{"id":"F2006B03461","name":"AD/BAe 146/109 - Thales Avionics Distance Bearing Indicator","slug":"ad-bae-146-109-thales-avionics-distance-bearing-indicator","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":43015,"registerId":"commonwealth-F2006B03461-current","compilationNumber":null,"startDate":"2026-04-01","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/BAe 146/109 - Thales Avionics Distance Bearing Indicator","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\n \n\n \n\n![](image.001.png)\n\n# AIRWORTHINESS DIRECTIVE\n\n![](image.001.png)  \n\n\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 CASR 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\n![](image.001.png)  \n\n\n \n\nBritish Aerospace BAe 146 Series Aeroplanes\n\n \n\n# AD/BAe 146/109 Thales Avionics Distance Bearing Indicator\n\n\n5/2004\n\n \n\n \n\nApplicability: Model Avro 146-RJ Series RJ70, RJ85 and RJ100 aeroplanes fitted with Thales Avionics Distance Bearing Indicator (DBI) part number (P/N) 63543-280-1 with the following serial numbers:\n\n \n\n| 3084 | 3551 to 3554 | 3687 | 3955 to 3958 |\n| --- | --- | --- | --- |\n| 3171 | 3576 | 3697 to 3700 | 3986 to 3989 |\n| 3442 | 3577 | 3717 to 3719 | 4017 to 4020 |\n| 3443 | 3602 to 3605 | 3762 to 3765 | 4042 to 4045 |\n| 3485 to 3488 | 3624 to 3627 | 3787 to 3790 | 4070 |\n| 3504 | 3664 | 3830 to 3833 | 4071 |\n| 3505 | 3665 | 3858 to 3861 | 4099 to 4104 |\n| 3518 to 3521 | 3672 | 3901 | 4137 |\n| 3528 to 3531 | 3673 | 3902 | 4138 |\n| 3544 to 3547 | 3686 | 3912 to 3915 |  |\n\n\n \n\nRequirement: Determine the part number and serial number of the DBI in accordance with BAE Systems (Operations) Service Bulletin SB 34-371-70671A dated 19 September 2003. If the DBI is found to be one of those identified in the above Applicability Statement, remove the DBI from the aeroplane and replace it with a modified Thales DBI P/N 63543-280-2 or a DBI P/N 63543-280-1, whose serial number is not listed in the Applicability Statement, in accordance with SB 34-371-70671A.\n\n \n\nNote: CAA(UK) AD G-2004-0006 refers.\n\n \n\nCompliance: Within four calendar months after the effective date of this Directive.\n\n \n\nThis Airworthiness Directive becomes effective on 13 May 2004.\n\nBritish Aerospace BAe 146 Series Aeroplanes\n\n \n\nAD/BAe 146/109 (continued)\n\n \n\nBackground: A manufacturing fault with the DBI PSU transformer could result in the propagation of the aircraft 115VAC input power supply through the instrument onto the DBI ARINC 429 Input/Output interfaces. An analysis of this failure concluded that at the aircraft level the failure effect could be loss of all aircraft primary navigation instruments.\n\n![Signature of James Coyne, Delegate of the Civil Aviation Safety Authority.](image.002.png)  \n\n\nJames Coyne\n\nDelegate of the Civil Aviation Safety Authority 1 April 2004\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\n \n\n \n\n![](image.001.png)  \n\n\nThe above AD is notified in the Commonwealth of Australia Gazette on 21 April 2004.\n","sortOrder":0}],"analysis":{"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 is a targeted safety directive addressing a specific manufacturing defect in a specific aircraft component. The scope remains precisely limited to the identified unsafe condition and affected aircraft population."},"complexity_factors":["Single, specific technical requirement with clear part numbers and serial numbers","No defined terms section — all terminology is industry-standard aviation language","No cross-references to other legislation beyond a single note referencing a UK equivalent directive","Straightforward conditional logic: if aircraft has specific part with specific serial number, then replace it","Single compliance deadline with no exceptions or alternative compliance methods","Short document (approximately 1 page of substantive content)"],"plain_english_summary":"This CASA Airworthiness Directive requires operators of BAe 146 RJ70/RJ85/RJ100 aircraft to inspect specific Thales DBI units (P/N 63543-280-1, listed serials) per the BAE service bulletin and, if matched, remove and replace them. A transformer defect can leak high voltage onto data lines and could disable all primary navigation instruments. Compliance was mandated within four months of the AD (effective 13 May 2004)."},"flash_summary":{"complexity_score":3,"scope_assessment":{"changed":false,"description":"This Airworthiness Directive is tightly focused on correcting a specific unsafe hardware condition in a limited set of Thales DBI units (identified by part number and serial numbers) installed on BAe 146/Avro RJ aircraft. It requires inspection and removal/replacement of only the affected units and does not broaden the regime to other parts, systems, aircraft types, or operator duties beyond the compliance actions and time window. Therefore the scope has not grown beyond the original safety‑remedial purpose described in the Background."