{"id":"F2006B06026","name":"AD/PA-46/20 - Exhaust Transition Bolts","slug":"ad-pa-46-20-exhaust-transition-bolts","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":114424,"registerId":"commonwealth-F2006B06026-current","compilationNumber":null,"startDate":"2026-04-03","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/PA-46/20 - Exhaust Transition Bolts","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)  Piper PA-46 (Malibu) Series Aeroplanes\n\n \n\nAD/PA-46/20 Exhaust Transition Bolts 8/91 TX\n\nApplicability: All model PA-46-350P fitted with Textron Lycoming TI0-540-AE2A engine with engine S/No up to but not including L9161-61A and excluding S/No L9157-61A.\n\n \n\nRequirement: Action in accordance with the Technical Requirements of FAA AD 91-10-04 Amdt 39-6981.\n\n \n\nNote: Textron Lycoming SB No 491A refers.\n\n \n\nCompliance: Within 10 hours time in service from 31 May 1991.\n\n \n\nBackground: An aircraft accident has occurred caused by engine power loss, which resulted from exhaust transition flange bolt loss and flange separation.\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 instrument, as written, targets a specific subset of PA-46-350P aeroplanes by engine serial number and requires compliance with FAA AD 91-10-04 and Textron Lycoming SB No 491A within a short, specified time window. The text contains no indication that the directive changes or expands scope from an earlier version; it simply sets an immediate mandatory remedial action for the aircraft/engine serial numbers listed. (Applicability; Requirement; Compliance)"},"complexity_factors":["Narrow technical applicability (specific aircraft model and engine serial-number cutoffs)","Delegation of detailed technical procedure to external documents (FAA AD and Textron Lycoming SB)","Short compliance timeframe (10 hours TIS from a specified date)","Specialised subject matter (aircraft exhaust flange/bolt integrity) requiring technical maintenance work","A single-sentence background linking the directive to an accident increases operational urgency but provides little procedural detail in the instrument itself"],"plain_english_summary":"CASA requires owners/operators of a specific subset of Piper PA-46-350P aircraft (defined by Textron Lycoming engine serial numbers, with one exclusion) to carry out the technical actions set out in FAA AD 91-10-04 and Lycoming SB No. 491A. The work must be done within 10 hours TIS from 31 May 1991 to address reported exhaust transition flange bolt loss and prevent related engine power loss.\n\nAffected operators pay for inspections/repairs; CASA enforces compliance while the FAA and manufacturer provide the technical procedure."},"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 exhaust bolt failures in the identified Piper PA-46 models."},"complexity_factors":["Single, specific applicability clause targeting one aircraft model and specific engine serial number ranges","Single requirement referencing an external technical document (FAA AD) rather than spelling out detailed steps","Simple compliance deadline (10 hours time in service from fixed date)","No defined terms section, no cross-references to other legislation, no conditional logic or exceptions","Background provided in plain narrative form explaining the safety rationale","Total length is extremely short (under 200 words of substantive content)"],"plain_english_summary":"**What this is:** 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**Who it affects:** Owners and operators of **Piper PA-46-350P Malibu aeroplanes** fitted with a specific Textron Lycoming engine (TIO-540-AE2A) with serial numbers up to but not including L9161-61A, and excluding serial number L9157-61A.\n\n**What it requires:** These aircraft must follow the technical instructions in an American safety order (FAA AD 91-10-04 Amendment 39-6981). This involves inspecting or fixing the **exhaust transition bolts** — the bolts that hold together parts of the engine's exhaust system. There's also a reference to Textron Lycoming Service Bulletin 491A, which provides additional technical guidance.\n\n**When it had to be done:** Within 10 hours of flying time after 31 May 1991.\n\n**Why it matters:** An aircraft crashed because exhaust bolts came loose, causing the exhaust flange to separate and the engine to lose power. This directive prevents the same dangerous failure from happening again by forcing operators to check and fix these bolts before the problem causes another accident.\n\n**In short:** If you owned one of these specific Piper Malibu planes in 1991, CASA ordered you to inspect your exhaust bolts within 10 flight hours or risk your engine failing mid-flight."}},"importantCases":[],"_links":{"self":"/api/acts/ad-pa-46-20-exhaust-transition-bolts","history":"/api/acts/ad-pa-46-20-exhaust-transition-bolts/history","analysis":"/api/acts/ad-pa-46-20-exhaust-transition-bolts/analysis","conflicts":"/api/acts/ad-pa-46-20-exhaust-transition-bolts/conflicts","importantCases":"/api/acts/ad-pa-46-20-exhaust-transition-bolts/important-cases","documents":"/api/acts/ad-pa-46-20-exhaust-transition-bolts/documents"}}