Summary
This document proposes to adopt a new airworthiness directive (AD) that would apply to Aerospace Technologies of Australia Pty Ltd. (ASTA) Models N22B, N24A, and N22S airplanes that are not equipped with a part number (P/N) 1E/N-12-57 fuselage stub fin plate (MOD N759). The proposed action would require replacing the existing fuselage stub fin plate with one of improved design, P/N 1E/N-12-57. Several reports of cracks along the forward flange of the fuselage stub fin plate in the area of Rib Water Line (WL) 138.87 prompted the proposed action. The actions specified by the proposed AD are intended to prevent structural failure of the fuselage area caused by a cracked stub fin plate, which, if not detected and corrected, could result in loss of control of the airplane.