What happened
On a flight from a staging site at Johnson Lake toward Fort McMurray, Alberta, an Aerospatiale AS350BA (registration C-FHLF) carrying the pilot and four heli-tack firefighters experienced a loss of control. While cruising at approximately 1500 feet, the pilot began a rapid descent to a low altitude to observe wildlife. To achieve this, the pilot pushed the cyclic forward to increase airspeed rather than lowering the collective.
As the aircraft reached an altitude just above the tree tops, the pilot attempted to level off by pulling back on the cyclic and raising the collective. During this maneuver, the flight controls became difficult to move. The helicopter rolled to the right and pitched up before diving into the marshy terrain and overturning. The accident resulted in one fatality and three serious injuries. One passenger was ejected from the cabin after an inboard seat-tbelt attachment failed.
The investigation
The investigation examined the aircraft's hydraulic systems, the pilot's training, and the operational procedures regarding weight and balance. Investigators found that the aircraft's hydraulic servos showed no mechanical anomalies. However, the investigation focused on the phenomenon of servo transparency, where aerodynamic forces on the rotor blades exceed the hydraulic servos' ability to control pitch.
It was established that the pilot was trained to recognize this phenomenon but failed to implement the correct recovery procedure—lowering the collective—during the event. Furthermore, the investigation found that the pilot had not completed an accurate weight and balance report for the flight, relying instead on estimates from previous missions. The passengers and cargo weights were not officially recorded or provided to the pilot prior to departure.
Findings
- The pilot initiated a sudden, high-speed descent and lost control due to servo transparency during the attempt to level off.
- The pilot did not execute the proper recovery technique (lowering the collective) and was unable to correct the aircraft's attitude due to the low altitude and proximity to trees.
- The pilot's previous flight maneuvers, involving sudden climbs and descents, had not been reported to management.
- The lack of a formal weight and balance report meant the pilot could not confirm the aircraft was within its allowable operating limits.