Garmin GNC 255 Installation Manual - page 72

GTR 225/GNC 255 TSO Installation Manual

190-01182-02

Page 6-18

Rev. B

6.6.5 Interface Checkout

This section describes the checks that must be carried out to verify that systems interfacing to the 

GTR/GNC are communicating properly. Only those interfaces that are connected to the GTR/GNC must 

be verified.

6.6.5.1 External RMI/OBI Interface Check (GNC Only)

If the VOR OBI output from the GNC is connected to an RMI navigation indicator verify the interface as 

described in this section. If the following steps do not perform correctly, check the electrical connections 

and configuration setup. The aircraft heading system must be operating properly in order for the RMI 

needle to point correctly.

1. Apply power to the equipment.

2. If installed, set the RMI select switch to the VLOC position.

3. Tune a local VOR station, or use a simulated signal from an approved VOR Test System.

4. Verify that the RMI needle swings and points toward the VOR station.

6.6.5.2 DME Tuning Check (GNC Only)

1. If the GNC is set up to remotely channel a DME, verify the interface as described in this section.

2. Select a VOR/ILS channel that corresponds to (1) a DME station within a 40 nautical mile range, 

or (2) the frequency of a DME ground tester.

3. Verify that the DME locks on to the signal and a valid distance is displayed.

4. Tune an invalid VOR station. Verify that the DME data is flagged.