Investigation Summary
The flight was the first leg of a long-haul route from Sverdlovsk to Vladivostok. Shortly after takeoff, while the aircraft was maneuvering in cloud cover, a failure in the AC power supply disabled the primary flight instruments. Specifically, the main artificial horizons and the compass system ceased to function correctly. Without visual references or reliable instruments, the crew inadvertently increased their bank angle during a planned left turn. The aircraft's bank reached 75 to 80 degrees, leading to a rapid loss of altitude and control. The investigation highlighted that a similar electrical failure occurred on another Tu-104 just two weeks later, suggesting a systemic vulnerability in the aircraft's electrical architecture.
Final Conclusions
The crash was caused by the failure of the electrical power supply to the main artificial horizons and the compass system. This failure led to incorrect instrument readings while the aircraft was in IMC (Instrument Meteorological Conditions), resulting in the spatial disorientation of the crew and a subsequent loss of control.
Video Analysis
No video analysis linked for this case file yet.
Airframe & Maintenance
Systems & Failure Modes
Artificial Horizon
The primary instrument for determining aircraft attitude; failed due to AC power loss.
Compass System
The directional instruments failed simultaneously with the attitude indicators, leaving the crew without heading reference.
AC Electrical Supply
The failure of this power bus disabled critical flight instruments during a turn in IMC.
Interesting Facts
- 01The aircraft was at full passenger capacity with 100 passengers and 8 crew members.
- 02The crash occurred only four minutes after takeoff.
- 03Visibility at the time of the accident was approximately 6 kilometers with cloud cover.
- 04The aircraft had accumulated 20,582 flight hours and 9,412 cycles prior to the accident.
- 05A nearly identical accident involving another Aeroflot Tu-104 occurred just two weeks later (Flight 964).
Safety Actions & Advisories
Electrical System Redundancy Review
Following the crash and a similar incident two weeks later (Flight 964), investigators recommended improvements to the Tu-104's electrical architecture to prevent a single point of failure in the AC bus from disabling all primary attitude indicators.
Instrument Failure Training
The investigation led to revised training protocols for Aeroflot crews regarding the identification of 'frozen' or erroneous instrument readings during IMC, emphasizing the use of standby instruments.