{"id":"F2006B03538","name":"AD/BAe 146/90 - TCAS and GPWS Aural Warning","slug":"ad-bae-146-90-tcas-and-gpws-aural-warning","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":43105,"registerId":"commonwealth-F2006B03538-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\nBritish Aerospace BAe 146 Series Aeroplanes","sortOrder":0},{"sectionNumber":"AD/BAe 146/90 TCAS and GPWS Aural Warnin","sectionType":"part","heading":"AD/BAe 146/90 TCAS and GPWS Aural Warning 7/2001","content":"# AD/BAe 146/90 TCAS and GPWS Aural Warning 7/2001\n\nApplicability: All BAe 146-100, -200 and -300 series aeroplanes, with modifications HCM50261X and (HCM01077L or HCM50273B) and (HCM50040E or HCM50040N) embodied.\n\nRequirement: Incorporate modification HCM50261Y in accordance with BAe Systems (Operations) Ltd, Modification Service Bulletin SB.34-339-50261Y dated 11 April 2001.\n\nNote: This Modification Service Bulletin has been classified as mandatory by the CAA(UK).\n\nCompliance: Before 1 March 2002.\n\nThis Airworthiness Directive becomes effective on 12 July 2001.\n\nBackground: Action specified by this Directive will prevent Traffic Collision and Avoidance System aural warnings being inhibited after a Ground Proximity Warning System (GPWS) aural warning or a GPWS test.\n\n![Signature of Eugene Paul Holzapfel, Delegate of the Civil Aviation Safety Authority.](image.002.png)  \n\nEugene Paul Holzapfel\n\nDelegate of the Civil Aviation Safety Authority 28 May 2001\n\n![](image.001.png)  \n\nThe above AD is notified in the Commonwealth of Australia Gazette on 13 June 2001.","sortOrder":1}],"analysis":{"flash_summary":{"complexity_score":3,"scope_assessment":{"changed":false,"description":"The Directive implements a corrective modification for a specific unsafe condition identified in the Background and limits applicability to BAe 146-100/200/300 aeroplanes with particular prior modifications (Applicability; Requirement; Background). It does not expand applicability beyond the aircraft/mod combinations listed, nor add additional regulatory powers or broader operational restrictions, so the scope of affected aircraft and the remedial action remains aligned with the stated intent."},"complexity_factors":["Specific applicability depends on verifying embodiment of multiple prior modifications (HCM50261X and (HCM01077L or HCM50273B) and (HCM50040E or HCM50040N)) — extra record checks for operators (Applicability).","Mandates incorporation of a single clearly referenced modification HCM50261Y via BAe Service Bulletin SB.34-339-50261Y dated 11 April 2001 — requires technical shop work but a single engineering action (Requirement).","Fixed compliance deadline (before 1 March 2002) creates scheduling pressure for fleet operators and maintenance providers (Compliance).","Relies on an external document classified mandatory by the UK CAA, so operators must obtain and follow that Service Bulletin (Note/Requirement).","Technical risk being addressed is an interaction between TCAS and GPWS aural warnings (Background) — diagnosing and testing the fix may require avionics expertise and test procedures.","Regulatory authority and enforceability are straightforward (CASA Delegate issued AD) but enforcement and approval of the modification installation rest with operators and approved maintenance organisations (front-loaded compliance burden)."],"plain_english_summary":"This Airworthiness Directive requires operators of BAe 146-100, -200 and -300 aeroplanes (that already have the listed prior modifications) to install modification HCM50261Y per BAe Service Bulletin SB.34-339-50261Y so that TCAS aural warnings are not inhibited by a GPWS aural warning or GPWS test. The Civil Aviation Safety Authority (the Delegate) sets a compliance deadline of 1 March 2002; the aircraft owner/operator must arrange and pay for the modification (Applicability; Requirement; Compliance; Background)."},"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"},"kimi_summary":{"content_quality":"ok","complexity_score":2,"scope_assessment":{"changed":false,"description":"This AD maintains its original narrow scope — a targeted safety fix for a specific technical fault in a specific aircraft type. There is no evidence of scope creep; it addresses exactly the unsafe condition described in the background without expanding to unrelated systems or aircraft types."},"complexity_factors":["Single, specific modification requirement with clear reference to manufacturer service bulletin","Limited applicability — only affects one aircraft type (BAe 146 series) with specific pre-existing modifications","No nested exceptions or conditional logic beyond the applicability criteria","Straightforward compliance deadline with no phased or variable timelines","Only 4 defined modification numbers in the entire document","No cross-references to other legislation beyond the enabling regulation (CAR 1998 subreg 39.1(1))"],"plain_english_summary":"This CASA Airworthiness Directive requires operators of British Aerospace BAe 146 (-100/-200/-300) to install a hardware modification that prevents the Ground Proximity Warning System (GPWS) or its tests from inadvertently silencing the Traffic Collision Avoidance System (TCAS).\n\nIt affects operators and maintenance organisations of BAe 146s with the referenced earlier modifications. The change restores independent alerts so pilots don’t miss critical collision warnings; compliance was mandated by 1 March 2002."}},"importantCases":[],"_links":{"self":"/api/acts/ad-bae-146-90-tcas-and-gpws-aural-warning","history":"/api/acts/ad-bae-146-90-tcas-and-gpws-aural-warning/history","analysis":"/api/acts/ad-bae-146-90-tcas-and-gpws-aural-warning/analysis","conflicts":"/api/acts/ad-bae-146-90-tcas-and-gpws-aural-warning/conflicts","importantCases":"/api/acts/ad-bae-146-90-tcas-and-gpws-aural-warning/important-cases","documents":"/api/acts/ad-bae-146-90-tcas-and-gpws-aural-warning/documents"}}