{"id":"F2006B07413","name":"AD/TFE 731/7 Amdt 2 - Turbine Interstage Transition Duct","slug":"ad-tfe-731-7-amdt-2-turbine-interstage-transition-duct","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":49650,"registerId":"commonwealth-F2006B07413-current","compilationNumber":null,"startDate":"2026-04-02","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/TFE 731/7 Amdt 2 - Turbine Interstage Transition Duct","content":"COMMONWEALTH OF AUSTRALIA (Civil Aviation Regulations 1998), PART 39 \\- 106 CIVIL AVIATION SAFETY AUTHORITY\n\nSCHEDULE OF AIRWORTHINESS DIRECTIVES\n\n![](image.001.png)  \nAlliedSignal (Garrett/AiResearch) Turbine Engines \\- TFE731 Series\n\nAD/TFE731/7\n\nAmdt 2\n\n  \nTurbine Interstage Transition Duct 11/87\n\nApplicability: TFE 731-2, \\-3, \\-3A, \\-3AR, \\-3B, \\-3BR and \\-3R engines whose serial numbers are detailed in the Requirement document.\n\nRequirement: Action in accordance with GTEC SB TFE-731-72-3159R6.\n\nCompliance: Unless already accomplished, at the next major periodic inspection or at the next access of affected part whichever occurs first after 30 June 1986.\n\nNote: Compliance with the previous issue of this Directive satisfies compliance with this amendment.\n\nBackground: This Directive is amended to reflect the manufacturers revision 6 of SB\n\nTFE 731-72-3159 which updates engine application and includes reference to FAA AD 81-24-08 which addresses this subject.","sortOrder":0}],"analysis":{"kimi_summary":{"content_quality":"ok","complexity_score":3,"scope_assessment":{"changed":false,"description":"This is a routine amendment to an existing airworthiness directive. The scope remains unchanged — it still addresses the same safety issue on the same engine models. The amendment simply updates the referenced technical document to the manufacturer's latest revision (R6) and acknowledges the corresponding FAA directive. This is standard maintenance of aviation safety orders, not scope creep."},"complexity_factors":["Short, single-purpose directive (approximately 150 words)","Only 2 defined references (the service bulletin and FAA AD)","Simple conditional logic: compliance required only if not already done, and only after a specific date","No nested exceptions or cross-references to other legislation","Relies on external technical document (service bulletin) for actual procedural details, keeping the legislative text minimal"],"plain_english_summary":"**What this is:** This is an **Airworthiness Directive (AD)** — a mandatory safety order issued by Australia's Civil Aviation Safety Authority (CASA). Think of it as a \"recall notice\" for aircraft engines, but with legal force. Owners and operators must comply or the aircraft cannot legally fly.\n\n**What it does:** This AD requires inspection or replacement of a specific part — the **Turbine Interstage Transition Duct** — on certain AlliedSignal (formerly Garrett/AiResearch) TFE731 jet engines. These engines are commonly used in business jets like the Learjet, Falcon, and Citation aircraft.\n\n**Who it affects:** Anyone operating aircraft with TFE731-2, -3, -3A, -3AR, -3B, -3BR, or -3R engines whose serial numbers are listed in the manufacturer's service bulletin (a technical document referenced in the AD).\n\n**What must be done:** Operators must follow the instructions in **Service Bulletin TFE-731-72-3159 Revision 6** — a detailed technical document from the engine manufacturer. The work must be done by the next major inspection or the next time mechanics access the affected part, whichever comes first, but only if that happens after 30 June 1986.\n\n**Why it matters:** The Turbine Interstage Transition Duct sits between turbine stages in the hot section of the engine. If this part fails, it can cause catastrophic engine damage, potentially leading to engine failure in flight. This amendment updates the original directive to match the manufacturer's latest guidance (Revision 6 of their service bulletin) and references the corresponding US Federal Aviation Administration (FAA) safety order.\n\n**Key point:** If you already complied with the previous version of this directive, you're still compliant — you don't need to do the work again."},"flash_summary":{"complexity_score":2,"scope_assessment":{"changed":true,"description":"The amendment updates the AD to mirror the manufacturer’s revision 6 of service bulletin TFE-731-72-3159 (SB TFE-731-72-3159R6), which changes the engine application (the set of engines/serial numbers affected) and adds a reference to FAA AD 81-24-08. Practically, this alters which specific engines are captured by the AD (Applicability; Background) and directs operators to comply with the updated SB (Requirement)."},"complexity_factors":["Short, single-subject AD with a clear mandatory action (Requirement).","Relies on an external manufacturer service bulletin (GTEC SB TFE-731-72-3159R6) for technical details (Requirement) rather than containing them.","Applicability depends on engine serial numbers listed in a separate Requirement document, requiring cross-checking (Applicability).","Timing rule is conditional (next major periodic inspection or next access of affected part, whichever occurs first, after a specific date), which adds a scheduling consideration (Compliance).","Cross-reference to FAA AD 81-24-08 and the manufacturer’s SB revision increases the number of documents an operator must consult to be sure of full compliance (Background).","Provision that prior compliance satisfies the amendment reduces complexity for already-compliant operators but requires record-checking (Note)."],"plain_english_summary":"CASA requires operators of certain AlliedSignal TFE731 engines (only the serial numbers listed in the Requirement) to carry out mandatory work per GTEC SB TFE-731-72-3159R6 at the next major inspection or the next time the affected part is accessed after 30 June 1986. Operators or their maintenance providers pay inspection/repair costs; earlier compliant work satisfies this amendment."}},"importantCases":[],"_links":{"self":"/api/acts/ad-tfe-731-7-amdt-2-turbine-interstage-transition-duct","history":"/api/acts/ad-tfe-731-7-amdt-2-turbine-interstage-transition-duct/history","analysis":"/api/acts/ad-tfe-731-7-amdt-2-turbine-interstage-transition-duct/analysis","conflicts":"/api/acts/ad-tfe-731-7-amdt-2-turbine-interstage-transition-duct/conflicts","importantCases":"/api/acts/ad-tfe-731-7-amdt-2-turbine-interstage-transition-duct/important-cases","documents":"/api/acts/ad-tfe-731-7-amdt-2-turbine-interstage-transition-duct/documents"}}