40
ERDC/CRREL TR-02-13
Results
The database was analyzed for several aspects of the icing problem,
including in-flight vs. ground icing, aircraft type (Table 16), accident location
(Table 17), and accident class (Table 18). Finally the icing accident data was
compared to the total Army aviation accident data during the same time period.
A. In-flight vs. ground.
Out of the 255 icing-related accidents and incidents, 160 occurred in flight
and the remaining 95 occurred on the ground. A common in-flight icing accident
in helicopters was damage to a whip antenna. For example, an AH60A flying out
of Grafenwohr AAF (Case No. 19981124009) reported the following:
"During instrument approach into Grafenwohr AAF, aircraft entered moder-
ate icing condition. Ice accumulated on no heated surfaces. Suspected that ice
accumulated on #1 whip antenna causing antenna to flex and eventually frac-
turing and fraying the antenna. Maintenance replaced antenna and released
aircraft to flight."
A typical ground icing accident was inadequate deicing before takeoff. For
example, this UH1 out of Fort Lewis WA (Case No. 19841212011) noted that
"Aircraft start, run up with no deficiencies noted. Aircraft lifted to hover for
taxi to take off. Pilot noted severe 1:1 lateral vibration and returned a/c to parking
and performed emergency shutdown procedures. Crew did not notice buildup of
clear ice on main rotor blade during preflight inspection."
In several other cases, snow and ice that collected on the aircraft while on the
ground later melted and refroze on control surfaces and other equipment.
B. Icing by aircraft type.
As shown in Table 16, helicopters account for two-thirds of the icing
accidents and incidents. Of these, three-quarters were attributed to the UH-1
Huey and the UH-60 Black Hawk, which were the two largest fleets in the Army
during the period of the study, and have many more flight hours. The Black
Hawk fleet flies over 40% of the rotary wing flight hours annually. However, the
most serious accident was the crash of an MH47E Chinook at Fort Campbell,
Kentucky, on 7 March 1997. It resulted in five fatalities and loss of the aircraft,
valued at ,478,835. This cost represents 92% of the total damage cost due to
icing over the FY85FY99 time period. According to the accident report, the
helicopter was flying through fog, gusty winds, snow, and moderate icing when it
crashed. These weather conditions are suspected to be a cause of the crash.
Previous Page
