Investigation Summary
The fire originated between frames 48 and 50 on the left side of the rear baggage compartment. Investigators determined that a breakdown in wire insulation led to a short circuit and subsequent overheating. As the fire progressed, it caused a massive power failure that deactivated the MS-61B voice recorder and MSRP-64 parametric recorders, leaving the final minutes of the flight unrecorded. The crew initially reported a fire in the auxiliary power unit (APU) and later believed both engines were on fire, though post-crash analysis confirmed the engines were functional and the fire was localized to the baggage area. The landing was complicated by dense fog and the failure of artificial horizons and navigation instruments. The aircraft touched down in deep snow with its gear extended, which caused the legs to sink and break, leading to a series of bounces before the fuselage struck a forest belt and inverted.
Final Conclusions
The investigation concluded that the accident was caused by a short circuit in the electrical installation of the rear baggage compartment due to faulty insulation. No errors were found in the actions of the flight crew, who were praised for maintaining coordination under extreme conditions. The fire ceased only when the aircraft completely lost power just before the final impact.
Video Analysis
No video analysis linked for this case file yet.
Airframe & Maintenance
Systems & Failure Modes
Electrical Wiring
Faulty insulation in the rear baggage compartment (frames 48-50) led to a short circuit and the primary fire.
Flight Recorders
The MS-61B voice recorder and MSRP-64 parametric recorder failed during the emergency due to a total loss of power.
Artificial Horizon
The primary attitude indicators failed 11 seconds after the crew reported an engine fire, forcing the pilots to fly without visual or instrument attitude reference in fog.
Interesting Facts
- 01The fire was caused by a short circuit in electrical wiring due to insulation breakdown.
- 02The aircraft was manufactured in 1972 and had accumulated over 30,000 flying hours.
- 03Dense fog at the diversion airport (Koltsovo) prevented a standard emergency landing.
- 04The flight recorders stopped functioning several minutes before the crash due to the electrical fire.
- 0522 people died at the scene; five more succumbed to injuries later, including two passengers and one crew member.
Safety Actions & Advisories
Electrical Insulation Inspection
Following the investigation, emphasis was placed on the inspection of electrical wiring insulation in the rear baggage compartments of Tu-134 aircraft to prevent short circuits caused by wear or faulty installation.