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TCAS Home Page
Welcome to the TCAS Logic
System's home page on the FAA
Technical
Center
web.
This sub-web was created for the primary purpose of making draft material
for
DO-185A available to all members of RTCA SC-147 during the
development
of the change 7 specifications used in today's TCAS II / ACAS systems.
However, with the publication of DO-185A
through RTCA, Inc.,
this web is now mostly dormant.
About
TCAS:
The Traffic Alert and
Collision Avoidance System (TCAS) is an airborne system developed by the
FAA that operates independently from the ground-based Air Traffic Control
(ATC) system. TCAS was designed to increase cockpit awareness of
proximate aircraft and to serve as a "last line of defense" for
the prevention of mid-air collisions.
There are two levels of
TCAS systems:
TCAS I
was developed to accommodate the general aviation (GA) community and the
regional airlines. This system issues ‘Traffic
Advisories’ (TAs) to assist pilots in visual acquisition of
intruder aircraft. TCAS I is mandated on aircraft with 10 to 30
seats, although TCAS II may be installed instead.
TCAS II
is a more sophisticated system which provides the information of TCAS I, and
also analyzes the projected flight path of approaching aircraft and
issues ‘Resolution Advisories’ (RAs) to the pilot to resolve
potential mid-air collisions. TCAS II is required internationally in
aircraft with more than 30 seats or weighing more than 15,000 kg.
The TCAS II Minimum
Operational Performance Standards (MOPS) were updated and approved by
RTCA, Inc. Special Committee 147 and published in document DO-185A in
December, 1997 and available through RTCA, Inc. This latest revision to
the system is referred to as "Version 7" in the United
States. The
international community adopted these standards for the Airborne
Collision Avoidance System (ACAS) and it is now mandated throughout most
of Europe
and other countries such as Japan
and Australia.
FAA Technical Center TCAS
activities:
The FAA
Technical
Center
began working on collision avoidance systems well before the current
"TCAS" concept was envisioned. The FAA
Technical
Center
has been involved in many aspects of the development and implementation
of TCAS for use in national and international airspace. The FAA
Technical
Center
has conducted extensive flight testing and data evaluation of the
surveillance hardware and software, as well as the collision avoidance
(CAS) logic. This information has been used in both the initial
definition of system specifications through RTCA Incorporated, and the
continued revisions to these specifications. The FAA
Technical
Center
has also conducted and analyzed millions of computer simulated
encounters. This information has been used to verify that the logic
operates as designed, and has also been used to characterize those types
of encounters which would benefit from logic improvements.
The ADS-B / TCAS group
supported the implementation of TCAS into the airspace by conducting
demonstration flight tests to introduce limited numbers of pilots and
air-traffic controllers throughout the United
States to the system.
The FAA
Technical
Center
installed updated TCAS hardware and software aboard our test aircraft to
verify proper end-to-end operation of manufacturers systems, and to
support manufacturers in the testing and certification process.
TCAS is now a mature
system, and while those who worked on standards development have focused
their efforts towards ADS-B, TCAS group personnel still perform data
analysis on revenue-flight data recorded to monitor the performance of
TCAS in the national airspace, and simulated TCAS events when radar data
is provided. The Airborne Technology Team personnel participates in
the ACAS subgroup of the ICAO Aeronautical Surveillance Panel
(ASP). Through this forum, the analysis of TCAS performance
conducted here at the FAA
Technical
Center
is briefed to the international community. TCAS personnel
also continue to provide certification support for new TCAS systems.
For more information on
TCAS activities or the content of this page, please contact J. Stuart
Searight at Stuart.Searight@faa.gov.
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