GPS Steering

[SMO]

I have the EFIS AP IV with GPSS. I understand I in order to use this feature I need a GPS that provides an ARINC signal. I was planning to use a Garmin 696 but I find that it does not provide this signal. What are my options? Do you have a list of GPS units that provide the appropriate signal? Does the optional GPS from Trutrak provide this signal?

Mark Olson

[PhantomPholly]

First off, you don't need ARINC unless you intend to fly precision IFR GPS approaches.

There aren't a whole lot of certified IFR GPS's which provide this.

From page 22 of the manual, the following units are shown as providing ARINC:

Garmin 155XL
Garmin 200XL
Garmin 300XL
Garmin GX 50-65
Garmin GNS 480
Garmin 430 (and I believe 420)
Garmin 530 (and I believe 520)

Not all of these are certified for IFR; for those the only real benefit is that course interceptions will be a bit smoother and track will be steadier than with a serial GPS unit.

[SMO]

Are there any other GPS units that will work with the EFIS AP besides Garmin? In retrospect, I probably could have purchased the EFIS AP III instead of the IV. In order to take advantage of the features of the IV I should probably add a 430, but panel space becomes an issue in the Rocket.

I don't currently have an IFR rating but would like to get this in the next couple years.

[PhantomPholly]

I don't have the EFIS, just familiar with their autopilots (and according to a recent announcement, they pretty much all work the same way). Based on the features comparison, I believe you are correct that you are leaving functionality on the table with your installation - you may wish to ask TT if they would let you trade out for a lesser unit if you aren't going to install an ARINC capable GPS unit.

I find it interesting that using serial data compatible with an SL30 you can display / fly a VOR/ILS approach, but it still will not drive the autopilot:

SL30 NAV

With the serial wires from the SL30 to the EFIS connected. The EFIS
will display the VOR / ILS NAV information on the HSI. This
information does not command the FD or AP. With a valid SL30
NAV input, an ILS or VOR will be displayed over the CRS label.
Press and Hold the CRS button to display the information on the HSI.
The OBS radial will be displayed on the SL30 also.
The SL30 must be set for SERIAL output.

Why they don't offer the obvious "next step" to convert any NAV or GPS signal to autopilot steering is a question for TT to answer.