{"id":"F2006B02261","name":"AD/AL 250/5 Amdt 1 - Engine Compressor - Modifications","slug":"ad-al-250-5-amdt-1-engine-compressor-modifications","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":41491,"registerId":"commonwealth-F2006B02261-current","compilationNumber":null,"startDate":"2026-04-01","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/AL 250/5 Amdt 1 - Engine Compressor - Modifications","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 250/5\n\nAmdt 1\n\n\nEngine Compressor - Modifications 10/68\n\n \n\nApplicability: All 250-C18 engines.\n\n \n\nDocument: Allison CEBs No. 250 CEB-51 and -52. Compliance: Before 25 October 1968.\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 supplied text does not indicate any expansion or narrowing of the instrument's scope relative to an earlier document. As presented, the directive applies to all Allison 250-C18 engines and makes compliance with Allison CEB-51 and CEB-52 mandatory by the specified date. The text does not state prior scope or any amendment history details that would show a change in scope."},"complexity_factors":["Very short, narrowly targeted instrument (applies only to Allison 250-C18 engines).","Prescriptive single-action requirement with a single fixed deadline (before 25 October 1968).","Dependency on external technical documents (Allison CEB-51 and CEB-52) for implementation detail increases practical complexity for maintainers.","Lack of explanatory material in the supplied text (no stated reasons, no transitional arrangements or alternatives) creates ambiguity about intent and practical options.","Regulatory context is clear (airworthiness directive under CASA), so legal placement is simple."],"plain_english_summary":"What this instrument does (mechanics)\n\n- This airworthiness directive (AD/AL 250/5 Amdt 1) requires specific compressor modifications for Allison 250-C18 engines. (See: \"Applicability: All 250-C18 engines\"; \"Document: Allison CEBs No. 250 CEB-51 and -52.\"; \"Compliance: Before 25 October 1968.\")\n- The directive makes compliance with the technical instructions in Allison CEB-51 and CEB-52 mandatory for every 250-C18 engine, and sets a final compliance date (before 25 October 1968).\n\nWho it affects\n\n- Legally responsible parties for affected engines: owners and operators of aircraft fitted with Allison 250-C18 engines, and the maintenance organisations who carry out the work. (See: \"Applicability: All 250-C18 engines.\" and the referenced Allison CEBs.)\n\nWhy it matters (what it changes in practice)\n\n- The AD converts the technical instructions in manufacturer bulletins (Allison CEB-51 and CEB-52) into a mandatory regulatory requirement that must be carried out by the compliance date. That changes the status of those bulletins from guidance to a required action for the specified engines. (See: \"Document: Allison CEBs No. 250 CEB-51 and -52.\" and \"Compliance: Before 25 October 1968.\")\n\nSource-stated rationale\n\n- The supplied text does not state an explicit reason or set out the safety issue that prompted the directive. The instrument text itself only sets applicability, references the manufacturer bulletins, and fixes a compliance date.\n\nCosts, incentives, trade-offs and implementation issues (source-grounded analysis)\n\n- Who pays: The directive places the obligation to comply on parties responsible for the engines (owners/operators/maintainers). The text does not allocate funding or subsidies; therefore costs of parts, labour, and aircraft downtime are the responsibility of those parties. (See: \"Applicability\" and \"Document\"/\"Compliance\" entries.)\n- Decision authority: The AD is issued under the Civil Aviation Safety Authority schedule of airworthiness directives (header: \"PART 39 - 106 CIVIL AVIATION SAFETY AUTHORITY / SCHEDULE OF AIRWORTHINESS DIRECTIVES\"), and it references manufacturer CEBs for technical detail. This splits legal command (the AD) from the technical instructions (the CEBs). (See header and \"Document\".)\n- Compliance burden and timing risk: The AD imposes a fixed deadline (before 25 October 1968). Meeting a fixed, near-term deadline can create demand for parts/slots in maintenance facilities and may require scheduling downtime; the text does not provide transitional arrangements or extensions. (See: \"Compliance: Before 25 October 1968.\")\n- Implementation detail and discretion: The AD does not reproduce the technical work required; instead it references manufacturer bulletins (CEB-51 and -52). Implementers must consult those documents to know what specific modifications to perform. The AD therefore delegates technical detail to external documents, increasing the need to consult and interpret those bulletins. (See: \"Document: Allison CEBs No. 250 CEB-51 and -52.