{"id":"F2006B02561","name":"AD/ATF3/4 - High Pressure Turbine Disc Inspection","slug":"ad-atf3-4-high-pressure-turbine-disc-inspection","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":41817,"registerId":"commonwealth-F2006B02561-current","compilationNumber":null,"startDate":"2026-04-01","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/ATF3/4 - High Pressure Turbine Disc Inspection","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 \\- ATF3 Series\n\nAD/ATF3/4 High Pressure Turbine Disc Inspection 3/95\n\nApplicability: AlliedSignal Model ATF3-6 and \\-6A engines as detailed in AlliedSignal Alert Service Bulletin No. ATF3-A72-6184 Revision 1.\n\nRequirement: Inspect the high pressure turbine (HPT) disc in accordance with AlliedSignal Alert Service Bulletin No. ATF3-A72-6184 Revision 1.\n\nNote: FAA Airworthiness Directive 94-23-04 refers.\n\nCompliance: Effective 2 March 1995:\n\n    Engines with 1550 or more HPT disc cycles since new, within 50 cycles.\n\n    2. Engines with less than 1550 HPT disc cycles since new, within 300 cycles or prior to accumulating 1600 cycles since new, whichever occurs first.\n\nBackground: This Directive has been issued to require a once only inspection of the HPT disc curvic and bore area for cracks. The requirement follows reports of cracks being found in the subject discs during routine inspections.","sortOrder":0}],"analysis":{"kimi_summary":{"content_quality":"ok","complexity_score":2,"scope_assessment":{"changed":false,"description":"N/A — This is a discrete, single-issue airworthiness directive with no evidence of scope creep. It addresses one specific safety concern (HPT disc cracks) for one engine series with clear applicability limits."},"complexity_factors":["Single, specific mechanical component targeted (HPT disc)","Only two compliance pathways based on one variable (cycle count)","No defined terms section — relies on external technical document (AlliedSignal Service Bulletin)","No cross-references to other legislation beyond noting related FAA directive","Straightforward conditional logic (if/then based on cycle thresholds)","Single requirement with no exceptions, exemptions, or nested conditions"],"plain_english_summary":"This is an **Airworthiness Directive (AD)** — essentially a mandatory safety order for aircraft engines. It requires owners and operators of specific AlliedSignal (Garrett/AiResearch) ATF3-6 and ATF3-6A jet engines to inspect a critical part called the **high pressure turbine (HPT) disc** for cracks.\n\n**Who it affects:**\n- Anyone operating aircraft with these specific engine models\n- Maintenance organisations servicing these engines\n\n**What it requires:**\n- A **one-time inspection** of the HPT disc's \"curvic\" (a type of gear-like coupling) and bore (the central hole) areas\n- The inspection must follow the exact procedure in AlliedSignal's Alert Service Bulletin ATF3-A72-6184 Revision 1\n\n**When to comply:**\n- **High-use engines** (1,550+ cycles since new): inspect within 50 flight cycles\n- **Lower-use engines** (under 1,550 cycles): inspect within 300 cycles **or** before hitting 1,600 total cycles — whichever comes first\n\n**Why it matters:**\nCracks were found in these discs during routine maintenance. The HPT disc spins at extreme speeds and temperatures; if it fails, the engine could destroy itself and potentially damage the aircraft. This directive prevents catastrophic engine failure by catching cracks before they cause an accident.\n\n**Key point:** This isn't optional — it's legally enforceable under the Civil Aviation Regulations. Non-compliance means the aircraft cannot legally fly."},"flash_summary":{"complexity_score":2,"scope_assessment":{"changed":false,"description":"Based on the text provided, the directive imposes a once‑only inspection on specified engines and sets cycle‑based compliance windows. The instrument text does not indicate any change to that scope from an earlier or different stated intent; therefore there is no evidence in this text that the scope has been changed."},"complexity_factors":["Narrow applicability to specific engine models requiring identification of affected engines (Applicability).","Single, clearly defined technical action (one‑time inspection of HPT disc curvic and bore area) but the method is delegated to a manufacturer Alert Service Bulletin (Requirement).","Compliance tied to engine life measured in HPT disc cycles with two different timing windows (>=1550 cycles vs <1550 cycles), requiring accurate life‑cycle tracking (Compliance).","Dependence on an external technical document (AlliedSignal Alert Service Bulletin No. ATF3‑A72‑6184 Revision 1) for the inspection procedure increases operational complexity (Requirement).","Directive references another regulator’s AD (FAA) which may require cross‑checking related documents (Note).","The AD does not specify remedial actions within the text provided, creating potential operational ambiguity about next steps after inspection (Requirement, Background)."],"plain_english_summary":"This AD mandates a one‑time inspection of the high‑pressure turbine disc (curvic and bore area) on specified AlliedSignal ATF3‑6/6A engines, to be carried out per AlliedSignal Alert Service Bulletin ATF3‑A72‑6184 Rev 1, with cycle‑based deadlines.  \n\nIt affects owners/operators and their maintenance providers, who must schedule and pay for the inspection to address discovered disc cracks and ensure continued airworthiness."}},"importantCases":[],"_links":{"self":"/api/acts/ad-atf3-4-high-pressure-turbine-disc-inspection","history":"/api/acts/ad-atf3-4-high-pressure-turbine-disc-inspection/history","analysis":"/api/acts/ad-atf3-4-high-pressure-turbine-disc-inspection/analysis","conflicts":"/api/acts/ad-atf3-4-high-pressure-turbine-disc-inspection/conflicts","importantCases":"/api/acts/ad-atf3-4-high-pressure-turbine-disc-inspection/important-cases","documents":"/api/acts/ad-atf3-4-high-pressure-turbine-disc-inspection/documents"}}