BOAC Flight 781
Encyclopedia
On 10 January 1954, British Overseas Airways Corporation
Flight 781 a de Havilland DH.106 Comet 1
registered G-ALYP, 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.
, a prominent Australian journalist and military historian working for the BBC
, was one of those killed.
before its final flight.
On 10 January 1954, the flight took off at 09:34 GMT for the final-stage flight to London. 31-year-old Alan Gibson, who served as the captain, was one of the youngest pilots at BOAC.
At about 09:50 GMT a passing BOAC Argonaut
G-ALHJ was in contact with Captain 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.
Heathrow Airport initially listed Flight 781 as being delayed; around 1:30 PM the airport took the flight off the arrivals board.
At first the task of finding out what happened was difficult. 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. Established protocol for aircraft accident investigation did not exist.
An extensive search for the aircraft was organised including the Royal Navy
ship 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 pathologist Antonio Fornari found broken limbs and damaged limbs, which occurred after death. But Fornari also discovered a distinct pattern of injuries, which were identified as the cause of death, in most of the victims. These injuries consisted of fractured skulls and ruptured and otherwise damaged lungs. Fornari found no evidence of an explosion, and he felt confused by the pattern of injuries.
The ruptured lungs were 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.
The following day, the New York Times reported that BOAC had withdrawn all Comets from service.
While the investigation continued, BOAC desperately tried to get Comets back in service, and on 23 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 8 April 1954, a charter flight operating as South African Airways Flight 201
took off from Rome bound for Egypt with 14 passengers and seven crew. Thirty-three minutes into the flight the pilot reported to be on course flying at 10,000 metres, then all contact was lost.
Sir Arnold Hall
, a Cambridge University scholar and scientist, was appointed as the head accident investigator.
Initial examination and reconstruction of the wreckage of G-ALYP revealed several signs of inflight break-up:
When most of the wreckage was recovered, investigators found that fractures started in the roof of the cabin, a window then smashed into the elevators, the rear 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 large water tank, the tank was filled, and water was pumped into the plane to simulate flight conditions. The experiment occurred 24 hours per day, 7 days per week. It could possibly have taken as long as five months. A Seconds From Disaster
documentary episode described this task as "grueling." If the hypothesis was tested in the 2000s, investigators would have used computer technology to determine the effect of pressurization.
After the equivalent of 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 fact was that the supports around the windows were 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 caused manufacturing defect cracks which may have caused the start of fatigue cracks around the rivet. The investigators examined the final piece of wreckage with a regular microscope.
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 anticipated, especially around sharp-cornered cut-outs, such as windows. As a result, future jet airliner
s 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
.
52 years after the incident, Paul Withey, an aviation expert, went to the Science Museum
in London to examine the aircraft parts with 2000s technology. The aircraft piece was mounted on a plate. Withey received an impression of the aircraft part using a silicone-based putty. At Imperial College London
in London Withey used an electron microscope
to examine the putty impression of the fatigue crack. He found a manufacturing defect when zooming to 800 times and confirmed that Sir Arnold Hall's investigation was correct.
British Overseas Airways Corporation
The British Overseas Airways Corporation was the British state airline from 1939 until 1946 and the long-haul British state airline from 1946 to 1974. The company started life with a merger between Imperial Airways Ltd. and British Airways Ltd...
Flight 781 a de Havilland DH.106 Comet 1
De Havilland Comet
The de Havilland DH 106 Comet was the world's first commercial jet airliner to reach production. Developed and manufactured by de Havilland at the Hatfield, Hertfordshire, United Kingdom headquarters, it first flew in 1949 and was a landmark in aeronautical design...
registered G-ALYP, took off from Ciampino Airport
Ciampino Airport
-Access:There is no rail transport at Ciampino Airport. There are direct bus connections both to Roma Termini railway station and to close local stations...
in Rome, Italy, en route to Heathrow Airport in London
London
London is the capital city of :England and the :United Kingdom, the largest metropolitan area in the United Kingdom, and the largest urban zone in the European Union by most measures. Located on the River Thames, London has been a major settlement for two millennia, its history going back to its...
