{"id":"F2006B10732","name":"AD/HU 369/68 - Tail Rotor Drive Shaft Coupling","slug":"ad-hu-369-68-tail-rotor-drive-shaft-coupling","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":116725,"registerId":"commonwealth-F2006B10732-current","compilationNumber":null,"startDate":"2026-04-03","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/HU 369/68 - 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 369/68 Tail Rotor Drive Shaft Coupling 1/87\n\nApplicability: All model 369, 369A, 369D, 369E, 369H, 369HE, 369HM and 369HS Helicopters fitted with tail rotor drive shaft flexible couplings Part No. 369A5501 or 369H92564.\n\nRequirement: 1. Install forward and aft flexible coupling failsafe device (PN’s 369D25530 bolt and 369D25531 socket) in accordance with the applicable Service Information Notice, DN-95 or HN-173, for forward coupling and DN-143, HN-206 or EN-31 for aft coupling.\n\n    2. Check for Tail Rotor backlash or looseness by rocking the Tail Rotor back and forth in its plane of rotation. The blade should not move in excess of 1.93cm (0.75 inch) at the blade tip without rotation of the main rotor blades.\n\n    3. If tail rotor blade tip movement exceeds the specified limit inspect and replace as necessary either or both forward and aft tail rotor drive shaft couplings.\n\nNote: FAA AD86-20-07 refers.\n\nCompliance: 1. Unless already accomplished, at the next Maintenance Release inspection after 31 March 1987.\n\n    2. At each pre-flight check and anytime “thumping” or “rapping” is heard from the tail rotor drive during final tail rotor run down.\n\n    3. Before further flight.\n\nNote: This Directive shall be entered on the Maintenance Release as maintenance required. The inspection required by Para 2 may be performed by the pilot in command, in which case certification is not required. A copy of this Directive shall be carried in the aircraft.\n\nBackground: Investigation overseas has disclosed that repetitive inspections as previously required are inadequate to intercept impending failure.","sortOrder":0}],"analysis":{"flash_summary_failed":{"failed":true,"reason":"A positive credit balance is required for all requests, including BYOK, so fallback providers remain available. Add credits at https://vercel.com/d?to=%2F%5Bteam%5D%2F%7E%2Fai%3Fmodal%3Dtop-up to continue.","source":"analysis-cron"},"kimi_summary":{"content_quality":"ok","complexity_score":3,"scope_assessment":{"changed":false,"description":"This Airworthiness Directive maintains its original narrow scope—addressing a specific mechanical defect in specific helicopter models. The requirements remain tightly focused on the tail rotor drive shaft coupling issue identified in the background. No scope creep is evident; the directive does not expand into unrelated systems or impose broader operational restrictions beyond what is necessary to address the identified safety risk."},"complexity_factors":["Short, single-purpose directive with clear applicability section","Only 3 main requirements with straightforward compliance dates","Minimal defined terms (only standard aviation abbreviations like 'PN' for Part Number)","No nested exceptions or conditional logic beyond standard 'unless already accomplished' clause","Single cross-reference to FAA AD (provided as background only, not binding)","Practical measurement provided in both metric and imperial units (1.93cm/0.75 inch)","Clear background statement explaining safety rationale"],"plain_english_summary":"This safety order requires owners/operators of specified Hughes/Kawasaki 369-series helicopters with certain tail rotor drive shaft couplings to install failsafe devices and to perform regular looseness checks by rocking the tail rotor blades. If blade tip movement exceeds 1.93 cm (~¾\"), couplings must be inspected and fixed before flight. Intended to prevent catastrophic loss of tail-rotor control, the directive mandates installation by the next maintenance after March 31, 1987, allows pilots to do the rocking check, and must be carried aboard."},"flash_summary":{"complexity_score":5,"scope_assessment":{"changed":false,"description":"Scope remains focused on 369-series helicopters fitted with the specified flexible coupling part numbers. The directive requires installation of failsafe devices, routine and event-driven inspections, and replacement when the specified backlash limit is exceeded; it does not broaden applicability beyond the listed models or parts."},"complexity_factors":["Technical specificity: exact coupling part numbers and a precise blade-tip movement limit of 1.93 cm (Requirement 2).","Multiple affected airframes: several 369-series models listed with applicability limited to aircraft fitted with specified couplings (Applicability).","Specified retrofit/installation actions tied to particular parts and Service Information Notices, requiring conformity with different documents for forward and aft couplings (Requirement 1).","Layered compliance triggers and timing: next Maintenance Release after a date, each pre-flight check, event-driven checks on unusual noises, and 'before further flight' for defects (Compliance).","Division of inspection responsibility: pilots may perform the pre-flight check without certification, while installation and replacements imply maintenance personnel action (Compliance note; Requirement 1 & 3).","Recordkeeping and carriage requirements: directive must be entered on the Maintenance Release and a copy carried in the aircraft (Note).","Cross-reference to external regulator action (FAA AD86-20-07), creating alignment/verification considerations (Note).","Replacement decision rule: inspection threshold leads to inspection and possible replacement of forward and/or aft couplings, implying parts inventory and logistics impact (Requirement 3)."],"plain_english_summary":"**Requires fitted failsafe parts and checks on tail-rotor couplings.** This directive mandates installing specified forward and aft failsafe devices, checking tail-rotor backlash (blade-tip movement must not exceed 1.93 cm), and replacing couplings if looseness is found. \n\nIt applies to McDonnell Douglas (Hughes) and Kawasaki 369 series helicopters that have the listed coupling part numbers and follows overseas findings that routine inspections alone were not reliably preventing failures."}},"importantCases":[],"_links":{"self":"/api/acts/ad-hu-369-68-tail-rotor-drive-shaft-coupling","history":"/api/acts/ad-hu-369-68-tail-rotor-drive-shaft-coupling/history","analysis":"/api/acts/ad-hu-369-68-tail-rotor-drive-shaft-coupling/analysis","conflicts":"/api/acts/ad-hu-369-68-tail-rotor-drive-shaft-coupling/conflicts","importantCases":"/api/acts/ad-hu-369-68-tail-rotor-drive-shaft-coupling/important-cases","documents":"/api/acts/ad-hu-369-68-tail-rotor-drive-shaft-coupling/documents"}}