{"id":"F2006B11207","name":"AD/LYC/83 - Crankshaft Flange","slug":"ad-lyc-83-crankshaft-flange","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":56922,"registerId":"commonwealth-F2006B11207-current","compilationNumber":null,"startDate":"2026-04-02","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/LYC/83 - Crankshaft Flange","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/83 Crankshaft Flange 11/88\n\nApplicability: All AEIO-540-D series, IO-540 (250 & 260 horsepower) engines converted for aerobatic flight or any other 540 engines employing a 2-3/8 diameter main bearing seal used in unlimited category aerobatic manoeuvres.\n\nRequirement: Visually inspect the crankshaft flange in accordance with Lycoming Service Bulletin No 482.\n\nCompliance: For those engines which have been subjected to unlimited category manoeuvres - initially within 100 hours of engine operation after 3 November 1988 and thereafter at intervals not exceeding each 10 hours of aerobatic flight involving unlimited category manoeuvres.\n\nBackground: Lycoming SB 482 advises that cracked crankshafts have occurred on applicable engines which have been submitted to unlimited category aerobatic manoeuvres. These manoeuvres are more severe than contemplated when the engines were certificated for prolonged inverted flight and for normal aerobatic manoeuvres. Unlimited category manoeuvres such as multiple snap rolls, inverted flat spins, lomcevaks etc. produce severe bending loads on the propeller flange area. Exceeding engine maximum rated speed and/or using the aircraft in manoeuvres which produce rapid angular propeller centreline acceleration may result in crankshaft failure.","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":false,"description":"The directive's scope remains limited to the engine types and operational use set out in the Applicability: Lycoming AEIO‑540/IO‑540 (250 & 260 hp) engines converted for aerobatic flight or 540 engines using the specified main bearing seal when subjected to unlimited category manoeuvres. The instrument does not broaden coverage to other engine types or non‑aerobatic operations."},"complexity_factors":["Narrow technical applicability to specific engine models and conversions (Applicability).","Dependence on an external document for the inspection procedure: Lycoming Service Bulletin No. 482 (Requirement).","Short, recurring inspection interval tied to flight activity (every 10 hours of unlimited aerobatic flight) increasing operational and recordkeeping burden (Compliance).","Operational judgment required to determine when an engine has been subjected to 'unlimited category manoeuvres' despite examples in the Background, creating interpretive scope (Background).","Safety‑critical component (crankshaft flange) raises enforcement and consequence stakes, though the AD itself prescribes only inspection rather than mandatory replacement (Requirement/Background)."],"plain_english_summary":"**Requires operators and owners of specified Lycoming 540‑series engines used in \"unlimited\" aerobatic manoeuvres (or engines converted for aerobatics) to visually inspect the crankshaft flange in accordance with Lycoming Service Bulletin No. 482. (Requirement)**\n\nInspections must occur initially within 100 hours of operation after 3 November 1988 for engines already used in unlimited manoeuvres and thereafter at intervals not exceeding every 10 hours of unlimited aerobatic flight. Costs and recordkeeping fall to the aircraft owner/operator; compliance imposes frequent inspections and maintenance actions. (Compliance)"},"kimi_summary":{"content_quality":"ok","complexity_score":2,"scope_assessment":{"changed":false,"description":"This is a discrete, targeted safety directive addressing a specific mechanical failure mode in specific engines under specific operating conditions. It has not expanded beyond its original purpose of preventing crankshaft failures in high-stress aerobatic operations."},"complexity_factors":["Single, specific mechanical requirement (visual inspection)","Only 3 defined applicability criteria (engine series, horsepower, bearing seal size)","Simple two-tier compliance schedule (initial 100-hour check, then 10-hour intervals)","No cross-references to other legislation beyond the parent Civil Aviation Regulations 1998","No conditional exceptions or nested logic","Background section provides clear rationale without adding legal complexity","Total length: approximately 200 words"],"plain_english_summary":"This AD mandates mandatory inspections of the crankshaft flange on certain Lycoming 540-series piston engines (including AEIO-540-D and IO-540 aerobatic-modified models) used in unlimited-category aerobatics. Operators must follow Lycoming Service Bulletin No. 482 to detect cracks early.\n\nIt targets owners/operators performing extreme manoeuvres that impose high crankshaft loads, addressing real-world failures that could lead to propeller separation and catastrophic in-flight loss of power."}},"importantCases":[],"_links":{"self":"/api/acts/ad-lyc-83-crankshaft-flange","history":"/api/acts/ad-lyc-83-crankshaft-flange/history","analysis":"/api/acts/ad-lyc-83-crankshaft-flange/analysis","conflicts":"/api/acts/ad-lyc-83-crankshaft-flange/conflicts","importantCases":"/api/acts/ad-lyc-83-crankshaft-flange/important-cases","documents":"/api/acts/ad-lyc-83-crankshaft-flange/documents"}}