AD/RAD/51 Amdt 1 - Rockwell International/Collins Aviation Division TDR-94D Transponder

The Directive organises around a small set of core concepts, each spelled out in the text.

• Applicability: The hardware in scope is the Rockwell/Collins TDR-94D Mode S transponder identified by P/N 622-9210-002. The Directive lists multiple aeroplane types on which that transponder is installed, and it uses the phrase “installed on, but not limited to,” indicating the list is illustrative rather than exhaustive. The document therefore targets the piece of equipment by part number and particular installations, but leaves open that other types or models with the same P/N might also be in scope.
• Interim restriction (placard): The immediate operational control is a pilot-visible placard requiring that TCAS II not be operated in any mode other than the “TA only” mode. The Directive prescribes the exact text of the placard and the minimum letter height (25 mm). The placard is an operational-control measure directed at flight crew behaviour and cockpit configuration.
• Software modification (permanent remedy): The Directive requires a software modification to the transponder per a specific Collins Service Bulletin (TDR-94/94D-34-6 Rev 2, dated 21 September 1992). The modification is a technical change to firmware/software intended to remove the underlying failure mode that precipitated the operational restriction; once incorporated, the placard is no longer necessary.
• Relationship to prior instruments: The Directive explicitly cross-references the original issue of the Directive and FAA AD 93-04-02 (Amendment 39-8504). The text treats prior compliance under those instruments as discharging the requirements here (“If not previously accomplished in accordance with the original issue of this Directive or United States Federal Aviation Administration (FAA) AD 93-04-02”).
• Compliance timing and effect: The instrument sets narrow compliance windows (placard within about one month from the Directive’s effective date; software modification within about two months). The Amendment also records a limited administrative purpose , addition of a part number to the applicability list and updating of affected aircraft , and records that typographical errors were corrected.

Each of these concepts links an operational control to a technical fix, with explicit sequencing: placard first (short-term restriction), software modification second (removal of restriction). The Directive is therefore structured as a risk mitigation ladder: immediate, cheap to implement restriction followed by a mandated technical correction.

The Directive names the owners, operators, maintenance organisations and potentially lessors of aeroplanes equipped with the specified transponder as the primary parties affected. The applicable equipment is P/N 622-9210-002 (TDR-94D Mode S transponder), and the Directive lists specific aeroplane series where that transponder is installed: Beechcraft 300 series; Bombardier (de Havilland) DHC-8 series; Bombardier (Canadair) Challenger CL-601 series; British Aerospace HS 125-700 series; Dassault Mystere‑Falcon 200 and 900; Grumman Gulfstream G1159 series; Saab 340A and 340B; Short Brothers SD3-60. The list is introduced with the qualifier “installed on, but not limited to,” so operators of aircraft not listed but fitted with the P/N are also implicated.

Who pays: The Directive imposes actions that require work (fabricating and installing a placard; modifying transponder software). Those are tasks normally carried out at the expense of the aircraft operator or aircraft owner. The text does not allocate cost or funding, but the operative duties (placard fabrication/installation and software modification) are standard airworthiness maintenance items that fall to the operator or the organisation responsible for the aircraft’s maintenance.

Who decides and who certifies: The Directive is issued under the authority of the Civil Aviation Safety Authority (CASA) , the document carries the delegation signature “James Coyne, Delegate of the Civil Aviation Safety Authority” dated 6 August 2008. Execution of Requirement 2 must be performed in accordance with the Accomplishment Instructions of the named Collins Service Bulletin; that implies the modification should be carried out by maintenance personnel authorised to perform service-bulletin work under applicable maintenance regulations. The Directive treats compliance with the original issue or FAA AD 93-04-02 as an alternative means of compliance, so operators who have already performed those prior actions are not required to repeat them here.

Behavioural change mandated: Pilots must refrain from operating TCAS II in modes other than TA only until the software modification is complete (or indefinitely if the modification is never made). Maintenance organisations must either install the placard or show prior compliance, and must schedule and implement the software modification according to the Service Bulletin. The timing requirements create a short window for operators to act.

The Directive imposes specific mandatory duties and also contains limited rights (or discharge conditions) for affected operators.

