Summary
We propose to adopt a new airworthiness directive (AD) for certain Cessna Aircraft Company (Cessna) Models 525, 525A, and 525B airplanes. This proposed AD would require you to inspect the lower wing skin structure, forward wing spar, lower fuselage skin, fairings, and the external fairing frames for corrosion; repair any damage found; apply a corrosion inhibitive sealant to the fuselage fairings before reinstalling; and disable the cockpit mounted pilot relief tube. This proposed AD results from leaking of the cockpit mounted pilot relief tube, which caused corrosion of the airplane structure. We are proposing this AD to detect and correct any damage from corrosion of the airplane structure. Corrosion of the airplane structure could cause structural degradation and lead to structural failure of the airplane with consequent loss of control.