Installation Instructions

190-01007-A3 GTN 6XX/7XX AML STC Installation Manual
Rev. 4 Page 5-69
5.5.4.9.1.13 Air/Ground Discrete
The GDL 88 AIR/GROUND discrete input is active-low, and can be configured to interpret whether the
aircraft is airborne or on the ground based upon whether the input is grounded or open.
If the GDL 88 AIR/GROUND discrete is not connected, then select Not Installed (default configuration).
If the GDL 88 AIR/GROUND discrete connected, and the aircraft air/ground state is On-Ground when
the input is grounded, the select Active for Ground. If the AIR/GROUND discrete is connected, and the
aircraft air/ground state is airborne when the input is grounded, then select Active for Airborne.
Table 5-58. GDL 88 Air/Ground Discrete Configurations
AIR/GROUND
Discrete
AIR/GROUND Discrete Input State GDL 88
AIR/GROUND State
Not Installed N/A N/A
Active for Ground
Open Airborne
Grounded On-Ground
Active for Airborne
Open On-Ground
Grounded Airborne
5.5.4.9.1.14 Pressure Altitude Broadcast Inhibit Switch
This setting configures whether the GDL 88 is interfaced with an external switch for controlling pressure
altitude reporting. If an altitude reporting selection switch is installed and interfaced to the PRESSURE
ALT BROADCAST INHIBIT discrete select Installed, otherwise select Not Installed.
5.5.4.9.1.15 Anonymous Mode
NOTE
If a Mode S Transponder is installed with the GDL 88, the UAT anonymity feature must
be disabled as to prevent two different aircraft addresses from being transmitted
(Transponder Mode S address and the GDL 88 temporary address).
This setting controls whether the UAT anonymity feature is available. Consult the aircraft operator for
guidance on whether this feature should be enabled. When enabled, and the flight crew selects the
anonymous mode with the transponder tuned to the VFR Code, the GDL 88 transmits a temporary
address instead of the aircraft assigned ICAO 24-bit address, and a call sign of “VFR.”
If it is desired to disable the UAT anonymity feature, select Unavailable (default configuration).
If it is desired to enable the UAT anonymity feature controlled by an interfaced display, select Display
Available. If it is desired to enable the UAT anonymity feature controlled by an anonymous selection
switch interfaced to the ANONYMOUS MODE discrete input, select Switch Available.