{"id":"F2006B06474","name":"AD/R44/6 - Main Rotor Gearbox","slug":"ad-r44-6-main-rotor-gearbox","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":47978,"registerId":"commonwealth-F2006B06474-current","compilationNumber":null,"startDate":"2026-04-02","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/R44/6 - Main Rotor Gearbox","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)  \nRobinson R44 Series Helicopters\n\nAD/R44/6 Main Rotor Gearbox 12/96 DM\n\nApplicability: This Directive is applicable to all R44 helicopters with S/N 0001 through 0232 fitted with main rotor gearbox P/N C006-1 Revision A through P. Helicopters S/N 0019, 0067, 0118, 0135 and 0215 are already in compliance with this Directive.\n\nRequirement: Unless previously carried out, action in accordance with Robinson R44 SB No 15 dated 2 August 1996. Report any fretting or loose bolts by MDR action.\n\nNote: FAA Priority Letter AD 96-18-22 refers.\n\nCompliance: Within 100 hours time in service from 11 September 1996 or prior to 1 October 1996, whichever occurs first.\n\nBackground: An overseas inflight failure of a main rotor gearbox has been reported. Inspection of the gearbox revealed that the 18 bolts securing the ring gear, P/N C146-3, to the gear carrier, P/N C268-2, had lost clamping torque which then resulted in fretting and failure of the gear carrier.","sortOrder":0}],"analysis":{"flash_summary":{"complexity_score":3,"scope_assessment":{"changed":false,"description":"The directive's scope remains targeted to the set of R44 helicopters (S/N 0001–0232) fitted with the specified main rotor gearbox part numbers and revisions. The instrument imposes a compulsory inspection/rectification and reporting obligation for those aircraft; it does not expand coverage beyond that defined group and excludes five serial numbers already stated as compliant. (Applicability; Requirement)"},"complexity_factors":["Narrow, well-defined applicability by serial number range and specific part numbers/revisions (lowers complexity). (Applicability)","Dependence on an external technical document (Robinson R44 Service Bulletin No. 15) for the exact work instructions (adds moderate complexity). (Requirement)","Short, fixed compliance window (100 hours TIS or a calendar date) increases urgency and operational coordination complexity. (Compliance)","Mandatory reporting of findings (MDR) creates administrative steps beyond the physical inspection. (Requirement)","Cross-reference to an FAA priority letter as additional context (minor additional cross-jurisdictional complexity). (Note)"],"plain_english_summary":"What this directive does (mechanics)\n\n- Requires owners/operators of certain Robinson R44 helicopters (serial numbers 0001–0232) fitted with main rotor gearbox P/N C006-1 Revision A through P to carry out the maintenance action described in Robinson R44 Service Bulletin No. 15 (dated 2 August 1996). (Applicability; Requirement)\n- Requires reporting any fretting or loose bolts found to the regulator via mandatory defect reporting (MDR) procedures. (Requirement)\n- Sets a mandatory compliance window: the work must be done within 100 hours time-in-service from 11 September 1996 or before 1 October 1996, whichever comes first. (Compliance)\n\nWhy it was issued (stated reason)\n\n- The directive was issued after an overseas in-flight failure of a main rotor gearbox. Inspection showed the 18 bolts that secure the ring gear (P/N C146-3) to the gear carrier (P/N C268-2) had lost clamping torque, which led to fretting and failure of the gear carrier. The directive implements the inspection/rectification steps set out in the manufacturer service bulletin to address that problem. (Background; Requirement)\n\nWho is affected and who pays\n\n- Affected parties: owners/operators of R44 helicopters S/N 0001–0232 that have the listed gearbox part numbers and revisions. Five listed helicopters (S/N 0019, 0067, 0118, 0135 and 0215) are noted as already being in compliance and so do not need further action. (Applicability)\n- Financial cost falls on the aircraft owners/operators. They must arrange the inspection/rectification called for in the service bulletin and pay for parts, labour and any downtime. (Requirement; Compliance)\n\nImplementation, decision points and reporting\n\n- The required technical steps are those in Robinson R44 Service Bulletin No. 15; the operator or