What happened
A cargo flight operating from Jeddah to Kano was delayed for thirteen hours prior to departure due to difficulties starting the number four engine. The Boeing 707 eventually departed at 13:48 UTC carrying 35 tonnes of cargo distributed across 13 pallets and various loose items in the lower hold.
While cruising at FL350 near N'Djamena at approximately 17:00 UTC, the flight engineer detected an unusual odor in the cockpit. This smell was confirmed by the loadmaster and ground engineer located in the cargo area, who observed a misty appearance around pallet number 11. The crew attempted to manage the situation by applying a fire extinguisher to the pallet and performing smoke evacuation procedures, which provided temporary relief from the fumes.
As the aircraft reached the midpoint of the flight between N'Djamena and Kano, the crew received clearance to descend at 18:00. Shortly after, a Master Warning was triggered, followed by a Fire Warning one minute later. Smoke subsequently entered the passenger cabin. The crew began an emergency descent at a rate of nearly 3,000 feet per minute. During the descent, the pitch trims became non-functional, leading to the aircraft impacting marshland. Evidence at the site, including tire marks, suggested a low-speed impact into elephant grass, followed by a somersault, explosion, and disintegration of the airframe.
Findings
The accident resulted in three fatalities, including both loadmasters and one crew member, while the remaining two occupants sustained injuries. The primary factor in the loss of control was the loss of pitch trim effectiveness during the emergency descent following the fire.