{"id":"F2006B06668","name":"AD/ROTAX/20 Amdt 1 - Exhaust Muffler Inspection","slug":"ad-rotax-20-amdt-1-exhaust-muffler-inspection","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":48636,"registerId":"commonwealth-F2006B06668-current","compilationNumber":null,"startDate":"2026-04-02","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/ROTAX/20 Amdt 1 - Exhaust Muffler Inspection","content":"![](image.001.png)\n\n![](image.001.png)  \nAIRWORTHINESS DIRECTIVE\n\nFor the reasons set out in the background section, the CASA delegate whose signature appears below revokes Airworthiness Directive (AD) AD/ROTAX/20 and issues the following 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\n\nAD/ROTAX/20\n\nAmdt 1\n\n  \nExhaust Muffler Inspection 12/2004\n\n| Applicability: | a.  | Rotax 914 F series aircraft engines with serial numbers (S/N) 4,420.373, 4,420.374, 4,420.376, and 4,420.378 up to 4,420.391 inclusive, and 4,420.393,4,420.394, 4,420.396, 4,420.397 and 4,420.399 up to 4,420.406 inclusive, withexhaust muffler part number (P/N) 979402 installed. |\n| -------------- | --- | -------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |\n|                | b.  | Rotax 914 F series engines from S/N 4,420.407 onwards with exhaust muffler P/N 979402 or P/N 979404 installed.                                                                                                                                                                         |\n|                | c.  | Exhaust muffler P/N 979402 with S/N 02.0001 up to S/N 02.0322 inclusive and S/N 03.0001 up to 03.0108 inclusive.                                                                                                                                                                       |\n|                | d.  | Exhaust muffler P/N 979404 from 03.0200 onwards.                                                                                                                                                                                                                                       |\n| Requirement:   | 1.  | Visually inspect the exhaust muffler exterior for smoke traces or cracks in accordance with Rotax mandatory Service Bulletin (SB) SB-914-028 dated March 2004 or later revision as approved by Austrian ACG or EASA.                                                                   |\n|                | 2.  | Replace any exhaust muffler that is found to have smoke traces or cracks, with an exhaust muffler that is serviceable and not affected by provisions of this directive.                                                                                                                |\n\nNote 1: Airworthiness Directive A-2004-005 R1 published by Austrian ACG and approved by EASA under reference no 2004-10151 dated 5th October 2004 refers.\n\nCompliance: 1. Unless previously accomplished, with-in 50 hours time-in-service after the effective date of this directive, and thereafter every 50 flight hours.\n\n2. Before further flight.\n\nNote 2: Installation of an exhaust muffler that is approved by the manufacturer and is not affected by the provisions of this directive is considered terminating action to the requirements of this AD.\n\nThis Amendment becomes effective on 25 November 2004.\n\nRotax Piston Engines\n\nAD/ROTAX/20 Amdt 1 (continued)\n\nBackground: The initial issue of this directive addressed the unsafe condition caused by the occurrences of cracks in the area of exhaust muffler bottom and exhaust flange. The leaking hot exhaust gases can cause fire.\n\nThis amendment addresses the same unsafe condition but with the expanded applicability list. This amendment also mandates repetitive inspection at regular intervals.\n\nThe original issue of this directive became effective on 27 November 2003.\n\n![Signature of James Coyne Delegate of the Civil Aviation Safety Authority](image.002.png)  \n\nJames Coyne\n\nDelegate of the Civil Aviation Safety Authority 14 October 2004\n\n![](image.001.png)  \n\nThe above AD is notified in the Commonwealth of Australia Gazette on 3 November 2004.","sortOrder":0}],"analysis":{"flash_summary":{"complexity_score":4,"scope_assessment":{"changed":true,"description":"Yes. The amendment expands the applicability (adds additional engine and muffler serial-number ranges and a second muffler P/N) and imposes mandatory repetitive inspections every 50 flight hours. The Background states: \"This amendment addresses the same unsafe condition but with the expanded applicability list. This amendment also mandates repetitive inspection at regular intervals.