# AD 2001-15-17: Transponder Control Panels

- Type: Airworthiness directive
- Status: Current
- Products: Bombardier ATR42-200, ATR42-300, ATR42-320, ATR42-500, ATR72-101, ATR72-102, ATR72-201, ATR72-202, ATR72-211, ATR72-212, ATR72-212A, DHC-8-101 and 21 more
- Effective: August 20, 2001
- Published: July 31, 2001, 66 FR 39431–39433
- Issued: July 19, 2001
- Issued as: Final rule; request for comments
- Superseded by: Nothing supersedes this AD
- Product type: Appliance
- Amendment: 39-12352
- Docket: 2001-CE-22-AD
- Registered aircraft: 1,646 may be affected, by airframe or engine model (OpenAirDocs)
- Official PDF: https://openairdocs.org/files/sha256/a9/f7/a9f7e9197ed2397ce85453f57d99cb076e0902f58d12aaae4f3b5f4fd658b27a (from https://www.govinfo.gov/content/pkg/FR-2001-07-31/pdf/01-18707.pdf)
- Federal Register: https://www.federalregister.gov/documents/2001/07/31/01-18707/airworthiness-directives-rockwell-collins-inc-ctl-92-transponder-control-panels
- FAA DRS: https://drs.faa.gov/browse/excelExternalWindow/BF695D46A556708D86256A9A005CF16C.0001
- DRS record last changed: January 21, 2026
- Page: https://openairdocs.org/ad/2001-15-17

## Summary

This amendment adopts a new airworthiness directive (AD) that applies to certain Rockwell Collins, Inc. (Rockwell Collins) CTL-92 transponder control panels that are installed on aircraft. This AD requires you to modify the altitude encoder inputs of the CTL-92 transponder control panels. This AD is the result of reports of noise generation within the CTL-92 transponder control panels that the transponder can interpret and transmit as a random altitude. Air traffic control (ATC) and traffic alert and collision avoidance system (TCAS)-equipped aircraft can then interpret these erroneous random altitudes as valid altitudes. The actions specified by this AD are intended to prevent such erroneous altitude interpretations, which could result in reduced vertical separation or unsafe TCAS resolution advisories.

## The airworthiness directive

### Adoption of the Amendment

Accordingly, under the authority delegated to me by the Administrator, the Federal Aviation Administration amends part 39 of the Federal Aviation Regulations (14 CFR part 39) as follows:

1. The authority citation for part 39 continues to read as follows:

2. FAA amends § 39.13 by adding a new airworthiness directive (AD) to read as follows:

2001-15-17 Rockwell Collins, Inc.: Amendment 39-12352; Docket No. 2001-CE-22-AD.

### (a)

  (a) What airplanes are affected by this AD? This AD applies to 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 specified in Rockwell Collins Service Bulletin 33 (CTL-92-34-33), dated April 5, 2001), that are installed in aircraft. These CTL-92 transponder control panels are installed in, but not limited to, the following aircraft that are certificated in any category:

  (1) Aerospatiale ATR42 and ATR72 series airplanes;

  (2) Saab Aircraft Models 340B and SF340A airplanes;

  (3) Embraer EMB-120 series airplanes;

  (4) deHavilland DHC-8 series airplanes; and

  (5) Raytheon Models C90A, B200, 350, and 1900D airplanes.

  (b) Who must comply with this AD ? Anyone who wishes to operate an aircraft equipped with one of the affected CTL-92 transponder control panels must comply with this AD.

  (c) What problem does this AD address ? The actions specified by this AD are intended to prevent erroneous altitude interpretations, which could result in reduced vertical separation or unsafe traffic alert and collision avoidance system (TCAS) resolution advisories.

  (d) What must I do to address this problem? To address this problem, you must accomplish the following actions:


| Action | Compliance time | Procedures |
| --- | --- | --- |
| (1) Modify the altitude encoder inputs of the CTL-92 transponder control panels | Within the next 10 hours time-in-service (TIS) after August 20, 2001 (the effective date of this AD) | Modify in accordance with the Accomplishment Instructions section of Rockwell Collins Service Bulletin 33 (CTL-92-34-33), dated April 5, 2001. |
| (2) Do not install, on any aircraft, an affected CTL-92 transponder control panel that has not been modified as required by paragraph (d)(1) of this AD | As of August 20, 2001 (the effective date of this AD) | Modify in accordance with the Accomplishment Instructions section of Rockwell Collins Service Bulletin 33 (CTL-92-34-33), dated April 5, 2001. |

  (e) Can I comply with this AD in any other way? You may use an alternative method of compliance or adjust the compliance time if:

  (1) Your alternative method of compliance provides an equivalent level of safety; and

  (2) The Manager, Wichita Aircraft Certification Office, approves your alternative. Send your request through an FAA Principal Maintenance Inspector, who may add comments and then send it to the Manager, Wichita Aircraft Certification Office.

