VOR system - vor/mb receiver

General

The VOR/LOC antenna is on the top of the vertical stabilizer. The VOR antenna receives RF signals in the frequency range of 108 MHz to 117.95 MHz. The antenna receives VOR and localizer frequencies. The VOR/LOC antenna sends VOR signals to both VOR/MB receivers.

 

 

NAVIGATION CONTROL PANEL

General

The navigation (NAV) control panel supplies frequency inputs and test commands to the DME, ILS, and VOR navigation radios.

Operation

The NAV control panel has 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 want to use.

The transfer switch is a momentary action switch that 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 digits. The inner knob sets the tenths and one hundreths digits.

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

The NAV control panel continuous bite monitors control panel operation. The NAV control panel shows FAIL in the active and standby frequency display windows when there is a failure. An internal monitor in the NAV control panel monitors the 28v dc input. If the monitor does not see the 28v dc input, it will show the message BLANK in both the active and standby frequency display windows.

When you set a VOR frequency in the range of 108 Mhz to 117.95 Mhz, the NAV control panel sends the frequency to the VOR/MB receivers and DME interrogators. The control panel sets the data word to the ILS receivers to NCD.

Test

When you push the NAV control panel test switch, a test command goes out to the VOR/MB receiver, ILS receiver, and DME interrogator. If a VOR frequency shows in the active frequency window, the test command goes to only the VOR/MB receiver. IF an ILS frequency shows in the active frequency window, the control panel sends a test command to only the ILS receiver. 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.

 

 

 

VOR SYSTEM - FUNCTIONAL DESCRIPTION

General

The receiver contains VOR and marker beacon functions. This section only covers the VOR function.

Operation

Frequency tune inputs from the NAV control panel go to an ARINC 429 receiver in the VOR/MB receiver, then to the processor. The processor sends the tune inputs to the frequency synthesizer to tune the receiver circuits.

The control panel sends a discrete to the REU when you tune a VOR frequency. The REU uses the discrete to select VOR audio inputs.

When you tune a VOR frequency, the control panel also sends a discrete to the DEUs. The DEUs use the discrete to display VOR or ILS as the frequency data source on the lower left corner of the captain and first officer NAV displays.

The processor sends fault data to the memory card. Only shop personnel can read the memory card contents.

The air/ground discrete input from the PSEU inhibits a VOR test when the airplane is in the air. The receiver also uses the discrete for flight leg count.

RF input signals from the VOR/ILS antenna go through the power divider then to the receiver circuits in the VOR/MB receiver. The receiver circuits send audio and morse code station identifier signals from the ground station to the audio processor.

The audio processor sends the audio and morse code station identifier signal to the audio output circuits then to the remote electronics unit.

The morse decoder circuit decodes the station identifier and puts it in digital format then sends it to the ARINC 429 transmitter. The display electronic units (DEU 1 & 2), use the data to show the station identifier.

The VOR/MB VOR receiver circuits send the antenna inputs to the bearing processor which calculates the VOR station bearing. Data from the bearing processor goes to the ARINC 429 transmitter. The VOR/MB receiver transmits VOR bearing and receiver status on two output buses.

Output bus 1 goes to the onside FCC. Output bus 2 goes to these components:

· Flight data acquisition unit (FDAU)

· Radio magnetic indicator (RMI)

· Flight management computers (FMC)

· Display electronic units (DEU).

 

Test

When you push the test switch on the NAV control panel, a test command goes to the receiver when a VOR frequency is the active frequency. When the processor receives a test command, it monitors the VOR/MB receiver operation and control input status. Test results show on the status LEDs when you do a test from the front panel switches.