{"id":"F2006B07242","name":"AD/T53/13 - Improved Centrifugal Compressor Impeller - Introduction","slug":"ad-t53-13-improved-centrifugal-compressor-impeller-introduction","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":49116,"registerId":"commonwealth-F2006B07242-current","compilationNumber":null,"startDate":"2026-04-02","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/T53/13 - Improved Centrifugal Compressor Impeller - Introduction","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)  AlliedSignal (Lycoming) Turbine Engines - T53 Series\n\n \n\nAD/T53/13 Improved Centrifugal Compressor Impeller - Introduction\n\n\n1/86\n\n \n\nApplicability: All T5313B engines. Document: 1. Lycoming SB No. 0042; or\n\n2. FAA AD 75-01-05; or\n\n \n\n3. AD/LYC-T/14. Compliance: Before 28 February 1975.\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":"Based only on the text provided, the directive applies to all T5313B engines and prescribes compliance by following one of three listed documents before 28 February 1975. There is no information in the supplied text indicating a change in scope from its original intent."},"complexity_factors":["Narrow and specific applicability: applies to a single engine model (T5313B). (Applicability)","Single fixed compliance deadline stated (28 February 1975). (Compliance)","References external technical documents as the required method of compliance (Lycoming SB No. 0042; FAA AD 75-01-05; AD/LYC-T/14), creating dependence on those documents for technical detail. (Document)","Technical subject-matter requires specialist maintenance skills and parts, increasing operational complexity despite legal simplicity. (Document)","Short text leaves implementation details to the referenced documents and to maintenance organisations, concentrating complexity in the technical guidance rather than in the directive itself. (Document)"],"plain_english_summary":"This directive mandates that every AlliedSignal (Lycoming) T5313B turbine engine be modified to the “improved centrifugal compressor impeller” standard by 28 February 1975. Owners/operators must arrange and pay for the work, which must be performed by qualified maintenance providers using one of the specified technical documents as the method of compliance. Non‑compliance risks regulatory enforcement and engines may be grounded until the modification is completed."},"kimi_summary":{"content_quality":"ok","complexity_score":2,"scope_assessment":{"changed":false,"description":"This is a discrete, single-issue safety directive focused specifically on one engine component. There is no evidence of scope creep; it addresses exactly what it purports to address — a mandatory hardware modification for safety reasons."},"complexity_factors":["Extremely short document — only 4 substantive lines of regulatory text","No defined terms section — all terms are industry-standard aviation references","Simple unconditional mandate: single applicability criterion (T5313B engines), single compliance action, single deadline","No nested exceptions or conditional logic — straightforward 'applies to all, comply by date X'","Cross-references are optional alternatives (three documents listed with 'or'), not mandatory interdependent provisions"],"plain_english_summary":"This is an **Airworthiness Directive (AD)** — a mandatory safety order issued by Australia's Civil Aviation Safety Authority (CASA). It requires owners and operators of specific aircraft engines to make a safety modification.\n\n**What it does:**\n- Mandates the installation of an improved centrifugal compressor impeller (a critical rotating component in the engine that compresses air for combustion) on all **T5313B turbine engines** made by AlliedSignal (formerly Lycoming).\n\n**Who it affects:**\n- Anyone operating, maintaining, or owning aircraft powered by T5313B engines — these are typically used in helicopters and some fixed-wing aircraft.\n\n**Why it matters:**\n- The original impeller design apparently had a safety defect. This directive forces replacement before a specific deadline (28 February 1975) to prevent potential engine failure, which could cause crashes.\n\n**Key details:**\n- **Compliance deadline:** Before 28 February 1975\n- **Technical reference:** Operators can follow Lycoming Service Bulletin No. 0042, or the equivalent US Federal Aviation Administration (FAA) directive, or an earlier Australian directive (AD/LYC-T/14)\n- **Status:** This is a historical directive from January 1986 (noted as \"1/86\"), though the compliance date of 1975 suggests it may be a republication or consolidation of earlier requirements"}},"importantCases":[],"_links":{"self":"/api/acts/ad-t53-13-improved-centrifugal-compressor-impeller-introduction","history":"/api/acts/ad-t53-13-improved-centrifugal-compressor-impeller-introduction/history","analysis":"/api/acts/ad-t53-13-improved-centrifugal-compressor-impeller-introduction/analysis","conflicts":"/api/acts/ad-t53-13-improved-centrifugal-compressor-impeller-introduction/conflicts","importantCases":"/api/acts/ad-t53-13-improved-centrifugal-compressor-impeller-introduction/important-cases","documents":"/api/acts/ad-t53-13-improved-centrifugal-compressor-impeller-introduction/documents"}}