environment. A common, organic chemical, sorbitol, has
been identified as the potential base stock for the new deicing fluid. Such a fluid,
if successful, could be applied to aircraft with a garden-type sprayer if
bivouacked, or applied with the Army's ACDS.
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