COMMONWEALTH OF AUSTRALIA (Civil Aviation Regulations 1998), PART 39 - 105 CIVIL AVIATION SAFETY AUTHORITY SCHEDULE OF AIRWORTHINESS DIRECTIVES Boeing 727 Series Aeroplanes AD/B727/124 Fuselage Crown Skin Circumferential Joint BS 1080 Applicability: Model 727-100 and 727-100C aircraft listed in the Requirement document. 2/91 Requirement: Action in accordance with the technical requirements of FAA AD 90-21-10 Amdt 39-6761. Note: Boeing SB 727-53-0109 Rev 1, Rev 2 and Rev 3 refer. Compliance: As specified in the Requirement document with effective date 13 November 1990. Background: Country of origin AD. To detect delamination, cracking, and/or corrosion that may lead to depressurisation.