[uk_figs]

Just finished installing the AV-30 HSI module to add the HSI/CDI functionality to the backup instrument. My current GNX 375 settings for the Dynon/TruTrak Autopilot use Speed LOW, GAMA 1, SDI Common which all works fine. The AV-HSI install manual suggests the GNX 375 be set to Speed LOW, GAMA 3, SDI Common. The TruTrak manual says GAMA 1.
I flew the systems (less the autopilot) today and everything seems to be working fine wrt to approach guidance but I am of course curious what the difference is between GAMA 1 and GAMA 3.
No real hits on google so I thought I would try the brain trust here.
Figs

 

[gmkonrad]

Just finished installing the AV-30 HSI module to add the HSI/CDI functionality to the backup instrument. My current GNX 375 settings for the Dynon/TruTrak Autopilot use Speed LOW, GAMA 1, SDI Common which all works fine. The AV-HSI install manual suggests the GNX 375 be set to Speed LOW, GAMA 3, SDI Common. The TruTrak manual says GAMA 1.
I flew the systems (less the autopilot) today and everything seems to be working fine wrt to approach guidance but I am of course curious what the difference is between GAMA 1 and GAMA 3.
No real hits on google so I thought I would try the brain trust here.
Figs

From my GPS175 manual:
Table 5-2 GPS 175 ARINC 429 TX Port 1
Selections
Options
Description
Format
Off. No units connected to this port.
GAMA Format 1. • GDU 620. • GAD 29. • GDU 37X/45X/46X
GAMA Format 3. • Aspen. • Sandel 3308, 3500, and 4500
Speed. Low. Standard, nominally 12.5 Kb per second
High. High-speed, nominally 100 Kb per second