AAIB investigation to AS350 B3e Ecureuil, G-MATH
Loss of control during hydraulics-off training, Wycombe Air Park, Buckinghamshire, 5 May 2017.
Summary:
The accident occurred whilst the helicopter was engaged in hydraulic failure training. An instructor was in the left seat of the helicopter, a pilot under training in the right seat and another pilot under training, who was a passenger on this flight, was seated in the rear.
The right-seat pilot was performing a hydraulics-off approach, to finish in a run-on landing. The instructor became dissatisfied with the approach parameters and took control in the latter stages, performing a hydraulics-off go-around into a left-hand circuit, before lining up the helicopter on final approach for the pilot to make a second attempt. Once again, the instructor took control late in the approach and performed another go-around. On this occasion, the left turn onto the downwind was flown with a higher angle of bank (AOB). The instructor was unable to control the roll attitude and the helicopter rolled left, beyond 90掳 AOB, descended rapidly and struck the ground, coming to rest on its left side.
All three occupants were seriously injured. The right-seat pilot died some weeks later from injuries sustained in the accident.
No technical issues were identified and a definitive reason why the instructor was unable to roll the helicopter back to a level attitude could not be determined.
The investigation concluded that clearer instructions in the AS350 flight manual for hydraulics-off flight would help prevent similar accidents in future. In response to this accident, the helicopter manufacturer has taken safety actions including: amending the AS350 flight manual to limit the AOB to 30掳 during hydraulics-off flight and the inclusion of warnings not to conduct low speed manoeuvres with hydraulics off due to the danger of loss of control. It has also prepared a safety video describing how to perform hydraulics-off training.
Download report: