What happened
On 27 July 2019, an Enstrom 280FX helicopter, registration G-WPKR, was performing a private flight near Tongwynlais, Caerphilly. While executing a steep descent toward a private helipad from the east, the pilot encountered a high rotor RPM warning. In an attempt to stabilize the rotor speed, the pilot over-corrected, triggering a low rotor RPM alarm. During this maneuver, the aircraft overshot the intended landing pad and descended into an adjacent quarry, hovering approximately 50 feet above the quarry floor.
Seeking to recover, the pilot applied full power to climb out of the quarry. However, the aircraft was unable to maintain the climb, and the low rotor RPM warning returned. Trapped near a rock face with no room to turn or descend, the pilot continued to apply maximum power in an attempt to clear the quarry lip. The helicopter eventually cleared the edge but struck a fence and several bags of ballast, resulting in no injuries to the pilot but causing extensive damage to the tail rotor, landing skids, and lower fuselage.
The investigation
Investigators examined the flight dynamics and the pilot's actions during the critical descent and climb phases. The investigation established that the pilot had not flown G-WPKR recently due to ongoing maintenance. The pilot noted that the approach was particularly difficult due to the terrain and the chosen flight path. The investigation also looked into the mechanics of the engine's performance during the climb, specifically focusing on the phenomenon of over-pitching.
Findings
- The pilot's attempt to correct the initial rotor speed fluctuation led to an over-correction that caused the aircraft to overshoot the landing site.
- The pilot was unable to perform necessary recovery actions, such as lowering the collective to reduce drag, because the aircraft's position relative to the quarry wall prevented any descent or turning.
- The engine was unable to provide sufficient power to sustain the climb due to the low rotor RPM situation.
- The pilot's recent experience on this specific type was limited, having only 45 hours on the model.