{"id":"F2006B02632","name":"AD/B727/109 Amdt 1 - Fuselage - Aft Lower Lobe Frame","slug":"ad-b727-109-amdt-1-fuselage-aft-lower-lobe-frame","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":41948,"registerId":"commonwealth-F2006B02632-current","compilationNumber":null,"startDate":"2026-04-01","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/B727/109 Amdt 1 - Fuselage - Aft Lower Lobe Frame","content":"---\nmeta-content-style-type: text/css\nmeta-content-type: application/xhtml+xml; charset=utf-8\nmeta-generator: Aspose.Words for .NET 22.10.0\n---\n\n?xml version=\"1.0\" encoding=\"utf-8\" standalone=\"no\"?>\n\nCOMMONWEALTH OF AUSTRALIA (Civil Aviation Regulations 1998), PART 39 - 105 CIVIL AVIATION SAFETY AUTHORITY\n\nSCHEDULE OF AIRWORTHINESS DIRECTIVES\n\n \n\n![](image.001.png)  Boeing 727 Series Aeroplanes\n\n \n\n# AD/B727/109\n\nAmdt 1\n\nApplicability: All Models.\n\n# Fuselage - Aft Lower Lobe Frame 1/93\n\n \n\nRequirement: 1. Visually inspect aircraft for cracks in accordance with Boeing S.B. 727-53-AO195, Revision 1, dated 19 September 1991.\n\n \n\n2. Incorporate the preventative modification specified in Boeing S.B. 727-53-AO195, Revision 1, Accomplishment Instructions, Part II.\n\n \n\nModified areas are exempt from the inspections of 1. above.\n\n \n\nNote: FAA AD 90-06-16, Amendment 39-6545 refers.\n\n \n\nCompliance: 1. (a) If previously inspected in accordance with the original issue of this AD - at intervals not to exceed 4000 flight cycles; otherwise,\n\n \n\n1.  (b) Prior to exceeding 28000 flight cycles, or before 10 June 1993, whichever is the later, and thereafter at intervals not to exceed 4000 flight cycles.\n\n\n \n\n2.    Prior to exceeding 47500 flight cycles, or prior to 9 March 1994, whichever is the later.\n\n \n\nBackground: There have been reports of cracks in aft lower lobe frames in a number of aircraft which had accumulated between 41500 and 59600 flight hours, and between 29800 and 51600 flight cycles. Cracking is attributed to fatigue, and if not repaired could result in cracks in the skin, hence pressurization loss. Severed frames could result in rapid crack growth and subsequent rapid decompression.\n\n \n\nSince the original issue of this AD, further reports of cracking in low time aircraft have necessitated a reduction in the inspection threshold. The FAA has determined that an adequate level of safety cannot be maintained by means of inspection alone, and that the preventative modification should be mandatory. A terminating modification is now also available for stringers S-28 left and right. These changes are reflected in Amendment 1 of this AD.\n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n","sortOrder":0}],"analysis":{"flash_summary_failed":{"failed":true,"reason":"Unauthenticated. Configure AI_GATEWAY_API_KEY or use a provider module. Learn more: https://ai-sdk.dev/unauthenticated-ai-gateway","source":"analysis-cron"},"flash_summary":{"complexity_score":4,"scope_assessment":{"changed":true,"description":"Amendment 1 reduced the inspection threshold for early inspections and made the preventative modification mandatory, and it adds a terminating modification for stringers S‑28 left and right. Modified areas are exempt from further inspections. (See Background; Requirement: 1 & 2; Compliance: 1(a), 1(b), 2.)"},"complexity_factors":["Cross‑reference to an external manufacturer document (Boeing S.B. 727‑53‑AO195, Revision 1) for inspection and modification procedures (Requirement: 1 & 2).","Multiple numeric compliance triggers using flight cycles and hard dates (Compliance: 1(a), 1(b), 2) requiring operator tracking of flight cycles and calendar deadlines.","Distinction between inspection requirement and terminating preventative modification (Requirement: 2; Modified areas exempt from inspections).","Inclusion of a specific terminating modification for stringers S‑28 left and right referenced in Background, adding optional compliance paths.","Regulatory interplay with the FAA AD 90‑06‑16 (Note), creating potential cross‑jurisdictional documentation and conformity issues.","Technical aviation safety context (fatigue cracking, risk of decompression) requiring specialist maintenance capability to execute inspections and modifications (Background & Requirement)."],"plain_english_summary":"This Airworthiness Directive requires all Boeing 727 operators to inspect aft lower‑lobe fuselage frames for cracks per Boeing Service Bulletin 727‑53‑AO195 Rev 1 and to carry out a preventative modification (Part II). Once the modification is fitted the modified areas are exempt from further inspections. Operators pay for inspections and the modification; the Civil Aviation Safety Authority enforces compliance. Inspections and the mandatory modification must be done by the flight‑cycle thresholds and dates specified in the AD."},"kimi_summary":{"content_quality":"ok","complexity_score":3,"scope_assessment":{"changed":false,"description":"This AD remains tightly focused on its original purpose: addressing fatigue cracking in Boeing 727 aft lower lobe frames. Amendment 1 expanded the safety measures (adding mandatory modification, reducing inspection thresholds, adding terminating modification for stringers S-28) but these are responsive refinements within the same technical scope rather than scope creep. The document has not expanded to cover unrelated aircraft systems or airframe areas."},"complexity_factors":["Short, single-purpose document (2 pages) with clear, numbered requirements","Only 3 defined compliance deadlines with straightforward conditional logic ('whichever is the later')","Single cross-reference to FAA AD 90-06-16 for background context only","Minimal defined terms — relies on standard aviation terminology (flight cycles, Service Bulletin)","Simple exemption clause (modified areas exempt from inspection) with no nested conditions","Background section provides plain-language explanation of safety rationale"],"plain_english_summary":"This CASA Airworthiness Directive mandates inspections and a permanent reinforcement for the aft lower lobe frame on all Boeing 727s after fatigue cracks were found that can cause loss of cabin pressure. Operators must perform visual checks per Boeing Service Bulletin every 4,000 flight cycles (or before 28,000 total cycles if applicable) and install the modification by 47,500 cycles or March 1994. After the modification is fitted, the repetitive inspections for that area are no longer required."}},"importantCases":[],"_links":{"self":"/api/acts/ad-b727-109-amdt-1-fuselage-aft-lower-lobe-frame","history":"/api/acts/ad-b727-109-amdt-1-fuselage-aft-lower-lobe-frame/history","analysis":"/api/acts/ad-b727-109-amdt-1-fuselage-aft-lower-lobe-frame/analysis","conflicts":"/api/acts/ad-b727-109-amdt-1-fuselage-aft-lower-lobe-frame/conflicts","importantCases":"/api/acts/ad-b727-109-amdt-1-fuselage-aft-lower-lobe-frame/important-cases","documents":"/api/acts/ad-b727-109-amdt-1-fuselage-aft-lower-lobe-frame/documents"}}