What happened
On the afternoon of the occurrence, a Bell 206B helicopter, operating on behalf of the Alberta Department of Environmental Protection, Lands and Forests division, departed Grande Prairie, Alberta, for aerial timber management inspections. After departing at 1338 MDT, the aircraft ceased all radio communication. Following unsuccessful attempts to re-establish contact, a search was initiated, and the helicopter was located by a search crew at 1700.
The aircraft had crashed approximately 52 miles northwest of Grande and was found in a state of destruction due to the impact and a subsequent intense fire. The wreckage indicated the helicopter had entered a steep, nose-down, right-bank descent into the trees. The pilot and two forestry officers sustained 3 fatal injuries.
The investigation
Investigators examined the wreckage and mechanical components of the Bell 206B. While the post-impact fire destroyed much of the airframe, the engine and flight control systems were analyzed by the TSB Engineering Branch. The examination of the engine power turbine output coupling showed a shear consistent with torsional overload, but no mechanical deficiencies were identified that would have contributed to the accident. The hydraulic servos showed no evidence of pre-impact malfunction, and the engine was found to be producing substantial power at the time of impact.
Regarding the pilot, records confirmed he was properly certified and qualified for the mission. A review of his medical history noted a recent incident on 25 September 1997, where he had inhaled jet fuel while siphoning fuel to accommodate an extra passenger, resulting in chemical pneumonia. While postmortem lung examinations showed no residual effects from this exposure, the pilot's medical history also revealed advanced atherosclerotic coronary artery disease, which could potentially cause sudden loss of consciousness.
Findings
- The aircraft was in compliance with all regulatory requirements for certification and equipment.
- The engine was functioning and producing power at the moment of impact.
- There was no evidence of mechanical failure or pre-impact system malfunction.
- The cause of the loss of control that led to the fatal descent could not be determined.
- The possibility of the pilot experiencing disorientation or loss of consciousness due to underlying coronary artery disease could not be ruled out.