{"id":"F2006B02137","name":"AD/AC/77 - Induction Air Elbow Duct - Replacement, Exhaust System - Inspection","slug":"ad-ac-77-induction-air-elbow-duct-replacement-exhaust-system-inspection","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":41367,"registerId":"commonwealth-F2006B02137-current","compilationNumber":null,"startDate":"2026-04-01","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/AC/77 - Induction Air Elbow Duct - Replacement, Exhaust System - Inspection","content":"---\nmeta-content-style-type: text/css\nmeta-content-type: application/xhtml+xml; charset=utf-8\nmeta-description: CASA Airworthiness Directive\nmeta-generator: Aspose.Words for .NET 22.10.0\nmeta-keywords: Issue 11/1982,Aircraft below 5700 kg,Twin Commander (Gulfstream/Rockwell/ Aerocommander 500, 600 and 700) Series Aeroplanes,Induction Air Elbow Duct - Replacement, Exhaust System - Inspection,77\ntitle: Airworthiness Directive - AD/AC/77 - Induction Air Elbow Duct - Replacement, Exhaust System - Inspection\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)  Twin Commander (Gulfstream/Rockwell/ Aerocommander 500, 600 and 700) Series Aeroplanes\n\n \n\n# AD/AC/77 Induction Air Elbow Duct - Replacement,\n\nExhaust System - Inspection Applicability: Model 685 with S/Nos. 12000 to 12043 and 12045 to 12066. Document:               Gulfstream American SB 192.\n\nCompliance: Within 100 hours’ time in service after 31 December 1982.\n\n# 11/82\n\n \n\nBackground: A combination of exhaust system leakage and displaced induction ducting may cause exhaust gases to enter the cockpit and cabin.\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":{"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 specific aircraft. It has not expanded beyond its original purpose of preventing carbon monoxide poisoning in Twin Commander Model 685 aircraft."},"complexity_factors":["Very short document (approximately 150 words of substantive content)","Only 1 defined applicability criterion (specific serial number range)","Single compliance deadline (100 hours time-in-service after fixed date)","No cross-references to other legislation or regulations beyond citation of parent regulation (CAR 1998 Part 39)","No conditional logic or exceptions","Simple two-part requirement (replacement + inspection)","References only one technical document (Gulfstream American Service Bulletin 192)"],"plain_english_summary":"This CASA Airworthiness Directive mandates owners/operators of certain Twin Commander twin‑engine aircraft (models 500/600/700 series, notably Model 685 serials 12000–12043 and 12045–12066) to replace the induction air elbow duct and inspect the exhaust for leaks within 100 flight hours after 31 December 1982. \n\nIt’s required because damaged or displaced ducting can allow deadly carbon monoxide into the cockpit/cabin; compliance is mandatory before further flight."},"flash_summary":{"complexity_score":3,"scope_assessment":{"changed":false,"description":"Scope remains focused on the listed Model 685 serial numbers and mandates replacement/inspection per Gulfstream American SB 192 within the stated 100-hour compliance period; it does not expand beyond those aircraft or actions."},"complexity_factors":["Narrow applicability — specific to Model 685 serial numbers (Applicability).","Clear, short compliance window (100 hours after 31 Dec 1982) reduces scheduling ambiguity (Compliance).","Dependence on an external manufacturer document for technical instructions (Gulfstream American SB 192) — requires consulting the SB for details (Document).","Safety-critical operational consequence framed in the Background (risk of exhaust gases entering cockpit/cabin) increases urgency but not regulatory complexity.","The AD states required actions but omits detailed procedures in the text, so maintainers must interpret/implement per the referenced service bulletin."],"plain_english_summary":"**What it does:** Requires owners/operators of Twin Commander Model 685 aeroplanes (S/N 12000–12043 and 12045–12066) to replace the induction air elbow duct and inspect the exhaust system in accordance with Gulfstream American SB 192. Compliance must occur within 100 hours’ time in service after 31 December 1982.  \n\n**Who pays and why it matters:** Operators must arrange and fund the work. The directive targets a risk that exhaust leakage plus displaced induction ducting could allow exhaust gases into the cockpit and cabin (Background)."}},"importantCases":[],"_links":{"self":"/api/acts/ad-ac-77-induction-air-elbow-duct-replacement-exhaust-system-inspection","history":"/api/acts/ad-ac-77-induction-air-elbow-duct-replacement-exhaust-system-inspection/history","analysis":"/api/acts/ad-ac-77-induction-air-elbow-duct-replacement-exhaust-system-inspection/analysis","conflicts":"/api/acts/ad-ac-77-induction-air-elbow-duct-replacement-exhaust-system-inspection/conflicts","importantCases":"/api/acts/ad-ac-77-induction-air-elbow-duct-replacement-exhaust-system-inspection/important-cases","documents":"/api/acts/ad-ac-77-induction-air-elbow-duct-replacement-exhaust-system-inspection/documents"}}