Damage tolerance analysis of the North American SNJ-6 wing lower attachment angle

Abstract

This paper presents the damage tolerance analysis (DTA) work undertaken by the National Research Council Canada Institute for Aerospace Research (NRC–IAR) for the SNJ-6 wing lower attachment angles and the recommendations on a suitable repeat inspection interval for different usage and nondestructive inspection (NDI) capabilities. NRC–IAR carried out flight and laboratory testing to support the DTA work. Crack growth predictions were conducted using two different MIL-A-008866B spectra (basic and advanced trainer class spectra), three initial crack sizes (0.60, 0.40, and 0.25 in.), and four spectrum clipping values (5.67g, 5.00g, 4.50g, and 4.00g). A total of 24 crack growth scenarios were analyzed. A critical input to the analysis was the aspect ratio of surface crack length to crack depth, which was determined from fractographic images of the failed component. The crack growth and residual strength evaluations estimated the remaining time to failure in a broad range from 1572 h (advanced trainer; maximum...