Turkish Airlines Flight 981
Encyclopedia
Turkish Airlines
Flight 981 was a McDonnell Douglas DC-10
, registered TC-JAV and named the Ankara, that crashed in Fontaine-Chaalis
, Oise
, France
, outside Senlis
, on 3 March 1974. Known as the "Ermenonville air disaster", from the forest where the aircraft crashed, the accident resulted in the deaths of all 346 on board.
The crash resulted from the failure of the rear cargo hatch latching system, which allowed the hatch to blow off in flight. This design flaw had been predicted by a Convair
engineer, Dan Applegate
.
The resulting decompression of the cargo hold caused the cabin floor above the hatch to collapse. The flight control cables for the airplane that ran through the floor were severed, leaving the pilots with almost no control over the aircraft. Problems with the latching system and the potential failure mode that led to the crash were known to Convair
, the fuselage's builder, with the information passed on to McDonnell Douglas several years prior to the accident. Changes that addressed the problem had been found, but were not applied to TC-JAV, nor any other aircraft in the DC-10 fleet. McDonnell Douglas instead chose a solution less disruptive to schedules but failed to ensure that personnel were trained to follow the new procedures to ensure the hatch had locked. McDonnell Douglas's reputation and the reputation of the DC-10 were harmed.
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. Flight 981 has the highest death toll of any aviation accident in France and the highest death toll of any accident involving a McDonnell Douglas DC-10 anywhere in the world. It is also the deadliest single plane crash with no survivors.
, and was delivered to the airline in December 1972.
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 due to a strike
by British European Airways
(BEA) employees, many London-bound travelers who had been stranded at Orly were booked onto Flight 981. Among them were 17 English rugby
players who had attended a France-England match the previous day; the flight also carried four British fashion models, and 48 Japan
ese 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
. Shortly thereafter the flight was cleared to flight level
230, and started turning to the west for London. Just after Flight 981 passed over the town of Meaux
, controllers picked up a distorted transmission from the plane; 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 afterwards.
Its wreckage was later found in the Ermenonville Forest
, a state-owned forest at Bosque de Dammartin, in the commune of Fontaine-Chaalis
, Oise
. 6 passengers had been ejected over Saint-Pathus
.
The aircraft had disintegrated. The post-crash fires were small as there were few large pieces of the aircraft left intact to burn. Of the 346 onboard, only 40 bodies were visually identifiable. Nine passengers were never identified.
The wreckage had been so extensively broken up that immediate investigation suggested that a bomb had been placed on-board. Turkish news reports suggested that a group had intended to bomb a BEA aircraft but had switched planes along with the other passengers. Two terrorist groups soon called to claim responsibility.
and British Airways, boarded TK 981 in Paris. As a result the layover, normally one hour, was one hour and thirty minutes.
Most of the passengers were British. Among the British passengers were members of an amateur rugby team and trade union leader James Conway. Japanese embassy sources said that a total of 49 Japanese were on board. Turkish sources said that 15 Turks were on board. Also on board was John Cooper
, who won silver medals in men's 400 meter hurdles and the 4X400 meter relay at the 1964 Summer Olympics
in Tokyo
Among the passengers was Dr. Wayne Wilcox, a cultural attaché of the Embassy of the United States in London
, his wife, and two of his four children. 38 passengers were Japanese university graduates who were touring Europe and were planning to join Japanese firms after the end of their tour.
and cockpit voice recorder
. These 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. At some point, one of the crew pressed his microphone button, broadcasting the pandemonium in the cockpit on the departure frequency.
The aircraft quickly attained a 20 degree nose-down attitude and started picking up speed while Captain Nejat Berkoz and First Officer Oral Ulusman struggled to gain control. As the speed increased the additional lift started to raise the nose again, and Berkoz called "Speed!" and started to push the throttles forward again in order to level off. It was too late, however, and 72 seconds after decompression the airliner slammed into the forest at a speed of about 430 knots (497 miles per hour, or 796 km/h) in a slight left turn. The speed of the impact caused the airliner to disintegrate.
The wreckage was so fragmented that it was difficult to tell whether any parts of the aircraft were missing. An air traffic controller
noted that as the flight was cleared to FL230
, he had briefly seen a second echo on his radar, remaining stationary behind the aircraft. A farmer soon telephoned in, and it was discovered that the rear cargo-hold hatch beneath the floor, portions of the interior floor, and six passenger seats (still holding dead passengers) had landed in a turnip field near the town of Saint-Pathus
, approximately 15 kilometers south of the main crash site.
French investigators determined that the rear cargo hold hatch had failed in flight. When it failed, the cargo area decompressed, but not so in the passenger area above it. The difference in air pressure, several pounds per square inch, caused the floor to fail, blowing a section of the passenger cabin immediately above the hatch out through the open hatch. The control cables, which were beneath the floor, were severed, and the pilots lost control of the airliner's elevator
s, its rudder
, and the number two engine. Without these controls, it was impossible to control the aircraft.
