DARTMOUTH, NS, Nov. 28, 2013 /CNW/ - The Transportation Safety Board of
Canada (TSB) today released its investigation report (A12A0085) into
the August 2012 engine failure and hard landing of a Bell 407
helicopter in Wabush, Newfoundland and Labrador.
On 12 August 2012, a Universal Helicopters Newfoundland Limited Bell 407
helicopter was slinging a drill tower approximately 4 nautical miles
southwest of Wabush, Newfoundland and Labrador. At around 1 p.m.
Atlantic Daylight Time, as the helicopter was approaching the drill
base frame, the engine lost power. The helicopter then immediately
descended and yawed to the left. The engine power loss occurred at an
altitude from which a safe landing could not be assured, resulting in
substantial helicopter damage; there was no post-crash fire. The pilot,
who was the sole occupant, sustained minor injuries and was able to
exit the aircraft.
The Bell 407 is powered by a single Rolls-Royce Corporation (RRC) Model
250-C47B turbine engine. A metallurgical examination of the occurrence
helicopter's engine revealed high-cycle fatigue (HCF) striations on 6
turbine wheel blades. One of these blades had an HCF crack, which
propagated about 0.40 inches before it separated in overstress. The
failure of the first blade led to a rapid failure of the turbine wheel
as the remaining blades separated in overstress due to impact with
Since April 2002, there have been 3 similar occurrences of HCF blade
failure on part number 6898663 third-stage turbine wheel installed in
the Model 250-C47B engines. At the time of this report, RRC has not
been able to specifically identify what engine operating condition, or
conditions, cause the tensile residual stresses to be induced at the
blade hub trailing edges.
The TSB is an independent agency that investigates marine, pipeline,
railway and aviation transportation occurrences. Its sole aim is the
advancement of transportation safety. It is not the function of the
Board to assign fault or determine civil or criminal liability.
SOURCE: Transportation Safety Board of Canada
For further information:
Transportation Safety Board of Canada
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