{"id":"F2006B10714","name":"AD/HU 369/51 Amdt 3 - Rotor Brake and Tail Rotor Drive Shaft Coupling","slug":"ad-hu-369-51-amdt-3-rotor-brake-and-tail-rotor-drive-shaft-coupling","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":116690,"registerId":"commonwealth-F2006B10714-current","compilationNumber":null,"startDate":"2026-04-03","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/HU 369/51 Amdt 3 - Rotor Brake and Tail Rotor Drive Shaft Coupling","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)  \nMcDonnell Douglas (Hughes) and Kawasaki 369 Series Helicopters\n\nAD/HU 369/51\n\nAmdt 3\n\n  \nRotor Brake and Tail Rotor Drive Shaft Coupling 1/87\n\nApplicability: 1. Model 369D Series Helicopters equipped with a rotor brake system P/N 369H90123, not modified in accordance with S.I.N. DN-95 (installation of fail- safe coupling);\n\n2. All model 369 Helicopters not modified in accordance with Service Information Notice DN-95, HN-173, DN-143, HN-206 or EN-31 as applicable.\n\nRequirement: 1. De-activate the rotor brake system in accordance with Part I of Hughes S.I.N. DN-94.\n\nNote: FAA AD 81-17-02 refers.\n\n2. Inspect the forward and rear flexible couplings (P/Nos. 369H92564 and/or 369A5501) in accordance with Part II of S.I.N. DN-94.\n\nCompliance: 1. Within 25 hours time in service after 26 October 1981.\n\n2. Inspect within 100 hours time in service after 31 August 1986 and thereafter at each issue of a new Maintenance Release.\n\nNote: Rotor brake may be re-activated after installation of coupling fail safe device in accordance with S.I.N. DN-95.\n\nBackground: In the past, there have been reports of several fatigue failures of forward flexible couplings on helicopters equipped with a rotor brake system. A recent investigation after an accident has revealed the possibility of either forward or rear couplings failing. Amdt 2 was issued to include both couplings, on all model 369 helicopters, for inspection. This amendment excludes helicopters amended to the requirement of AD/HU 369/68.","sortOrder":0}],"analysis":{"kimi_summary":{"content_quality":"ok","complexity_score":3,"scope_assessment":{"changed":true,"description":"Originally focused only on forward flexible couplings on rotor-brake-equipped helicopters (Amdt 1). Expanded in Amdt 2 to cover both forward and rear couplings on all Model 369 helicopters regardless of rotor brake status. This amendment (Amdt 3) further narrows the scope by excluding helicopters already covered by AD/HU 369/68, showing the directive has evolved through multiple safety iterations."},"complexity_factors":["Multiple applicability conditions requiring cross-referencing against specific part numbers and modification status","References to external documents (Service Information Notices DN-94, DN-95, HN-173, DN-143, HN-206, EN-31, and FAA AD 81-17-02) without reproducing their content","Two distinct compliance deadlines with different triggering dates","Amendment history (Amdt 3) that modifies previous requirements and excludes helicopters covered by another directive (AD/HU 369/68)"],"plain_english_summary":"This Airworthiness Directive orders operators of certain McDonnell Douglas/Kawasaki 369 helicopters to disable a specified rotor brake on Model 369D (unless fitted with a fail‑safe coupling) and to carry out recurring inspections of flexible tail‑rotor drive couplings on 369s that haven’t received listed safety service updates.\n\nIt targets owners/operators of affected 369-series aircraft to prevent fatigue failures that have caused accidents."},"flash_summary_failed":{"failed":true,"reason":"Unauthenticated. Configure AI_GATEWAY_API_KEY or use a provider module. Learn more: https://ai-sdk.dev/unauthenticated-ai-gateway","source":"analysis-cron"},"flash_summary":{"complexity_score":5,"scope_assessment":{"changed":true,"description":"This amendment narrows the population subject to the directive by excluding helicopters already amended to meet AD/HU 369/68 (Background). It also expressly ties applicability to whether specific Service Information Notices have been incorporated (Applicability), so compliance obligations shift depending on prior modifications. Operators of affected helicopters must pay for de‑activation, inspections and any corrective work; they must meet short compliance windows (25 and 100 flight hours) and ongoing inspection at each new Maintenance Release (Compliance: 1–2)."},"complexity_factors":["Multiple applicability conditions across model variants and specific part numbers (Applicability).","Dependence on prior or alternative service modifications (S.I.N. DN-95, HN-173, DN-143, HN-206, EN-31) which change whether the AD applies (Applicability; Background).","Two separate mandatory actions (de‑activation and inspection) with different compliance timeframes (Compliance: 1 and 2).","Recurring inspection obligation tied to each issue of a new Maintenance Release (Compliance: 2).","Technical specificity of components to inspect (forward and rear flexible couplings, P/Ns 369H92564 and/or 369A5501) increasing maintenance precision (Requirement 2).","Conditional re‑activation of rotor brake only after installation of fail‑safe coupling per S.I.N. DN-95 (Note under Requirement/Compliance).","Cross-reference to an external FAA AD and multiple Service Information Notices increases traceability and administrative steps (Note; Requirement).","Enforcement and compliance depend on operators performing maintenance and recording Maintenance Releases, creating practical monitoring complexity (Compliance: 2)."],"plain_english_summary":"This airworthiness directive requires certain McDonnell Douglas (Hughes)/Kawasaki 369 helicopters to have the rotor brake de‑activated and the forward and rear flexible couplings inspected, unless the helicopter already has specified fail‑safe or modification work. It responds to reported fatigue failures of coupling components and sets deadlines: de‑activate within 25 flight hours and inspect within 100 hours and at each new Maintenance Release. Rotor brakes may be re‑activated after fitment of the approved fail‑safe coupling device."}},"importantCases":[],"_links":{"self":"/api/acts/ad-hu-369-51-amdt-3-rotor-brake-and-tail-rotor-drive-shaft-coupling","history":"/api/acts/ad-hu-369-51-amdt-3-rotor-brake-and-tail-rotor-drive-shaft-coupling/history","analysis":"/api/acts/ad-hu-369-51-amdt-3-rotor-brake-and-tail-rotor-drive-shaft-coupling/analysis","conflicts":"/api/acts/ad-hu-369-51-amdt-3-rotor-brake-and-tail-rotor-drive-shaft-coupling/conflicts","importantCases":"/api/acts/ad-hu-369-51-amdt-3-rotor-brake-and-tail-rotor-drive-shaft-coupling/important-cases","documents":"/api/acts/ad-hu-369-51-amdt-3-rotor-brake-and-tail-rotor-drive-shaft-coupling/documents"}}