What's new
Van's Air Force

Don't miss anything! Register now for full access to the definitive RV support community.

Autopilot and Nav/GPS's that drive it

UH1CW2

Well Known Member
I have a GRT EFIS with a Trio autopilot. I know a lot of you RV flyers have the autopilot coupled to a GPS for hands off approaches. Can someone provide a list of IFR GPS's or GPS/NAV units that will drive the autopilot and even shoot the missed approach? I know the NEW Garmin GTN's will but are there any other options other than a GTN or a 430,530 unit? Will a Garmin GNC 300XL shoot the approach and the missed? Any help with this is appreciated.
 
I have a Garmin 430W with GRT which I can shoot ILS/RNAV including the miss approach. I have never practiced the full miss approach with the ILS but the RNAV type certainly will drive the auto pilot to the published miss. I have TT A/P which has been working really great without any issues.

Hope this helps.
 
I have a grt Hx and HS, Trio Pro, and Garmin 420W gps. Also an SL30 nav com.
1. With the Efis out of the loop - Trio connected directly to the 420W - The autopilot will follow and execute a precision LPV approach.
2. With the nav or gps feeding the efis, and the efis directing the autopilot over the ARINC link, the autopilot will follow an LPV approach from the 420 or an ILS from the SL30. It will also execute the missed approach if guidance is available from the gps, or manually using the heading mode on the efis.

Only a WAAS gps can do the precision LPV approach, so the lower cost gps units you mentioned will not do it. With a TSO 129 box, like the Garmin 300, you can do a non precision approach with the autopilot tracking laterally (left- right) while you manually enter descents to the step down and or MDA altitude.
 
Also, there is lateral guidance on the missed approach, but not vertical, so you have to tell it to climb and where to level off, whether through an EFIS or directly on the auto pilot.
 
Thanks for the help

Thank you for all the input. I guess the answer to my question is; I need to get either a WAAS 430 or a GTN 650 to use the autopilot system to its full potential. I have the autopilot being driven by the GRT EFIS at this time. After reading the information it seems that the EFIS or WAAS GPS will drive the autopilot to do the same things so long as the WAAS GPS is feeding the autopilot directly or through the EFIS unit.

My initial problem is panel space as I have a long EZ and very little space to spare. I am using a 250XL and a King 125 at this time. I think I can make enough room by removing both and installing a 430 and a slim com radio. I think one nav/com radio will be enough since I already have a 122D in the panel. Anyway, I love the VAF Forum for all the willingness to share information and the experience of the builders. THANKS AGAIN.

Phil Camarda
 
Also, there is lateral guidance on the missed approach, but not vertical, so you have to tell it to climb and where to level off, whether through an EFIS or directly on the auto pilot.

This is correct. With the grt Hx you can pre-program the altitude of the hold on a miss, so you're down to 3 operations if you decide to miss: push 'miss' on the Hx; add power; and as you go past the MAP push OBS on the 420W to unsuspend and start sequencing for the miss.

That's for a gps approach. ILS misses can be a little more work.
 
Back
Top