Summary
This document revises an earlier proposed airworthiness directive (AD), applicable to all Short Brothers Model SD3-60 series airplanes, that would have required performing an inspection of the shear attachment fitting for the fin-to-fuselage front spar, and of the shear cleat for the fin root rib at the aft spar location for corrosion; reporting inspection results; and performing corrective action, if necessary. This new action revises the proposed rule by adding additional inspection areas, a repetitive borescope (intrascope) inspection, and applicable corrective actions per new Short Brothers information. This new action also revises the proposed rule by deleting the inspection report. The actions specified by this new proposed AD are intended to detect and correct corrosion in the area of the main spar web fittings of the vertical stabilizer, which could result in reduced structural integrity of the vertical stabilizer. This action is intended to address the identified unsafe condition.