{"id":"F2006B08465","name":"AD/CF6/21 - Eddy Current Inspection of High Pressure Turbine Thermal Shields","slug":"ad-cf6-21-eddy-current-inspection-of-high-pressure-turbine-thermal-shields","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":51116,"registerId":"commonwealth-F2006B08465-current","compilationNumber":null,"startDate":"2026-04-02","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/CF6/21 - Eddy Current Inspection of High Pressure Turbine Thermal Shields","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 - 106 CIVIL AVIATION SAFETY AUTHORITY\n\nSCHEDULE OF AIRWORTHINESS DIRECTIVES\n\n \n\n![](image.001.png)  General Electric Turbine Engines - CF6 Series\n\n \n\n# AD/CF6/21 Eddy Current Inspection of High Pressure\n\nTurbine Thermal Shields\n\nApplicability: CF6-45/-50 series engines.\n\n# 11/91\n\n \n\nRequirement: Action in accordance with the Technical Requirements of FAA AD 91-15-16, Amendment 39-7080.\n\nNote: General Electric Service Bulletin 72-879 Revision 6 refers.\n\nCompliance: As specified in the Requirement Document with an effective date of 28 November 1991.\n\n \n\nBackground: Four HPT stage one discs have been found cracked during inspection. The condition, if not corrected could result in uncontained engine failure.\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 AD implements the inspection requirement for CF6-45/-50 engines by adopting the FAA AD's technical requirements and refers to the GE service bulletin. The directive's scope (engines affected and inspection mandate) aligns with the stated safety problem (cracked HPT stage one discs) and does not indicate a change from that stated intent."},"complexity_factors":["Cross-reference to external technical documents (FAA AD 91-15-16 and GE Service Bulletin 72-879 Rev 6) which must be consulted for procedural detail","Technical nature of inspections (eddy-current testing) requiring specialised skills and equipment","Safety-critical consequences (risk of uncontained engine failure) raising enforcement and documentation requirements","Operational impacts: potential engine removal, downtime, and parts replacement if defects are found","Regulatory layering: CASA AD enforces requirements set out in a foreign authority's AD, creating reliance on externally maintained documents"],"plain_english_summary":"This AD requires operators of GE CF6‑45 and CF6‑50 engines to perform eddy‑current inspections of high‑pressure turbine thermal shields per FAA AD 91‑15‑16 and GE Service Bulletin 72‑879 Rev 6 (effective 28 Nov 1991). It responds to cracked HPT stage‑one discs and aims to prevent uncontained engine failure; operators must schedule inspections and bear inspection, downtime, and repair costs."},"kimi_summary":{"content_quality":"ok","complexity_score":2,"scope_assessment":{"changed":false,"description":"This is a discrete, single-issue safety directive focused specifically on eddy current inspection of HPT thermal shields in CF6 engines. It has not expanded beyond its original purpose."},"complexity_factors":["Very short document (under 200 words)","Only 1 defined applicability (CF6-45/-50 series engines)","Single requirement referencing external technical document (FAA AD 91-15-16)","No nested conditions, exceptions, or cross-references within the instrument itself","Background provided in plain language","Compliance date is absolute (no conditional triggers)"],"plain_english_summary":"This is an **Airworthiness Directive (AD)** — essentially a mandatory safety order issued by Australia's Civil Aviation Safety Authority (CASA).\n\n**What it does:**\nIt requires owners and operators of specific General Electric jet engines (the CF6-45 and CF6-50 series, commonly used on aircraft like the Boeing 747 and DC-10) to perform a specialised safety inspection called an **\"eddy current inspection\"** on a particular engine component — the **High Pressure Turbine (HPT) thermal shields**.\n\n**Why it matters:**\nFour of these engine discs were found cracked during routine checks. If left undetected, these cracks could cause the engine to break apart during flight — what's called an \"uncontained engine failure.\" This is extremely dangerous because flying debris can damage the aircraft or injure passengers.\n\n**Who must comply:**\nAnyone operating aircraft with these specific CF6 engine models in Australia.\n\n**What they must do:**\nFollow the technical instructions in an American safety order (FAA AD 91-15-16) and a General Electric service bulletin. The inspection had to be completed by 28 November 1991."}},"importantCases":[],"_links":{"self":"/api/acts/ad-cf6-21-eddy-current-inspection-of-high-pressure-turbine-thermal-shields","history":"/api/acts/ad-cf6-21-eddy-current-inspection-of-high-pressure-turbine-thermal-shields/history","analysis":"/api/acts/ad-cf6-21-eddy-current-inspection-of-high-pressure-turbine-thermal-shields/analysis","conflicts":"/api/acts/ad-cf6-21-eddy-current-inspection-of-high-pressure-turbine-thermal-shields/conflicts","importantCases":"/api/acts/ad-cf6-21-eddy-current-inspection-of-high-pressure-turbine-thermal-shields/important-cases","documents":"/api/acts/ad-cf6-21-eddy-current-inspection-of-high-pressure-turbine-thermal-shields/documents"}}