, which prevents the doors from opening while the aircraft is pressurized. The cargo hatch, however, is not. Due to its large radius, the cargo hatch on the DC-10 could not be swung inside the fuselage without taking up a considerable amount of valuable cargo space. Instead, the hatch was swung outward, allowing cargo to be stored directly behind it. The outward-opening hatch allowed it, in the event of a latch failure, to be blown open by the pressure inside the cargo area. To prevent that, the DC-10 used a supposedly fail-safe
latching system held in place by "over top dead center latches" - five C-shaped latches mounted on a common torque shaft that were rotated over latching pins ("spools") fixed to the aircraft fuselage. Due to their shapes, when the latches are in the proper position, pressure on the hatch does not place any torque on them that could cause them to open, and they actually further seat onto the pins.
To ensure this rotation was complete and the latches were in the proper position, the DC-10 cargo hatch design included a separate locking mechanism that consisted of small locking pins that slid through holes on the back of the latches. When the locking pins were in place, any rotation of the latches would jam the pins against the fuselage, making further rotation impossible. The pins were pushed into place by an operating handle on the outside of the hatch. If the latches were not properly closed the pins could not enter the holes and the handle would remain open, visually indicating a problem. Additionally, the handle moved a metal plug into a vent cut in the outer hatch panel: if the vent was not plugged the fuselage would not retain pressure, eliminating any pneumatic force on the hatch. Also, there was an indicator light in the cockpit that would remain lit if the cargo hatch was not correctly latched.
In 1972, American Airlines Flight 96
, another DC-10, had its cargo hatch blow off in flight. In the ensuing investigation it was discovered that the handlers had forced the locking handle closed in spite of the fact that the latches had not rotated completely - because of an electrical problem. The incident investigators discovered that the rod connecting the pins to the handle was weak enough that it could be bent with repeated operation and some force being applied, allowing the baggage handler
to close the handle with his knee in spite of the pins remaining out of their locking holes. Both the vent plug and cockpit light were operated by the handle or the locking pins, not the latches, so when the handle was stowed both of these warning systems indicated that the door was properly closed. In the case of Flight 96, the airliner was able to make a safe emergency landing as not all the underfloor cables had been severed, thus allowing the pilots limited control.
In the aftermath of the Flight 96 incident, the NTSB made several recommendations. Its primary concern was the addition of venting in the rear cabin floor that would ensure that a cargo area decompression would equalize the cabin area, and not place additional loads onto the floor. In fact, most of the DC-10 fuselage had vents like these: it was only the rearmost hold that lacked them. Additionally, the NTSB suggested that upgrades to the locking mechanism and to the latching actuator electrical system be made compulsory. However, while the FAA agreed that the locking and electrical systems should be upgraded, the FAA also agreed with McDonnell Douglas that the additional venting would be too expensive to implement, and the FAA did not demand that this change be made.
Although the DC-10 had been ordered three months after the service bulletin was issued, and it had been delivered to Turkish Airlines three months later, the changes required by the service bulletin had never been implemented. The interconnecting linkage between the lock and the latch hooks had not been upgraded. Through either deliberate fraud or oversight, the construction logs nevertheless showed that this work had been carried out. Mohammed Mahmoudi, the baggage handler who had closed the door on Flight 981, noted that no particular amount of force was needed to close the locking handle. Investigators concluded that the system had already been fatigued in prior flights.
The fix that was implemented by McDonnell Douglas after the American Airlines Flight 96 incident was the addition of a small window that allowed the baggage handlers to visually inspect the pins, confirming they were in the correct position, and placards were added to inform them of proper operation. This modification had been carried out on TC-JAV. However, Mahmoudi had not been advised as to what the indicator window was for. 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. Furthermore, the instructions regarding the indicator window were posted on the aircraft in English and Turkish, but the Algerian-born Mahmoudi, who could read and write three languages fluently, could not read either language.
It was normally the duty of either the airliner's flight engineer or the chief ground engineer of Turkish Airlines 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 members called for Mahmoudi to be arrested, the crash investigators stated that it was unrealistic to expect an untrained, low-paid baggage handler who could not read the warning sticker (due to the language difference) to be responsible for the safety of the aircraft.
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 seal the cargo hatch. 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 as out-of-pocket expenses
by the fuselage's sub-contractor, Convair
. Although Convair had informed McDonnell Douglas of the potential problem, rectifying what the airline considered a small problem with a low probability of occurrence would have seriously disrupted delivery of the aircraft and cost sales so Convair's concerns were ignored. Dan Applegate
was Director of Product Engineering at Convair at the time. His serious reservations about the integrity of the DC-10's cargo latching mechanism are considered a classic case in the field of engineering ethics
.
