Disrupted fuel flow likely led to 2010 firefighting helicopter crash in Lillooet

A Transportation Safety Board of Canada (TSB) investigation report (A10P0242) released on May 13 identified disrupted fuel flow as the likely cause of the crash of a Transwest Helicopters Ltd. Bell 214B-1 helicopter, which was fighting fire approximately 20 nautical miles northwest of Lillooet, British Columbia. The helicopter lost power, touched down hard on uneven terrain, and rolled over onto its side. The 2 pilots escaped with minor injuries.
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During the July 29, 2010 flight, after the pilots successfully carried out 12 water drops with the helicopter, the engine lost power. The pilot-in-command (PIC), seated in the left-hand seat, turned the helicopter left and downhill and descended toward an open area to land. As the helicopter neared the ground, the PIC leveled the helicopter and reduced the rate of descent; however, the main-rotor struck the terrain on the right side, and the helicopter came to rest on its left side facing uphill. The tail broke off, and the tail rotor assembly landed 30 feet away. The helicopter was substantially damaged, and there was a small post-crash fire.
Investigators found that the engine fuel control unit (FCU) was contaminated with metallic debris, which likely disrupted fuel flow and caused the engine to lose power. A review of maintenance procedures was undertaken by the TSB, which revealed that overhaul procedures and documentation were unclear and lacked detail, and that recurring component failures were not tracked and monitored as required by the approved maintenance organization. The absence of tracking and monitoring FCU failures increases the risk that component problems will not be fixed before failure.
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The investigation further noted that inspections did not include complete disassembly of sub-component parts of the FCU, and some FCUs were misidentified when incomplete modifications were carried out.
Shortly after the occurrence, Honeywell, the FCU manufacturer, issued 2 service bulletins for the misidentified FCUs, reducing the time between overhauls from 2400 hours to 1800 hours, and later recalled all these FCUs.

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