Investigation Summary
The aircraft was operating the first leg of a Karshi to Leningrad service, with Ufa scheduled as the first intermediate stop. While cruising at 11,600 meters (38,100 ft), the airspeed dropped to 400 km/h, which is near the stall limit for the Tu-154 at that altitude and weight. The stick shaker activated to warn of the impending stall. However, the crew, who had been on duty for 24 hours prior to departure, incorrectly identified the resulting airframe vibrations as engine compressor stalls (surges). They responded by pulling the throttles back to flight idle, which caused the speed to drop further to 290 km/h. The aircraft then entered a flat spin from which recovery was impossible.
Final Conclusions
The investigation concluded that the primary cause was pilot error exacerbated by extreme fatigue. The crew failed to maintain adequate airspeed for the high-altitude cruise and misinterpreted the stall warnings. Contributing factors included the high ambient air temperature, which reduced the aircraft's aerodynamic ceiling, and the crew's lack of experience in handling the Tu-154 in deep stall conditions.
Video Analysis
No video analysis linked for this case file yet.
Airframe & Maintenance
Systems & Failure Modes
Stick Shaker
A mechanical device that rapidly vibrates the control yoke to warn the pilot of an imminent aerodynamic stall.
Flight Data Recorder (FDR)
The device that provided the critical parameters showing the low airspeed and engine power reductions.
Interesting Facts
- 01This remains the deadliest aviation accident in the history of Soviet/Russian aviation and the Tupolev Tu-154.
- 02The flight is commonly, but incorrectly, referred to as Flight 7425. Official Soviet records list it as Flight 5143.
- 03The aircraft was carrying 200 people in total, consisting of 191 passengers (including 52 children) and 9 crew members.
- 04The crew had been awake for over 24 hours due to scheduling delays at the origin airport.
- 05The cockpit voice recorder (CVR) was destroyed in the crash, forcing investigators to rely on FDR data and psychological profiling.
- 06The high outside air temperature significantly lowered the aircraft's aerodynamic ceiling and stall margin at high altitude.
Safety Actions & Advisories
Fatigue Management
The accident highlighted the dangers of crew fatigue in the Soviet civil aviation system, leading to stricter enforcement of rest requirements.
Tu-154 Training
Training programs for Tu-154 pilots were updated to include better recognition of high-altitude stall characteristics versus engine malfunctions.
Location
ACCIDENT SITE · Coordinates taken from the wikidata coordinate.