Investigation Summary
The flight was operating normally at a cruising altitude of 7,800 meters until it was cleared to descend. During the descent, a spontaneous short circuit in the electrical system triggered the elevator trim tab mechanism, forcing it into a maximum upward deflection. This created an overwhelming nose-down pitch moment. While the trim tab was the initiating mechanical failure, the resulting extreme aerodynamic forces significantly altered the horizontal stabilizer's effectiveness and the aircraft's overall longitudinal stability. The resulting high-speed dive subjected the airframe to significant G-loads, which caused the aircraft's gyroscopic flight instruments to fail. Deprived of reliable attitude information and struggling against the mechanical malfunction, the crew managed a brief recovery at 2,000 meters, but the aircraft quickly entered a secondary stall and spin from which recovery was impossible at such low altitude.
Final Conclusions
The investigation concluded that the primary cause was a spontaneous short circuit in the elevator trim tab control circuit. The failure of the gyroscopic instruments, induced by the stresses of the initial dive, was a significant contributing factor that prevented the crew from maintaining control once they had arrested the initial descent.
Photographic Evidence (1)
Video Analysis
No video analysis linked for this case file yet.
Airframe & Maintenance
Systems & Failure Modes
Elevator Trim Tab
A small surface on the elevator used to reduce control column pressure; a short circuit caused it to deflect fully, forcing the plane into a dive.
Gyroscopic Instruments
The aircraft's attitude indicators failed due to the extreme aerodynamic loads and G-forces experienced during the initial dive.
Interesting Facts
- 01The accident was the deadliest involving a Tupolev Tu-124 at the time of the occurrence.
- 02A short circuit caused the elevator trim tab to deflect and lock in the upward position.
- 03The aircraft's gyroscopic instruments failed during the dive due to the high loads sustained.
- 04Visibility at the time of the crash was 2 to 4 kilometers with haze and cloudy skies.
- 05The passenger list included four prominent Lithuanian pediatricians: Petras Baublys, Liudmila Steponaitienė, Raimondas Lučinskas, and Ona Surplienė, who were traveling to a conference in Kharkiv.
Safety Actions & Advisories
Trim Tab Control Circuit Inspection
Following the investigation's determination that a spontaneous short circuit in the elevator trim tab control circuit caused the loss of control, Aeroflot and the Tupolev Design Bureau initiated inspections of the Tu-124 fleet's electrical wiring and trim mechanisms to prevent similar malfunctions.