Operation

The NAV control panels have an active frequency display window and a standby frequency display window. The frequency that shows in the active frequency display window is the frequency that the navigation radios use for operation. The standby frequency display window shows the next frequency you will use.

The transfer switch is a momentary action switch. It transfers the frequency in the standby frequency display window to the active frequency display window. When you push the switch, the frequency that is in the active frequency display window transfers to the standby frequency display window.

The frequency select control is a continuous rotary knob. There is an inner knob and an outer knob. The outer knob sets the tens and ones. The inner knob sets the tenth and one hundreth numbers.

At power up, the frequency displays show the last frequency entry before power down.

The NAV control panel continuous BITE function monitors the operation. The NAV control panel shows FAIL in the active and the standby frequency display windows when there is a failure. The monitor in the NAV control panel monitors the 28v dc input. If the monitor does not get the 28v dc, the frequency display windows are blank.

Test

When you push the test switch, the NAV control panel sends a test command out on it’s output bus. If a VOR frequency shows in the active frequency window, the test command goes to the VOR receiver. IF an ILS frequency shows in the active frequency window, the control panel sends a test command to the ILS receivers. If there is a DME frequency that is paired with the VOR or ILS frequency, a test command also goes to the DME interrogators.

When you do a test of the master dim and test system, the NAV control panel shows 188.88. The display shows for two seconds on then one second off until the test is complete.