TCAS Home Page
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
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
this web is now mostly dormant.
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
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
(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
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