D. Functional Description, VOR/ILS Self-Test Operation
(1)
VOR/ILS self-test provides the VOR and ILS self-test audio signals, timing sequence for control of the flags during self-test, and the automatic self-test timing and control. A self-test is initiated by the test switch on the receiver front panel or on the VHF NAV control panel. The switch(es) control a preprogrammed Read-Only-Memory which generates the VOR test, DN/R test, UP/L test and End test outputs.
(2)
The self-test oscillators outputs are applied to the input of the VHF and UHF receiver sections to simulate a VOR signal on any VOR channel or localizer and glide slope signals on any ILS channel. These signals provide an overall operational test for the VOR/ILS navigation system.
(3)
Prior to self-test initiation, control logic will allow normal operation of the GS and VOR/LOC flags. When self-test is initiated, the GS and VOR/LOC flags will be driven out of view and remain out of view through completion of test. There is up to a 5-second delay on flag action for VOR test and no delay for ILS test.
EFFECTIVITY
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(4) Automatic self-test provides for self-testing in the VOR mode if a failure has been detected. The End test will stop self-test even if a self-test input is present.
E. Control
(1) Turn-On Procedure (Fig. 3)
(a) Provide electrical power to system (Ref 24-22-00, Maintenance Practices (Apply Power)
CAUTION: MAKE SURE THAT THE EQUIPMENT COOLING SYSTEM IS
_______ OPERATING BEFORE TURN-ON OF THE ELECTRICAL OR ELECTRONIC SYSTEMS OR HEAT DAMAGE COULD RESULT. (REF 21-58-00, ADJUSTMENT/TEST).
(b)
On electronics circuit breaker panel P7, check that the following circuit breakers are closed: ATT ADI 1, ATT ADI 2, CAPT FLT INST SW RELAYS, F/O FLT INST SW RELAYS, GS 1, GS 2, HDG SYNC EXCIT 1, HDG SYNC EXCIT 2, HDG SYNC EXCIT 3, HSI 1, HSI 2, MHRS 1, MHRS 2, RMI 1, RMI 2, VOR 1 AC, VOR 2 AC, VOR 1 DC, and VOR 2 DC.
(c)
On overhead lightplate circuit breaker panel P126, check that GS3 and VOR 3 circuit breakers are closed.
(d)
Set captain's and first officer's VOR/ILS-INS transfer switches to VOR/ILS.
(e)
Set the VOR/ILS transfer switch to the center position. (Capt 1 - F/O 2).
(2) Shutdown Procedure
(a)
Turn off equipment.
(b)
Remove electrical power if no longer required (Ref 24-22-00).
F. Functional Description, Relay Control (Fig. 4)
(1)
The selection of the two VOR/ILS receivers being used is controlled by the captain's VOR/ILS transfer switch which, in turn, controls the positions of the captain's and first officer's VOR/ILS relays. With the VOR/ILS switch in the center or normal position, the relays are set to provide data to the captain from receiver NO. 1 and to the first officer from receiver No. 2. If either receiver No. 1 or 2 should malfunction, receiver No. 3 may be used as an alternate.
(2)
The VOR/ILS position annunciator lights provide an indication of the VOR/ILS receiver being used by the pilots.
(3)
If, for example, the VOR/ILS transfer switch is set to CAPT 3 -F/O 2 position, 28-volt dc power will be applied through the switch to the stepping solenoid of the captain's VOR/ILS relay causing the relay to switch from the No. 1 position to the No. 3 position. While the captain's VOR/ILS relays are in the alternate No. 3 position the dc path to the first officer's VOR/ILS relay solenoid is broken, thus preventing the captain's and first officer's VOR/ILS relays from being in the No. 3 position simultaneously.
(4)
If the autopilot is coupled to a VOR/ILS receiver and the alternate VOR/ILS receiver is selected, a deviation switching discrete signal is applied to the AP accessory box No. 2 which will uncouple the autopilot from the VOR/ILS navigation system.
EFFECTIVITY
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(5) The radio/INS transfer relays and VOR/ILS-INS switches control the selection of either INS or VOR/ILS data for display by the pilots' flight instruments.
G. Functional Description, Antenna Switching (Fig. 5)
(1)
Radio frequency signals from the VOR and localizer antennas are applied to the three VOR/ILS receivers. VOR and localizer rf is switched to the receivers as determined by the mode selector switch on the AP/FD NAV mode selector panel and the position of the captain's and first officer's VOR/ILS A transfer relays. RF switches 1, 2, and 3 direct rf from the VOR antenna to the receivers when the mode switch is in the INS, HDG, or VOR LOC position and rf from the localizer antennas when the mode switch is in the LAND or ILS position after localizer capture has occurred, RF switches 4 and 5, controlled by the VOR/ILS A transfer relays, direct the VOR/LOC rf to the two receivers that are in use.
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