{"id":"F2006B08462","name":"AD/CF6/18 - High Pressure Turbine Inspection and Improved Shroud Cooling","slug":"ad-cf6-18-high-pressure-turbine-inspection-and-improved-shroud-cooling","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":51108,"registerId":"commonwealth-F2006B08462-current","compilationNumber":null,"startDate":"2026-04-02","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/CF6/18 - High Pressure Turbine Inspection and Improved Shroud Cooling","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/CF6/18 High Pressure Turbine Inspection and Improved Shroud Cooling\n\nApplicability: All model CF6-80C2, A5, B6, B6 F and DIF.\n\n \n\nRequirement: Carry out the technical requirements of FAA AD 91-05-21 Amdt 39-6900.\n\n# 6/91\n\n \n\nCompliance: As detailed in Requirement Document with a revised effective date of 13 June 1991.\n\n \n\nBackground:  The AD introduces a borescope inspection program to detect high pressure turbine (HPT) stage 1 shroud and blade distress. Also, it requires installation of improved HPT hardware which increases the cooling to the HPT stage 1 shroud. The AD is prompted by one HPT failure which resulted in aircraft damage.\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":4,"scope_assessment":{"changed":false,"description":"The instrument adopts the technical requirements of FAA AD 91-05-21 for the specified CF6 engine models and sets an effective compliance date (Requirement; Compliance). The source text does not indicate any expansion or narrowing of scope relative to the FAA AD or any additional national variations; therefore there is no evident change of scope from the stated technical mandate in the instrument itself (Applicability; Requirement; Background)."},"complexity_factors":["Incorporation by reference of an external technical document (FAA AD 91-05-21) so the substantive technical requirements and intervals are not reproduced in the instrument (Requirement).","Technical subject matter (HPT stage 1 shroud and blade inspection and cooling hardware) requiring specialist maintenance skills and equipment (Background).","Narrow and well‑defined applicability (specific CF6 models) which reduces population‑level complexity but concentrates obligations on a defined operator group (Applicability).","Compliance timing delegated to a Requirement Document with a revised effective date (13 June 1991), creating a need to consult that document for precise deadlines (Compliance).","Limited text in the instrument about who may perform required work or how costs are allocated, requiring operational interpretation by operators and maintainers (Requirement; Compliance)."],"plain_english_summary":"What this instrument does (mechanically)\n\n- It requires operators of certain General Electric CF6 engines to perform inspections and to fit upgraded hardware. The instrument tells those operators to follow the technical requirements of FAA Airworthiness Directive 91-05-21 Amendment 39-6900 (\"the FAA AD\") (Requirement). It sets the effective compliance timetable in the Requirement Document with a revised effective date of 13 June 1991 (Compliance).\n\nWho it applies to\n\n- All CF6-80C2, A5, B6, B6F and DIF engines (Applicability).\n\nWhy it was introduced (as stated in the text)\n\n- The text states the measure was prompted by one high pressure turbine (HPT) failure that caused aircraft damage. The FAA AD it adopts introduces a borescope inspection programme to detect stage 1 HPT shroud and blade distress and requires installation of improved HPT hardware to increase cooling of the stage 1 shroud (Background).\n\nHow it changes behaviour, who pays, and who decides\n\n- Who decides: The Civil Aviation Safety Authority requires compliance by adopting the FAA AD technical requirements (Requirement).\n- Who pays: Operators of the listed CF6 models must carry out inspections and install upgraded HPT hardware. Those actions typically incur costs for labour, tooling, parts and any associated aircraft downtime; the instrument itself does not allocate funding (Applicability; Requirement).\n- Behaviour changes: Operators must implement a borescope inspection programme and install improved HPT cooling hardware as specified in the FAA AD. That will produce recurring inspection activity and one-time or periodic hardware modifications (Background; Requirement).\n\nCompliance burden and discretion\n\n- Compliance burden: The AD binds operators to the technical steps in the FAA AD and to the compliance timetable in the Requirement Document (Compliance; Requirement). The text does not specify who must perform the work (e.g. airline maintenance staff or independent MROs) nor the detailed inspection intervals in this instrument — those details reside in the FAA AD and the Requirement Document (Requirement; Compliance).