In the STANDBY (green) mode the TCAS computer shows no traffic displays and does not reply to
other airplane interrogations. The standby mode is selected by pressing the STANDBY line key on
the main tuning page, thereby causing the transponder not to transmit and disabling the TCAS
system.
The primary TCAS selection is displayed in the lower left window of the RMU main tuning page.
Control of those displayed functions is possible by means of the line keys and/or the tuning knobs,
once the tuning box is moved to the desired function with the line key. Range and altitude bands are
selectable. The following are included:
1. Altitude band select - With the NORMAL band selected (green) the altitude display
encompasses a range of ±2700 feet; with ABOVE (cyan) selected the altitude display
changes to a range of -2700 feet to +7000 feet from own airplane altitude. If BELOW (cyan)
is selected, the range becomes from, -7000 feet to +2700 feet from own airplane altitude.
2. Range (green) - Selectable at ranges of 6, 12, 20, and 40 NM. Selection is made by
pressing the RANGE line key or by turning the tuning knobs once the tuning box is
transferred to the RANGE function by pressing the line key.
3. TCAS Display 1/2 - This is the annunciation of which (pilot or copilot) TCAS display features
the RMU is controlling. When the cursor is in the window, the 1/2 button is used for the
selection. At power down the selections store.
Flight ID is a mode S coding which reflects the current flight's call sign. The outer tuning knob moves
the character position designator and the inner tuning knob selects the desired alphanumeric
character.
The flight level 1/2 selection on the ATC/TCAS control page displays the transponder's encoded and
the air data source (digital air data computer 1 or 2) for that (i.e., DADC 1 and DADC 2).
The TCAS system has a self-test which may be activated when the yellow cursor is in the ATC/TCAS
window and the TST key is pressed on the RMU control. “TEST” will be displayed when the test is
active. During the test the TCAS traffic displays will show test pattern traffic symbols, red and green
resolution advisories, during the test sequence. The sequence takes approximately ten seconds. If
the test is completed successfully the system will return to the set operating modes and aurally
annunciate "TCAS SYSTEM TEST OK" on the cockpit audio system. For a failure in the TCAS
system “TCAS FAIL” will be displayed in yellow on the TCAS display and the audio system aurally
annunciates "TCAS SYSTEM FAIL. TEST" and will operate either on the ground or airborne.
The TCAS system requires an operating mode S transponder with encoded altitude data included in
the interrogation replies. When the transponder is set to STBY, the receiver transmitter may
automatically change to standby mode or turn itself off.
Cessna Citation XLS - Instrumentation & Avionics
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