AD/RAD/79 Amdt 1 - Thales Avionics TA/RA VSI-TCAS Indicator

This AD rests on several technical and regulatory concepts, stated in the source text and used to structure the remedial requirements.

TA/RA VSI‑TCAS indicator and ACAS II: The indicator in question is the Thales Avionics TA/RA VSI‑TCAS indicator. The Applicability limits the AD to those indicators when they are installed in conjunction with a TCAS II Change 7 (described in the AD as ACAS II) computer. The AD therefore targets an interaction between the indicator hardware/software and the ACAS II computer rather than standalone indicator behaviour.

Resolution Advisory (RA) modes and failure display: The concrete fault is that when a "Don’t climb‑Don’t descend‑Maintain" RA is issued (a multi‑aircraft encounter configuration), the indicator may present an "RA fail" message. The Background explains that, under normal operation in this RA condition, the vertical speed scale should display a green arc of ±250 ft/min with the remainder of the scale red. However, in the described scenario the display is incorrect even though the audio annunciation and traffic display are correct (Background). The AD therefore separates the correctness of different information channels: aural annunciation and traffic display remain reliable, the VSI‑TCAS display may be unreliable.

Temporary operational limitation vs software modification: The AD imposes a temporary operational mitigation in the AFM that directs crews to follow the audio annunciation and maintain vertical speed when a "Don’t climb‑Don’t descend‑Maintain" RA occurs, despite an "RA fail" indication on the indicator (Requirement 1). The permanent remedy is a software modification of the indicator per Thales Service Bulletins (Requirement 2). After modification, the temporary AFM limitation may be removed (Requirement 2).

Acceptable compliance methods and documentation: The AD explicitly permits "inserting a copy of this Directive in the AFM" as an acceptable method of complying with the AFM amendment requirement (Requirement 1). It also identifies the specific Thales Service Bulleting numbers that are to be used for the software modification (457400‑34‑082 through ‑085) (Requirement 2). These enumerations constitute the AD’s specified means of compliance.

Operator verification responsibility and certification interface: Note 2 places responsibility on the operator to "check with the design approval holder of the ACAS II installation" that modifying the indicator software "doesn’t alter the initial aircraft ACAS II installation airworthiness condition." That makes clear the AD treats the indicator software modification as a change that may interact with the certified ACAS II installation, and it pushes the verification obligation onto the operator to liaise with the design approval holder.

Scope exclusions and variant fitments: Note 1 lists a set of part numbers not covered by this AD where those P/N are installed with TCAS I computers; in other words the AD applies only where the listed indicators are paired with ACAS II (TCAS II Change 7). The Applicability list of many P/Ns , and the explicit exclusion list , are a primary instrument for delineating the AD’s scope.

Regulatory basis and notification: The AD is issued by a CASA delegate under subregulation 39.1(1) of CASR 1998 (opening paragraph) and it was notified in the Commonwealth of Australia Gazette on 21 April 2004 (signature block). The AD cross‑references a foreign authority AD (DGAC AD F‑2004‑053) and a Thales Service Information Letter (Note 3), indicating the technical issue had international visibility and vendor guidance.

Probability and hazard framing: The Background states the probability of encountering the scenario that triggers the errant display is low, but the configuration is critical (an aircraft between two others) and "this incorrect display may lead to a hazardous situation if the wrong interpretation of the required manoeuvre is made by the crew." That textual framing justifies the AD’s combination of immediate AFM mitigation and software modification.

Together, these concepts structure the regulatory remedy: restrict scope by part number and installation, mandate a temporary crew procedure to avoid misinterpretation, require specified software updates, and impose an operator duty to confirm airworthiness effects on the broader system installation.

The AD explicitly names the class of equipment and installation combinations subject to its requirements, and thereby identifies the stakeholders who must act.

