BOAC Flight 781
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| Summary | |
|---|---|
| Date | 10 January 1954 |
| Type | In-flight metal fatigue failure |
| Site | Mediterranean off Elba |
| Passengers | 29 |
| Crew | 6 |
| Injuries | 0 |
| Fatalities | 35 |
| Survivors | 0 |
| Aircraft type | de Havilland DH-106 Comet 1 |
| Operator | British Overseas Airways Corporation |
| Tail number | G-ALYP |
| Flight origin | Kallang Airport, Singapore |
| Last stopover | Ciampino Airport, Rome, Italy |
| Destination | London Heathrow Airport, London, England, United Kingdom |
On 10 January 1954, BOAC Flight 781 a de Havilland Comet 1 (type DH-106), took off from Ciampino Airport in Rome, Italy en route to Heathrow Airport in London, England on the final leg of its flight from Singapore. At about 10:00 GMT, the aircraft suffered an explosive decompression at altitude and crashed into the Mediterranean Sea, killing everyone on board.
The flight was operated by British Overseas Airways Corporation (BOAC) using the aircraft G-ALYP ("Yoke Peter").
Contents |
[edit] Passengers
Of the 29 passengers, 10 were children.[1]
Chester Wilmot, a noted BBC journalist and military historian, boarded the flight.
[edit] Flight and disaster
On 10 January 1954, the flight took off at 09:34 GMT for the final stage flight to London.
At about 09:50 GMT a passing BOAC Argonaut G-ALHJ was in contact with Yoke Peter's Captain, Alan Gibson. During a radio communication about weather conditions, the conversation was abruptly cut-off. The last words heard from Captain Gibson were "George How Jig, did you get my..". About this time wreckage was seen falling into the sea by a fisherman.
[edit] Search, recovery and investigation
At first the task of finding out what happened was like finding a needle in a haystack. In 1954, there were no black boxes, no cockpit voice recorders or flight data recorders so there was no way of knowing what was going on.
An extensive search for the aircraft was organised including the Royal Navy ship HMS Barhill and the civilian salvage vessel Sea Salvor from Malta.
Witnesses to the crash were a group of Italian fishermen who were preparing to do their catch. Upon seeing the plane's remnants falling into the water, the fishermen rushed to the scene to recover the bodies and to find possible survivors, of which there were none. In order to find more evidence concerning the cause of the crash, the bodies were brought to the coroner for autopsy. During the examination, the coroner discovered a distinct pattern of injuries, which were also identified as the cause of death, in most of the victims. These injuries consisted of fractured skulls and ruptured lungs, of which the latter was a sure indicator that the air cabin depressurised because the sudden decrease in pressure would cause the lungs to expand until they rupture. In order to support the theory and also to confirm the cause of the skull fractures, the crash was simulated at the Royal Aircraft Establishment in Farnborough, using the same conditions of the actual plane prior to crash. To do this experiment, a model fuselage was constructed similar to that of the comet. Dummies were also seated within the fuselage to simulate possible movements of passengers during the crash. To simulate the crash, the investigators deliberately ruptured the model by increasing the air pressure within it until it exploded. The movement of the dummies within the air cabin at the moment of explosion was conclusive of skull fracture as they were thrown out of their seats and slammed head-first into the ceiling. Wreckage of the aircraft was eventually found on the sea floor and subsequently raised and transported to the Royal Aircraft Establishment for investigation. Upon examination of the wreckage it became obvious that the aircraft had broken up in mid-air, and initially it was thought that the aircraft might have been brought down by a bomb. Suspicion then shifted to the possibility of an engine turbine explosion and modifications were put in hand to encase the turbine ring in other Comets with armour plate, to contain a possible disintegrating turbine disk. In the meantime, all Comets were to be grounded until these modifications had been carried out. The possibility of failure of the pressure cabin had been considered but then discounted due to the Comet's cabin having been designed to a considerably higher strength than was considered necessary at the time.
While the investigation continued, BOAC desperately tried to get Comets back in service, and on 23rd March it succeeded. BOAC's chairman commented on television, "We obviously wouldn't be flying the Comet with passengers if we weren't satisfied conditions were suitable." But a second BOAC Comet was lost on April 8: a charter flight operating as South African Airways Flight 201 took off from Rome bound for Egypt, with 14 passengers and seven crew. 33 minutes into the flight the pilot reported to be on course flying at 10,000 metres, then all contact was lost.
[edit] Metal fatigue
Initial examination and reconstruction of the wreckage of G-ALYP revealed several signs of inflight break-up:
- Shreds of cabin carpet were found trapped in the remains of the Comet's tail section
- The imprint of a coin was found on a fuselage panel from the rear of the aircraft
- Smears and scoring on the rear fuselage were tested and found to be consistent to the paint applied to the passenger seats of the Comet
When most of the wreckage was recovered, investigators found that fractures started on the roof, a window then smashed into the back elevators, the back fuselage then tore away, the outer wing structure fell, then the outer wing tips and finally the cockpit broke away and fuel from the wings set the debris on fire.
To find out what caused the first failure, BOAC donated G-ALYU ("Yoke Uncle") for testing. The airframe was put in a huge water tank, the tank was filled, and water was pumped into the plane to simulate flight conditions. After the equivalent of only 3,000 flights investigators at the RAE were able to conclude that the crash had been due to failure of the pressure cabin at the forward ADF window in the roof. This 'window' was in fact one of two apertures for the aerials of an electronic navigation system in which opaque fibreglass panels took the place of the window 'glass.' The failure was a result of metal fatigue caused by the repeated pressurisation and de-pressurisation of the aircraft cabin. Another worrying fact was that the supports around the windows were only riveted not glued, as the original specifications for the aircraft had called for. The problem was exacerbated by the punch rivet construction technique employed. Unlike drill riveting, the imperfect nature of the hole created by punch riveting may cause the start of fatigue cracks around the rivet.
The Comet's pressure cabin had been designed to a safety factor comfortably in excess of that required by British Civil Airworthiness Requirements (2.5x P as opposed to the requirement of 1.33x P and an ultimate load of 2x P, P being the cabin 'Proof' pressure) and the accident caused a revision in the estimates of the safe loading strength requirements of airliner pressure cabins.
In addition, it was discovered that the stresses around pressure cabin apertures were considerably higher than had been appreciated, especially around sharp-cornered cut-outs, such as windows. As a result, future jet airliners would feature windows with rounded corners, the curve eliminating a stress concentration. This was a noticeable distinguishing feature of all later models of the Comet.
[edit] Dramatizations
- An episode of Seconds from Disaster, "Crash of the Comet," focused on this and several other Comet crashes.
[edit] See also
[edit] References
- Air Disasters by Stanley Stewart - Arrow Books (UK) 1986/89 - ISBN 0-09-956200-6
- Report of the Public Inquiry into the causes and circumstances of the accident which occurred on the 10th January, 1954, to the Comet aircraft G‐ALYP - Official Report - 1955[1]
- "Seconds From Disaster" " Crash of the Comet" on National Geographic Channel.
[edit] External Link
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