Investigation Summary
The flight was operating the second leg of a Baku to Novosibirsk route, having departed Tashkent at 01:25 local time. While cruising at 7,800 metres (25,600 ft) on autopilot, the aircraft experienced a sudden drop in airspeed from 400 to 370 km/h within six seconds. This was followed by a violent descent with vertical overloads fluctuating between 1.5g and -0.8g. Weather at the time consisted of clouds at 1,000 to 1,300 metres, mild wind, rain, and 10 km visibility. Approximately 17 seconds into the upset, the Il-18 entered a steep right bank with an angular velocity exceeding 100 degrees per second. The resulting aerodynamic forces caused the right wing to separate at 5,000 metres, followed by the total breakup of the fuselage at 3,600 metres as the speed reached 700 km/h, well beyond the aircraft's Vne (never-exceed speed) of 675 km/h. The wreckage was found scattered over a wide area, with components like the stabilizers located 3.5 km from the main impact site.
Final Conclusions
The official investigation could not determine the definitive cause of the accident. While the initial 20 to 30 seconds of the descent resembled a controlled emergency maneuver, the subsequent loss of control was inexplicable. Investigators considered the possibility of a crew member accidentally interfering with the elevator controls during an emergency descent, but this could not be proven. Examination of two puncture holes in the rear fuselage initially raised suspicions of a missile strike or internal explosion, but forensic analysis found no explosive residue and concluded the damage occurred during the breakup or impact. The flight data recorders were recovered but were too badly damaged to provide the necessary parameters to solve the mystery.
Video Analysis
No video analysis linked for this case file yet.
Airframe & Maintenance
Systems & Failure Modes
Autopilot
Engaged during the initial speed drop; investigators could not determine if it contributed to the loss of control.
Propeller Feathering System
Found in the feathered state in the wreckage, indicating the engines were likely shut down or failed during the descent.
Elevators
Investigators hypothesized a crew member might have lost control of the elevator during an emergency descent.
Flight Data Recorder
Recovered from the site but sustained significant damage, limiting the data available to investigators.
Interesting Facts
- 01The aircraft was flying on autopilot at the time the upset began.
- 02The propellers were found in the feathered position, though it is unknown if this was a crew action or an automated system response.
- 03The aircraft reached a speed of 700 km/h during the descent, exceeding its structural limit of 675 km/h.
- 04Two local military units confirmed no missiles were fired and no other aircraft were in the area at the time of the crash.
- 05The aircraft had accumulated 21,663 flight hours and 11,787 cycles since its manufacture in 1959.
- 06The aircraft was originally configured for 80 passengers but was later converted to an 89-passenger configuration.