INSTALLATION MANUAL
CMA-5024 GLSSU
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Page A.16
Revision 1 Jan 19, 2009
1.2.10 ARINC 429 OUTPUT STATUS/SIGN MATRIX (SSM) BITS PROCESSING
The following SSM conventions apply to data generated by the GLSSU. Specific conventions for the
digital deviation data are described later in this section. The GLSSU stops all transmissions on an
ARINC 429 output when it cannot control its SSM bits.
The GLSSU outputs labels with the SSM bits set to Normal. Unless other conditions force a SSM
setting of Fail Warning, the SSM is set to NCD whenever the value cannot be calculated or exceeds the
maximum range permitted. The GLSSU sets the SSM bits to Functional Test while the related
Functional/Guidance Tests are active.
While in fault mode, the SSM bits are set to Failure warning or NCD for label where an SSM of Fail
Warning is not defined, except for labels 156, 157, 273, 305, 306, 307, 350, 352, 354, 355, 371, 373,
375, 376 and 377, which are maintained in Normal state.
ARINC 429 output Status/Sign matrix (SSM) bits processing for the digital deviation data only
The GLSSU annunciates as follows the validity of the ARINC 429 data labels 117 & 171 or 174 which
contain the vertical deviation data, and 116 & 173 which contain the lateral deviation data:
- These ARINC 429 data labels are not transmitted during the Self-Test.
- The SSM bits are set at "Functional Test" during the Guidance Test of the proportional deviation
data. Refer to Section III 3. C. (3) (b). Note that when the GLSSU is in Fault mode, the SSM are
set to "Fail Warning".
- SSM are set to "Normal Operation" when the data is valid.
- SSM are set to "Fail Warning" for a navigation alert.
- SSM are set to “No Computed Data” for any of the following conditions:
- No approach is selected
- The approach is parked
- The "Attitude Data Used" APD is enabled and no attitude data is received for one second.
If the GLSSU cannot control properly the SSM bits, it stops all data transmissions on the affected
ARINC 429 output bus.
1.2.11 ARINC 429 OUTPUT DATA FORMAT
The GLSSU outputs the ARINC data labels listed in Figures A-12 to A-15 below, respectively for the
GPS, GLS, ILS and DME output busses. The same notes apply to the 4 figures.
For the format of the data labels, refer to Appendix C when the note (j) applies or else refer to the
standard ARINC 743A characteristic. The presence of some of these labels is controlled by the APD
as identified by notes (e) and (s) in Figure A-12 and by note (e) in Figure A-13; the data format of a few
labels is also controlled by the APD. Refer to Appendix E for details on the APD.
The document reference is online, please check the correspondence between the online documentation and the printed version.
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