After Flight 981, a complete re-design of the latching system was finally implemented. The latches themselves were re-designed to prevent them from moving into the wrong positions in the first place. The locking system was mechanically upgraded to prevent the handle from being able to be forced closed without the pins in place, and the vent door operation was changed to be operated by the pins, so that it would properly indicate that the pins were in the locked position, not that the handle was. Additionally, the FAA ordered further changes to all aircraft with outward-opening doors, including the DC-10, Lockheed L-1011
, and Boeing 747
, requiring that vents be cut into the cabin floor to allow pressures to equalize in the event of a blown-out door.
The name given to the crashed DC-10, "Ankara", is still used on an Airbus A340-300
(TC-JDL, MSN: 57) in Star Alliance Livery.
show Mayday
(known as Air Emergency in the US, Mayday in Ireland and Air Crash Investigation in the UK and the rest of world). The episode is entitled "Behind Closed Doors".
It was also featured in Loose Change 9/11: An American Coup.
. An inward-opening hatch (a plug door
) that is unlatched will not fly open, because the difference in air pressure between the aircraft cabin and the air outside will seal the hatch shut. However, an outward-opening, non-plug type hatch needs to be locked shut to prevent any unwanted opening. This makes it particularly important that the locking mechanisms be secure. American Airlines Flight 96
experienced the same problem before the accident of flight 981 happened, but the NTSB's recommendations to prevent it from happening again were not implemented by any airline. As a result, now whenever the NTSB comes up with recommendations to prevent certain accidents from happening, they talk to the FAA, consequently, the FAA may issue an Airworthiness Directive
to help prevent certain types of accidents from happening. However, NTSB and FAA are two independent Federal agencies, and the FAA is not obligated to act on any NTSB recommendation. Aircraft types other than the DC-10 have also experienced catastrophic failures of a hatch. The Boeing 747 has experienced several such incidents, the most noteworthy of which occurred aboard United Airlines Flight 811
in February 1989, when the cargo hatch failed and caused a section of the fuselage to fail, causing the deaths of nine passengers who were expelled from the aircraft. A somewhat similar problem led to a cockpit window being blown out of British Airways Flight 5390
.
Flight 96 because American Airlines had installed a galley above the rear cargo hatch beneath that cabin floor - that reduced the weight on the cabin floor in this location. The galley presumably weighed less than an equivalent number of passengers and their seats sitting in this same location.
Turkish Airlines
Turkish Airlines is the national flag carrier airline of Turkey, headquartered in the Turkish Airlines General Management Building on the grounds of Atatürk Airport in Yeşilköy, Bakirköy district, Istanbul...
Flight 981 was a McDonnell Douglas DC-10
McDonnell Douglas DC-10
The McDonnell Douglas DC-10 is a three-engine widebody jet airliner manufactured by McDonnell Douglas. The DC-10 has range for medium- to long-haul flights, capable of carrying a maximum 380 passengers. Its most distinguishing feature is the two turbofan engines mounted on underwing pylons and a...
, registered TC-JAV and named the Ankara, that crashed in Fontaine-Chaalis
Fontaine-Chaalis
Fontaine-Chaalis is a small village in northern France. It is designated municipally as a commune within the département of Oise.On 3 March 1974 Turkish Airlines Flight 981 crashed in this commune, in the Ermenonville Forest.-References:*...
, Oise
Oise
Oise is a department in the north of France. It is named after the river Oise.-History:Oise is one of the original 83 departments created during the French Revolution on March 4, 1790...
, France
France
The French Republic , The French Republic , The French Republic , (commonly known as France , is a unitary semi-presidential republic in Western Europe with several overseas territories and islands located on other continents and in the Indian, Pacific, and Atlantic oceans. Metropolitan France...
, outside Senlis
Senlis, Oise
Senlis is a French commune located in the Oise department near Paris. It has a long and rich heritage, having traversed centuries of history. This medieval town has welcomed some of the most renowned figures in French history, including Hugh Capet, Louis IX, the Marshall of France, Anne of Kiev and...
, on 3 March 1974. Known as the "Ermenonville air disaster", from the forest where the aircraft crashed, the accident resulted in the deaths of all 346 on board.
The crash resulted from the failure of the rear cargo hatch latching system, which allowed the hatch to blow off in flight. This design flaw had been predicted by a Convair
Convair
Convair was an American aircraft manufacturing company which later expanded into rockets and spacecraft. The company was formed in 1943 by the merger of Vultee Aircraft and Consolidated Aircraft, and went on to produce a number of pioneering aircraft, such as the Convair B-36 bomber, and the F-102...
engineer, Dan Applegate
Dan Applegate
F. D. "Dan" Applegate was Director of Product Engineering for Convair, a McDonnell Douglas subcontractor during the early 1970s. He rose from relative obscurity to become the subject of a classic case in engineering ethics when he penned what became known as the "Applegate Memorandum".On June 12,...
.
The resulting decompression of the cargo hold caused the cabin floor above the hatch to collapse. The flight control cables for the airplane that ran through the floor were severed, leaving the pilots with almost no control over the aircraft. Problems with the latching system and the potential failure mode that led to the crash were known to Convair
Convair
Convair was an American aircraft manufacturing company which later expanded into rockets and spacecraft. The company was formed in 1943 by the merger of Vultee Aircraft and Consolidated Aircraft, and went on to produce a number of pioneering aircraft, such as the Convair B-36 bomber, and the F-102...
