TRAFFIC COLLISION AND AVOIDANCE SYSTEM II (TCAS II)
TCAS 2000 (Optional)
The TCAS II system visually presents traffic advisories on the multi-function display to the flight crew.
The system interrogates every transponder equipped airplane within the selected range for bearing
and data. It uses this data to establish a track for collision avoidance predictions.
The TCAS computer performs functions that determine range, bearing, and of intruder aircraft based
on information computed from or contained in the reply messages. Bearing can only be determined
for intruder replies received on the system directional antenna. can only be determined if the intruder
is reporting in its transponder reply message.
Based on the information that can be extracted from or computed from the reply, the TCAS computer
evaluates the threat potential of the intruder by calculating intruder closing rate and position relative
to own aircraft. Based on this evaluation the TCAS computer categorizes the intruder as a non-
threat, proximity or traffic advisory.
For traffic advisory category aircraft, the TCAS computer outputs traffic advisory symbol position and
alert data to the EFIS. The TCAS computer also outputs traffic advisory alert voice messages to the
cockpit audio system.
For proximity and non-threat aircraft, the TCAS computer outputs proximity or non-threat traffic
symbol position data to the EFIS. Voice alerts are not generated for proximity or non-threat category
aircraft. Intruders which are not reporting are also detected and tracked. By using the interrogation
reply, the TCAS can accomplish the following:
1. Compute range between own airplane and an intruder.
2. Compute relative bearing to the intruder.
3. Compute and vertical speed of an intruder (if reporting).
4. Compute closing rate between an intruder and own airplane.
5. Issue a traffic advisory (TA) when the closing traffic is in the vicinity.
6. Issue a resolution advisory (RA) in order to maintain safe vertical separation.
7. Track 45 aircraft at once, displaying up to 30, and can coordinate a resolution advisory for
up to three intruders at once.
Certain functions of the traffic and collision avoidance system (TCAS) are tuned through the radio
management unit (RMU). Other selections are made with controls on the multi-function display
(MFD). For information on the MFD, refer to Flight Guidance System. The ATC/TCAS control page
display provides displays and controls for the TCAS modes. To access the page, the page (PGE)
button is pressed, and the ATC/TCAS line key is then pressed.
On the ATC/TCAS control page the additional selections which follow may be made. System
selection (INTRUDER) is possible between two modes; relative altitude or absolute altitude modes.
In relative (REL) (green) mode, the difference between the intruder airplane's altitude and own
airplane altitude is displayed. In absolute altitude mode (FL), the flight level (cyan) of the intruder
airplane is displayed. If FL is selected on the Honeywell system, the selection will return to REL in 20
seconds.
A TCAS selection may be made to display only traffic that constitutes a potential threat or all traffic.
The TA DISPLAY line key is used to select AUTO, whereupon traffic will be displayed on the multi-
function display (MFD) only if it is a TA (traffic advisory) or RA (resolution advisory) target. MANUAL
on the same key selects an MFD display in which all TCAS traffic within the viewing airspace will be
shown.
Cessna Citation XLS - Instrumentation & Avionics
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