{"id":"F2006B06665","name":"AD/ROTAX/18 - Replacement of Valve Spring Retainers of Engines in Single Valve Spring Configuration","slug":"ad-rotax-18-replacement-of-valve-spring-retainers-of-engines-in-single-valve-spring-configuration","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":48623,"registerId":"commonwealth-F2006B06665-current","compilationNumber":null,"startDate":"2026-04-02","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"AIRWORTHINESS DIRECTIVE","sectionType":"part","heading":"AIRWORTHINESS DIRECTIVE","content":"# AIRWORTHINESS DIRECTIVE\n\n![](image.001.png)  \n\nFor the reasons set out in the background section, the CASA delegate whose signature appears below issues the following Airworthiness Directive (AD) under subregulation 39.1 (1) of CASR 1998. The AD requires that the action set out in the requirement section (being action that the delegate considers necessary to correct the unsafe condition) be taken in relation to the aircraft or aeronautical product mentioned in the applicability section: (a) in the circumstances mentioned in the requirement section; and (b) in accordance with the instructions set out in the requirement section; and (c) at the time mentioned in the compliance section.\n\n![](image.001.png)  \n\nRotax Piston Engines","sortOrder":0},{"sectionNumber":"AD/ROTAX/18 Replacement of Valve Spring ","sectionType":"part","heading":"AD/ROTAX/18 Replacement of Valve Spring Retainers of Engines in Single Valve Spring Configuration","content":"# AD/ROTAX/18 Replacement of Valve Spring Retainers of Engines in Single Valve Spring Configuration\n\n  \n12/2003","sortOrder":1},{"sectionNumber":"d. Engines which have had the oil system","sectionType":"part","heading":"d. Engines which have had the oil system opened during repair/maintenance:","content":"## d. Engines which have had the oil system opened during repair/maintenance:\n\nWithin the next 10 hours TIS.\n\n    e. Engines with more than 25 hours TIS (except those affected by (d)): At the next 100 hour inspection after the effective date of this Directive.","sortOrder":2},{"sectionNumber":"Rotax Piston Engines","sectionType":"part","heading":"Rotax Piston Engines","content":"## Rotax Piston Engines\n\nAD/ROTAX/18 (continued)\n\nThis Airworthiness Directive becomes effective on 27 November 2003.\n\nBackground: Due to a delay in the purging of the lubrication system during starting, it is possible that the valve spring retainers may crack due to a number of reasons outlined in the SB’s relevant to this Directive. The Austrian CAA requires replacement of the retainers with new reinforced retainers.\n\n![Signature of Jim Coyne Delegate of the Civil Aviation Safety Authority](image.002.png)  \n\nJim Coyne\n\nDelegate of the Civil Aviation Safety Authority 14 October 2003\n\n![](image.001.png)  \n\nThe above AD is notified in the Commonwealth of Australia Gazette on 5 November 2003.","sortOrder":3}],"analysis":{"flash_summary_failed":{"failed":true,"reason":"Unauthenticated. Configure AI_GATEWAY_API_KEY or use a provider module. Learn more: https://ai-sdk.dev/unauthenticated-ai-gateway","source":"analysis-cron"},"kimi_summary":{"content_quality":"ok","complexity_score":2,"scope_assessment":{"changed":false,"description":"This is a standard airworthiness directive with a narrow, specific safety purpose: addressing a known mechanical defect in a particular engine type. The scope matches the original intent of issuing urgent safety instructions for defective aviation components."},"complexity_factors":["Very short document (approximately 300 words)","Only 2 defined categories of affected engines (d and e)","Simple conditional structure: if condition X, do action Y by time Z","No cross-references to other legislation beyond basic enabling power (CASR 1998 subregulation 39.1(1))","Single technical requirement with two alternative compliance timelines","Background explanation is brief and non-technical"],"plain_english_summary":"This is a **safety order for aircraft engines**. The Civil Aviation Safety Authority (CASA) has discovered a dangerous problem with certain Rotax piston engines: the valve spring retainers (small metal parts that hold engine valves in place) can crack because oil doesn't flow properly when the engine starts.\n\n**Who it affects:**\n- Owners and operators of Rotax piston engines with a **single valve spring configuration**\n- Specifically engines that have either:\n  - Had their oil system opened for repairs (must fix within 10 hours of engine use)\n  - Been used more than 25 hours (must fix at the next regular 100-hour inspection)\n\n**What must be done:**\nThe old valve spring retainers must be replaced with new, stronger \"reinforced\" retainers.\n\n**Why it matters:**\nCracked valve spring retainers can cause engine failure, which is obviously extremely dangerous in an aircraft. This order is mandatory and became effective on 27 November 2003."},"flash_summary":{"complexity_score":4,"scope_assessment":{"changed":false,"description":"The Directive's scope remains focused on Rotax piston engines with single valve spring configuration and mandates fitting reinforced retainers per the applicability and compliance paragraphs (d) and (e). The instrument does not indicate an expansion or narrowing of that applicability beyond what is stated in the AD."},"complexity_factors":["Technical specificity: requires replacement of a particular engine component (valve spring retainers) on Rotax piston engines in single valve spring configuration.","Conditional compliance timings: two different deadlines depending on maintenance history (paragraphs (d) and (e)).","Regulatory cross-reference: issued under CASR 1998 subreg 39.1(1), invoking AD enforcement and mandatory compliance.","Dependence on external service material: background references service bulletins and Austrian CAA requirements as the rationale/source of corrective action.","Operational burden: requires coordination by owners/operators and maintenance organisations and downtime scheduling to meet TIS/inspection windows.","Effective date and notification: specific effective date (27 November 2003) and Gazette notification (5 November 2003) affect timing and legal force."],"plain_english_summary":"This Airworthiness Directive orders replacement of valve spring retainers on Rotax piston engines fitted with a single valve spring. It affects aircraft owners/operators and maintenance organisations and was issued by CASA under CASR 1998 subreg 39.1(1). The AD says delayed oil-system purging can let retainers crack, so affected engines must have reinforced retainers fitted: if the oil system was opened during repair, within the next 10 hours TIS (d); otherwise, at the next 100‑hour inspection for engines >25 hours TIS (e). Owners/operators pay for and arrange the work."}},"importantCases":[],"_links":{"self":"/api/acts/ad-rotax-18-replacement-of-valve-spring-retainers-of-engines-in-single-valve-spring-configuration","history":"/api/acts/ad-rotax-18-replacement-of-valve-spring-retainers-of-engines-in-single-valve-spring-configuration/history","analysis":"/api/acts/ad-rotax-18-replacement-of-valve-spring-retainers-of-engines-in-single-valve-spring-configuration/analysis","conflicts":"/api/acts/ad-rotax-18-replacement-of-valve-spring-retainers-of-engines-in-single-valve-spring-configuration/conflicts","importantCases":"/api/acts/ad-rotax-18-replacement-of-valve-spring-retainers-of-engines-in-single-valve-spring-configuration/important-cases","documents":"/api/acts/ad-rotax-18-replacement-of-valve-spring-retainers-of-engines-in-single-valve-spring-configuration/documents"}}