INSTALLATION MANUAL
CMA-5024 GLSSU
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Page 14
November 21, 2008
to determine if the position output on the GLS bus is located at the GPS antenna or the navigation
center. A typical installation will not require a conversion from antenna position to the navigation center.
This is usually limited to large aircraft that are unable to locate the antenna close to the navigation
center. Refer to Section II.
E. Aircraft system integration
The following is the responsibility of the system integrator.
The aircraft systems will monitor the integrity and status data from the GLSSUs so that flight safety is
preserved. In turn, the aircraft systems will provide auxiliary data inputs, such as initial
time/date/position and heading/velocity/altitude from air data systems and inertial navigation systems
(DADS, IRS, INS), in order to enhance the performance and availability of the GLSSU.
The aircraft systems may use the navigational data outputs from the GLSSUs as-is, or may combine it
with other navigation data sources to form hybrid navigation solutions. In the later case, the Time Mark
busses (not shown in the figures above) will enable time-tagging the various data sources for precise
time-synchronization.
F. ARINC 743A-4 compatibility and retrofitting issues
The GLSSU is intended and can be used for retrofitting without changes an existing ARINC-743A-4
aircraft installation, such as for replacing the legacy CMC CMA-3012 GNSSU, with the exception of the
antenna which must be an active
antenna. The CMA-3012 was using a passive antenna connected via
a very short coaxial cable.
The GLSSU generally conforms to the applicable portions of ARINC Characteristic 743A-4 to the extent
described in this manual. The applicable portions are the form factor, the connectors J1 and J2, the
power consumption, and the ARINC 429 input/output data label format.
Mechanically, the GLSSU conforms to the alternate configuration of ARINC 743A-4 and complies with
the pinout for the 41 pin circular connector J1. The RF connector J2 is the specified TNC connector;
however it must interface with a TSO-C190 active antenna as required by TSO-C145b/146b (for class 2,
3, or 4 operation) instead of a passive antenna. Refer to Section II 3 A for antenna characteristics. The
approach connector J3 of the GLSSU may not be used in ARINC743A-4 retrofit installations that
implement only Class Beta-1 functions.
The polarity of the Time Mark pulse defined herein is the opposite of the ARINC 743A-4 characteristic in
order to maintain compatibility with the legacy system pinout that was designed to comply with ARINC
743.
Note: Swap the two Time Mark Hi/Lo connections defined in Figure 106 of Section II for connecting to
systems that require ARINC 743A-4 pulse polarity.
The GLSSU accepts all standard ARINC 429 labels per ARINC 743A-4 except for labels 204 and 320
that are ignored. Labels 312 and 313 are also ignored but only on the FMS/DADS bus. The GLSSU
accepts the optional PRAIM ARINC 429 labels per ARINC 743A-4; note that the APD Configuration may
change the PRAIM label number. The GLSSU accepts ARINC 419 input labels 203 and 212 per
encoding specified in Appendix A. Note that the GLSSU accepts several labels in addition to those
specified in ARINC 743A-4 in order to perform the SBAS related functions not included in this ARINC
characteristic.
The APD Configuration defines the polarity of the Air/Ground discrete input.
The document reference is online, please check the correspondence between the online documentation and the printed version.
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