A report released by the Defence Service Authority states that an unexplained engine problem caused a plane to crash into a field, in July last year, killing one person and injuring another.
On July 8, the crew of a UK registered Yak-52 aircraft reported that they had suffered an engine malfunction and attempted a forced landing.
The aircraft was operating in support of the Empire Test Pilot School and had a crew of 2: the Front Seat Pilot was a Royal Air Force Test Pilot while the Civilian Pilot in Command occupied the rear cockpit.
In the final stages of the attempted forced landing, near to the village of Dinton in Wiltshire, the aircraft crashed.
The RAF Test Pilot was pronounced dead at the scene and the Pilot in Command suffered serious injuries.
Both the civilian Air Accidents Investigation Branch from the Department of Transport and the Defence Accident Investigation Branch were deployed to the crash site.
The report does say that omission of external checks before the flight could mean that signs of an impending malfunction were missed.
The report also suggests that the safety equipment on board could have been more suitable and wearing a more suitable helmet could have mitigated injuries.