COMMONWEALTH OF AUSTRALIA (Civil Aviation Regulations 1998), PART 39 - 105 CIVIL AVIATION SAFETY AUTHORITY SCHEDULE OF AIRWORTHINESS DIRECTIVES Boeing 747 Series Aeroplanes AD/B747/18 Lower Cargo Doorway Lower Sill Truss and Latch Support Fitting - Inspection 11/79 Applicability: All models. Document: 1. FAA AD 79-17-02, Amdt. 39-3526; 2. (Boeing SB 747-53-2200 refers). Compliance: As per requirement document No. 1. Background: Overseas it has been found that the 7079-T6 truss and related 7079-T6 latch support fittings on the lower sill of forward and lower cargo doorways can exhibit corrosion, cracking and blocked drainage paths.