\" The original AD became effective 27 November 2003; this amendment becomes effective 25 November 2004."},"complexity_factors":["Applicability lists multiple specific engine serial-number ranges and two muffler part numbers, creating a precise but detailed scope that operators must check against their equipment (Applicability a–d).","Requirement mandates inspection per an external Rotax mandatory Service Bulletin (SB-914-028) or later revision as approved by Austrian ACG or EASA, introducing dependence on an externally maintained technical document and regulator approvals (Requirement 1; Note 1).","Repetitive compliance schedule: initial inspection within 50 hours and thereafter every 50 flight hours imposes ongoing operational burden and record-keeping (Compliance 1).","Immediate replacement obligation: any muffler with smoke traces or cracks must be replaced before further flight, creating potential near-term cash costs and downtime for operators (Requirement 2; Compliance 2).","Terminating action provided if an approved, unaffected muffler is installed, which affects long-term cost trade-offs between recurring inspections and one-off replacement (Note 2).","Authority and procedural context: AD issued under CASR 1998 subregulation 39.1(1) by a CASA delegate and references revocation of a prior AD, which matters for legal force and amendment history (header; signature block).","Amendment history and effective dates are specified (original AD effective 27 Nov 2003; this amendment effective 25 Nov 2004), so operators must track which AD version applies to their fleet (Background; effective date)."],"plain_english_summary":"This AD requires owners/operators of certain Rotax 914 F engines and specific exhaust muffler part and serial numbers to visually inspect mufflers for smoke traces or cracks, replace any defective muffler before further flight, and repeat inspections every 50 flight hours (initial within 50 hours). It addresses the risk that leaking hot exhaust gases can cause fire. Operators pay for inspections and replacements; fitting an approved unaffected muffler ends the inspection requirement."},"flash_summary_failed":{"failed":true,"reason":"A positive credit balance is required for all requests, including BYOK, so fallback providers remain available. Add credits at https://vercel.com/d?to=%2F%5Bteam%5D%2F%7E%2Fai%3Fmodal%3Dtop-up to continue.","source":"analysis-cron"},"kimi_summary":{"content_quality":"ok","complexity_score":3,"scope_assessment":{"changed":true,"description":"This Amendment 1 expands the original 2003 directive's scope significantly. The original AD addressed a specific unsafe condition but applied to a narrower range of engines. This amendment: (1) expands the applicability list to include additional serial number ranges and an additional muffler part number (P/N 979404), (2) converts a one-time inspection into a repetitive, ongoing maintenance requirement (every 50 flight hours), and (3) adds a terminating action option. The directive has evolved from a targeted safety fix to a broader ongoing airworthiness monitoring regime."},"complexity_factors":["Multiple overlapping applicability categories (a-d) with specific serial number ranges that require careful cross-referencing","References to external documents (Rotax Service Bulletin SB-914-028, Austrian ACG directive A-2004-005 R1, EASA approval)","Two-part compliance schedule: initial 50-hour window plus ongoing 50-hour repetitive intervals","Conditional logic: 'unless previously accomplished' qualifier in compliance section","Terminating action provision (Note 2) creates an exception pathway"],"plain_english_summary":"CASA mandates owners/operators of certain Rotax 914 F engines (specific serial ranges using muffler P/N 979402 or 979404) to visually inspect exhaust mufflers for cracks or smoke traces within 50 flight hours and every 50 hours thereafter. Any crack or smoke evidence requires replacement before further flight.\n\nThe AD expands covered serials and makes inspections repetitive to address fire risk from exhaust leaks; fitting an approved non‑covered muffler terminates the inspection requirement."}},"importantCases":[],"_links":{"self":"/api/acts/ad-rotax-20-amdt-1-exhaust-muffler-inspection","history":"/api/acts/ad-rotax-20-amdt-1-exhaust-muffler-inspection/history","analysis":"/api/acts/ad-rotax-20-amdt-1-exhaust-muffler-inspection/analysis","conflicts":"/api/acts/ad-rotax-20-amdt-1-exhaust-muffler-inspection/conflicts","importantCases":"/api/acts/ad-rotax-20-amdt-1-exhaust-muffler-inspection/important-cases","documents":"/api/acts/ad-rotax-20-amdt-1-exhaust-muffler-inspection/documents"}}