Turkish Airlines Flight 981
From Wikipedia, the free encyclopedia
 CG render of TC-JAV moments after failure seen from the cargo door (the seats actually had passengers in them, not shown).
|
|
| Summary | |
|---|---|
| Date | March 3, 1974 |
| Type | Cargo door failure, control failure |
| Site | Ermenonville, France |
| Passengers | 333 |
| Crew | 13 |
| Injuries | 0 |
| Fatalities | 346 |
| Survivors | 0 |
| Aircraft type | McDonnell Douglas DC-10-10 |
| Aircraft name | Ankara |
| Operator | Turkish Airlines |
| Tail number | TC-JAV |
| Flight origin | Yeşilköy International Airport |
| Last stopover | Orly Airport (Paris) |
| Destination | London Heathrow Airport |
Turkish Airlines Flight 981, registration TC-JAV, was a McDonnell Douglas DC-10 which crashed just outside of Senlis, France, on March 3, 1974. All 346 on board died in the accident.
Contents |
[edit] The accident
Flight 981 had flown from Istanbul that morning, landing at Paris's Orly International Airport just after 11:00 AM local time. The aircraft, a McDonnell Douglas DC-10, was carrying just 167 passengers and 13 crew members in its first leg. 50 passengers disembarked at Paris. The flight's second leg, from Paris to London's Heathrow Airport, was normally underbooked, but owing to a strike by British European Airways employees, many London-bound travelers who had been stranded at Orly were booked onto Flight 981. There were 17 English rugby players who had attended a France-England match the previous day; the flight also carried four British fashion models, 48 Japanese bank management trainees on their way to England, as well as passengers from a dozen other countries.
The aircraft departed Orly at around 12:30 PM for its flight to Heathrow. It took off in an easterly direction, then turned to the north to avoid flying directly over Paris. Just after Flight 981 passed over the town of Meaux, controllers picked up a distorted transmission from Flight 981; the aircraft's pressurization and overspeed warnings were heard over the pilots' words in Turkish, including the co-pilot saying "the fuselage has burst." The flight disappeared from radar shortly thereafter, and its wreckage was later found at the Grove of Dammartin in the Ermenonville forest, close to the town of Senlis.
[edit] The investigation
Examination of the flight data recorder and cockpit voice recorder showed that the first hint the flight crew had of any problem was a muffled explosion that took place just after the aircraft passed over Meaux. The explosion was followed by a loud rush of air, and the throttle for the tail-mounted No. 2 engine snapped shut at the same moment. The aircraft banked and began a descending turn to the left as captain Mejat Berköz and first officer Oral Ulusman tried to control the aircraft. At some point one of the crew pressed his microphone button, broadcasting the pandemonium in the cockpit on the departure frequency. The captain attempted in vain to control the aircraft, but 72 seconds after decompression it slammed into the forest at a speed of 430 knots. Of the 346 onboard, only 40 bodies were visually identifiable. 9 passengers were never identified. The wreckage too was fragmented to the point that it was difficult to tell whether any parts of the aircraft were missing. It was soon discovered, however, that the rear underfloor cargo hold door and six passenger seats (still holding passengers) had landed in a turnip field near the town of St Pathus, approximately 15 kilometres south of the main crash site.
French investigators determined that the rear underfloor cargo hold door had failed in mid-flight. Passenger doors on the DC-10 are of the plug variety, which prevents the doors from opening while the aircraft is pressurized. The cargo door, however, is not. Due to its large area, the cargo door on the DC-10 swung out for loading and was held in place during flight by "over top dead center latches" powered by hydraulic actuators. The latching system was supposed to be made 'fail safe' by a set of features: the over top dead center latches were supposed to be locked by pins which moved behind them when the door locking handle was fully seated; the pins could not be driven home unless the over top dead center latches had in fact gone over top dead center and could not open with pressure behind the door; if the pins were not driven home, there was a vent which would remain open, preventing proper pressurization of the fuselage; and lastly there was an indicator light in the cockpit which would remain on if the door was not correctly latched.
Flight 981's cargo door was faulty (as explained below). Moreover, the baggage handler who closed it on the date in question had not been advised of the meaning or importance of the indicator window.[1] Due to both design and manufacturing flaws, the locking handle could be correctly stowed, and the vent flap closed — and the cockpit warning light turned off — without the locking pins being correctly positioned. The latches were not driven over top dead center by the drive system and failed when the pressure differential between the inside and outside of the aircraft increased as the aircraft climbed. The failure of the door and resulting decompression blew a section of the passenger cabin immediately above the door out of the open hatch and severed the control cables for the elevators, the rudder and the No. 2 engine (which were routed under the floor). This left the crew unable to control those components and led directly to the accident.
