Abstract: Investigations into multiple domestic and foreign design general specifications and model specifications for aero engines reveal that the regulations and methods for fatigue scatter factors of aero engines are relatively broad without strict definitions and classifications. According to the influences on the engine fatigue life, the fatigue scatter factors for aero engines are categorized into structural scatter factors and load scatter factors, and their definitions are respectively given. We then propose a calculation method for the load scatter factor. Based on the number of start-ups of the main loads and the running time of large states for an aero-engine, the load scatter factor and its variations with the running time are studied. The variation laws of the load scatter factor with the running time under the fixed tasks frequency mixing and the variable tasks frequency mixing are explored using mathematical simulation. Results show that the load scatter factor for the aero-engine is between 1.0 and 2.0, exhibiting a downward trend with the increase of the running time, and its decline rate is related to the nature of the load.

Key words: life of aero engines, fatigue scatter factors, load scatter factors, Weibull distribution, flight tasks frequency mixing