, the fuselage's builder, with the information passed on to McDonnell Douglas several years prior to the accident. Changes that addressed the problem had been found, but were not applied to TC-JAV, nor any other aircraft in the DC-10 fleet. McDonnell Douglas instead chose a solution less disruptive to schedules but failed to ensure that personnel were trained to follow the new procedures to ensure the hatch had locked. McDonnell Douglas's reputation and the reputation of the DC-10 were harmed.
The crash of Flight 981 was the deadliest air disaster
Disaster
A disaster is a natural or man-made hazard that has come to fruition, resulting in an event of substantial extent causing significant physical damage or destruction, loss of life, or drastic change to the environment...
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
Japan Airlines Flight 123
Japan Airlines Flight 123 was a Japan Airlines domestic flight from Tokyo International Airport to Osaka International Airport on August 12, 1985. The Boeing 747-146SR that made this route, registered , suffered mechanical failures 12 minutes into the flight and 32 minutes later crashed into two...
in 1985. Flight 981 has the highest death toll of any aviation accident in France and the highest death toll of any accident involving a McDonnell Douglas DC-10 anywhere in the world. It is also the deadliest single plane crash with no survivors.
Aircraft
The aircraft, a DC-10 Series 10 (production designation "Ship 29") was built in Long Beach, CaliforniaLong Beach, California
Long Beach is a city situated in Los Angeles County in Southern California, on the Pacific coast of the United States. The city is the 36th-largest city in the nation and the seventh-largest in California. As of 2010, its population was 462,257...
, and was delivered to the airline in December 1972.
Accident
Flight 981 had flown from IstanbulIstanbul
Istanbul , historically known as Byzantium and Constantinople , is the largest city of Turkey. Istanbul metropolitan province had 13.26 million people living in it as of December, 2010, which is 18% of Turkey's population and the 3rd largest metropolitan area in Europe after London and...
that morning, landing at Paris
Paris
Paris is the capital and largest city in France, situated on the river Seine, in northern France, at the heart of the Île-de-France region...
's Orly International Airport just after 11:00 am local time. The aircraft, a McDonnell Douglas DC-10
McDonnell Douglas DC-10
The McDonnell Douglas DC-10 is a three-engine widebody jet airliner manufactured by McDonnell Douglas. The DC-10 has range for medium- to long-haul flights, capable of carrying a maximum 380 passengers. Its most distinguishing feature is the two turbofan engines mounted on underwing pylons and a...
, 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
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...
's Heathrow Airport, was normally underbooked, but due to a strike
Strike action
Strike action, also called labour strike, on strike, greve , or simply strike, is a work stoppage caused by the mass refusal of employees to work. A strike usually takes place in response to employee grievances. Strikes became important during the industrial revolution, when mass labour became...
by British European Airways
British European Airways
British European Airways or British European Airways Corporation was a British airline which existed from 1946 until 1974. The airline operated European and North African routes from airports around the United Kingdom...
(BEA) employees, many London-bound travelers who had been stranded at Orly were booked onto Flight 981. Among them were 17 English rugby
Rugby football
Rugby football is a style of football named after Rugby School in the United Kingdom. It is seen most prominently in two current sports, rugby league and rugby union.-History:...
players who had attended a France-England match the previous day; the flight also carried four British fashion models, and 48 Japan
Japan
Japan is an island nation in East Asia. Located in the Pacific Ocean, it lies to the east of the Sea of Japan, China, North Korea, South Korea and Russia, stretching from the Sea of Okhotsk in the north to the East China Sea and Taiwan in the south...
ese 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
Paris
Paris is the capital and largest city in France, situated on the river Seine, in northern France, at the heart of the Île-de-France region...
. Shortly thereafter the flight was cleared to flight level
Flight level
A Flight Level is a standard nominal altitude of an aircraft, in hundreds of feet. This altitude is calculated from the International standard pressure datum of 1013.25 hPa , the average sea-level pressure, and therefore is not necessarily the same as the aircraft's true altitude either...
230, and started turning to the west for London. Just after Flight 981 passed over the town of Meaux
Meaux
Meaux is a commune in the Seine-et-Marne department in the Île-de-France region in the metropolitan area of Paris, France. It is located east-northeast from the center of Paris. Meaux is a sub-prefecture of the department and the seat of an arondissement...
, controllers picked up a distorted transmission from the plane; the aircraft's pressurization and overspeed warnings were heard over the pilots' words in Turkish
Turkish language
Turkish is a language spoken as a native language by over 83 million people worldwide, making it the most commonly spoken of the Turkic languages. Its speakers are located predominantly in Turkey and Northern Cyprus with smaller groups in Iraq, Greece, Bulgaria, the Republic of Macedonia, Kosovo,...
