AAIB investigation to AS350 B3e Ecureuil, G-MATH

Loss of control during hydraulics-off training, Wycombe Air Park, Buckinghamshire, 5 May 2017.


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° 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° 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:

AS350 B3e Ecureuil, G-MATH 10-18

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Glossary of abbreviations

Published 11 October 2018