Homebuilt Gyroplane, Bridgewater, Victoria, on 3 November 1990

Circumstances:

The pilot took off to the west and climbed straight ahead for approximately one kilometre. At about 150 feet above the ground the complete main rotor assembly suddenly separated from the gyroplane. The gyroplane then plummeted to the ground. The main rotor assembly struck the ground about 15 metres short of the main impact site. Wreckage examination disclosed that the lower teeter stop plate was bent on both ends, probably prior to the accident. The bent teeter stops allowed the main rotor blades to flap down beyond normal limits. All teeter stops had pronounced marks indicating repetitive contact. While the main rotor was spinning, one of the blade grips and one of its blade attachment bolts contacted the prerotator horn causing overload failure of the torque tube at the hole for the main rotor assembly attachment bolt. An imprint on one side of the torque tube indicated that full aft control stick had been applied at the time the torque tube began to fail. None of the witnesses saw the gyroplane proposing or performing unusual manoeuvres before rotor separation.

Significant Factors:

The following factors were considered relevant to the development of the accident:

1. The spinning main rotor contacted the prerotator horn because bent teeter stops allowed flapping of the main rotor blades beyond safe limits.

2. The torque tube suffered overload failure.