User's Manual
SYSTEM DESCRIPTION AND INSTALLATION MANUAL
TCAS 3000 Traffic Alert and Collision Avoidance System
34−43−23
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Page 1−7
15 Dec 2005
3. System Description
The TCAS 3000 is an onboard advisory system designed to act as a backup to the air traffic
control (ATC) radar and the “see and avoid” procedures. By computing the closure rate and
altitude of all transponder equipped aircraft in the surrounding airspace, the TCAS can
anticipate a potential midair collision before it has a chance to materialize.
TCAS 3000 continually plots local air traffic on the associated display, and in the event of a
conflicting flightpath, guides the pilot towards the correct avoidance maneuver. If the intruding
aircraft is also equipped with a TCAS II compatible system, the two systems can communicate
their mutual intentions through the Mode S transponders. The coordinated advisories that
result allow the two pilots to execute complementary avoidance maneuvers.
TCAS 3000 complies with ARINC Characteristic 735A and TSO−C119−b.
A. System Functional Description
Vertical guidance to avoid midair collisions is accomplished by interrogating the Mode A,
Mode C, and Mode S transponders of potential threat aircraft, tracking their responses,
and providing advisories to the flight crew to assure vertical separation. Two levels of
advisories are provided:
• Traffic advisories (TA), indicate the range, bearing, and relative altitude of the intruder
to aid in visual acquisition of the intruder
• Resolution advisories (RA) indicate a vertical maneuver to be performed or avoided in
order to assure safe separation.
Traffic advisories can be displayed on ACSS Vertical Speed Indicator/Traffic and
Resolution Advisory (VSI/TRA) display, Electronic Flight Instrument System (EFIS) or any
instrument that displays the appropriate symbology and conforms to the definition of
ARINC Characteristic 735.
Resolution advisories can be displayed on the ACSS VSI/TRA display, EFIS or any other
indicator that displays the appropriate symbology and conforms to the definition of ARINC
Characteristic 735.
Figure 1−1 shows the various types of intruder equipment and the resulting advisories. It
should be noted that Mode A equipped intruders result in detection and display of TAs
only. An intruder not equipped with a transponder is invisible to TCAS.
Communication with another TCAS equipped aircraft is provided by an onboard diversity
Mode S transponder. Only one onboard Mode S transponder is required for TCAS
operation. However, the ACSS TCAS 3000 operates with either of two onboard Mode S
transponders, one of which operates as a spare. The transponder in use is selectable
from the cockpit. Figure 1−2 shows the communication between two TCAS equipped
aircraft.