, England
England
England is a country that is part of the United Kingdom. It shares land borders with Scotland to the north and Wales to the west; the Irish Sea is to the north west, the Celtic Sea to the south west, with the North Sea to the east and the English Channel to the south separating it from continental...
, on the final leg of its flight from Singapore
Singapore
Singapore , officially the Republic of Singapore, is a Southeast Asian city-state off the southern tip of the Malay Peninsula, north of the equator. An island country made up of 63 islands, it is separated from Malaysia by the Straits of Johor to its north and from Indonesia's Riau Islands by the...
. At about 10:00 GMT, the aircraft suffered an explosive decompression
Explosive decompression
Uncontrolled decompression refers to an unplanned drop in the pressure of a sealed system, such as an aircraft cabin and typically results from human error, material fatigue, engineering failure or impact causing a pressure vessel to vent into its lower-pressure surroundings or fail to pressurize...
at altitude and crashed into the Mediterranean Sea, killing everyone on board.
Passengers
Of the 29 passengers, 10 were children. Chester WilmotChester Wilmot
Reginald William Winchester Wilmot was an Australian war correspondent who reported for the BBC and the Australian Broadcasting Corporation during the Second World War. After the war he continued to work as a broadcast reporter, and wrote a well-appreciated book about the liberation of Europe...
, a prominent Australian journalist and military historian working for the BBC
BBC
The British Broadcasting Corporation is a British public service broadcaster. Its headquarters is at Broadcasting House in the City of Westminster, London. It is the largest broadcaster in the world, with about 23,000 staff...
, was one of those killed.
Flight and disaster
Gerry Bull, a former BOAC engineer, said that when he inspected the aircraft in Rome he looked for "incidental damage." He did not find any, so he believed Flight 781 was fit for flight. Bull and the same team of engineers later examined South African Airways Flight 201South African Airways Flight 201
South African Airways Flight 201, a de Havilland Comet 1, took off at 18:32 UTC from Ciampino Airport in Rome, Italy en route to Cairo, Egypt, on the second stage of its flight from London to Johannesburg, South Africa. The flight crashed, killing all aboard at around 19:07 UTC on 8 April 1954...
before its final flight.
On 10 January 1954, the flight took off at 09:34 GMT for the final-stage flight to London. 31-year-old Alan Gibson, who served as the captain, was one of the youngest pilots at BOAC.
At about 09:50 GMT a passing BOAC Argonaut
Canadair North Star
The Canadair North Star was a 1940s Canadian development of the Douglas C-54 / DC-4 aircraft. Instead of radial piston engines found on the Douglas design, Canadair employed Rolls-Royce Merlin engines in order to achieve a 35 mph faster cruising speed. The prototype flew on 15 July 1946 and...
G-ALHJ was in contact with Captain 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.
Heathrow Airport initially listed Flight 781 as being delayed; around 1:30 PM the airport took the flight off the arrivals board.
Search, recovery and investigation
That day's edition of The New York Times carried a piece about the accident.At first the task of finding out what happened was difficult. In 1954, there were no black boxes, no cockpit voice recorders
Cockpit voice recorder
A cockpit voice recorder , often referred to as a "black box", is a flight recorder used to record the audio environment in the flight deck of an aircraft for the purpose of investigation of accidents and incidents...
or flight data recorders
Flight data recorder
A flight data recorder is an electronic device employed to record any instructions sent to any electronic systems on an aircraft. It is a device used to record specific aircraft performance parameters...
so there was no way of knowing what was going on. Established protocol for aircraft accident investigation did not exist.
An extensive search for the aircraft was organised including the Royal Navy
Royal Navy
The Royal Navy is the naval warfare service branch of the British Armed Forces. Founded in the 16th century, it is the oldest service branch and is known as the Senior Service...
ship and the civilian salvage vessel Sea Salvor
RFA Sea Salvor (A503)
RFA Sea Salvor was a salvage vessel of the post-war Royal Fleet Auxiliary. She also served as a support ship for Mine Counter Measures vessels....
from Malta
Malta
Malta , officially known as the Republic of Malta , is a Southern European country consisting of an archipelago situated in the centre of the Mediterranean, south of Sicily, east of Tunisia and north of Libya, with Gibraltar to the west and Alexandria to the east.Malta covers just over in...