Note:

This AD applies to any aircraft with the equipment installed as identified in paragraph (a) of this AD, regardless of whether the aircraft has been modified, altered, or repaired in the area subject to the requirements of this AD. For aircraft that have been modified, altered, or repaired so that the performance of the requirements of this AD is affected, the owner/operator must request approval for an alternative method of compliance in accordance with paragraph (e) of this AD. The request should include an assessment of the effect of the modification, alteration, or repair on the unsafe condition addressed by this AD; and, if you have not eliminated the unsafe condition, specific actions you propose to address it.

  (f) Where can I get information about any already-approved alternative methods of compliance? You can contact Roger A. Souter, FAA, Wichita Aircraft Certification Office (ACO), 1801 Airport Road, Room 100, Wichita, Kansas 67209; telephone: (316) 946-4134; facsimile: (316) 946-4407, e-mail: roger.souter@faa.gov.

  (g) What if I need to fly the airplane to another location to comply with this AD? The FAA can issue a special flight permit under sections 21.197 and 21.199 of the Federal Aviation Regulations (14 CFR 21.197 and 21.199) to operate your airplane to a location where you can accomplish the requirements of this AD.

  (h) Are any service bulletins incorporated into this AD by reference? Actions required by this AD must be done in accordance Rockwell Collins Service Bulletin 33 (CTL-92-34-33), dated April 5, 2001. The Director of the Federal Register approved this incorporation by reference under 5 U.S.C. 552(a) and 1 CFR part 51. You can get copies from Rockwell Collins, Business and Regional Systems, 400 Collins Road Northeast, Cedar Rapids, Iowa 52498. You can look at copies at FAA, Central Region, Office of the Regional Counsel, 901 Locust, Room 506, Kansas City, Missouri, or at the Office of the Federal Register, 800 North Capitol Street, NW., suite 700, Washington, DC.

    (i) When does this amendment become effective? This amendment becomes effective on August 20, 2001.

## Rule preamble

### Dates

This AD becomes effective on August 20, 2001.

The Director of the Federal Register approved the incorporation by reference of certain publications listed in the regulation as of August 20, 2001.

The Federal Aviation Administration (FAA) must receive any comments on this rule on or before September 7, 2001.

### Addresses

Submit comments in triplicate to FAA, Central Region, Office of the Regional Counsel, Attention: Rules Docket No. 2001-CE-22-AD, 901 Locust, Room 506, Kansas City, Missouri 64106.

You may get the service information referenced in this AD from Rockwell Collins Inc., Business and Regional Systems, 400 Collins Road Northeast, Cedar Rapids, Iowa 52498. You may examine this information at FAA, Central Region, Office of the Regional Counsel, Attention: Rules Docket No. 2001-CE-22-AD, 901 Locust, Room 506, Kansas City, Missouri 64106; or at the Office of the Federal Register, 800 North Capitol Street, NW, suite 700, Washington, DC.

### For further information contact

Roger A. Souter, FAA, Wichita Aircraft Certification Office (ACO), 1801 Airport Road, Room 100, Wichita, Kansas 67209; telephone: (316) 946-4134; facsimile: (316) 946-4407; e-mail: roger.souter@faa.gov.

### Discussion

What Events Have Caused This AD?

The FAA 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.

These circuit cards exhibit reduced ground integrity in the area of the Gillham input processing. This results in noise generation within the CTL-92 transponder control panels that the transponder can interpret and transmit as a random altitude. Air traffic control (ATC) and traffic alert and collision avoidance system (TCAS)-equipped aircraft can then interpret these erroneous random altitudes as valid altitudes.

The following Rockwell Collins CTL-92 control unit part numbers are affected: 622-6523-204, 622-6523-205, 622-6523-206, 622-6523-207, and 622-6523-208.

These Rockwell Collins CTL-92 transponder control panels could be installed on, but not limited to, the following aircraft:

—Aerospatiale ATR42 and ATR72 series airplanes;

—Saab Aircraft Models 340B and SF340A airplanes;

—Embraer EMB-120 series airplanes;

—deHavilland DHC-8 series airplanes; and

—Raytheon Models C90A, B200, 350, and 1900D airplanes.

