What happened
On December 31, a Hughes 369D (registration C-GXQI) was engaged in seismic operations, moving bags from one line to another using a 10-foot line and a carousel. The mission involved transporting bags in lifts of five, a process that had been ongoing since the early morning. At approximately 12:45, ground personnel noticed the aircraft had failed to return for its scheduled lift. After radio communication attempts failed, nearby helicopters were dispatched to search for the aircraft.
The helicopter was located around 13:30 in a ravine characterized by 100-foot-high spruce trees. The wreckage showed significant damage, and the pilot sustained serious injuries. The aircraft came to rest on its side in a 30-foot-deep ravine, with the engine still running at the time of impact, as evidenced by a burn mark behind the exhaust.
The investigation
Investigators examined the wreckage and the surrounding terrain, noting that the ground marker for the seismic bags was located at the bottom of the ravine. To reach this specific spot, the pilot would have needed to perform a vertical descent alongside large trees. The investigation found that the main-rotor blades had struck trees during the descent, causing the tail boom to separate and all five blades to detach from the hub before the aircraft hit the ground.
Evidence suggested the sling line had been manually released prior to the crash and was found wrapped around the rotor hub. While the pilot had recently completed training on the Hughes 500 type, they had very limited flight hours on this specific model. Although there were anecdotal reports of pressure on pilots to maintain high productivity during seismic operations, no direct evidence of such pressure was found in this specific instance.
Findings
- The helicopter experienced a vertical descent into the trees while the engine was producing power.
- Main-rotor blades struck trees during the descent, leading to a total loss of control.
- The pilot's experience with the Hughes 500 and seismic-specific operations was limited.
- It is possible the aircraft entered a vortex ring state during the vertical descent, a condition that is difficult to detect and difficult to recover from in confined, wooded areas.
Safety action
Following the accident, the operator, Airborne Energy Solutions Ltd., introduced several safety improvements, including:
- Enhanced training resources and increased safety awareness.
- Reiteration of pilot relief systems and protocols for managing client-related pressures.
- An educational plan for seismic clients and crews regarding the placement of ground markers.