Accident Overview
On an unspecified date, a Bell 206B helicopter operated by Héli-Star Inc., registration C-GNPI, serial number 2353, departed from Boucher Lake at approximately 2015 Eastern Daylight Time, destined for La Tuque Airport, Quebec. The pilot, the sole occupant, had accumulated about 4000 hours on the Bell 206. Shortly after takeoff, the aircraft crashed into Boucher Lake. The pilot sustained minor injuries, and the aircraft was substantially damaged.
Investigation Findings
Examination confirmed that the helicopter was equipped and maintained in accordance with existing regulations, and the pilot was certified and qualified for the flight. The engine was producing power at the time of impact, and no evidence of a power loss was found. Consequently, the investigation did not determine the cause of a transient decrease in engine rpm reported by the pilot.
The aircraft struck the water with significant force approximately one kilometer from where the rpm decrease occurred, suggesting that a precautionary landing or autorotation landing had not been planned. Such a landing would have reduced horizontal impact forces.
Seat Belt Degradation
A detailed examination of the seat belt shoulder straps revealed significant degradation due to ultraviolet (UV) exposure. The lower portions of the straps, which were more exposed to sunlight, had whitened and failed at 600 pounds of tension. The upper portions, less exposed because they were rolled on the inertia reel, failed at 1500 pounds. The upper portion failed at 66% of the limit required by standard TSO C22, indicating that even non-discolored straps may have UV degradation. The lower straps had their mechanical strength reduced to about 26% of original strength, failing before reaching the prescribed limit. This meant the pilot experienced greater deceleration forces than intended.
No signs of physical wear were found, and the belts were considered in good condition during maintenance and regulatory inspections. The absence of specific evaluation criteria for UV degradation contributed to the return to service of seat belts that no longer met regulatory requirements.
Determined Causes and Contributing Factors
The investigation did not determine the cause of the transient decrease in engine rpm reported by the pilot. The attitude, speed, and altitude of the aircraft did not allow the pilot to avoid a collision with the lake surface when the pilot raised the nose of the helicopter.
Other Findings
The pilot's seat belt shoulder straps failed at a tension level below regulatory requirements due to degradation from prolonged exposure to sunlight.