Abstract:

For nearly 20 years, "Rain Flow Counting Method" has been generally used to draw up the aircraft load spectrum over the world.This paper points out that "Rain Flow Counting Method" has serious disadvantages, i.e.it can not consider the sequence of flight load appearance and the loading condition of peak and valley points for each load. Many researches and tests have all proved that the load acting sequence and the loading condition have a great effect on the aircraft stuctural fatigue life. So the load spectrum drawn up by means of "Rain Flow Counting Method" is not accurate enough to aircraft stuctural life determination. The author has studied a new method using the mean lives takeoff and landing of actually measuring Courses to draw up the aircraft F BY F load spectrum, which uses the formula derived in this paper to calculate the mean life of each flight course actually measured, and joining them stochastically, i.e.to draw up the F BY F mean life load spectrum.This spectrum can keep the sequence of flight loads and the loading conditions of load peak and valley points unchanged, so as to increase the accuracy of aircraft structural life determination. By means of this method, load spectra for many types of aircraft have been drawn up and successfully used to make the full scale fatigue tests and life determination for these aircraft, achieving good results.

Key words: mean life, method of draw ing up load spect rum, sequence of load appearance