01-27665. Airworthiness Directives; Rockwell Collins TDR-94 and TDR-94D Mode S Transponders

AGENCY:

Federal Aviation Administration, DOT.

ACTION:

Notice of proposed rulemaking (NPRM).

SUMMARY:

This document proposes to adopt a new airworthiness directive (AD) that would apply to certain Rockwell Collins TDR-94 and TDR-94D Mode S transponders that derive altitude information from a Gillham (gray code) encoded pressure altitude source and are installed on airplanes. The proposed AD would require you to have the unit modified to prevent erroneous altitude reporting. The proposed AD is the result of reports that erroneous altitude resolutions could occur when the affected transponders are utilized in areas with other airplanes equipped with certain aircraft collision avoidance system (ACAS) or traffic alert and collision avoidance system (TCAS) configurations. The actions specified by the proposed AD are intended to prevent these erroneous altitude resolutions from causing a reduction in the intended ACAS or TCAS Change 7 separation margins. Such a condition could result in air traffic control or the pilot making flight decisions that put the airplane in unsafe flight conditions.

DATES:

The Federal Aviation Administration (FAA) must receive any comments on the rule on or before January 11, 2002.

ADDRESSES:

Submit comments to FAA, Central Region, Office of the Regional Counsel, Attention: Rules Docket No. 2000-CE-32-AD, 901 Locust, Room 506, Kansas City, Missouri 64106. You may view any comments at this location between 8 a.m. and 4 p.m., Monday through Friday, except Federal holidays.

You may obtain service information that applies to this proposed AD from Rockwell Collins Inc., Business and Regional Systems, 400 Collins Road Northeast, Cedar Rapids, Iowa 52498. You may also view this information at the Rules Docket at the address above.

FOR FURTHER INFORMATION CONTACT:

Roger A. Souter, FAA, Wichita Aircraft Certification Office (ACO), 1801 Airport Road, Room 100, Wichita, Kansas 67209; telephone: [phone]; facsimile: [phone]; e-mail: [e-mail].

SUPPLEMENTARY INFORMATION:

Comments Invited

How do I comment on the proposed AD? The FAA invites comments on this proposed 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. We may amend the proposed rule in light of comments received. Factual information that supports your ideas and suggestions is extremely helpful in evaluating the effectiveness of the proposed AD action and determining whether we need to take additional rulemaking action.

Are there any specific portions of the proposed AD I should pay attention to? We specifically invite comments on the overall regulatory, economic, environmental, and energy aspects of the proposed 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 the proposed AD.

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. 2000-CE-32-AD.” We will date stamp and mail the postcard back to you.

Discussion

What events have caused this AD? The FAA has received information that erroneous altitude resolutions could occur on certain Rockwell Collins TDR-94 and TDR-94D Mode S transponders installed in airplanes with Gillham (gray code) encoded sources. This information indicates that these transponders are utilized in areas with other airplanes equipped with certain aircraft collision avoidance system (ACAS) or traffic alert and collision avoidance system (TCAS) configurations. In these situations, the transponders could receive incorrect TCAS resolution advisories. This could result in a reduction in the intended ACAS or TCAS Change 7 minimum separation margins.

Gillham altitude sources have a 100-foot resolution. The affected transponder will set the altitude resolution status to indicate a 25-foot resolution when connected to a Gillham altitude source. For those units that have digital sources of altitude information, the altitude resolution status is set correctly.

These Rockwell Collins TDR-94 and TDR-94D Mode S transponders could be installed on, but not limited to, the following airplanes:

—Aerospatiale ATR42 series airplanes;

—deHavilland DHC-7 and DHC-8 series airplanes; and

—Short Brothers Models SD3-60 and SD3-60 SHERPA airplanes.

What are the consequences if the condition is not corrected? As described above, such erroneous altitude resolutions could cause a reduction in the intended ACAS or TCAS Change 7 separation margins and result in air traffic control or the pilot making flight decisions that put the airplane in unsafe flight conditions.

Relevant Service Information

Is there service information that applies to this subject? Rockwell Collins has issued Service Bulletin No. 17 (TDR-94/94D-34-17), dated February 8, 1999.

What are the provisions of this service bulletin? The service bulletin includes information on how to have the TDR-94 and TDR-94D Mode S transponders modified to prevent erroneous altitude reportings. This consists of:

—Converting the TDR-94 transponder from Collins part number (CPN) 622-9352-004 to CPN 622-9352-005; and

—Converting the TDR 94D transponder from CPN 622-9210-004 to CPN 622-9210-005.

Collins Product Information Letter No. 71, dated January 1999, references the service bulletin.

The FAA's Determination and an Explanation of the Provisions of the Proposed AD

What has FAA decided? After examining the circumstances and reviewing all available information related to the incidents described above, we have determined that:

—The unsafe condition referenced in this document exists or could develop on type design airplanes that incorporate Rockwell Collins TDR-94 (CPN 622-9352-004) and TDR-94D (CPN 622-9210-004) Mode S transponders and derive altitude information from a Gillham (gray code) encoded pressure altitude source;

—The actions specified in the previously-referenced service information should be accomplished on these airplanes with these Mode S transponders; and

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

What would the proposed AD require? This proposed AD would require you to have the actions of Rockwell Collins Service Bulletin No. 17 (TDR-94/94D-34-17), dated February 8, 1999, incorporated on any affected Mode S transponder that is installed on a type-certificated airplane where Gillham pressure altitude encoding sources are used.

