Investigation Summary
The accident occurred during the sixth test flight of the first production Tu-144D, an upgraded version of the Soviet supersonic transport featuring more efficient RD-36-51A engines. During the flight, a fuel line ruptured due to high-frequency vibrations (up to 1500Hz) caused by internal fuel flow, a phenomenon that had not been accounted for in the design of the new engine's fuel system. While the failure was systemic to the new RD-36-51A fuel system design, investigators believed the specific leak likely originated from a fuel system hose connected to engine 1. Despite a significant discrepancy of 4.7 tons between the fuel flow meters and the tank quantity gauges, the flight engineers dismissed the readings as sensor errors and did not inform the pilots. As the aircraft descended to 3,000 meters to test the APU, fuel continued to leak at a rate of 220kg/min. The attempt to start the APU provided the ignition source for the accumulated fuel vapors. The resulting fire quickly spread, leading to the sequential shutdown of engines 3, 4, and 1. With only one engine (engine 2) remaining operational, the crew was forced to land in a field near Kladkovo. The aircraft struck trees and slid for 620 meters, coming to rest in flames.
Final Conclusions
The investigation concluded that the primary cause was a fuel leak resulting from the fatigue failure of a fuel pipeline in the power plant zone. Contributing factors included the crew's failure to act on fuel quantity discrepancies and the ignition of leaked fuel by the APU. The disaster effectively ended the Tu-144's short-lived passenger service career, as Aeroflot permanently suspended passenger operations with the type shortly after the crash.
Video Analysis
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Airframe & Maintenance
Systems & Failure Modes
RD-36-51A Engines
New, more efficient turbojets designed for the Tu-144D variant to increase range; the fuel lines for these engines suffered from unforeseen high-frequency vibration fatigue.
Auxiliary Power Unit (APU)
A small turbine engine used to provide power; its start sequence provided the spark that ignited the leaked fuel vapors.
Fuel Quantity Gauges
Instruments that showed a massive discrepancy in fuel levels, which the flight engineers incorrectly dismissed as sensor malfunctions.
Interesting Facts
- 01The aircraft had only 9 total flight hours and 5 previous flights at the time of the accident.
- 02Approximately 8,000 kg (8 tons) of fuel leaked into the wing compartments before ignition.
- 03The two fatalities were flight engineers seated in a compartment that was crushed when the nose cone collapsed during the belly landing.
- 04The crash led to the immediate and permanent cancellation of all Tu-144 passenger services by Aeroflot.
Safety Actions & Advisories
Fuel Pipeline Redesign
New methods were adopted to improve fuel pipeline durability and prevent hydraulic shocks and vibration-induced fatigue.
Tu-144 Passenger Service Ban
Following the crash, the Soviet government banned all passenger flights of the Tu-144, effectively ending its commercial career.