\n- Bureaucratic discretion: This instrument directs adherence to an external FAA AD rather than setting detailed technical rules itself, so the practical technical content and intervals are determined by the referenced FAA document (Requirement). The instrument does not specify additional national variations or exemptions in the text provided.\n\nTrade-offs, incentives and implementation risks (source‑grounded)\n\n- The stated intended effect is improved detection of HPT damage and increased cooling of the stage 1 shroud, which addresses the particular failure that prompted the AD (Background). Achieving that requires inspections and hardware changes that impose costs and aircraft downtime on operators (Applicability; Requirement).\n- Implementation risk: The AD’s technical obligations depend on an external document (FAA AD 91-05-21). That creates a dependency on that document for technical detail and intervals; the instrument itself does not reproduce those details (Requirement; Compliance).\n- Market effects: The instrument makes compliance actions (inspections and hardware installation) mandatory for operators of the listed engine models. The text does not limit who may perform the required work, so in the absence of additional direction the practical effect on which service providers can compete to perform the work is not specified here (Requirement).\n\nNet practical summary\n\n- If you operate aircraft powered by the listed CF6 models, you must follow FAA AD 91-05-21’s technical requirements (borescope inspection programme and installation of improved HPT stage 1 shroud cooling hardware) on the timetable set out in the Requirement Document with effective date 13 June 1991. The directive was issued after an HPT failure that caused aircraft damage and is designed to find shroud/blade distress and to improve shroud cooling (Background; Requirement; Compliance). The instrument delegates technical detail to the referenced FAA AD, and operators are responsible for the costs and operational steps to comply (Requirement; Compliance)."},"kimi_summary":{"content_quality":"ok","complexity_score":2,"scope_assessment":{"changed":false,"description":"This is a standard airworthiness directive maintaining its original narrow scope: mandating specific safety inspections and hardware modifications for a defined engine series. It has not expanded beyond this technical safety purpose."},"complexity_factors":["Extremely short document (under 200 words)","Only 2 substantive operative provisions: applicability and requirement","No defined terms section — relies entirely on external FAA document for technical specifications","No conditional logic, exceptions, or nested provisions","Single cross-reference to external FAA directive rather than internal legislative structure","Minimal background section with plain language explanation"],"plain_english_summary":"This is an **Airworthiness Directive (AD)** issued by Australia's Civil Aviation Safety Authority (CASA) that applies to specific General Electric CF6 jet engines used in aircraft.\n\n**What it does:**\n- Requires airlines and aircraft operators to inspect the **High Pressure Turbine (HPT)** — a critical engine component — using a special camera called a **borescope** (a flexible tube with a camera that lets mechanics look inside engines without taking them apart)\n- Mandates installation of upgraded hardware that provides better cooling to prevent overheating of the turbine shroud (a protective ring around the turbine blades)\n\n**Who it affects:**\n- Owners and operators of aircraft with **CF6-80C2, A5, B6, B6F and D1F model engines** — these are commonly used on wide-body aircraft like Boeing 747s and 767s, and Airbus A300s and A310s\n- Maintenance organisations servicing these engines\n\n**Why it matters:**\n- This directive was triggered by an actual engine failure that damaged an aircraft\n- The inspections and hardware upgrades prevent catastrophic engine failures that could endanger passengers and crew\n- Operators must comply by the specified date (13 June 1991 for this revised version)\n\n**How it works:**\nRather than rewriting all the technical requirements, CASA simply adopts the American **FAA AD 91-05-21** — a common practice where Australia recognises equivalent safety standards from the United States Federal Aviation Administration."}},"importantCases":[],"_links":{"self":"/api/acts/ad-cf6-18-high-pressure-turbine-inspection-and-improved-shroud-cooling","history":"/api/acts/ad-cf6-18-high-pressure-turbine-inspection-and-improved-shroud-cooling/history","analysis":"/api/acts/ad-cf6-18-high-pressure-turbine-inspection-and-improved-shroud-cooling/analysis","conflicts":"/api/acts/ad-cf6-18-high-pressure-turbine-inspection-and-improved-shroud-cooling/conflicts","importantCases":"/api/acts/ad-cf6-18-high-pressure-turbine-inspection-and-improved-shroud-cooling/important-cases","documents":"/api/acts/ad-cf6-18-high-pressure-turbine-inspection-and-improved-shroud-cooling/documents"}}