A new supplemental type certificate for interfacing Garmin GTN navigators with analog radio altimeters includes DAC International’s GDC62 to convert analog signals to Arinc 429 format. The STC includes using the GDC62 to act as the interface between the GTN and analog Sperry AA-300 or Collins ALT-55 radio altimeters; the GDC62 converts the analog input from the radio altimeters to Arinc 429 format. This enables avionics installers to retain these analog units rather than replace them with digital radio altimeters that are compatible with TCAS II digital processors and GPS receivers.

The STC was developed by Columbia Avionics and Aircraft Services “to allow the terrain awareness and warning system (Taws) A function in the GTN navigator to be enabled,” according to DAC International. Aircraft covered by this STC include the Cessna Citation 500, 550, S550, 560 and 560XL.