INSTALLATION MANUAL
CMA-5024 GLSSU
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without prior written permission by CMC Electronics Inc.
Page E.17
Revision 1 Jan 19, 2009
(5) SBAS Selection Threshold
While the GLSSU is in SBAS PA mode, it retains the same SBAS satellite signal as a source
of correction and integrity data when the protection levels obtained with this data are within
the SBAS Selection Thresholds (and also within the applicable alarm limit when an approach
is selected).
When the GLSSU is operated as a class Delta-4 equipment by selecting an approach, the
SBAS Selection Thresholds are normally set to their maximum value of 500 m so that the
selected source of data remains the same as long as it meets the alarm limits of the
approach. When the GLSSU is operated as a class Beta-3 equipment without selecting an
approach, there is no alarm limit available to decide when to change the source of data. The
SBAS Selection Thresholds are then set to the lowest HAL/VAL value expected for the types
of approaches to be flown. For the WAAS service provider the expected HAL/VAL for an
LPV 200 feet approach is 40/35 meters.
(6) Approach Monitor Deactivation Threshold
This APD contains the distance to the runway threshold (LTP/FTP) at which the Approach
Monitor is deactivated. The recommended value is 0.04 nm.
(7) SBAS PA Mode Range Limit
The SBAS PA Mode Range Limit specifies the maximum range at which the GLSSU will
enter SBAS PA mode automatically. A value of 0 specifies the absence of such a limit. When
the Automatic SBAS PA Mode Control APD is enabled and the distance to LTP/FTP is not
within the SBAS PA Mode Range Limit APD, the proportional and rectilinear deviation labels'
SSM are set to NCD.
(8) Equipment ID
This APD contains the equipment ID assigned to the GLSSU and reported in label 377. A
distinct value can be specified for reporting by the “GLS bus” type and by the GPS bus type
to allow downstream equipment to distinguish which type of bus is received. ARINC 743A
specifies a hexadecimal ID of “00B”. This is the recommended setting for both bus types.
(9) GLS/GPS ARINC 429 Output Bus Type
This APD specifies the type of ARINC 429 output bus provided on each of the 3 configurable
GLS/GPS ARINC 429 Outputs on the Approach aircraft connector J3. Each bus is
configured separately. Since three “GPS bus” type busses are provided on the Navigation
aircraft connector J1, the typical setting is a “GLS bus” type.
The “GPS bus” type is used for backward compatibility with equipment that cannot support
the faster transmission interval for the navigation information and deviation data or will
misinterpret the new labels of the “GLS bus” type busses. Some IRU are known not to
support the higher data rates. Also the “GLS bus” type is high speed only. The “GPS bus”
type can be configured high or low speed per ARINC 743A-4. The GPS bus is provided for
maximum compatibility with ARINC 743A-4. At least one output must be of type “GLS bus” to
conform to TSO-C145b/146b.
The document reference is online, please check the correspondence between the online documentation and the printed version.
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