The aircraft had been operating for two hours without any apparent problems. Shortly after lift off, following a refuelling stop, the pilot was unable to maintain directional control and the aircraft began yawing rapidly to the right. The pilot attempted to land the aircraft in a clear area, however, one skid dug in and the aircraft rolled over. A fractured tail rotor drive shaft intermediate flexplate was the only mechanical defect found during the investigation. The specialist engineering investigation established that the flexplate failure was caused by the main rotor blades contacting an external object. The only main rotor strike evident at the accident site occurred when the aircraft rolled over following the landing. Damage to the tail rotor control rods indicated that full left peddle had been applied at the time of the flexplate failure. Aircraft weight, power requirements, wind conditions and take-off and DEPARTURE techniques were not conducive to loss of tail rotor effectiveness, however, loss of tail rotor effectiveness will cause the aircraft to yaw to the right. The reason for the initial yaw was not determined. The aircraft rolled over when the pilot was forced to make an emergency landing on unsuitable terrain whilst he was attempting to recover from a difficult control situation.
