Summary
We propose to adopt a new airworthiness directive (AD) for PILATUS Aircraft Ltd. Model PC-7 airplanes. This proposed AD results from mandatory continuing airworthiness information (MCAI) originated by an aviation authority of another country to identify and correct an unsafe condition on an aviation product. The MCAI describes the unsafe condition as stress corrosion cracking on the main frame on frame 11 left and right fittings. We are issuing this proposed AD to require actions to address the unsafe condition on these products.