Incident Sequence
While cruising at night at the assigned altitude of 10,100 metres, approaching the Novokuznetsk reporting point, the captain's daughter entered the cockpit. She was allowed to sit in the left-hand seat while the captain demonstrated autopilot features using HDG/S and NAV submodes to alter heading. The captain's son then took the left front seat. The captain intended to demonstrate the same manoeuvre when his son asked if he could turn the control wheel. The son turned the wheel slightly (applying a force of 8–10 kg) and held it in that position for a few seconds before returning the wheel to neutral. The captain then demonstrated the same features as he did to his daughter and ended by using the NAV submode to bring the aircraft back on course.
As the autopilot attempted to level the aircraft at its programmed heading, it came into conflict with the inputs from the control wheel, which was blocked in a neutral position. Forces on the control wheel increased to 12–13 kg until the torque limiter activated by disconnecting the autopilot servo from the aileron control linkage. The autopilot remained engaged. The aircraft then started to bank to the right at 2.5° per second, reaching 45° when the autopilot was unable to maintain altitude. The A310 started buffeting, which caught the attention of the captain, who told the copilot to take control while he tried to regain his seat. The copilot's seat was fully aft, so it took him an additional 2–3 seconds to reach the control wheel. The bank continued to 90°, the aircraft pitched up steeply with +4.8g accelerations, stalled, and entered a spin. Two minutes and six seconds later, the aircraft struck the ground. The aircraft disintegrated on impact, and all 75 occupants were killed, among them 25 foreigners.
Probable Cause
The official investigation identified the probable cause as a combination of factors: (1) The decision by the pilot in command to allow an unqualified and unauthorized outsider (his son) to occupy his duty station and intervene in flying the aeroplane. (2) The execution of demonstration manoeuvres not anticipated in the flight plan or flight situation, with the pilot operating the autopilot while not at his duty station. (3) Application by the outsider and the copilot of control forces that interfered with the functioning of the roll channel of the autopilot (not recommended in the A310 flight manual), overriding the autopilot and disconnecting it from the aileron control linkage. (4) The copilot and pilot failed to detect the disconnection, probably due to lack of declutch warning, unfamiliarity with declutching function, difficulty detecting by feel, and the pilot being away from his position. (5) A slight unintentional turn of the control wheel after disconnection caused a right roll to develop. (6) The crew failed to detect excessive bank angle and were late in re-entering the control loop, as their attention was focused on determining why the aircraft banked right. (7) The autopilot continued height-keeping after declutching, leading to buffeting and high angles of attack until disconnected. (8) Inappropriate action by the copilot, who failed to disconnect autopilot and push control column forward, causing stall and spin; this could have resulted from the presence of the outsider, poor working posture, unintentional pitch-up, lack of training, and temporary loss of spatial orientation at night.