Aircraft operators: The primary affected parties are operators of aircraft in which the listed Thales Avionics TA/RA VSI‑TCAS indicators (the detailed P/N list in the Applicability) are installed in conjunction with a TCAS II Change 7 (ACAS II) computer (Applicability). For those operators, the AD imposes immediate procedural changes to the Aircraft Flight Manual (Requirement 1) and a requirement to modify indicator software per Thales Service Bulletins (Requirement 2). The AFM amendment must be done within 15 days (Compliance), so operators with affected equipment must act promptly after the Amendment’s effective date.

Flight crew: Pilots and other relevant crew operating affected aircraft are directly implicated because the temporary AFM limitation prescribes an operational action for the crew: when a "Don’t climb‑Don’t descend‑Maintain" RA is triggered and the TA/RA VSI‑TCAS indicates an RA fail message, the crew are to follow the audio annunciation and maintain vertical speed until the clear of conflict condition is achieved (Requirement 1). The AD thus changes crew behaviour in a discrete RA scenario.

Maintenance organisations and engineers: Maintenance providers that perform software modifications, log AFM amendments, or certify the indicator modification will be involved. The AD requires the software modification to be accomplished "in accordance with the following Thales Avionics Service Bulletins" (Requirement 2). Those organisations must apply the correct service bulletin by P/N and record the modification.

Design approval holders and installation certifiers: Note 2 places an explicit onus on the operator to check with the design approval holder of the ACAS II installation that the TA/RA VSI‑TCAS software modification "doesn’t alter the initial aircraft ACAS II installation airworthiness condition." That pulls in the design approval holder (the entity that holds the type design or installation approval for the ACAS II system) because they must confirm whether the modification interacts with the original certification basis for the ACAS II installation.

Thales Avionics (supplier): Thales is implicated because the AD directs the use of Thales Service Bulletins and references a Thales Service Information Letter (Note 3). Thales supplies the corrective software and the associated service documentation that operators and maintenance organisations must use.

Regulator and compliance enforcers: CASA, via the delegate who issued the AD under CASR subregulation 39.1(1), is the authority that requires compliance and set the compliance dates. The AD was notified in the Commonwealth of Australia Gazette (final lines), indicating the regulator’s formal notice.

Excluded parties: Indicators with certain P/N when installed with TCAS I are explicitly excluded (Note 1). The list of excluded P/N (for TCAS I installations) must be checked by operators; if an indicator is one of those P/N and is fitted to TCAS I, the AD does not apply.

Secondary stakeholders: Operators may need to coordinate with their operations and safety departments to implement the temporary AFM limitation, schedule aircraft downtime for the software modification, and liaise with the design approval holder. Cargo and passenger customers could be indirectly affected by aircraft downtime, but the AD text does not quantify such operational impacts.

In short, the AD places immediate obligations on operators and crews of affected aircraft, requires maintenance organisations to execute specific software mods, and requires operator coordination with the ACAS II design approval holder to confirm continued conforming airworthiness. The scope is deliberately limited to particular P/Ns when installed with TCAS II Change 7, and to exclude certain P/N when installed with TCAS I.

The AD sets out discrete duties for operators, maintenance organisations, and crew; it also describes acceptable compliance methods and a limited right to remove the temporary limitation after the permanent modification is carried out.

AFM amendment duty ( Requirement 1 ): Operators of affected aircraft must amend the Aircraft Flight Manual to include the exact temporary limitation wording provided in the AD. The required text is explicit: it warns that when a "Don’t climb‑Don’t descend‑Maintain" RA is triggered the TA/RA VSI‑TCAS may indicate an RA fail message whereas audio annunciation and traffic display information are correct; it instructs the crew to follow the audio annunciation and maintain vertical speed until clear of conflict. The AD allows 'inserting a copy of this Directive in the AFM' as an acceptable means of complying with this duty (Requirement 1). The Compliance paragraph imposes a deadline for this duty: within 15 days after the effective date of the Amendment.

Software modification duty ( Requirement 2 ): Operators must modify the software of all affected TA/RA VSI‑TCAS indicators installed on aircraft equipped with an ACAS II computer in accordance with the listed Thales Avionics Service Bulletins (457400‑34‑082, ‑083, ‑084, ‑085). The AD states that following modification the temporary AFM limitation "may be removed from the AFM" (Requirement 2), which is the AD’s specified mechanism for restoring the prior AFM state , subject to confirmation that the modification resolves the issue and that removal does not impair airworthiness.

