What happened
During a firefighting mission near a creek valley northwest of Lillooet, British Columbia, a Bell 214B-1 helicopter, registration C-GTWV, experienced a sudden loss of engine power. The aircraft, operated by Transwest Helicopters Ltd., was attempting to deliver a water load when the engine failed at an altitude of approximately 200 feet.
In response to the power loss, the pilot-in-command attempted to climb back over a nearby ridgeline to reach a clearing. During the maneuver, the crew released the 130-foot long-line and water bucket to reduce weight. As the helicopter approached the ground, the pilot applied full collective to cushion the impact. However, due to the uneven and sloping terrain, the advancing main-rotor blade struck the ground, causing the aircraft to pitch forward and roll onto its left side. The impact caused the tailboom to separate from the fuselage.
The pilot-in-command sustained a concussion and was rendered unconscious by the impact, while the copilot escaped with minor injuries. The copilot successfully extracted the unconscious pilot from the wreckage. A small fire ignited in an exhaust duct following the crash, though it was quickly extinguished.
The investigation
Investigators examined the engine's fuel control unit (FCU) and found it contaminated with metallic debris. Specifically, a broken leg from a cotter pin was discovered within the unit, which likely obstructed fuel flow and caused the engine to lose power. The investigation revealed that the cotter pin had suffered a fatigue fracture due to movement within the linkage assembly.
Further scrutiny of the maintenance history showed that the FCU had been incorrectly identified as a specific upgraded configuration, which allowed it to remain in service for an extended period without the necessary modifications. Additionally, the investigation found that the overhaul process lacked detailed records and did not involve a complete disassembly of all subcomponents, which prevented the detection of the internal wear and debris.
Findings
- Metallic debris within the fuel control unit likely disrupted fuel flow, leading to the engine power loss.
- The sloping and uneven terrain at the landing site caused the helicopter to roll over after the initial touchdown.
- Inadequate overhaul documentation and incomplete disassembly of the FCU prevented the identification of failing subcomponents.
- The lack of shoulder restraints for the crew increased the risk of injury during the rollover event.