{"id":"F2006B11208","name":"AD/LYC/85 Amdt 1 - Exhaust Assembly","slug":"ad-lyc-85-amdt-1-exhaust-assembly","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":56924,"registerId":"commonwealth-F2006B11208-current","compilationNumber":null,"startDate":"2026-04-02","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/LYC/85 Amdt 1 - Exhaust Assembly","content":"COMMONWEALTH OF AUSTRALIA (Civil Aviation Regulations 1998), PART 39 \\- 106 CIVIL AVIATION SAFETY AUTHORITY\n\nSCHEDULE OF AIRWORTHINESS DIRECTIVES\n\n![](image.001.png)  \nLycoming Piston Engines\n\nAD/LYC/85\n\nAmdt 1\n\n  \nExhaust Assembly 10/96\n\nApplicability: Textron Lycoming TIO-540-S1AD engines.\n\nRequirement: To prevent cracking or distortion of the engine exhaust system flanges, V-band couplings and pipes which could result in an engine compartment fire and smoke entering the cabin, accomplish the following requirements:\n\n    a. Modify the crossover exhaust system in accordance with the requirements of Part II of Textron Lycoming Service Bulletin (SB) Number 484, and\n\nb. Install a one piece exhaust pipe and manifold retainer clamp in accordance with the requirements of Textron Lycoming SB No. 499B.\n\n    2. a. Inspect the exhaust system for heat damage, distortion, cracks or excessive wear in accordance with Textron Lycoming SB No. 484, and\n\nb. Inspect the exhaust system for clearance dimensions, proper fastener torque and slip joint engagement in accordance with Textron Lycoming SB No. 499B.\n\n    3. Repair or replace damaged parts identified during compliance with Requirement 2 of this directive.\n\nNote: FAA Airworthiness Directive 91-21-01R1 refers.\n\nCompliance: Requirement 1: Unless previously accomplished, within 25 hours time in service after 12 September 1996.\n\nRequirement 2: At intervals not to exceed 130 hours time in service, effective 12 September 1996.\n\nRequirement 3: Before further flight, effective 12 September 1996.\n\nBackground: This directive was originally issued in October 1989 to require the inspection and modification of the exhaust system crossover pipe. The requirements addressed reports of accidents, incidents and defects related to the TIO-540-S1AD exhaust system. This amendment reflects advice from the manufacturer of reports of exhaust system defects in engines complying with the original issue of this directive. This amendment adds a further modification of the exhaust system by mandating the installation of a single piece pipe and a supporting clamp and an additional inspection procedure to cover the additional modification.\n\nThe original issue of this Airworthiness Directive became effective on 4 August 1989.","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"},"flash_summary":{"complexity_score":3,"scope_assessment":{"changed":true,"description":"The amendment expands the original directive by adding a further modification requirement — installation of a single‑piece exhaust pipe and a supporting manifold retainer clamp — and adds an additional inspection procedure to cover that modification. The original directive required inspection and modification of the crossover exhaust pipe; the amendment extends required work and inspections per the Background section."},"complexity_factors":["Narrow applicability — applies only to Textron Lycoming TIO‑540‑S1AD engines (limits scope and technical footprint).","Technical mechanical work — requires specific exhaust modifications and installation of a single‑piece pipe and manifold retainer clamp (requires mechanical skill and parts).","Reliance on manufacturer service bulletins — compliance steps are specified by Textron Lycoming SB No. 484 (modification and inspection) and SB No. 499B (pipe/clamp and inspection).","Recurring inspections — mandates inspections at fixed intervals (130 hours TIS) which create ongoing maintenance scheduling and costs.","Short initial compliance window for modification if not already done (25 hours TIS after 12 Sep 1996) and immediate repair-before-flight requirement for defects, which can cause aircraft downtime.","Cross-reference to FAA AD 91-21-01R1 (additional regulatory cross‑links for implementers and maintainers)."],"plain_english_summary":"This airworthiness directive requires owners and maintenance organisations of Textron Lycoming TIO‑540‑S1AD engines to modify and inspect the exhaust assembly to prevent flange, V‑band coupling and pipe cracking or distortion that could lead to engine‑compartment fires or cabin smoke. It directs compliance with Lycoming service bulletins and mandates repair or replacement of defective parts. The Civil Aviation Safety Authority sets the compliance windows and inspection intervals, so operators bear parts, labour and downtime costs to meet the directive."},"kimi_summary":{"content_quality":"ok","complexity_score":3,"scope_assessment":{"changed":false,"description":"This amendment remains tightly focused on its original purpose — preventing exhaust system failures in the TIO-540-S1AD engine. The amendment adds an additional modification (one-piece pipe and clamp) and corresponding inspection, but this directly addresses the same safety risk (exhaust system cracking/distortion) that motivated the original 1989 directive. The scope has not expanded beyond exhaust system safety for this specific engine."},"complexity_factors":["Short, single-purpose document (1 page)","Only 3 defined requirements with clear sequential numbering","Minimal cross-referencing (only 2 manufacturer service bulletins and 1 FAA directive mentioned in passing)","Simple conditional logic (\"unless previously accomplished\", \"before further flight\")","No nested exceptions or complex definitions section","Straightforward applicability statement (single engine model)"],"plain_english_summary":"This CASA Airworthiness Directive mandates safety fixes for Textron Lycoming TIO‑540‑S1AD engines after exhaust flanges, couplings, and pipes were found to crack or distort, risking hot-gas leaks, fires, or cabin smoke. Operators of affected aircraft must fit the upgraded one‑piece crossover pipe and clamp (per manufacturer service bulletins), inspect the exhaust every 130 flight hours, and repair any defects before flight to prevent engine fires and smoke events."}},"importantCases":[],"_links":{"self":"/api/acts/ad-lyc-85-amdt-1-exhaust-assembly","history":"/api/acts/ad-lyc-85-amdt-1-exhaust-assembly/history","analysis":"/api/acts/ad-lyc-85-amdt-1-exhaust-assembly/analysis","conflicts":"/api/acts/ad-lyc-85-amdt-1-exhaust-assembly/conflicts","importantCases":"/api/acts/ad-lyc-85-amdt-1-exhaust-assembly/important-cases","documents":"/api/acts/ad-lyc-85-amdt-1-exhaust-assembly/documents"}}