Accident Overview

Photo of airplane wreckage in the forest
Photo of airplane wreckage in the forest

On Sunday March 3, 1974 Flight TK981 departed Istanbul for Paris and London. The DC-10 landed at Paris-Orly at 11:02 and taxied to stand A2. There were 167 passengers on board of whom 50 disembarked. The aircraft was refueled, and baggage was loaded onto the plane. The planned turnaround time of one hour was delayed by 30 minutes. An additional 216 passengers embarked.

Most of the passengers were booked on this flight because of a strike at British Airways. Throughout Europe, the British Airways strike affected nearly all air travel. The Turk-Hava airplane was normally a charter operation that had been pressed into scheduled service in order to compensate for the lack of British Airways flights.

The door of the aft cargo compartment on the left-hand side was closed at about 10:35. When all preparations were complete, the flight received permission to taxi to runway 08 at 12:24. Four minutes later the crew was cleared to line up for departure, and then cleared for departure route 181 and an initial climb to 4000 feet. The aircraft took off at approximately 12:30 hours, and was cleared to climb to 6000 feet, which was reached at 12:34. The North Area Control Center then cleared TK981 further to 23000 feet. Three or four seconds before 12:40:00 hours, the noise of decompression was recorded on the cockpit voice recorder, and the co-pilot said, "the fuselage has burst" as the pressurization aural warning sounded. This was caused by the opening and separation of the aft left-hand cargo door. Because of the pressure difference in the cargo bay and passenger cabin, the floor above the cargo door partly collapsed. Two occupied triple seat units were ejected from the aircraft. All the horizontal stabilizer and elevator control cables, routed beneath the floor of the DC-10, were severed. Thrust control on the number 2 engine was also lost. The aircraft turned nine degree to the left and pitched nose down. The nose-down attitude increased rapidly to -20 deg. Although the numbers 1 and 3 engines were throttled back, the speed increased to 360 knots. The pitch attitude then progressively increased to -4 degrees and the speed increased to 430 knots (800 km/h). In a left bank of 17 degrees, the DC-10 crashed into the forest of Ermenonville, 37 kilometers northeast of Paris.

Six bodies and bits of the fuselage were also found in fields some eight miles from the crash sites. Further analysis of the associated wreckage showed that one of the pieces was the rear cargo door. Investigators found that a support plate, which prevents forced closing of the locking handle and the vent door when the door is not fully latched and locked, was not installed on this door. Maintenance records of modifications accomplished on this airplane by McDonnell-Douglas reflected that the support plate had been installed.

Illustration showing the location of a DC-10-10 aft cargo door
Illustration showing the location of the DC-10-10 aft cargo door

Investigation of the accident revealed that prior to takeoff, the cargo door was not properly latched and locked (see Closing of the Cargo Door) (see NTSB video describing door closure system) and the flight deck aft cargo door warning light (see illustration of flight engineer's panel in the cockpit) went out prematurely because of an incorrectly rigged warning switch.

Illustration of correct and incorrect actuator shaft latching
Illustration of correct and incorrect actuator shaft latching
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Examination of the latch actuator revealed insufficient extension of the actuator shaft (277.5 mm versus 297 mm for full extension). This resulted in the torque tube not rotating far enough to move the latch hooks into the "over-center" position. See DC-10 Cargo Door Latch Flash Animation for an illustration of this process.

Additionally, the lock pins were not properly rigged to engage had the torque tube been properly rotated. The four lock pins on the lock tube were 1.6 mm short of the rear face of the restraining flanges. With the latch hooks not "over center" and the lock pins not engaged, the loads applied to the latch hooks from fuselage internal pressure were transmitted through the latching mechanism to the latch actuator support bracket, failing the two attachment bolts. When the two attachment bolts failed, the detached latch actuator enabled the latch hooks to slip off the latch spools, resulting in the sudden opening of the cargo door.

Photos of recovered Turk Hava aft cargo door
Photos of recovered Turk Hava aft cargo door (source: BEA France)
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Bulk (aft) cargo door lock pin viewing port/placard location
Bulk (aft) cargo door lock pin viewing port/placards location
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Photo of American Airlines DC-10 cargo door remains
Photo of American Airlines DC-10 cargo door remains
The sudden opening of the aft cargo door resulted in a rapid loss of pressurization in that compartment. The cabin floor was not equipped with pressure relief vents. Thus, the loss of the door caused the full differential pressure between the pressurized passenger cabin and the atmosphere to be exerted on the cabin floor over the compartment. This loading failed the floor support structure and the cabin floor collapsed downward into the cargo compartment.

The collapse of the floor severed cables to the empennage control surfaces. The control cables from the cockpit to the empennage control actuators were routed through the cabin floor beams over this cargo compartment. The severed control cables made it impossible to control the aircraft pitch attitude.

The accident report stated that tests on a door with the same definition as that of TC-JAV revealed - due to incorrect adjustment of the lock tube and the bent link between the locking handle and the vent door shaft - that the vent door could be closed without excessive force. The person that closed the aft cargo door stated that he proceeded as usual, without any particular difficulties, and that he did not notice any abnormalities.

Twenty-one months prior to this Turk Hava accident, an American Airlines DC-10 suffered a similar explosive decompression (See Turk Hava/Windsor Comparative Flash Animation) due to the opening of the aft cargo door near Windsor, Ontario, Canada (see summary of the American Airlines DC-10, Windsor accident).

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