AAIB investigation to Prion Mk 3, (UAS registration n/a) 030221
Loss of power followed by stall and spin, Salisbury Plain, Wiltshire, 3 February 2021.
Summary:
During a training flight at a height of 400 ft agl the engine lost some power and the aircraft started to descend. The operator sent a command to limit the throttle but this did not resolve the issue. The autopilot was in a mode whereby the throttle was used to control airspeed and elevator used to control altitude. The loss of altitude caused the autopilot to pitch the unmanned aircraft nose-up until it stalled, entered a spin, and then hit the ground.
Following this accident the engine has been modified and the operator has changed their training and operational procedures to help mitigate the risk of recurrence.
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Published 9 December 2021