{"id":"F2006B06534","name":"AD/RAD/79 Amdt 1 - Thales Avionics TA/RA VSI-TCAS Indicator","slug":"ad-rad-79-amdt-1-thales-avionics-ta-ra-vsi-tcas-indicator","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":48197,"registerId":"commonwealth-F2006B06534-current","compilationNumber":null,"startDate":"2026-04-02","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/RAD/79 Amdt 1 - Thales Avionics TA/RA VSI-TCAS Indicator","content":"![](image.001.png)\n\nAIRWORTHINESS DIRECTIVE\n\n![](image.001.png)  \n\nFor the reasons set out in the background section, the CASA delegate whose signature appears below revokes Airworthiness Directive (AD) AD/RAD/79 and issues the following 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\nRadio Communication and Navigation Equipment\n\nAD/RAD/79\n\nAmdt 1\n\n  \nThales Avionics TA/RA VSI-TCAS Indicator 6/2004\n\nDM\n\nApplicability: All Thales Avionics (formerly Sextant Avionique) TA/RA VSI-TCAS indicator with the following part numbers (P/N) installed in conjunction with a TCAS II Change 7 (ACAS II) computer.\n\n| 457400EA0311 | 457400GB1312 | 457400PB1900 |\n| ------------ | ------------ | ------------ |\n| 457400EB0311 | 457400GB1900 | 457400RA0711 |\n| 457400FA0311 | 457400GB2000 | 457400RB0711 |\n| 457400FB0311 | 457400GB2100 | 457400SA0711 |\n| 457400GA0311 | 457400HA1900 | 457400SB0711 |\n| 457400GA0602 | 457400JA1900 | 457400TB0811 |\n| 457400GA0911 | 457400KA0602 | 457400TC0811 |\n| 457400GA1100 | 457400KA1311 | 457400UA1311 |\n| 457400GA1311 | 457400KA1900 | 457400UA1900 |\n| 457400GA1312 | 457400KB1311 | 457400UB1311 |\n| 457400GA1900 | 457400KB1900 | 457400UB1900 |\n| 457400GA0011 | 457400LA2000 | 457400WA0811 |\n| 457400GB0011 | 457400MA0602 | 457400WB0811 |\n| 457400GB0911 | 457400MA1311 | 457400ZA1900 |\n| 457400GB1100 | 457400MB1311 |              |\n| 457400GB1311 | 457400PA1900 |              |\n\nNote 1: This Directive is not applicable to indicators with the following P/N as they are installed in conjunction with TCAS I computers:\n\n457400GA1502\n\n457400GB1502\n\n  \n457400MA1502\n\n457400MB1502\n\n  \n457400ZA1502\n\n457400ZB1502\n\nRequirement: 1. If not previously accomplished in accordance with the original issue of this Directive, amend the Aircraft Flight Manual (AFM) of all aircraft, equipped with an ACAS II computer and a TA/RA VSI-TCAS indicator with a P/N listed in the Applicability Statement not modified in accordance with Requirement 2, to include the following ACAS II temporary limitation:\n\n“Limitation:\n\nWhen a \"Don’t climb-Don’t descend-Maintain\" Resolution Advisory is triggered, the TA/RA VSI-TCAS may indicate an RA fail message whereas audio annunciation (\"Maintain Vertical Speed, Maintain\") and traffic display information are correct. In this specific case, the crew should follow the audio annunciation and therefore maintain the vertical speed until the clear of conflict condition has occurred.”\n\nInserting a copy of this Directive in the AFM is an acceptable means of complying with this Requirement.\n\n2. Modify the software of all TA/RA VSI-TCAS indicators, with a P/N listed in the Applicability Statement, installed on aircraft equipped with an ACAS II computer in accordance with the following Thales Avionics Service Bulletins, as applicable:\n\n457400-34-082\n\n457400-34-083\n\n457400-34-084, and\n\n457400-34-085\n\nFollowing modification of the affected indicator the temporary limitation may be removed from the AFM.\n\nNote 2: It is the responsibility of the operator to check with the design approval holder of the ACAS II installation that TA/RA VSI-TCAS equipment software modification doesn’t alter the initial aircraft ACAS II installation airworthiness condition.\n\nNote 3: DGAC AD F-2004-053 and Thales Avionics Service Information Letter THAV/SIL-1064 Issue 03 dated 4 June 2003 refer.\n\nCompliance: For Requirement 1 \\- Within 15 days after the effective date of this Amendment.\n\nFor Requirement 2 \\- Remains unchanged as ‘Before 31 December 2007’. This Amendment becomes effective on 21 April 2004.\n\nBackground: The TA/RA VSI-TCAS indicator displays an \"RA fail\" message when a \"maintain - Don’t Climb/Don’t descent\" resolution advisory (multi-aircraft encounter configuration) is issued by the ACAS II computer. Normally in this condition, the TA/RA VSI-TCAS indicator should display on the vertical speed scale a green arc of\n\n±250 ft/min with the rest of the scale red.\n\nThe probability of encountering the operational scenario leading to this resolution advisory is low but this situation, where the aircraft is located between two others, one below and one above, is critical. This incorrect display may lead to a hazardous situation if the wrong interpretation of the required manoeuvre is made by the crew. It should be noted that traffic advisory indication on the TA/RA VSI-TCAS display and aural annunciation (\"Maintain Vertical Speed, Maintain\") are correct.