{"id":"F2006B10649","name":"AD/HU 269/91 - Main Transmission Pinion Assembly","slug":"ad-hu-269-91-main-transmission-pinion-assembly","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"repealed","isInForce":false,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":116562,"registerId":"commonwealth-F2006B10649-current","compilationNumber":null,"startDate":"2026-04-03","status":"Repealed","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/HU 269/91 - Main Transmission Pinion Assembly","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)  \nSchweizer (Hughes) 269 Series Helicopters\n\nAD/HU 269/91 Main Transmission Pinion Assembly 2/88\n\nApplicability: 1. All model helicopters fitted with main transmission pinion assembly P/No 269A5103, 269A5103-9 and 269A5103-21 not previously inspected in accordance with AD/HU-269/63B.\n\n2. All 269A5103-31 main transmission pinion assemblies with serial numbers that do not begin with the letter S.\n\nNote: This Directive supersedes AD/HU-269/63B.\n\nRequirement: Action in accordance with Schweizer SIN N-216.\n\nCompliance: For Helicopters: Within 300 hours time in service after 25 January 1988 or by 30 June 1988 which ever occurs first.\n\nFor Spares: Before installation on an aircraft after 25 January 1988.\n\nBackground: The manufacturer advises that cracking of the pinion assembly has occurred in service. Failure of the pinion could result in loss of drive to the main rotor. This Directive has been raised to include requirements of SIN N.216 which superseded SIN N.170 and SIN N.151.2.","sortOrder":0}],"analysis":{"kimi_summary":{"_metrics":{"model":"kimi-k2.5","source":"moonshot-batch","completionTokens":1786},"content_quality":"ok","complexity_score":3,"scope_assessment":{"changed":false,"description":"This remains a targeted airworthiness directive addressing a specific mechanical defect in helicopter transmission systems. The scope is confined to the original safety concern regarding cracking in main transmission pinion assemblies and has not expanded beyond this technical maintenance requirement."},"complexity_factors":["Specific part number identification requiring technical cross-referencing (four distinct part numbers)","Serial number exclusion criteria (excluding assemblies with serial numbers beginning with 'S')","Dual compliance timeline requiring calculation of both flight hours and calendar dates","Incorporation by reference of external technical document (Schweizer SIN N-216) not reproduced in the directive","Conditional applicability excluding previously inspected assemblies"],"plain_english_summary":"This directive orders owners/operators of Hughes (Schweizer) 269 helicopters with specific main transmission pinion assemblies (parts 269A5103, 269A5103-9, 269A5103-21, and some 269A5103-31 serials) to inspect or replace them per the manufacturer’s Service Instruction Notice N-216 after cracking was found in service. \n\nCompliance is required promptly (within 300 flight hours of 25 Jan 1988 or by 30 Jun 1988, whichever is sooner) and spares must be checked before installation to avoid loss of main-rotor drive and catastrophic failure."}},"importantCases":[],"_links":{"self":"/api/acts/ad-hu-269-91-main-transmission-pinion-assembly","history":"/api/acts/ad-hu-269-91-main-transmission-pinion-assembly/history","analysis":"/api/acts/ad-hu-269-91-main-transmission-pinion-assembly/analysis","conflicts":"/api/acts/ad-hu-269-91-main-transmission-pinion-assembly/conflicts","importantCases":"/api/acts/ad-hu-269-91-main-transmission-pinion-assembly/important-cases","documents":"/api/acts/ad-hu-269-91-main-transmission-pinion-assembly/documents"}}