Operator verification duty ( Note 2 ): The AD places a verification duty on the operator to check with the design approval holder of the ACAS II installation that the TA/RA VSI‑TCAS software modification "doesn’t alter the initial aircraft ACAS II installation airworthiness condition." That is an operator obligation to confirm the modification’s interaction with the broader certified system.

Acceptable compliance methods and service documentation duty: The AD prescribes particular service bulletins as the required means of software modification (Requirement 2). Compliance depends on performing the modification "in accordance with" those bulletins; the bulletins themselves set technical steps, though the AD reproduces only the bulletin identifiers.

Right to remove temporary limitation: The AD gives operators the right to remove the temporary AFM limitation after the software modification is completed (Requirement 2). Removal is conditional on completing the modification as specified; the AD does not state any further approval mechanism for the removal, though Note 2 suggests operators should confirm with the design approval holder regarding the installation’s airworthiness condition.

Scope exclusion qualification ( Note 1 ): Operators of indicators with certain P/Ns installed with TCAS I do not have the duties imposed by this AD. Those P/Ns are listed explicitly in Note 1. This is a right to non‑application, but only where the installation is with TCAS I, not TCAS II.

Documentation and record-keeping expectations: The AD expressly permits inserting the Directive into the AFM as acceptable compliance for Requirement 1. It does not otherwise prescribe a record‑keeping regime in the text provided; however, the explicit instructions to modify software per Thales SBs imply maintenance records and modification entries will be necessary as part of standard maintenance practice.

No penalty or enforcement detail in text: The AD is issued under subregulation 39.1(1) of CASR 1998 (opening paragraph), which is the regulatory basis for mandating correction of unsafe conditions. The AD text itself does not specify penalties, processes for reporting compliance to CASA, or approval procedures associated with the AFM amendment or the removal thereof. Those matters, if applicable, would be governed by the referenced regulation and usual airworthiness administration practice, but the AD text itself confines duties to the AFM amendment, the software modification per the listed service bulletins, and the operator‑to‑design‑approval‑holder check (Requirement 1; Requirement 2; Note 2).

In short, the AD’s key duties require prompt AFM amendment, completion of specified software updates, and operator confirmation with the design approval holder; the AD prescribes acceptable means for AFM amendment and specific service bulletins for the software fix, and it allows removal of the temporary limitation after modification.

The AD’s text establishes its regulatory basis and compliance dates but does not set out specific monetary penalties or enforcement procedures within the document itself. The opening paragraph states the AD is issued by the CASA delegate under subregulation 39.1(1) of CASR 1998 and requires the actions described in the Requirement section to be taken in relation to the aircraft or aeronautical product mentioned in the Applicability statement (opening paragraph). That invocation is the AD’s enforcement foundation: it is a legislative or delegated‑legislative instrument mandating actions to correct an unsafe condition.

Compliance timing as an enforcement lever: The AD sets firm compliance timelines. Requirement 1 must be satisfied "Within 15 days after the effective date of this Amendment" (Compliance for Requirement 1). Requirement 2 retains the original compliance timing unchanged as "Before 31 December 2007" (Compliance for Requirement 2). Those deadlines are the AD’s temporal enforcement mechanism. The Amendment became effective on 21 April 2004 (closing lines), so the 15‑day deadline operates relative to that date.

Absence of penalty specifics in the AD text: The AD does not specify fines, licence sanctions, or the procedural steps CASA would take to enforce non‑compliance. The document is focused on mandating corrective action and setting timelines, and it provides no detail on the administrative or criminal penalties that may apply under the wider regulatory framework. Any penalties or enforcement processes would therefore be drawn from CASR 1998 and associated enforcement policy and procedures outside the AD text.

Notification and formal recording: The AD was notified in the Commonwealth of Australia Gazette on 21 April 2004 (final lines), establishing its public and formal promulgation. That publication is part of the formalisation of the AD and supports enforcement insofar as it gives legal notice to affected parties.

