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UH1CW2 02-13-2018 09:47 AM

GRT Sport SX will not track GPS
I was hoping someone could help me with an EFIS issue. I have the GRT 2 axis autopilot in the plane. I am using an Garmin 250XL to drive the EFIS on channel 1. During start-up the EFIS confirms the GPS signal. I can set the autopilot at altitude and it will hold heading and altitude. However it only tracks the heading bug. When I try to have it track the GPS course it wonders off course immediately. I have tried adjusting the gain with no luck. The BAUD rate is set correctly from the GPS to the EFIS. Is there something I am missing? I have even wired in the iFly 720 GPS to the EFIS on GPS channel 2. It recognizes the GPS input (no faults) and it does the same thing, wonders off course within a second or so. If I let the airplane continue on the autopilot it will turn away from the course line to a random heading and just keep going with no solid direction. As stated heading bug works great but it will not track a GPS course line. Note: in the past these two GPS's drove the TRIO system perfectly.

RV8iator 02-13-2018 10:44 AM

Make sure you have th corrcect NAV source selected under CDI/OBS softkey, and n the SET menu you have to tell the unit where to feed the EXTERNAL or INTERNAL flight plans from.

BobTurner 02-13-2018 01:44 PM

To go from heading track to tracking the gps:
1. Select your gps as the primary nav source;
2. Change “heading” to “ENAV”.
Do not select GNAV. That requires a gps that furnishes roll commands, etc., like a 430. It also needs an arinc interface.

UH1CW2 02-13-2018 05:06 PM

I have always selected GNAV as I though that was for GPS. ENAV is the correct driver for the Garmin 250 XL, GREAT!

I will also check where I am feeding my flight plans from.

All this time I have been following my flight plans with the heading bug. **** I should have asked this question sooner.

Again, THANK YOU!!!

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