{"id":"F2006B02653","name":"AD/B727/131 Amdt 1 - Fuselage Skin Cracking","slug":"ad-b727-131-amdt-1-fuselage-skin-cracking","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":41969,"registerId":"commonwealth-F2006B02653-current","compilationNumber":null,"startDate":"2026-04-01","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/B727/131 Amdt 1 - Fuselage Skin Cracking","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/B727/131\n\nAmdt 1\n\n  \nFuselage Skin Cracking 3/93\n\nApplicability: Boeing 727-200 series aircraft, line numbers 433 to 1832 inclusive.\n\nRequirement: Perform a detailed visual or High Frequency Eddy Current inspection for fuselage skin cracks along Stringer 1 from Body Station (BS) 1090 to BS 1110 and along the fairing attachment angle from BS 1095 to BS 1110 in accordance with Boeing Alert Service Bulletin 727-53A0204.\n\nNote: FAA AD 91-03-19 R1 refers.\n\nCompliance: Inspect before exceeding 3000 flights or 18 months, whichever occurs sooner, since the last inspection conducted in accordance with the original issue of this Directive. Repeat the inspection at intervals not to exceed 3000 flights or 18 months, whichever occurs sooner, or until one of the following preventative actions occurs:\n\n    (1) The aircraft is modified before cracks are found in accordance with Boeing Drawing 65C35757 or Paragraph C of the Accomplishment Instructions of Boeing Alert Service Bulletin 727-53A0204 Revision 2 or Revision 3; or\n\n    (2) The aircraft is repaired, if cracked, in accordance with Part III, Paragraph B or Paragraph D, of the Accomplishment Instructions of Boeing Alert Service Bulletin 727-53A0204 Revision 3.\n\nNote: Modification or repair in this manner removes the requirement for repetitive inspection, however local repair in accordance with the Boeing Structural Repair Manual does not.\n\nBackground: The original issue of this Directive referred to FAA AD 91-03-19 which specified repetitive inspection to detect cracks of the fuselage skin under the centre engine inlet pedestal housing. This action was required to avoid the possibility of rapid decompression of the cabin. This amendment revises the existing Directive to increase the allowable number of flights between inspections and to document the option of modification or repair to remove the requirement for repetitive inspections.","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"},"kimi_summary":{"content_quality":"ok","complexity_score":3,"scope_assessment":{"changed":false,"description":"This amendment stays within the original scope of addressing fuselage skin cracking in the specified aircraft. It does not expand to new aircraft types, new structural areas, or new safety issues. The changes are procedural — adjusting inspection intervals and documenting existing repair options — rather than expanding the directive's coverage."},"complexity_factors":["Multiple compliance pathways (inspection, modification, or repair) with different technical references","Cross-references to external Boeing documents (Service Bulletins, Structural Repair Manual, engineering drawings) and FAA AD 91-03-19 R1","Conditional logic: 'whichever occurs sooner' appears twice, creating calculation requirements for operators","Nested conditions in the permanent resolution options (Revision 2 or 3 of the Service Bulletin for modification; specific paragraphs for repair)","Distinction between 'local repair' (which doesn't count) and full repair (which does count) requires careful reading"],"plain_english_summary":"This CASA Airworthiness Directive requires operators of Boeing 727‑200 aircraft (line numbers 433–1832) to inspect the fuselage under the centre engine inlet for cracks using detailed visual or High Frequency Eddy Current checks. Inspections must occur every 3,000 flights or 18 months (first due by that interval) until a permanent Boeing‑approved modification or repair is installed. The rule addresses risk of rapid decompression and the amendment allows longer intervals and clearer paths to a permanent fix."},"flash_summary":{"complexity_score":5,"scope_assessment":{"changed":true,"description":"This amendment increases the allowable interval between repetitive inspections (to 3,000 flights or 18 months) and documents that completing a specified modification or repair (per Boeing Drawing 65C35757 or designated paragraphs of the Alert Service Bulletin) removes the repetitive-inspection requirement. The amendment therefore narrows operational inspection frequency while adding a permanent corrective option; the original Directive required only repetitive inspections."},"complexity_factors":["Narrow airframe applicability (Boeing 727-200, line numbers 433–1832) — increases precision but requires operators to check serial ranges.","Technical inspection methods specified (detailed visual or High Frequency Eddy Current) — requires specialised equipment or trained personnel.","Dual compliance metric (3000 flights OR 18 months, whichever sooner) — creates mixed operational and calendar tracking burdens.","Conditional removal of repetitive inspections by modification or repair tied to specific Boeing drawings and Service Bulletin revisions (Revision 2 or 3) — creates dependency on external design documents and revision control.","Explicit statement that local repairs per the Structural Repair Manual do NOT remove repetitive-inspection requirement — raises compliance nuance.","Cross-reference to FAA AD and multiple paragraphs/parts of the Boeing Service Bulletin and Drawing increases procedural cross-checking.","Requirement to repeat inspections until modification/repair or crack finding — introduces ongoing recurring compliance cost until mitigation.","Safety rationale (risk of rapid decompression) requires conservative interpretation by operators and inspectors, affecting threshold for action."],"plain_english_summary":"This airworthiness directive requires operators of Boeing 727-200s (line numbers 433–1832) to inspect for fuselage skin cracks along Stringer 1 and adjacent fairing attachment angles using detailed visual or high-frequency eddy-current methods per Boeing Alert Service Bulletin 727-53A0204. The rule sets a repeat interval of no more than 3,000 flights or 18 months and allows removal of the repetitive-inspection obligation if the aircraft is modified or repaired in accordance with the specified Boeing drawings or service bulletin. The action addresses the risk of rapid decompression under the centre engine inlet pedestal housing."}},"importantCases":[],"_links":{"self":"/api/acts/ad-b727-131-amdt-1-fuselage-skin-cracking","history":"/api/acts/ad-b727-131-amdt-1-fuselage-skin-cracking/history","analysis":"/api/acts/ad-b727-131-amdt-1-fuselage-skin-cracking/analysis","conflicts":"/api/acts/ad-b727-131-amdt-1-fuselage-skin-cracking/conflicts","importantCases":"/api/acts/ad-b727-131-amdt-1-fuselage-skin-cracking/important-cases","documents":"/api/acts/ad-b727-131-amdt-1-fuselage-skin-cracking/documents"}}