Boeing 777: Air Traffic Control Transponder (ATC) & Traffic Collision Avoidance System (TCAS)

777 Air Traffic Control Transponder (ATC) & Traffic Collision Avoidance System (TCAS) by jerome meriweather
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777 Photo and/or Graphic Element
Two ATC transponders are controlled by a single control panel. The selected transponder activates when the airplane is airborne. The Traffic Collision Avoidance System (TCAS) consists of two Mode S transponders, a TCAS Transponder control panel, a computer processor, a TCAS EFIS control panel, two NDs capable of traffic display, two PFDs capable of pitch guidance to avoid transponder-equipped airplanes, an aural message system, and two directional antennas.

ABV / N / BLW Selectors

ABV - Displays altitude reporting traffic from 2700 feet below to 9900 feet above airplane altitude.
N (Normal) - Displays altitude reporting traffic from 2700 feet below to 2700 feet above airplane altitude.
BLW - Displays altitude reporting traffic from 9900 feet below to 2700 feet above airplane altitude.

ABS / REL Selectors

ABS - Target altitude information is displayed as three-digit absolute (indicated) altitude above sea level.
REL - Target altitude information is relative to present altitude )+/- two digits) or 00 for co-altitude.>

IDENT, TCAS and XPNDR Selecto

IDENT - Push to transmit an identification signal.>
TCAS / XPNDR Selector - Rotate to:
- STBY - TCAS and the transponders are in the standby mode.
- ALT RPTG OFF - Transponder operates without altitude reporting and TCAS is in the standby mode.
- XPNDR - Transponder operates with altitude reporting and TCAS is in the standby mode.
- TA ONLY - The transponder is on. TCAS is on but only the Traffic Advisory function of TCAS is operational. Resolution Advisories and pitch guidance are inhibited. The message TA ONLY appears on the ND display.
- TA / RA - The transponder is on and all Traffic Advisory and Resolution Advisory function of TCAS is operational. If a TA becomes active, the indications are the same as for TA only.