Practical enforcement mechanisms implied: Although not stated in the AD, typical enforcement of ADs rests on the regulator’s ability to ground aircraft, refuse airworthiness certifications, or require corrective actions before permitting operations. The AD’s explicit deadlines and the requirement that AFM contents be amended provide concrete, auditable items auditors and inspectors can check during operations or maintenance oversight. The AD’s instruction to accomplish specified service bulletins also provides a tangible record trail (service bulletin reference numbers) that maintenance records should reference.

Interaction with design approval holder responsibilities: Note 2 imposes a duty on the operator to check with the design approval holder that the modification does not alter the initial ACAS II installation airworthiness condition. If such a check were to reveal that additional approvals or design changes are required, enforcement could follow the applicable certification procedures, though the AD itself does not take that step on the record.

In sum, the AD is enforced by its regulatory source (CASR subregulation 39.1(1)) and by the deadlines and concrete actions it prescribes. The AD does not enumerate specific penalties or enforcement steps in its text; those are left to the wider regulatory framework and administrative practice of CASA.

The AD frames its authority and interaction narrowly but with explicit cross‑references to other regulatory and technical instruments in the source text.

Regulatory basis under CASR 1998: The AD is issued by the CASA delegate under subregulation 39.1(1) of CASR 1998 (opening paragraph). That locates the AD within the Civil Aviation Safety Regulations framework; the AD therefore functions as a delegated regulatory instrument that requires corrective action to address an unsafe condition. The document itself does not reproduce CASR provisions beyond this citation, but the citation serves as the legal hook authorising the imposition of the requirements set out.

Interaction with ACAS II installation approval: Note 2 directs operators 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." This creates an interface between the AD’s mandated corrective action and the certified installation basis for ACAS II. If the modification affects the installation’s certification basis, further airworthiness approvals could be required under the aircraft’s certification rules and the rules governing changes to certified installations. The AD does not itself describe the post‑check process, but it preserves the need to ensure the modification is compatible with the installation’s original approval.

Cross‑reference to foreign AD and manufacturer information: Note 3 references DGAC AD F‑2004‑053 and Thales Avionics Service Information Letter THAV/SIL‑1064 Issue 03 dated 4 June 2003. That indicates the issue has been addressed by the French DGAC and by Thales technical notices, and the AD picks up those external documents as relevant materials. The practical effect is that operators may need to consult foreign authority ADs and manufacturer service information to implement the technical fix and to understand the broader regulatory context; the AD itself requires particular Thales Service Bulletins for the software modification (Requirement 2).

Interaction with aircraft operating documentation and maintenance regulations: The AD requires an AFM amendment (Requirement 1) and allows insertion of the Directive itself into the AFM as an acceptable means of compliance. AFM content is part of an aircraft’s operational documentation under airworthiness and operations regulations; therefore the AD’s AFM amendment duty will interact with the rules governing AFM changes, operator approvals for AFM revisions, and the continuing airworthiness obligations to ensure the AFM is accurate and current. The AD does not detail approval processes for AFM changes, but by requiring the amendment it engages those existing regulatory controls.

No conflicts or supersessions specified beyond revocation: The AD revokes the previous AD/RAD/79 and issues this AD under the same regulatory authority (opening paragraph). The AD text states this amendment "continues the requirements of the original issue adding part number 457400SB0711 to the Applicability Statement" (Background). Thus the AD supersedes and modifies the earlier directive in a limited way, rather than creating an independent parallel regime.

Compliance timing relative to other obligations: The AD specifies its own deadlines (15 days for AFM amendment; before 31 December 2007 for software modification). Operators must meet these dates in addition to any other obligations under CASR or their air operator certificate requirements, creating a temporal interaction with ongoing maintenance schedules and certification cycles.

