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On December 31, 1968 a [[Vickers Viscount]] aircraft departed from [[Perth, Western Australia]] for a flight of {{convert|724|mi}} to [[Port Hedland, Western Australia]] . On board were two pilots, three air hostesses and twenty-one passengers. The aircraft crashed twenty-eight miles short of its destination with the loss of all lives.<ref name=1.1>Section 1.1</ref> Half of the right-hand wing, from outboard of the inner engine to the wingtip, including the outer engine and its propeller, struck the ground about {{convert|3000|ft|m}} away from the main wreckage site.<ref>Section 1.12</ref> |
On December 31, 1968 a [[Vickers Viscount]] aircraft departed from [[Perth, Western Australia]] for a flight of {{convert|724|mi}} to [[Port Hedland, Western Australia]] . On board were two pilots, three air hostesses and twenty-one passengers. The aircraft crashed twenty-eight miles short of its destination with the loss of all lives.<ref name=1.1>Section 1.1</ref> Half of the right-hand wing, from outboard of the inner engine to the wingtip, including the outer engine and its propeller, struck the ground about {{convert|3000|ft|m}} away from the main wreckage site.<ref>Section 1.12</ref> |
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| image1 = *[http://www.aussieairliners.org/viscount/vh-tvb/0129.213.html Photograph of VH-RMQ one month before the crash]<ref>[http://www.aussieairliners.org/viscount/vh-tvb/0129.213.html Aussieairliners]</ref>}} |
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== The flight == |
== The flight == |
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Revision as of 00:48, 31 July 2011
| Accident | |
|---|---|
| Date | December 31, 1968 |
| Summary | Metal fatigue |
| Site | Port Hedland, Western Australia |
| Aircraft | |
| Aircraft type | Vickers Viscount Type 720 |
| Registration | VH-RMQ |
| Flight origin | Perth, Western Australia |
| Destination | Port Hedland, Western Australia |
| Passengers | 21 |
| Crew | 5 |
| Fatalities | 26 (all) |
| Survivors | 0 |
On December 31, 1968 a Vickers Viscount aircraft departed from Perth, Western Australia for a flight of 724 miles (1,165 km) to Port Hedland, Western Australia . On board were two pilots, three air hostesses and twenty-one passengers. The aircraft crashed twenty-eight miles short of its destination with the loss of all lives.[1] Half of the right-hand wing, from outboard of the inner engine to the wingtip, including the outer engine and its propeller, struck the ground about 3,000 feet (910 m) away from the main wreckage site.[2]
| External image | |
|---|---|
 *Photograph of VH-RMQ one month before the crash[3] |
The flight
The Vickers Viscount took off from Perth at 08:36 am local time. After take-off the pilot reported moderate turbulence up to an altitude of 8,000 feet (2,400 m), with “a couple of nasty patches round about five.” The aircraft climbed to 19,000 feet (5,800 m) for the 189 minute flight.[1]
At 11:34 am the pilot advised that the aircraft was 30 miles (48 km) short of its destination and passing 7,000 feet (2,100 m) on descent to Port Hedland airport. No further radio transmission was received from the aircraft. The aircraft’s [flight data recorder]] and cockpit voice recorder show that four seconds after completion of this transmission half of the right-hand wing separated from the aircraft. Twenty-six seconds later the aircraft fuselage struck the ground.[4]
When the crew of the aircraft failed to respond to further radio calls a Cessna 337 aircraft was despatched from Port Hedland airport at 12:12 pm to investigate. Eleven minutes later the pilot of the Cessna reported sighting the burning wreckage. A ground party from Port Hedland arrived at the accident site an hour later and confirmed that none of the occupants had survived the impact.[1]
The wreckage
Accident investigators immediately observed that half of the right-hand wing, still with an engine and propeller attached, had struck the ground a significant distance from the main wreckage. Despite the fact that the half wing had been driven into the rocky ground by the impact it was clear that the wing’s main spar lower boom had fractured in flight, causing immediate separation of the half wing from the remainder of the aircraft.[5]
The investigation
Detailed investigation of the two fracture faces showed that metal fatigue had caused a crack to grow across the wing’s main spar lower boom until it covered approximately 85% of the available cross-section. At this point the wing could no longer support the weight of the aircraft and the outer half of the wing broke free from the inner half.[6]
The fatal fatigue crack in the aluminium main spar lower boom had initiated in the rearmost of five bolt holes for attachment of the right-hand inner engine. These bolt holes were 7⁄8 inch (2.2 cm) diameter. A steel bush was inserted in each bolt hole. Each steel bush was an interference fit in the hole to reduce the effect of metal fatigue and increase the retirement life of the main spar lower boom.
The official retirement life of each main spar lower boom was xxxxx hours. The main spar lower boom in VH-RMQ had been in service for only yyyyy hours. The investigation concentrated on determining why the main spar lower boom had failed significantly before reaching its retirement life.
The investigation determined that the original steel bush in the rearmost of the five holes had been removed and replaced by another bush. The replacement was slightly bell-mouthed as the result of being struck with a conical tool. When the replacement bush had been inserted into the rearmost hole it had broached a small amount of aluminium from the wall of the hole. This broaching action had scored the wall of the hole. The broaching actin also left the diameter of the hole slightly oversize. As a result, the replacement steel bush was not an interference fit it in the hole. Scoring of the wall of the hole and the absence of the interference fit of the bush left the main spar lower boom vulnerable to premature fatigue failure.
Despite exhaustive investigation it was not possible to determine when, or by whom, the original steel bush had been removed and replaced by a bell-mouthed steel bush.