{"id":"F2006B10752","name":"AD/HU 369/88 - Tailrotor Swashplate Locknut Lock Washer","slug":"ad-hu-369-88-tailrotor-swashplate-locknut-lock-washer","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":116765,"registerId":"commonwealth-F2006B10752-current","compilationNumber":null,"startDate":"2026-04-03","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/HU 369/88 - Tailrotor Swashplate Locknut Lock Washer","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)  McDonnell Douglas (Hughes) and Kawasaki 369 Series Helicopters\n\n \n\nAD/HU 369/88 Tailrotor Swashplate Locknut Lock Washer 1/95\n\nDM\n\n \n\nApplicability: Models 369D, 369E and 369F/FF Series.\n\n \n\nRequirement: Action in accordance with MDHC SINs DN-185, EN-78 or FN-64 as applicable.\n\n \n\nCompliance: Within 25 hours time in service after 9 November 1994, thereafter inspect at intervals not exceeding 100 hours time in service.\n\n \n\nBackground: There have been reports of the MS172209 lockwashers failing due to a flaw in the tang. Failure of the tang could allow the locknut to lose torque, and thereby causing eventual disengagement of the assembly resulting in loss of tail rotor control.\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, targeted safety directive addressing a specific mechanical defect in specific helicopter models. It has not expanded beyond its original purpose of mandating inspection and replacement of a faulty lock washer component."},"complexity_factors":["Single, specific mechanical defect addressed","Only 3 helicopter model variants affected","Clear compliance timeline (25 hours initial, 100 hours recurring)","References external manufacturer documents (SINs) but does not reproduce them","No defined terms section, no conditional logic, no nested exceptions","Total length: approximately 150 words of substantive content"],"plain_english_summary":"This is an **Airworthiness Directive** — a mandatory safety order issued by Australia's Civil Aviation Safety Authority (CASA) for specific helicopter models.\n\n**What it does:**\nOrders owners and operators of certain McDonnell Douglas (Hughes) and Kawasaki 369 series helicopters (models 369D, 369E, and 369F/FF) to inspect and fix a dangerous defect in the tail rotor system.\n\n**The problem:**\nA small metal part called a **lock washer** (specifically model MS172209) used in the tail rotor swashplate assembly has a design flaw in its \"tang\" (a projecting piece that helps lock the nut in place). If the tang breaks, the locknut can loosen over time. This could cause the tail rotor assembly to come apart, resulting in **complete loss of tail rotor control** — which means the pilot cannot control the helicopter's direction, potentially causing a crash.\n\n**What must be done:**\n- **Initial action:** Inspect and repair according to specific manufacturer service bulletins (called Service Information Notices or SINs) within 25 flight hours after 9 November 1994\n- **Ongoing:** Repeat inspections at least every 100 flight hours thereafter\n\n**Who it affects:**\nOwners, operators, and maintenance engineers of the affected helicopter models in Australia.\n\n**Why it matters:**\nThis is a **flight-critical safety issue**. The tail rotor keeps the helicopter from spinning uncontrollably. Failure of this small washer could lead to catastrophic loss of control and fatalities."},"flash_summary":{"complexity_score":3,"scope_assessment":{"changed":false,"description":"The AD, as provided, implements a targeted inspection and corrective-action requirement for MS172209 lockwashers on specified Model 369 helicopters. There is no material in the supplied text indicating a change in the AD's scope from its original purpose; it explicitly applies to Models 369D, 369E and 369F/FF, requires actions per MDHC SINs, and sets the initial and recurring inspection intervals (see \"Applicability\", \"Requirement\", \"Compliance\", \"Background\")."},"complexity_factors":["Cross-reference to manufacturer Service Information Notices (DN-185, EN-78, FN-64) requires operators to obtain and interpret external technical documents (Requirement).","Technical specificity about a particular part (MS172209 lockwasher) and a specific failure mode (tang flaw) requires specialist maintenance knowledge (Background).","Compliance timing uses flight hours metric (time in service) with an initial short window (25 hours) and recurring interval (100 hours) that affects scheduling and operations (Compliance).","Potential dependency on availability of replacement parts or approved repair procedures not contained in the AD itself increases practical implementation steps.","Relatively narrow applicability to specific helicopter models reduces breadth but concentrates affected operators and suppliers (Applicability)."],"plain_english_summary":"This AD requires owners/operators of certain McDonnell Douglas (Hughes) and Kawasaki Model 369 helicopters to inspect the tailrotor swashplate locknut lockwasher (MS172209) and carry out any corrective work specified in MDHC SINs DN-185, EN-78 or FN-64. Initial inspection is within 25 hours TIS after 9 Nov 1994, then every 100 hours TIS.\n\nThe rule was issued after reports of lockwasher tang failure that could allow locknut torque loss and tail rotor disengagement. Operators bear inspection and repair costs and must follow the manufacturer SINs."}},"importantCases":[],"_links":{"self":"/api/acts/ad-hu-369-88-tailrotor-swashplate-locknut-lock-washer","history":"/api/acts/ad-hu-369-88-tailrotor-swashplate-locknut-lock-washer/history","analysis":"/api/acts/ad-hu-369-88-tailrotor-swashplate-locknut-lock-washer/analysis","conflicts":"/api/acts/ad-hu-369-88-tailrotor-swashplate-locknut-lock-washer/conflicts","importantCases":"/api/acts/ad-hu-369-88-tailrotor-swashplate-locknut-lock-washer/important-cases","documents":"/api/acts/ad-hu-369-88-tailrotor-swashplate-locknut-lock-washer/documents"}}