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Analysis

Summary

The two eyewitnesses gave conflicting views on whether both skids were off the ground. The witness who reported that the right skid did not leave the ground during the attempted lift-off was a helicopter flying instructor. His evidence was given greater weight because he was an experienced observer of helicopter operations, having daily monitored solo student helicopter pilots over several months.

In the absence of any evidence of flight control malfunction, strong winds, or intentional pilot input, the circumstances of the accident were consistent with dynamic rollover.

Dynamic rollover can occur when a helicopter is in the hover with one skid touching the ground. If the helicopter is allowed to roll to one side, pivoting around the skid on the ground, the thrust from the tilted rotor will apply a sideways force to the top of the helicopter, causing it to continue rolling. Rapid pilot input is then necessary to prevent the main rotor striking the ground.

For dynamic rollover to occur, one wheel or skid must be touching the ground or a fixed object. At the accident site, there were no marks on the tarmac to suggest that either skid had been restricted in its movement when the helicopter attempted to lift off. However, eyewitness evidence suggested that the right skid remained in contact with the ground during the accident sequence.

Due to the pilot's low number of flying hours on helicopters and his lack of recent helicopter flying, he may not have recognised that a dynamic rollover situation was developing or may have been slow to apply appropriate corrective action.

The rescuers reported that although the pilot's shoulder harness was not secured, the lap belt was when they attempted to move his body from the aircraft. The pilot had either not secured his shoulder harness before starting the engine, contrary to the flying school's standard operating procedures and aircraft checklist or, for reasons unknown, had unsecured the shoulder harness prior to the lift-off sequence.

The right side of the cockpit occupied by the pilot was largely undamaged; therefore the accident was most probably survivable. The evidence suggested that the pilot's head injuries were caused when his head struck the cockpit structure near the cockpit roof. Although a secured shoulder harness would not have prevented the pilot's head from contacting the right door, it would have reduced the upper body movement and therefore may have reduced the severity of the pilot's injuries.

 
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