.
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 pathologist Antonio Fornari found broken limbs and damaged limbs, which occurred after death. But Fornari also discovered a distinct pattern of injuries, which were identified as the cause of death, in most of the victims. These injuries consisted of fractured skulls and ruptured and otherwise damaged lungs. Fornari found no evidence of an explosion, and he felt confused by the pattern of injuries.
The ruptured lungs were a sure indicator that the air cabin depressurised because the sudden decrease in pressure
Explosive decompression
Uncontrolled decompression refers to an unplanned drop in the pressure of a sealed system, such as an aircraft cabin and typically results from human error, material fatigue, engineering failure or impact causing a pressure vessel to vent into its lower-pressure surroundings or fail to pressurize...
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
Royal Aircraft Establishment
The Royal Aircraft Establishment , was a British research establishment, known by several different names during its history, that eventually came under the aegis of the UK Ministry of Defence , before finally losing its identity in mergers with other institutions.The first site was at Farnborough...
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
Royal Aircraft Establishment
The Royal Aircraft Establishment , was a British research establishment, known by several different names during its history, that eventually came under the aegis of the UK Ministry of Defence , before finally losing its identity in mergers with other institutions.The first site was at Farnborough...
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
Turbine
A turbine is a rotary engine that extracts energy from a fluid flow and converts it into useful work.The simplest turbines have one moving part, a rotor assembly, which is a shaft or drum with blades attached. Moving fluid acts on the blades, or the blades react to the flow, so that they move and...
explosion and modifications were put in hand to encase the turbine ring in other Comets with armour
Armour
Armour or armor is protective covering used to prevent damage from being inflicted to an object, individual or a vehicle through use of direct contact weapons or projectiles, usually during combat, or from damage caused by a potentially dangerous environment or action...
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
Cabin pressurization
Cabin pressurization is the pumping of compressed air into an aircraft cabin to maintain a safe and comfortable environment for crew and passengers when flying at altitude.-Need for cabin pressurization:...
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.
The following day, the New York Times reported that BOAC had withdrawn all Comets from service.
While the investigation continued, BOAC desperately tried to get Comets back in service, and on 23 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 8 April 1954, a charter flight operating as South African Airways Flight 201
South African Airways Flight 201
South African Airways Flight 201, a de Havilland Comet 1, took off at 18:32 UTC from Ciampino Airport in Rome, Italy en route to Cairo, Egypt, on the second stage of its flight from London to Johannesburg, South Africa. The flight crashed, killing all aboard at around 19:07 UTC on 8 April 1954...
took off from Rome bound for Egypt with 14 passengers and seven crew. Thirty-three minutes into the flight the pilot reported to be on course flying at 10,000 metres, then all contact was lost.
Sir Arnold Hall
Arnold Alexander Hall
Sir Arnold Alexander Hall FRS was a British aeronautical engineer, scientist, and industrialist.-Life:Hall was born in Liverpool, and attended Alsop High School in Walton, before going to Clare College, Cambridge, where he won several prizes As a postgraduate he worked with Frank Whittle, then...
, a Cambridge University scholar and scientist, was appointed as the head accident investigator.
Metal fatigue
- 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 in the roof of the cabin, a window then smashed into the elevators, the rear 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
Boac
Boac may refer to:* Boac, Marinduque, a municipality in the Southern Philippines* Boac , an American rapper* British Overseas Airways Corporation, a former British state-owned airline...
donated G-ALYU ("Yoke Uncle") for testing. The airframe was put in a large water tank, the tank was filled, and water was pumped into the plane to simulate flight conditions. The experiment occurred 24 hours per day, 7 days per week. It could possibly have taken as long as five months. A Seconds From Disaster
Seconds From Disaster
-By original broadcast date:National Geographic Channel has broadcast many episodes under multiple titles. The title currently or most recently listed on the NGC Calendar is shown first...
documentary episode described this task as "grueling." If the hypothesis was tested in the 2000s, investigators would have used computer technology to determine the effect of pressurization.
