What happened
During a reindeer herding mission, a pilot was attempting to land and pick up a passenger from a landing site consisting of wet mire and tufts of vegetation. To facilitate landings on soft or snowy terrain, the helicopter was equipped with specialized landing gear extensions known as "bear paws."
After the aircraft was set down, the pilot noticed the helicopter felt unstable because a tuft of turf was positioned under the left landing gear. To correct this, the pilot attempted to lift the aircraft slightly to reposition it to the right. During this maneuver, the aircraft experienced a sudden roll to the right. Despite the pilot immediately lowering the collective pitch, the roll continued until the main rotor struck the ground, leaving the aircraft resting on its right side. The pilot escaped the uninjured aircraft without fire, and no emergency services were summoned to the scene.
The investigation
Investigators examined the landing gear and the specialized plates used for soft-ground operations. They discovered that the bear paw mounted on the right rear section of the landing gear had rotated slightly clockwise. Marks found on a nearby tuft of turf indicated that the edge of this plate had become snagged during the movement.
Further inspection of the installation revealed a mechanical vulnerability: the plate was mounted in a way that allowed it to rotate approximately 20 degrees clockwise and 80 degrees counterclockwise from its intended position. The pilot reported no prior technical malfunctions or issues with the aircraft's performance leading up to the incident.
Findings
- The plate on the right rear landing gear became stuck in the turf during the pilot's attempt to hover and reposition the aircraft.
- The pilot was unable to counteract the resulting roll tendency.
- The mounting of the bear paw allowed for unintended rotation, which contributed to the snagging incident.