Takeoff (climb)

The exact cause of the accident could not be determined and the official accident report was not published by the Senegal Government. Nevertheless, The determination of the causes of the accident is therefore based on the expert reports ordered by the French investigating magistrate and the position of the locking pin of the left supply valve observed after the accident. Experts conclude that the left engine has stopped due to the closing of the fuel supply valve. The poor quality of the fuel was also blamed, which, before the accident, led Air Senegal to ask a chemical engineer from Shell-Senegal to test the fuel and the refueling operations. The engineer, while noting the poor quality of the fuel, came to the same conclusions as the experts. In France, operational tests were carried out on a similar aircraft and, moreover, fuel analyzes were carried out by the Accident Investigation Bureau. To these different expertises were added those of the government of the United Kingdom, the country of the manufacturer of the aircraft, and the results of a test carried out by British Aerospace with the same aircraft. The various analyzes carried out on the drums used for refueling showed that water was not present in the drums but in the pump used for refueling. It appears that the pump had been disassembled and the filters removed before filling the aircraft's tanks. As a result, the tiny amount of water that could have been found in the tanks would not have allowed the fuel to be considered contaminated and therefore unfit for consumption. The court, considering itself sufficiently informed by all these expertises, refused to grant the civil parties a further investigation 12 years after the facts. For the magistrates, there is no doubt that the determining cause of the accident was the closure of the left fuel isolation valve. The various investigations finally made it possible to determine that a ground mechanic had carried out a technical intervention under the left wing before the departure, at the level of the engine, but the exact nature of this intervention could not be established with precision. In its judgment, the court recognized that various indirect causes may have played a role in the occurrence of this air disaster: anomalies in the storage and distribution of fuel, nervousness and intense stress generated around the aircraft due to overbooking, irritability of the captain who, impatient to take off, did not consider certain checks useful. However, the magistrates have ruled, the determining cause perfectly defined by the various experts is the closing of the isolation valve of the left engine of the aircraft. On May 14, 2009, more than 12 years after the incident, Senegalese mechanic Moustapha Diagne was sentenced to 30 months' imprisonment with a 15-month suspended sentence. The length of the firm prison sentence is the length of the pre-trial detention that the defendant, after being extradited, had already served.

The aircraft crashed as a result of the lack of cockpit co-ordination when the pilot-in-command took control of the aircraft as the aircraft was airborne. The following factors contributed to the occurrence: marginal environmental conditions; contaminated runway surface; poor cockpit management; ineffective briefing; and, inadequate training for rejected take-offs.

It was determined that the captain decided to seat on the right front seat, letting the command to the copilot seating in the left front seat, which was against the published procedures because the copilot was not authorized and did not have sufficient experience. The copilot forgot to extend the flaps in an appropriate angle for the takeoff procedure, which caused the aircraft to adopt a critical angle of attack after liftoff and to stall. Successives errors and poor crew coordination were considered as contributing factors as well as the fact that the crew failed to follow the pre-takeoff checklist and failed to identify that the aircraft was not properly configured for the takeoff procedure.

Failure of the pilot-in-command to ensure adequate removal of airframe ice from the aircraft during preflight.

The pilot experienced directional control difficulties during the take-off run, probably because the rudder trim was set at the near full left position. Because the rudder trim indicator could be moved without affecting the actual rudder trim, it is probable that it did not reflect the actual position of the rudder trim.

Failure of the pilot to maintain proper altitude/clearance above the ground after takeoff. A related factor was the pilot's self-induced pressure to depart before the arrival of bad weather.

Failure of the electronic engine control, which caused an overtorque condition in the right engine that made directional control of the airplane not possible by the pilot when the power to the left engine was retarded to idle during the takeoff roll.

It was determined that the aircraft weight was 1,5 ton above MTOW at the time of the accident. Also, it was reported that wings surfaces were contaminated with frost and snow, which was considered as a contributing factor.

The pilot's inadequate compensation for wind conditions, and failure to maintain adequate airspeed, which resulted in an inadvertent stall and collision with terrain (water). A factor associated with the accident was the gusty wind condition.

It was determined that the reverse thrust system on the right engine accidentally deployed after takeoff due to a mechanical failure of unknown origin. Nevertheless, investigations confirmed that a warning light came on in the cockpit prior to departure but the crew failed to identify this warning because he did not follow the pre-departure checklist.