{"id":"F2006B11204","name":"AD/LYC/78 Amdt 5 - Thermostatic Oil Cooler Bypass Valve","slug":"ad-lyc-78-amdt-5-thermostatic-oil-cooler-bypass-valve","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"repealed","isInForce":false,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":56916,"registerId":"commonwealth-F2006B11204-current","compilationNumber":null,"startDate":"2026-04-02","status":"Repealed","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/LYC/78 Amdt 5 - Thermostatic Oil Cooler Bypass Valve","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/78\n\nAmdt 5\n\n  \nThermostatic Oil Cooler Bypass Valve 6/95\n\nApplicability: All Textron Lycoming engines fitted with thermostatic bypass valve P/N 53E19600, 75944, LW-13230 or 53E19980.\n\nRequirement: Carry out a physical inspection of the thermostatic bypass valve in accordance with the procedure detailed in Textron Lycoming Mandatory Service Bulletin No. 518B.\n\nNote: Textron Lycoming Mandatory Service Bulletin No. 518 has been amended to delete reference to a crimp nut dimension.\n\nCompliance: Effective 25 May 1995: Unless previously accomplished in accordance with a previous issue of this Directive;\n\n    Dual magneto engines; within 25 hours time in service from 25 May 1995 and thereafter at intervals not to exceed 300 hours time in service.\n\n    2. Non dual magneto engines; within 25 hours time in service after 25 May 1995 and thereafter at intervals not to exceed 600 hours time in service.\n\nBackground: This Directive requires an inspection of the oil cooler thermostatic bypass valve for security of the crimp nut on the valve shaft. This amendment reflects the release of Textron Lycoming Mandatory Service Bulletin No. 518B. The original issue of MSB 518 included a dimension check of the valve crimp nut in addition to a requirement to inspect the crimp nut for security on the shaft. Following in-service experience, the service bulletin was amended to increase the crimp nut dimension limits. A further amendment of the service bulletin now removes the dimension check entirely.","sortOrder":0}],"analysis":{"kimi_summary":{"_metrics":{"model":"kimi-k2.5","source":"moonshot-batch","completionTokens":2003},"content_quality":"ok","complexity_score":3,"scope_assessment":{"changed":false,"description":"This amendment narrows the technical requirements by removing the dimensional measurement of the crimp nut while retaining the security inspection. The scope remains focused on safety inspections of the thermostatic bypass valve and has not expanded beyond the original airworthiness safety purpose."},"complexity_factors":["Technical aviation terminology requiring knowledge of engine magneto configurations","Multiple specific part numbers in applicability section","Tiered compliance schedule with different hourly intervals for different engine categories","Reference to external technical document (Service Bulletin 518B) without reproducing full procedure","Amendment history requires understanding of what was removed from previous requirements"],"plain_english_summary":"This directive requires operators of aircraft with certain Textron Lycoming piston engines (valve P/Ns 53E19600, 75944, LW-13230, 53E19980) to inspect the thermostatic oil cooler bypass valve’s crimp nut for security per Textron Lycoming Mandatory Service Bulletin No. 518B. Initial and recurring intervals differ for dual‑magneto (first 25 flight hours after 25 May 1995, then every 300 hours) and non‑dual engines (first 25 hours, then every 600 hours). The amendment drops the previous nut‑dimension measurement and limits the check to nut security."}},"importantCases":[],"_links":{"self":"/api/acts/ad-lyc-78-amdt-5-thermostatic-oil-cooler-bypass-valve","history":"/api/acts/ad-lyc-78-amdt-5-thermostatic-oil-cooler-bypass-valve/history","analysis":"/api/acts/ad-lyc-78-amdt-5-thermostatic-oil-cooler-bypass-valve/analysis","conflicts":"/api/acts/ad-lyc-78-amdt-5-thermostatic-oil-cooler-bypass-valve/conflicts","importantCases":"/api/acts/ad-lyc-78-amdt-5-thermostatic-oil-cooler-bypass-valve/important-cases","documents":"/api/acts/ad-lyc-78-amdt-5-thermostatic-oil-cooler-bypass-valve/documents"}}