{"id":"F2006B03233","name":"AD/B747/52 - Lower Fuselage Frames","slug":"ad-b747-52-lower-fuselage-frames","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"repealed","isInForce":false,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":42657,"registerId":"commonwealth-F2006B03233-current","compilationNumber":null,"startDate":"2026-04-01","status":"Repealed","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/B747/52 - Lower Fuselage Frames","content":"COMMONWEALTH OF AUSTRALIA (Civil Aviation Regulations 1998), PART 39 \\- 105 CIVIL AVIATION SAFETY AUTHORITY\n\nSCHEDULE OF AIRWORTHINESS DIRECTIVES\n\n![](image.001.png)  \nBoeing 747 Series Aeroplanes\n\nAD/B747/52 Lower Fuselage Frames 12/86\n\nApplicability: All models, line numbers 1 to 265.\n\nRequirement: Inspect in accordance with Boeing Alert SB 747-53A2237 Revision 1.\n\nCompliance: 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.\n\nIf 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.\n\nBackground: 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.\n\nThis 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.","sortOrder":0}],"analysis":{"kimi_summary":{"_metrics":{"model":"kimi-k2.5","source":"moonshot-batch","completionTokens":1664},"content_quality":"ok","complexity_score":3,"scope_assessment":{"changed":false,"description":"This Airworthiness Directive maintains its original 1986 scope, addressing the specific safety issue of fatigue cracking in lower fuselage frames of early Boeing 747 models. It implements the FAA directive with minor local variations regarding post-reinforcement inspections."},"complexity_factors":["Dual-track compliance trigger (7,000 landings vs 500 landings after specific calendar date)","Conditional inspection interval logic (3,000 vs 12,000 landings depending on reinforcement status)","Reference to external technical document (Boeing Alert Service Bulletin 747-53A2237)","Technical aviation terminology requiring domain knowledge (line numbers, fuselage sections, ASB)"],"plain_english_summary":"This mandatory safety directive requires owners/operators of the first 265 Boeing 747s to inspect lower fuselage frames in the bottom half of the airframe for fatigue cracks, following Boeing's service instructions. Initial and repetitive inspection intervals are set (first before 7,000 landings or within 500 landings after 31 Dec 1986, then every 3,000 landings), with reinforcement per Boeing allowing a 12,000‑landing interval only for the reinforced frames.\n\nAustralia’s version keeps extra precautionary inspections after reinforcement to detect new cracks in surrounding metal."}},"importantCases":[],"_links":{"self":"/api/acts/ad-b747-52-lower-fuselage-frames","history":"/api/acts/ad-b747-52-lower-fuselage-frames/history","analysis":"/api/acts/ad-b747-52-lower-fuselage-frames/analysis","conflicts":"/api/acts/ad-b747-52-lower-fuselage-frames/conflicts","importantCases":"/api/acts/ad-b747-52-lower-fuselage-frames/important-cases","documents":"/api/acts/ad-b747-52-lower-fuselage-frames/documents"}}