AIRPLANE
OPERATIONS
MANUAL
NAVIGATION AND
COMMUNICATION
MARCH 30, 2001
2-18-13
Page
1
Code
01
TUNING BACKUP CONTROL HEAD
The Tuning Backup Control Head is a unit that provides an alternative
means of tuning the NAV 2 and COM 2.
The TBCH is energized only when the AVIONICS MASTER is switched
ON, and in normal operation it displays the RMU 2 NAV and COM
active frequencies (NAV 2 and COM 2).
NORMAL MODE
In the Normal Mode, the TBCH displays the RMU 2 NAV and COM
active frequencies. Each time these frequencies are tuned via RMU,
the TBCH display is updated automatically. The same occurs when
these frequencies are tuned via TBCH, the RMU 2 NAV and COM
active frequencies being also updated automatically.
It is also possible to tune the RMU 1 NAV and COM active frequencies
using the RMU cross-side operational mode (see 2-18-11, page 4).
EMERGENCY MODE
When the TBCH is set to the Emergency Mode, the Radio
Management System will accept only the NAV and COM tuning via
TBCH, ignoring the RMUs control.
The RMUs will recover their capability of tuning the radio frequencies
only when the TBCH is set to the Normal Mode again.
SELF TEST
After power up, the Tuning Backup Control Head performs a self-test.
This test consists of saving the frequencies that the COM and NAV
units are tuned to as indicated by the Radio System Bus (RSB), and
then changing the frequency outputs to the COM and NAV and
verifying that they have changed on the RSB. Failures are announced
in the display line associated with the function as an error message
followed by an error code “ERXX”, with the “XX” showing a two-digit
error code.
This test is performed only on the ground, when the unit is turned on.
To Next Page