Why is the proposed compliance time presented in calendar time instead of hours time-in-service (TIS)? The compliance of the proposed AD is presented in calendar time instead of hours TIS because the condition exists regardless of airplane operation. The erroneous altitude indications could occur regardless of the number of times and hours the airplane was operated or the age of the Mode S transponder. For these reasons, FAA has determined that a compliance based on calendar time should be utilized in the proposed AD in order to ensure that the unsafe condition is addressed in a reasonable time period on all airplanes that have an affected Rockwell Collins TDR-94 and TDR-94D Mode S transponder installed, and where Gillham pressure altitude encoding sources are used.

Cost Impact

How many airplanes would the proposed AD impact? We estimate that 1,400 affected Rockwell Collins TDR-94 and TDR-94D Mode S transponders could be installed on airplanes in the U.S. registry.

What would be the cost impact of the proposed AD on owners/operators of the affected airplanes? Rockwell Collins will cover all workhours and parts costs associated with this modification under warranty. The proposed AD would not impose any cost impact upon the owners/operators of any airplane incorporating one of the affected TDR-94 and TDR-94D Mode S transponders.

Regulatory Impact

Would this proposed AD impact various entities? The regulations proposed herein would 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, it is determined that this proposed rule would not have federalism implications under Executive Order 13132.

Would this proposed AD involve a significant rule or regulatory action? For the reasons discussed above, I certify that this action (1) is not a “significant regulatory action” under Executive Order 12866; (2) is not a “significant rule” under DOT Regulatory Policies and Procedures (44 FR 11034, February 26, 1979); and (3) if promulgated, will not have a significant economic impact, positive or negative, on a substantial number of small entities under the criteria of the Regulatory Flexibility Act. A copy of the draft regulatory evaluation prepared for this action has been placed in the Rules Docket. A copy of it may be obtained by contacting the Rules Docket at the location provided under the caption ADDRESSES.

List of Subjects in 14 CFR Part 39

• Air transportation
• Aircraft
• Aviation safety
• Safety

The Proposed Amendment

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

PART 39—AIRWORTHINESS DIRECTIVES

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

Authority: 49 U.S.C. 106(g), 40113, 44701.

§ 39.13

[Amended]

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

Rockwell Collins, Inc.: Docket No. 2000-CE-32-AD.

(a) What products are affected by this AD? This AD applies to TDR-94 Mode S transponders (Collins part number (CPN) 622-9352-004) and TDR-94D Mode S transponders (CPN 622-9210-004) that derive altitude information from a Gillham (gray code) encoded pressure altitude source and are installed on, but not limited to, the following airplanes that are certificated in any category:

(1) Aerospatiale ATR42 series airplanes;

(2) deHavilland DHC-7 and DHC-8 series airplanes; and

(3) Short Brothers Models SD3-60 and SD3-60 SHERPA airplanes.

(b) Who must comply with this AD? Anyone who wishes to operate any airplane with one of the affected TDR-94 or TDR-94D Mode S Transponders units installed must comply with this AD.

(c) What problem does this AD address? The actions specified by this AD are intended to prevent erroneous altitude resolutions from causing a reduction in the intended aircraft collision avoidance system (ACAS) or traffic alert and collision avoidance system (TCAS) Change 7 minimum separation margins. Such a condition could result in air traffic control or the pilot making flight decisions that put the airplane in unsafe flight conditions.

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

Action	Compliance time	Procedures
(1) Determine whether the altitude information from any TDR-94 Mode S transponder (CPN 622-9352-004) or TDR-94D Mode S transponder (CPN 622-9210-004) is derived from a digital air data source or a Gillham (gray code) encoded source	Within the next 3 months after the effective date of this AD	As specified in Rockwell Collins Service Bulletin No. 17 (TDR-94/94D-34-17), dated February 8, 1999. Collins Product Information Letter No. 71, dated January 1999, references the service bulletin.
(2) If the altitude information is derived from a Gillham (gray code) encoded source, have the unit modified to prevent erroneous altitude reporting. The modification encompasses converting the TDR-94 transponder from Collins part number (CPN) 622-9352-004 to CPN 622-9352-005; and converting the TDR 94D transponder from CPN 622-9210-004 to CPN 622-9210-005	At the next transponder check required by 14 CFR 91.413 that occurs 3 months after the effective date of this AD or within the next 9 months after the effective date of this AD, whichever occurs first	In accordance with Rockwell Collins Service Bulletin No. 17 (TDR-94/94D-34-17), dated February 8, 1999. Collins Product Information Letter No. 71, dated January 1999, references the service bulletin.
(3) If the altitude information from all affected transponders is derived from a digital air data source, no modification action is required by this AD	Not applicable	Not applicable.
(4) Do not install any TDR-94 Mode S transponder (CPN 622-9352-004) or TDR-94D Mode S transponder (CPN 622-9210-004) on any airplane if the altitude information is derived from a Gillham (gray code) encoded source, unless the modification required by paragraph (d)(2) of this AD is incorporated	As of the effective date of this AD	Accomplish the modification in accordance with Rockwell Collins Service Bulletin No. 17 (TDR-94/94D-34-17), dated February 8, 1999. Collins Product Information Letter No. 71, dated January 1999, references the service bulletin.

(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 each airplane identified in paragraph (a) of this AD, regardless of whether it has been modified, altered, or repaired in the area subject to the requirements of this AD. For airplanes 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: [phone]; facsimile: [phone]; e-mail: [e-mail].

(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) How do I get copies of the documents referenced in this AD? You may obtain copies of the documents referenced in this AD from Rockwell Collins Inc., Business and Regional Systems, 400 Collins Road Northeast, Cedar Rapids, Iowa 52498. You may view this information at FAA, Central Region, Office of the Regional Counsel, 901 Locust, Room 506, Kansas City, Missouri 64106.

Issued in Kansas City, Missouri, on October 30, 2001.

Brian A. Hancock,

Acting Manager, Small Airplane Directorate, Aircraft Certification Service.