Air Accidents Investigation Branch
Summary:
The flight departed from Dunkeswell Aerodrome with the purpose of revalidating the aircraft owners PPL. The instructor was demonstrating the procedure for an engine failure at 2,200ft and a target airspeed of 80 kt. He reported that as he applied nose-up pitch, there was a loud bang and the aircraft immediately pitched down with severe buffeting.
After recovering control, the instructor elected to make a forced landing and, considering it to be the only safe option, he chose to land in a nearby field. On landing he was unable to stop the aircraft before entering a river at around 30 kt, with the aircraft finally coming to rest after striking the opposite bank. Neither of the occupants were injured. The instructor subsequently found that the baggage compartment door was open, and the canvas aircraft cover was missing. He attributed the accident to the compartment door opening in flight releasing the aircrafts cover, which temporarily affected the airflow over the elevator, resulting in the uncommanded pitch change.