Garmin GDL 88 User Manual

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6-1
190-01122-03  Rev. A
GDL 88 ADS-B Transceiver Pilot’s Guide
INSTALLATION CONFIGURATIONS
6.1 
Possible Installation Configurations
6.1.1 
GDL 88 with ADS-B Out Transmission Enabled
The GDL 88 can provide for both the ADS-B Out and ADS-B In functionality.
In this case, the GDL 88 transmits ADS-B messages on 978 MHz and receives
ADS-B, ADS-R, TIS-B, and FIS-B services on the 1090 and 978 MHz links using
its dual link receive capabilities. This installation is limited by FAR 91.227 to use
below FL180.
6.1.2 
GDL 88 with ADS-B Out Transmission Disabled
With ADS-B Out transmission disabled, the GDL 88 can provide for only ADS-B 
In functionality. In this case, the GDL 88 receives ADS-B, ADS-R, TIS-B, and FIS-B
services on the 1090 and 978 MHz links using its dual link receive capabilities. In
order for the ADS-B Out mandate to be met, another LRU, Such as a Garmin GTX
330ES transponder, must be installed that complies with the ADS-B Out mandate 
on either the 978 MHz or 1090 MHz link. For aircraft operated above FL180, a
1090 MHz ADS-B Out compliant LRU will be required.
6.1.3 
GDL 88 Only – No Display
In  a  minimal  installation,  the  GDL  88  provides  the  required  ADS-B  Out
functionality with a standalone set of annunciators and control switches installed 
in the cockpit. When a GDL 88 is installed without interface to an external 
display, some ADS-B In functionality is still retained. A traffic annunciation light
is installed in the cockpit for CSA alerts and aural alerts are provided for these 
threat aircraft, to include directionality from the ownship and range.