What happened
On 29 June 2016, a Guimbal Cabri G2, registration G-CILU, was conducting a dual training flight at Cotswold (Kemble) Airport. The flight was performing a 'quick-stop' manoeuvre, which involves flying downwind at 60 knots and 30 feet above ground level before executing a left turn and flare to reach a hover.
During the middle of the turning phase, the aircraft experienced a sudden descent. As the helicopter lost altitude, the low rotor RPM warning horn activated. The instructor attempted to take control of the aircraft to level it; however, the main rotor blades made contact with the ground. The helicopter skidded across the grass and came to a halt. There were no injuries to the two crew members on board.
The investigation
The investigation examined the flight profile and the sequence of events leading to the loss of altitude. It was established that the weather conditions were clear, though a wind of 15 to 25 knots was present. The investigation looked into the actions of the crew during the emergency and the mechanical state of the aircraft's rotor system. The instructor noted that the student pilot had applied excessive pitch to the main rotor blades in an attempt to compensate for a loss of height caused by turbulence.
Findings
- The primary cause of the accident was the over-pitching of the main rotor blades in response to turbulence-induced altitude loss.
- The instructor's attempt to regain control was hindered by the student pilot's delayed release of the flight controls.
- The aircraft sustained damage to the fuselage, tail, landing skids, and main rotor blades.