AIRWORTHINESS DIRECTIVE
For 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.
Radio Communication and Navigation Equipment
AD/RAD/79
Amdt 1
Thales Avionics TA/RA VSI-TCAS Indicator 6/2004
DM
Applicability: 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.
457400EA0311 | 457400GB1312 | 457400PB1900 |
457400EB0311 | 457400GB1900 | 457400RA0711 |
457400FA0311 | 457400GB2000 | 457400RB0711 |
457400FB0311 | 457400GB2100 | 457400SA0711 |
457400GA0311 | 457400HA1900 | 457400SB0711 |
457400GA0602 | 457400JA1900 | 457400TB0811 |
457400GA0911 | 457400KA0602 | 457400TC0811 |
457400GA1100 | 457400KA1311 | 457400UA1311 |
457400GA1311 | 457400KA1900 | 457400UA1900 |
457400GA1312 | 457400KB1311 | 457400UB1311 |
457400GA1900 | 457400KB1900 | 457400UB1900 |
457400GA0011 | 457400LA2000 | 457400WA0811 |
457400GB0011 | 457400MA0602 | 457400WB0811 |
457400GB0911 | 457400MA1311 | 457400ZA1900 |
457400GB1100 | 457400MB1311 | |
457400GB1311 | 457400PA1900 | |
Note 1: This Directive is not applicable to indicators with the following P/N as they are installed in conjunction with TCAS I computers:
457400GA1502
457400GB1502
457400MA1502
457400MB1502
457400ZA1502
457400ZB1502
Requirement: 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:
“Limitation:
When 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.”
Inserting a copy of this Directive in the AFM is an acceptable means of complying with this Requirement.
2. 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:
457400-34-082
457400-34-083
457400-34-084, and
457400-34-085
Following modification of the affected indicator the temporary limitation may be removed from the AFM.
Note 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.
Note 3: DGAC AD F-2004-053 and Thales Avionics Service Information Letter THAV/SIL-1064 Issue 03 dated 4 June 2003 refer.
Compliance: For Requirement 1 - Within 15 days after the effective date of this Amendment.
For Requirement 2 - Remains unchanged as ‘Before 31 December 2007’. This Amendment becomes effective on 21 April 2004.
Background: 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
±250 ft/min with the rest of the scale red.
The 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.
The 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.
This amendment continues the requirements of the original issue adding part number 457400SB0711 to the Applicability Statement.
The original issue of this Directive became effective on 14 April 004.
James Coyne
Delegate of the Civil Aviation Safety Authority 15 April 2004
The above AD is notified in the Commonwealth of Australia Gazette on 21 April 2004.
Overview
The Civil Aviation Safety Authority (CASA) has issued an Airworthiness Directive (AD) to address a safety issue related to the Thales Avionics TA/RA VSI-TCAS indicator in aircraft equipped with an ACAS II computer. This AD, which became effective on 21 April 2004, amends AD/RAD/79 and targets specific part numbers of the TA/RA VSI-TCAS indicators that, when installed with a TCAS II Change 7 computer, may display an incorrect "RA fail" message during a "Don't climb-Don't descend-Maintain" Resolution Advisory. The directive mandates that aircraft operators either amend the Aircraft Flight Manual (AFM) to include a temporary limitation concerning the correct interpretation of the TA/RA VSI-TCAS display or modify the software of the affected indicators according to specified Thales Avionics Service Bulletins. The objective of this AD is to ensure that pilots correctly interpret the resolution advisories, thereby preventing potential hazardous situations arising from misinterpretation of the indicator display.
Scope and Application
The Airworthiness Directive issued under the Civil Aviation Act 1988 and Civil Aviation Regulations 1988 applies to specific Thales Avionics (formerly Sextant Avionique) TA/RA VSI-TCAS indicators with particular part numbers that are installed on aircraft equipped with a TCAS II Change 7 (ACAS II) computer. This legislative instrument mandates corrective actions to address an unsafe condition identified in these indicators. The directive applies to all aircraft operators who possess or operate the specified TA/RA VSI-TCAS indicators. The geographic reach of this directive is nationwide, applicable throughout the Commonwealth of Australia. There are no stated exclusions or exemptions within the directive itself, although compliance is contingent upon the operator verifying that software modifications do not affect the initial airworthiness of the ACAS II installation. The directive can be extended or modified through subordinate instruments, ensuring it adapts to new findings or changes in technology. The directive requires operators to update their Aircraft Flight Manuals to include a temporary limitation regarding RA fail messages and mandates software modifications to the TA/RA VSI-TCAS indicators to correct the display issue. Compliance deadlines are set at 15 days for updating the Aircraft Flight Manual and 31 December 2007 for the software modifications.
Key Provisions
The Airworthiness Directive AD/RAD/79Amdt 1 pertains to Thales Avionics TA/RA VSI-TCAS indicators with specific part numbers installed with a TCAS II Change 7 (ACAS II) computer. The directive, effective from 21 April 2004, mandates certain actions to address a safety issue associated with these indicators. The applicability section (Applicability) specifies the TA/RA VSI-TCAS indicators covered by the directive, which must be installed with a TCAS II Change 7 computer. These indicators are identified by particular part numbers, excluding those installed with TCAS I computers. The requirement section (Requirement) details two actions that must be undertaken: first, operators must amend the Aircraft Flight Manual (AFM) of affected aircraft to include a temporary limitation regarding the TA/RA VSI-TCAS indicator’s display of a "Don’t climb-Don’t descend-Maintain" Resolution Advisory. Specifically, the AFM must note that the indicator may incorrectly display an "RA fail" message while the audio and traffic display information remain correct. Second, the software of the specified TA/RA VSI-TCAS indicators must be modified according to specified Thales Avionics Service Bulletins. These modifications should resolve the aforementioned display issue, allowing operators to remove the temporary limitation from the AFM.
The directive imposes several obligations on the parties it governs. Operators of aircraft equipped with the specified TA/RA VSI-TCAS indicators must ensure that the AFM is updated within 15 days of the directive's effective date to include the temporary limitation. This action is critical to inform flight crews of the potential display anomaly and to mitigate associated risks. Additionally, operators must modify the software of the specified indicators to correct the display issue, adhering to the provided Thales Avionics Service Bulletins. Compliance with these software modifications must be achieved by 31 December 2007. Operators are also responsible for verifying that these modifications do not adversely affect the airworthiness of the aircraft’s ACAS II installation. This verification should be done in consultation with the design approval holder of the ACAS II system.
Failure to comply with the provisions of this Airworthiness Directive may result in significant consequences. The directive does not explicitly outline specific penalties for non-compliance; however, non-compliance with airworthiness directives is generally considered a serious matter under aviation regulations. Such non-compliance could lead to enforcement actions by the Civil Aviation Safety Authority (CASA), which may include fines, operational restrictions, or other regulatory penalties. Furthermore, operators failing to adhere to these requirements risk compromising the safety of flight operations, potentially leading to hazardous situations or accidents. It is imperative that operators take the necessary actions to ensure compliance with the directive to maintain the highest safety standards in aviation.