{"id":"F2006B10360","name":"AD/HILLER 12/34 Amdt 1 - Main Transmission Oil Filter","slug":"ad-hiller-12-34-amdt-1-main-transmission-oil-filter","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":115975,"registerId":"commonwealth-F2006B10360-current","compilationNumber":null,"startDate":"2026-04-03","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/HILLER 12/34 Amdt 1 - Main Transmission Oil Filter","content":"![](image.001.png)![](image.001.png)AIRWORTHINESS DIRECTIVE\n\n![](image.001.png)For the reasons set out in the background section, the CASA delegate whose signature appears below revokes Airworthiness Directive (AD) AD/HILLER 12/34 and issues the following AD under subregulation 39.1 (1) of CAR 1998. The AD requires that the action set out in the requirement section (being action that the delegate considers necessary to correct the unsafe condition) be taken in relation to the aircraft or aeronautical product mentioned in the applicability section: (a) in the circumstances mentioned in the requirement section; and (b) in accordance with the instructions set out in the requirement section; and (c) at the time mentioned in the compliance section.\n\nHiller UH-12 Series Helicopters\n\nAD/HILLER 12/34\n\nAmdt 1\n\n  \nMain Transmission Oil Filter 4/2002\n\nApplicability: All UH-12 series helicopters, including Soloy Conversions, incorporating a main transmission part number (P/N) 23500-3, 237700-3, -5, -7, -9, -21 and –23.\n\nRequirement: Inspect the main transmission oil filter and if applicable, the magnetic particle chip detector, in accordance with Hiller Aviation Service Bulletin UH-12-23-2.\n\nNote: FAA Airworthiness Directive 81-17-03 refers.\n\nCompliance: 1. Main transmissions not incorporating Rogerson Hiller Corporation Service Bulletin UH-12-23-3: Unless previously accomplished; within 25 hours’ time in service after this Directive is effective and thereafter at intervals not to exceed:\n\n    Piston engine helicopters: 55 hours.\n\n    b. Turbine engine helicopters: 27.5 hours.\n\n    2. Main transmissions incorporating Rogerson Hiller Corporation Service Bulletin UH-12-23-3: Unless previously accomplished, within 25 hours’ time in service after this Directive is effective and thereafter at intervals not to exceed:\n\n    Piston engine helicopters: 110 hours.\n\n    b. Turbine engine helicopters: 55 hours.\n\nThis Amendment becomes effective on 18 April 2002.\n\nHiller UH-12 Series Helicopters\n\nAD/HILLER 12/34 Amdt 1 (continued)\n\nBackground: This Directive was originally issued to require monitoring of the main transmission oil filter. The requirement was in response to reports of extensive wear in the planetary assemblies. This amendment introduces extended compliance intervals for helicopters incorporating a modified main transmission and provides an extended compliance to assist maintenance scheduling..\n\n![](image.002.png)  \n\nEugene Paul Holzapfel\n\nDelegate of the Civil Aviation Safety Authority 10 March 2002","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"},"flash_summary":{"complexity_score":3,"scope_assessment":{"changed":true,"description":"The amendment modifies compliance intervals rather than broadening aircraft applicability: it keeps the same UH‑12 applicability but introduces extended recurring inspection intervals for main transmissions that incorporate the Rogerson modification and gives an initial 25‑hour deadline (Background; Compliance). This reduces inspection frequency for modified transmissions (lowering operator maintenance burden) while maintaining inspection requirements for unmodified units, shifting incentives toward incorporating the Rogerson modification if operationally feasible."},"complexity_factors":["Multiple applicability criteria by part number (P/N 23500-3, 237700-3, -5, -7, -9, -21 and -23) (Applicability).","Different compliance tracks depending on whether Rogerson Hiller Corp Service Bulletin UH-12-23-3 has been incorporated (Compliance 1 vs 2).","Separate recurring intervals for piston versus turbine engine helicopters (Compliance 1 & 2).","Initial short-term compliance requirement (within 25 hours’ time in service) plus ongoing intervals (Compliance).","Requirement cross-references an external service bulletin for inspection instructions (Requirement: Hiller Aviation Service Bulletin UH-12-23-2).","Optional component 'if applicable' (magnetic particle chip detector) introduces factual determination by maintainer (Requirement).","Revocation and replacement of a prior AD creates an administrative change that operators must track (opening paragraph / Background)."],"plain_english_summary":"This Airworthiness Directive requires owners/operators of Hiller UH‑12 series helicopters (specific main transmission part numbers) to inspect the main transmission oil filter and, if fitted, the magnetic particle chip detector in line with Hiller Aviation Service Bulletin UH‑12‑23‑2. It sets an initial 25 hours’ time‑in‑service deadline and recurring inspection intervals, and lengthens those intervals for helicopters that incorporate a Rogerson-modified main transmission. Operators pay inspection labour/time and any follow‑on maintenance; the regulator enforces compliance and sets the inspection schedule."},"kimi_summary":{"content_quality":"ok","complexity_score":3,"scope_assessment":{"changed":false,"description":"This amendment stays within the original scope of the AD. It modifies only the compliance intervals (extending them for modified transmissions) without expanding the affected aircraft population or introducing new types of requirements. The core safety purpose — monitoring transmission oil filters for planetary gear wear — remains unchanged."},"complexity_factors":["Multiple conditional compliance paths based on engine type (piston vs turbine) and transmission modification status","Cross-reference to external technical documents (Hiller Service Bulletin UH-12-23-2 and Rogerson Hiller Corporation Service Bulletin UH-12-23-3)","Reference to US FAA Airworthiness Directive 81-17-03","Specific part number enumeration (7 variants) in applicability section","Nested time calculations: initial 25-hour window plus recurring intervals"],"plain_english_summary":"This AD requires owners/operators of Hiller UH-12 series helicopters (including Soloy conversions) to inspect the main transmission oil filter—and the magnetic chip detector where fitted—on a mandated initial and recurring schedule to detect early planetary-gear wear and prevent catastrophic main-rotor seizure. \n\nAn amendment extends inspection intervals for helicopters with the upgraded transmission per the service bulletin, reducing maintenance burden while maintaining safety."}},"importantCases":[],"_links":{"self":"/api/acts/ad-hiller-12-34-amdt-1-main-transmission-oil-filter","history":"/api/acts/ad-hiller-12-34-amdt-1-main-transmission-oil-filter/history","analysis":"/api/acts/ad-hiller-12-34-amdt-1-main-transmission-oil-filter/analysis","conflicts":"/api/acts/ad-hiller-12-34-amdt-1-main-transmission-oil-filter/conflicts","importantCases":"/api/acts/ad-hiller-12-34-amdt-1-main-transmission-oil-filter/important-cases","documents":"/api/acts/ad-hiller-12-34-amdt-1-main-transmission-oil-filter/documents"}}