Summary
This document proposes the adoption of a new airworthiness directive (AD) that is applicable to all Bombardier Model DHC-7 series airplanes. This proposal would require removal of all attachment bolts and pre-load indicating (PLI) washers of the wing-to-fuselage attachment fittings; a one-time visual inspection to detect corrosion of each attachment bolt; and installation of new attachment bolts and PLI washers of the wing-to-fuselage attachment fittings. This proposal is prompted by issuance of mandatory continuing airworthiness information by a foreign civil airworthiness authority. The actions specified by the proposed AD are intended to prevent failure of the attachment bolts of the wing-to-fuselage attachment fittings due to stress corrosion cracking, which could result in reduced structural integrity of the airplane.