Garmin GTN 6 series Maintenance Manual page 112

7.4.3.2.3 Two GTNs/Two SN3308s
1. Remove power from GTN #2.
2. Cycle power to GTN #1 and acknowledge the prompts until it gets to the Instrument Panel Self-
Test page (see Section 6.1.1). Select GPS1 as the navigation source by pressing the NAV key on
the SN3308 #1. Verify that GPS1 is displayed on the SN3308.
3. Ensure that the SN3308 is receiving valid heading. The Vertical Deviation Indication will not be
displayed unless the SN3308 is receiving valid heading.
4. While GTN #1 is displaying the Instrument Panel Self-Test page, verify that the SN3308 is
displaying the following data from GPS1.
 Course Deviation: Half-scale left deviation, TO indication, flag pulled
 Vertical Deviation: Half-scale up deviation, flag pulled
 Active Waypoint: GARMN
5. On GTN #1 verify that an OBS value is displayed (and not dashed out).
6. Acknowledge the self test on GTN #1 by touching the Continue key.
7. Select VLOC on GTN #1 and verify that the SN3308 displays NAV 1 or NAV 2 (depending on
which navigation source the GTN is).
8. Using a VOR test set verify that the CDI deviation on the SN3308 is displayed correctly.
9. Remove power from GTN #1 and apply power to GTN #2. Acknowledge the prompts until the
Instrument Panel Self-Test page is displayed (see Section 6.1.1).
10. Select GPS2 by pressing the NAV key on the SN3308.
Repeat steps 4 through 8 with the second GTN.
Perform the same procedure for the second SN3308. Ensure that SN3308 #2 is receiving valid heading by
ensuring the vertical deviation indication is being displayed.
7.4.3.3 Sandel SN3500/4500 Interface Check
If a Sandel SN3500/4500 EHSI has been connected to the GTN, the interface should be verified as
described in this section.
1. Cycle power to the GTN and acknowledge the prompts until it gets to the Instrument Panel Self-
Test page (see Section 6.1.1).
2. Ensure that the SN3500/4500 is receiving valid heading. The Vertical Deviation Indication will not
be displayed unless the SN3500/4500 is receiving valid heading.
3. While the GTN is displaying the Instrument Panel Self-Test page, verify that the SN3500/4500 is
displaying data from the GPS source.
 Course Deviation: Half-scale left deviation, TO indication, flag pulled
 Vertical Deviation: Half-scale up deviation, flag pulled
 Active Waypoint: GARMN
4. On the GTN verify that an OBS value is displayed (and not dashed out).
5. Acknowledge the self test on the GTN by touching the Continue key.
6. Select VLOC on the GTN and verify that the SN3500/4500 displays NAV 1 or NAV 2 (depending
on which navigation source the GTN is).
7. Ensure that the NAV1 (or NAV2) indication does not have a red line through it.
Repeat steps 3 through 7 for the second GTN, if installed.
System Maintenance Manual GTN 6XX/7XX Part 23 AML STC
Page 7-16
190-01007-A1
Rev. 6