their nominated maintenance provider decides how to carry out the work in accordance with that bulletin. (Requirement)\n- Operators must report findings of fretting or loose bolts to the regulator via MDR action, creating an explicit reporting obligation. (Requirement)\n- The directive cross-references an FAA priority letter (FAA Priority Letter AD 96-18-22), which may be used as additional guidance or context. (Note)\n\nPractical trade-offs, risks and behavioural effects (mechanics, not judgement)\n\n- Timing and availability: the short compliance window (100 hours TIS or before 1 October 1996) may require operators to prioritise affected helicopters for inspection and could cause temporary reductions in availability of those aircraft. (Compliance)\n- Parts and workshop capacity: operators may face queueing for parts or maintenance slots with authorised or independent providers; maintenance providers gain short-term demand for performing the SB work. (Requirement)\n- Reporting creates regulatory visibility: finding and reporting fretting or loose bolts increases regulator oversight of fleet defects, and may trigger further action depending on aggregated reports. (Requirement)\n- Safety objective vs. cost: the directive substitutes an immediate, mandatory inspection/rectification cost for the otherwise latent risk posed by potential bolt loosening; who bears that cost is the aircraft owner/operator. (Background; Requirement)\n\nScope and limits\n\n- The directive is narrowly targeted by serial number range and by specific gearbox part numbers and revisions; it does not mandate work on R44 helicopters outside that serial/P/N combination. (Applicability)\n\nSource citations: Applicability; Requirement; Compliance; Background; Note."},"kimi_summary":{"content_quality":"ok","complexity_score":2,"scope_assessment":{"changed":false,"description":"This is a discrete safety directive addressing a specific mechanical defect in specific aircraft. It has not expanded beyond its original purpose of mandating inspection and repair of the main rotor gearbox fault."},"complexity_factors":["Very short document (approximately 200 words)","Only 4 defined identifiers (serial number ranges, part numbers, service bulletin reference)","Single compliance pathway with clear deadline","No cross-references to other legislation beyond a note about related FAA directive","Simple conditional logic (applicability based on serial number and part number ranges, with explicit exemptions listed)"],"plain_english_summary":"This is an **Airworthiness Directive** — a mandatory safety order issued by Australia's Civil Aviation Safety Authority (CASA) for aircraft.\n\n**What it does:**\nOrders owners and operators of specific Robinson R44 helicopters to inspect their main rotor gearbox for a dangerous mechanical fault. The problem involves bolts that secure the ring gear to the gear carrier — if these bolts come loose, it causes \"fretting\" (wear from small movements between metal parts) and can lead to catastrophic gearbox failure.\n\n**Who it affects:**\n- Owners and operators of Robinson R44 helicopters with serial numbers 0001 through 0232\n- Specifically those fitted with main rotor gearbox part number C006-1, Revision A through P\n- Five specific helicopters (S/N 0019, 0067, 0118, 0135, and 0215) are already compliant and don't need to act\n\n**What must be done:**\n- Follow the instructions in **Robinson Service Bulletin No. 15** dated 2 August 1996\n- Check for loose bolts and fretting damage\n- Report any problems found through a Mandatory Defect Report (MDR)\n\n**When it must be done:**\nWithin 100 flight hours after 11 September 1996, or before 1 October 1996 — whichever comes first.\n\n**Why it matters:**\nAn overseas helicopter suffered an in-flight main rotor gearbox failure due to this exact defect. This directive prevents the same deadly failure from happening in Australian-registered aircraft. Non-compliance could result in loss of the aircraft and lives."}},"importantCases":[],"_links":{"self":"/api/acts/ad-r44-6-main-rotor-gearbox","history":"/api/acts/ad-r44-6-main-rotor-gearbox/history","analysis":"/api/acts/ad-r44-6-main-rotor-gearbox/analysis","conflicts":"/api/acts/ad-r44-6-main-rotor-gearbox/conflicts","importantCases":"/api/acts/ad-r44-6-main-rotor-gearbox/important-cases","documents":"/api/acts/ad-r44-6-main-rotor-gearbox/documents"}}