INSTALLATION MANUAL
CMA-5024 GLSSU
This document includes Proprietary Information and shall not be reproduced or communicated to third party
without prior written permission by CMC Electronics Inc.
Page 204
November 21, 2008
The test consists in monitoring a test pattern of the proportional deviation output data and the
associated deviation flags on the GLS and ILS bus from the GLSSU using the EDS in the
cockpit. For installations that cannot display the deviations during the guidance test, refer to the
aircraft documentations for the installation test procedure that verifies that the aircraft systems
receive the deviation data.
For activating manually the guidance tests, ground the Functional/Guidance Test discrete input,
after ensuring that the Tune/Guidance Test Inhibit Discrete Input pin is open; the guidance test
will begin about 1 second after manual activation. However, this action may activate firstly the
self-tests as described in section a) above; in this case, the guidance tests will begin about 7
seconds after the end of the self-test.
Another alternative is using the FMS or alternate means to activate the Guidance test; refer to
the applicable equipment manual for operating instructions. An acceptable alternate means is
using an ARINC 429 bus emulator for sending either the data label 33 or the Guidance test
command on the Command Summary Word, ARINC data label 227; refer to Appendices A and
C for information.
With the GLSSU operating, activate the Guidance Test as described above. This action
activates a deviation output data test pattern, for about 15 seconds total. Keep observing the
vertical and lateral deviation displays and their flags, and check that the deviation test data
sequence generated by the GLSSU is as follows:
i) The SSMs are set to "Failure Warning" and lateral and vertical output deviation are set to 0
DDM for a period of three seconds (nominal).
ii) The SSMs are set to "No Computed Data" and lateral and vertical output deviations are set
to 0 DDM for a period of two seconds (nominal).
iii) The deviation values of -0.085 DDM (Up) and -0.075 DDM (Left) are present for three
seconds nominal with the SSMs set to “Functional Test”.
iv) The deviation indication sweeps from up to down and left to right, in two seconds nominal
with the SSMs set to “Functional Test”.
v) The deviation values of +0.085 DDM (Down) and +0.075 DDM (Right) are present for six
seconds (nominal), with the SSM set to “Functional Test”.
vi) End of the test; return to normal operation.
In addition, verify during the Self-Test mode and during the Guidance Test that the following
discrete outputs are toggling:
Approach Tuned Discrete output,
Approach Available Discrete output,
System Valid Discrete output.
Note that the GPS Fault Discrete output may also toggle during Self-Test mode.
The GLSSU may be defective if the observed test pattern differs from the expected one, described
above. Specifically, deviations that remain at full-scale up/right or are not output during the test
indicate a problem with the installation. Note that some EDS will display deviations only when the
label SSM bits are set at Normal Operation. Since the fault may reside in the external wiring or
The document reference is online, please check the correspondence between the online documentation and the printed version.
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