What happened
On 16 April 2000, a Montgomerie-Bensen B8MR gyroplane, registration G-BXDC, was being used for private practice maneuvers at Carlisle Airport. The pilot, who had recently completed training, intended to perform wheel balancing and short runway hops. Witnesses observed the aircraft performing several successful low-altitude runs along the runway for approximately one hour.
During the final sequence, the aircraft was seen at a height of roughly 15 to 20 feet. The engine power was reduced, initiating a shallow descent. However, the pilot then increased the throttle to full power, causing the aircraft to climb to approximately 30 to 40 feet. Suddenly, the nose of the aircraft dropped, and the gyroplane entered a steep, 45-degree descent while rolling to the left. The aircraft struck a pasture field beyond the airport boundary, resulting in one fatality.
The investigation
Investigators examined the wreckage of G-BXDC and found the aircraft's construction to be generally good. While there was evidence of damage to the rotor blades, examination of the propeller and rotor discs revealed that the propeller blades had struck the rotor blades during the descent. This collision was caused by a distortion that bent the top of the mast rearwards, bringing the propeller and rotor paths into contact.
Technical analysis focused on the aerodynamic stability of the aircraft. In this specific model, the engine thrust line is positioned higher than the centre of gravity and the fuselage drag centre. While stable during normal flight, this configuration is susceptible to a phenomenon known as a 'power pushover' if rotor thrust is significantly reduced or lost.
Findings
- The pilot was performing practice maneuvers involving runway hops and wheel balancing.
- Towards the end of the final run, the pilot likely attempted to climb to avoid running out of runway, potentially intending to land in the adjacent field.
- This maneuver involved an abrupt pitch-down, which unloaded the rotor.
- The application of high engine power during this nose-down pitch likely induced a power pushover, causing the aircraft to pitch sharply downwards and lose control.