{"id":"F2006B11196","name":"AD/LYC/104 - Crankshaft Drive Gear Bolts","slug":"ad-lyc-104-crankshaft-drive-gear-bolts","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":56905,"registerId":"commonwealth-F2006B11196-current","compilationNumber":null,"startDate":"2026-04-02","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/LYC/104 - Crankshaft Drive Gear Bolts","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/104 Crankshaft Drive Gear Bolts 12/99\n\nApplicability: Textron Lycoming Model O-540-F1B5 engines as detailed by serial number in FAA Airworthiness Directive 99-03-05 and installed in, but not limited to, Robinson R44 helicopters.\n\nNote: Copies of FAA AD 99-03-05 are available from CASA. CASA contact position is the Airworthiness Directive Publishing Controller. Contact number is 131 757.\n\nRequirement: Replace crankshaft drive gear bolt part number (P/N) STD-2209. Compliance: Within 10 hours time in service from the effective date of this directive.\n\nThis Airworthiness Directive becomes effective on 2 December 1999.\n\nBackground: This directive has been issued to prevent failure of the crankshaft bolt resulting in an engine failure. The requirement follows advice of a manufacturing error in bolts supplied to the Robinson Helicopter Company.","sortOrder":0}],"analysis":{"kimi_summary":{"content_quality":"ok","complexity_score":2,"scope_assessment":{"changed":false,"description":"This is a discrete, targeted safety directive addressing a specific manufacturing defect. It has not expanded beyond its original purpose of mandating bolt replacement to prevent engine failure."},"complexity_factors":["Very short document (under 200 words)","Only 1 substantive requirement (bolt replacement)","Single defined term (P/N = part number)","No nested conditional logic or cross-references to other legislation beyond a single reference to FAA AD 99-03-05 for serial numbers","Clear, fixed compliance deadline (10 hours time in service)","Narrow applicability (specific engine model and serial numbers)"],"plain_english_summary":"**What this is:** An Airworthiness Directive (AD) — essentially a mandatory safety order for aircraft.\n\n**What it does:** Orders the replacement of a specific faulty bolt in certain Lycoming aircraft engines. The bolt in question (part number STD-2209) was manufactured incorrectly and could fail, causing complete engine failure.\n\n**Who it affects:**\n- **Aircraft owners/operators** with Textron Lycoming O-540-F1B5 engines, specifically those listed by serial number in a related US FAA directive (99-03-05)\n- **Primarily Robinson R44 helicopter operators**, though other aircraft with these engines are also covered\n\n**What must be done:**\n- Replace the faulty crankshaft drive gear bolt\n- **Deadline:** Within 10 hours of flying time after 2 December 1999\n\n**Why it matters:** A failed crankshaft bolt means engine failure, which in a helicopter is extremely dangerous. This is a reactive safety measure following discovery of a manufacturing defect in bolts supplied to Robinson Helicopter Company.\n\n**Key point:** This is not optional — compliance is legally mandatory for airworthiness certification."},"flash_summary":{"complexity_score":2,"scope_assessment":{"changed":false,"description":"The directive's scope, as stated, matches its expressed purpose: it mandates replacement of a specified crankshaft drive gear bolt on identified Lycoming O-540-F1B5 engines to prevent bolt failure following advice of a manufacturing error. The text does not expand or narrow that scope beyond the engine/model/serial-number linkage to FAA AD 99-03-05 nor introduce additional measures or exemptions. (Applicability; Requirement; Background)"},"complexity_factors":["Narrow technical scope (single part, single bolt P/N STD-2209) (Requirement)","Clear, short compliance window (10 hours time-in-service) (Compliance)","Applicability limited to specified engine model and serial numbers referenced to FAA AD 99-03-05 (Applicability; Note)","No procedural alternatives, waivers, or compliance pathways specified (Requirement; Compliance)","Dependence on an external document (FAA AD 99-03-05) for precise serial-number scope adds a minor cross-reference step (Applicability; Note)"],"plain_english_summary":"CASA mandates replacement of the crankshaft drive gear bolt (P/N STD-2209) on specified Lycoming O-540-F1B5 engines (including installations in Robinson R44s), to be done within 10 hours TIS from 2 Dec 1999.  \n\nThis affects aircraft owners/operators who must fund and schedule the mandatory replacement to prevent bolt failure after a reported manufacturing error; CASA issued the directive and points to the referenced FAA AD for engine serial-number applicability."}},"importantCases":[],"_links":{"self":"/api/acts/ad-lyc-104-crankshaft-drive-gear-bolts","history":"/api/acts/ad-lyc-104-crankshaft-drive-gear-bolts/history","analysis":"/api/acts/ad-lyc-104-crankshaft-drive-gear-bolts/analysis","conflicts":"/api/acts/ad-lyc-104-crankshaft-drive-gear-bolts/conflicts","importantCases":"/api/acts/ad-lyc-104-crankshaft-drive-gear-bolts/important-cases","documents":"/api/acts/ad-lyc-104-crankshaft-drive-gear-bolts/documents"}}