AD 99-21-22 Amendment 39-11367

This amendment adopts a new airworthiness directive (AD), applicable to all Short Brothers Model SD3-30, SD3-60, SD3 SHERPA, and SD3-60 SHERPA series airplanes, that requires a visual inspection to detect corrosion of the shear decks and ribs of the left and right stub wings; follow-on corrective actions, if necessary; and drilling of new drain holes in the lower shear decks. This amendment is prompted by issuance of mandatory continuing airworthiness information by a foreign civil airworthiness authority. The actions specified by this AD are intended to prevent corrosion of the stub wing shear decks and ribs, which could result in cracking or failure of the stub wing structure.