In short, the AD operates within the CASR 1998 authority, interacts practically with the certified ACAS II installation via Note 2, references foreign authority and manufacturer's service information, and engages the existing regulatory regimes governing AFM changes and continuing airworthiness. The AD does not itself set out the broader legal procedures for approval of installation changes, enforcement sanctions, or cross‑jurisdictional recognition; those steps remain within the wider regulatory instruments it cites and the practices of CASA and the design approval holder.

The AD itself records a concise amendment history and the provenance of this instrument.

Revocation and reissue: The preamble states that the CASA delegate revokes Airworthiness Directive AD/RAD/79 and issues the following AD under subregulation 39.1(1) of CASR 1998 (opening paragraph). The text therefore replaces a prior AD/RAD/79 with this amendment, continuing the regulatory control over the same unsafe condition but including modifications set out in the current document.

Effective dates and signature: The Amendment is signed by James Coyne, Delegate of the Civil Aviation Safety Authority, dated 15 April 2004 (signature block). The closing lines state that "This Amendment becomes effective on 21 April 2004" and that "The above AD is notified in the Commonwealth of Australia Gazette on 21 April 2004." The original issue of the Directive "became effective on 14 April 004" (Background) , there is a typographical omission of the final digit in that sentence, but it indicates the original issue predated this Amendment and was effective in mid‑April 2004.

Change to Applicability: The Background states this amendment "continues the requirements of the original issue adding part number 457400SB0711 to the Applicability Statement." Therefore the substantive amendment compared with the original AD is the addition of that part number into the list of affected P/Ns. The Amendment did not change the AFM mitigation requirement or the service bulletins; Requirement 2's compliance timing "remains unchanged as ‘Before 31 December 2007’" (Compliance). The AFM requirement has a new 15‑day compliance period relative to the Amendment’s effective date.

Original AD content conserved: The Background explains the original issue of the 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." The Amendment continues those requirements, which shows continuity of approach: temporary operational mitigation followed by vendor software remedy.

Cross‑references to external documents: Note 3 records DGAC AD F‑2004‑053 and Thales Avionics Service Information Letter THAV/SIL‑1064 Issue 03 dated 4 June 2003 as relevant external items referenced in the AD. Those documents form part of the background technical record and are likely the sources for the service bulletins and the original identification of the unsafe condition, although the AD text itself is the domestic regulatory instrument.

Documentation of applicability list: The table of affected part numbers and the Note 1 exclusion list are a core part of the Amendment. The addition of P/N 457400SB0711 is explicitly recorded in the Background. The Applicability table lists many P/Ns across several columns; the AD both adds and excludes P/Ns, which is the material content change from the original AD.

In sum, the Amendment revokes and supersedes AD/RAD/79, preserves the original mitigation and modification approach, adds at least one part number to the applicability, fixes compliance timing for the AFM amendment, and was signed and made effective in April 2004 with Gazette notification on 21 April 2004.

The AD text contains no references to litigation, appeals, judicial review, or tribunal decisions arising from this Directive or its implementation. There are no cases, enforcement proceedings, or legal disputes cited in the document.

The only procedural markers in the document are administrative: issuance by a CASA delegate under subregulation 39.1(1) of CASR 1998 (opening paragraph), signer and date (James Coyne, 15 April 2004), and notification in the Commonwealth of Australia Gazette on 21 April 2004 (closing lines). The AD does cross‑reference DGAC AD F‑2004‑053 and a Thales Service Information Letter (Note 3), but those are technical and administrative documents rather than records of litigation.

Therefore, based on the provided source, there is no litigation history to report. Any challenges, enforcement actions, or court decisions related to this AD are not recorded in the text supplied.

The AD includes several concrete traps for implementers; these are points where failure to follow the text literally or to check adjacent certification elements can produce non‑compliance or unintended consequences.

1. Applicability depends on both part number and ACAS II installation: The Applicability attaches to specific TA/RA VSI‑TCAS indicator part numbers and only where they are "installed in conjunction with a TCAS II Change 7 (ACAS II) computer." An indicator with an affected P/N installed with TCAS I is excluded per Note 1. Implementers must therefore check both the indicator P/N and the TCAS configuration on the aircraft. Misreading the Applicability could lead to unnecessary modification or failure to comply where the TCAS variant differs.

