Viscount 720C aircraft VH-RMQ, near Port Hedland, WA, 31 December 1968

At 0830 hours Western Standard Time on 31st December, 1968, a Viscount 720C aircraft, registered VH-RMQ, was scheduled to commence a regular public transport service, designated Flight 1750, from Perth to Port Hedland in the State of Western Australia.

The aircraft struck the ground in open spinifex-grassed country. The aircraft was destroyed by severe impact forces and the major portion was also affected by an intense post-impact fire.

There were 22 passengers and 4 crew on board, none of the aircraft occupants survived the impact.

The investigation found that the starboard inner wing had failed in upward bending at Station 143, where the strength of the lower boom of the main spar had been substantially reduced by fatigue cracking extending over some 85% of its cross-sectional area. It is probable that, at the time of the failure, flight loads close to 1g steady flight loads were being applied to the wing.

The cause of this accident was that the fatigue endurance of the starboard inner main spar lower boom was substantially reduced by the insertion of a flared bush at Station 143 when the margin of safety associated with the retirement life specified for such booms did not ensure that this boom would achieve its retirement life in the presence of such a defect.