What Are the Consequences if the Condition Is Not Corrected?

Such erroneous altitude interpretations could result in reduced vertical separation or unsafe TCAS resolution advisories.

Is There Service Information That Applies to This Subject?

Rockwell Collins has issued Service Bulletin 33 (CTL-92-34-33), dated April 5, 2001. This service bulletin includes:

—Procedures for how to modify the altitude encoder inputs of these transponder control panels; and

—A list of part numbers and serial numbers of the affected CTL-92 transponder control panels.

The FAA's Determination and an Explanation of the Provisions of this AD What Has FAA Decided?

The FAA has reviewed all available information, including the service information referenced above, and determined that:

—The unsafe condition referenced in this document exists or could develop on type design aircraft that incorporate these Rockwell Collins CTL-92 transponder control panels;

—The actions specified in the previously-referenced service information should be accomplished on the affected Rockwell Collins CTL-92 transponder control panels; and

—AD action should be taken in order to correct this unsafe condition.

What Does This AD Require?

This AD requires you to modify the altitude encoder inputs of the CTL-92 transponder control panels. Rockwell Collins Service Bulletin 33 (CTL-92-34-33), dated April 5, 2001, specifies the exact part numbers and serial numbers that are affected and includes procedures on how to modify these transponder control panels.

Will I Have the Opportunity To Comment Prior to the Issuance of the Rule?

Because the unsafe condition described in this document could result in reduced vertical separation or unsafe TCAS resolution advisories, FAA finds that notice and opportunity for public prior comment are impracticable. Therefore, good cause exists for making this amendment effective in less than 30 days.

### Comments Invited

How Do I Comment on This AD?

Although this action is in the form of a final rule and was not preceded by notice and opportunity for public comment, we invite your comments on the rule. You may submit whatever written data, views, or arguments you choose. You need to include the rule's docket number and submit your comments in triplicate to the address specified under the caption ADDRESSES. We will consider all comments received on or before the closing date specified above. We may amend this rule in light of comments received. Factual information that supports your ideas and suggestions is extremely helpful in evaluating the effectiveness of the AD action and determining whether we need to take additional rulemaking action.

Are There Any Specific Portions of the AD I Should Pay Attention to?

The FAA specifically invites comments on the overall regulatory, economic, environmental, and energy aspects of the rule that might suggest a need to modify the rule. You may examine all comments we receive before and after the closing date of the rule in the Rules Docket. We will file a report in the Rules Docket that summarizes each FAA contact with the public that concerns the substantive parts of this AD.

We are reviewing the writing style we currently use in regulatory documents, in response to the Presidential memorandum of June 1, 1998. That memorandum requires federal agencies to communicate more clearly with the public. We are interested in your comments on whether the style of this document is clear, and any other suggestions you might have to improve the clarity of FAA communications that affect you. You can get more information about the Presidential memorandum and the plain language initiative at http://www.plainlanguage.gov.

How Can I Be Sure FAA Receives My Comment?

If you want us to acknowledge the receipt of your comments, you must include a self-addressed, stamped postcard. On the postcard, write “Comments to Docket No. 2001-CE-22-AD.” We will date stamp and mail the postcard back to you.

### Regulatory Impact

Does This AD Impact Various Entities?

These regulations will not have a substantial direct effect on the States, on the relationship between the national Government and the States, or on the distribution of power and responsibilities among the various levels of government. Therefore, FAA has determined that this final rule does not have federalism implications under Executive Order 13132.

Does This AD Involve a Significant Rule or Regulatory Action?

The FAA has determined that this regulation is an emergency regulation that must be issued immediately to correct an unsafe condition in aircraft, and is not a significant regulatory action under Executive Order 12866. It has been determined further that this action involves an emergency regulation under DOT Regulatory Policies and Procedures (44 FR 11034, February 26, 1979). If it is determined that this emergency regulation otherwise would be significant under DOT Regulatory Policies and Procedures, a final regulatory evaluation will be prepared and placed in the Rules Docket (otherwise, an evaluation is not required). A copy of it, if filed, may be obtained from the Rules Docket.

## Affected data sheets (6) (OpenAirDocs)

The type certificate data sheets whose models the AD names.

