190-01115-01 G3X™/G3X Touch™ Avionics Installation Manual
Rev. AV Page 2-4
2.1.1.2 ADAHRS
The GSU 25 is the ADAHRS (air data, attitude, and heading reference system) unit for the G3X system.
An ADAHRS senses the aircraft’s attitude, measures all air data parameters, and calculates aircraft
heading.
Up to three ADAHRS units are supported. In a system with multiple GDU displays and multiple ADAHRS
units, each display can present data from a separate ADAHRS, and any GDU display may also be switched
to display data from any ADAHRS. Data from multiple ADAHRS units is also automatically cross-
compared, and disagreements are noted on the PFD display.
Each GSU 25 ADAHRS is connected to pneumatic pressure inputs for pitot, static, and angle of attack
(AOA). Connection of the AOA input is only required for GSU 25 #1, and is optional for GSU 25 #2 and
#3. For aircraft capable of indicated airspeeds greater than 300 knots, the GSU 25D is used.
The GSU 25 communicates with other LRUs using the CAN bus, and can optionally be connected to the
PFD1 GDU using RS-232 for redundancy. For GSU 25 installation information, refer to Section 17
and
Section 24
.
The older GSU 73 ADAHRS is also supported. The GSU 73 does not provide AOA data, but a system that
includes a GSU 73 may also include additional GSU 25 units. For GSU 73 installation information, refer to
Appendix F
and Appendix G.
In a system installed with one or more dedicated ADAHRS units and one or more G5 standby flight
displays, attitude and air data from the G5 will also be displayed on the GDU displays, in the event that
valid data is not available from any dedicated ADAHRS unit.
In a G3X Touch system installed with no dedicated ADAHRS units, attitude and air data from the G5 will
be used throughout the system, including for autopilot functionality, but will not be visible on the GDU
4XX displays.
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