{"id":"F2006B02533","name":"AD/AS 355/9 - Main Gear Box Bevel Reduction Gear Module - Inspection of Bevel Ring Gear/Vertical Shaft Attachment Bolts","slug":"ad-as-355-9-main-gear-box-bevel-reduction-gear-module-inspection-of-bevel-ring-gear-vertical-shaft-a","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":41789,"registerId":"commonwealth-F2006B02533-current","compilationNumber":null,"startDate":"2026-04-01","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/AS 355/9 - Main Gear Box Bevel Reduction Gear Module - Inspection of Bevel Ring Gear/Vertical Shaft Attachment Bolts","content":"COMMONWEALTH OF AUSTRALIA (Civil Aviation Regulations 1998), PART 39 \\- 105 CIVIL AVIATION SAFETY AUTHORITY\n\nSCHEDULE OF AIRWORTHINESS DIRECTIVES\n\n![](image.001.png)  \nEurocopter AS 355 (Twin Ecureuil) Series Helicopters\n\nAD/AS 355/9 Main Gear Box Bevel Reduction Gear\n\nModule - Inspection of Bevel Ring Gear/Vertical Shaft Attachment Bolts\n\n  \n3/83\n\nApplicability: All model AS 355 helicopters fitted with a main gearbox containing bevel reduction gear assembly, Part Number 355A.32.0600.00 and 01, not modified under A.M.S.\n\n07.7082 or A.M.S. 07.7083.\n\nDocument: AS 355 SB 05.05.\n\nNote: Bureau Veritas AD 82-178-8(B) refers.\n\nCompliance: PART 1: Within 10 hours time in service after 31st March 1983 every 50 hours thereafter, prior to compliance with Part 2: Carry out the visual check.\n\nPART 2: Within 300 hours time in service after 31st March 1983: Carry out the screw tightening check, as a one time only inspection.\n\nPART 3: Every 300 hours time in service, after compliance with Part 2: Carry out the visual check.\n\nBackground: The manufacturer advises that there have been several cases of sheared and loose bolts, securing the bevel ring gear to the vertical shaft, found during maintenance operations.","sortOrder":0}],"analysis":{"kimi_summary":{"content_quality":"ok","complexity_score":3,"scope_assessment":{"changed":false,"description":"This is a discrete, targeted safety directive addressing a specific mechanical defect identified by the manufacturer. It has not expanded beyond its original purpose of mandating bolt inspections on affected AS 355 helicopters."},"complexity_factors":["Single discrete subject matter (specific bolt inspection on specific helicopter model)","Only 2 defined part numbers for applicability","Clear three-part compliance schedule with specific time-in-service thresholds","Minimal cross-referencing (one service bulletin and one foreign airworthiness directive noted)","No nested conditional logic or exceptions beyond the two modification exclusions","Short document (approximately 200 words of substantive content)"],"plain_english_summary":"This CASA Airworthiness Directive mandates inspections of the main gearbox bolts that attach the bevel ring gear to the vertical shaft on certain Eurocopter AS355 helicopters after reports of sheared or loose bolts. It applies to helicopters with specified gearbox part numbers, excluding those already modified by two named service bulletins.\n\nThe AD requires immediate and recurring visual inspections plus a one‑time torque check, to detect loose or broken bolts and prevent catastrophic gearbox failure."},"flash_summary":{"complexity_score":3,"scope_assessment":{"changed":false,"description":"Scope remains targeted to AS 355 helicopters with the specified main gearbox part numbers and excludes gearboxes modified under the two listed A.M.S. modifications. The directive addresses a specific component (bevel ring gear/vertical shaft attachment bolts) and prescribes inspection actions; it does not broaden applicability beyond those equipment and modification conditions."},"complexity_factors":["Technical specificity: applies only to AS 355 helicopters fitted with main gearbox P/N 355A.32.0600.00 and .01 (applicability condition).","Conditional exclusions: excludes gearboxes modified under A.M.S. 07.7082 or A.M.S. 07.7083.","Multiple inspection types and timing: near-term visual check, one-time screw-tightening check, and recurring visual checks at different hour intervals.","Operational impact: requires maintenance access, skilled personnel, and aircraft out-of-service time.","References to external documents: relies on Service Bulletin AS 355 SB 05.05 and notes Bureau Veritas AD 82-178-8(B).","Safety-critical component: bolt failures on bevel ring gear/vertical shaft have direct flight-safety implications."],"plain_english_summary":"This directive requires operators of certain Eurocopter AS 355 helicopters (those with a specific main gearbox part number and not modified under stated modifications) to inspect the bolts that attach the bevel ring gear to the vertical shaft. It mandates a near-term visual check, a one‑time screw‑tightening inspection, and recurring visual checks to address reported sheared or loose bolts. Operators pay inspection costs and face aircraft downtime; the measure mechanically reduces risk by finding and correcting loose or broken attachment bolts."}},"importantCases":[],"_links":{"self":"/api/acts/ad-as-355-9-main-gear-box-bevel-reduction-gear-module-inspection-of-bevel-ring-gear-vertical-shaft-a","history":"/api/acts/ad-as-355-9-main-gear-box-bevel-reduction-gear-module-inspection-of-bevel-ring-gear-vertical-shaft-a/history","analysis":"/api/acts/ad-as-355-9-main-gear-box-bevel-reduction-gear-module-inspection-of-bevel-ring-gear-vertical-shaft-a/analysis","conflicts":"/api/acts/ad-as-355-9-main-gear-box-bevel-reduction-gear-module-inspection-of-bevel-ring-gear-vertical-shaft-a/conflicts","importantCases":"/api/acts/ad-as-355-9-main-gear-box-bevel-reduction-gear-module-inspection-of-bevel-ring-gear-vertical-shaft-a/important-cases","documents":"/api/acts/ad-as-355-9-main-gear-box-bevel-reduction-gear-module-inspection-of-bevel-ring-gear-vertical-shaft-a/documents"}}