{"id":"F2006B11209","name":"AD/LYC/86 Amdt 2 - Propeller Governor Oil Line","slug":"ad-lyc-86-amdt-2-propeller-governor-oil-line","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":56925,"registerId":"commonwealth-F2006B11209-current","compilationNumber":null,"startDate":"2026-04-02","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/LYC/86 Amdt 2 - Propeller Governor Oil Line","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/86\n\nAmdt 2\n\n  \nPropeller Governor Oil Line 11/98\n\nApplicability: All Lycoming four cylinder engines with a rear mounted propeller governor and external oil line.\n\nRequirement: 1. Rigid Oil Line Installation:\n\n    Inspect the propeller governor external oil line for evidence of leaks, cracks, abrasion and correct fitment of support clamps. Replace as necessary.\n\n    b. Replace the propeller governor external oil line, if fitted with aluminium attachment nuts, with an oil line having P/N AN818-6 steel attachment nuts.\n\n    c. Replace aluminium propeller governor oil line elbow P/N MS20822-6D with a steel elbow P/N MS20822-6.\n\n2. Flexible Oil Line Installation. If a flexible governor oil hose is fitted, inspect the hose and ascertain the specification of the hose. If not of TSO C53a - Type D specification, replace with correct hose in accordance with Lycoming Service Instruction No.1435, Supplement 1.\n\nNote: FAA AD 90-04-06 and Lycoming SB 488A refer.\n\nCompliance: Unless previously accomplished:\n\n    Engines in service: Within 25 hours in service. Uninstalled engines: Prior to installation in an aircraft.\n    Engines in service: Within 25 hours time in service. Uninstalled engines: Prior to installation in an aircraft.\n\nThis amendment becomes effective on 8 October 1998.\n\nBackground: Several applicable Lycoming engine installations in Australia have been found with TSO C53a -Type C flexible governor lines fitted and there have been a number of premature failures of these lines. This directive has been amended to include inspection for fitment of the correct specification flexible hoses installed as an alternate to rigid lines and the removal of those flexible hoses which do not meet the manufacturer’s installation requirements. The operating parameters of the installation is such that Lycoming has determined that TSO C53a-Type C hoses are not an acceptable substitute for rigid lines and that only TSO C53a-Type D hoses will suffice.\n\nThis Directive allows the use of only flexible oil lines which are approved as a replacement for rigid oil lines. All other aspects of the directive remain as per Amendment 1.\n\nCOMMONWEALTH OF AUSTRALIA (Civil Aviation Regulations 1998), PART 39 \\- 106 CIVIL AVIATION SAFETY AUTHORITY\n\nSCHEDULE OF AIRWORTHINESS DIRECTIVES\n\nAmendment 1 of this airworthiness directive became effective on 4 October 1990. The original issue of this airworthiness directive became effective on 12 July 1990.","sortOrder":0}],"analysis":{"flash_summary":{"complexity_score":3,"scope_assessment":{"changed":true,"description":"This amendment expanded the AD's scope beyond the earlier rigid‑line focus by explicitly adding inspection and specification requirements for flexible governor oil hoses. It requires identification of the hose TSO specification and prohibits TSO C53a‑Type C hoses in these installations, permitting only TSO C53a‑Type D hoses as an acceptable flexible alternative; it also mandates replacement of certain aluminium fittings with specified steel parts. Those additions increase the universe of affected components and the types of maintenance actions required (hose specification checks and possible replacements), and so broaden the directive's practical scope compared with the original issue."},"complexity_factors":["Short, single-subject airworthiness directive (AD) focused on propeller governor oil line","Limited number of prescriptive items (3 rigid-line actions; 1 flexible-line action)","Technical specificity via part numbers (AN818-6, MS20822-6) and TSO designations (TSO C53a Type C vs Type D)","Cross-references to external documents (FAA AD 90-04-06, Lycoming SB 488A, Lycoming Service Instruction No.1435, Supplement 1)","Two compliance paths (engines in service vs uninstalled engines) with identical 25‑hour/installation deadlines","Amendment history and background text adds context but not legal complexity (amendment 1 and amendment 2 noted)"],"plain_english_summary":"**What this directive does (mechanically):**\n\n- **Inspects and fixes the propeller governor oil line** on certain Lycoming four‑cylinder piston engines with a rear‑mounted propeller governor and an external oil line. (Applicability)\n- For engines with a **rigid oil line** the directive requires:\n  - Inspect the external oil line for leaks, cracks, abrasion and correct clamp fitment; replace parts as needed (Requirement 1.a).\n  - Replace aluminium attachment nuts on the oil line with steel nuts, part number AN818-6 (Requirement 1.b).\n  - Replace an aluminium elbow, P/N MS20822-6D, with the steel elbow P/N MS20822-6 (Requirement 1.c).\n- For engines with a **flexible governor oil hose** the directive requires:\n  - Inspect the hose to identify its Technical Standard Order (TSO) specification (Requirement 2).\n  - If the hose is not to **TSO C53a - Type D**, replace it with a hose that meets that Type D specification, following Lycoming Service Instruction No.1435, Supplement 1 (Requirement 2).\n- The directive cross‑references FAA AD 90‑04‑06 and Lycoming Service Bulletin 488A as related documents.