Accident
On a daytime IFR training flight from Mallala in clear weather, the port mainplane of the Bristol B170 separated from the fuselage. The aircraft crashed into a wheat field approximately 2 miles from the RAAF Station. Impact ignited the field, and RAAF Mallala fire crews extinguished the blaze to reach the crash site. The port wing was recovered about 1.5 miles from the main wreckage.
Occupants
The three crew members on board were Flight Lieutenant J. D. Entwhistle, Flying Officer Leonard Murphy, and Flying Officer Donald Shillinglaw. All three were killed.
Investigation and Probable Cause
The RAAF investigation traced the cause to events earlier that day. A separate training flight had placed the wing under severe load. That morning's exercise involved recovery from unusual attitudes using only a limited instrument panel. On two occasions, the training captain executed steep diving turns, the recovery from which generated high G-forces, causing a second pilot seated at the navigator position to black out. Subsequent investigations identified fatigue failure in the wing root ends and main spar structure as the origin of the structural failure. In response, Bristol produced a modification that proved successful. Most British and European civil B170s were flown to Western Airways at Weston-super-Mare for the modification at Bristol's expense. Australian B170s underwent the work at Bristol Aviation Services at Bankstown, where wings were removed and modifications installed.