When investigators inspected the door, they found that it contained a design flaw that had already been identified and should have been corrected. In 1972, American Airlines Flight 96[2] had suffered a similar cargo door failure; after that incident, McDonnell Douglas issued a service bulletin ordering that changes be made to the latching mechanism so as to prevent any future accident. However, although TC-JAV had been ordered three months after the service bulletin was issued and had been delivered to Turkish Airlines three months later, the changes required by the service bulletin had never been implemented. Moreover, the interconnecting linkage between the lock and the latch hooks had been incorrectly rigged. As a result, only a slight amount of extra force was required to stow the vent flap lever when the latch hooks were not correctly set.
It was normally the duty of either the aircraft's flight engineer or Turkish Airlines's chief ground engineer to ensure that all cargo and passenger doors were securely closed before takeoff. In this case, the airline did not have a ground engineer on duty at the time of the accident, and the flight engineer for Flight 981 failed to check the door personally. Although French media called for the baggage handler (Mr. Mohammed Mahmoudi) to be arrested, investigators stated that it was unrealistic to expect an untrained, low-paid baggage handler who could not read the warning sticker (due to language differences) to be responsible for the safety of the aircraft.
The crash of Flight 981 was the deadliest air disaster of all time before the Tenerife Disaster event of 1977, and remained the deadliest single-airliner disaster until the crash of Japan Airlines Flight 123 in 1985.
The latch of the DC-10 is a study in human factors, interface design and engineering responsibility. The control cables for the rear control surfaces of the DC-10 are routed under the floor, so a failure of the hatch could lead to the collapse of the floor, and disruption of the controls. To make matters worse, Douglas chose a new latch design to close it. If the hatch were to fail for any reason, there was a very high probability the plane would be lost. This possibility was first discovered in 1969 and actually occurred in 1970 in a ground test. Nevertheless, nothing was done to change the design, presumably because the cost for any such changes would have been borne out-of-pocket by the fuselage's main contractor, Convair. Dan Applegate was Director of Product Engineering at Convair at the time. His serious reservations on the integrity of the DC-10's cargo latching mechanism are considered a classic case in engineering ethics.
[edit] Similar accidents
Outward-opening cargo doors are inherently not fail-safe. While an inward opening door (a plug door) which is unlatched will not open due to the difference in pressure between the aircraft cabin and the air outside, an outward opening, non-plug type door needs to be locked shut to prevent unwanted opening. This makes it particularly important that the locking mechanisms be secure. Aircraft types other than the DC-10 have also experienced catastrophic failures of a door; the Boeing 747 has experienced a number of such incidents, the most noteworthy of which occurred aboard United Airlines Flight 811 in February 1989, when the cargo door failed and caused a section of the fuselage to fail, causing the deaths of 9 passengers who were expelled from the aircraft.
[edit] Notable passengers onboard Flight 981
- Hubert 'Jake' Davies and Geoffrey Brigstocke
United Kingdom, Britain's two leading authorities on law-of-the-sea - Francis Hope United Kingdom, European correspondent for The Observer
- Jim Conway United Kingdom, Secretary of Britain's second largest union, the AUEW
- Dr Patrick Hutton United Kingdom, Principal scientific officer at the British Atomic Weapons Research Establishment (AWRE)
- Dr Charles Bowley United Kingdom, an internationally recognised authority on blood transfusion
- Milton Wood United Kingdom, former Mayor of Brighouse, West Yorkshire
- John Cooper - United Kingdom: silver medallist in men's 400 m hurdles and 4 x 400 m relay at the 1964 Summer Olympics in Tokyo [3]
- Dr Wayne Wilcox
United States, serving Cultural attache at the US embassy in London and also chairman of Columbia University's political science department
[edit] See also
[edit] Footnotes
- ^ He had been told that as long as the door latch handle stowed correctly and the vent flap closed at the same time, the door was safe. Moreover, the instructions regarding the indicator window were posted on the aircraft in Turkish and English, but the handler at Orly could only read French and Arabic.
- ^ The control cables were not fully severed on American Airlines Flight 96 because American Airlines had installed a galley above the rear underfloor cargo door which reduced the weight on the cabin floor at that location.
- ^ Wallechinsky, David. (1984). The Complete Book of the Olympics. New York: Penguin Books. pp. 57, 67.
[edit] References and external links
- Final Report, in French.
- Turkish Airlines Flight 981 report from the Aviation Safety Network
- Pre-crash photo taken from Airliners.net courtesy of M.Mailbrink
- Destination Disaster, by Paul Eddy et al., Quadrangle, The New York Times Book Company, 1976 ISBN 0-8129-0619-5.
- The Last Nine Minutes, The Story of Flight 981, by Moira Johnston, Morrow, 1976 ISBN 0-688-03084-X.
- Air Disaster, Vol. 1, by Macarthur Job, Aerospace Publications Pty. Ltd. (Australia), 2001 ISBN 1-875671-11-0, pp. 127-144.
|
|||||||||||||||||||||||||
