Engine failure caused August 2012 crash of a Bell 407 helicopter in Wabush, Newfoundland and Labrador

Engine failure caused August 2012 crash of a Bell 407 helicopter in Wabush, 
Newfoundland and Labrador 
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 4nautical miles 
southwest of Wabush, Newfoundland and Labrador. At around 1p.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 
0.40inches 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 blade fragments. 
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 
Transportation Safety Board of Canada Media Relations 819-994-8053 
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CO: Transportation Safety Board of Canada
ST: Newfoundland and Labrador
NI: TRN AIR  
-0- Nov/28/2013 14:08 GMT