{"id":"F2006B02313","name":"AD/ALF/17 - No. 4 and 5 Duplex Bearing Assembly","slug":"ad-alf-17-no-4-and-5-duplex-bearing-assembly","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":41543,"registerId":"commonwealth-F2006B02313-current","compilationNumber":null,"startDate":"2026-04-01","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"AIRWORTHINESS DIRECTIVE","sectionType":"part","heading":"AIRWORTHINESS DIRECTIVE","content":"# AIRWORTHINESS DIRECTIVE\n\n![](image.001.png)\n\n![](image.001.png)  \nFor the reasons set out in the background section, the CASA delegate whose signature appears below issues the following Airworthiness Directive (AD) under subregulation 39.1 (1) of CAR 1998. The AD requires that the action set out in the requirement section (being action that the delegate considers necessary to correct the unsafe condition) be taken in relation to the aircraft or aeronautical product mentioned in the applicability section: (a) in the circumstances mentioned in the requirement section; and (b) in accordance with the instructions set out in the requirement section; and (c) at the time mentioned in the compliance section.\n\nAlliedSignal (Lycoming) Turbine Engines \\- ALF502 And LF 507 Series","sortOrder":0},{"sectionNumber":"AD/ALF/17 No. 4 and 5 Duplex Bearing Ass","sectionType":"part","heading":"AD/ALF/17 No. 4 and 5 Duplex Bearing Assembly 8/2001","content":"# AD/ALF/17 No. 4 and 5 Duplex Bearing Assembly 8/2001\n\nApplicability: Honeywell (formerly AlliedSignal) ALF502L, ALF502R and LF507 series engines installed on Canadair CL-600, BAe 146 and AVRO RJ series aircraft.\n\nRequirement: Replace the No. 4 and 5 duplex bearing assembly with an improved single No. 4 bearing assembly in accordance with Honeywell Service Bulletin (SB) ALF/LF 72- 1030, Revision 3, dated 3 April 2001 or SB ALF/LF 72-1040, Revision 2, dated 3 April 2001, as applicable.\n\nNote 1: FAA AD 2000-05-14 Amendment 39-11624, paragraph (e) refers.\n\nNote 2: Incorporation of earlier versions of SB ALF/LF 72-1030 or SB ALF/LF 72- 1040 (as applicable) meet the intent of this Directive.\n\nNote 3: Incorporation of this Directive is terminating action for Requirement 1 of AD/ALF/14 Amdt 3.\n\nCompliance: Within 6000 hours’ time in service or 6000 cycles in service from the date of this Directive whichever occurs first.\n\nThis Airworthiness Directive becomes effective on 9 August 2001.\n\nBackground: This Directive is issued to prevent the No. 4 and 5 duplex bearing failure, which may result in a stage 4 low pressure turbine rotor failure, an uncontained engine failure and damage to the aircraft.\n\n![](image.002.png)  \n\nEugene Paul Holzapfel\n\nDelegate of the Civil Aviation Safety Authority 29 June 2001\n\n![](image.001.png)","sortOrder":1}],"analysis":{"flash_summary":{"complexity_score":3,"scope_assessment":{"changed":false,"description":"The directive implements a targeted corrective change to bearing hardware for the engines and airframes listed; it replaces the No. 4/5 duplex assembly with a single No. 4 bearing and explicitly terminates Requirement 1 of AD/ALF/14 Amdt 3 (Requirement; Note 3). There is no indication in the text that the scope was broadened beyond that corrective intent."},"complexity_factors":["Technical maintenance action: replacement of a bearing assembly requiring parts, tooling and certified maintenance personnel (Requirement).","Defined applicability across multiple engine types and aircraft models, which affects a limited but specific operator group (Applicability).","Compliance timing uses two alternative metrics (hours or cycles), adding scheduling and tracking needs for operators (Compliance).","Dependency on external documents: specific Honeywell Service Bulletins and acceptable earlier revisions are referenced, creating reliance on manufacturer instructions and version control (Requirement; Note 2).","Cross-reference to prior ADs and FAA AD creates interaction with earlier mandated actions and termination of a prior requirement (Note 1; Note 3).","Safety justification is factual and specific (Background), but enforcement requires CASA oversight and maintenance record updates."],"plain_english_summary":"This Airworthiness Directive requires operators of Honeywell (AlliedSignal) ALF502L, ALF502R and LF507 engines fitted to Canadair CL-600, BAe 146 and Avro RJ aircraft to replace the No. 4 and No. 5 duplex bearing assembly with an improved single No. 4 bearing, following the Honeywell service bulletins referenced. Compliance is required within 6,000 flight hours or 6,000 cycles. The stated aim is to prevent a duplex‑bearing failure that could lead to a stage‑4 low‑pressure turbine rotor failure and an uncontained engine failure."},"kimi_summary":{"content_quality":"ok","complexity_score":2,"scope_assessment":{"changed":false,"description":"This Airworthiness Directive maintains its original narrow scope: addressing a specific mechanical defect in specific engine models. The document references prior and related directives but does not expand beyond the original safety purpose of preventing bearing failure in ALF502/LF507 engines."},"complexity_factors":["Very short document (approximately 300 words)","Only 3 defined applicability criteria (engine models and aircraft types)","Single primary requirement with clear alternative compliance paths (two service bulletin options)","Simple compliance timeframe (6000 hours OR 6000 cycles, whichever first)","Minimal cross-referencing (one FAA AD reference, one prior AD termination note)","No nested exceptions or conditional logic — straightforward mandatory replacement"],"plain_english_summary":"This safety order requires operators of Honeywell ALF502 and LF507 engines (as fitted to Canadair CL-600, BAe 146 and AVRO RJ series) to replace a hazardous No. 4/5 duplex bearing assembly with an improved single-bearing design per Honeywell service instructions. The replacement must be done within 6,000 flight hours or 6,000 flight cycles from the August 2001 effective date to prevent uncontained low-pressure turbine failures. Completing this action also satisfies the earlier AD/ALF/14."},"flash_summary_failed":{"failed":true,"reason":"A positive credit balance is required for all requests, including BYOK, so fallback providers remain available. Add credits at https://vercel.com/d?to=%2F%5Bteam%5D%2F%7E%2Fai%3Fmodal%3Dtop-up to continue.","source":"analysis-cron"}},"importantCases":[],"_links":{"self":"/api/acts/ad-alf-17-no-4-and-5-duplex-bearing-assembly","history":"/api/acts/ad-alf-17-no-4-and-5-duplex-bearing-assembly/history","analysis":"/api/acts/ad-alf-17-no-4-and-5-duplex-bearing-assembly/analysis","conflicts":"/api/acts/ad-alf-17-no-4-and-5-duplex-bearing-assembly/conflicts","importantCases":"/api/acts/ad-alf-17-no-4-and-5-duplex-bearing-assembly/important-cases","documents":"/api/acts/ad-alf-17-no-4-and-5-duplex-bearing-assembly/documents"}}