Airworthiness Directives; Short Brothers Model SD3-60 SHERPA, SD3-SHERPA, and SD3-30 Series Airplanes

This amendment adopts a new airworthiness directive (AD), applicable to all Short Brothers Model SD3-60 SHERPA and SD3-SHERPA series airplanes, and certain Model SD3-30 series airplanes, that requires replacement of existing oxygen system "O" rings with improved wear-resistant "O" rings. 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 the loss of oxygen from the aircraft oxygen system, which could result in an insufficient supply of oxygen being provided to the airplane flight crew and passengers in the event of an emergency.