{"id":"F2006B10053","name":"AD/G159/1 - Flap Drive Control Gearbox - Replacement of Sheave Guard","slug":"ad-g159-1-flap-drive-control-gearbox-replacement-of-sheave-guard","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":55497,"registerId":"commonwealth-F2006B10053-current","compilationNumber":null,"startDate":"2026-04-02","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/G159/1 - Flap Drive Control Gearbox - Replacement of Sheave Guard","content":"---\nmeta-content-style-type: text/css\nmeta-content-type: application/xhtml+xml; charset=utf-8\nmeta-generator: Aspose.Words for .NET 22.10.0\n---\n\n?xml version=\"1.0\" encoding=\"utf-8\" standalone=\"no\"?>\n\nCOMMONWEALTH OF AUSTRALIA CIVIL AVIATION ORDERS CIVIL AVIATION SAFETY AUTHORITY                            PART 105 SCHEDULE OF AIRWORTHINESS DIRECTIVES\n\n![](image.001.png)  GULFSTREAM (GRUMMAN) G.159 SERIES AEROPLANES\n\n \n\nAD/G159/1 Flap Drive Control Gearbox - Replacement of\n\nSheave Guard\n\n\n1/61\n\n \n\nApplicability: S/Nos. 1 to 56 and 114. Document:  Grumman Service Change No. 79.\n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n","sortOrder":0}],"analysis":{"kimi_summary":{"content_quality":"ok","complexity_score":2,"scope_assessment":{"changed":false,"description":"This is a historical Airworthiness Directive from 1961. It remains precisely scoped to its original purpose: addressing a specific mechanical safety issue on a limited production run of Gulfstream G.159 aircraft. There is no evidence of scope creep — the document has not been expanded to cover additional aircraft types, components, or operational requirements beyond the original sheave guard replacement mandate."},"complexity_factors":["Extremely short document — only 2 substantive lines of operational content","No defined terms section — all terminology references external manufacturer documentation","Single, unambiguous compliance action (replacement of one component)","No conditional logic, exceptions, or alternative compliance methods","Simple applicability criteria (specific serial number range)","Cross-reference to only one external document (Grumman Service Change No. 79)"],"plain_english_summary":"This is an **Airworthiness Directive (AD)** — a mandatory safety order issued by Australia's Civil Aviation Safety Authority (CASA). It applies to specific Gulfstream G.159 series aeroplanes (serial numbers 1 to 56 and 114).\n\n**What it requires:**\n- Owners or operators of these specific aircraft must replace the **sheave guard** (a protective cover or shield) on the **flap drive control gearbox** (the mechanical system that controls the wing flaps).\n- The work must be done according to **Grumman Service Change No. 79** — a technical instruction from the aircraft manufacturer.\n\n**Why it matters:**\nAirworthiness Directives are legally binding safety fixes. They are issued when a design flaw, maintenance issue, or wear pattern is discovered that could affect flight safety. This particular AD dates from **January 1961** (noted as \"1/61\"), making it one of the earliest safety directives for this aircraft type. Non-compliance means the aircraft cannot legally fly in Australian airspace."},"flash_summary":{"complexity_score":3,"scope_assessment":{"changed":false,"description":"The provided excerpt contains a single airworthiness directive that mandates replacement of the sheave guard for specified G.159 serial numbers and references Grumman Service Change No. 79. There is no information in the supplied text indicating a change from an earlier scope or an amendment to a prior instrument. The directive appears to set a specific, limited scope (serial numbers 1–56 and 114) and to defer technical procedure to the referenced manufacturer service change."},"complexity_factors":["Narrow technical scope limited to a single component (sheave guard) and assembly (flap drive control gearbox), which reduces legal breadth but requires technical maintenance skills.","Reference to an external manufacturer document (Grumman Service Change No. 79) for procedural detail — compliance depends on another document not reproduced here.","Regulatory character: issued under Civil Aviation Orders, Part 105 (Airworthiness Directives), meaning non-compliance carries regulatory consequences even though those consequences are not detailed in the excerpt.","Limited applicability by serial number (S/Nos. 1–56 and 114) concentrates obligations and reduces the number of affected parties, but requires accurate aircraft identification and record checks.","Operational and logistical factors (parts procurement, certified labour and scheduling downtime) introduce practical complexity beyond the text of the AD.","The excerpt does not include compliance deadlines, inspection intervals, or enforcement language, creating uncertainty until the full AD or referenced service change is consulted."],"plain_english_summary":"This Airworthiness Directive requires replacement of the sheave guard on the flap drive control gearbox of Gulfstream (Grumman) G.159 aeroplanes with serial numbers 1–56 and 114. It affects owners, operators and maintenance organisations, who must follow Grumman Service Change No. 79 to comply; costs, parts and scheduling are the operators’ responsibility."}},"importantCases":[],"_links":{"self":"/api/acts/ad-g159-1-flap-drive-control-gearbox-replacement-of-sheave-guard","history":"/api/acts/ad-g159-1-flap-drive-control-gearbox-replacement-of-sheave-guard/history","analysis":"/api/acts/ad-g159-1-flap-drive-control-gearbox-replacement-of-sheave-guard/analysis","conflicts":"/api/acts/ad-g159-1-flap-drive-control-gearbox-replacement-of-sheave-guard/conflicts","importantCases":"/api/acts/ad-g159-1-flap-drive-control-gearbox-replacement-of-sheave-guard/important-cases","documents":"/api/acts/ad-g159-1-flap-drive-control-gearbox-replacement-of-sheave-guard/documents"}}