- [TCDS A13NM](https://openairdocs.org/tcds/A13NM): De Havilland Aircraft of Canada Limited; names 12 of 16 models: DHC-8-101, DHC-8-102, DHC-8-103, DHC-8-106, DHC-8-201, DHC-8-202, DHC-8-301, DHC-8-311…
- [TCDS A53EU](https://openairdocs.org/tcds/A53EU): ATR – GIE Avions de Transport Régional; names 11 of 11 models: ATR72-202, ATR72-101, ATR72-212A, ATR72-212, ATR42-300, ATR42-320, ATR72-211, ATR72-102…
- [TCDS A31SO](https://openairdocs.org/tcds/A31SO): Embraer S.A.; names 5 of 5 models: EMB-120ER, EMB-120, EMB-120RT, EMB-120FC, EMB-120QC
- [TCDS 3A20](https://openairdocs.org/tcds/3A20): Textron Aviation Inc.; names 1 of 22 models: C90A
- [TCDS A24CE](https://openairdocs.org/tcds/A24CE): Textron Aviation Inc.; names 1 of 37 models: 1900D
- [TCDS A52EU](https://openairdocs.org/tcds/A52EU): Saab AB; names 1 of 2 models: SAAB 340B

## Registered aircraft it may apply to (OpenAirDocs)

Matched by airframe and engine model; the AD's applicability may narrow it by serial number, part number or equipment.

- Aircraft: 1,646 (1,646 by airframe model, 0 by engine model)
- Makers: Cessna 543, Beech 446, Raytheon 383, Bombardier 57, Saab-Scania 42, Embraer 41, Dehavilland 28, Aerospatiale/Aeritalia 17, Atr-Gie Avions De Trnsp Rgnl 15, Saab 15

Models with the most aircraft:

- [Cessna 340A](https://openairdocs.org/model/cessna-340a): 543 aircraft (airframe model)
- [Beech B200](https://openairdocs.org/model/beech-b200): 281 aircraft (airframe model)
- [Raytheon B200](https://openairdocs.org/model/raytheon-b200): 206 aircraft (airframe model)
- [Raytheon C90A](https://openairdocs.org/model/raytheon-c90a): 155 aircraft (airframe model)
- [Beech C90A](https://openairdocs.org/model/beech-c90a): 125 aircraft (airframe model)
- [Saab-Scania SAAB 340B](https://openairdocs.org/model/saab-scania-saab-340b): 42 aircraft (airframe model)
- [Beech 1900D](https://openairdocs.org/model/beech-1900d): 40 aircraft (airframe model)
- [Embraer EMB-120ER](https://openairdocs.org/model/embraer-emb-120er): 38 aircraft (airframe model)
- [Bombardier DHC-8-402](https://openairdocs.org/model/bombardier-dhc-8-402): 26 aircraft (airframe model)
- [Raytheon 1900D](https://openairdocs.org/model/raytheon-1900d): 22 aircraft (airframe model)
- [Dehavilland DHC-8-202](https://openairdocs.org/model/dehavilland-dhc-8-202): 17 aircraft (airframe model)
- [Bombardier DHC-8-315](https://openairdocs.org/model/bombardier-dhc-8-315): 15 aircraft (airframe model)
- [Saab SAAB 340B](https://openairdocs.org/model/saab-saab-340b): 15 aircraft (airframe model)
- [Bombardier DHC-8-202](https://openairdocs.org/model/bombardier-dhc-8-202): 14 aircraft (airframe model)
- [Atr-Gie Avions De Trnsp Rgnl ATR 72-212A](https://openairdocs.org/model/atr-gie-avions-de-trnsp-rgnl-atr-72-212a): 14 aircraft (airframe model)
- [Hawker Beechcraft B200](https://openairdocs.org/model/hawker-beechcraft-b200): 12 aircraft (airframe model)
- [Aerospatiale/Aeritalia ATR 42-300](https://openairdocs.org/model/aerospatiale-aeritalia-atr-42-300): 12 aircraft (airframe model)
- [Aerospatiale ATR 72-212](https://openairdocs.org/model/aerospatiale-atr-72-212): 9 aircraft (airframe model)
- [Saab-Fairchild 340A](https://openairdocs.org/model/saab-fairchild-340a): 8 aircraft (airframe model)
- [Atr-Gie Avions De Trnsp Region ATR42-500](https://openairdocs.org/model/atr-gie-avions-de-trnsp-region-atr42-500): 6 aircraft (airframe model)

All 47 models: https://openairdocs.org/ad/2001-15-17/models.md
Every aircraft: https://openairdocs.org/ad/2001-15-17/aircraft.md

No proposed rule in this release led to it. Its text cites no advisory circulars or STCs.

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