What happened
On 9 April 2000, a Hughes 369HS, registration G-BPLZ, was performing a private flight at Wolverhampton Business Airport. While the pilot was hover taxiing the aircraft toward the airfield's refueling facility, the helicopter touched down on a heading of approximately 170°. Upon landing, the aircraft began rotating toward the left. The rotation continued for one full revolution before the helicopter briefly became airborne, at which point the rate of turn accelerated. The aircraft completed an additional half-turn, spinning rapidly before coming to a stop upright near the fuel bowser. Following the engine shutdown, the pilot identified that the tail boom had been severed.
The investigation
Investigators examined the aircraft and found no evidence of mechanical failure within the tail rotor gearbox mounting or the tail rotor drive system. While the main rotor blades remained undamaged, the tail rotor flapping stops were found to be destroyed. Meteorological data indicated that at the time of the incident, a surface wind of 16 knots was blowing from 060°, with gusts up to 25 knots expected, resulting in a crosswind from the left.
Analysis of a video recording of the event revealed that the helicopter had actually rotated to the left, contradicting the pilot's initial belief that the aircraft had drifted to the right. The pilot's attempt to correct a perceived rightward rotation by applying left pedal likely contributed to the sequence of events.
Findings
- The aircraft was subject to a left-sided crosswind during the landing attempt.
- The pilot applied left pedal input in response to a perceived rightward rotation, which was actually a leftward rotation.
- The combination of low rotor RPM and high yaw pedal demand likely caused the tail rotor to flap excessively during the rapid spinning.
- This excessive flapping caused the tail rotor blades to strike the tail boom, resulting in the destruction of the flapping stops and the severing of the boom.