What happened
On March 3, 1974, flight TK981 arrived at Paris-Orly from Istanbul, with the intention of continuing to London. During the turnaround process, which was delayed by approximately 30 minutes, the aircraft underwent refueling and baggage loading. A large number of passengers were on board due to ongoing industrial action at British Airways.
Following the completion of ground operations, the DC-10 departed Orly at roughly 12:30. Shortly after reaching flight level 60, the aircraft experienced a sudden decompression event just before 12:40. This was triggered by the separation and opening of the left-hand aft cargo door. The resulting pressure differential caused the cabin floor to partially collapse, leading to the ejection of several seat units from the fuselage.
The structural failure also severed the control cables for the elevators and horizontal stabilizer, which were routed beneath the cabin floor. Additionally, the number 2 engine lost nearly all power. The aircraft entered a steep nose-down pitch and began to accelerate rapidly. While the crew attempted to manage the descent by reducing power to the remaining engines, the aircraft could not be stabilized. The plane eventually struck the Ermenonville forest, approximately 37 km northeast of Paris. The impact caused the aircraft to disintegrate, resulting in 346 fatalities.
Findings
Investigations concluded that the primary cause was the failure of the aft cargo door latching mechanism to properly secure the door before takeoff. Due to a design flaw, the door appeared closed and locked even though the lock pins were not fully engaged. This error was exacerbated by several contributing factors:
- Incomplete implementation of necessary service bulletins regarding the door mechanism.
- Improper modifications that prevented the lock pins from protruding sufficiently.
- The disabling of the visual warning light on the flight deck, which would have alerted the crew to an unlocked door.
- A lack of visual verification through the door's inspection viewport during ground operations.
Furthermore, the investigation highlighted a critical vulnerability in the aircraft's design: the routing of essential flight control cables beneath the cabin floor made the aircraft susceptible to total control loss following a high-altitude decompression event.