Accident Overview
A test flight ended in tragedy when the aircraft, a recently converted MK.2 to 21 version, crashed in a field near Cowbridge, south of Wales. The flight departed from Bristol-Filton Airport approximately 34 minutes before the accident. The airplane went out of control and dove into the ground, resulting in the deaths of all four occupants: three engineers from Bristol and one pilot.
Investigation Findings
The official investigation determined that the accident was caused by a structural failure of the fuselage stern frame, to which the fin was attached. This failure was attributed to the application of a load greater than the design ultimate load on the fin and rudder. Calculations indicated that the overloading resulted from excessive rudder movement at a speed exceeding 120 knots.
Aircraft Details
The source notes that the aircraft was an MK.2 version that had recently been converted to a 21 version. This flight was the second test flight for the certification program. No other details about the aircraft type, registration, or manufacturer were provided in the source.