Introduction
On the morning of the occurrence, a Bell 206B helicopter (serial number 681) was conducting a positioning flight from Key Pile Camp, British Columbia, to the airstrip at Helmut, a distance of 10 kilometres. The pilot held a valid Canadian commercial helicopter licence endorsed for the Bell 206 and had about 1000 total flying hours, with 63 hours on type. The helicopter had no known deficiencies before the flight and was within load and centre of gravity limits.
Accident Sequence
The pilot descended on approach over surrounding trees while heading east toward the west side of the threshold of runway 31. The pilot had been in radio communication with a helicopter operating in the immediate area and did not indicate any emergency. The helicopter descended rapidly in a nose-low, right-banked turn. The approach path was cluttered with temporary buildings, vehicles, and water-filled dugouts. The lower vertical fin of the helicopter struck a steel pipe fence located on the west side of the threshold. The fuselage contacted the threshold surface in a nose-down, right-side-low attitude, breaking off the skid gear and cross tubes. The helicopter swung clockwise, came to rest on a magnetic heading of 213 degrees, and was consumed by fire. The pilot did not escape the wreckage and succumbed to the fire.
Weather and Site Conditions
The occurrence happened at about 0755 Pacific daylight time in daylight conditions. Weather was reported as clear sky, light and variable winds, and temperature 10°C. The Helmut strip is 2025 feet above sea level. The compacted earth runway threshold is raised about two feet above surrounding terrain; the steel pipe fence was installed in lower terrain, with its top about 17 inches higher than the threshold surface.
Aircraft and Pilot Information
The helicopter was a Bell 206B equipped with high skid gear. Logbooks and maintenance records indicated it was certified, equipped, and maintained in accordance with regulations. The last inspection was a 100-hour check on 29 May 2000; the last maintenance was replacement of a time-expired engine bleed valve on 31 May 2000. The helicopter had about 9903 hours since manufacture. The pilot recently arrived from Australia, held an Australian commercial helicopter licence, and had experience on several helicopter types. He successfully completed company training and a Transport Canada proficiency check. He was not wearing a helmet. Autopsy and toxicology showed no indication of physiological factors degrading performance; internal deceleration injuries were consistent with being thrown forward at impact.
Engine and Fuel Control Unit Examination
The fuel-fed fire destroyed most of the helicopter except the aft tail boom. The engine (Rolls-Royce/Allison 250-C20) and transmission were fire-damaged but relatively intact; strip examination indicated they were capable of normal mechanical operation. Examination of the fuel control unit (Honeywell/Bendix DP-N2) found that one screw head securing a ratio lever cover had separated and was retained by lock wire braid. The separated screw head failed due to hydrogen embrittlement cracking, likely from cadmium plating. The screw did not meet strength specifications; its ultimate tensile strength exceeded the maximum specified. Four additional screws from the same unit also did not conform. The failed screw was an unapproved part installed during an overhaul at the manufacturer's west coast facility in 1996. Bench testing showed that with the screw head missing, the cover leaked when fuel flow reached about 177 pounds per hour (pph), decreasing flow to about 111 pph, allowing engine output of about 101 shaft horsepower (normal at 177 pph is 250 shp).
Post-Impact Evidence
Low-energy signatures at the impact site—short fuselage travel, minimal main-rotor blade damage, lack of mast bending—indicated low main-rotor rpm. The sound of a turbine engine accelerating was heard just before impact. No smoke or flames were reported before impact. It is probable that the pilot smelled fuel from the leak and attempted an autorotational landing. The cluttered area would have prompted a stretched glide, leading to loss of rotor rpm and the subsequent fence strike.
Findings and Safety Actions
The TSB determined that the screw failure caused fuel leakage and power loss below flight requirements. The pilot attempted to autorotate but rotor rpm decayed, resulting in the fence strike. The screw was non-conforming and failed due to hydrogen embrittlement. As safety actions, Transport Canada notified the FAA of suspected unapproved parts. Honeywell issued service bulletins and revised drawings to prevent similar failures, and initiated corrective actions including scrapping non-conforming screws and updating supplier requirements.