The pilot was undergoing his initial helicopter licence training and was authorised to fly three solo circuits at Mangalore. A helicopter flying instructor briefed him for the flight. The engine start was conducted by the pilot but monitored by the instructor, who vacated the helicopter shortly after.
As the helicopter started to lift off the ground into a hover, it rolled to the right until the main rotor struck the ground. The main rotor and transmission then separated from the fuselage, which landed on its right side, facing in the same direction as it was parked. Several rescuers reached the accident site within seconds and shut down the engine. They released the pilot's lap seat belt and moved him from the wreckage. A short time later, the pilot died of his injuries.
The autopsy report attributed the cause of death to head injuries. The pilot's injuries and damage to the aircraft were consistent with his head having impacted the upper door surround structure. The pilot did not have his upper body restraint harness secured. The aircraft checklist contained a requirement that the pilot's seat harness be secured before the engine was started. The flying school's procedures required that the pilot's complete harness, including the shoulder restraint, be secured before the engine was started.
Initial examination of the wreckage disclosed that the left side of the front of the cockpit had been severed. The right side and rear of the cockpit were intact and relatively undamaged. The skids were undamaged. Both main rotor blades had broken into several pieces and were lying on the tarmac near the fuselage. Abrasion marks on the rotor blades and impact marks on the ground indicated that the helicopter had rolled to the right until the main rotor had contacted the tarmac. There were no marks on the tarmac to indicate that the skids had been dragged sideways, had sunk into the tarmac surface, or had stuck to the surface.
Examination of the wreckage did not reveal any pre-existing defects or malfunctions that would have precluded other than normal operation. An examination of the maintenance records indicated that all required maintenance had been performed, and there were no defects listed on the maintenance release.
The pilot was an experienced commercial pilot with a total flying time of more than 4,000 hours on fixed-wing, multi-engine aircraft. He was correctly licensed and authorised for the flight.
The pilot commenced training for his private pilot licence (helicopter) on 9 May 1997 and continued training at irregular intervals over the next 11 months. During this period he continued to fly fixed-wing aircraft as part of his employment. At the time of the accident, he had completed 13.6 hours on the Bell 206 type, including 0.6 hours of solo flying. All his helicopter training had been on this aircraft type. The pilot had not flown a helicopter for 21 days before the accident flight.
Two witnesses saw the helicopter attempt to lift off the ground. One reported seeing both skids lift off the ground before the helicopter began to roll to the right. A second witness reported seeing only the left skid leave the ground before the helicopter began to roll.
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.
- The pilot had a low experience level and a low recency level on helicopter aircraft.
- For reasons undetermined, the helicopter began to roll to the right before both skids had left the ground.
- The pilot did not take timely action to correct the dynamic rollover situation.
- The pilot's shoulder harness was not secured at the time of the accident.
|Date:||13 February 1998||Investigation status:||Completed|
|Time:||1255 hours ESuT|
|Release date:||18 July 2000|
|Report status:||Final||Occurrence category:||Accident|
|Highest injury level:||Fatal|
|Aircraft manufacturer||Bell Helicopter Co|
|Type of operation||Flying Training|
|Damage to aircraft||Destroyed|
|Departure point||Mangalore, VIC|
|Departure time||1255 hours ESuT|
|Role||Class of licence||Hours on type||Hours total|