{"id":"F2006B02529","name":"AD/AS 355/8 - Main Gearbox Filter - Inspection","slug":"ad-as-355-8-main-gearbox-filter-inspection","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":41785,"registerId":"commonwealth-F2006B02529-current","compilationNumber":null,"startDate":"2026-04-01","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/AS 355/8 - Main Gearbox Filter - Inspection","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 Regulations 1998), PART 39 - 105 CIVIL AVIATION SAFETY AUTHORITY\n\nSCHEDULE OF AIRWORTHINESS DIRECTIVES\n\n \n\n![](image.001.png)  Eurocopter AS 355 (Twin Ecureuil) Series Helicopters\n\n \n\nAD/AS 355/8 Main Gearbox Filter - Inspection 3/83\n\nApplicability: All model AS 355 helicopters, having the main gearbox fitted with a TEDECO magnetic plug, Part Number B4439 with electrical indication (optional SB 63.02 refers) and not modified in accordance with A.M.S. 07.1211.\n\n \n\nDocument: AS 355 SB 05.07.\n\n \n\nNote: Bureau Veritas AD 82-180-9(B) refers.\n\n \n\nCompliance: At periods not exceeding 100 hours time in service after 31st March 1983.\n\n \n\nBackground:  The manufacturer advises of the need to reduce the inspection interval for the main gearbox oil filter, on helicopters fitted with the TEDECO magnetic plug installation.\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 discrete, single-issue safety directive from 1983 addressing a specific technical problem with a specific helicopter component. It has not expanded beyond its original narrow purpose of mandating more frequent gearbox filter inspections for affected AS 355 helicopters."},"complexity_factors":["Very short document (approximately 200 words)","Only 4 defined applicability criteria (model, part number, electrical indication, modification status)","Single compliance requirement with clear time threshold (100 hours)","No cross-references to other legislation sections — only references to manufacturer documents (SB 05.07, A.M.S. 07.1211)","No conditional logic or nested exceptions","Straightforward command structure: 'applies to X, do Y by Z date'"],"plain_english_summary":"This is an **Airworthiness Directive (AD)** — essentially a mandatory safety order issued by Australia's Civil Aviation Safety Authority (CASA) for aircraft.\n\n**What it does:**\nIt requires owners and operators of specific Eurocopter AS 355 helicopters (also known as \"Twin Ecureuil\" helicopters) to inspect the main gearbox oil filter more frequently than before.\n\n**Who it affects:**\n- Owners and operators of AS 355 model helicopters\n- Specifically those with a particular type of magnetic plug (TEDECO brand, Part Number B4439) that has an electrical warning indicator\n- Only applies if the helicopter has **not** been modified according to a specific technical bulletin (A.M.S. 07.1211)\n\n**What must be done:**\n- Inspect the main gearbox filter at least every 100 hours of flight time\n- This new schedule started from 31 March 1983\n\n**Why it matters:**\nThe helicopter manufacturer identified a safety concern with the TEDECO magnetic plug installation that requires more frequent checks to prevent potential gearbox failures. Gearbox failures in helicopters can be catastrophic, so this directive forces operators to catch problems early through more regular inspections.\n\n**Key terms explained:**\n- **Airworthiness Directive (AD):** A legally enforceable safety notice that aircraft owners must follow to keep their aircraft airworthy\n- **Time in service:** Actual flight hours (not just calendar time)\n- **SB (Service Bulletin):** Manufacturer's technical notice about maintenance or modifications\n- **Magnetic plug:** A drain plug with a magnet that attracts metal particles, revealing internal wear or damage in the gearbox"},"flash_summary":{"complexity_score":2,"scope_assessment":{"changed":false,"description":"The directive narrows the maintenance interval for the main gearbox oil filter for the specified subset of AS 355 helicopters (those with TEDECO magnetic plug Part No. B4439 with electrical indication and not modified per A.M.S. 07.1211). It does not expand applicability beyond that stated group and does not introduce additional types of obligations beyond the inspection interval and reference to the service bulletin (Applicability; Compliance; Document)."},"complexity_factors":["Narrow, specific applicability (single helicopter model with a specific part and modification exclusion) (Applicability)","Single, fixed compliance action and interval (inspection at ≤100 hours TIS) (Compliance)","Reliance on an external service bulletin (AS 355 SB 05.07) for procedural detail (Document)","Cross-reference to another authority AD (Bureau Veritas AD 82-180-9(B)) which may add external requirements (Note)","Temporal start date stated (31 March 1983) but no staged implementation or multiple conditional pathways (Compliance)"],"plain_english_summary":"This AD mandates inspection of the main gearbox oil filter on Eurocopter AS 355 helicopters fitted with a TEDECO magnetic plug (Part No. B4439) with electrical indication, at intervals not exceeding 100 hours time‑in‑service, effective from 31 March 1983. Helicopters modified per A.M.S. 07.1211 are exempt.\n\nIt affects owners, operators and maintenance organisations, increasing recurring inspection costs and downtime and creating an incentive to pursue the A.M.S. 07.1211 modification; inspection procedure is in AS 355 SB 05.07."}},"importantCases":[],"_links":{"self":"/api/acts/ad-as-355-8-main-gearbox-filter-inspection","history":"/api/acts/ad-as-355-8-main-gearbox-filter-inspection/history","analysis":"/api/acts/ad-as-355-8-main-gearbox-filter-inspection/analysis","conflicts":"/api/acts/ad-as-355-8-main-gearbox-filter-inspection/conflicts","importantCases":"/api/acts/ad-as-355-8-main-gearbox-filter-inspection/important-cases","documents":"/api/acts/ad-as-355-8-main-gearbox-filter-inspection/documents"}}