, including the co-pilot saying "the fuselage has burst." The flight disappeared from radar shortly afterwards.
Its wreckage was later found in the Ermenonville Forest
Ermenonville Forest
The Ermenonville Forest is a state-owned forest in Oise, France.On 3 March 1974 Turkish Airlines Flight 981 crashed in the forest and in the commune of Fontaine-Chaalis....
, a state-owned forest at Bosque de Dammartin, in the commune of Fontaine-Chaalis
Fontaine-Chaalis
Fontaine-Chaalis is a small village in northern France. It is designated municipally as a commune within the département of Oise.On 3 March 1974 Turkish Airlines Flight 981 crashed in this commune, in the Ermenonville Forest.-References:*...
, Oise
Oise
Oise is a department in the north of France. It is named after the river Oise.-History:Oise is one of the original 83 departments created during the French Revolution on March 4, 1790...
. 6 passengers had been ejected over Saint-Pathus
Saint-Pathus
Saint-Pathus is a commune in the Seine-et-Marne department in the Île-de-France region in north-central France.Saint-Pathus is contiguous with Oissery.-External links:* *...
.
The aircraft had disintegrated. The post-crash fires were small as there were few large pieces of the aircraft left intact to burn. Of the 346 onboard, only 40 bodies were visually identifiable. Nine passengers were never identified.
The wreckage had been so extensively broken up that immediate investigation suggested that a bomb had been placed on-board. Turkish news reports suggested that a group had intended to bomb a BEA aircraft but had switched planes along with the other passengers. Two terrorist groups soon called to claim responsibility.
Passengers
167 passengers flew on the Istanbul to Paris leg, and 50 of them disembarked in Paris. 216 new passengers, many of whom were supposed to fly on Air FranceAir France
Air France , stylised as AIRFRANCE, is the French flag carrier headquartered in Tremblay-en-France, , and is one of the world's largest airlines. It is a subsidiary of the Air France-KLM Group and a founding member of the SkyTeam global airline alliance...
and British Airways, boarded TK 981 in Paris. As a result the layover, normally one hour, was one hour and thirty minutes.
Most of the passengers were British. Among the British passengers were members of an amateur rugby team and trade union leader James Conway. Japanese embassy sources said that a total of 49 Japanese were on board. Turkish sources said that 15 Turks were on board. Also on board was John Cooper
John Cooper (athlete)
John Cooper was a British athlete who competed mainly in the 400 metre hurdles.He competed for Great Britain in the 1964 Summer Olympics held in Tokyo, Japan in the 400 metre hurdles where he won the silver medal...
, who won silver medals in men's 400 meter hurdles and the 4X400 meter relay at the 1964 Summer Olympics
1964 Summer Olympics
The 1964 Summer Olympics, officially known as the Games of the XVIII Olympiad, was an international multi-sport event held in Tokyo, Japan in 1964. Tokyo had been awarded with the organization of the 1940 Summer Olympics, but this honor was subsequently passed to Helsinki because of Japan's...
in Tokyo
Among the passengers was Dr. Wayne Wilcox, a cultural attaché of the Embassy of the United States in London
Embassy of the United States in London
The Embassy of the United States of America to the Court of St. James's has been located since 1960 in the American Embassy London Chancery Building, in Grosvenor Square, Westminster, London...
, his wife, and two of his four children. 38 passengers were Japanese university graduates who were touring Europe and were planning to join Japanese firms after the end of their tour.
Investigation
Investigators were able to retrieve both the flight data recorderFlight 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...
and cockpit voice recorder
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...
. These 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. At some point, one of the crew pressed his microphone button, broadcasting the pandemonium in the cockpit on the departure frequency.
The aircraft quickly attained a 20 degree nose-down attitude and started picking up speed while Captain Nejat Berkoz and First Officer Oral Ulusman struggled to gain control. As the speed increased the additional lift started to raise the nose again, and Berkoz called "Speed!" and started to push the throttles forward again in order to level off. It was too late, however, and 72 seconds after decompression the airliner slammed into the forest at a speed of about 430 knots (497 miles per hour, or 796 km/h) in a slight left turn. The speed of the impact caused the airliner to disintegrate.
The wreckage was so fragmented that it was difficult to tell whether any parts of the aircraft were missing. An air traffic controller
Air traffic controller
Air traffic controllers are the people who expedite and maintain a safe and orderly flow of air traffic in the global air traffic control system. The position of the air traffic controller is one that requires highly specialized skills...
noted that as the flight was cleared to FL230
Flight level
A Flight Level is a standard nominal altitude of an aircraft, in hundreds of feet. This altitude is calculated from the International standard pressure datum of 1013.25 hPa , the average sea-level pressure, and therefore is not necessarily the same as the aircraft's true altitude either...