},"complexity_factors":["Single narrow applicability to BAe 146/Avro RJ70/RJ85/RJ100 models","Long list of specific DBI serial numbers in the Applicability table (many discrete entries and ranges)","Requirement depends on an external technical document: BAE Systems Service Bulletin SB 34-371-70671A","Conditional action: only remove/replace if serial number matches those listed (inspection + conditional replacement)","Two approved replacement options (modified P/N 63543-280-2 or non-listed P/N 63543-280-1)","Fixed compliance window (four calendar months)","Cross-reference to a foreign regulator’s AD (CAA(UK) AD G-2004-0006)","Technical failure mode involves avionics bus (ARINC 429) and PSU transformer propagation (requires technical maintenance competence)"],"plain_english_summary":"**What this instrument requires (mechanics first)**\n\n- The directive applies to BAe 146 / Avro RJ70, RJ85 and RJ100 aeroplanes that have a Thales Avionics Distance Bearing Indicator (DBI) with part number (P/N) 63543-280-1 and one of the serial numbers listed in the Applicability table (Applicability). \n- Operators must check (determine) the DBI part number and serial number following the instructions in BAE Systems Service Bulletin SB 34-371-70671A (Requirement). \n- If an aeroplane has an affected DBI serial number, the DBI must be removed and replaced either with a modified Thales DBI P/N 63543-280-2 or with a P/N 63543-280-1 whose serial number is not on the affected list, in accordance with the same Service Bulletin (Requirement). \n- The work must be completed within four calendar months from the effective date of the Directive (Compliance). \n\n**Why this was put in place (official rationale and the mechanical test of it)**\n\n- The Background states that a manufacturing fault in the DBI power-supply transformer (PSU transformer) can allow the aircraft 115 VAC input power to propagate onto the DBI’s ARINC 429 input/output interfaces. Analysed at the aircraft level, that failure could lead to the loss of all primary navigation instruments (Background).\n- The AD therefore targets those specific DBI units whose serial numbers match the units manufactured with the fault, by requiring removal and replacement (Requirement + Applicability).\n\n**Who is affected and who pays**\n\n- Affected parties: aircraft operators/owners of BAe 146 / Avro RJ70, RJ85, RJ100 aircraft fitted with the listed Thales DBI serial numbers (Applicability). Maintenance organisations performing the work and parts suppliers (Thales/BAE) are also involved. \n- Who pays: aircraft operators bear the direct costs — inspecting the unit, purchasing the replacement DBI (P/N 63543-280-2 or a non-listed P/N 63543-280-1) and paying for removal and installation and any associated downtime.\n\n**Who decides and what choices remain**\n\n- The Civil Aviation Safety Authority (CASA) delegate issued the AD and prescribes the mandatory action, while individual operators decide scheduling (when within the 4‑month window), which approved maintenance organisation performs the work, and which acceptable replacement unit to fit (the modified P/N 63543-280-2 or a non-listed 63543-280-1) subject to the Service Bulletin instructions (Requirement, Compliance). \n- Operators may substitute between the two approved replacement options, but may not continue to operate with an affected serial-number DBI after compliance time.\n\n**Costs, trade-offs, incentives and implementation risks**\n\n- Direct cost and opportunity cost: operators must fund parts and maintenance and may incur aircraft downtime while the DBI is removed and replaced. The size of the cost depends on number of affected aircraft and availability of replacement inventory (Requirement, Applicability, Compliance). \n- Supply and scheduling risk: if replacement units or qualified maintenance slots are limited, operators may face implementation delays or higher costs. The AD sets a four‑month deadline which concentrates pressure on supply and labour resources (Compliance). \n- Substitution effects: the AD permits two replacement paths (modified 63543-280-2 or non-listed 63543-280-1), giving operators some flexibility to source parts. That flexibility may reduce per-unit cost or delay compared with a single mandated retrofit. \n- Compliance burden and enforcement: the AD is prescriptive (inspection, removal, replacement) and enforceable by CASA; operators must follow the BAE Service Bulletin for procedural details, which shifts some technical implementation responsibility to BAE’s published method (Requirement). \n- Safety benefit vs cost: the action directly addresses a specific hardware failure mode that CASA’s analysis judged could degrade primary navigation systems; the operator bears the cost to remove that quantified risk (Background).\n\n**Cross-references and administrative notes**\n\n- The Directive references BAE Systems Service Bulletin SB 34-371-70671A for the method to determine serial numbers and perform replacement (Requirement). \n- It also notes a corresponding United Kingdom CAA Airworthiness Directive (CAA(UK) AD G-2004-0006) (Note)."}},"importantCases":[],"_links":{"self":"/api/acts/ad-bae-146-109-thales-avionics-distance-bearing-indicator","history":"/api/acts/ad-bae-146-109-thales-avionics-distance-bearing-indicator/history","analysis":"/api/acts/ad-bae-146-109-thales-avionics-distance-bearing-indicator/analysis","conflicts":"/api/acts/ad-bae-146-109-thales-avionics-distance-bearing-indicator/conflicts","importantCases":"/api/acts/ad-bae-146-109-thales-avionics-distance-bearing-indicator/important-cases","documents":"/api/acts/ad-bae-146-109-thales-avionics-distance-bearing-indicator/documents"}}