TRAFFIC ALERT AND COLLISION AVOIDANCE SYSTEM (TCAS)
DESCRIPTION
The TCAS II system is an airborne traffic alert and collision avoidance system that interrogates transponders in nearby air-
craft and uses computer processing to identify and display potential and predicted collision threats. The system protects a
volume of airspace around the TCAS equipped aircraft. The system provides appropriate aural and visual advisories to the
flight crew to provide adequate separation when the computer analysis of intruding aircraft transponder replies predicts a
penetration of the protected airspace. The TCAS II system provides two types of advisories. A traffic advisory (TA) indi-
cates the relative position of an intruding aircraft that is approximately 35 seconds from the closest point of approach and
may, a short time later require a resolution advisory (RA). The TA provides the flight crew with the opportunity to visually
acquire the intruding aircraft. An RA will produce a threat resolution in the form of a vertical maneuver that will increase
separation when the computer predicts the intruder aircraft is within approximately 25 seconds from the closest point
of approach.
The TCAS II system can only generate resolution advisories for intruders equipped with operative Mode C or better tran-
sponders, which provide information on the altitude of the intruder. Traffic advisories, which display the relative position
of the intruder, can be generated for aircraft with operative transponders. The TCAS II equipment is viewed as a supplement
to the pilot, who, with the aid of the ATC system has the primary responsibility for avoiding mid-air collisions. The TCAS
II system provides no indication of traffic conflicts with the other aircraft without operative transponders.
COMPONENTS AND OPERATION
The TCAS II system provides the following capabilities:
- Collision avoidance tracking
- Threat detection
- Threat resolution
- Communication and coordination
- Surveillance
TA and RA symbols have priority over any conflicting display space usage and will overwrite any other symbols or char-
acters. The TCAS II has a maximum range of 40 nm and a maximum of 32 intruders can be displayed. Four different TCAS
symbols are used on the TCAS page to represent TCAS targets. Indicators that represent the intruder’s vertical speed and
relative altitude data accompany each TCAS symbol.
Relative altitude mode is used when the altitude between own aircraft and intruder aircraft is desired. Absolute altitude
mode is used when the barometric altitude of the intruder aircraft is desired. The relative (REL) or absolute (ABS) altitude
of intruder aircraft is shown below the traffic symbols on the TCAS display. Relative altitude mode is the default mode.
Altitude is not shown for intruder aircraft not reporting altitude data. To select REL or ABS, turn the MENU switch
to position the selection box around the desired mode.
Arrows are used to indicate the vertical speed of the target aircraft. The arrow indicates that an aircraft is changing altitude
at a rate of 500 fpm or greater.
Plus or minus signs along with a number symbolizes the relative altitude of the threat airplane. Plus indicates above and
minus indicates below.
TCAS MODE SELECT
Line select buttons on the left and right sides of the TCAS CONTROL page control the following functions:
- MODE (TA, TA/RA, or STBY)
- TRAFFIC (ON/OFF)
- ALT TAG (REL/ABS)
- TEST
- EXT TEST (ON/OFF)
- ALT LIMITS (ABOVE, NORM, BELOW)
Challenger Global 300 - Navigation
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