, he had briefly seen a second echo on his radar, remaining stationary behind the aircraft. A farmer soon telephoned in, and it was discovered that the rear cargo-hold hatch beneath the floor, portions of the interior floor, and six passenger seats (still holding dead passengers) had landed in a turnip field near the town of Saint-Pathus
Saint-Pathus
Saint-Pathus is a commune in the Seine-et-Marne department in the Île-de-France region in north-central France.Saint-Pathus is contiguous with Oissery.-External links:* *...
, approximately 15 kilometers south of the main crash site.
French investigators determined that the rear cargo hold hatch had failed in flight. When it failed, the cargo area decompressed, but not so in the passenger area above it. The difference in air pressure, several pounds per square inch, caused the floor to fail, blowing a section of the passenger cabin immediately above the hatch out through the open hatch. The control cables, which were beneath the floor, were severed, and the pilots lost control of the airliner's elevator
Elevator (aircraft)
Elevators are flight control surfaces, usually at the rear of an aircraft, which control the aircraft's orientation by changing the pitch of the aircraft, and so also the angle of attack of the wing. In simplified terms, they make the aircraft nose-up or nose-down...
s, its rudder
Rudder
A rudder is a device used to steer a ship, boat, submarine, hovercraft, aircraft or other conveyance that moves through a medium . On an aircraft the rudder is used primarily to counter adverse yaw and p-factor and is not the primary control used to turn the airplane...
, and the number two engine. Without these controls, it was impossible to control the aircraft.
Cause
The passenger doors on the DC-10 are of the plug door varietyPlug door
A plug door is a door designed to seal itself by taking advantage of pressure difference on its two sides and is typically used on pressurised aircraft...
, which prevents the doors from opening while the aircraft is pressurized. The cargo hatch, however, is not. Due to its large radius, the cargo hatch on the DC-10 could not be swung inside the fuselage without taking up a considerable amount of valuable cargo space. Instead, the hatch was swung outward, allowing cargo to be stored directly behind it. The outward-opening hatch allowed it, in the event of a latch failure, to be blown open by the pressure inside the cargo area. To prevent that, the DC-10 used a supposedly fail-safe
Fail-safe
A fail-safe or fail-secure device is one that, in the event of failure, responds in a way that will cause no harm, or at least a minimum of harm, to other devices or danger to personnel....
latching system held in place by "over top dead center latches" - five C-shaped latches mounted on a common torque shaft that were rotated over latching pins ("spools") fixed to the aircraft fuselage. Due to their shapes, when the latches are in the proper position, pressure on the hatch does not place any torque on them that could cause them to open, and they actually further seat onto the pins.
To ensure this rotation was complete and the latches were in the proper position, the DC-10 cargo hatch design included a separate locking mechanism that consisted of small locking pins that slid through holes on the back of the latches. When the locking pins were in place, any rotation of the latches would jam the pins against the fuselage, making further rotation impossible. The pins were pushed into place by an operating handle on the outside of the hatch. If the latches were not properly closed the pins could not enter the holes and the handle would remain open, visually indicating a problem. Additionally, the handle moved a metal plug into a vent cut in the outer hatch panel: if the vent was not plugged the fuselage would not retain pressure, eliminating any pneumatic force on the hatch. Also, there was an indicator light in the cockpit that would remain lit if the cargo hatch was not correctly latched.
In 1972, American Airlines Flight 96
American Airlines Flight 96
American Airlines Flight 96 was a regular McDonnell Douglas DC-10-10 flight operated by American Airlines. The flight suffered a cargo door failure on 12 June 1972 while flying over Windsor, Ontario; it is thus sometimes referred to as the Windsor incident.The rapid decompression in the cargo hold...
, another DC-10, had its cargo hatch blow off in flight. In the ensuing investigation it was discovered that the handlers had forced the locking handle closed in spite of the fact that the latches had not rotated completely - because of an electrical problem. The incident investigators discovered that the rod connecting the pins to the handle was weak enough that it could be bent with repeated operation and some force being applied, allowing the baggage handler
Baggage handler
In the airline industry, a baggage handler is a person who loads and unloads baggage , and other cargo for transport via aircraft...
to close the handle with his knee in spite of the pins remaining out of their locking holes. Both the vent plug and cockpit light were operated by the handle or the locking pins, not the latches, so when the handle was stowed both of these warning systems indicated that the door was properly closed. In the case of Flight 96, the airliner was able to make a safe emergency landing as not all the underfloor cables had been severed, thus allowing the pilots limited control.
In the aftermath of the Flight 96 incident, the NTSB made several recommendations. Its primary concern was the addition of venting in the rear cabin floor that would ensure that a cargo area decompression would equalize the cabin area, and not place additional loads onto the floor. In fact, most of the DC-10 fuselage had vents like these: it was only the rearmost hold that lacked them. Additionally, the NTSB suggested that upgrades to the locking mechanism and to the latching actuator electrical system be made compulsory. However, while the FAA agreed that the locking and electrical systems should be upgraded, the FAA also agreed with McDonnell Douglas that the additional venting would be too expensive to implement, and the FAA did not demand that this change be made.
