What happened
During a routine flight sequence near Dakar-Yoff Airport, two aircraft collided while navigating the YF VOR waypoint. The first aircraft, an Air Sénégal Twin Otter, was performing a descent from Saint Louis and had been directed to hold an altitude of 3,000 feet while passing over the YF VOR.
Simultaneously, a NAMC YS-11, registered C5-GAA, was operating a scheduled service from Dakar-Yoff to Banjul. The crew of the NAMC YS-11 had been instructed to climb along radial 140 and maintain 2,000 feet over the same waypoint. As both aircraft reached the YF VOR, they struck one another.
Following the impact, the NAMC YS-11 sustained significant damage, including the partial loss of its left wing, but the crew managed to navigate the aircraft back to Dakar-Yoff Airport for a safe landing. Conversely, the Twin Otter entered an uncontrolled descent and crashed into the ocean a few kilometers from the coast. The accident resulted in 3 fatalities among the occupants of the Twin Otter.
Findings
An investigation into the event indicates that the collision occurred because both aircraft occupied the same airspace at the YF VOR waypoint while operating at different assigned altitudes.