Duties (explicit in the Directive text)

• Install a placard: Requirement 1 states that, if Requirement 1 was not previously accomplished under the original Directive or FAA AD 93-04-02, operators must fabricate and install a placard with the precise wording: ‘OPERATION OF TCAS II IN ANY MODE OTHER THAN THE “TA ONLY” MODE IS PROHIBITED’. The placard lettering must be at least 25 mm high and the placard must be “within the pilot’s clear view on the instrument panel.” This is a physical equipment/placard installation duty with explicit text and sizing.
• Modify transponder software: Requirement 2 requires modification of the transponder software in accordance with the Accomplishment Instructions of Collins Service Bulletin TDR-94/94D-34-6 Revision 2 dated 21 September 1992. The Directive makes clear that Requirement 2 is the durable corrective action; incorporation of that modification removes the need for the placard mandated by Requirement 1.

Rights or discharge conditions contained in the text

• Prior compliance: The Directive provides that the duties apply “If not previously accomplished in accordance with the original issue of this Directive or United States Federal Aviation Administration (FAA) AD 93-04-02.” Operators who can demonstrate prior compliance under the original Directive or FAA AD are therefore discharged from performing the repeated action.
• Removal of placard after fix: The text explicitly states that “The placard mandated by Requirement 1 is no longer necessary after this Modification is incorporated.” That creates a defined pathway for removal of the operational restriction: complete the specified software modification and the placard may be taken down.

Timing obligations

• The placard must be installed prior to 25 October 2008 (Compliance for Requirement 1).
• The software modification must be performed prior to 1 December 2008 (Compliance for Requirement 2).
• The Amendment becomes effective on 25 September 2008.

Procedural obligations implicit in the Directive

• The software modification must follow the Accomplishment Instructions in the named Service Bulletin (Collins TDR-94/94D-34-6 Rev 2). The Directive therefore channels the manner of technical compliance to the supplier’s approved procedure rather than leaving method to operator discretion.

What the Directive does not state as a right

• The Directive does not offer any alternative modification method, equivalency approval process, or stated derogation; it simply cross-references prior compliance under the original Directive or FAA AD. The text therefore appears to require either the placard and/or the specified service-bulletin modification, subject to the prior-compliance carve-out.

The Directive text itself does not include an express penalty schedule or enforcement mechanics within the body of the document. The instrument is presented as an Airworthiness Directive (AD) and states the compliance requirements and dates, but contains no statutory penalty clause or administrative sanction language in the published text provided.

What the source does say about enforcement context

• The Directive is issued by the Civil Aviation Safety Authority (CASA), evidenced by the signature line: “James Coyne, Delegate of the Civil Aviation Safety Authority.” As an AD, it is an instrument that sets mandatory airworthiness actions; the text gives compliance dates and prescribes required corrective actions to address an identified failure mode.
• The Directive cross-references FAA AD 93-04-02, which suggests alignment with the FAA’s prescriptive regime on the same hardware. The Directive treats prior accomplishment under the FAA AD as satisfying the new requirements.

What is not present and what operators should note

• The document, as supplied, does not set out criminal or civil penalties, de‑registration consequences, or suspension/withdrawal of certificates. It likewise does not present an administrative process for extension, deferment, or alternative means of compliance beyond prior compliance under the original Directive or FAA AD 93-04-02.
• Because the Directive sets mandatory compliance requirements and deadlines, non-compliance would typically be a regulatory breach under the broader aviation safety regulatory framework. The Directive text itself does not identify enforcement steps, enforcement authorities beyond the signatory, or appeal processes. Operators must therefore treat the AD’s specified actions and deadlines as mandatory and consult CASA and applicable aviation regulations for enforcement and sanction details not included in the Directive text.

Practical consequence for operators

• The absence of penalties in the Directive text does not negate the operational effect: failure to comply with an AD can have regulatory consequences under airworthiness law and operations rules. The Directive makes clear what must be done and by when; responsibility for meeting those requirements rests with the operator/owner and the organisation performing maintenance.