Although the DC-10 had been ordered three months after the service bulletin was issued, and it had been delivered to Turkish Airlines three months later, the changes required by the service bulletin had never been implemented. The interconnecting linkage between the lock and the latch hooks had not been upgraded. Through either deliberate fraud or oversight, the construction logs nevertheless showed that this work had been carried out. Mohammed Mahmoudi, the baggage handler who had closed the door on Flight 981, noted that no particular amount of force was needed to close the locking handle. Investigators concluded that the system had already been fatigued in prior flights.
The fix that was implemented by McDonnell Douglas after the American Airlines Flight 96 incident was the addition of a small window that allowed the baggage handlers to visually inspect the pins, confirming they were in the correct position, and placards were added to inform them of proper operation. This modification had been carried out on TC-JAV. However, Mahmoudi had not been advised as to what the indicator window was for. 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. Furthermore, the instructions regarding the indicator window were posted on the aircraft in English and Turkish, but the Algerian-born Mahmoudi, who could read and write three languages fluently, could not read either language.
It was normally the duty of either the airliner's flight engineer or the chief ground engineer of Turkish Airlines 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 members called for Mahmoudi to be arrested, the crash investigators stated that it was unrealistic to expect an untrained, low-paid baggage handler who could not read the warning sticker (due to the language difference) to be responsible for the safety of the aircraft.
Aftermath
The latch of the DC-10 is a study in human factors
Human factors
Human factors science or human factors technologies is a multidisciplinary field incorporating contributions from psychology, engineering, industrial design, statistics, operations research and anthropometry...
, interface design
Interface design
Interface design deals with the process of developing a method for two modules in a system to connect and communicate. These modules can apply to hardware, software or the interface between a user and a machine...
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 seal the cargo hatch. 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 as out-of-pocket expenses
Out-of-pocket expenses
Out-of-pocket expenses are direct outlays of cash which may or may not be later reimbursed.In operating a vehicle, gasoline, parking fees and tolls are considered out-of-pocket expenses for the trip...
by the fuselage's sub-contractor, Convair
Convair
Convair was an American aircraft manufacturing company which later expanded into rockets and spacecraft. The company was formed in 1943 by the merger of Vultee Aircraft and Consolidated Aircraft, and went on to produce a number of pioneering aircraft, such as the Convair B-36 bomber, and the F-102...
. Although Convair had informed McDonnell Douglas of the potential problem, rectifying what the airline considered a small problem with a low probability of occurrence would have seriously disrupted delivery of the aircraft and cost sales so Convair's concerns were ignored. Dan Applegate
Dan Applegate
F. D. "Dan" Applegate was Director of Product Engineering for Convair, a McDonnell Douglas subcontractor during the early 1970s. He rose from relative obscurity to become the subject of a classic case in engineering ethics when he penned what became known as the "Applegate Memorandum".On June 12,...
was Director of Product Engineering at Convair at the time. His serious reservations about the integrity of the DC-10's cargo latching mechanism are considered a classic case in the field of engineering ethics
Engineering ethics
Engineering ethics is the field of applied ethics and system of moral principles that apply to the practice of engineering. The field examines and sets the obligations by engineers to society, to their clients, and to the profession...
.
After Flight 981, a complete re-design of the latching system was finally implemented. The latches themselves were re-designed to prevent them from moving into the wrong positions in the first place. The locking system was mechanically upgraded to prevent the handle from being able to be forced closed without the pins in place, and the vent door operation was changed to be operated by the pins, so that it would properly indicate that the pins were in the locked position, not that the handle was. Additionally, the FAA ordered further changes to all aircraft with outward-opening doors, including the DC-10, Lockheed L-1011
Lockheed L-1011
The Lockheed L-1011 TriStar, commonly referred to as the L-1011 or TriStar, is a medium-to-long range, widebody passenger trijet airliner. It was the third widebody airliner to enter commercial operations, following the Boeing 747 and the McDonnell Douglas DC-10. Between 1968 and 1984, Lockheed...
, and Boeing 747
Boeing 747
The Boeing 747 is a wide-body commercial airliner and cargo transport, often referred to by its original nickname, Jumbo Jet, or Queen of the Skies. It is among the world's most recognizable aircraft, and was the first wide-body ever produced...
, requiring that vents be cut into the cabin floor to allow pressures to equalize in the event of a blown-out door.
The name given to the crashed DC-10, "Ankara", is still used on an Airbus A340-300
Airbus A340
The Airbus A340 is a long-range four-engine wide-body commercial passenger jet airliner. Developed by Airbus Industrie,A consortium of European aerospace companies, Airbus is now fully owned by EADS and since 2001 has been known as Airbus SAS. a consortium of European aerospace companies, which is...
(TC-JDL, MSN: 57) in Star Alliance Livery.
