{"id":"F2006B10735","name":"AD/HU 369/70 - Main Transmission Tail Rotor Output Drive Pinion Shaft","slug":"ad-hu-369-70-main-transmission-tail-rotor-output-drive-pinion-shaft","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":116731,"registerId":"commonwealth-F2006B10735-current","compilationNumber":null,"startDate":"2026-04-03","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/HU 369/70 - Main Transmission Tail Rotor Output Drive Pinion Shaft","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\n# AD/HU 369/70 Main Transmission Tail Rotor Output Drive Pinion Shaft\n\nApplicability: All model 369D, 369E, 369F and 369FF series Helicopters.\n\n# 8/87\n\nTLX\n\n \n\nRequirement: Action in accordance with McDonnell Douglas SIN No. DN-147, EN-35, FN-24, as applicable.\n\n \n\nCompliance: For helicopters fitted with transmission assemblies which have the Serial Numbers listed in the “Time of Compliance” section of the Requirement Document: Within 25 hours time in service after 1 June 1987.\n\n \n\nAll other helicopters: Within 100 hours time in service after 1 June 1987. For spares: Before installation on a Helicopter after 1 June 1987.\n\nBackground: The manufacturer has received reports of the output drive pinion shafts fracturing.\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 failure mode in specific helicopter models. It has not expanded beyond its original purpose of mandating inspection/replacement of a defective pinion shaft."},"complexity_factors":["Very short document (under 300 words)","Only 4 defined applicability categories (369D, 369E, 369F, 369FF)","Simple conditional structure: two compliance deadlines based on serial number presence in manufacturer document","Single cross-reference to external manufacturer documents (SIN numbers)","No nested exceptions or complex definitional sections","Clear, unambiguous operative language ('Action in accordance with...')"],"plain_english_summary":"This CASA Airworthiness Directive mandates inspection or replacement of the main transmission tail‑rotor output drive pinion shaft on McDonnell Douglas (Hughes) and Kawasaki 369D/E/F/FF helicopters and on relevant spare parts. Affected machines must comply per manufacturer service instructions — transmissions with certain serial numbers within 25 flight hours of 1 June 1987, others within 100 hours; spares must be modified before installation.  \n\nIt responds to reported shaft fractures that could cause loss of tail‑rotor drive and catastrophic loss of control."},"flash_summary":{"complexity_score":3,"scope_assessment":{"changed":false,"description":"The directive targets the same group identified in the instrument: specific 369 series models and transmissions with listed serial numbers. It imposes inspection/repair per manufacturer instructions and sets differential compliance deadlines; there is no indication in the source text that the instrument's substantive scope was broadened or narrowed from its stated purpose to address pinion-shaft fractures."},"complexity_factors":["Dependence on external manufacturer documents (Service Instructions DN-147, EN-35, FN-24) for required action and technical detail (Requirement).","Serial-number–specific accelerated compliance window (25 hours) for listed transmissions versus a 100‑hour window for others, creating prioritisation and tracking needs (Compliance).","Different treatment of spares (must be inspected before installation) increases parts-handling and recordkeeping obligations (Compliance).","Limited model applicability (369D, 369E, 369F, 369FF) reduces scope but concentrates impact on operators of those types (Applicability).","Historical effective dates (compliance counted from 1 June 1987) create retroactive timing constraints for service records and fleet managers (Compliance)."],"plain_english_summary":"Requires operators of McDonnell Douglas (Hughes) and Kawasaki 369D/E/F/FF helicopters to carry out inspection or corrective action on the main transmission tail-rotor output drive pinion shaft following McDonnell Douglas Service Instructions DN-147, EN-35 or FN-24, with a 25‑hour deadline for certain serial-numbered transmissions and 100 hours for others; spares must be checked before installation (Compliance). The directive responds to reported pinion-shaft fractures; operators and maintenance providers bear the compliance cost and must prioritise affected serial-numbered units."}},"importantCases":[],"_links":{"self":"/api/acts/ad-hu-369-70-main-transmission-tail-rotor-output-drive-pinion-shaft","history":"/api/acts/ad-hu-369-70-main-transmission-tail-rotor-output-drive-pinion-shaft/history","analysis":"/api/acts/ad-hu-369-70-main-transmission-tail-rotor-output-drive-pinion-shaft/analysis","conflicts":"/api/acts/ad-hu-369-70-main-transmission-tail-rotor-output-drive-pinion-shaft/conflicts","importantCases":"/api/acts/ad-hu-369-70-main-transmission-tail-rotor-output-drive-pinion-shaft/important-cases","documents":"/api/acts/ad-hu-369-70-main-transmission-tail-rotor-output-drive-pinion-shaft/documents"}}