{"id":"F2006B11385","name":"AD/MU-2/55 - Emergency Gear Down Gearbox","slug":"ad-mu-2-55-emergency-gear-down-gearbox","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":57286,"registerId":"commonwealth-F2006B11385-current","compilationNumber":null,"startDate":"2026-04-02","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/MU-2/55 - Emergency Gear Down Gearbox","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-2/55 Emergency Gear Down Gearbox 8/94\n\nApplicability: All MU-2B-10, -15, -20, -25, -26 S/N 008 through 347, except S/N 313 and 321, MU-\n\n2B-30, -35 and -36 S/N 501 through 696, except S/N 652 and 661.\n\n \n\nRequirement: Action in accordance with Mitsubishi MU-2 Service Bulletin No 219.\n\n \n\nNote: JCAB AD TCD-3942-94 refers.\n\n \n\nCompliance: Unless previously carried out within 100 hours time in service from 31 July 1994.\n\n \n\nBackground: The manufacturer has advised that a lower pin of an emergency gear down gearbox has fallen out of the bracket housing.\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":2,"scope_assessment":{"changed":false,"description":"The AD defines a precise, time-limited requirement for specified MU-2 serial numbers to comply with Mitsubishi MU-2 Service Bulletin No. 219. The text supplied does not indicate any change to that scope or applicability; it sets the original applicability, required action, compliance window, and the factual background (Applicability; Requirement; Compliance; Background; Note)."},"complexity_factors":["Narrow applicability defined by specific models and serial-number ranges with a small number of stated exceptions (Applicability).","Mandate references an external technical document (Mitsubishi MU-2 Service Bulletin No. 219) rather than specifying technical steps in the AD itself (Requirement).","Time-limited compliance tied to a historical date and a flight-hour window (100 hours from 31 July 1994), requiring operators to calculate hours-in-service (Compliance).","No alternative methods, costs, or procedural details provided in the AD; compliance depends on interpreting and following the referenced service bulletin (Requirement).","Cross-reference to a foreign AD (JCAB AD TCD-3942-94) adds a layer of external context but does not change domestic mandate (Note)."],"plain_english_summary":"This AD requires owners/operators of specified Mitsubishi MU‑2 models/serial ranges to complete the corrective work in Mitsubishi MU‑2 Service Bulletin No. 219 within 100 flight hours from 31 July 1994 (unless already done). It was issued after a report that a lower pin fell from an emergency-gear-down gearbox; the AD mandates the manufacturer’s fix. Affected operators must obtain and follow SB219, bear parts/labor/downtime costs, and schedule the work to meet the compliance window."},"kimi_summary":{"content_quality":"ok","complexity_score":2,"scope_assessment":{"changed":false,"description":"This is a discrete, targeted safety directive addressing a specific mechanical defect in a specific aircraft type. It has not expanded beyond its original purpose of mandating inspection/repair of the emergency gear down gearbox pin issue."},"complexity_factors":["Single, specific mechanical defect addressed","Clear applicability list (specific models and serial numbers)","Single compliance action (follow Service Bulletin 219)","Simple time-based compliance deadline (100 hours from fixed date)","No nested exceptions or conditional logic","Cross-reference to only one external document (JCAB AD TCD-3942-94) and one manufacturer document","Extremely short (under 200 words of substantive content)"],"plain_english_summary":"This is an **Airworthiness Directive** (a mandatory safety order) issued by Australia's Civil Aviation Safety Authority for **Mitsubishi MU-2 series aeroplanes**.\n\n**What it does:**\n- Requires owners and operators of specific MU-2 aircraft to inspect or fix a problem with the **emergency gear down gearbox** — a backup system that lets pilots lower the landing gear manually if the normal system fails.\n\n**The safety problem:**\n- The manufacturer discovered that a **lower pin can fall out of the bracket housing** in this gearbox. If this happens, the emergency landing gear system might not work when needed — a serious safety risk during an emergency.\n\n**Who must comply:**\n- Owners/operators of specific MU-2B models with particular serial numbers (roughly 1980s-era aircraft). Some serial numbers are excluded from this directive.\n\n**What action is required:**\n- Follow the instructions in **Mitsubishi Service Bulletin No. 219** (the manufacturer's official repair notice).\n- Do this within **100 hours of flying time** after 31 July 1994, unless already done.\n\n**Why it matters:**\n- This prevents potential landing gear failures in emergencies. If your normal gear system fails and your backup doesn't work either, you're looking at a gear-up landing — expensive, dangerous, potentially fatal."}},"importantCases":[],"_links":{"self":"/api/acts/ad-mu-2-55-emergency-gear-down-gearbox","history":"/api/acts/ad-mu-2-55-emergency-gear-down-gearbox/history","analysis":"/api/acts/ad-mu-2-55-emergency-gear-down-gearbox/analysis","conflicts":"/api/acts/ad-mu-2-55-emergency-gear-down-gearbox/conflicts","importantCases":"/api/acts/ad-mu-2-55-emergency-gear-down-gearbox/important-cases","documents":"/api/acts/ad-mu-2-55-emergency-gear-down-gearbox/documents"}}