{"id":"F2006B11375","name":"AD/MU-2/44 - Split Radio Bus","slug":"ad-mu-2-44-split-radio-bus","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":57276,"registerId":"commonwealth-F2006B11375-current","compilationNumber":null,"startDate":"2026-04-02","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/MU-2/44 - Split Radio Bus","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)  Mitsubishi MU-2 Series Aeroplanes\n\n \n\nAD/MU-2/44 Split Radio Bus 13/89\n\nApplicability: MU 2B25: S/N 239 through 273. MU 2B-30/35: S/N 505 through 599. Requirement:  Action IAW MHI MU 2 SB 069/24-006 in conjunction with AD/MU 2/43. Compliance:               Prior to 31 March 1990.\n\nBackground: This AD resulted from a request by the National Transportation Safety Board (US) who while investigating a number of fatal MU 2B accidents, concluded that pilots were becoming confused in the operation of the interrupt/disconnect switches for the electric pitch trim and autopilot systems.\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\n \n\n \n\n \n\n \n\n \n","sortOrder":0}],"analysis":{"flash_summary":{"complexity_score":3,"scope_assessment":{"changed":false,"description":"The AD’s scope, as stated in the instrument, targets specific MU-2 serial numbers and prescribes modification per a named service bulletin together with an existing AD. The text presents this as a response to the NTSB finding about pilot confusion (Background) and does not indicate any expansion or narrowing of the target population or obligations from what that stated intent implies (Applicability; Requirement; Compliance)."},"complexity_factors":["Narrow applicability tied to specific aircraft serial-number ranges (Applicability)","Mandated compliance with an external manufacturer service bulletin (MHI MU 2 SB 069/24-006) rather than detailed technical steps inside the AD (Requirement)","Conjoint requirement with a separate AD (AD/MU 2/43) increases coordination needs (Requirement)","Fixed compliance deadline resulting in scheduling pressure and potential downtime (Compliance)","Safety rationale based on an external investigation report (NTSB) rather than empirical detail in the AD (Background)"],"plain_english_summary":"What this instrument does\n\n- This is an Airworthiness Directive (AD) issued under the Civil Aviation Regulations schedule of ADs (header: PART 39 - 105) that requires specified Mitsubishi MU-2 series aeroplanes to be modified. (Header; Applicability; Requirement)\n\nWho it affects\n\n- Owners and operators of Mitsubishi MU-2B25 aeroplanes with serial numbers 239–273, and MU-2B-30/35 aeroplanes with serial numbers 505–599. (Applicability)\n\nWhat must be done, and when\n\n- The affected aircraft must be modified in accordance with Mitsubishi Heavy Industries (MHI) Service Bulletin MU 2 SB 069/24-006 and in conjunction with AD/MU 2/43. (Requirement)\n- The required work must be completed before 31 March 1990. (Compliance)\n\nWhy this was issued (official rationale)\n\n- The AD states it was prompted by a request from the U.S. National Transportation Safety Board after investigations of multiple fatal MU-2B accidents. The NTSB concluded that pilots were becoming confused by the interrupt/disconnect switches for the electric pitch trim and autopilot systems. The AD’s stated purpose is therefore to change the aircraft/system so that this confusion is reduced or removed. (Background)\n\nWho pays and who decides\n\n- The direct costs (labour, parts, downtime) fall to the owners/operators of aircraft in the listed serial-number ranges because they must carry out the service-bulletin work required by the AD. (Applicability; Requirement)\n- The AD is issued under the Civil Aviation Regulations schedule of airworthiness directives; the regulator (Civil Aviation Safety Authority as indicated in the header) sets the mandatory compliance requirement and date. (Header; Compliance)\n\nImplementation, incentives and trade-offs\n\n- The AD references a manufacturer service bulletin and another AD (AD/MU 2/43). Operators must source parts and qualified maintenance to perform the modification in the way the service bulletin specifies; this creates a measurable compliance burden (labour, parts cost, and aircraft downtime). (Requirement)\n- The stated safety benefit (reduced pilot confusion on interrupt/disconnect switches) is concentrated on the affected aircraft and their crews; the cost is concentrated on their owners/operators. (Applicability; Background)\n- The operation of maintenance organisations that service these aircraft may see increased demand for work from affected operators; conversely, operators face opportunity costs while aircraft are out of service. (Requirement; Compliance)\n- The AD fixes a compliance deadline, limiting operators’ discretion about timing; compliance is binary (completed or not by the date). (Compliance)\n\nPractical risks and implementation notes\n\n- The AD requires following a specific service bulletin; the safety outcome depends on that bulletin’s technical instructions and correct installation by qualified personnel. If the bulletin is unclear or parts are scarce, there is an implementation risk (delay or incorrect modification). (Requirement)\n- The AD must be read and applied together with AD/MU 2/43, so operators must coordinate both mandates when planning maintenance. Failure to recognise the conjoint requirement raises compliance risk. (Requirement)\n\nSource citations\n\n- Header: Civil Aviation Regulations schedule of Airworthiness Directives (PART 39 - 105).\n- Applicability: MU-2B25 S/N 239–273; MU-2B-30/35 S/N 505–599.\n- Requirement: Action in accordance with MHI MU 2 SB 069/24-006 in conjunction with AD/MU 2/43.\n- Compliance: Prior to 31 March 1990.\n- Background: NTSB request regarding pilot confusion with interrupt/disconnect switches for electric pitch trim and autopilot systems."},"kimi_summary":{"content_quality":"ok","complexity_score":2,"scope_assessment":{"changed":false,"description":"This is a discrete, targeted safety directive addressing a specific technical issue identified through accident investigation. It remains focused on its original purpose of preventing pilot confusion with electrical system switches."},"complexity_factors":["Very short document (approximately 200 words)","Only 2 defined applicability ranges (serial number ranges)","Single requirement referencing external technical document (service bulletin)","No nested conditional logic or exceptions","No cross-references to other legislation beyond one related AD","Straightforward compliance deadline with no alternative methods"],"plain_english_summary":"This is an **Airworthiness Directive (AD)** — essentially a mandatory safety order issued by Australia's Civil Aviation Safety Authority (CASA) for specific aircraft.\n\n**What it does:**\nIt requires owners/operators of certain **Mitsubishi MU-2 series aeroplanes** to modify their aircraft's electrical system to split the radio bus (a shared electrical circuit). This must be done following a specific manufacturer's service bulletin (MHI MU 2 SB 069/24-006) and in conjunction with another related directive (AD/MU 2/43).\n\n**Who it affects:**\n- **MU 2B25 models:** Serial numbers 239 through 273\n- **MU 2B-30/35 models:** Serial numbers 505 through 599\n\n**Why it matters:**\nThe US National Transportation Safety Board investigated several fatal crashes involving these aircraft and found pilots were getting confused by the interrupt/disconnect switches for the electric pitch trim and autopilot systems. This confusion could lead to loss of aircraft control. The modification helps prevent this by changing how the electrical system is configured, reducing the risk of pilot error in critical flight situations.\n\n**Compliance deadline:**\nThe work had to be completed before 31 March 1990."}},"importantCases":[],"_links":{"self":"/api/acts/ad-mu-2-44-split-radio-bus","history":"/api/acts/ad-mu-2-44-split-radio-bus/history","analysis":"/api/acts/ad-mu-2-44-split-radio-bus/analysis","conflicts":"/api/acts/ad-mu-2-44-split-radio-bus/conflicts","importantCases":"/api/acts/ad-mu-2-44-split-radio-bus/important-cases","documents":"/api/acts/ad-mu-2-44-split-radio-bus/documents"}}