{"id":"F2009L02177","name":"AD/B737/355 - Forward Airstair Doorway Backup Intercostals and Upper Sill Web","slug":"ad-b737-355-forward-airstair-doorway-backup-intercostals-and-upper-sill-web","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":140333,"registerId":"commonwealth-F2009L02177-current","compilationNumber":null,"startDate":"2026-04-03","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"Boeing 737 Series Aeroplanes","sectionType":"division","heading":"Boeing 737 Series Aeroplanes","content":"### Boeing 737 Series Aeroplanes\n\n| AD/B737/355 | Forward Airstair Doorway BackupIntercostals and Upper Sill Web | 7/2009 |\n| ----------- | -------------------------------------------------------------- | ------ |\n\n| Applicability: | Model 737-100, -200, -200C, -300, -400 and -500 series aircraft, as identified in Boeing Alert Service Bulletin 737-53A1269, dated 17 May 2007, or later FAA approved revision.                                                                     |\n| -------------- | --------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |\n| Requirement:   | Action in accordance with the technical requirements of FAA AD 2009-09-06 Amdt 39-15892.                                                                                                                                                            |\n| Compliance:    | As specified in the Requirement document, with a revised effective date of2 July 2009.                                                                                                                                                              |\n|                | This Airworthiness Directive becomes effective on 2 July 2009.                                                                                                                                                                                      |\n| Background:    | The FAA received a report indicating that cracks were detected in the backup intercostals and upper sill web of the forward airstair doorway. Such fatigue cracking, unless detected and corrected, could result in a rapid loss of cabin pressure. |\n\n![](image.001.png)  \nDavid Villiers  \nDelegate of the Civil Aviation Safety Authority\n\n22 May 2009","sortOrder":0},{"sectionNumber":"AD/B737/355","sectionType":"part","heading":"AD/B737/355","content":"## AD/B737/355","sortOrder":1},{"sectionNumber":"Forward Airstair Doorway BackupIntercost","sectionType":"part","heading":"Forward Airstair Doorway BackupIntercostals and Upper Sill Web","content":"## Forward Airstair Doorway Backup  \nIntercostals and Upper Sill Web","sortOrder":2},{"sectionNumber":"7/2009","sectionType":"part","heading":"7/2009","content":"## 7/2009","sortOrder":3}],"analysis":{"kimi_summary":{"content_quality":"ok","complexity_score":3,"scope_assessment":{"changed":false,"description":"This is a standard, narrow airworthiness directive addressing a specific structural fatigue issue in a defined aircraft population. It has not expanded beyond its original safety purpose."},"complexity_factors":["Very short document (approximately 200 words of substantive content)","Only 1 defined term implicitly referenced (the Boeing Service Bulletin)","Single cross-reference to FAA AD 2009-09-06 (external document containing actual technical requirements)","No conditional logic or nested exceptions within the directive itself — all technical complexity is outsourced to the referenced FAA document","Simple binary applicability test (aircraft model numbers)","Straightforward compliance structure (follow the US rules)"],"plain_english_summary":"Owners/operators of Boeing 737 Classic series (‑100/‑200/‑200C/‑300/‑400/‑500) must inspect and repair fatigue cracks found at the forward airstair doorway (backup intercostals and upper sill web). Cracks could lead to rapid cabin decompression, so CASA mandates compliance with FAA AD 2009‑09‑06’s inspection and repair instructions. The AD took effect 2 July 2009."},"flash_summary_failed":{"failed":true,"reason":"A positive credit balance is required for all requests, including BYOK, so fallback providers remain available. Add credits at https://vercel.com/d?to=%2F%5Bteam%5D%2F%7E%2Fai%3Fmodal%3Dtop-up to continue.","source":"analysis-cron"},"flash_summary":{"complexity_score":4,"scope_assessment":{"changed":false,"description":"The instrument adopts the FAA AD’s technical requirements and uses Boeing’s service bulletin to identify affected aeroplanes (see Requirement and Applicability). It does not expand the technical scope beyond the referenced FAA/Boeing material; the main local change is the formal effective date set by CASA (Compliance: effective 2 July 2009)."},"complexity_factors":["Cross-reference to external FAA AD (Requirement: FAA AD 2009-09-06 Amdt 39-15892) — technical procedures are not reproduced here, so implementers must obtain and follow that document.","Dependence on Boeing Alert Service Bulletin for identifying affected aircraft (Applicability: Boeing Alert Service Bulletin 737-53A1269, dated 17 May 2007).","Narrow model applicability (Applicability: specific 737-100/200/200C/300/400/500 series) limits scope but requires fleet-by-fleet checks.","Compliance timing and formal effective date update (Compliance: revised effective date 2 July 2009) — operators must schedule work to meet the directive timeline.","Safety consequence severity (Background: detected fatigue cracking could result in rapid loss of cabin pressure) increases urgency and enforcement attention.","Operational and financial burden falls on aircraft operators — inspections and corrective actions are required but cost details not provided in this instrument (Requirement/Compliance).","Regulatory delegation and adoption model (document signed by CASA delegate) — Australian AD enforces foreign technical material domestically, creating administrative reliance on external approvals."],"plain_english_summary":"This Airworthiness Directive requires operators of certain Boeing 737-100/200/200C/300/400/500 series aeroplanes to carry out inspections and any necessary corrective action on the forward airstair doorway backup intercostals and upper sill web, following the technical requirements of FAA AD 2009-09-06 and Boeing Alert Service Bulletin 737-53A1269. \n\nCASA makes the directive effective 2 July 2009 after reports of fatigue cracking that could cause rapid cabin decompression; affected operators bear the cost and must follow the referenced FAA/Boeing procedures."}},"importantCases":[],"_links":{"self":"/api/acts/ad-b737-355-forward-airstair-doorway-backup-intercostals-and-upper-sill-web","history":"/api/acts/ad-b737-355-forward-airstair-doorway-backup-intercostals-and-upper-sill-web/history","analysis":"/api/acts/ad-b737-355-forward-airstair-doorway-backup-intercostals-and-upper-sill-web/analysis","conflicts":"/api/acts/ad-b737-355-forward-airstair-doorway-backup-intercostals-and-upper-sill-web/conflicts","importantCases":"/api/acts/ad-b737-355-forward-airstair-doorway-backup-intercostals-and-upper-sill-web/important-cases","documents":"/api/acts/ad-b737-355-forward-airstair-doorway-backup-intercostals-and-upper-sill-web/documents"}}