What happened
On July 4, at approximately 11:30 hrs, a McDonnell Douglas DC-10 operated by THY Air Transport departed from Istanbul for Montdidier. During the initial climb, the aircraft experienced a sudden in-flight decompression at approximately 11:40 hrs. The cockpit crew reported an audible warning and a sudden change in aircraft attitude, characterized by a nose-down movement and a rapid descent.
As the aircraft descended, it entered a high-speed dive, reaching speeds of approximately 430 knots. The aircraft eventually impacted the ground near Montdid and broke up upon impact. There were no fatalities among the crew or passengers, though the aircraft was destroyed.
The investigation
The investigation focused on the structural integrity of the aft cargo door and the mechanism responsible for its closure. Investigators examined the wreckage, the cockpit voice recorder, and the aircraft's maintenance history. Technical analysis involved testing the electric motor of the latch actuator and examining the physical state of the door latches and the vent door.
Investigators also reviewed the loading procedures, noting that the aircraft had undergone last-minute passenger embarkation and cargo loading. The investigation included laboratory testing in Zurich to determine if the actuator could have functioned correctly under the observed conditions.
Findings
Technical examinations revealed that the aft cargo door was not properly closed and locked. Specifically, an incorrect adjustment of the door's locking mechanism—involving the use of shims—resulted in a situation where the latches appeared to be engaged even though they had not achieved the necessary over-center position. This allowed the door to remain effectively unlatched.
As the aircraft climbed, the pressure differential between the cabin and the outside atmosphere caused the door to open. The sudden release of pressure and the subsequent aerodynamic forces caused the door to detach from the airframe. This led to the rapid decompression and the loss of control that resulted in the crash.
Safety action
The investigation led to recommendations regarding the inspection and maintenance of cargo door locking mechanisms. It was emphasized that the procedures for checking the closure and locking of cargo doors must be strictly followed to ensure the latches are fully and correctly engaged.