2. Exact AFM wording is required and a 15‑day deadline applies: Requirement 1 prescribes the precise wording to be included in the AFM and provides that inserting a copy of the Directive into the AFM is acceptable. However, the Compliance paragraph requires this AFM amendment "Within 15 days after the effective date of this Amendment." Operators must ensure the AFM entry is made within that tight window; the AD does not provide for staggered implementation. The AD becomes effective on 21 April 2004, so the 15‑day clock starts there.

3. Temporary instruction may contradict the indicator display: The AD stipulates that when the particular RA occurs and the TA/RA VSI‑TCAS indicates RA fail, the crew should follow the audio annunciation and maintain vertical speed. This creates a situation where a crew must deliberately disregard a fail indication on an indicator if the audio annunciation and traffic display are correct. Flight crew training, SOP updates, and proficiency checks must reflect that specific instruction. Failing to ensure crews understand and can execute the temporary limitation could produce unsafe outcomes despite compliance on paper.

4. Software modification interacts with ACAS II installation airworthiness: Note 2 places responsibility on the operator to check with the design approval holder that the indicator software modification "doesn’t alter the initial aircraft ACAS II installation airworthiness condition." If the modification does interact with the certified installation, additional approvals or engineering action could be required, and those steps are not specified in the AD. That creates a compliance pathway that can delay or complicate the fix beyond simply applying a service bulletin.

5. Multiple service bulletins and part‑number mapping: Requirement 2 lists four Thales Service Bulletins (457400‑34‑082, ‑083, ‑084, ‑085). Operators and maintenance organisations must apply the correct bulletin for the specific indicator variant. Applying the wrong bulletin could leave the issue unresolved or alter other behaviours of the indicator. The AD does not map each P/N to a specific SB in the text; implementers must ensure the SB used is the applicable one for the unit fitted.

6. Removal of temporary AFM limitation is conditional, not automatic: Requirement 2 states that "Following modification of the affected indicator the temporary limitation may be removed from the AFM." The permissive "may" means removal is allowed, but Note 2 suggests the operator should confirm the modification’s effect with the design approval holder. Practically, operators should document the modification and the basis for AFM restoration; failure to do so may create audit issues.

7. Documented exclusions must be validated: Note 1 lists specific P/Ns not applicable when installed with TCAS I. Aircraft records, equipment logs, and maintenance data must be checked to confirm whether an indicator is indeed installed with TCAS I or TCAS II. A mistaken classification could lead to non‑compliant operations if an affected P/N is treated as excluded.

8. No penalty mechanics stated: The AD does not set out enforcement or penalty details, but compliance is mandated under CASR. Operators must not assume lack of penalty language implies lenience; ADs are mandatory instruments. Absence of explicit reporting instructions in the AD means operators must follow standard CASA reporting and maintenance release procedures to evidence compliance.

9. Low probability but critical scenario: The Background states the operational scenario that triggers the problem is low probability but critical (aircraft between two others). Operators might be tempted to deprioritise the software fix due to low probability; however, the AD requires both rapid AFM amendment and a later software remedy, signalling regulator emphasis on the hazard despite low frequency.

10. Timing mismatch between AFM amendment and software fix: The AFM amendment is required within 15 days, while the software fix has a longer compliance date (before 31 December 2007). That staggered schedule obliges operators to keep a temporary mitigating procedure in place potentially for an extended period, which has operational, training and audit implications.

Each of these "gotchas" derives directly from the AD text (Applicability; Requirement 1; Requirement 2; Note 1; Note 2; Compliance; Background) and should be treated as concrete implementation checkpoints for operators, maintenance organisations and flight operations departments.

The AD prescribes a clear sequence of actions; the following pragmatic compliance checklist restates those steps in operational order, citing the relevant provisions in the AD.

