{"id":"F2006B04983","name":"AD/CESSNA 170/55 - Exhaust Heater/Muffler","slug":"ad-cessna-170-55-exhaust-heater-muffler","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":44878,"registerId":"commonwealth-F2006B04983-current","compilationNumber":null,"startDate":"2026-04-02","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/CESSNA 170/55 - Exhaust Heater/Muffler","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 - 105 CIVIL AVIATION SAFETY AUTHORITY\n\nSCHEDULE OF AIRWORTHINESS DIRECTIVES\n\n \n\n![](image.001.png)  Cessna 170, 172, F172, FR172 and 175 Series Aeroplanes\n\n \n\nAD/CESSNA 170/55 Exhaust Heater/Muffler 6/91\n\nApplicability: All Cessna 172 Series (Serial Numbers 36216 through 36769) that have not been modified with Cessna Service kit SK-172-10 or SK-172-10A.\n\n \n\nRequirement: Inspect and/or rectify subject aircraft in accordance with FAA AD90-06-03 R1.\n\n \n\nNote: FAA AD 90-06-03 R1 refers to Cessna Service Letter (SL) 170/172-11 dated 3 February 1958 and Cessna SL 170/172-13, dated 7 April 1958 contain information that pertains to this subject AD.\n\n \n\nCompliance: Within 100 hours time-in-service from 13 June 1991.\n\n \n\nBackground: FAA AD action is intended to prevent cracking of the exhaust heater/muffler that could result in dangerous carbon monoxide levels.\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":{"kimi_summary":{"content_quality":"ok","complexity_score":2,"scope_assessment":{"changed":false,"description":"This is a standard, narrow airworthiness directive targeting a specific mechanical defect in a specific aircraft model range. It has not expanded beyond its original safety purpose of addressing exhaust heater/muffler cracking."},"complexity_factors":["Very short document (under 300 words)","Only 2 defined applicability criteria (serial number range and service kit exclusions)","Single cross-reference to FAA AD90-06-03 R1 (external document)","Simple conditional logic: applies IF serial number in range AND not modified with specific kits","No nested exceptions or subsections","Clear, single compliance deadline (100 hours time-in-service)","Straightforward safety purpose with no regulatory alternatives or exemptions mentioned"],"plain_english_summary":"This CASA Airworthiness Directive requires owners/operators of Cessna 172s (S/N 36216–36769) without kits SK‑172‑10 or SK‑172‑10A to inspect and repair the exhaust heater/muffler per FAA AD90‑06‑03 R1 (which references Cessna service letters). The inspect/repair must be done within 100 flying hours from 13 June 1991 to prevent cracks that could leak carbon monoxide into the cabin."},"flash_summary":{"complexity_score":2,"scope_assessment":{"changed":false,"description":"The directive applies only to the specific serial-number range and excludes aircraft already modified with the named service kits. It mandates inspection/rectification per the referenced FAA AD and Cessna service letters within the stated 100-hour window; the text does not expand or broaden that applicability or impose additional discretionary powers."},"complexity_factors":["Narrow, serial-number limited applicability with explicit exemption for aircraft modified by SK-172-10 or SK-172-10A (single-target scope).","Single mandated action: inspect and/or rectify the exhaust heater/muffler (operationally straightforward but technical).","Cross-references needed: compliance is by following FAA AD 90-06-03 R1 and Cessna Service Letters (external documents required to implement).","Definite compliance window: within 100 hours time-in-service from a fixed date (administrative scheduling constraint).","Implementation requires qualified maintenance resources to perform inspection/repairs and maintain compliance records."],"plain_english_summary":"Requires owners/operators of Cessna 172 aeroplanes (serial numbers 36216–36769) that have not had service kit SK-172-10 or SK-172-10A fitted to inspect and, if needed, repair the exhaust heater/muffler following FAA AD 90-06-03 R1 and related Cessna service letters. Compliance is required within 100 hours time-in-service from 13 June 1991; the stated purpose is to prevent exhaust-muffler cracking that could cause dangerous carbon monoxide levels."}},"importantCases":[],"_links":{"self":"/api/acts/ad-cessna-170-55-exhaust-heater-muffler","history":"/api/acts/ad-cessna-170-55-exhaust-heater-muffler/history","analysis":"/api/acts/ad-cessna-170-55-exhaust-heater-muffler/analysis","conflicts":"/api/acts/ad-cessna-170-55-exhaust-heater-muffler/conflicts","importantCases":"/api/acts/ad-cessna-170-55-exhaust-heater-muffler/important-cases","documents":"/api/acts/ad-cessna-170-55-exhaust-heater-muffler/documents"}}