What happened
On 04 April 1994, an Aerospatelle AS350B helicopter, registration C-FHBG, was performing a medical transport mission near High Prairie. Operated by Turbowest Helicopters Limited, the aircraft was carrying a patient on a stretcher, a crew member, and an engineer. The mission involved transferring a patient from a rural seismic site to a ground vehicle for further transport to a hospital.
While the pilot was circling at approximately 150 feet above ground level to ensure the landing area was clear of traffic, the engine suddenly lost all power. The pilot initiated an autorotation into a nearby wooded clearing. During the descent, the aircraft struck the uneven terrain with a high rate of descent and significant groundspeed. The impact caused the skid gear to collapse, and the helicopter rolled onto its left side, resulting in substantial damage to the aircraft. Despite the severity of the impact, all three occupants escaped without injury.
The investigation
The investigation focused on the sudden loss of engine power and the circumstances leading to the engine failure. Investigators examined the cockpit configuration, specifically the floor-mounted control quadrant. It was noted that the patient's position in the cabin placed their knee in close proximity to the fuel flow control lever.
During the flight, the patient attempted to adjust a knapsack under their knee to alleviate pain. The engineer moved from his seat to assist the patient with the bag. The investigation established that during this movement, the fuel flow control lever was moved into the closed position, which cut off fuel to the engine.
Findings
- The primary cause of the engine failure was that the floor-mounted fuel flow control lever was inadvertently moved to the closed position, causing fuel starvation.
- The fuel flow control lever lacked a guard or protection to prevent accidental movement.
- The design of the control quadrant allowed the lever to be moved out of the flight position easily.
- The heavy impact and subsequent damage were caused by the combination of low altitude, low rotor RPM, high groundspeed at impact, and the uneven nature of the landing site.
- The pilot and aircraft were fully compliant with all regulatory requirements for training, maintenance, and airworthiness.