After the equivalent of 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
Direction finding
Direction finding refers to the establishment of the direction from which a received signal was transmitted. This can refer to radio or other forms of wireless communication...
window in the roof. This 'window' was in fact one of two apertures for the aerials
Antenna (radio)
An antenna is an electrical device which converts electric currents into radio waves, and vice versa. It is usually used with a radio transmitter or radio receiver...
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
Metal Fatigue
Metal Fatigue , is a futuristic science fiction, real-time strategy computer game developed by Zono Incorporated and published by Psygnosis and TalonSoft .-Plot:...
caused by the repeated pressurisation and de-pressurisation of the aircraft cabin. Another fact was that the supports around the windows were 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 caused manufacturing defect cracks which may have caused the start of fatigue cracks around the rivet. The investigators examined the final piece of wreckage with a regular microscope.
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
Stress (physics)
In continuum mechanics, stress is a measure of the internal forces acting within a deformable body. Quantitatively, it is a measure of the average force per unit area of a surface within the body on which internal forces act. These internal forces are a reaction to external forces applied on the body...
around pressure cabin apertures were considerably higher than had been anticipated, especially around sharp-cornered cut-outs, such as windows. As a result, future jet airliner
Jet airliner
A jet airliner is an airliner that is powered by jet engines. This term is sometimes contracted to jetliner or jet.In contrast to today's relatively fuel-efficient, turbofan-powered air travel, first generation jet airliner travel was noisy and fuel inefficient...
s 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
De Havilland Comet
The de Havilland DH 106 Comet was the world's first commercial jet airliner to reach production. Developed and manufactured by de Havilland at the Hatfield, Hertfordshire, United Kingdom headquarters, it first flew in 1949 and was a landmark in aeronautical design...
.
52 years after the incident, Paul Withey, an aviation expert, went to the Science Museum
Science Museum (London)
The Science Museum is one of the three major museums on Exhibition Road, South Kensington, London in the Royal Borough of Kensington and Chelsea. It is part of the National Museum of Science and Industry. The museum is a major London tourist attraction....
in London to examine the aircraft parts with 2000s technology. The aircraft piece was mounted on a plate. Withey received an impression of the aircraft part using a silicone-based putty. At Imperial College London
Imperial College London
Imperial College London is a public research university located in London, United Kingdom, specialising in science, engineering, business and medicine...
in London Withey used an electron microscope
Electron microscope
An electron microscope is a type of microscope that uses a beam of electrons to illuminate the specimen and produce a magnified image. Electron microscopes have a greater resolving power than a light-powered optical microscope, because electrons have wavelengths about 100,000 times shorter than...
to examine the putty impression of the fatigue crack. He found a manufacturing defect when zooming to 800 times and confirmed that Sir Arnold Hall's investigation was correct.
Dramatizations
- An episode of Seconds from DisasterSeconds From Disaster-By original broadcast date:National Geographic Channel has broadcast many episodes under multiple titles. The title currently or most recently listed on the NGC Calendar is shown first...
, "Crash of the Comet," focused on this and several other Comet crashes.
See also
- List of notable decompression accidents and incidents
- Lists of accidents and incidents on commercial airliners
- List of structural failures and collapses
External links
- "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." - Hosted on the National Transportation Safety BoardNational Transportation Safety BoardThe National Transportation Safety Board is an independent U.S. government investigative agency responsible for civil transportation accident investigation. In this role, the NTSB investigates and reports on aviation accidents and incidents, certain types of highway crashes, ship and marine...
website - Begins on Page 6 of 169 - "Piece reference BT 220/115." - The National Archives
- Flight 781 is in the U.S. Federal Aviation Administration's Lessons Learned From Transport Airplane Accidents library.
- Pre-crash picture of G-ALYP Flight 781