{"id":"F2006B02686","name":"AD/B727/163 - Lower Fuselage Skin Panels","slug":"ad-b727-163-lower-fuselage-skin-panels","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":42002,"registerId":"commonwealth-F2006B02686-current","compilationNumber":null,"startDate":"2026-04-01","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/B727/163 - Lower Fuselage Skin Panels","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 727 Series Aeroplanes\n\nAD/B727/163 Lower Fuselage Skin Panels 13/99\n\nApplicability: Model 727-100 and \\-100C aircraft, with line numbers listed in FAA AD 99-21-10 applicability.\n\nRequirement: Replace the skin panels of the lower fuselage between body station (BS) 950 and BS1183 with non-bonded skin panels, in accordance with Part IV of the Accomplishment Instructions of Boeing Service Bulletin (SB) 727-53-0085 Revision 4, dated July 11, 1991.\n\nNote 1: Accomplishment of the modification specified in SB 727-53-0085, Revision 2, or Revision 3, is acceptable for compliance with the replacement required by this Directive.\n\nNote 2: Accomplishment of the modifications specified in the Requirement of this Directive constitutes terminating action for the inspection requirements of FAA AD 92-19-10 (AD/B727/127 Amdt 1), for those panels.\n\nNote 3: FAA AD 99-21-10 Amdt 39-11353 refers.\n\nCompliance: Within 20 years since original installation, or within 4 years after 30 December 1999, whichever occurs later.\n\nThis Airworthiness Directive becomes effective on 30 December 1999.\n\nBackground: The FAA received reports of corrosion of the skin panels of the lower fuselage on aircraft with hot-bonded doublers. The actions specified by this Directive are intended to prevent degradation of the structural integrity of certain skin panels of the lower fuselage, which could result in loss of aircraft pressurisation.","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":false,"description":"Scope does not broaden the original technical target. The directive enforces replacement of specified lower fuselage panels on the identified 727-100/-100C aircraft to address corrosion risk, and it expressly terminates prior inspection requirements for those panels (per the Notes and referenced FAA ADs)."},"complexity_factors":["Technical, safety-critical structural work: replacement of lower fuselage skin panels requires certified maintenance personnel and approved procedures.","Cross-references to external documents: mandates Boeing Service Bulletin 727-53-0085 Revision 4 (with Revisions 2 or 3 acceptable) and refers to FAA AD 99-21-10 for applicability.","Applicability limited to specific line numbers and aircraft models, requiring checks of aircraft records to confirm coverage.","Compliance-timing calculation: 'within 20 years since original installation, or within 4 years after 30 December 1999, whichever occurs later' complicates scheduling and tracking.","Operational impact and cost: replacement generates aircraft downtime and parts/labour expense for operators.","Regulatory interaction: the modification constitutes terminating action for inspection requirements of FAA AD 92-19-10, affecting continuing airworthiness obligations."],"plain_english_summary":"This Airworthiness Directive requires operators of certain Boeing 727-100 and 727-100C aircraft to replace lower fuselage skin panels between body station (BS) 950 and BS 1183 with non-bonded panels, following Boeing Service Bulletin instructions. It targets aircraft listed in the FAA AD applicability and aims to prevent corrosion-related loss of pressurisation. Operators must schedule and fund the modification within the stated compliance window; completing it removes specified recurring inspection obligations for those panels."},"kimi_summary":{"content_quality":"ok","complexity_score":2,"scope_assessment":{"changed":false,"description":"This is a targeted safety directive addressing a specific structural corrosion issue in a defined aircraft type. The scope remains precisely limited to the original safety concern — replacement of lower fuselage skin panels on Boeing 727-100 series aircraft — with no expansion into unrelated operational or maintenance areas."},"complexity_factors":["Very short document (approximately 250 words)","Only 2 defined technical terms: 'body station (BS)' and 'hot-bonded doublers' (both explained in context)","Single clear requirement with straightforward compliance deadline","Minimal cross-referencing: only references to specific Boeing Service Bulletin revisions and one related FAA AD","No nested exceptions or conditional logic — just one primary requirement with two acceptable alternative compliance paths (Notes 1 and 2)","Single applicability criterion (specific aircraft models and line numbers)"],"plain_english_summary":"This AD orders operators of certain Boeing 727‑100 and 727‑100C aircraft to replace specific lower fuselage hot‑bonded skin panels with non‑bonded panels per Boeing repair instructions because the original construction is prone to corrosion that can weaken structure and cause loss of cabin pressurisation. Affected aircraft are those with listed production line numbers; replacements must occur within 20 years of panel installation or within four years after 30 Dec 1999, whichever is later. Credit given for earlier approved repair revisions; inspections under the older AD are then no longer required."}},"importantCases":[],"_links":{"self":"/api/acts/ad-b727-163-lower-fuselage-skin-panels","history":"/api/acts/ad-b727-163-lower-fuselage-skin-panels/history","analysis":"/api/acts/ad-b727-163-lower-fuselage-skin-panels/analysis","conflicts":"/api/acts/ad-b727-163-lower-fuselage-skin-panels/conflicts","importantCases":"/api/acts/ad-b727-163-lower-fuselage-skin-panels/important-cases","documents":"/api/acts/ad-b727-163-lower-fuselage-skin-panels/documents"}}