Dutch investigators have confirmed that a Fokker 50 that overran runway 23 at Mogadishu and came to rest on a beach had lost all torque from its left-hand engine during the climb-out from Aden Adde airport.

The aircraft, registered 6O-YAS and operated by Starsky Aviation, was carrying 54 occupants on 10 February when the malfunction occurred. None of them was injured, but the turboprop sustained significant damage in the overrun.

The Dutch Safety Board disclosed the engine failure in its half-year update on the investigation, which Somalia's aircraft accident investigation authority is overseeing.

What happened on departure?

According to the safety board, the Fokker 50 had been climbing out of Aden Adde airport when the torque of its left-hand engine "dropped to zero." The aircraft is fitted with Pratt & Whitney Canada PW125 powerplants.

The flight crew responded by shutting down the affected engine.

"The captain decided to shut down the engine and return to [Mogadishu]," says the safety board.

Why did the aircraft overrun?

The single-engine approach back into Mogadishu ended in an overrun after the aircraft landed on runway 23 in what investigators describe as "gusty wind conditions."

The safety board's account of the landing sequence is direct: "Despite the use of brakes and thrust-reversers, the aircraft could not decelerate sufficiently, resulting in it overrunning the end of the runway."

The aircraft crossed the runway end and stopped on the beach off runway 23's threshold.

What remains unresolved?

Somalia's aircraft accident investigation authority has yet to reach conclusions on the accident. The Dutch Safety Board's half-year update does not assign a cause for the torque loss, the decision-making during the return, or the failure to stop within the runway distance available.

Several questions stay open while the probe continues:

• Why the left-hand PW125's torque dropped to zero during the climb
• Whether the gusty wind conditions materially extended the landing distance
• Whether braking and reverse-thrust performance matched expectations for the conditions
• What role, if any, the runway 23 distance and surface played in the overrun

The significant damage to the airframe and the survival of all 54 occupants make 6O-YAS a hull-loss event by any conventional accounting. Starsky Aviation has not been named in connection with any enforcement action in the material disclosed so far.

The Somali investigation authority will determine whether the engine malfunction, the weather, crew decisions, or a combination of factors produced the overrun. Its final report will carry the conclusions the Dutch Safety Board's interim update deliberately withholds.