\n\nThe original issue of this Directive initially required the inclusion of a temporary amendment in the AFM followed by modification to the software to correct the display on the TA/RA VSI-TCAS indicator.\n\nThis amendment continues the requirements of the original issue adding part number 457400SB0711 to the Applicability Statement.\n\nThe original issue of this Directive became effective on 14 April 004.\n\n![Signature of James Coyne Delegate of the Civil Aviation Safety Authority](image.002.png)  \n\nJames Coyne\n\nDelegate of the Civil Aviation Safety Authority 15 April 2004\n\n![](image.001.png)  \n\nThe above AD is notified in the Commonwealth of Australia Gazette on 21 April 2004.","sortOrder":0}],"analysis":{"flash_summary":{"complexity_score":3,"scope_assessment":{"changed":true,"description":"This Amendment 1 does not change the core corrective approach (temporary AFM limitation followed by software modification) from the original AD; it expands the applicability narrowly by adding one additional indicator part number (457400SB0711). The amendment therefore slightly broadens the population of affected equipment but does not alter the original safety objective or introduce new types of obligations."},"complexity_factors":["46 applicable part numbers listed in the Applicability section","6 explicitly excluded part numbers (Note 1)","Two-step compliance structure: immediate AFM amendment (temporary limitation) + later mandatory software modification","Different compliance deadlines for Requirement 1 (15 days) and Requirement 2 (retained original deadline: before 31 Dec 2007)","Cross-references to four Thales service bulletins (457400-34-082, -083, -084, -085) for the corrective action","Operator responsibility to check compatibility with the ACAS II design approval holder (Note 2) — an additional conditional check outside the AD text","References to external regulatory and manufacturer documents (DGAC AD, Thales Service Information Letter) that may affect interpretation","Conditional removal of AFM limitation after successful modification (interplay between software change and operational limitation)","Revocation of a prior AD and continuation of its requirements (administrative cross-linking)"],"plain_english_summary":"**What this directive does (mechanically)\n\n- Requires operators of certain Thales Avionics TA/RA VSI-TCAS indicators (listed by part number) that are installed with a TCAS II Change 7 (ACAS II) computer to take two actions:  \n  1. Insert a temporary limitation into the Aircraft Flight Manual (AFM) within 15 days telling flight crews how to respond to a specific kind of Resolution Advisory (Requirement 1).  \n  2. Modify the indicator software in accordance with Thales service bulletins (457400-34-082, -083, -084, -085) by the previously stated compliance date (Requirement 2). After the software modification, the AFM temporary limitation can be removed.\n\n- The AD applies only to the listed indicator part numbers (46 P/Ns) when used with an ACAS II (TCAS II Change 7) computer. A small group of indicator P/Ns that are paired with TCAS I are explicitly excluded (Note 1).\n\n**Who is affected\n\n- Aircraft operators and owners that have one of the listed TA/RA VSI-TCAS indicator part numbers installed together with an ACAS II computer.  \n- Maintenance organisations that must perform the indicator software modification according to the Thales service bulletins.  \n- Flight crews on affected aircraft, because their AFM will carry an operational limitation until the software is fixed.\n\n**What crews must do (behaviour change)\n\n- If a \"Don’t climb–Don’t descend–Maintain\" Resolution Advisory (a “maintain” RA) is issued and the TA/RA VSI-TCAS shows an \"RA fail\" message or displays the vertical speed scale incorrectly, the crew must follow the aural advisory (\"Maintain Vertical Speed, Maintain\") and keep the current vertical speed until the conflict is cleared (Requirement 1). The AD accepts inserting a copy of the AD into the AFM as compliant with this requirement.\n\n**What operators must do (compliance and timing)\n\n- Insert the AFM temporary limitation within 15 days of the effective date of this amendment (Compliance for Requirement 1).  \n- Arrange for the indicator software modification using the specified Thales service bulletins. The AD retains the original compliance deadline for that modification (Requirement 2; Compliance: before 31 December 2007 as stated).  \n- After completing the software modification, the AFM limitation may be removed.