[Federal Register Volume 64, Number 218 (Friday, November 12, 1999)]
[Rules and Regulations]
[Pages 61493-61495]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 99-29472]


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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. 99-NM-328-AD; Amendment 39-11418; AD 99-23-22]
RIN 2120-AA64


Airworthiness Directives; Various Transport Category Airplanes 
Equipped With Mode ``C'' Transponder(s) With Single Gillham Code 
Altitude Input

AGENCY: Federal Aviation Administration, DOT.

ACTION: Final rule; request for comments.

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SUMMARY: This amendment adopts a new airworthiness directive (AD) that 
is applicable to various transport category airplanes equipped With 
certain Mode ``C'' transponder(s) with single Gillham code altitude 
input. This action requires repetitive tests to detect discrepancies of 
the Mode ``C'' transponder(s), air data computer, and certain wiring 
connections; and corrective actions, if necessary. This amendment is 
prompted by reports that, during level flight, the Traffic Alert 
Collision Avoidance System (TCAS II) issued false advisories that 
directed the flightcrew to change course and either climb or descend. 
The actions specified in this AD are intended to prevent such false 
advisories due to inaccurate airplane altitude reporting, which could 
result in the flightcrew deviating the airplane from its assigned 
flight path and a possible mid-air collision.

DATES: Effective November 29, 1999.
    Comments for inclusion in the Rules Docket must be received on or 
before January 11, 2000.

ADDRESSES: Submit comments in triplicate to the Federal Aviation 
Administration (FAA), Transport Airplane Directorate, ANM-114, 
Attention: Rules Docket No. 99-NM-328-AD, 1601 Lind Avenue, SW., 
Renton, Washington 98055-4056.
    Information pertaining to this amendment may be obtained from or 
examined at the FAA, Transport Airplane Directorate, 1601 Lind Ave, 
SW., Renton, Washington 98055-4056.

FOR FURTHER INFORMATION CONTACT: Peter Skaves, Aerospace Engineer, 
Airplane and Flight Crew Interface Branch, ANM-111, FAA, Transport 
Airplane Directorate, 1601 Lind Avenue, SW., Renton, Washington 98055-
4056; telephone (425) 227-2795; fax (425) 227-1320.


[[Page 61494]]


SUPPLEMENTARY INFORMATION: The FAA has received reports of eleven 
incidents involving certain transport category airplanes equipped with 
Mode ``C'' transponder(s) with single Gillham code altitude input. 
These reports indicate that, during level flight, the TCAS II issued 
false advisories that directed the flightcrew to change course and 
either climb or descend. These instances all involved communication 
between airplanes with the TCAS II and airplanes having the Mode ``C'' 
transponder(s). The airplanes having the Mode ``C'' transponders are 
predominantly older, out-of-production transport category airplanes. In 
at least one instance, the Gillham wiring connection was determined to 
have failed, resulting in inaccurate altitude reporting by the Mode 
``C'' transponder. There are three primary sources of failure that 
could lead to inaccurate airplane altitude reporting: the Mode ``C'' 
transponder(s), air data computer, and Gillham wiring connections. The 
exact cause of the failures is unknown at this time. Such inaccurate 
altitude reporting and consequent false TCAS II advisories, if not 
prevented, could result in the flightcrew deviating the airplane from 
its assigned flight path and a possible mid-air collision.

Additional Considerations

    The FAA also has received information regarding inaccurate altitude 
reporting on airplanes equipped with TCAS II and Mode ``S'' 
transponders. Following one incident involving reduction of separation 
between two airplanes equipped with TCAS II and Mode ``S'' 
transponders, the Civil Aviation Authority (CAA), which is the 
airworthiness authority for the United Kingdom, issued British 
airworthiness directive 001-08-99. The British airworthiness directive 
applies to airplanes equipped with any Mode ``S'' transponder connected 
to a TCAS II system with Gillham altitude format, and requires 
repetitive tests of certain Mode ``S'' transponder systems to detect 
discrepancies, and corrective action, if necessary.

FAA's Determinations

    Based on the numerous incidents involving airplanes equipped with 
TCAS II and Mode ``C'' transponders, the FAA considers that immediate 
action is required to address the unsafe condition identified 
previously. Since the exact cause of the failures leading to inaccurate 
altitude reporting is unknown, the FAA finds it necessary to obtain and 
evaluate additional information, and to require corrective actions in 
the interim until final action can be identified. In addition, the CAA 
has kept the FAA informed of its actions regarding the Mode ``S'' 
transponders. The FAA is in the process of reviewing the information 
from the CAA, and is considering separate rulemaking action to address 
those airplanes having Mode ``S'' transponders.

