Tcas Ii Theory Of Operation - Garmin GTN 625 Pilot's Manual

9.9 TCAS II
NOTE: This feature is available with software v6.30 and later.
WARNING: Traffic information shown on system displays is provided as an
aid in visually acquiring traffic. Traffic avoidance maneuvers are based upon
TCAS II Resolution Advisories, ATC guidance, or positive visual acquisition
of conflicting traffic.
WARNING: Do not rely solely upon the display of traffic information to
accurately depict all of the traffic information within range of the aircraft.
Due to lack of equipment, poor signal reception, and/or inaccurate
information from other aircraft, traffic may be present but not represented
on the displays.
NOTE: If the installed TCAS II traffic system is not a GTS 8000, refer to
the applicable documentation for system-specific information.
A Traffic Alert and Collision Avoidance System II (TCAS II), such as the
GTS 8000, improves flight safety by monitoring nearby airspace for aircraft flying
with operating transponders. The TCAS II system provides traffic information to
the displays. If separation from other aircraft is within certain limits, the system
issues Traffic Advisories (TAs) assisting the flight crew in the visual acquisition
of traffic, or Resolution Advisories (RAs) providing recommended vertical
guidance maneuvers to resolve traffic conflicts.
9.9.1

TCAS II Theory of Operation

When the TCAS II system is operating in TA/RA or TA Only Mode, the system
interrogates the transponders of other aircraft in the vicinity, and monitors for
their replies. Based on successive replies, the system tracks the range, bearing,
and (if reported) the altitudes of other aircraft. For each detected aircraft
transponder, the system calculates time to, and separation at, the closest point
of approach (CPA) around the potential collision area surrounding own aircraft.
Based on CPA time, own aircraft altitude, and selected TCAS II system mode,
the system determines if a TA or RA should be issued for a detected intruder.
190-01004-03 Rev. P GTN 625/635/650 Pilot's Guide
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