\n\n**Why the regulator says it is needed (stated purpose)\n\n- The TA/RA VSI-TCAS indicator can show an \"RA fail\" message or an incorrect vertical speed display when an ACAS II issues a multi-aircraft \"maintain\" RA (one aircraft between two others). The regulator states the aural RA and traffic display are correct, but the visual failure message could be misread and lead to an unsafe manoeuvre (Background). The AD therefore imposes a temporary operational limitation and mandates a software fix.\n\n**Costs, incentives and trade-offs (practical effects)\n\n- Direct costs fall mainly on operators and maintenance providers: AFM administration (minor), aircraft downtime for software modification, labour and any parts/service fees charged by Thales or MROs (Requirement 2 and referenced service bulletins).  \n- Incentives for operators are strong to comply: safety risk to flight operations and mandatory regulatory status of an AD. Non‑compliance would expose operators to enforcement risk.  \n- Implementation risks include ensuring the software modification is compatible with the particular ACAS II installation (the AD explicitly places responsibility on the operator to check compatibility with the ACAS II design approval holder — Note 2). If compatibility is not confirmed, additional work could be required.  \n- The temporary AFM limitation shifts reliance from a possibly ambiguous visual indication to the aural RA; this requires that crews are trained/aware of the change to avoid confusion.  \n- Once software is modified, the limitation is removed, so the measure is corrective rather than permanently restrictive.\n\n**Who decides and where discretion exists\n\n- The CASA delegate issued the AD under CASR subregulation 39.1(1). The AD mandates the AFM insertion and the software modification per Thales service bulletins; the operator retains responsibility to check compatibility with the ACAS II installation (Note 2). That checking step introduces an operator-level decision and potential additional workload.\n\n**References and cross‑links that matter for compliance\n\n- The AD cross-references four Thales service bulletins (457400-34-082 to -085) for the modification procedure, and also references DGAC AD F-2004-053 and a Thales Service Information Letter (THAV/SIL-1064 Issue 03) (Note 3). Operators will need access to those documents to complete the corrective action.\n\n**Net scope change in this amendment (short summary)\n\n- This Amendment 1 continues the original AD's requirements and adds one additional indicator part number (457400SB0711) to the applicability list. Other requirements, deadlines and the nature of the corrective action remain as in the original directive (Background)."},"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"},"kimi_summary":{"content_quality":"ok","complexity_score":3,"scope_assessment":{"changed":false,"description":"This is a narrow, targeted amendment to an existing Airworthiness Directive. It adds a single part number (457400SB0711) to the applicability list and confirms existing compliance dates. The scope remains tightly focused on the original safety issue — a specific software display anomaly in Thales TCAS indicators — and has not expanded beyond this technical correction."},"complexity_factors":["Highly specific technical scope — applies only to 46 specific part numbers in combination with TCAS II Change 7 computers","Two-tier compliance structure with different deadlines for documentation update versus hardware/software modification","Cross-references to external technical documents (Thales Service Bulletins 457400-34-082 through 085)","Conditional logic: Requirement 1 applies only to units 'not modified in accordance with Requirement 2'","Exclusion clause (Note 1) identifying 6 part numbers that are explicitly not covered","Regulatory machinery references (subregulation 39.1(1) of CASR 1998) without explanatory context"],"plain_english_summary":"This AD mandates fixes for a software fault in certain Thales TA/RA VSI‑TCAS displays that can incorrectly show a “system failure” instead of the green guidance arc when the pilot is advised “Don’t climb, don’t descend, maintain your current vertical speed.” Audio and traffic displays remain correct, but pilots could follow the misleading message. Operators of aircraft with the listed Thales part numbers paired with TCAS II must insert a temporary AFM warning within 15 days and install Thales software updates by end‑2007; this revision adds one part number."}},"importantCases":[],"_links":{"self":"/api/acts/ad-rad-79-amdt-1-thales-avionics-ta-ra-vsi-tcas-indicator","history":"/api/acts/ad-rad-79-amdt-1-thales-avionics-ta-ra-vsi-tcas-indicator/history","analysis":"/api/acts/ad-rad-79-amdt-1-thales-avionics-ta-ra-vsi-tcas-indicator/analysis","conflicts":"/api/acts/ad-rad-79-amdt-1-thales-avionics-ta-ra-vsi-tcas-indicator/conflicts","importantCases":"/api/acts/ad-rad-79-amdt-1-thales-avionics-ta-ra-vsi-tcas-indicator/important-cases","documents":"/api/acts/ad-rad-79-amdt-1-thales-avionics-ta-ra-vsi-tcas-indicator/documents"}}