{"id":"F2006B08456","name":"AD/CF6/12 Amdt 2 - Turbine Mid Frame Aft Circumferential Weld","slug":"ad-cf6-12-amdt-2-turbine-mid-frame-aft-circumferential-weld","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":51093,"registerId":"commonwealth-F2006B08456-current","compilationNumber":null,"startDate":"2026-04-02","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/CF6/12 Amdt 2 - Turbine Mid Frame Aft Circumferential Weld","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)  \nGeneral Electric Turbine Engines \\- CF6 Series\n\nAD/CF6/12\n\nAmdt 2\n\n  \nTurbine Mid Frame Aft Circumferential Weld 3/91\n\nApplicability: CF6-50/-45 series.\n\nRequirement: Action in accordance with the technical requirements of FAA AD 90-23-15 (Amdt 39-6754).\n\nNote: GE SB 72-957 Rev. 2 refers.\n\nCompliance: As specified in the Requirement Document.\n\nBackground: The AD was initially raised to mandate the requirements of GE 72-957 which introduced inspections to insure against conditions which could release hot air into the core cowl cavity. Two such events resulted in take-off aborts due to fire warning indications.\n\nThis amendment is raised to update the requirement in accordance with the FAA AD incorporating the latest revision of the manufacturer’s SB covering the problem. It extends inspection intervals for certain engines on the basis of service experience.","sortOrder":0}],"analysis":{"flash_summary":{"complexity_score":4,"scope_assessment":{"changed":true,"description":"The amendment updates the mandated technical reference to align with FAA AD 90-23-15 incorporating the latest revision of GE Service Bulletin 72-957 (Note; Requirement) and, on the basis of service experience, extends inspection intervals for certain engines (Background). Thus the practical scope changed from the original AD by changing the required reference version and by lengthening inspection intervals for some engines."},"complexity_factors":["References external mandatory documents (FAA AD 90-23-15 and GE SB 72-957 Rev. 2) rather than reproducing technical steps, requiring access to and interpretation of those documents (Requirement; Note).","Compliance actions depend on service-history-based distinctions (some engines have extended intervals), so operators must determine which interval applies to each engine (Background).","Operational impact varies by operator: inspections can require downtime, labour and parts costs; scheduling and record-keeping burdens fall on maintenance organisations (Applicability; Requirement; Compliance).","Safety trade-off: balancing inspection frequency against operational cost relies on manufacturer/FAA judgment and service data, creating moderate risk if implementation or data interpretation is incorrect (Background).","Enforcement and responsibility are split: CASA mandates the AD, FAA AD sets technical requirements, and GE supplies the service bulletin, requiring coordination across documents and organisations (Requirement; Note)."],"plain_english_summary":"This amendment makes inspections and any required follow-up actions mandatory for GE CF6-50 and CF6-45 engines’ turbine mid‑frame aft circumferential weld by requiring compliance with FAA AD 90‑23‑15 and the referenced GE Service Bulletin, affecting operators, engine owners and maintenance organisations. It matters because previous weld failures triggered fire warnings and aborted takeoffs; the rule updates the mandated technical reference and (for some engines) extends inspection intervals based on service experience, shifting inspection costs and scheduling to operators."},"kimi_summary":{"content_quality":"ok","complexity_score":3,"scope_assessment":{"changed":false,"description":"The amendment remains tightly scoped to its original purpose: ensuring the structural integrity of a specific engine weld. The only change is procedural — adopting updated manufacturer guidance and extending inspection intervals based on service experience. This is a routine technical update, not scope creep."},"complexity_factors":["Very short document (under 300 words)","Only 1 defined applicability criterion (engine series)","Single cross-reference to FAA AD 90-23-15 and manufacturer Service Bulletin 72-957 Rev. 2","No nested conditional logic or exceptions within the text itself — compliance delegated entirely to external technical documents","Background section provides clear safety rationale in plain language"],"plain_english_summary":"This is an **Airworthiness Directive** (AD) — essentially a mandatory safety order issued by Australia's Civil Aviation Safety Authority (CASA) for aircraft engines.\n\n**What it does:**\nThis directive requires owners and operators of **General Electric CF6-50 and CF6-45 series turbine engines** to perform specific safety inspections on a particular weld in the engine's turbine section (the \"mid frame aft circumferential weld\").\n\n**Why it matters:**\n- **The safety risk:** Cracks or failures in this weld can allow hot air to leak into the engine's outer casing (the \"core cowl cavity\"), which has previously caused fire warnings and forced pilots to abort take-offs.\n- **The fix:** Operators must follow inspection procedures originally developed by the engine manufacturer (General Electric) and now mandated by the US Federal Aviation Administration (FAA AD 90-23-15).\n\n**What's new in this version (Amendment 2):**\n- Updates the requirements to match the latest manufacturer guidance (Service Bulletin 72-957, Revision 2)\n- **Extends inspection intervals** for certain engines based on real-world service data — meaning some operators can wait longer between checks if their engines meet specific criteria\n\n**Who must comply:**\nAnyone operating aircraft with CF6-50 or CF6-45 engines in Australia — this includes airlines, cargo operators, and private owners."}},"importantCases":[],"_links":{"self":"/api/acts/ad-cf6-12-amdt-2-turbine-mid-frame-aft-circumferential-weld","history":"/api/acts/ad-cf6-12-amdt-2-turbine-mid-frame-aft-circumferential-weld/history","analysis":"/api/acts/ad-cf6-12-amdt-2-turbine-mid-frame-aft-circumferential-weld/analysis","conflicts":"/api/acts/ad-cf6-12-amdt-2-turbine-mid-frame-aft-circumferential-weld/conflicts","importantCases":"/api/acts/ad-cf6-12-amdt-2-turbine-mid-frame-aft-circumferential-weld/important-cases","documents":"/api/acts/ad-cf6-12-amdt-2-turbine-mid-frame-aft-circumferential-weld/documents"}}