What happened
On 17 December 2020, a Robinson R44 Clipper I, registration G-CLIO, was conducting a private flight to a farm in Holmfirth, North Yorkshire. The pilot, accompanied by two passengers, intended to land in a field after performing an out-of-ground-effect hover to inspect the landing area. During the approach, the pilot misjudged the wind direction, resulting in a downwind approach toward the landing site.
As the aircraft approached the field, the pilot attempted to slow the descent and transition into a hover by raising the collective lever. However, the engine was already at its power limit. This action caused the main rotor to overpitch, leading to a rapid reduction in rotor RPM and a sharp increase in the rate of descent. As the rotor speed dropped, the tail rotor lost effectiveness, and the aircraft experienced an uncontrolled yaw to the right. The helicopter struck the ground with 3 persons on board receiving minor injuries.
The investigation
The AAIB examined the wreckage and reviewed video footage of the approach. The investigation established that the aircraft was flying a downwind profile, which the pilot had failed to correctly identify despite visual cues from a nearby wind turbine. The examination of the Robinson R44 Clipper I revealed significant damage, including a fractured tail rotor shaft, damaged skids, and a punctured tail boom. The investigation also analyzed the engine performance, noting that the increase in torque during the overpitching event contributed to the loss of directional control.
Findings
- The pilot's incorrect assessment of the wind direction led to a hazardous downwind approach.
- The main rotor was overpitched because the pilot raised the collective without sufficient engine power to compensate for the increased drag.
- The reduction in rotor RPM caused a loss of tail rotor authority, making the resulting rightward yaw unrecoverable.
- The aircraft's descent rate increased rapidly as the engine reached its power limit.