Airworthiness Directives; Various Transport Category Airplanes Equipped with Mode “C” Transponder(s) with Single Gillham Code Altitude Input

[Federal Register Volume 65, Number 77 (Thursday, April 20, 2000)]
[Rules and Regulations]
[Pages 21133-21134]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 00-9247]



[[Page 21133]]

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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. 2000-NM-81-AD; Amendment 39-11686; AD 99-23-22 R2]
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; rescission.

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SUMMARY: This amendment rescinds Airworthiness Directive (AD) 99-23-22 
R1, which is applicable to various transport category airplanes 
equipped with Mode ``C'' transponder(s) with single Gillham code 
altitude input. That 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 
requirements of that AD were intended to prevent false advisories that 
direct the flightcrew to change course and either climb or descend, 
which could result in the flightcrew deviating the airplane from its 
assigned flight path, and a possible mid-air collision. Since the 
issuance of that AD, test data have been collected that demonstrate 
that the repetitive tests are unnecessary.

EFFECTIVE DATE: April 20, 2000.

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.

SUPPLEMENTARY INFORMATION: On November 4, 1999, the Federal Aviation 
Administration (FAA) issued AD 99-23-22, amendment 39-11418 (64 FR 
61493, November 12, 1999), as revised by AD 99-23-22 R1, amendment 39-
11473 (64 FR 70181, December 16, 1999), applicable to various transport 
category airplanes equipped with Mode ``C'' transponder(s) with single 
Gillham code altitude input. That 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. That action was 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. Such false advisories, if not corrected, could 
result in the flightcrew deviating the airplane from its assigned 
flight path and a possible mid-air collision.

Actions Since Issuance of Previous AD

    The compliance time for the initial test of the Mode ``C'' 
transponder(s) with single Gillham altitude code input, as required by 
AD 99-23-22 R1, has passed. Therefore, the FAA assumes that the test 
has been conducted at least once, and all applicable corrective actions 
have been accomplished, on all transport category airplanes affected by 
that AD. The following is a summary of the airplane inspections and 
test results:

Aircraft Test Results (AD 99-23-22 R1) 
    Aircraft test results reviewed = 1,142
    Aircraft passing tests without corrective action required = 1,055
    Aircraft failing tests with corrective action required = 87
    Percent of aircraft that failed the AD test = 7.6%
Aircraft Wiring/Avionics Failures 
    Mode ``C'' transponder failures = 49
    Air Data Computer (ADC) failures = 14
    Encoding altimeter failures = 3
    Gillham code wiring failures = 1
    Miscellaneous wiring failures = 8
    Failures sources under review = 12

    The results of the transponder tests required by AD 99-23-22 R1 
revealed that numerous Mode ``C'' transponders failed the test, and 
many of the Mode ``C'' test failures have been determined to be caused 
by a particular transponder type. All other test failures reported by 
operators appear to be random and isolated.
    The FAA concludes that continued repetitive tests on the applicable 
airplane models listed in AD 99-23-22 R1 are unnecessary since the 
corrective actions have been accomplished on all transport category 
airplanes identified in that AD.
    In addition, the FAA has determined that the repetitive performance 
of the tests required by AD 99-23-22 R1 may result in increased or 
accelerated component wear, which could contribute to reports of 
incorrect airplane altitude.

Future Rulemaking

    Over 50 percent of the airplane test failures have been reported by 
operators to be caused by Mode ``C'' transponders. The FAA is 
conducting further reviews to determine whether a systematic root cause 
failure of that Mode ``C'' transponder exists. Based on the results of 
these reviews, the FAA may consider further rulemaking to address 
potential problems concerning the Mode ``C'' transponder.

FAA's Determination

    Because the results of the tests required by AD 99-23-22 R1 have 
identified and corrected the causes of the identified unsafe condition, 
and because repetitive performance of the test may increase or 
accelerate component wear and contribute to reports of incorrect 
airplane altitude, the FAA has determined that it is necessary to 
rescind AD 99-23-22 R1 to prevent operators from performing unnecessary 
and potentially harmful repetitive tests.
    Since this action rescinds a requirement to perform unnecessary 
actions, it has no adverse economic impact and imposes no additional 
burden on any person. Therefore, notice and public procedures hereon 
are unnecessary, and the rescission may be made effective upon 
publication in the Federal Register.

The Rescission

    Accordingly, pursuant to 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:

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 an airworthiness directive 
removing amendment 39-11473.

99-23-22 R2  Transport Category Airplanes: Amendment 39-11686. 
Docket No. 2000-NM-81-AD. Rescinds AD 99-23-22 R1, Amendment 39-
11473.

    Applicability: Transport category airplanes, as listed below, 
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. Whether a 
Mode ``C'' transponder has a single Gillham code altitude input may 
be determined by reviewing the transponder installation 
instructions.

Airplane Models

Airbus Industrie
    A300
    A310
British Aerospace
    BAe Avro 146-RJ
    BAe ATP
Fokker
    F28 Mark 0070
    F28 Mark 0100

[[Page 21134]]

    F28 Mark 1000-4000
Lockheed
    L-1011 TriStar
    L-188 Electra
CASA
    CN-235
Dassault Aviation
    Mystere Falcon 50
    Mystere Falcon 900
    Mystere Falcon 200
    Fan Jet Falcon Series G
Boeing (MDC)
    DC-10-30
    DC-10-40
    DC-9
    DC-9-81
    DC-9-82
    DC-9-83
    DC-9-87
    Boeing 707
    Boeing 727
    Boeing 737
    Boeing 747
Bombardier
    CL-215-1A10
    CL-215-6B11
    CL-600-1A11
    CL-600-2A12
    CL-600-2B16
Gulfstream
    G1159 (G-II)
    G-1159A (G-III)
    G-IV

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

    This rescission is effective April 20, 2000.


    Issued in Renton, Washington, on April 7, 2000.
Donald L. Riggin,
Acting Manager, Transport Airplane Directorate, Aircraft Certification 
Service.
[FR Doc. 00-9247 Filed 4-19-00; 8:45 am]
BILLING CODE 4910-13-U

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