The Directive explicitly situates itself in relation to a prior FAA AD and the original issue of the same CASA Directive. The text contains a direct cross-reference and a carve-out for prior compliance:

• Cross-reference to FAA AD: The Requirements open with the phrase “If not previously accomplished in accordance with the original issue of this Directive or United States Federal Aviation Administration (FAA) AD 93-04-02,” and a separate note states “FAA AD 93-04-02 Amendment 39-8504 refers.” That establishes that actions already carried out under FAA AD 93-04-02 are treated as satisfying the immediate obligation of this Amendment. In practical terms, operators who complied with the FAA AD or the original CASA Directive do not need to repeat those same actions under AD/RAD/51 Amdt 1.
• Relationship to prior CASA Directive: The Directive is an amendment to AD/RAD/51 , it notes the original issue became effective on 27 May 1993 and states that this Amendment adds the P/N 622-9210-002 to the applicability, updates affected aircraft, and corrects minor typographical errors. The Amendment therefore updates the scope of the CASA AD rather than introducing a wholly new regulatory regime.
• Service Bulletin as method of compliance: Requirement 2 mandates modification in accordance with the Accomplishment Instructions of a specific manufacturer service bulletin (Collins Service Bulletin TDR-94/94D-34-6 Rev 2, 21 September 1992). That links the regulatory requirement to a manufacturer-prescribed technical procedure. The Directive therefore channels the “how” of compliance to the service bulletin rather than leaving it open to arbitrary methods.
• Implicit interaction with maintenance and operations rules: Although not stated in the AD text, an AD typically interacts with maintenance regulation (for example, maintenance release/certification obligations), operational rules (e.g. limitations on equipment and approved instrumentation), and aircraft continuing airworthiness requirements. The Directive expressly changes an operational limitation (prohibiting certain TCAS II modes) and prescribes a technical fix, so it will interact operationally with TCAS/ATC procedures and technically with maintenance approval frameworks. The supplied text, however, does not quote the specific maintenance or operations regulations; operators must consult their broader regulatory framework to see how compliance with this AD is recorded, certified and enforced.

Limits of the Directive’s stated interplays

• The text does not state alternative means of compliance, an explicit equivalency approval path, or an appeal process. The only explicit inter-instrument relationship is the recognition of earlier compliance under the original CASA Directive or FAA AD 93-04-02. Any further interaction (for example with national maintenance standards or continued airworthiness recordkeeping rules) is outside the text provided and would be governed by the relevant statutes and CASA procedural practice.

The Directive contains its own, compact amendment history in the text. The salient points in the supplied document are:

• Original issue: The Directive’s original issue is recorded as having become effective on 27 May 1993. The Background section states: “The original issue of this Directive became effective on 27 May 1993.”
• This Amendment (AD/RAD/51 Amdt 1): The document is titled AD/RAD/51 Amdt 1 and is dated 10/2008 in the header. The signature block shows the delegate and date: “James Coyne, Delegate of the Civil Aviation Safety Authority” dated 6 August 2008. The Amendment text states “This Amendment becomes effective on 25 September 2008.”
• Purpose of the Amendment: The Background explains that this Amendment results from “a request from industry to identify the affected transponder,” and that the Amendment “adds P/N 622-9210-002 to the applicability statement, updates the list of affected aircraft and corrects minor typographical errors.” That records a narrow administrative change rather than an alteration to the fundamental safety measure or compliance timeline in substance.
• Relation to FAA AD: The text refers to FAA AD 93-04-02 (and Amendment 39-8504) both in a note and in the operative text: prior accomplishment in accordance with FAA AD 93-04-02 discharges the new listed requirements. The Amendment therefore records alignment with the FAA action and recognises prior FAA-led compliance.
• Revisions to required documents: Requirement 2 mandates modification in accordance with Collins Service Bulletin TDR-94/94D-34-6 Revision 2, dated 21 September 1992. The Revision 2 dating indicates the technical remedy originates from the early 1990s and that the Amendment channels compliance to that specific revision. The Amendment itself is, by its nature, an update to the earlier AD to add the part number and correct errors; it does not change the identity of the corrective action already set out.

Taken together, the Amendment history shows a 1993 original AD followed by a 2008 Amendment to add a specific part number and update aircraft lists, with an effective date in late September 2008 and a narrow expressed administrative purpose.

