{"id":"F2006B06528","name":"AD/RAD/73 - Rockwell Collins CTL-92 Transponder Control Panel","slug":"ad-rad-73-rockwell-collins-ctl-92-transponder-control-panel","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":48174,"registerId":"commonwealth-F2006B06528-current","compilationNumber":null,"startDate":"2026-04-02","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/RAD/73 - Rockwell Collins CTL-92 Transponder Control Panel","content":"COMMONWEALTH OF AUSTRALIA (Civil Aviation Regulations 1998), PART 39 \\- 107 CIVIL AVIATION SAFETY AUTHORITY\n\nSCHEDULE OF AIRWORTHINESS DIRECTIVES\n\n![](image.001.png)  \n![](image.002.png)  \nRadio Communication and Navigation Equipment\n\nAIRWORTHINESS DIRECTIVE\n\n![](image.002.png)\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 CAR 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.003.png)AD/RAD/73 Rockwell Collins CTL-92 Transponder Control Panel\n\n  \n10/2001\n\nDM\n\nApplicability: Rockwell Collins CTL-92 Transponder Control Panel Part Numbers 622-6523-204, 622-6523-205, 622-6523-206, 622-6523-207, and 622-6523-208 (serial numbers as\n\nspecified in Rockwell Collins Service Bulletin \\[SB\\] 33 \\[CTL-92-34-33\\], dated 5 April 2001).\n\nNote 1: These CTL-92 transponder control panels are known be installed in, but not limited to, the following aircraft:\n\nAerospatiale ATR42 and ATR72 series aeroplanes Saab Aircraft Models 340B and SF340A aeroplanes Embraer EMB-120 series aeroplanes\n\nde Havilland DHC-8 series aeroplanes\n\nRaytheon Models C90A, B200, 350, and 1900D aeroplanes.\n\nRequirement: 1. Modify the altitude encoder inputs of the CTL-92 transponder control panels in accordance with the Accomplishment Instructions section of Rockwell Collins SB 33 (CTL-92-34-33).\n\n2. CTL-92 Transponder Control Panel, with the part number serial number combination listed in SB 33 (CTL-92-34-33), may not be installed on any aeroplane unless it has been modified in accordance with Requirement 1.\n\nNote 2: FAA AD 2001-15-17 Amdt 39-12352 refers.\n\nCompliance: For Requirement 1 \\- Within the next 10 hours time-in-service from the effective date of this Directive.\n\nFor Requirement 2 \\- As of the effective date of this Directive.\n\nThis Airworthiness Directive becomes effective on 20 August 2001.\n\nBackground: The United States Federal Aviation Administration has received reports of erroneous Mode C and Mode S random transponder transmissions from aircraft equipped with Gillham encoded altitude sources and certain Rockwell Collins CTL-92 Transponder Control Panels. Rockwell Collins introduced new A6 circuit cards for these transponder control panels in September 2000.\n\nCOMMONWEALTH OF AUSTRALIA (Civil Aviation Regulations 1998), PART 39 \\- 107 CIVIL AVIATION SAFETY AUTHORITY\n\nSCHEDULE OF AIRWORTHINESS DIRECTIVES\n\n![](image.004.png)These circuit cards exhibit reduced ground integrity in the area of the Gillham input processing. This results in noise generation within the CTL-92 control panels that the transponder can interpret and transmit as a random altitude. Air traffic control and traffic alert and collision avoidance system (TCAS)-equipped aircraft can interpret these erroneous random altitudes as valid altitudes.\n\nThis Directive requires modification of the altitude encoder inputs of the CTL-92. This action is intended to prevent erroneous altitude interpretations, which could result in reduced vertical separation or unsafe TCAS resolution advisories.\n\n![Signature of Eugene Paul Holzapfel Delegate of the Civil Aviation Safety Authority](image.005.png)  \n\nEugene Paul Holzapfel\n\nDelegate of the Civil Aviation Safety Authority 6 August 2001\n\n![](image.002.png)  \n\nThe above AD is notified in the Commonwealth of Australia Gazette on 15 August 2001.","sortOrder":0}],"analysis":{"flash_summary":{"complexity_score":3,"scope_assessment":{"changed":false,"description":"The AD remains narrowly focused on correcting a specific unsafe condition in certain CTL-92 transponder control panels (faulty Gillham input processing on A6 circuit cards). It does not expand beyond that technical remedy: it prescribes a modification, bans installation of unmodified affected units, and sets an urgent compliance deadline. The scope therefore aligns with the directive's original safety purpose and has not grown beyond that aim."