Explanation of Requirements of the Rule

    Since an unsafe condition has been identified that is likely to 
exist or develop on other products of the same type design, this AD is 
being issued to prevent inaccurate airplane altitude reporting and 
false TCAS II advisories, which could result in the flightcrew 
deviating the airplane from its assigned flight path and a possible 
mid-air collision. This AD requires repetitive tests to detect 
discrepancies of the Mode ``C'' transponder(s), air data computer, and 
certain wiring connections; and corrective actions, if necessary. The 
actions are required to be accomplished in accordance with the 
procedures specified in the applicable component maintenance manuals 
and wiring diagrams contained in the airplane maintenance manuals.
    This AD also requires that operators report all inspection results 
(positive or negative) to the FAA.

Interim Action

    This is considered to be interim action until final action is 
identified, at which time the FAA may consider further rulemaking.

Determination of Rule's Effective Date

    Since a situation exists that requires the immediate adoption of 
this regulation, it is found that notice and opportunity for prior 
public comment hereon are impracticable, and that good cause exists for 
making this amendment effective in less than 30 days.

Comments Invited

    Although this action is in the form of a final rule that involves 
requirements affecting flight safety and, thus, was not preceded by 
notice and an opportunity for public comment, comments are invited on 
this rule. Interested persons are invited to comment on this rule by 
submitting such written data, views, or arguments as they may desire. 
Communications shall identify the Rules Docket number and be submitted 
in triplicate to the address specified under the caption ADDRESSES. All 
communications received on or before the closing date for comments will 
be considered, and this rule may be amended in light of the comments 
received. Factual information that supports the commenter's ideas and 
suggestions is extremely helpful in evaluating the effectiveness of the 
AD action and determining whether additional rulemaking action would be 
needed.
    Comments are specifically invited on the overall regulatory, 
economic, environmental, and energy aspects of the rule that might 
suggest a need to modify the rule. All comments submitted will be 
available, both before and after the closing date for comments, in the 
Rules Docket for examination by interested persons. A report that 
summarizes each FAA-public contact concerned with the substance of this 
AD will be filed in the Rules Docket.
    Commenters wishing the FAA to acknowledge receipt of their comments 
submitted in response to this rule must submit a self-addressed, 
stamped postcard on which the following statement is made: ``Comments 
to Docket Number 99-NM-328-AD.'' The postcard will be date stamped and 
returned to the commenter.

Regulatory Impact

    The regulations adopted herein will not have substantial direct 
effects 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, in 
accordance with Executive Order 12612, it is determined that this final 
rule does not have sufficient federalism implications to warrant the 
preparation of a Federalism Assessment.
    The FAA has determined that this regulation is an emergency 
regulation that must be issued immediately to correct an unsafe 
condition in aircraft, and that it 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. 
A copy of it, if filed, may be obtained from 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.

Adoption of the Amendment

    Accordingly, pursuant to the authority delegated to me by the

[[Page 61495]]

Administrator, the Federal Aviation Administration amends part 39 of 
the Federal Aviation Regulations (14 CFR part 39) 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. Section 39.13 is amended by adding the following new 
airworthiness directive:

99-23-22  Transport Category Airplanes: Amendment 39-11418. Docket 
99-NM-328-AD.

    Applicability: Transport category airplanes, certificated in any 
category, equipped with any Mode ``C'' transponder with single 
Gillham code altitude input, including, but not limited to, the 
transponder part numbers listed below. A Mode ``C'' transponder with 
single Gillham code altitude input is defined as any Mode ``C'' 
transponder meeting Aeronautical Radio, Inc. (ARINC) 572 
specification.
    Mode ``C'' Transponder Part Numbers:

Rockwell Collins: 622-2224-001, 622-2224-003, 522-2703-001, 522-
2703-011, 787-6211-001, 787-6211-002
Bendix: 066-1056-00, 066-1056-01, 066-1123-00, 2041599-6508
Wilcox: 97637-201, 97637-301
IFF: APX-100, APX-101

    Note 1: This AD applies to each airplane identified in the 
preceding applicability provision, 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 (d) 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 the unsafe condition has not been 
eliminated, the request should include specific proposed actions to 
address it.

