{"id":"F2006B02793","name":"AD/B727/89 Amdt 4 - Cockpit Side Window - F-N Window Post","slug":"ad-b727-89-amdt-4-cockpit-side-window-f-n-window-post","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":42135,"registerId":"commonwealth-F2006B02793-current","compilationNumber":null,"startDate":"2026-04-01","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/B727/89 Amdt 4 - Cockpit Side Window - F-N Window Post","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/B727/89\n\nAmdt 4\n\n  \nCockpit Side Window \\- “F-N” Window Post 8/95\n\nApplicability: B727 line numbers 1 to 1164 inclusive.\n\nRequirement: Inspect visually, by eddy current and by X-ray as applicable, the “F-N” window post in accordance with Boeing Service Bulletin (SB) 727-53-0086, Revision 11.\n\nNote: FAA AD 93-05-17 refers.\n\nCompliance: Inspect at the thresholds and intervals specified in Tables I and II of Boeing SB 727-53-0086, Revision 11.\n\nBackground: One hundred and sixty two cracks have been experienced on 707, 727 and 737 aircraft in the subject region, including aircraft that have been modified and repaired to earlier issues of the SB. This SB has been identified by the B727 Ageing Aircraft Structures Working Group as a safety of flight item and requires the area to be modified, Directive AD/B727/118 refers.\n\nAmendment 3 extended the inspection area to the structure above the cockpit window.\n\nAmendment 4 corrects the applicability.","sortOrder":0}],"analysis":{"kimi_summary":{"content_quality":"ok","complexity_score":2,"scope_assessment":{"changed":false,"description":"This amendment makes a minor technical correction to applicability (which aircraft line numbers are covered). It does not expand the substantive safety requirements or inspection scope established in earlier amendments."},"complexity_factors":["Very short document (under 300 words)","Only 1 defined term implicitly referenced (line numbers)","No nested conditional logic — simple applicability threshold","Single compliance pathway with reference to external technical document (Boeing SB)","No cross-references to other legislation beyond noting related FAA directive and another Australian AD","Amendment history is narrative, not structural"],"plain_english_summary":"This is an **Airworthiness Directive** (a mandatory safety order) issued by Australia's Civil Aviation Safety Authority for **Boeing 727 aircraft**.\n\n**What it does:**\n- Requires airlines and aircraft operators to inspect a specific structural part of the cockpit — the \"F-N window post\" (a metal frame piece between the pilot's side windows)\n- Mandates three types of inspection: visual checks, eddy current testing (using electromagnetic fields to detect cracks), and X-ray examination\n- Operators must follow the exact procedures in **Boeing Service Bulletin 727-53-0086, Revision 11**\n\n**Who it affects:**\n- Owners and operators of Boeing 727 aircraft with **line numbers 1 through 1164** (essentially the early production models)\n- Maintenance engineers responsible for airframe inspections\n\n**Why it matters:**\n- **Safety critical:** 162 cracks have already been found in this area across Boeing 707, 727, and 737 aircraft — including planes that had previous \"fixes\" applied\n- The B727 Ageing Aircraft Structures Working Group flagged this as a \"safety of flight item,\" meaning failure could endanger the aircraft\n- This amendment (version 4) simply **corrects which aircraft serial numbers** the directive applies to — previous versions already required the inspections\n\n**Key point:** This isn't new safety work — it's a technical correction to ensure the right planes are covered by existing crack-detection requirements."},"flash_summary":{"complexity_score":5,"scope_assessment":{"changed":true,"description":"Yes. Amendment 3 extended the inspection area to structure above the cockpit window; Amendment 4 corrects the applicability to B727 line numbers 1–1164. The AD therefore broadened the inspected area in a prior amendment and then adjusted which aircraft are covered in this amendment."},"complexity_factors":["Reference to an external, revision‑specific Boeing Service Bulletin (727‑53‑0086 Rev.11) that contains the detailed inspection procedures and interval tables (Requirement; Compliance).","Multiple inspection techniques required (visual, eddy current, X‑ray), which demand specialist equipment and skills (Requirement).","Compliance is governed by thresholds and intervals contained in tables within the SB rather than fully set out in the AD, creating dependence on an external document (Compliance).","Applicability limited to a specified block of airframes (B727 line numbers 1–1164), requiring operators to verify serial/line number status (Applicability).","Interplay with other directives and documents: FAA AD 93‑05‑17 is referenced and a related modification directive is AD/B727/118 (Background), creating coordination and possible duplicate actions.","Historical amendments changed the inspected area (Amendment 3) and corrected applicability (Amendment 4), so operators must track amendment history for current obligations (Amendments).","Existence of prior repairs and modifications on affected aircraft increases inspection complexity and interpretation of acceptable findings (Background)."],"plain_english_summary":"Requires operators of Boeing 727s (line numbers 1–1164) to inspect the cockpit “F‑N” window post using visual, eddy‑current and X‑ray methods, following Boeing Service Bulletin 727‑53‑0086 Revision 11, at the thresholds and intervals set out in that bulletin. The Civil Aviation Safety Authority requires compliance; operators bear the cost of inspections, any modifications, and repairs. The directive follows multiple reported cracks and has been amended to extend the inspected area and to correct which aircraft are covered."}},"importantCases":[],"_links":{"self":"/api/acts/ad-b727-89-amdt-4-cockpit-side-window-f-n-window-post","history":"/api/acts/ad-b727-89-amdt-4-cockpit-side-window-f-n-window-post/history","analysis":"/api/acts/ad-b727-89-amdt-4-cockpit-side-window-f-n-window-post/analysis","conflicts":"/api/acts/ad-b727-89-amdt-4-cockpit-side-window-f-n-window-post/conflicts","importantCases":"/api/acts/ad-b727-89-amdt-4-cockpit-side-window-f-n-window-post/important-cases","documents":"/api/acts/ad-b727-89-amdt-4-cockpit-side-window-f-n-window-post/documents"}}