{"id":"F2006B02245","name":"AD/AL 250/27 - Compressor Bleed Valve Strainer - Installation","slug":"ad-al-250-27-compressor-bleed-valve-strainer-installation","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":41475,"registerId":"commonwealth-F2006B02245-current","compilationNumber":null,"startDate":"2026-04-01","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/AL 250/27 - Compressor Bleed Valve Strainer - Installation","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 - 106 CIVIL AVIATION SAFETY AUTHORITY\n\nSCHEDULE OF AIRWORTHINESS DIRECTIVES\n\n \n\n![](image.001.png)  Allison Turbine Engines - 250 Series\n\n \n\nAD/AL 250/27 Compressor Bleed Valve Strainer - Installation 7/77\n\nApplicability: Model 250-C20, -C20B, -B17 and B17B. Document:  1. Allison CEB 250-C20/C20B-1116; or\n\n2. Allison CEB 250-B17/B17B TP CEB 1071; or 3. FAA AD No. 77-09-08.\n\nCompliance: Within 100 hours’ time in service after 31 July 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","sortOrder":0}],"analysis":{"kimi_summary":{"content_quality":"ok","complexity_score":2,"scope_assessment":{"changed":false,"description":"This is a discrete, single-issue airworthiness directive from 1977 addressing a specific mechanical defect. It has not expanded beyond its original purpose of mandating a compressor bleed valve strainer installation for the specified engine models."},"complexity_factors":["Extremely short document (under 200 words)","Only 4 engine models specified in applicability","Simple binary compliance requirement: install strainer or don't","Single deadline with clear metric (100 hours time in service)","No defined terms section, no cross-references to other legislation beyond the three technical documents","No conditional logic, exceptions, or nested provisions","Standardised AD format following CASA template"],"plain_english_summary":"This is an **Airworthiness Directive (AD)** issued by Australia's Civil Aviation Safety Authority (CASA) that mandates a safety fix for specific Allison turbine aircraft engines.\n\n**What it does:**\nRequires owners and operators of certain Allison 250-series engines to install a **compressor bleed valve strainer** — a filter device that prevents debris from damaging the engine's bleed valve system.\n\n**Who it affects:**\n- Aircraft with **Allison 250-C20, -C20B, -B17, or -B17B** model engines\n- This typically covers various light helicopters and small fixed-wing aircraft used in Australia\n\n**What must be done:**\nOperators must follow one of three technical documents to install the strainer:\n1. Allison CEB 250-C20/C20B-1116, OR\n2. Allison CEB 250-B17/B17B TP CEB 1071, OR  \n3. FAA AD No. 77-09-08 (the equivalent US safety order)\n\n**Deadline:**\nThe work must be completed **within 100 hours of flight time** after 31 July 1977.\n\n**Why it matters:**\nAirworthiness Directives are legally binding safety orders. Without this strainer, compressor bleed valves could become contaminated or fail, potentially causing **engine power loss or failure in flight**. Compliance is mandatory — flying without completing this modification would violate civil aviation law and put lives at risk."},"flash_summary":{"complexity_score":2,"scope_assessment":{"changed":false,"description":"The excerpt sets a specific, limited requirement (installation of a compressor bleed valve strainer) for clearly listed Allison 250 engine models, with a defined compliance window and explicit references to the technical documents to be followed. There is no indication in the provided text that the scope has been broadened or narrowed relative to the instrument's own terms; therefore the scope has not changed from the instrument's stated coverage in this excerpt."},"complexity_factors":["Narrow technical scope (single installation requirement limited to specific engine models).","Short, fixed compliance window expressed in hours time-in-service (requires operator scheduling).","Primary action specified by reference to external technical documents rather than detailed steps in the AD, creating dependency on those documents.","Administrative formality within the airworthiness-directive regime (mandatory nature but no penalties/exemptions detailed in the excerpt).","Historical dating (1977) and cross-reference to FAA AD may complicate retrieval of the authoritative installation procedure."],"plain_english_summary":"This AD mandates installing a compressor bleed valve strainer on Allison 250-C20, -C20B, -B17 and -B17B turbine engines, to be done per the listed Allison service bulletins or FAA AD, within 100 hours TIS after 31 July 1977. It affects aircraft owners/operators, maintenance organisations and parts suppliers; owners bear compliance costs and must obtain and follow the referenced technical documents. The directive sets the mandatory requirement but delegates the technical/safety rationale to those referenced sources."}},"importantCases":[],"_links":{"self":"/api/acts/ad-al-250-27-compressor-bleed-valve-strainer-installation","history":"/api/acts/ad-al-250-27-compressor-bleed-valve-strainer-installation/history","analysis":"/api/acts/ad-al-250-27-compressor-bleed-valve-strainer-installation/analysis","conflicts":"/api/acts/ad-al-250-27-compressor-bleed-valve-strainer-installation/conflicts","importantCases":"/api/acts/ad-al-250-27-compressor-bleed-valve-strainer-installation/important-cases","documents":"/api/acts/ad-al-250-27-compressor-bleed-valve-strainer-installation/documents"}}