Thales 421, Эксплуатация и обслуживание, Страница: 144 / 256

LLZ 421
Maintenance Operation and Maintenance
ILS 420
6−4
Ed. 01.10 SOAC
6.2.2.3 Check of Carrier Frequency
Validate set station frequency with a frequency counter or similar. The measurement is performed at
the affected TX in Stdby mode (this RF path includes a 35 dB attenuator):
a) Switch off both TX1 and TX2. Remove RF cable from J25 (Stby CRS CSB) at PIN−Diode Transfer
Switch, rear side of cabinet. Connect Frequency Counter to J25 (stby CSB out).
b) Switch on both TX1 and TX2. Open dialog ’Transmitter1−Waveform Data#1’ and ’Transmitter2−
Waveform Data#1’. Note down value of ’CRS CSB SDM’ of standby transmitter. Set it to 0 %. Vali-
date indication of station frequency. After measurement, reset ’CRS CSB SDM’ of standby trans-
mitter to noted value. Change transmitter, repeat step b).
c) Finally switch off both TX and connect as normal again. Switch on both TX.
6.2.3 Performing Check of Shutdown Circuits and Control Logics
Transmitter shutdown occurs with the activation of either the modulation shutdown (Shutdown B,
modulation signal at LGA off), or the synthesizer shutdown (Shutdown A, synthesizer carrier genera-
tion off). To ensure that no latent failure exists in the shutdown paths (LGA or SYN) that would prevent
its capability, it is to verify that a transmitter shutdown occurs solely due to this path. To perform the
test, refer to section 6.2.8. Follow the procedure described in the ECU test data sheet.
6.2.3.1 Check of ECU Interlock Shutdown Control
NOTE: Perform this test only if the ECU Interlock function is really used.
Preparation: The runway to which the station under test belongs, must be the inactive one. The corre-
spondent station status must be ’OFF’. Verify that the DIP−switch SW1/2 at the ECU subassembly
is set to ’open’: Interlock enabled.
Test action Expected result
At the LCP of the station , perform a ’TX on’ command. The transmitter is turned on, but station remains not radiating
because the ECU keeps both shut down paths ’OFF’ (SYN and
MOD shutdown). Station status changes from ’OFF’ to ’Runway
OFF’.
After test has passed, return to normal operation
6.2.4 Performing Check of MIT Function
Test action Expected result
Set monitors to bypass; open dialog ’TX Integrity Test Waveforms’
for the transmitter that is on the aerial. Open dialog ’Integrity Test
Data’ for monitor 1 and monitor 2. Open dialog ’LRCI System
Status’.
Change test signal A DDM from 0.0 % DDM to 0.8 % DDM. Verify MON1 Test Signal A DDM goes to alarm.
Verify MON2 Test Signal A DDM goes to alarm.
Verify ’MON-1 Integrity Test Res.= failed’.
Verify ’MON-2 Integrity Test Res.= failed’.
Set test signal A DDM to 0.0 % Verify all reading return to normal conditions.
Change signal B RF level from 70 % to 80 %. Verify MON1 Test Signal B RF Level goes to alarm.
Verify MON2 Test Signal B RF Level goes to alarm.
Verify ’MON-1 Integrity Test Res.= failed’.
Verify ’MON-2 Integrity Test Res.= failed’.
Set signal B RF level to 70 %. Verify all reading return to normal condition.
Change test signal A SDM and B SDM to 35 % for LLZ. Verify MON1 Test Signal A SDM and B SDM goes to alarm.
Verify MON2 Test Signal A SDM and B SDM goes to alarm.
Verify ’MON-1 Integrity Test Res.= failed’.
Verify ’MON-2 Integrity Test Res.= failed’.
Change test signal A SDM to the original setting, change test
signal B SDM to the original setting. Verify all reading return to normal conditions.
End MIT verification test.
NOTE: The test values are referenced to the LGM MIT alarm limit defaults of the monitor integrity test signals:
LLZ − Mon. Integrity Test Test signal A RF Level SDM DDM Test signal B RF Level SDM DDM Unit
Default value 90 40 0 70 38 1.5 %
Alarm limit defaults Lower/Upper 88/92 39/41 −0.5/0.5 Lower/Upper 68/72 37/39 1.0/2.0 %