Pulsed eddy current detection of cracks in F/A-18 inner wing spar at large lift-off using modified principal components analysis

摘要

Stress corrosion cracks may develop between fasteners in the aluminum inner wing spars of F/A-18 (CF188 Hornet) aircraft. These fasteners secure carbon-fibre/epoxy composite wing skin, of varying thickness (8 to 21 mm), to the spar. Inspection of the spar through the wing skin is required in order to avoid wing disassembly. A pulsed eddy current system that uses principal component analysis and discriminant analysis to identify cracks has been field tested at the USN North Island facility. The results show that the system can accurately identify cracks in real time throughout the wing. The method is far faster than X-ray radiography and, because it is very portable, can be readily deployed to second or first line facilities. Issues that need to be addressed to improve the performance of the system are identified and potential solutions are examined.