What happened
On a mission involving both fire patrol and a Trumpeter Swan cygnet survey, a Cessna 337, registration C-GGDW, crashed near Beaverlodge, Alberta. The aircraft, operated by Wildlife Observation Services Inc., was flying at a very low altitude to allow a biologist to accurately count young swans. During a steep turn at approximately 1437 mountain daylight time, the pilot lost control of the aircraft. The plane descended at a 45-degree angle through a stand of trees, striking them with a left-wing-low attitude before skidding into a beaver pond.
The impact resulted in one fatality and one serious injury. The pilot died from blunt cranial trauma, while the biologist survived with multiple fractures and lacerations. Although the aircraft's emergency locator transmitter failed to signal due to severed antenna cables, the crew was located using GPS tracking software.
The investigation
Investigators examined the aircraft's flight path, the wreckage, and the organizational oversight of the flight. Analysis of GPS data revealed that the final turns preceding the crash involved bank angles exceeding 50 degrees. At the time of the accident, the aircraft was flying at a high-density altitude with a ground speed of approximately 83 knots, which was below the calculated stall speed for those specific flight conditions.
The investigation also reviewed the company's operational control and the pilot's qualifications. It was noted that the pilot did not meet the specific flight hour requirements established by the Alberta Sustainable Resource Development (ASRD) contract. Furthermore, the company's operations manual lacked specific procedures or training requirements for the high-risk, low-altitude maneuvers required for wildlife surveys.
Findings
- The pilot experienced an aerodynamic stall caused by the combination of low airspeed, a high angle of bank, and high-density altitude.
- The low altitude of the flight prevented the pilot from recovering from the stall before hitting the trees.
- The pilot lacked sufficient guidance and specialized training for performing low-level aerial surveys.
- The operator permitted a pilot to conduct flights without meeting the established ASRD experience and hour requirements.
- The loss of the ELT signal, caused by severed antenna leads, delayed the search-and-rescue mission.
Safety action
Following the investigation, ASRD implemented new standard operating procedures for low-level operations, including a maximum bank angle of 30 degrees when flying below 500 feet AGL and maintaining higher airspeeds during turns. Wildlife Observation Services Inc. updated its operations manual to include more rigorous training, mandatory mission briefings, and enhanced flight-following capabilities using GPS and satellite communication.