{"id":"F2006B03049","name":"AD/B747/148 Amdt 1 - Fuselage Skin Stringer 12 Lap Joint","slug":"ad-b747-148-amdt-1-fuselage-skin-stringer-12-lap-joint","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":42408,"registerId":"commonwealth-F2006B03049-current","compilationNumber":null,"startDate":"2026-04-01","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/B747/148 Amdt 1 - Fuselage Skin Stringer 12 Lap Joint","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/B747/148\n\nAmdt 1\n\n  \nFuselage Skin Stringer 12 Lap Joint 10/95\n\nApplicability: B747 aircraft Line Number 201 to 230 inclusive.\n\nRequirement: 1. High frequency eddy current inspect the fuselage skin around the upper row of fasteners in the stringer 12L and 12R lap joints. Inspect from Body Station (BS) 520 to BS 741.1 in accordance with Boeing Service Bulletin (SB) 747-53-2366 Accomplishment Instructions, Part I.\n\n    2. Modify the stringer 12L and 12R lap joints by removing the countersunk fasteners and installing raised head fasteners in accordance with Boeing SB 747-53-2366 Accomplishment Instructions, Part III.\n\n    3. Inspect in accordance with Requirement 1.\n\nNote: FAA AD 94-15-17 refers.\n\nCompliance: 1. Pre Requirement 2 modification: Inspect in accordance with Requirement 1 before 15 000 flights or within 1000 flights after 25 May 1995, whichever occurs later.\n\nRe-inspect at intervals not to exceed 4000 flights.\n\n    2. Modify in accordance with Requirement 2 before 20 000 flights or before 25 May 1999 whichever occurs later.\n\n    3. Post Requirement 2 modification: Inspect in accordance with Requirement 1 before 10 000 flights after modification.\n\nRe-inspect at intervals not to exceed 3000 flights.\n\nThis Amendment is effective 14 September 1995.\n\nBackground: The waffle doubler to skin panel bonded joint has, on other aircraft types, experienced disbonding. The countersinks in the three rows of fasteners of the stringer 12 lap joints are deeper than the upper skin panel and multi-site fatigue cracking, leading to a rapid depressurisation, may result. The inspections and modifications of this Directive will assist in maintaining the structural airworthiness of the aircraft.\n\nAmendment 1 corrects the Service Bulletin number called up in Requirement 2. As there is no change to Requirement 1 the Compliance date of 25 May 1995 is unchanged from the original issue of this Directive.","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":5,"scope_assessment":{"changed":false,"description":"Amendment 1 only corrects the Service Bulletin number cited in Requirement 2 and leaves Requirement 1 and the compliance dates unchanged. There is no substantive expansion or narrowing of affected aircraft, inspections, modifications, or timings (Background)."},"complexity_factors":["Technical NDT requirement: high-frequency eddy-current inspection of a specific fuselage area (Requirement 1).","Precise geometric scope: stringer 12L and 12R, skin fasteners between BS 520 and BS 741.1 (Requirement 1).","Modification work‑scope: remove countersunk fasteners and install raised-head fasteners per Boeing SB (Requirement 2).","Flight-based compliance timing and staged reinspection intervals (pre- and post-modification) create planning complexity (Compliance).","Reference to external manufacturer documentation (Boeing Service Bulletin) and cross-reference to an FAA AD increase dependence on outside documents (Requirement 1; Note).","Applicability limited to a narrow subset of airframes (Line Number 201–230) concentrates compliance cost on specific operators (Applicability).","Amendment corrects a procedural citation (Service Bulletin number) rather than altering inspection or compliance obligations (Background).","Safety-critical nature increases recordkeeping and potential operational disruption during inspections/modification (Requirements and Compliance)."],"plain_english_summary":"Requires operators of Boeing 747s (Line Numbers 201–230) to carry out high-frequency eddy-current inspections of the stringer 12L/12R lap joints (BS 520–BS 741.1) and to replace countersunk fasteners with raised-head fasteners per a Boeing Service Bulletin, with flight-based deadlines and recurring inspection intervals. The aim, as stated in the instrument, is to maintain structural airworthiness by finding and preventing multi-site fatigue cracking that could lead to rapid depressurisation."},"kimi_summary":{"content_quality":"ok","complexity_score":3,"scope_assessment":{"changed":false,"description":"This is a minor amendment (Amendment 1) that corrects only the Service Bulletin number reference in Requirement 2. The background, applicability, and all substantive safety requirements remain identical to the original 1995 directive. No expansion of scope has occurred."},"complexity_factors":["Multiple conditional compliance deadlines with 'whichever occurs later' logic","Cross-reference to external technical document (Boeing Service Bulletin 747-53-2366)","Technical aviation terminology requiring domain knowledge (stringer, lap joint, eddy current, body station)","Sequential dependency between requirements (inspection → modification → re-inspection)","Different inspection intervals for pre- and post-modification states"],"plain_english_summary":"This safety order targets Boeing 747s (serials 201–230) to fix a dangerous fuselage flaw at stringer 12: countersunk rivets cut into the skin and, with possible debonding, can allow multiple cracks and sudden cabin decompression. It requires high‑frequency eddy‑current inspections, replacing flush rivets with raised‑head rivets, and recurring checks with specified compliance windows. The amendment only corrects a Boeing bulletin reference and does not change the safety requirements."}},"importantCases":[],"_links":{"self":"/api/acts/ad-b747-148-amdt-1-fuselage-skin-stringer-12-lap-joint","history":"/api/acts/ad-b747-148-amdt-1-fuselage-skin-stringer-12-lap-joint/history","analysis":"/api/acts/ad-b747-148-amdt-1-fuselage-skin-stringer-12-lap-joint/analysis","conflicts":"/api/acts/ad-b747-148-amdt-1-fuselage-skin-stringer-12-lap-joint/conflicts","importantCases":"/api/acts/ad-b747-148-amdt-1-fuselage-skin-stringer-12-lap-joint/important-cases","documents":"/api/acts/ad-b747-148-amdt-1-fuselage-skin-stringer-12-lap-joint/documents"}}