Generating Methods of Severe Load Spectra for Airplanes Based on Statistic Analysis in Flight Subjects

Abstract

Nowadays, the mean load spectra is mostly used in fatigue test for aircraft, but it has the defects of long fatigue cycle. The severe load spectra is used instead, which can shorten the test time greatly. In order to meet the demand of full-scale fatigue test for life evaluation and aircraft strength criterion at home and abroad, on the basis of take-off and landing data of an instructional airplane, the task analysis method is combined with statistic analysis method to establish a severe load spectra generation method, and arrange and perfect the spectra generation process. The severe load spectra of each flight subject and all subjects are generated and obtained, including weighted median load spectrum, one time standard deviation spectrum, two times standard deviation spectrum, severe load spectrum with 90% survival probability and 95% confidence coefficient, and total severe load spectrum. The K-S test method is used to verify the rationality of load damage distribution, and the selection method of severe spectra representing take-off and landing is give according to statistical results of equivalent damage calculation. The results show that the method of compiling severe spectra is reasonable and effective, the compilation results can fit the severe spectrum characteristics, and the selected representative take-off and landing can represent the conditions of different severity of flight subjects.

Keywords

• fatigue test
• severe load spectra
• statistic analysis method
• flight subject
• equivalent damage