Investigation Summary
The accident flight was a ferry leg following the delivery of a cargo of cash from Moscow. During the pre-takeoff checklist, the crew observed alternator failures on engines 1 and 2 but proceeded after the radio operator apparently reactivated them. Within a minute of takeoff, the aircraft's electrical system began to fail catastrophically. The fire, located in the ceiling of the cargo compartment between web frames 15 and 25, caused a cascade of erroneous warnings, including 'too low, gear' while climbing and false door-open indications. The fire eventually caused the fuel supply to engines 1 and 2 to be cut, leading to their automatic shutdown and feathering. The most critical failure occurred when the intense heat from the electrical fire weakened the aileron control cables and rods. In the final moments of the flight, the crew reported they were on final approach, but the aircraft began an uncommanded bank to 32 degrees. The pilots were unable to counter this roll due to the mechanical destruction of the control runs. The aircraft clipped a power line at an altitude of 31 meters and impacted the ground with a high vertical speed of 5,000 feet per minute.
Final Conclusions
The Interstate Aviation Committee (MAK) concluded that the accident was caused by a loss of aircraft roll controllability. This was the direct result of the destruction of aileron control cables and rods due to significant heating from an in-flight fire in the aircraft's electrical network. The fire originated in the cargo compartment ceiling (frames 15-25), though the exact primary source could not be determined due to the extent of the post-crash fire and impact damage. The fire also caused the failure of two engines and multiple flight instruments.
Photographic Evidence (1)
Video Analysis
No video analysis linked for this case file yet.
Airframe & Maintenance
Crew Experience
Captain
No prior incidents recorded.
Navigator
No prior incidents recorded.
Systems & Failure Modes
Aileron Control Cables
Mechanical cables and rods that transmit pilot input to the ailerons; these were destroyed by intense heat from the electrical fire.
Electrical Distribution Network
A complex of bunch-conductors and distributors located in the cargo hold ceiling where the fire originated.
Engine Auto-feather System
Automatically feathered the propellers of engines 1 and 2 when they failed due to fire-induced fuel starvation.
Interesting Facts
- 01The aircraft was 40 years old at the time of the accident, built in 1968.
- 02The fire was located in the ceiling of the cargo compartment between web frames 15 and 25.
- 03The aileron control rod that failed was made of D16-T alloy.
- 04The aircraft was returning to Perm after delivering a cargo of cash to Chelyabinsk.
- 05The vertical speed at impact was approximately 25 meters per second (5,000 feet per minute).
Safety Actions & Advisories
Control Run Thermal Protection
The investigation highlighted the vulnerability of the D16-T alloy control rods and steel cables to localized intense heat from electrical fires. Recommendations were made to review the routing and thermal shielding of primary flight control runs where they pass in close proximity to high-power electrical distribution networks in An-12 aircraft.