It was March of 1974 and British European Airways ground crews had gone on strike. This action left many United Kingdom-bound passengers stranded in Europe. Many travellers had managed to get to other international airports in hopes of getting a seat on other airlines. On the morning of the 3rd, one such flight that had many empty seats was THY Turkish Airlines flight 981, service from Istanbul to London via Paris. Only 167 passengers were aboard the 345 seat DC-10, 50 of those scheduled to get off in Paris.
......THY Turkish Airlines had been operating the DC-10s for just over a year as the first airline to operate them outside of the USA.

Because of a deal worked out with McDonnell-Douglas and the haste with which the aircraft were introduced into the fleet, initial operation took place with Mc-Donnell-Douglas support personnel aboard every flight to assist crews in learning the intricacies of the technologically advanced aircraft.

......This initial operating experience was long since over, however, when 216 additional London-bound passengers boarded 981 just after noon. Under the command of captain Mejat Berkoz, first officer Oral Ulusman, and flight engineer Huseyin Ozer, 981 taxied out to Orly's runway 08 under clear skies. Just after 12:30pm, 981 climbed out of Orly with Ulusman at the controls and was cleared to FL230. Shortly after, it began its turn on course towards London.

Climbing through 13,00ft, 981's radar label disappeared from ATC's radar screen just as a garbled transmission came over the frequency. In the background, words in Turkish followed by a pressurization warning and then an overspeed warning were heard. Continued calls from ATC went unanswered. Shortly after, calls came in to area police stations reporting a large explosion in the forest north of the Paris area. When rescuers reached the scene, only bits of the aircraft remained intact in the large area cut out by the crash. All 346 people aboard the aircraft were killed.

......Investigators were able to locate both the flight data recorder (FDR) and the cockpit voice recorder (CVR) which were able to reveal many insights about the final moments of the flight of 981. Just as the aircraft was passing through 9,000ft at 300kts, there was a muffled explosion and the sound of air rushing which indicated a sudden decompression. At the same time, the number 2 throttle lever closed and the engine began to spool down. The captain asked what had happened to which Ulusman replied "The fuselage has burst!"

The aircraft began to descend while banking to the left. Berkoz pulled the other throttles back and told Ulusman to bring the nose up to which he responded "I can't bring it up, she's not responding!" By this time, the aircraft was in a 20-degree nose down attitude and was continuing to accelerate. At 32 seconds after the explosion, the aircraft's overspeed warning horn sounded, indicating that the aircraft was about to exceed it's never-exceed speed. Shortly after Ulusman said "We've lost it..." and Berkoz said "It looks like we're going to hit the ground." Another few seconds after this, Berkoz apparently changed his mind and exclaimed "Speed!" as he pushed the throttles forward again. The nose began to rise and the G-forces began to rise as the aircraft tried to recover from it's dive. It was too late however. The aircraft struck the ground some 72 seconds after the explosion at 430kts.

......Because there were no prior indications of a problem and the debris was in small pieces, investigators first believed the accident to have been caused by a bomb. A Turkish media report claimed that a group of passengers had intended to bomb a BEA flight from Paris to London, but had boarded the Turkish aircraft instead when BEA flights were cancelled. Two separate terrorists groups later called in to claim responsibility. However, shortly after the accident, a farmer called claiming that six bodies had fallen into his fields some 8 miles from the crash sites. Bits of the fuselage were also found in the area. The bodies recovered were still strapped into their seats in two rows of three. Examination of the bodies and associated wreckage and revealed no evidence of any bomb residue.

In fact, pathological examination showed that the bodies were in good physical condition and death was entirely a result of impact with the ground. Further analysis of the associated wreckage revealed that one of the pieces was the rear cargo door. This find proved to be the key piece in revealing the cause of the accident.

......Not quite two years earlier, an American Airlines DC-10 had suffered a similar explosive decompression during climbout from Detroit, Michigan. With gentle control inputs and excellent crew coordination, the crew was able to get the aircraft on the ground safely. Once safely on the ground, it became evident that the rear cargo door had opened in flight, partially ripping open the fuselage. The cargo door on the DC-10 was not like older aircraft doors which were bevelled to allow them to shut tighter with cabin pressure. Instead, it incorporated C-latches which locked down on rollers attached to the door sill. All four clamps are locked down with a single electric actuator. In addition, the door has a vent which allows residual pressure to be released on the ground to prevent the door from flying open when it is released.

The vent is operated with a vent flap lever which also slides in locking pins which lock the torque tubes in places, holding the C-latches clamped onto the rollers. When the locking pins are in place, they close micro switches which extinguish "door-open" lights in the cockpit. Finally, the door has a small window which allows handlers to view the latches to ensure their position. In the Detroit case, it was found that the baggage handler had experienced difficulty closing the door. There was low voltage in the actuator so it could not fully drive the C-latches home. The baggage handler could not fully shut the vent flap lever, so he used his knee to put extra force on it. It shut, but was left slightly out of the fully stowed position. Studies showed that the extra force was sufficient to deform the linkage inside the door, jamming the locking pins against the restraining flange and pushing the micro switches closed.

The C-latches never fully stowed however, and because the locking pins could not engage, the door simply blew out as soon as the pressure built up inside the compartment. The NTSB recommended that several changes in the system be implemented to provide better safety in door operation. The FAA began to prepare an Airworthiness Directive which would ground all aircraft until the changes were made. However, Jackson McGowen, then president of the Douglas division of McDonnell-Douglas, approached FAA administrator John Shaffer about downgrading the urgency of the changes. McGowen was worried that the AD would affect the marketing of the aircraft, so Shaffer downgraded the AD to three service bulletins which did not require immediate grounding of the aircraft.

......It was found in the case of 981 that the stiffening of the interconnecting linkage had not been completed as required by one of the service bulletins. The service bulletin had been issued six months before the aircraft was delivered to THY Turkish Airlines. Handling the door on the morning of the 3rd was an Algerian man who had been instructed on how to close the door, but not how to use the window. In any case, the placards on the window were in French and English and he could read neither. He experienced no difficulty closing the door, which was due to already present fatigue on the locking pins. Neither a ground engineer or the flight engineer chose to come out for a final inspection.

A glance in the window would have shown the C-latches were not fully stowed. The difference that caused the tragedy of flight 981 was the cabin configuration above the baggage compartment. Instead of a passenger lounge, there were rows of three, all occupied that day, which imposed a much greater load on the floor. This was evident by the ejection of the six people and seats from the aircraft before the crash. What sealed the fate of the rest of the aircraft was the layout of the DC-10's control cables. The cables ran through the floor area beneath the cabin. When the floor failed after the door blew out, it severely crippled the control system which was evident by the immediate closure of the number 2 throttle. It was not know to what extent controllability was lost, but it appeared to have been great as evidenced by Ulusman's comments in the final moments of the flights.

......The FAA immediately issued an Airworthiness Directive after the crash of flight 981 requiring strengthening of the interconnecting linkage, installation of relief valves to reduce structural loads on the floor of the cabin, and and re-wiring of the actuator to avoid low voltage conditions. This was the first crash of a fully loaded wide-body aircraft and would be but one event in a long history for the DC-10.