{"id":"F2009L01977","name":"AD/ALF/21 - High Pressure Compressor Discs","slug":"ad-alf-21-high-pressure-compressor-discs","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":79186,"registerId":"commonwealth-F2009L01977-current","compilationNumber":null,"startDate":"2026-04-02","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"AlliedSignal (Lycoming) Turbine Engines ","sectionType":"division","heading":"AlliedSignal (Lycoming) Turbine Engines - ALF502 and LF507 Series","content":"### AlliedSignal (Lycoming) Turbine Engines - ALF502 and LF507 Series\n\n| AD/ALF/21 | High Pressure Compressor Discs | 6/2009 |\n| --------- | ------------------------------ | ------ |\n\n| Applicability: | Honeywell International Inc. ALF502L-2 and ALF502L-2C turbofan engines with high pressure compressor (HPC) first stage discs, part numbers (P/Ns) 2-101-331-03, 2-101-331-04, and 2-101-331-10, installed.Note 1: These engines are installed on, but not limited to, Bombardier CL-600-1A11 aeroplanes.                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                           |\n| -------------- | -------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |\n| Requirement:   | 1. For discs with 5,000 or more cycles-since-new on the effective date of this AD, perform a dimensional inspection of the HPC first stage disc to determine if excessive disc balance material was removed. See the following Figure 1 for limits.Limits for Removed Balance Material, DiscForward Flange Figure 1 (Sheet 1 of 2)Limits for Removed Balance Material, DiscForward Flange Figure 1 (Sheet 2 of 2)2. Replace the disc if excessive disc balance material was removed. See limits in Figure 1 of this AD.3. If the removed balance material condition is acceptable, perform a magnetic particle inspection of the disc rim and slots for cracks using a 3 to 7 power magnification glass. The Engine Overhaul Manual, 72-34-11, Inspection/Check, contains information on the magnetic particle inspection procedure.4. Replace the disc if any cracks are found.Note 2: FAA AD 2009-08-07 Amdt 39-15880 dated 6 April 2009 refers. |\n| Compliance:    | At the next shop visit, but not later than 2,500 cycles-in-service after the effective date of this AD, unless the actions have already been done.                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                 |\n\n|             | This Airworthiness Directive becomes effective on 4 June 2009.                                                                                                                                                                                                                                                                                    |\n| ----------- | ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |\n| Background: | This AD results from reports of discs found with excessive material removed from the balancing locations of the disc. The issuing of this AD is intended to prevent the discs from fracturing before reaching the currently published life limit. A disc fracture could result in an uncontained failure of the disc and damage to the aeroplane. |\n\n![](image.003.png)  \nJames Coyne  \nDelegate of the Civil Aviation Safety Authority\n\n17 April 2009","sortOrder":0},{"sectionNumber":"AD/ALF/21","sectionType":"part","heading":"AD/ALF/21","content":"## AD/ALF/21","sortOrder":1},{"sectionNumber":"High Pressure Compressor Discs","sectionType":"part","heading":"High Pressure Compressor Discs","content":"## High Pressure Compressor Discs","sortOrder":2},{"sectionNumber":"6/2009","sectionType":"part","heading":"6/2009","content":"## 6/2009","sortOrder":3}],"analysis":{"flash_summary":{"complexity_score":4,"scope_assessment":{"changed":false,"description":"The instrument enforces inspections and replacements for the specified discs to prevent premature fracture, consistent with its stated purpose (Background). It does not broaden applicability beyond the listed engine models and part numbers, nor does it alter published life limits; it adds an intermediate inspection and replacement trigger tied to shop visits and cycles (Applicability; Requirement; Compliance)."},"complexity_factors":["Technical measurement requirement: dimensional limits for removed balance material are set by figure-based tolerances, requiring precise measurement tools and interpretation (Requirement, Figure 1).","NDT capability: magnetic particle inspection of rim and slots at 3–7× magnification is mandated and references the Engine Overhaul Manual (Requirement; Engine Overhaul Manual 72-34-11).","Cycles- and shop-visit scheduling: applicability and compliance are based on cycles‑since‑new and the ‘‘next shop visit / 2,500 cycles’’ window, creating tracking and maintenance‑planning burdens (Applicability; Compliance).","Parts-specific scope: applicability is narrowly tied to particular engine models and part numbers, so operators must identify affected serials/parts (Applicability).","Operational cost and downtime: replacement where limits or cracks are found imposes direct parts and labour costs and aircraft downtime on operators (Requirement; Background).","Regulatory cross-reference: the AD cites FAA AD 2009-08-07, implying coordination or alignment with foreign regulator requirements (Requirement, Note 2).","Clear safety objective but binary outcome: the remedy is inspection/replace (mechanical, non-discretionary), reducing regulator discretion but concentrating costs on operators (Requirement; Compliance).","Inspection interpretation risk: reliance on figure limits and manual procedures creates scope for varying technician judgments and potential rework (Requirement; Engine Overhaul Manual reference)."],"plain_english_summary":"This Airworthiness Directive requires operators of Honeywell ALF502L-2 and ALF502L-2C turbofan engines fitted with the specified HPC first-stage discs (P/Ns 2-101-331-03, -04, -10) to inspect those discs for excessive balance‑material removal and for rim/slot cracks, and to replace any discs that exceed the limits. Inspections use dimensional checks and magnetic particle testing and must occur at the next shop visit or within 2,500 cycles. It affects engine maintainers and aircraft operators who must bear inspection, NDT and replacement costs."},"kimi_summary":{"content_quality":"ok","complexity_score":3,"scope_assessment":{"changed":false,"description":"This is a targeted safety directive addressing a specific manufacturing defect in specific engine components. The scope remains precisely limited to the identified safety risk without expansion into broader operational or regulatory matters."},"complexity_factors":["Single, specific technical subject matter (one engine component on specific engine models)","Clear, sequential requirements (4 numbered steps)","Only 3 specific part numbers affected","Single compliance deadline with straightforward exception ('unless already done')","Minimal cross-referencing (only one reference to FAA AD and engine manual)","No nested definitions or interpretation sections","Technical but precise language appropriate for aviation maintenance professionals"],"plain_english_summary":"This AD requires operators of Bombardier CL-600 jets with Honeywell/AlliedSignal ALF502L-2/-2C engines to inspect high‑pressure compressor discs because some were manufactured with excessive balance material removed, risking disc fracture and uncontained engine failure.  \n\nDiscs with 5,000+ flight cycles must be measured and replaced if material removal is excessive; acceptable discs require magnetic particle crack inspections and replacement if cracked. Compliance is at next overhaul or within 2,500 flight cycles."},"flash_summary_failed":{"failed":true,"reason":"Unauthenticated. Configure AI_GATEWAY_API_KEY or use a provider module. Learn more: https://ai-sdk.dev/unauthenticated-ai-gateway","source":"analysis-cron"}},"importantCases":[],"_links":{"self":"/api/acts/ad-alf-21-high-pressure-compressor-discs","history":"/api/acts/ad-alf-21-high-pressure-compressor-discs/history","analysis":"/api/acts/ad-alf-21-high-pressure-compressor-discs/analysis","conflicts":"/api/acts/ad-alf-21-high-pressure-compressor-discs/conflicts","importantCases":"/api/acts/ad-alf-21-high-pressure-compressor-discs/important-cases","documents":"/api/acts/ad-alf-21-high-pressure-compressor-discs/documents"}}