Accident Overview
On May 18, 2016, an Antonov An-12B, registration 4K-AZ25, operated by Silk Way Airlines, was conducting a multi-leg flight from Baku, Azerbaijan, to Bagram and Dwyer in Afghanistan, then to Mary, Turkmenistan, and back to Baku. The crew consisted of a captain, first officer, navigator, flight mechanic, flight radio operator, and loadmaster, with two maintenance mechanics and an engineer also on board. During the takeoff from Dwyer Aerodrome, the aircraft overran the runway and was destroyed by a post-crash fire, resulting in seven fatalities and two serious injuries.
Sequence of Events
The flight to Dwyer was uneventful. After landing, the crew started the engines at 09:11:27, with Engine #2 started last at 09:47:37. The captain designated the first officer as pilot flying and himself as pilot monitoring. Taxiing commenced for takeoff on runway heading 229°. The concrete runway measured 2,439 meters by 37 meters. Takeoff weight and center of gravity were within limits. The crew planned to take off with flaps set to 15.
During the takeoff roll, at 09:57:56, the flight mechanic reported an increase in engine gas temperature (MGT) on Engine #3 above acceptable levels. The first officer confirmed the rise. The captain ordered propellers to be locked. Data indicated that propellers on Engines #1, #2, and #4 were locked, but there was no evidence the propeller on Engine #3 was locked.
At 09:59:42, the crew began the takeoff roll. Air traffic control advised wind from 280° at 14 knots, gusting to 26 knots, resulting in a quartering headwind with a headwind component of 5 to 9 m/s. The crew increased thrust on Engines #1 and #4 first, followed by Engine #2 after 10 seconds. The three engines reached approximately 50 kg/sq·cm on the torque indicator, below takeoff power. Engine #3 remained at ground idle. The takeoff roll was initiated near the runway threshold and progressed to the left of the centerline. The rudder was deflected left nearly to the stop.
At an indicated airspeed of approximately 120 km/h, the "Engine #3 negative thrust" signal activated and remained recorded. At 150 km/h, thrust on Engines #1 and #4 was increased to 63 kg/sq·cm, consistent with takeoff power for the conditions. Engine #2 reached this thrust 23 seconds later at about 200 km/h. Engine #3 continued at ground idle. The aircraft reached a maximum speed of 220 km/h. A nose-up input on the control column was recorded about 260 meters before the runway end, but the aircraft did not lift off. It overran the runway onto the ground at 220 km/h.
Aftermath
The aircraft sustained significant damage during the overrun, and a post-crash fire destroyed most of the structure. Of the nine persons on board, seven were killed and two were seriously injured and taken to hospital.