Summary
This document proposes to adopt a new airworthiness directive (AD) that would apply to certain Twin Commander Aircraft Corporation (Twin Commander) Models 690C and 695 airplanes. The proposed action would require initially inspecting the wing structure for cracks, modifying any cracked wing structure, and, if not cracked, either repetitively inspecting or modifying the wing structure. Results of full-scale fatigue testing that indicated areas in the wing that are subject to fatigue cracks prompted the proposed action. The actions specified by the proposed AD are intended to prevent wing damage caused by fatigue cracking, which, if not detected and corrected, could progress to the point of structural failure.