General
When you tune an ILS frequency on the NAV control panels, discrete signals go to the DEUs to tell if the frequency is an ILS or VOR frequency. Each NAV control panel sends the discrete signal to the DEU 1 and DEU 2.
The FCCs send an ILS tune inhibit to the ILS function of the MMRs during the approach (APP) mode of operation. The ILS receiver will not accept another tune frequency during this mode.
The PSEU sends air/ground discrete signals to the MMRs to set the flight leg count in the internal memory, and also inhibit test in the air.
The MMRs send ILS ground station audio to the REU. The REU sends the audio to the flight compartment.
ILS - RECEIVER
Purpose
The multi-mode receiver contains an ILS receiver and a global positioning system (GPS) sensor unit. The ILS receiver function supplies localizer and glideslope deviation to different airplane systems. The GPS sensor unit supplies position data and time to the flight management computer system (FMCS).
Description
The MMR is a standard ARINC 600 3 MCU unit with dimensions 3.75 x 7.75 x 14.6 inches. The receiver weighs 10 pounds and uses 115v ac 400 Hz power for operation.
Test and Indication
There are status LED indicators and a test switch on the front of the multi mode receiver. The test switch starts a functional test of the receiver. The LED status indicators show test results.
ILS - ANTENNAS
Localizer Antenna
The localizer antenna has two elements. One element supplies RF inputs to ILS receiver 1 and one element supplies RF inputs to ILS receiver 2. The localizer antenna receives frequencies from 108.1 Mhz to 111.95 Mhz at odd tenth intervals.
Glideslope Antenna
The glideslope antenna also has two elements. One element supplies RF signal inputs to MMR 1 and one element supplies RF signal inputs to MMR 2. The glideslope antenna receives frequencies from 328.6 Mhz to 335.4 Mhz.
ILS - NAVIGATION CONTROL PANEL
General
The navigation (NAV) control panels supply frequency control and test signals to the DME, the MMR, and the VOR navigation radios.
Operation
The NAV control panels have an active frequency indicator and a standby frequency indicator. The frequency that shows in the active frequency indicator is the frequency the navigation radios use for operation. The standby frequency indicator shows the next frequency you will use.
The frequency transfer switch is a momentary action switch. It transfers the frequency in the standby frequency indicator to the active frequency indicator. When you push the switch, the frequency in the active frequency indicator transfers to the standby frequency indicator.
The frequency selectors are continuous rotary selectors. There is an inner selector and an outer selector. The outer selector sets the tens and ones numbers. The inner selector sets the tenth and one hundredth numbers. The frequency selectors only change the numbers in the standby frequency indicator. 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 indicators when there is a control panel failure.
An internal monitor in the NAV control panel monitors the 28v dc input. If the monitor does not see the 28v dc, it shows the message BLANK in the active and the standby frequency indicators.
Test
When you push the NAV control panel test switch, a test command goes out on the data bus. If a VOR frequency is active, the VOR receiver starts a self test. If an ILS frequency is active, the MMR receiver starts a self test. If a DME frequency is paired with the VOR or ILS frequency, the DME interrogator starts a self test at the same time.
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.
