COMMONWEALTH OF AUSTRALIA (Civil Aviation Regulations 1998), PART 39 - 105 CIVIL AVIATION SAFETY AUTHORITY
SCHEDULE OF AIRWORTHINESS DIRECTIVES
Boeing 747 Series Aeroplanes
AD/B747/52 Lower Fuselage Frames 12/86
Applicability: All models, line numbers 1 to 265.
Requirement: Inspect in accordance with Boeing Alert SB 747-53A2237 Revision 1.
Compliance: Before exceeding 7,000 landings or within the next 500 landings after 31 December 1986 whichever occurs later; and thereafter at intervals not exceeding 3,000 landings.
If the strap and angle reinforcement is accomplished in accordance with the ASB, the repeat inspection interval may be extended to 12,000 landings for reinforced frames only.
Background: Numerous reports have been received from overseas of cracked fuselage frames in the lower lobe in Sections 42 and 46. Cracks have been found as early as 6874 landings.
This Directive implements the intent of the FAA AD, with some local variations. One which should be noted is the requirement to carry out precautionary inspections after reinforcement, to cover the possibility of further cracking in fatigue-damaged structure which has not been replaced.