[Federal Register Volume 66, Number 214 (Monday, November 5, 2001)]
[Proposed Rules]
[Pages 55898-55900]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 01-27665]


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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. 2000-CE-32-AD]
RIN 2120-AA64


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

AGENCY: Federal Aviation Administration, DOT.

ACTION: Notice of proposed rulemaking (NPRM).

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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: (316) 946-4134; facsimile: (316) 946-4407; e-
mail: [email protected].

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

[[Page 55899]]

--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.


Sec. 39.13  [Amended]

    2. FAA amends Sec. 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
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(1) Determine whether the     Within the next 3     As specified in
 altitude information from     months after the      Rockwell Collins
 any TDR-94 Mode S             effective date of     Service Bulletin
 transponder (CPN 622-9352-    this AD.              No. 17 (TDR-94/94D-
 004) or TDR-94D Mode S                              34-17), dated
 transponder (CPN 622-9210-                          February 8, 1999.
 004) is derived from a                              Collins Product
 digital air data source or                          Information Letter
 a Gillham (gray code)                               No. 71, dated
 encoded source.                                     January 1999,
                                                     references the
                                                     service bulletin.

[[Page 55900]]

 
(2) If the altitude            At the next          In accordance with
 information is derived from   transponder check     Rockwell Collins
 a Gillham (gray code)         required by 14 CFR    Service Bulletin
 encoded source, have the      91.413 that occurs    No. 17 (TDR-94/94D-
 unit modified to prevent      3 months after the    34-17), dated
 erroneous altitude            effective date of     February 8, 1999.
 reporting. The modification   this AD or within     Collins Product
 encompasses converting the    the next 9 months     Information Letter
 TDR-94 transponder from       after the effective   No. 71, dated
 Collins part number (CPN)     date of this AD,      January 1999,
 622-9352-004 to CPN 622-      whichever occurs      references the
 9352-005; and converting      first.                service bulletin.
 the TDR 94D transponder
 from CPN 622-9210-004 to
 CPN 622-9210-005.
 (3) If the altitude          Not applicable......  Not applicable.
 information from all
 affected transponders is
 derived from a digital air
 data source, no
 modification action is
 required by this AD.
(4) Do not install any TDR-   As of the effective   Accomplish the
 94 Mode S transponder (CPN    date of this AD.      modification in
 622-9352-004) or TDR-94D                            accordance with
 Mode S transponder (CPN 622-                        Rockwell Collins
 9210-004) on any airplane                           Service Bulletin
 if the altitude information                         No. 17 (TDR-94/94D-
 is derived from a Gillham                           34-17), dated
 (gray code) encoded source,                         February 8, 1999.
 unless the modification                             Collins Product
 required by paragraph                               Information Letter
 (d)(2) of this AD is                                No. 71, dated
 incorporated.                                       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: (316) 946-4134; 
facsimile: (316) 946-4407; e-mail: [email protected].
    (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.
[FR Doc. 01-27665 Filed 11-2-01; 8:45 am]
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