Accident Sequence
The aircraft, carrying a pilot and five passengers, was on an IFR flight from Stansted Airport to Tatenhill Aerodrome. Shortly after takeoff from runway 23, the pilot reported a problem and requested to return. Stansted ATC cleared the aircraft for a left-hand circuit and return. As the aircraft turned left toward a downwind leg, the left bank suddenly increased, and the aircraft turned onto its back before descending vertically. It crashed into a wooded area southwest of the airport. Immediately after impact, a fierce fire erupted, and all six occupants were killed instantaneously.
Investigation
Examination of the wreckage confirmed that the right propeller and engine had been delivering power normally before impact, but the left propeller and engine had not been producing power. The left engine drive fuel pump had suffered fire damage, and its rubber seals were leaking. Disassembly revealed that the aneroid unit within the pump was corroded and could not have functioned. To investigate the possible effects of such corrosion on engine performance, tests were conducted using a similar engine in a test facility. These tests showed that the corroded aneroid caused the engine to misfire and run roughly at high power settings, but the engine ran normally at low power. While not fully representative of the accident flight conditions, the tests indicated no tendency for the engine to fail completely, although sudden full throttle applications greatly aggravated the rough running. Despite these findings, no reason for the apparent marked power loss associated with the left engine fitted to G-HAST has been established.