The supplied Directive contains no litigation history. The text does not reference any court decisions, appeals, legal challenges, or contested administrative reviews. There is no mention of judicial proceedings, stay applications, or litigious objections in the material provided.

What the absence implies for users of this note

• With no litigation referenced in the Directive, there is no case law or judicial interpretation supplied that clarifies ambiguous points in the AD text. Any interpretative disputes about scope, mandatory language, or the adequacy of a particular compliance method (beyond the express prior-compliance carve-out) would need to be resolved through CASA guidance, regulatory procedures or, ultimately, judicial fora , but there is no record of such activity in the document presented here.
• Practitioners wanting litigation precedent or case law on this specific AD will need to seek sources outside this Directive; the Directive itself provides no litigation cues.

The Directive’s brevity and phrasing conceal several practical pitfalls. These are points that often give rise to operational or compliance uncertainty and merit explicit attention.

• “Installed on, but not limited to”: The applicability table lists several aeroplane series but prefaces the list with “installed on, but not limited to.” That means the named aircraft are examples and operators must check the transponder P/N rather than rely solely on aircraft type. Failure to confirm the actual P/N 622-9210-002 in the aircraft could lead to inadvertent non-compliance.
• Exact placard wording and sizing: Requirement 1 prescribes the precise placard wording and a minimum letter height of 25 mm. Small deviations from the prescribed text or letter height might be non‑compliant. The Directive also specifies placement “within the pilot’s clear view on the instrument panel.” That requires judgement about pilot sightlines; operators should ensure the placard location does not obscure instruments and meets the stated requirement.
• Interim versus permanent measures and sequencing: The Directive makes clear that the placard is an interim measure and “is no longer necessary after this Modification is incorporated.” Operators who omit the placard and rely solely on a plan to modify later risk being non-compliant during the interim period unless they can show prior compliance. Conversely, operators who install the placard may remove it only after completing the specified software modification.
• Service Bulletin revision specificity: Requirement 2 requires modification “in accordance with the Accomplishment Instructions of Collins Service Bulletin TDR-94/94D-34-6 Revision 2 dated 21 September 1992.” That binds compliance to that specific revision. Using an earlier revision, an unofficial modification, or a different supplier’s procedure may not satisfy the Directive unless prior compliance under the original AD or FAA AD is demonstrable. Verify the revision number and date carefully.
• Prior compliance carve-out: The text allows for non-application “If not previously accomplished in accordance with the original issue of this Directive or United States FAA AD 93-04-02.” Operators must retain documentary proof of prior compliance under either instrument. Absent clear records, demonstrating prior compliance may be problematic.
• Deadlines are short: The Amendment becomes effective on 25 September 2008; Requirement 1 must be complied with prior to 25 October 2008 and Requirement 2 prior to 1 December 2008. Those compliance windows are narrow. Planning and scheduling with approved maintenance organisations must be prompt.
• Typographical errors referenced: The Background notes that the Amendment corrects minor typographical errors. Practitioners should be mindful that the original document or earlier versions might contain typographical anomalies (the supplied text itself contains the word “loose” where “lose” is intended in the Background,this is not a substantive change but an example of the kind of typographical issue the Amendment claims to correct).
• Scope of “TCAS II mode” language: The placard’s prohibition reads “OPERATION OF TCAS II IN ANY MODE OTHER THAN THE ‘TA ONLY’ MODE IS PROHIBITED.” The Directive does not define “mode” within the text. Practitioners should ensure they understand which TCAS II modes are used in their fleet and confirm that the aircraft’s operational procedures and pilot training align with the restriction until the software modification is completed.
• Absence of penalties and enforcement detail: The Directive lacks an internal penalties section. Operators should not read the silence as permissive; rather they should treat the AD as a mandatory airworthiness requirement and consult CASA for enforcement expectations and recordkeeping obligations.
• Non-exhaustive aircraft list plus new part number: The Amendment’s primary administrative change is to add the specific P/N to the applicability. This increases the chance that an aircraft not previously thought affected may now be captured by the AD, particularly where swapping of equipment has occurred in fleet maintenance histories.

