{"id":"F2006B09741","name":"AD/F27/86 - Propeller Feathering Circuit - Duplicated Manual Feathering System","slug":"ad-f27-86-propeller-feathering-circuit-duplicated-manual-feathering-system","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":115941,"registerId":"commonwealth-F2006B09741-current","compilationNumber":null,"startDate":"2026-04-03","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/F27/86 - Propeller Feathering Circuit - Duplicated Manual Feathering System","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/F27/86 Propeller Feathering Circuit - Duplicated\n\nManual Feathering System\n\n\n4/76\n\n \n\nApplicability: All models. Document: Fokker SB 61-26.\n\nCompliance: Before 30 September 1977.\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\n \n\n \n","sortOrder":0}],"analysis":{"kimi_summary":{"content_quality":"ok","complexity_score":2,"scope_assessment":{"changed":false,"description":"This is a discrete, time-bound safety directive from 1976 with a specific technical purpose (propeller feathering modification). It has not expanded beyond its original scope."},"complexity_factors":["Very short document (approximately 100 words of substantive content)","No defined terms section — uses plain technical language","Single compliance requirement with clear deadline","No cross-references to other legislation beyond the parent Civil Aviation Regulations 1998","No conditional logic or exceptions — applies to 'All models' unconditionally","References only one external technical document (Fokker SB 61-26) for implementation details"],"plain_english_summary":"This is an **Airworthiness Directive (AD)** — essentially a mandatory safety order issued by Australia's Civil Aviation Safety Authority (CASA) for aircraft.\n\n**What it does:**\nRequires owners and operators of **Fokker F27 series aircraft** to modify the propeller feathering circuit by installing a **duplicated manual feathering system**.\n\n**Why this matters:**\n\"Feathering\" a propeller means turning the blades so they cut through the air with minimal resistance — critical if an engine fails in flight. Without a working feathering system, a failed engine's propeller creates drag, making the aircraft harder to control and potentially dangerous. This directive adds a backup (duplicated) manual system so pilots can still feather the propeller even if the automatic or primary system fails.\n\n**Who it affects:**\nAnyone operating Fokker F27 aircraft in Australia — airlines, charter operators, or private owners.\n\n**What they must do:**\nFollow the technical instructions in **Fokker Service Bulletin 61-26** and complete the modification **before 30 September 1977**."},"flash_summary":{"complexity_score":2,"scope_assessment":{"changed":false,"description":"The supplied text presents a clear, narrow scope: require the duplicated manual feathering system modification on all Fokker F27 models via Fokker SB 61-26, with a fixed compliance date. There is no indication within the supplied document that the scope was altered from its original formulation; the applicability, technical reference, and deadline are stated directly in the text (Applicability; Document; Compliance)."},"complexity_factors":["Single, specific technical requirement (duplication of manual feathering system) stated in the title","Applies uniformly to all Fokker F27 models (Applicability: All models) — no model-specific carve-outs","Relies on an external technical document (Fokker SB 61-26) for implementation details (Document: Fokker SB 61-26)","Fixed compliance deadline creates scheduling pressure but does not add layered procedural requirements (Compliance: Before 30 September 1977)","The supplied text contains no conditional exemptions, certification steps, or enforcement provisions, keeping the directive’s text short but shifting complexity into the external service bulletin"],"plain_english_summary":"AD/F27/86 requires all Fokker F27 aircraft to have a duplicated manual propeller-feathering system installed in accordance with Fokker Service Bulletin SB 61‑26, completed before 30 September 1977.\n\nOwners/operators must arrange and fund the modification, scheduling parts, labour and downtime; the directive relies on the SB for technical detail and imposes a firm regulatory deadline."}},"importantCases":[],"_links":{"self":"/api/acts/ad-f27-86-propeller-feathering-circuit-duplicated-manual-feathering-system","history":"/api/acts/ad-f27-86-propeller-feathering-circuit-duplicated-manual-feathering-system/history","analysis":"/api/acts/ad-f27-86-propeller-feathering-circuit-duplicated-manual-feathering-system/analysis","conflicts":"/api/acts/ad-f27-86-propeller-feathering-circuit-duplicated-manual-feathering-system/conflicts","importantCases":"/api/acts/ad-f27-86-propeller-feathering-circuit-duplicated-manual-feathering-system/important-cases","documents":"/api/acts/ad-f27-86-propeller-feathering-circuit-duplicated-manual-feathering-system/documents"}}