},"complexity_factors":["Short document limited to a single affected component and specific part-number/serial-number combinations","Two clear operative requirements (modify per SB; prohibit installation unless modified)","Single, short compliance window (10 hours time-in-service) and immediate installation ban","Dependence on an external technical document (Rockwell Collins SB 33) for procedural detail","Cross-reference to FAA AD 2001-15-17 and Civil Aviation Regulations subregulation 39.1(1)","Limited definitional complexity and few conditional exceptions"],"plain_english_summary":"**What this directive does (mechanics)**\n\n- Applies to Rockwell Collins CTL-92 transponder control panels with specific part-number/serial-number combinations listed in Rockwell Collins Service Bulletin (SB) 33 (CTL-92-34-33). The SB lists the affected serial numbers; the AD itself names the relevant part numbers. (See \"Applicability\".)\n\n- Requires operators or maintenance organisations to modify the altitude-encoder input circuitry of those CTL-92 units exactly as described in the \"Accomplishment Instructions\" of Rockwell Collins SB 33. (Requirement 1.)\n\n- Prohibits installation of any CTL-92 unit with the affected part-number/serial-number combination on an aircraft unless it has been modified as required. (Requirement 2.)\n\n- Sets the compliance deadline: the modification must be carried out within the next 10 hours time-in-service from the directive's effective date. The installation ban applies from the effective date. (Compliance.)\n\n**Who is affected**\n\n- Aircraft operators and owners that have CTL-92 transponder control panels with the listed part numbers and serial numbers.\n- Aircraft maintenance organisations and licensed aircraft engineers who must perform the modification and certify the work.\n- Organisations that install or supply CTL-92 panels — they must not fit an unmodified, affected unit to an aircraft.  \n- Rockwell Collins (as the supplier of the service bulletin and originator of the corrective instructions) is the technical source for the fix.\n\n**Why it matters (official rationale)**\n\n- The FAA received reports that some CTL-92 control panels introduced with new A6 circuit cards had reduced ground integrity on the Gillham altitude input. That reduction can allow electrical noise to be interpreted by the transponder as a random altitude. Erroneous altitude reports can be transmitted in Mode C/Mode S and may be interpreted as valid by air traffic control or TCAS-equipped aircraft, creating the risk of incorrect vertical-separation information or unsafe TCAS advisories. The AD requires the modification to prevent those erroneous altitude transmissions. (Background and Requirement sections.)\n\n**Practical consequences, costs and risks**\n\n- Who pays: aircraft operators pay the direct costs (parts and labour) to implement the modification and any aircraft downtime. Maintenance organisations receive the work and must allocate technician time. (Requirement and Compliance.)\n\n- Time and operational cost: the AD imposes a tight compliance window (within 10 hours time-in-service), which may force operators to schedule immediate maintenance, potentially incurring AOG (aircraft-on-ground) disruption or rearranged flights.\n\n- Implementation burden: the modification must follow the manufacturer's SB instructions; it requires access to the SB, qualified personnel, and any prescribed parts or wiring changes. If parts or instructions are scarce, that creates scheduling risk and potential delays.\n\n- Incentives and concentrated benefits: maintenance shops authorised or experienced to carry out this specific Rockwell Collins SB may see a concentrated boost in demand for retrofit work. Rockwell Collins benefits from being the source of the fix (they supply the SB and likely parts/support).