History of the Flight
On 27 July 2019 at 1330 UTC, an Enstrom 280FX Shark (registration G-WPKR) was conducting a private flight to a landing site near Tongwynlais, Caerphilly. The pilot, aged 54 with 440 hours total flying experience (45 on type), contacted Cardiff Radar and received a wind report of 260/10 kt. He approached from the east for a steep descent onto the helipad. During the descent, the high rotor rpm warning alarm activated. In an attempt to reduce rotor rpm, the pilot over-corrected, triggering the low rotor speed warning alarm. He pushed the cyclic forward to increase rotor speed, but the helicopter overshot the helipad into a neighbouring quarry, descending to approximately 50 ft above the quarry floor.
The pilot hovered the helicopter to recover and then initiated a climb at full power. During the climb, it became apparent that insufficient power was available to sustain the climb. The climb rate reduced, and the low rotor rpm warning sounded. The pilot reported that he could not turn or descend without colliding with the rock face due to proximity to the quarry wall.
He continued applying full power, hoping to clear the quarry lip and boundary fence to land on the helipad. As the helicopter came over the lip, it started to descend and landed on a fence and bags of ballast. The helicopter came to rest approximately 0.5 m from the quarry edge. With full power still applied, the engine was over-speeding; the pilot turned the throttle to idle, disengaged the clutch, and turned the fuel off. He was uninjured and exited the helicopter without assistance.
Technical Discussion
Over-pitching occurs when maximum engine power is achieved and collective pitch continues to increase, causing a reduction in rotor rpm. As rotor rpm decays, the coning angle of the rotor blades increases, reducing rotor disc size and total thrust while increasing drag. Large coning angles prevent engine power from increasing rotor rpm. If rotor rpm continues to drop, it may reach a point where it cannot be restored even with full engine power – a condition known as over-pitching. The recovery actions involve lowering the collective lever and increasing throttle to reduce blade drag and allow rotors to regain speed, though height is lost during recovery.
In this event, having reached the bottom of the quarry, the pilot applied full power to climb out. With the throttle fully open, no additional power could be demanded once low rotor rpm occurred. Due to the position relative to the quarry wall, the pilot reported no option to turn or descend. Unable to execute recovery actions, the helicopter narrowly cleared the quarry lip before descending onto the fence and ballast bags.
Conclusion
While attempting to recover from overshooting the landing site, the helicopter encountered a low rotor rpm situation from which the pilot did not consider it possible to effect the necessary recovery actions. The pilot subsequently commented that he had misjudged the approach, considering it challenging in normal circumstances, particularly as he had not flown G-WPKR for some time due to maintenance. With hindsight, he believed he should have waited to fly with a safety pilot and that approaching from the north-west might have been less challenging given the light wind.