Incident Overview
The aircraft was conducting a cargo flight from Jeddah (JED) to Kano (KAN). The total cargo uplift was 35 tonnes, packed in 13 pallets, with some loose bundles of merchandise loaded in the lower cargo hold. Departure from Jeddah was delayed by thirteen hours due to problems starting the No. 4 engine. The Boeing 707 departed at 13:48 UTC.
In-Flight Events
As the aircraft approached N'Djamena at FL350, around 17:00 UTC, the flight engineer noted a strange smell in the cockpit. The ground engineer and loadmaster, seated in the cargo compartment area, confirmed the smell had persisted around them for some time. It appeared that the area around pallet number 11 was misty. The pallet was sprayed with a fire extinguisher, and the smoke evacuation procedure was carried out, temporarily stopping the fumes.
The aircraft was then halfway between N'Djamena and Kano, with about 40 minutes of flight time remaining. At 18:00, the flight was cleared to descend. Shortly after, the Master Warning sounded, followed one minute later by a Fire Warning. Smoke entered the cabin. A descent was initiated with a descent rate close to 3,000 feet per minute. Later, the pitch trims became ineffective before the aircraft crashed into marshland.
Wreckage and Impact
Tire ground marks at the accident scene indicated the aircraft descended very slowly into elephant grass and may have somersaulted on contact with water, then exploded and disintegrated along the wreckage trail. Two loadmasters and one crew member were killed. The other two occupants were injured.
Probable Cause
The probable cause of this accident was a heat-generating substance hidden in a cargo of fabrics inside pallet No. 11 in the cargo compartment of the aircraft. The heat emanating from the pallet resulted in smoke that caused a major distraction in the cockpit and later caused an explosion, which seriously impaired the flight controls of the aircraft.