\n\n- Substitution and operational choices: operators may choose to delay installing replacement CTL-92 units that are unmodified, or to source alternate transponders if modification capacity or cost makes that preferable. The AD forbids installing an affected unmodified unit, so the practical choice is modify or not install.\n\n- Record-keeping and compliance monitoring: operators must ensure compliance within the 10-hour window and keep maintenance records demonstrating the SB procedure was carried out; regulators and certificated engineers decide acceptability of the work (Requirement & Compliance).\n\n**Trade-offs and implementation risk**\n\n- Trade-off: immediate safety risk mitigation versus near-term operational disruption and retrofit cost. The AD prioritises removing the risk of erroneous altitude transmissions quickly.\n\n- Implementation risk: if the SB is unclear or requires special parts/tools, work may be delayed or executed incorrectly; this increases the chance of non-compliance or repeated work. The AD is prescriptive: it directs compliance with the SB instructions, which centralises technical decision-making with Rockwell Collins and certified engineers.\n\n**Effect on market behaviour and private enterprise**\n\n- The AD imposes a regulatory requirement on private operators to modify equipment they own or control, so private costs increase for those affected units.\n\n- Small maintenance providers may be edged out if they lack the capability to perform the specific modification; certified providers able to perform the SB will capture the work.\n\n- Competition among avionics suppliers is not directly altered by the AD, but demand for retrofit services and possible replacement equipment may shift temporarily.\n\n**Summary statements (plain)**\n\n- The AD requires a manufacturer-prescribed modification to the altitude-encoder input of specific Rockwell Collins CTL-92 transponder control panels within a short timeframe and bans installation of affected units unless modified. Operators pay for the fix, maintenance providers perform it, and the action is intended to stop erroneous altitude transmissions that could affect ATC and TCAS systems.\n\n(References in the directive: Applicability, Requirement 1–2, Compliance, Background, and Rockwell Collins SB 33.)"},"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 Airworthiness Directive maintains its original narrow scope. It addresses a specific safety defect in a specific piece of equipment (Rockwell Collins CTL-92 Transponder Control Panels) and does not expand beyond that technical remediation. The document remains focused on the single unsafe condition described in the background section."},"complexity_factors":["Single, specific technical subject matter (one transponder model)","Only 2 operational requirements with clear compliance deadlines","Minimal cross-referencing (only one external service bulletin and one FAA AD)","No nested exceptions or conditional logic","Straightforward applicability section with explicit part numbers","Short document (approximately 1 page of substantive content)","Clear, sequential structure: Applicability → Requirement → Compliance → Background"],"plain_english_summary":"This CASA safety order requires owners/operators of specified ATR, Saab, Embraer, de Havilland Dash‑8 and Raytheon (Beechcraft) aircraft to modify Rockwell Collins CTL‑92 transponder control panels (P/Ns 622‑6523‑204 through ‑208) to correct a fault that can produce false altitude readings. Mods must follow Rockwell Collins Service Bulletin 33 within 10 flight hours of 20 Aug 2001, and unmodified panels are banned thereafter to prevent wrong-altitude reports and collision risk."}},"importantCases":[],"_links":{"self":"/api/acts/ad-rad-73-rockwell-collins-ctl-92-transponder-control-panel","history":"/api/acts/ad-rad-73-rockwell-collins-ctl-92-transponder-control-panel/history","analysis":"/api/acts/ad-rad-73-rockwell-collins-ctl-92-transponder-control-panel/analysis","conflicts":"/api/acts/ad-rad-73-rockwell-collins-ctl-92-transponder-control-panel/conflicts","importantCases":"/api/acts/ad-rad-73-rockwell-collins-ctl-92-transponder-control-panel/important-cases","documents":"/api/acts/ad-rad-73-rockwell-collins-ctl-92-transponder-control-panel/documents"}}