What happened
During a positioning flight from Key Pile Camp to the Helmut airstrip in British Columbia, a Bell 206B helicopter experienced a sudden loss of engine power. As the pilot approached the runway, the aircraft entered a rapid, nose-low, right-banked descent. The landing area was obstructed by various temporary structures, vehicles, and dugouts. During the descent, the helicopter's lower vertical fin struck a steel pipe fence located near the runway threshold. The impact caused the fuselage to strike the ground, breaking the skid gear and cross tubes. The aircraft subsequently swung around and was consumed by a fuel-fed fire. The pilot, who was not wearing a helmet, sustained fatal internal deceleration injuries and did not survive the fire.
The investigation
Investigators examined the engine and transmission, finding them mechanically capable of normal operation. However, a strip examination of the engine's fuel control unit revealed that a screw head securing a ratio lever cover had separated. The TSB Engineering Laboratory determined the failure was caused by hydrogen embrittlement cracking, likely originating from the cadmium plating process. Further investigation revealed that the failed screw, along with several others in the unit, were unapproved parts that did not meet manufacturer strength or heat treatment specifications.
Analysis of the wreckage also showed low-energy signatures, such as minimal damage to the main rotor blades and mast, indicating low main-rotor RPM at the time of impact. This suggested the pilot was likely attempting an autorotational landing to avoid obstacles. The investigation also noted that the pilot was not wearing a helmet, which may have impacted survival during the deceleration forces of the impact.