Aeroflot Flight 846

Investigation

During an inspection of the left D-30KU-154 engine, it was discovered that disk 40-01-577 of the first stage of the low-pressure compressor had failed upon reaching nominal operating conditions. Due to the timely activation of the automatic fire extinguishing system, a fire did not occur when the engine failed.

The Federal State Institution, the State Center for Air Transport Flight Safety, conducted an investigation of the failed disk 40-01-577 and, on October 21, 2008, issued report No. 9297 I/103, concluding that the disk failure was due to high-cycle fatigue. Multiple near-surface fractures were discovered, located in the area of the angle formed by the blade groove and the trailing edge of the disk rim. High-frequency blade vibrations and low-frequency disk vibrations generated during engine operation generated natural disk vibrations, ultimately creating cyclic loading, which in turn led to the development of fatigue cracks. The investigation revealed that the failure zone contained high levels of residual stress due to the preserved fibrous structure, indicating that the disk material was excessively sensitive to loading conditions during operation, resulting in the formation of quasi-brittle fracture zones in the form of a faceted relief that extended considerably. That is, the disk material turned out to be too fragile.

On December 23, 2008, the final report was approved, according to which the destruction of the disk of the first stage of the low-pressure compressor, which led to a serious aviation incident, was not caused by operational irregularities, but by a design and manufacturing defect, that is, it occurred due to the fault of the engine manufacturer, the Saturn Scientific and Production Association.