the absence of an interference fit left the inner lower boom vulnerable to developing fatigue cracks at Station 143. Despite exhaustive investigation it was not possible to determine when, why, or by whom, the bush at Station 143 had been flared with a conical tool, removed and then re-inserted in the bolt hole. Investigators could not imagine circumstances in which a responsible tradesman would take these actions. Approximately 5000 flights after new inner lower booms were installed in 1964, numerous fatigue cracks began to develop in both the forward and rear edges of the hole. These cracks eventually joined to form a single crack growing forwards from the forward edge of the hole, and a single crack growing rearwards from the rear edge of the hole. These two cracks grew to affect 85% of the cross-sectional area of the inner lower boom at Station 143. Seven weeks after the accident the Minister for Civil Aviation, Reg Swartz, announced that the accident had been caused by metal fatigue and he did not consider it necessary to appoint a court to inquire into the accident. This position was challenged by the opposition spokesman for aviation, Charlie Jones. British Aircraft Corporation carried out multiple tests in which a bush was slightly flared with a conical tool and pressed into a hole in a test piece of the same aluminium alloy as the inner lower boom. Each test piece was then subjected to alternating stresses. These tests showed that eliminating the interference fit by insertion of a flared bush identical to the one found in the wreckage of VH-RMQ substantially reduced the mean life to failure of the boom – possibly by as much as 50%. The investigation by the Australian Department of Civil Aviation was completed in September 1969 and concluded: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.Accident Investigation Report, Section 3.28 When the Minister tabled the report in the Parliament in September 1969, Jones again called for a public inquiry. Aircraft The aircraft was a Vickers Viscount 720C manufactured in 1954 and assigned serial number 45. It