\n\n**Who is affected:**\n\n- Owners and operators of aircraft powered by Lycoming four‑cylinder engines that have a rear mounted propeller governor and an external oil line. That includes aircraft maintenance organisations (AMOs) and individual mechanics who maintain these engines.\n\n**When it must be done:**\n\n- For engines already in service: the inspections/replacements must be completed within 25 hours time in service unless they were already done.\n- For engines not installed in an aircraft: the inspections/replacements must be completed before installation.\n\n**Why the directive was issued (stated purpose):**\n\n- The background explains that some installations in Australia were found fitted with TSO C53a‑Type C flexible governor hoses and that there have been premature failures of those hoses. Lycoming examined the operating parameters and concluded Type C hoses are not an acceptable substitute for rigid lines; only TSO C53a‑Type D flexible hoses are acceptable alternatives. The amendment therefore added checks for flexible hose specification and mandated removal of incorrect flexible hoses.\n\n**Practical effects, implementation mechanics and trade‑offs:**\n\n- Who pays: aircraft owners/operators (or their maintenance providers) pay for inspections and any required replacements (steel nuts/elbows or Type D hoses).\n- Who decides/acts: licensed maintenance personnel or AMOs perform the inspections and replacements; owners decide when to schedule the work subject to the 25‑hour compliance window.\n- Compliance burden and operational disruption: the 25‑hour window is short and may force quick scheduling of maintenance downtime and procurement of specified steel fittings or TSO‑D hoses.\n- Technical specificity reduces substitution options: the directive prescribes particular part numbers for steel nuts and elbows and requires hoses meeting a specific TSO class, limiting the use of alternative fittings or hoses unless they are shown to meet the stated specification and Lycoming’s installation instructions.\n- Effects on maintenance suppliers and parts market: demand rises for the specified steel fittings and for TSO C53a‑Type D hoses; suppliers of aluminium fittings or Type C hoses will see reduced demand for these uses in the affected installations.\n- Safety rationale vs cost: the directive is presented as a safety response to observed premature failures of Type C flexible hoses. The immediate cost is parts and labour; the directive prioritises replacing fittings/hose types judged by the manufacturer and regulator to be unsafe in these installations.\n\n**Implementation risks and possible ambiguities:**\n\n- Correctly identifying TSO hose types and the exact elbow/nut part numbers requires technical familiarity and reference to Lycoming Service Instruction No.1435, Supplement 1. Misidentification could lead to non‑compliance or inappropriate replacement parts being fitted.\n- The directive relies on the manufacturer's (Lycoming's) determination that Type C hoses are unsuitable; the directive enforces that technical judgment by requiring Type D hoses or steel fittings.\n\n**Reference to text:**\n- The requirements are set out under \"Requirement\" (items 1 and 2) and the compliance timing under \"Compliance\". The background explains the reasoning and the amendment change to include flexible hose specification checks.\n\n"},"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":true,"description":"The original 1990 directive only addressed rigid aluminium oil lines and their replacement with steel components. Amendment 2 (1998) significantly expanded scope to also cover flexible oil line installations, adding inspection requirements for TSO C53a-Type D specification hoses and banning Type C hoses. This transformed the directive from a metal-parts replacement order into a comprehensive oil line safety mandate covering both rigid and flexible configurations."},"complexity_factors":["Short, single-purpose directive with clear mechanical requirements","Only 2 defined technical specifications (TSO C53a-Type C and Type D, plus part numbers)","Simple conditional structure: rigid line path OR flexible line path","Minimal cross-referencing (only to FAA AD 90-04-06, Lycoming SB 488A, and Service Instruction 1435)","Straightforward compliance deadlines with no nested exceptions","Some technical aviation terminology (TSO, propeller governor, time in service) requires domain knowledge but is standard for the industry"],"plain_english_summary":"This Airworthiness Directive orders operators and maintainers of Lycoming four‑cylinder piston engines with rear‑mounted propeller governors to inspect and, where required, replace external oil lines and fittings—upgrading aluminium nuts/elbows to steel and ensuring flexible hoses meet TSO C53a‑Type D. It applies to engines in service (compliance within 25 flight hours) and engines before installation. The aim is to prevent oil‑line failures that can cause loss of propeller control or engine failure."}},"importantCases":[],"_links":{"self":"/api/acts/ad-lyc-86-amdt-2-propeller-governor-oil-line","history":"/api/acts/ad-lyc-86-amdt-2-propeller-governor-oil-line/history","analysis":"/api/acts/ad-lyc-86-amdt-2-propeller-governor-oil-line/analysis","conflicts":"/api/acts/ad-lyc-86-amdt-2-propeller-governor-oil-line/conflicts","importantCases":"/api/acts/ad-lyc-86-amdt-2-propeller-governor-oil-line/important-cases","documents":"/api/acts/ad-lyc-86-amdt-2-propeller-governor-oil-line/documents"}}