Accident Sequence
A cargo flight from Moscow to Chelyabinsk completed an uneventful landing, after which 9 tons of various goods were deplaned. The aircraft was then ferried to Perm. One minute after takeoff from Chelyabinsk Airport runway 09, while climbing in marginal weather conditions, the crew declared an emergency and reported smoke in the cockpit. Air traffic control cleared the aircraft to return, and the crew completed a circuit.
During a third turn to the left, with a left bank of 15° and at a speed of 335 km/h, both left engines failed and their propellers autofeathered. Approximately 40 seconds later, the aircraft entered a right turn, then descended and crashed in an open field located 11 km from Chelyabinsk Airport. The aircraft burst into flames. The accident occurred 8 minutes after takeoff.
Damage and Occupants
The aircraft was totally destroyed. All 9 occupants were killed.
Probable Cause
The official investigation determined the probable cause to be a loss of controllability due to the destruction of the aileron control cables while carrying out an emergency approach to Chelyabinsk Airport after smoke spread in the cabin and the cockpit. The destruction of aileron wiring occurred, presumably, in the area of the 23-25 web frames of the cargo hold. The reason for the destruction of the wiring installation was most likely a significant heating of a control rod located in this zone, made of alloy D16-T, and its subsequent break under tension-load operation. Heating of the control rod could be a consequence of fire of the aircraft's electricity network, in immediate proximity of the control rod. This led to smoke spread in the cargo hold, unexpected triggering of alarm systems, aircraft equipment failures, and the auto-shutdown of two engines. Electrical bunch-conductors, distributors, blocks and aggregates of the aeronautical equipment, located in the 15-25 frames zone (ceiling of the cargo compartment) came under intense attack by fire. The investigation stated that the primary origin and reason of the fire could not be accurately determined due to the collision with the ground.