\")\n- Effects on private choice and operational behaviour: By making the manufacturer bulletins mandatory, the AD removes the option to defer or refuse the specified modifications for the covered engines; operators must either carry out the modification by the deadline or face the regulatory consequences set out under airworthiness rules. The text does not list permitted alternatives (e.g., placarding, operational limitations, or engine replacement), so those options are not addressed in the supplied text. (See: applicability/document/compliance entries.)\n\nTrade-offs and opportunity costs\n\n- The directive trades the owner's short-term costs (parts, labour, downtime) against whatever benefit the AD is intended to secure; the supplied text does not state that benefit explicitly. Because the AD imposes a mandatory action, owners cannot reallocate the same maintenance budget to other work for the affected engines without foregoing compliance. (See: \"Applicability\" and \"Compliance.\")\n\nConcentrated benefits, diffuse costs, capture risk\n\n- The supplied text does not identify beneficiaries or provide evidence about distributional effects. The directive concentrates the obligation on owners/operators of 250-C18 engines (a concentrated set of parties); any benefits that motivated the directive are not described in the text. The text does not address issues such as financial assistance, alternatives, or dispute resolution mechanisms.\n\nNet description\n\n- Mechanically, this is a narrow, prescriptive, time-limited mandatory modification requirement: it applies to all Allison 250-C18 engines, requires compliance with Allison CEB-51 and CEB-52, and sets a deadline of before 25 October 1968. The technical content and practical steps are contained in the referenced CEBs, which implementers must consult to comply. (See: whole directive: \"Applicability\", \"Document\", \"Compliance\".)"},"kimi_summary":{"content_quality":"ok","complexity_score":2,"scope_assessment":{"changed":false,"description":"This is a discrete, single-issue airworthiness directive focused solely on compressor modifications for one specific engine model. It has not expanded beyond its original narrow safety purpose."},"complexity_factors":["Extremely short document (approximately 100 words of substantive content)","No defined terms section — all terms are standard aviation industry terminology","No cross-references to other legislation or regulations beyond the parent Civil Aviation Regulations 1998","Simple conditional structure: single applicability criterion (engine model) and single compliance requirement (date)","No exceptions, exemptions, or nested conditions","Straightforward command structure: identifies problem engine, cites technical documents, sets deadline"],"plain_english_summary":"This is an **Airworthiness Directive (AD)** issued by Australia's Civil Aviation Safety Authority (CASA) that mandates specific safety modifications to a particular aircraft engine.\n\n**What it does:**\n- Requires owners and operators of **Allison 250-C18 turbine engines** to carry out modifications to the **engine compressor**.\n- The modifications must follow technical instructions found in **Allison Commercial Engine Bulletins (CEBs) numbered 250 CEB-51 and CEB-52**.\n\n**Who it affects:**\n- Anyone who owns, operates, or maintains aircraft powered by **Allison 250-C18 engines** (these are commonly used in helicopters and light aircraft).\n\n**Why it matters:**\n- Airworthiness Directives are legally binding safety orders. They are issued when an unsafe condition is found in an aircraft, engine, or propeller. Compliance is **mandatory** — you cannot legally fly the affected aircraft until the work is done.\n- This particular directive had a **hard deadline of 25 October 1968**, meaning all affected engines had to be modified before that date to remain airworthy.\n\n**Key point:** This is a historical directive from 1968. While it shows the regulatory framework for aviation safety, the compliance date has long passed."}},"importantCases":[],"_links":{"self":"/api/acts/ad-al-250-5-amdt-1-engine-compressor-modifications","history":"/api/acts/ad-al-250-5-amdt-1-engine-compressor-modifications/history","analysis":"/api/acts/ad-al-250-5-amdt-1-engine-compressor-modifications/analysis","conflicts":"/api/acts/ad-al-250-5-amdt-1-engine-compressor-modifications/conflicts","importantCases":"/api/acts/ad-al-250-5-amdt-1-engine-compressor-modifications/important-cases","documents":"/api/acts/ad-al-250-5-amdt-1-engine-compressor-modifications/documents"}}