1. Identify affected aircraft and equipment (Applicability)

   • Inspect aircraft equipment records and physical units to confirm whether the installed TA/RA VSI‑TCAS indicator is one of the part numbers listed in the Applicability.
   • Confirm the indicator is installed "in conjunction with a TCAS II Change 7 (ACAS II) computer." If the indicator P/N is one of those listed in Note 1 and is installed with TCAS I, the AD does not apply.

2. Implement the AFM temporary limitation within 15 days (Requirement 1; Compliance)

   • Within 15 days after the effective date of this Amendment (the Amendment became effective on 21 April 2004), amend the Aircraft Flight Manual to include the precise temporary limitation wording supplied in Requirement 1: "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 the Directive in the AFM is an acceptable means of complying with this Requirement (Requirement 1). Ensure that the AFM amendment is captured in the operator’s document control and distribution system so that crews receive the update promptly.

3. Train and brief flight crew (Requirement 1)

   • Issue operations notices and brief affected crews on the specific temporary limitation: when the specified RA occurs and an "RA fail" display appears, crews must follow the audio and maintain vertical speed until clear of conflict.
   • Update SOPs and quick reference material where necessary to reflect the temporary AFM limitation.

4. Plan and schedule the software modification per Thales Service Bulletins (Requirement 2)

   • Arrange for the TA/RA VSI‑TCAS software modification to be carried out "in accordance with" the listed Thales Service Bulletins: 457400‑34‑082, 457400‑34‑083, 457400‑34‑084, 457400‑34‑085 (Requirement 2). Determine which bulletin applies to each specific P/N and software baseline.
   • Complete the software modification on each affected indicator before 31 December 2007 (Compliance for Requirement 2). Coordinate with maintenance providers to schedule aircraft downtime and ensure the correct SB is applied for the specific indicator variant.

5. Check with the design approval holder (Note 2)

   • Before or as part of accomplishing the software modification, verify with the design approval holder of the ACAS II installation that the TA/RA VSI‑TCAS software modification "doesn’t alter the initial aircraft ACAS II installation airworthiness condition." Document the outcome of that verification and any additional approvals or corrective actions required.
   • If the design approval holder identifies a need for further certification or installation changes, follow the required approval pathways under the aircraft continuing airworthiness and modification approval processes.

6. Record and document modifications and AFM changes

   • Ensure the software modification is recorded in the aircraft’s maintenance log with reference to the Thales Service Bulletin applied, and retain any completion certificates or service centre documentation.
   • Record the AFM amendment in the operator’s document revision system. If a copy of the Directive was inserted into the AFM, note where that copy is filed and the date of insertion.

7. Remove the temporary AFM limitation after modification (Requirement 2)

   • After the software modification has been completed and any necessary design approval holder confirmation obtained, remove the temporary limitation from the AFM if appropriate. Requirement 2 states the temporary limitation "may be removed" following modification; ensure the basis for removal is documented.

8. Maintain audit trail for compliance and inspections

   • Keep an auditable trail showing the date and method of AFM amendment, crew briefings, scheduling and completion of software modifications, and the confirmation from the design approval holder.
   • Be prepared to present these records during regulatory inspections or audits. Although the AD does not specify reporting mechanics, standard maintenance and operational oversight regimes require retention of such records.

9. Consult the referenced materials if needed (Note 3)

   • Note 3 references DGAC AD F‑2004‑053 and Thales Service Information Letter THAV/SIL‑1064 Issue 03 dated 4 June 2003. Use these documents as supplementary technical references where necessary, and refer to Thales service bulletins for detailed modification steps.

10. Confirm scope and ongoing obligations

• Re‑check applicability after any equipment changes: if an indicator is replaced, re‑assess whether the new unit falls under the AD’s Applicability.
• Ensure ongoing compliance with CASR and company continuing airworthiness obligations. The AD does not specify broader reporting obligations, so follow CASA’s standard reporting and continuing airworthiness procedures as applicable.

This compliance route mirrors the AD’s structure: immediate AFM amendment and crew instruction (Requirement 1), followed by a software fix per manufacturer bulletins (Requirement 2), with an operator duty to verify effects on the broader certified installation (Note 2) and clear, auditable record‑keeping throughout.