{"id":"F2006B04976","name":"AD/CESSNA 170/48 - Exhaust Muffler/Shroud","slug":"ad-cessna-170-48-exhaust-muffler-shroud","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":44866,"registerId":"commonwealth-F2006B04976-current","compilationNumber":null,"startDate":"2026-04-02","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/CESSNA 170/48 - Exhaust Muffler/Shroud","content":"COMMONWEALTH OF AUSTRALIA (Civil Aviation Regulations 1998), PART 39 \\- 105 CIVIL AVIATION SAFETY AUTHORITY\n\nSCHEDULE OF AIRWORTHINESS DIRECTIVES\n\n![](image.001.png)  \nCessna 170, 172, F172, FR172 and 175 Series Aeroplanes\n\nAD/CESSNA 170/48 Exhaust Muffler/Shroud 9/83\n\nApplicability: Model 172RG with S/Nos 172RG0001 to 172RG1134.\n\nRequirement: 1. Modify the muffler shroud in accordance with Cessna SL No SE83-13. In addition, visually inspect the flanges on the outer diameter of the ends of the muffler for cracks prior to reinstallation of the muffler shroud. Repair or replace any cracked components.\n\n    2. Visually inspect the muffler shroud for security and proper location and the flanges on the outer diameter of the ends of the muffler for cracks. Repair or replace any cracked components before further flight. Removal of the muffler shroud for this inspection is not required.\n\n    3. Reinspect any repaired components.\n\nNote: As an alternative to comply with paragraphs 1, 2 and 3 of the requirement, deactivate the cabin heat system by removing the cabin heat control cable from the control arm on the cabin heat located on the firewall at the right upper side of the engine compartment. Ensure that the valve spring mechanism is functioning and that the cabin heat valve is spring loaded to the closed position and wire locked in the closed position. FAA AD 83-14-04 Amdt 39-4684 refers.\n\nCompliance: Para 1 \\- Within 25 hours time in service after 31 August 1983.\n\nPara 2 \\- Within 50 hours time in service after the modification detailed in para 1 of the requirement has been embodied and repeated thereafter at intervals of 50 hours time in service.\n\nPara 3 \\- Within 25 hours time in service after the repair.\n\nBackground: An overseas Authority and the manufacturer, require modification and repeated inspections to the exhaust muffler/shroud assembly in order to prevent the possibility of carbon monoxide contamination. This action supersedes that taken in cancelled AD/CESSNA 170/41.","sortOrder":0}],"analysis":{"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":false,"description":"This is a discrete, targeted safety directive addressing a specific mechanical defect in a specific aircraft model. It has not expanded beyond its original purpose of preventing carbon monoxide contamination in Cessna 172RG aircraft."},"complexity_factors":["Single, narrow applicability (one specific aircraft model with defined serial number range)","Three sequential requirements with clear cross-references to manufacturer service letter","Alternative compliance method provided with specific mechanical steps","Three separate compliance timeframes (25 hours, 50 hours, 25 hours post-repair)","Minimal defined terms (relies on standard aviation terminology like 'time in service')","No nested legislative cross-references to other regulations"],"plain_english_summary":"This AD mandates owners of Cessna 172RG aircraft (S/N 172RG0001–172RG1134) modify the exhaust muffler shroud per Cessna service instructions and perform recurring inspections of the shroud and muffler flanges, with repairs required before flight. As an alternative, operators may permanently disable the cabin heating system.\n\nIt addresses risk of carbon monoxide entering the cabin from cracked exhaust components and requires timely follow-up inspections after repairs."},"flash_summary":{"complexity_score":4,"scope_assessment":{"changed":true,"description":"This AD supersedes the cancelled AD/CESSNA 170/41 and replaces that prior action with a requirement to modify the muffler shroud, perform recurring inspections and repairs, and permits an alternative of deactivating and wire-locking the cabin heat valve. The current instrument updates the mandated compliance steps and intervals for the same aircraft group."},"complexity_factors":["Targeted applicability to a specific model and serial range (Model 172RG S/Ns 172RG0001–172RG1134) limits scope but requires serial verification.","Requires modification to meet Cessna Service Letter SE83-13 (external document dependency).","Multiple, short compliance intervals: initial modification within 25 hours TIS, recurring inspections every 50 hours after modification, and reinspections within 25 hours after repair, creating frequent maintenance actions.","Inspections must check flanges for cracks and shroud security; repairs or replacements are mandatory before further flight, creating potential parts and labour costs.","Provides an operational alternative (deactivate and wire-lock cabin heat valve) that requires functional verification (valve spring) and a physical lock — introduces different compliance and inspection steps.","References FAA AD 83-14-04 and supersedes a prior AD (AD/CESSNA 170/41), adding regulatory-history complexity for operators tracking compliance changes."],"plain_english_summary":"Requires modifying the exhaust muffler shroud per Cessna Service Letter SE83-13, inspecting muffler end flanges for cracks, repairing or replacing cracked parts and reinspecting repaired items; repeated inspections are mandated. As an alternative, operators may deactivate and wire-lock the cabin heat valve after ensuring the spring returns it to closed. Applies to Cessna 172RG serials 172RG0001–172RG1134 to reduce the risk of carbon monoxide entering the cabin."}},"importantCases":[],"_links":{"self":"/api/acts/ad-cessna-170-48-exhaust-muffler-shroud","history":"/api/acts/ad-cessna-170-48-exhaust-muffler-shroud/history","analysis":"/api/acts/ad-cessna-170-48-exhaust-muffler-shroud/analysis","conflicts":"/api/acts/ad-cessna-170-48-exhaust-muffler-shroud/conflicts","importantCases":"/api/acts/ad-cessna-170-48-exhaust-muffler-shroud/important-cases","documents":"/api/acts/ad-cessna-170-48-exhaust-muffler-shroud/documents"}}