INSTALLATION MANUAL
CMA-5024 GLSSU
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Page 21
November 21, 2008
CAUTION: The #1 and #2 DME and ILS input busses to the GLSSU must carry identical
data streams. In other words, the dual DME/ILS inputs must be connected to
the outputs from the same DME/ILS instrument. The HIS will accept the
DME/ILS data only from input busses #1, or alternately if there is no activity on
busses #1, only from input busses #2. Hence the two DME/ILS look-alike
output busses will carry identical data streams.
CAUTION: The ILS and DME inputs will accept up to 30 data labels per 100 ms period. If
this limit is exceeded, the HIS in the GLSSU may not retransmit some of the
received data labels on the corresponding ILS/DME Look-Alike outputs. This
restriction applies when the HIS substitutes on-the-fly the GLS data to specific
received ILS/DME data labels (i.e. pin J3-18, ILS/GLS Source select input
discrete, being grounded; refer to the approach connector J3 pinout in section
I.6.B). The restriction does not apply when the HIS passes transparently the
received ILS/DME data labels (i.e. pin J3-18 being opened or GLSSU non-
operating).
The HIS acknowledges positively the actual approach selection by means of annunciators
actuated by discrete outputs from the GLSSU.
In case of main 28 VDC power input or GLSSU failure, the HIS continues operating using the 28
V HIS supply (if provided).
Note: In case of power failure or GLSSU failure, the ILS/GLS Source Select Discrete
will still operate. There will be no HIS output if selecting the GLS data source;
select the ILS data source in order to pass-through the original DME/ILS data.
CAUTION: The same DME instruments may be shared by the GLSSUs and other
equipments, each tuning dedicated DME channels. The Left/Right/Center
Look-Alike DME Channel APD (depending on the SDI setting) designates
which DME channels are intercepted by the HIS data router.
The HIS control logic expects that the DME will transmit sequential data blocks for each frequency
channel. Knowing this, the HIS will trigger on the Frequency label (ARINC 429 data label 035) of
the allocated DME channel to intercept the proper DME data block, up to and ending with the next
Frequency label.
CAUTION: The DME devices MUST
transmit sequential blocks of data for each DME
channel, Frequency label first, in accordance with paragraph 4.8 of ARINC
709-8 or of paragraphs 4.8.1 and 4.8.1.2.4 of ARINC 709A-1.
The HIS may be configured by the APD data to perform a data concentrator bridging function, whereby
it will process both the ILS and DME data from the DME inputs onto the DME outputs instead of
processing the ILS data on the ILS busses; The ILS input/output busses are not connected in such an
installation. Refer to Appendix E.
The document reference is online, please check the correspondence between the online documentation and the printed version.
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