[Federal Register Volume 64, Number 233 (Monday, December 6, 1999)]
[Notices]
[Pages 68194-68195]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 99-31523]
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DEPARTMENT OF TRANSPORTATION
Federal Aviation Administration
Terrain Awareness and Warning System
AGENCY: Federal Aviation Administration (FAA), DOT.
ACTION: Notice of publication of Technical Standard Order (TSO)-C151a,
Terrain Awareness and Warning System.
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SUMMARY: The FAA has issued TSO-C151a, Terrain Awareness and Warning
System, and canceled TSO-C151. The FAA has taken this action to clarify
and correct certain paragraphs and tables that appeared in TSO-C151.
The FAA has determined that the changes to TSO-C151a are of a
clarifying and corrective nature, and that these changes do not alter
the original intent of the airworthiness requirements of the paragraphs
or tables being changed. Therefore, the FAA has taken this
administrative action without using public comment process. However,
the FAA will accept any comments about TSO-C151a and will consider them
in any future revision to TSO-C151a. The changes are discussed below
under the section titled SUPPLEMENTARY INFORMATION.
FOR FURTHER INFORMATION CONTACT: Michelle Swearingen, Federal Aviation
Administration (FAA), Aircraft Certification Service, Aircraft
Engineering Division, Avionic Systems Branch, AIR-130, 800 Independence
Avenue, SW, Washington, DC 20591, Telephone: (202) 267-3817, FAX: (202)
267-5340.
SUPPLEMENTARY INFORMATION:
Table 3.1, Appendix 1: The FAA has modified table 3.1 of appendix 1
to make it clearer and easier to use. These modifications include new
notes to table 3.1 and appropriate modifications to the related test
conditions in appendix 3. The specific modifications are described in
the following discussion.
In table 3.1 the column titled TAWS(RTC) was changed to TAWS(RTC)
DESCENDING. A new column titled TAWS(RTC) LEVEL FLIGHT was added
between the column titled TERPS(ROC) and the column now titled
TAWS(RTC) DESCENDING. The new column contains the following parameters:
for enroute the parameter is 700 feet; for terminal, 350 feet; for
approach, 150 feet; and for departure, 100 feet.
Note 2 was modified and corrected by retaining the ability to use a
linear slope but by deleting the reference to a specific design
criteria that does not meet the requirement of table 3.1. The note now
reads as follows: As an alternate to the stepped down reduction from
the terminal to approach phase in Table 3.1, a linear reduction of the
RTC as the aircraft comes closer to the nearest runway is allowed,
providing the requirements of Table 3.1 are met.
Two clarifying notes were added, note 3 and note 4. Note 3 reads as
follows: During the visual segment of a normal instrument approach
(typically about 1 NM from the runway threshold), the RTC should be
defined/reduced to minimize nuisance alerts. Below a certain altitude
or distance from the runway threshold, logic may be incorporated to
inhibit the FLTA function. Typical operations below Minimum Descent
Altitude (MDA), Decision Height (DH), or the Visual Descent Point (VDP)
should not generate nuisance alerts. Note 4 reads as follows: The
specified RTC values are reduced slightly for descending flight
conditions to accommodate the dynamic conditions and pilot response
times.
The related test conditions in appendix 3 were modified to be
compatible with the modified table 3.1 of appendix 1. In paragraph 1.3,
appendix 3, 700 replaced both 500 parameters. In paragraph 1.5,
appendix 3, 350 replaced both 300 parameters. In paragraph 1.7,
appendix 3, both 100 parameters were replaced with 150. In table B,
appendix 3, for the 250 and 300 ground speed test runs, both 6000
parameters were replaced with 5800. In the same table B, all five 5500
parameters were replaced with 5700. In table D, appendix 3, all four
1300 parameters were replaced with 1350. In table F, appendix 3, all
four 500 parameters were replaced with 550.
Section 3.3, Appendix 1: The FAA has modified the first paragraph
of section 3.3 by clarifying when the GPWS functions may be adjusted or
modified and by deleting general language that paraphrases FAA
deviation policy. Deviations are addressed in paragraph 3.f of the
basic TSO, and the use of deviations is applicable to the entire TSO
document. The first paragraph of section 3.3 now reads as follows: In
addition to the TAWS Forward Looking Terrain Avoidance and PDA
functions, the equipment shall provide the GPWS functions listed below
in accordance with TSO-C92c. Some GPWS alerting thresholds may be
adjusted or modified to be more compatible with the FLTA alerting
functions and to minimize GPWS nuisance alerts. However, it is
essential to retain the independent protective features provided by
both the GPWS and FLTA functions. In each case, all the following
situations must be covered. The failure of the TSO C92c equipment
functions, except for power supply failure, input sensor failure, or
failure of other common portions of the equipment, shall not cause a
loss of the FLTA, PDA, or Terrain Display.
Section 10.0, Appendix 1: The FAA has modified section 10.0 to
clarify the use of alternate definitions for various phases of flight.
The FAA also has removed reference to TSO-C129 and RTCA/DO-229. These
documents are for GPS navigation operations and are not appropriate for
TAWS operations.
[[Page 68195]]
Section 10.0 now reads as follows: The TAWS equipment search volumes
and alerting thresholds should vary as necessary to be compatible with
TERPS and other operational consideration. For that reason, a set of
definitions is offered for Enroute, Terminal, Approach and Departure
Phases of Flight. Other definitions for enroute, terminal and approach
may be used by TAWS provided they are compatible with TERPS and
standard instrument approach procedures and will comply with the test
criteria specified in Appendix 3.
Tables A, C, and E; Appendix 3: The FAA has modified these tables
by correcting certain parameters. Note 4 to table A, note 2 to table C
and note 2 to table E state that the values are based upon 20 percent
of the airplane's vertical velocity. However, a few values were
calculated using a 20-second criteria instead of the 20 percent
criteria. The corrected values are as follows: In column F of table A,
the 2111 value was replaced with 1800. In column F of table C, the 1036
value was replaced with 900, and the 1456 value was replaced with 1100.
In column F of table E, the 639 value was replaced with 550.
How To Obtain Copies: A copy of TSO-C151a may be obtained via
Internet (http://www.faa.gov/avr/air/airhome.htm) or on request from
the individual listed under the section titled FOR FURTHER INFORMATION
CONTACT. REFERENCED DOCUMENTS: TSO-C151a references several RTCA, Inc.
documents that contain specific requirements related to the TSO. RTCA
Document No. DO-161A, ``Minimum Performance Standards--Airborne Ground
Proximity Warning Equipment,'' dated May 27, 1976; DO-160D,
``Environmental Conditions and Test Procedures for Airborne
Equipment,'' dated July 29, 1997; DO-178B, ``Software Considerations in
Airborne Systems and Equipment Certification,'' dated December 1, 1992;
and DO-200A, ``Preparation, Verification and Distribution of User-
Selectable Navigation Data Bases,'' dated November 28, 1988, may be
purchased from the RTCA Inc., 1140 Connecticut Avenue, NW., Suite 1020,
Washington, DC 20036.
Issued in Washington, DC, on November 29, 1999.
James C. Jones,
Manager, Aircraft Engineering Division, Aircraft Certification Service.
[FR Doc. 99-31523 Filed 12-3-99; 8:45 am]
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