©1999 Navia Aviation AS 21833-3.4 Maintenance Procedures
OPERATING MANUALNORMARC 7013
INSTRUMENT LANDING SYSTEM
C-11
A facility shutdown is required for this check.
e. Detailed Procedure.
(1) Ensure that the localizer course width and phasing are adjusted to optimum in accordance
with paragraphs 5-16.
(2) Dummy load the transmitter sideband-only (SBO) output port and the SBO feedline input.
With the PIR , take a reference DDM reading at the width monitor input from the monitor
recombining network. The reference reading should be near 0 DDM.
(3) Remove the dummy load and insert the 90° section in the sideband feedline. Restore the
sideband energy and note the DDM reading now obtained. The value should be near 0 DDM.
If found out of tolerance, investigation should be carried out. No adjustment exists. The moni-
tor phasing depends on the average of the antenna monitor return cables phasing.
(4) Remove the 90° section and restore the sideband energy to the sideband feedline.
(7) Measure the width ddm at the monitor combining unit. Compare the value to previous ref-
erence value. A typical value is 0.155 DDM. If found out of tolearance investigate the reason.
(8) Restore the facility to service.
5-18 AUDIO AND RF FREQUENCIES.
a. Object.
This procedure provides a method to measure the ILS facility audio and carrier frequencies.
b. Discussion.
The operating frequencies of an ILS facility must remain within specified limits of the author-
ized values. The rf body installed in the carrier or an antenna feedline is a convenient point to
obtain a sample for the rf measurement. The navigational audio frequencies are essential for
establishing the course and width, while the identification tone is a necessary indication of
facility availability and identification.
c. Test Equipment Required.
1. A frequency counter with 0.0001 percent (1 part per million (ppm)) or better accuracy.
d. Conditions.
The facility must be removed from service.
e. Detailed Procedure.
1. Connect a frequency counter to the transmitter CSB test connector. Note: For Two-fre-
quency localizer switch off the clearance transmitter. Switch off the 90 Hz tone and the
identity modulation. Record the tone frequency. Repeat the other two frequency measur-
ments switching on one tone at a time.
Note: All tones are originating from the same frequency source. There is no provision for
adjustment.
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