    Compliance: Required as indicated, unless accomplished 
previously.
    To prevent false Traffic Alert Collision Avoidance System (TCAS 
II) advisories due to inaccurate airplane altitude reporting, which 
could result in the flightcrew deviating the airplane from its 
assigned flight path and a possible mid-air collision, accomplish 
the following:

Repetitive Tests

    (a) Within 45 days after the effective date of this AD: Perform 
the test procedures specified in paragraphs (a)(1) through (a)(9) of 
this AD to detect any discrepancies of the Mode ``C'' 
transponder(s), air data computer (ADC), or Gillham wiring 
connections, in accordance with the applicable ADC and Mode ``C'' 
transponder component maintenance manuals and airplane maintenance 
manual. Repeat the test procedures thereafter at intervals not to 
exceed 45 days.
    (1) Connect an air data test set to the Captain's (No. 1) Pitot/
Static system.
    (2) In the airplane flight deck, select Mode ``C'' transponder 
(1), or left Mode ``C'' transponder, depending on airplane flight 
deck configuration, and select ADC source (1).
    (3) Select the air data test set to the following altitude 
reporting values: 1,000 feet; 4,100 feet; 15,700 feet; and 31,000 
feet.
    (4) For each selected altitude, verify that the Mode ``C'' 
altitude reporting is within tolerance (+/-125 feet), and record the 
altitude output as follows: 1,000 feet (+/-125 feet); 4,100 feet (+/
-125 feet); 15,700 (+/-125 feet); and 31,000 feet (+/-125 feet).
    (5) In the airplane flight deck, select ADC source (2) and 
repeat paragraphs (a)(3) and (a)(4) of this AD.
    (6) In the airplane flight deck, select Mode ``C'' transponder 
(2), or the right Mode ``C'' transponder, depending on airplane 
flight deck configuration, select ADC source (1), and repeat 
paragraphs (a)(3) and (a)(4) of this AD.
    (7) In the airplane flight deck, select ADC source (2) and 
repeat paragraphs (a)(3) and (a)(4) of this AD.
    (8) Connect an air data test set to the Captain's (No. 2) Pitot/
Static system.
    (9) Repeat paragraphs (a)(2) through (a)(7) of this AD.

    Note 2: The tests required by paragraph (a) of this AD examine 
the three primary sources of inaccurate airplane altitude reporting. 
These three sources are: ADC's, Mode ``C'' transponders, and the 
Gillham wiring connections between the ADC and Mode ``C'' 
transponder.

Corrective Actions

    (b) If any discrepancy is detected during any test required by 
paragraph (a) of this AD: Prior to further flight, repair in 
accordance with the applicable ADC and Mode ``C'' transponder 
component maintenance manual and airplane maintenance manual. If the 
repair information is not available in the applicable manual, prior 
to further flight, repair in accordance with a method approved by 
the Manager, Seattle Aircraft Certification Office (ACO), FAA, 
Transport Airplane Directorate.

Reporting Requirement

    (c) Within 10 days after accomplishing the initial and 
repetitive tests required by paragraph (a) of this AD, submit a 
report of the inspection and test results (both positive and 
negative findings) to: Peter Skaves, Aerospace Engineer, Airplane 
and Flight Crew Interface Branch, ANM-111, FAA, Transport Airplane 
Directorate, 1601 Lind Avenue, SW., Renton, Washington 98055-4056; 
fax (425) 227-1320. The test results must include the Mode ``C'' 
transponder(s) and ADC part number(s), and must specify if any 
discrepancies of the Gillham wiring connections were detected, and 
if corrective action was required. Information collection 
requirements contained in this regulation have been approved by the 
Office of Management and Budget (OMB) under the provisions of the 
Paperwork Reduction Act of 1980 (44 U.S.C. 3501 et seq.) and have 
been assigned OMB Control Number 2120-0056.

Alternative Methods of Compliance

    (d) An alternative method of compliance or adjustment of the 
compliance time that provides an acceptable level of safety may be 
used if approved by the Manager, Seattle ACO. Operators shall submit 
their requests through an appropriate FAA Principal Maintenance or 
Avionics Inspector, who may add comments and then send it to the 
Manager, Seattle ACO.

    Note 3: Information concerning the existence of approved 
alternative methods of compliance with this AD, if any, may be 
obtained from the Seattle ACO.

Special Flight Permits

    (e) Special flight permits may be issued in accordance with 
sections 21.197 and 21.199 of the Federal Aviation Regulations (14 
CFR 21.197 and 21.199) to operate the airplane to a location where 
the requirements of this AD can be accomplished.
    (f) This amendment becomes effective on November 29, 1999.

    Issued in Renton, Washington, on November 4, 1999.
John J. Hickey,
Manager, Transport Airplane Directorate, Aircraft Certification 
Service.
[FR Doc. 99-29472 Filed 11-10-99; 8:45 am]
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