Investigators believe the Starbow Airlines ATR 72-500 runway excursion at Ghana's Kotoka airport was preceded by an unexpected slip of the captain's unsecured cockpit seat.
The aircraft – which had only been delivered to Starbow a couple of days before the 25 November accident – had been travelling at around 70kt during its take-off roll.
Preliminary information from the Ghanaian investigation authority, cited by French counterpart BEA, states that the captain's seat "suddenly moved [fully] backwards, violently, and shifted to the left".
The captain had been controlling the aircraft's direction with the nose-wheel steering tiller.
As the seat suddenly moved, the captain turned the tiller to the left, inadvertently steering the turboprop off the left side of the runway.
"The captain could not gain control of the aircraft until it came to a stop close to the perimeter fence, after efforts by the [first officer] to retard the power levers," says BEA.
Five occupants were injured during the accident. The aircraft, which had been bound for Kumasi, sustained damage to components including its left-hand propeller blades and fuselage.