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LLZ 421
Operation and Maintenance Fault Location
ILS 420
6−23
Ed. 01.10 SOAC
6.5 FAULT LOCATION
6.5.1 General
Fault location in the ILS (LLZ and GP) can be executed with the PC User Program (see Section 6.5.2).
In the Localizer CRSCSB/CRSSBO for Course and CLRCSB/CLRSBO for Clearance are used as
terms for the RF signals.
You should print out all settings, BITE values and monitor values of the transmitter, the monitor and
LCP on the finally set system that has reached operating temperature. This data consists of the refer-
ence values, a knowledge of which will substantially facilitate troubleshooting. These values are as-
sumed for the following troubleshooting procedure. If HF modules are replaced, the printout should
be updated because HF modules have greater tolerances. This log of the ACTUAL state is a basis
for the troubleshooting procedure.
NOTE: For the LLZ in Hot Stby−mode, there will be the need of a connected emergency battery
in case of one AC/DC converter is switched off or shutdown by a fault.
6.5.2 Fault Evaluation with PC and PC User Program
Any fault is stored in the system memory, which occurs in the installation and is acknowledged by
the internal BIT and which leads to a WARNING or ALARM indication. Fault location in Navaids 400
can be performed by use of the BIT report in the PC user program. This report is available in the config-
uration menu of the PC user program:
− Move mouse cursor to field TRANSMITTER or MONITOR or LRCI.
− Click twice left mouse button for more data information about transmitter or monitor or LCP. The
ensuing BIT results are displayed and can be interpreted or printed out.
6.5.3 Fault Location Support ILS−Localizer (2F or 1F, if applicable)
In addition to the BIT check results (see 6.5.2), the following fault location tables list typical faults,
which may occur in an ILS−LLZ installation. The tables contain 5 columns: Step, Fault, A to C. To
execute fault location in the following tables, start with left column and proceed to the right following
A, B or C, and then from next row in A to C, if necessary.
6.5.3.1 Fault Location with Indicators at Power Supply and Modules
The BIT data report (see 6.5.2) indicates faulty operating voltages, so that the defective module
(AC/DC converter or DC/DC converter) can be defined and replaced. Before replacing the AC/DC
converters, check mains power supply. Before locating a fault, try to define roughly the defective func-
tional group, i.e. power supply, transmitter, antenna, monitor or LCP. A first localization is done by eval-
uating the LED indicators on the various modules.
Step Fault A B C
1 ACC Power LED off? ACC switched to ON? Check mains power sup-
ply to ACC or change ACC
2 DCC−MV green LED off? ACC switched to ON?
TX1/TX2 switched on? Check power supply to
DCC or change DCC
3 LCP Live−lamp off? DC operating voltage ok? Reset LCP
LCP,
not operable No DC voltage supply?
TX1 and/or TX2 switched on? DC operating voltage 5V of
DCC−5 available? Check fuse F4. Replace
once if blown.
4 LG−M CPU_NORM lamp off? DC operating voltage ok? Reset board
5 LG−A CPU_NORM lamp off? DC operating voltage ok? Reset board