{"id":"F2006B09671","name":"AD/F27/101 - Cowlings - Gearbox Access Door - Modification","slug":"ad-f27-101-cowlings-gearbox-access-door-modification","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":115806,"registerId":"commonwealth-F2006B09671-current","compilationNumber":null,"startDate":"2026-04-03","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/F27/101 - Cowlings - Gearbox Access Door - Modification","content":"---\nmeta-content-style-type: text/css\nmeta-content-type: application/xhtml+xml; charset=utf-8\nmeta-generator: Aspose.Words for .NET 22.10.0\n---\n\n?xml version=\"1.0\" encoding=\"utf-8\" standalone=\"no\"?>\n\nCOMMONWEALTH OF AUSTRALIA (Civil Aviation Regulations 1998), PART 39 - 105 CIVIL AVIATION SAFETY AUTHORITY\n\nSCHEDULE OF AIRWORTHINESS DIRECTIVES\n\n \n\n![](image.001.png)  Fokker F27 Series Aeroplanes\n\n \n\nAD/F27/101 Cowlings - Gearbox Access Door - Modification 11/80\n\nApplicability: All model F27 with S/Nos. as detailed in Fokker F27 SB No. F27/71-27. Document: Fokker F27 SB No. F27/71-27.\n\nCompliance: Before 1 June 1981.\n\n \n\nBackground: SB No. F27/71-27 introduces a modification designed to prevent departure of the aeroplane with an unlocked gearbox access door.\n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n","sortOrder":0}],"analysis":{"flash_summary":{"complexity_score":2,"scope_assessment":{"changed":false,"description":"The AD implements the modification described in Fokker F27 SB No. F27/71-27 for the aeroplanes identified by serial number and mandates completion by a fixed date (Applicability; Document; Compliance). The directive enforces the service bulletin’s intended safety change (to prevent departure with an unlocked gearbox access door) rather than expanding or narrowing that technical scope; it does not add additional aircraft or different requirements beyond those referenced in the SB (Background; Document)."},"complexity_factors":["Narrow applicability limited to F27 serial numbers listed in the referenced service bulletin (Applicability; Document).","Clear and short compliance deadline with a single mandated action (Compliance).","Technical instructions are not contained in the AD but in an external service bulletin, requiring operators to obtain and follow that document (Document) — this adds a procedural dependency but not regulatory complexity.","No alternative methods of compliance, exemptions, or discretionary criteria are specified in the AD text, reducing interpretive complexity.","Regulatory authority and enforcement are clear (Civil Aviation Safety Authority / Part 39 header), so legal responsibility is not ambiguous."],"plain_english_summary":"This airworthiness directive requires the modification in Fokker Service Bulletin F27/71-27 be fitted to the Fokker F27 aeroplanes listed by serial number by 1 June 1981 to prevent departure with an unlocked gearbox access door. It affects aircraft owners/operators and maintenance organisations; compliance is mandatory and costs (parts, labour, downtime) fall to operators."},"kimi_summary":{"content_quality":"ok","complexity_score":2,"scope_assessment":{"changed":false,"description":"This is a discrete, single-issue airworthiness directive from 1980 with a narrow, specific scope (gearbox access door modification for one aircraft type). No evidence of scope creep."},"complexity_factors":["Very short document (approximately 150 words)","Only 2 defined references (Service Bulletin F27/71-27 and serial numbers)","Single, unambiguous compliance requirement with clear deadline","No nested conditions, exceptions, or cross-references to other legislation","Straightforward applicability criteria (specific aircraft models/serial numbers)"],"plain_english_summary":"This is an **Airworthiness Directive (AD)** issued by Australia's Civil Aviation Safety Authority (CASA) for **Fokker F27 aircraft**.\n\n**What it does:**\n- Requires owners/operators of specific Fokker F27 aeroplanes to install a modification to the **gearbox access door** (a maintenance hatch on the engine/gearbox area).\n- The modification prevents the aircraft from taking off if this door is not properly locked.\n\n**Who it affects:**\n- Operators of Fokker F27 aircraft with specific serial numbers listed in **Fokker Service Bulletin F27/71-27**.\n\n**Why it matters:**\n- **Safety issue:** An unlocked gearbox access door could open during flight, potentially causing damage or dangerous conditions.\n- **Mandatory compliance:** Aircraft owners must complete this modification **before 1 June 1981**.\n\n**Key terms:**\n- **Airworthiness Directive (AD):** A legally enforceable safety order requiring aircraft modifications or inspections.\n- **Service Bulletin (SB):** Technical instructions from the aircraft manufacturer describing how to make the modification."}},"importantCases":[],"_links":{"self":"/api/acts/ad-f27-101-cowlings-gearbox-access-door-modification","history":"/api/acts/ad-f27-101-cowlings-gearbox-access-door-modification/history","analysis":"/api/acts/ad-f27-101-cowlings-gearbox-access-door-modification/analysis","conflicts":"/api/acts/ad-f27-101-cowlings-gearbox-access-door-modification/conflicts","importantCases":"/api/acts/ad-f27-101-cowlings-gearbox-access-door-modification/important-cases","documents":"/api/acts/ad-f27-101-cowlings-gearbox-access-door-modification/documents"}}