{"id":"F2006B11379","name":"AD/MU-2/49 Amdt 1 - Underwing Pressure Bulkhead Flange","slug":"ad-mu-2-49-amdt-1-underwing-pressure-bulkhead-flange","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":57280,"registerId":"commonwealth-F2006B11379-current","compilationNumber":null,"startDate":"2026-04-02","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/MU-2/49 Amdt 1 - Underwing Pressure Bulkhead Flange","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\n# AD/MU-2/49\n\nAmdt 1\n\nApplicability: All Models.\n\n# Underwing Pressure Bulkhead Flange 10/94\n\n \n\nRequirement: Remove the necessary internal cabin lining and perform a close visual inspection of the underwing pressure bulkhead. Look for cracks in the bend radius of the flange on both left and right hand sides of the bulkhead from F.Sta.3905 to F.Sta.4660.\n\n \n\nCompliance: Prior to exceeding 5000 pressurised flights or prior to 11 October 1991, whichever occurs later. Thereafter at intervals not to exceed 1000 pressurised flights, and at any time there is an unexplained difficulty maintaining cabin pressure. The compliance of the initial issue of this Directive remains unchanged. This amendment is effective from 15 September 1994.\n\n \n\nBackground: There had been a report of a 300mm long crack in the bend radius of the pressure bulkhead flange on an Australian registered aircraft. Undetected cracking could cause a sudden loss of cabin pressure in flight. Amendment 1 is issued to specify the exact location of the area to be inspected in response to a reported misunderstanding in the field.\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":true,"description":"The amendment does not change who is covered or the inspection intervals but clarifies and specifies the exact area to be inspected (bend radius of the flange on both sides from F.Sta.3905 to F.Sta.4660). This resolves prior ambiguity about the inspection location without expanding the directive's compliance obligations."},"complexity_factors":["Applicability to all MU-2 models — broad but technically specific target.","Inspection location specified by fuselage station range (F.Sta.3905–4660) — requires technical familiarity with aircraft datum references.","Access burden: removal of internal cabin lining to reach the bulkhead flange (labor, downtime).","Recurring compliance tracking: counting pressurised flights (initial compliance before 5,000 pressurised flights, then every 1,000).","Unscheduled trigger: inspection required after any unexplained difficulty maintaining cabin pressure (operational monitoring and judgement).","Subjectivity of 'close visual inspection' — detection depends on inspector skill and judgement.","Amendment is a location clarification in response to field misunderstanding rather than a change to inspection frequency or scope of affected aircraft."],"plain_english_summary":"Requires owners/operators of all Mitsubishi MU-2 aeroplanes to remove internal cabin lining and do a close visual inspection of the underwing pressure bulkhead flange (left and right) in the bend radius between fuselage stations 3905–4660 for cracks. Initial inspection is required before exceeding 5,000 pressurised flights or by 11 October 1991, then every 1,000 pressurised flights and whenever there is an unexplained difficulty maintaining cabin pressure. The amendment cites a reported 300 mm crack and narrows the inspected area to resolve field misunderstanding."},"kimi_summary":{"content_quality":"ok","complexity_score":2,"scope_assessment":{"changed":false,"description":"This is Amendment 1 to an existing directive. The amendment is narrow and technical — it merely clarifies the exact location of the inspection area (F.Sta.3905 to F.Sta.4660) after field reports of misunderstanding. The core safety purpose and applicability remain unchanged from the original 1994 directive."},"complexity_factors":["Single, specific technical requirement (visual inspection of one component)","Clear compliance timeline with two triggers (flight hours/calendar date)","Only one defined technical term requiring explanation (F.Sta. = frame station, a reference point on the aircraft structure)","No cross-references to other legislation or regulations","Straightforward conditional logic (whichever occurs later, thereafter at intervals)","Background explanation included in document itself"],"plain_english_summary":"This CASA Airworthiness Directive requires operators of Mitsubishi MU-2 aeroplanes in Australia to remove cabin lining and visually inspect the underwing pressure bulkhead flange (bend radius) for cracks, after a 300mm crack was found. \n\nInspections must start by 5,000 pressurised flights (or by 11 Oct 1991 if later), repeat every 1,000 pressurised flights, and be done immediately if cabin pressure cannot be maintained. Amendment 1 clarifies the exact inspection area."},"flash_summary_failed":{"failed":true,"reason":"Unauthenticated. Configure AI_GATEWAY_API_KEY or use a provider module. Learn more: https://ai-sdk.dev/unauthenticated-ai-gateway","source":"analysis-cron"}},"importantCases":[],"_links":{"self":"/api/acts/ad-mu-2-49-amdt-1-underwing-pressure-bulkhead-flange","history":"/api/acts/ad-mu-2-49-amdt-1-underwing-pressure-bulkhead-flange/history","analysis":"/api/acts/ad-mu-2-49-amdt-1-underwing-pressure-bulkhead-flange/analysis","conflicts":"/api/acts/ad-mu-2-49-amdt-1-underwing-pressure-bulkhead-flange/conflicts","importantCases":"/api/acts/ad-mu-2-49-amdt-1-underwing-pressure-bulkhead-flange/important-cases","documents":"/api/acts/ad-mu-2-49-amdt-1-underwing-pressure-bulkhead-flange/documents"}}