Dramatization
The story of the disaster was featured on the fifth season of Canadian National Geographic ChannelNational Geographic Channel
National Geographic Channel, also commercially abbreviated and trademarked as Nat Geo, is a subscription television channel that airs non-fiction television programs produced by the National Geographic Society. Like History and the Discovery Channel, the channel features documentaries with factual...
show Mayday
Mayday (TV series)
Mayday, also known as Air Crash Investigation in the United Kingdom, Australia and Asia and Air Emergency and Air Disasters in the United States, is a Canadian documentary television programme produced by Cineflix investigating air crashes, near-crashes and other disasters...
(known as Air Emergency in the US, Mayday in Ireland and Air Crash Investigation in the UK and the rest of world). The episode is entitled "Behind Closed Doors".
It was also featured in Loose Change 9/11: An American Coup.
Similar accidents
Outward-opening cargo hatches are inherently not fail-safeFail-safe
A fail-safe or fail-secure device is one that, in the event of failure, responds in a way that will cause no harm, or at least a minimum of harm, to other devices or danger to personnel....
. An inward-opening hatch (a plug door
Plug door
A plug door is a door designed to seal itself by taking advantage of pressure difference on its two sides and is typically used on pressurised aircraft...
) that is unlatched will not fly open, because the difference in air pressure between the aircraft cabin and the air outside will seal the hatch shut. However, an outward-opening, non-plug type hatch needs to be locked shut to prevent any unwanted opening. This makes it particularly important that the locking mechanisms be secure. American Airlines Flight 96
American Airlines Flight 96
American Airlines Flight 96 was a regular McDonnell Douglas DC-10-10 flight operated by American Airlines. The flight suffered a cargo door failure on 12 June 1972 while flying over Windsor, Ontario; it is thus sometimes referred to as the Windsor incident.The rapid decompression in the cargo hold...
experienced the same problem before the accident of flight 981 happened, but the NTSB's recommendations to prevent it from happening again were not implemented by any airline. As a result, now whenever the NTSB comes up with recommendations to prevent certain accidents from happening, they talk to the FAA, consequently, the FAA may issue an Airworthiness Directive
Airworthiness Directive
An Airworthiness Directive is a notification to owners and operators of certified aircraft that a known safety deficiency with a particular model of aircraft, engine, avionics or other system exists and must be corrected....
to help prevent certain types of accidents from happening. However, NTSB and FAA are two independent Federal agencies, and the FAA is not obligated to act on any NTSB recommendation. Aircraft types other than the DC-10 have also experienced catastrophic failures of a hatch. The Boeing 747 has experienced several such incidents, the most noteworthy of which occurred aboard United Airlines Flight 811
United Airlines Flight 811
United Airlines Flight 811 experienced a cargo door failure in flight on Friday, February 24, 1989, after its stopover at Honolulu International Airport, Hawaii...
in February 1989, when the cargo hatch failed and caused a section of the fuselage to fail, causing the deaths of nine passengers who were expelled from the aircraft. A somewhat similar problem led to a cockpit window being blown out of British Airways Flight 5390
British Airways Flight 5390
British Airways Flight 5390 was a British Airways flight between Birmingham Airport in England and Málaga, Spain. On 10 June 1990 an improperly installed panel of the windscreen failed, blowing the plane's captain, Tim Lancaster, halfway out of the aircraft, with his body firmly pressed against the...
.
See also
- List of notable decompression accidents and incidents
- Loss of control
Footnotes
The control cables were not completely severed on American AirlinesAmerican Airlines
American Airlines, Inc. is the world's fourth-largest airline in passenger miles transported and operating revenues. American Airlines is a subsidiary of the AMR Corporation and is headquartered in Fort Worth, Texas adjacent to its largest hub at Dallas/Fort Worth International Airport...
Flight 96 because American Airlines had installed a galley above the rear cargo hatch beneath that cabin floor - that reduced the weight on the cabin floor in this location. The galley presumably weighed less than an equivalent number of passengers and their seats sitting in this same location.
Further reading
- 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 JobMacarthur JobMacarthur Job is an Australian aviation writer and air safety consultant. He has published nine books on aviation safety...
, Aerospace Publications Pty. Ltd. (Australia), 2001. ISBN 1-875671-11-0, pp. 127–144.
External links
- Final Report, in English. (Archive) - Bureau d'Enquêtes et d'Analyses pour la Sécurité de l'Aviation CivileBureau d'Enquêtes et d'Analyses pour la sécurité de l'Aviation CivileThe Bureau d'Enquêtes et d'Analyses pour la Sécurité de l'Aviation Civile is an agency of the French government, responsible for investigating aviation accidents and making safety recommendations based on what is learned from those investigations. It is headquartered in Building 153 on the grounds...
- Translation made by the French State Secretariat, posted by the Air Accidents Investigation BranchAir Accidents Investigation BranchThe Air Accidents Investigation Branch investigates air accidents in the United Kingdom. It is a branch of the Department for Transport and is based on the grounds of Farnborough Airport near Aldershot, Rushmoor, Hampshire.-History:...
(UK) - Final Report, in French. (Archive) - Bureau d'Enquêtes et d'Analyses pour la Sécurité de l'Aviation Civile