INSTRUMENT LANDING SYSTEM (ILS)
General
The instrument landing system (ILS) has two multi-mode
receivers (MMRs) that contain the ILS function. The ILS
function in the MMRs receive inputs from these antennas:
· VOR/LOC antenna
· Localizer antenna
· Glideslope antenna.
COMPONENT LOCATION
Electronic Equipment Compartment
The multi-mode receivers (MMRs) are in the electronic equipment compartment. MMR 1 is on the E1-2 shelf. MMR 2 is on the E1-4 shelf. The LOC antenna switches are on the side of the E1 rack.
Nose Radome
The glideslope and localizer antennas are in the nose radome.
The glideslope antenna is above the weather radar antenna.
The localizer antenna is below the weather radar antenna.
POWER INTERFACES
ILS - DIGITAL INTERFACE
General
These are the components that have a digital interface with the multi-mode receivers:
· Captain and first officer NAV control panels
· Flight data acquisition unit (FDAU)
· Standby attitude indicator
· Ground proximity warning computer (GPWC)
· Flight management computer (FMC) 1 and 2
· Display electronics units (DEU)
· FCC A and FCC B.
Digital Inputs
The NAV control panels supply frequency tune inputs to the multi-mode receivers. The NAV control panels also send tune inputs to the VOR and DME systems on a separate data bus.
ILS - FREQUENCY TRANSFER AND INSTRUMENT SWITCHING
General
The frequency transfer switch on the NAV control panel and the VHF NAV transfer switch on the navigation/displays source select panel have interface with the FCCs and DEUs.
Frequency Transfer Switch
The frequency transfer switch on the NAV control panel permits the crew to transfer the frequency from the standby display window on the NAV control panel, to the active display window. The transfer switch is a momentary action switch. When you push the switch, it changes the discrete level to the FCCs. The discrete tells the FCC when there is an ILS frequency change.
ILS - ANTENNA INTERFACE
ILS - ANALOG INTERFACES
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.
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.
Power Interface
The NAV control panel uses 115v ac power for operation. It also uses 28v dc for an internal monitor. The NAV control panel uses 5v ac from the master dim and test for panel lights.
ARINC 429 Interfaces
Frequency tune inputs and test commands from the NAV control panel go to the MMR on an ARINC 429 bus.
When you tune an ILS frequency, the frequency tune circuits operate switches in the NAV control panel that send these discrete signals:
· Open discrete to the REU
· Ground discrete to the DEUs
· 28v dc to the FCCs
· 28v dc to the LOC antenna switches.
RF Interfaces
RF signals from the VOR/LOC antenna or localizer antenna in the nose radome, go to the localizer receiver circuits in the MMR. RF signals from the glideslope antenna in the nose radome go to the glideslope receiver circuits in the MMR.
ILS - FUNCTIONAL DESCRIPTION
Test
To start an ILS test, push the NAV control panel test switch when there is an ILS frequency active or push the front panel test switch. When the processor receives a test signal, it does a test of operation and receiver condition. Test results show on the front panel LED status indicators. The LRU status LED shows red for test faults or green if there are no faults. The control fail LED comes on red if there is no tuning input data from the control panel. The control fail LED will show green for valid tune inputs.
ILS - CONTROLS
EFIS Controls
To show ILS data on the captain’s and F/O’s displays, set the mode selector on the EFIS control panel to the APP position.
ILS - STANDBY ATTITUDE INDICATOR DISPLAYS
General
The standby attitude indicator gives the crew an alternate attitude indication source. The indicator also provides ILS data. You use the approach selector on the indicator to show ILS data. The approach selector has these positions:
· Off - no ILS data on indicator
· APP - ILS localizer and glideslope data shows
· B/CRS - back course ILS localizer data shows.
General
To show ILS displays on the ADI you must tune a valid ILS frequency on the NAV control panel and select it to the active display window.
NCD Display
When the ILS data goes to an NCD condition, the CDS shows the localizer and glideslope scales and removes the pointers.
Fail Display
The amber LOC flag replaces the localizer deviation pointer
and scale when the localizer receiver function has a failure. The
amber G/S flag replaces the glideslope deviation pointer and
scale when the glideslope receiver function has a failure.
ILS - EXPANDED ILS DISPLAY
General
To show ILS displays on the CDS, set the EFIS control panel mode selector to the APP position. You must also tune a valid ILS frequency on the NAV control panel.
NCD Display
When the ILS data goes to an NCD condition, the CDS shows the localizer and glideslope scales and removes the pointers.
Fail Display
For invalid ILS data, the CDS replaces the localizer deviation
scale and indicator with the amber LOC flag when the localizer
receiver fails. The amber G/S flag replaces the glideslope
deviation scale and pointer when the glideslope receiver fails.
ILS - CENTERED ILS DISPLAY
General
To show the centered ILS NAV display, push the CTR switch on the EFIS control panel mode selector switch.
NCD Display
For an ILS NCD condition, the CDS displays the localizer and glideslope scales and removes the deviation bar and glideslope pointer.
Fail Display
For invalid ILS data, the CDS replaces the localizer scale and deviation indicator with the amber LOC flag when the localizer receiver fails. The amber G/S flag replaces the glideslope scale and pointer when the glideslope receiver fails.
Test
When you push the test switch, the MMR does a check of the internal operation and its interface with other airplane systems. The test takes approximately 36 seconds. This is the test sequence that shows on the LED status indicators during the test:
· 0 to 2 seconds - the LRU STATUS, the CONTROL FAIL, and the ANT FAIL LEDs come on red
· 2 to 4 seconds - the LRU STATUS LED is green and theCONTROL FAIL LED is red
· 4 to 6 seconds - all LEDs go off
· 6 to 36 seconds - test status shows.
The LRU STATUS segment shows red when there is an internal failure in the MMR. Green shows that the MMR is operating normally.
The CONTROL FAIL segment shows red when an interface to the MMR has a failure. Green shows that all the interfaces to the MMR are normal.
NOTE: The ANT FAIL LED is not used at this time.
ILS - SELF-TEST
Test
You use the NAV control panels to do an ILS test from the flight compartment. The captain NAV control panel does a test of MMR 1 and the first officer NAV control panel does a test of MMR 2.
You need to set these controls to do an ILS test:
· Enter a valid ILS frequency into the active frequency display window on the NAV control panel
· Set a course on the DFCS mode control panel that is within