Ehsi Deviation Scaling (If Hsi/Cdi Is Driven By The Gtn Via Serial Data) - Garmin GTN 625 Installation Manual

6.12.2.4 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 6.11.1).
2. Ensure that the SN3500/4500 is receiving valid heading.
NOTE
The Vertical Deviation Indication will not be displayed unless the SN3500 is receiving
valid heading.
3. While the GTN is displaying the 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 SN3308 displays NAV 1 or 
NAV 2 (depending on what navigation source the GTN is).
7. Ensure that the NAV1 (or NAV2) indication does not have a red line through it.
6.12.3

EHSI Deviation Scaling (If HSI/CDI Is Driven by the GTN Via Serial Data)

If the GTN has a serial connection to an EFIS display, proper scaling of the EFIS CDI and VDI must be
verified.
1. Cycle power to the GTN and acknowledge the prompts until it gets to the Instrument Panel Self
Test page (see Section 6.11.1).
2. With the Instrument Panel Self Test displayed on the GTN, look at the EHSI/EFIS and verify that
the lateral deviation is not flagged and half-scale left.
3. With the Instrument Panel Self Test displayed on the GTN, look at the EHSI/EFIS and verify that
the vertical deviation is not flagged and half-scale up.
NOTE
If the deviations are not as described, the EHSI/EFIS does not scale the GTN deviations
properly and cannot be certified for GPS-based guidance. Contact Garmin for further
assistance.
GTN 625/635/650 TSO Installation Manual
Page 6-64
190-01004-02
Rev. F