ILS RELAY - REMOVAL/INSTALLATION
EFFECTIVITY
AS Airplanes Incorporating SB 34-1139 SD ALL EXCEPT ST-AFK and ST-AFL WA ALL EXCEPT N4502W thru N4530W, N4569N and N4571M GJ B-2509 and B-2510
1. General
A. Two ILS relays are installed in electronic equipment rack E3-4. Each relay has 3 coaxial cable connectors and 4 wire terminal connections.
2. Remove ILS Relay
A. Open applicable VOR/LOC 1 (P18 panel) on VOR/LOC 2 (P6 panel) circuit breaker.
CAUTION: WHEN CONNECTING AND DISCONNECTING COAXIAL CABLE CONNECTORS, ENSURE THAT CABLE DOES NOT TWIST OR ROTATE. DAMAGE TO CABLE CAN OCCUR.
B. Disconnect coaxial cable connectors from relay.
C. Disconnect electrical wires and tag for reinstallation.
D. Remove mounting screws and remove relay.
3. Install ILS Relay
A. Position relay to mounting base and install screws.
CAUTION: WHEN CONNECTING AND DISCONNECTING COAXIAL CABLE CONNECTORS, ENSURE THAT CABLE DOES NOT TWIST OR ROTATE. DAMAGE TO CABLE CAN OCCUR.
B. Connect electrical wires and coaxial cables to relay as tagged during removal or per applicable wiring diagrams. Hand tighten cables.
C. Close circuit breaker opened in 2.A. above.
D. Test relay for satisfactory operation by performing "Prepare To Test System" and "Test VOR-Localizer Antenna Switching Function" portions of VOR/ILS Navigation System Adjustment/Test procedure. (Ref 34-31-0)
E. Remove airplane electrical power if no longer required.
May 01/99 34-31-71 Page 401
BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details.
MARKER BEACON SYSTEM - DESCRIPTION AND OPERATION
1. General
A. The marker beacon system provides the pilots with both visual and aural indication of airplane passage over airways fen markers, station location Z markers and instrument landing system (ILS) middle and outer markers.
B. The marker beacon system consists of a receiver, an antenna, two sets of three indicator lights and a sensitivity switch. (See figure 1.)
C. The ground marker beacon transmitters all operate on a fixed frequency of 75 MHz and are modulated by one of four audio signals, depending on the type of marker beacon. The signals, received by the airborne receiver as the airplane passes over the transmitter, are made to light indicator lights. The audio signal is also made available to the crew by actuation of the MKR control on the audio selector panels. Following are the four types of marker beacons with their tone frequency and indicator light color.
(1)
ILS Outer Marker - An intermittent 400-Hz tone with the blue light flashing.
(2)
ILS Middle Marker - An intermittent 1300-Hz tone with the amber light flashing.
(3)
Airways Fan Marker - An intermittent 3000-Hz tone with the clear light flashing.
(4)
Station Location Z Marker - A steady 3000-Hz tone with the clear light steadily lighted.
D. When an ILS middle marker signal is received, this information is fed to the flight director system for the low approach mode. (Refer to 34-26-0, Flight Director System.)
2. Receiver
A. The receiver is a single conversion crystal-controlled superheterodyne operating at a fixed frequency of 75 MHz Sensitivity of the receiver is variable and controlled by a switch located an the captain's instrument panel. Audio filters tuned to 400, 1300, and 3000 Hz are used for separation of the three types of tone modulation used by the beacons. The receiver, which contains an integral power supply, is installed on the electronic equipment rack (E-2).
3. Antenna
A. The antenna is a blade-type unit located on the bottom centerline of the airplane at body station 620. The antenna is connected to the receiver by a coaxial cable.
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Feb 15/73 BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details. 34-35-0 Page 1
L36404
Marker Beacon System Component Location 5C8
34-35-0 Figure 1 Jun 20/88
Page 2
BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details.
4. Indicator Lights
A. There are two sets of three indicator lights, one set is on the captain's instrument panel, and the other is on the first officer's instrument panel. The lights are covered by white, blue and amber lens and are the push-to-test type.
5. Sensitivity Control
A. On GJ ALL EXCEPT B-2504 and B-2505, the sensitivity switch is located on the captain's instrument panel adjacent to the marker beacon indicator lights. On GJ B-2504 and B-2505, the sensitivity switch is located on the selcal control panel, installed in the forward electronic control panel. The LOW and HI positions of the control indicate the degree of receiver sensitivity and are normally used when the airplane is flying at low or high altitudes respectively.
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