{"id":"F2006B02491","name":"AD/AS 355/37 - Tail Rotor Pitch Control Lever Expansion Pin","slug":"ad-as-355-37-tail-rotor-pitch-control-lever-expansion-pin","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":41747,"registerId":"commonwealth-F2006B02491-current","compilationNumber":null,"startDate":"2026-04-01","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/AS 355/37 - Tail Rotor Pitch Control Lever Expansion Pin","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 355/37 Tail Rotor Pitch Control Lever Expansion Pin 9/91\n\nDM\n\n \n\nApplicability: All AS 355 helicopters versions E, F, F1, F2 and N.\n\n \n\nRequirement: Action in accordance with the Technical Requirements of DGAC TAD T91-138-043 (B).\n\n \n\nNote: Aerospatiale TSB 01-34 refers.\n\n \n\nCompliance: As specified in the Requirement Document with revised effective date of 10 July 1991.\n\n \n\nBackground:  One lug of the tail rotor gearbox control lever hinge yoke failed through incorrect assembly of the bushes on the expansion pin.\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 standard airworthiness directive format unchanged from its original purpose: addressing a specific mechanical defect in a specific aircraft type. The scope remains tightly focused on the tail rotor pitch control lever issue."},"complexity_factors":["Very short document (approximately 150 words)","Only 1 defined applicability criterion (helicopter model numbers)","Single requirement referencing external technical document rather than spelling out procedures","No nested conditional logic or exceptions","No cross-references to other legislation or regulations beyond the enabling Civil Aviation Regulations 1998","Straightforward compliance deadline structure"],"plain_english_summary":"This is an **Airworthiness Directive** — essentially a mandatory safety notice issued by Australia's Civil Aviation Safety Authority (CASA) for specific helicopters.\n\n**What it does:**\nOrders owners and operators of certain Eurocopter AS 355 \"Twin Ecureuil\" helicopters to inspect and fix a dangerous defect in the tail rotor control system.\n\n**The safety problem:**\nThe tail rotor gearbox has a control lever with an \"expansion pin\" (a type of fastener that holds parts together). If the bushes (sleeve bearings) on this pin are assembled incorrectly, one of the lugs (projecting arms) on the hinge yoke can break. A failed tail rotor control means the pilot cannot control the helicopter's yaw (directional control), which can cause a crash.\n\n**Who must act:**\nAnyone operating AS 355 helicopters — specifically versions E, F, F1, F2, and N.\n\n**What they must do:**\nFollow the technical instructions in a French aviation safety document (DGAC TAD T91-138-043(B)), which details the inspection and repair procedures. There's also a reference to an Aerospatiale Technical Service Bulletin (TSB 01-34) for additional guidance.\n\n**When:**\nBy the deadlines specified in that French document, with the effective date updated to 10 July 1991.\n\n**Why it matters:**\nThis directive prevents catastrophic failure of the tail rotor controls. The background notes this already happened once due to incorrect assembly, so this is a \"fix it before it breaks\" order to prevent accidents."},"flash_summary":{"complexity_score":3,"scope_assessment":{"changed":false,"description":"The document defines its scope within the AD: it applies to all AS 355 helicopters versions E, F, F1, F2 and N and requires compliance with the named DGAC technical document. The AD does not indicate any change to that scope within the text provided, nor does it provide a prior scope to compare against."},"complexity_factors":["Short, single-issue directive focused on one component (tail rotor pitch control lever expansion pin) which reduces substantive complexity.","Relies on an external technical document (DGAC TAD T91-138-043 (B)) for procedural detail, requiring users to obtain and interpret that document.","Applicability lists multiple helicopter sub-models (E, F, F1, F2, N), so recipients must check model-level applicability.","Technical nature (mechanical assembly/inspection) requires specialist maintenance knowledge to implement, despite the AD itself being brief.","Compliance timing is specified indirectly (revised effective date), which can create procedural complexity in tracking deadlines and versions."],"plain_english_summary":"This airworthiness directive makes compliance mandatory for owners/operators of Eurocopter AS355 (E, F, F1, F2, N) helicopters: they must carry out the technical actions in DGAC TAD T91‑138‑043 (B) by the revised effective date (10 July 1991). It responds to a tail‑rotor gearbox hinge‑yoke lug failure caused by incorrectly assembled bushes on the expansion pin. The immediate operational and financial burden falls on operators, who must obtain and follow the DGAC Requirement Document."}},"importantCases":[],"_links":{"self":"/api/acts/ad-as-355-37-tail-rotor-pitch-control-lever-expansion-pin","history":"/api/acts/ad-as-355-37-tail-rotor-pitch-control-lever-expansion-pin/history","analysis":"/api/acts/ad-as-355-37-tail-rotor-pitch-control-lever-expansion-pin/analysis","conflicts":"/api/acts/ad-as-355-37-tail-rotor-pitch-control-lever-expansion-pin/conflicts","importantCases":"/api/acts/ad-as-355-37-tail-rotor-pitch-control-lever-expansion-pin/important-cases","documents":"/api/acts/ad-as-355-37-tail-rotor-pitch-control-lever-expansion-pin/documents"}}