The Directive sets out a clear two-step compliance pathway and identifies criteria for pre-existing compliance. Below are concretely actionable steps, drawn directly from the Directive text and phrased for operational use.

1. Verify applicability

   • Inspect the aircraft to determine whether a Rockwell/Collins TDR-94D Mode S transponder with part number 622-9210-002 is installed. Do not rely solely on aircraft type lists; the Directive states the applicability as P/N 622-9210-002 and lists affected aeroplanes “installed on, but not limited to” the specified types.
   • If the transponder is not P/N 622-9210-002, this AD as written does not apply to that equipment. If the P/N matches, proceed.

2. Check for prior compliance documentation

   • Determine whether the placard installation or the software modification has already been performed in accordance with the original issue of AD/RAD/51 or FAA AD 93-04-02. The Directive states the Requirements apply “If not previously accomplished in accordance with the original issue of this Directive or United States Federal Aviation Administration (FAA) AD 93-04-02.”
   • Retain documentary proof (maintenance logbook entries, service-release certificates, copies of the earlier AD compliance work) that show the relevant work was done in accordance with those earlier instruments.

3. If prior compliance is not established, install the placard (Requirement 1)

   • Fabricate a placard carrying the exact words: OPERATION OF TCAS II IN ANY MODE OTHER THAN THE “TA ONLY” MODE IS PROHIBITED
   • Use letters at least 25 mm in height.
   • Install the placard within the pilot’s clear view on the instrument panel.
   • Deadline: complete this installation prior to 25 October 2008 (the Directive’s Compliance statement for Requirement 1).

4. Schedule and perform the software modification (Requirement 2)

   • Arrange for the transponder software modification to be carried out in accordance with the Accomplishment Instructions of Collins Service Bulletin TDR-94/94D-34-6 Revision 2 dated 21 September 1992. The Directive requires conformity with that specific revision of the service bulletin.
   • Use appropriately authorised maintenance personnel or an organisation competent to carry out avionics software changes and to certify the work in your jurisdiction.
   • Deadline: the software modification must be incorporated prior to 1 December 2008.

5. After modification

   • Once the software modification required by Requirement 2 is incorporated, the Directive states that the placard mandated by Requirement 1 “is no longer necessary.” Document the completion of the service-bulletin work, update the aircraft maintenance records, and remove the placard only after the modification has been fully incorporated and certified.
   • File the modification records in the aircraft’s continuing airworthiness documentation.

6. Recordkeeping and audit readiness

   • Maintain records showing the P/N verification, placard fabrication and installation (if applicable), and service-bulletin modification completion (including reference to Collins Service Bulletin TDR-94/94D-34-6 Rev 2 and evidence of the Accomplishment Instructions having been followed).
   • Retain any evidence that earlier compliance under the original AD or FAA AD was performed, in case of audit by CASA or other relevant authority.

7. Practical maintenance points

   • Verify the Service Bulletin revision number and date carefully (Revision 2, 21 September 1992). Use the Accomplishment Instructions in that revision to execute the modification; earlier revisions may not meet the Directive’s stipulation.
   • Coordinate scheduling promptly given the short compliance windows set by the Directive: Requirement 1 prior to 25 October 2008 and Requirement 2 prior to 1 December 2008.
   • If the operator wishes to clarify whether some other action or alternative means of compliance would be acceptable, consult CASA. The Directive itself recognises only prior compliance under the original CASA Directive or the FAA AD as discharging the requirements.

8. Operational compliance in the interim

   • Until the software modification is certified, ensure flight crews are aware of the prohibition on operating TCAS II in modes other than “TA only,” and check cockpit configurations to ensure the restriction is physically enforced (the placard is intended to assist with that). Training or briefing should be documented.

9. Reference the effective and signature dates for compliance planning

   • The Amendment becomes effective on 25 September 2008, the delegate signed on 6 August 2008, and the original AD was effective 27 May 1993. Use these dates to contextualise timelines and confirm whether any earlier compliance might meet the Directive’s requirements.

Following these steps will align an operator’s technical and documentary position with the Directive as drafted. If there is any doubt about the sufficiency of earlier work or the acceptability of alternative means of compliance, contact CASA for formal guidance and keep contemporaneous records of all contacts and approvals.