{"id":"F2006B10736","name":"AD/HU 369/71 - Tail Rotor Transmission Mounting Studs","slug":"ad-hu-369-71-tail-rotor-transmission-mounting-studs","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":116733,"registerId":"commonwealth-F2006B10736-current","compilationNumber":null,"startDate":"2026-04-03","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/HU 369/71 - Tail Rotor Transmission Mounting Studs","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 369/71 Tail Rotor Transmission Mounting Studs 13/87\n\nTLX\n\nApplicability: All model 369D, 369E, 369F and 369FF series helicopters.\n\nRequirement: Action in accordance with McDonnell Douglas SIN No DN-151, EN-39, FN-28, as applicable.\n\nCompliance: Part 1 of Requirement document \\- unless already accomplished, prior to next flight.\n\nPart 2 of Requirement document \\- during each pilot’s preflight inspection.\n\nPart 3 of Requirement document \\- unless already accomplished, within 25 hours time in service or by 20 November 1987 whichever occurs first.\n\nPart 4 of Requirement document \\- prior to each issue or a new Maintenance Release after 20 November 1987.\n\nNote: The Part 2 inspection may be accomplished by the pilot in command in which case he shall enter and certify for this AD in Col 2 Part 3 of the Maintenance Release on each occasion.\n\nBackground: There have been several reported instances where some or all tail rotor transmission mounting studs have failed with indications of bending fatigue. Also, movement between the T/R gearbox and mounting bracket has occurred due to loss of mounting stud nut torque.","sortOrder":0}],"analysis":{"kimi_summary":{"content_quality":"ok","complexity_score":3,"scope_assessment":{"changed":false,"description":"This is a discrete, time-bound safety directive addressing a specific mechanical failure mode. It has not expanded beyond its original purpose of mandating inspections and repairs for tail rotor transmission mounting studs on the specified helicopter models."},"complexity_factors":["Short, single-purpose directive with clear applicability (4 specific helicopter models)","Four distinct compliance deadlines with straightforward timing triggers (next flight, preflight, 25 hours/20 Nov 1987, each new Maintenance Release)","Relies on external technical documents (McDonnell Douglas Service Information Notices) for actual procedural details rather than spelling them out","Single defined term ('time in service') used in standard aviation sense","Simple conditional logic (unless already accomplished)","One procedural note regarding pilot certification in Maintenance Release"],"plain_english_summary":"This Airworthiness Directive orders urgent inspections and repairs to the tail-rotor transmission mounting studs on certain Hughes/Kawasaki 369-series helicopters after reports of stud failure and gearbox loosening from fatigue. Failure risks tail-rotor loss and catastrophic control failure.\n\nIt requires pilots to visually check studs before every flight and maintenance crews to carry out immediate and short-term detailed inspections and corrective work to secure the gearbox and prevent recurrence."},"flash_summary":{"complexity_score":3,"scope_assessment":{"changed":false,"description":"The directive confines action to listed 369 series models and mandates inspections/repairs addressing reported mounting-stud failures and nut torque loss per specified service instructions (Applicability; Requirement; Background). It does not expand the fleet or issues covered beyond those failures described."},"complexity_factors":["Reference to external manufacturer service instructions (DN-151, EN-39, FN-28) requires cross-reading and creates dependency on non-statutory documents (Requirement).","Multiple distinct compliance deadlines (immediate before next flight; recurring preflight checks; 25 hours or calendar date; maintenance-release requirement) increase scheduling and tracking burden (Compliance: Parts 1–4).","Permits pilot-performed inspections and certification, shifting responsibility and requiring pilot record entries (Note; Part 2).","Safety-critical, technical inspections and repairs likely need maintenance resources and parts, imposing operational downtime and direct costs on operators (Background; Parts 1,3).","Narrow applicability to specific models reduces breadth but concentrates impact on operators of those types (Applicability)."],"plain_english_summary":"This airworthiness directive requires inspections and corrective action on tail-rotor transmission mounting studs for all McDonnell Douglas (Hughes) and Kawasaki 369D/E/F/FF helicopters, following McDonnell Douglas Service Instructions DN-151/EN-39/FN-28 because studs have failed and nut torque loss was reported (Background). Operators must do an initial action before the next flight (Part 1), pilots must perform and can certify preflight checks each flight (Part 2; Note), repairs are mandatory within 25 flight hours or by 20 Nov 1987 (Part 3), and maintenance releases updated (Part 4). Operators bear repair and compliance costs; pilots and maintenance staff decide, perform and record the inspections and repairs (Parts 1–4, Note)."}},"importantCases":[],"_links":{"self":"/api/acts/ad-hu-369-71-tail-rotor-transmission-mounting-studs","history":"/api/acts/ad-hu-369-71-tail-rotor-transmission-mounting-studs/history","analysis":"/api/acts/ad-hu-369-71-tail-rotor-transmission-mounting-studs/analysis","conflicts":"/api/acts/ad-hu-369-71-tail-rotor-transmission-mounting-studs/conflicts","importantCases":"/api/acts/ad-hu-369-71-tail-rotor-transmission-mounting-studs/important-cases","documents":"/api/acts/ad-hu-369-71-tail-rotor-transmission-mounting-studs/documents"}}