How big of a deal is this?

I am new to the experimental scene and trying to buy a RV8A that does not have an autopilot. The plane I am looking at has a Dynon D180, SL40, garmin handheld. I want to install a autopilot and have been looking at the Dynon site trying to understand what I need in order to have a 2 axis system. it would appear that I would need to purchase the AP74 and of course the servo's.
My questions are, 1) will I need the HSI module? 2) how bid an ordeal is it to add the autopilot and other items? and, 3) should I consider a different autopilot and servo's?
I appreciate any feedback you have.

All you need is the servos and the install kits. The auto pilot controls are all in the D180.

The AP74 gives you quicker access to auto pilot functions, but it adds no functionality.

He HS34 gives you an extra set of knobs, but it is basically an ARINC adapter. None of your instruments use ARINC, so it is not needed. You can connect your Gaemin handheld to the D180 via RS232 (which is the only format the GPS talks in).

Thanks. I was hoping that was the case on the AP74.

I didn't answer your 2nd and 3rd questions.

2. That depends on who is installing them. The hardest part may be running the wires. Connecting them isn't hard, and the install kits usually are quite easy to use. I don't know specifically on the -8A, but all of the other RV's are fairly easy. You only NEED 5 wires per servo, a pair of DSAB wires (twisted blue and green wires in your existing Dynon harness). They can just be spliced into the current wires and spliced together in just about any format. Then you need a power (red) and Auto Pilot Disconnect (yellow) and Ground (black). You can ground locally if necessary. Both servos get the same wires and you can run from ye panel to one servo, then from that servo to the other if that makes things easier. The wire colors I sed are the colors of the wires coming out of the servos. The power will need a 5A breaker fuse or switching breaker. The yellow wire needs a momentary switch that connects it to ground when pressed.

For future expansion, I recommend an extra pair of twisted wires (white/blue and white/green) in case you ever end up upgrading to Skyview, because they require 2 pairs of communication wires for redundancy.

3. IMHO, definitely not! This auto pilot will cost you $1,650 plus time and wire. You don't have an IFR panel, so going with a stand-alone auto pilot won't benefit you any. The auto pilot that works directly with your EFIS is the best way to go and the cheapest and easiest.

Ok, one more question. With that wiring set-up when you engage the autopilot does it engage both heading and altitude hold or can you engage separately?

Thanks again.

I was a beta tester for Dynon back when they were developing the AP for the D100/D180's. As mentioned, they work fine without the AP 74. However, that little unit really is a NICE to have as it lets you twist knobs rather than make multiple button pushes.

As Jesse mentioned, run the extra wires because it makes any future upgrade easier.

In fact, I would recommend you buy the pre-configured wiring harnesses from either Stein or Dynon. Then you can add a matching DB-9 connector on your servos and in the cockpit and make the pin-outs work for you. Then, if you upgrade (and there is no real reason to do that any time soon), you will just have to install Dynon's little 5 port DB-9 hub in the tail for the pitch servo and ADHRS unit, one in the panel for terminating everything and then it is simply plug-and-play.

In this picture, I added one more connector that ran forward to the panel. The wiring can't get much easier than that! (The zip-tie pad is glued in place with Goop Automotive Trim Adhesive after the sticky pad was removed. Seven years and 660 hours and not one has failed.)

You can engage them both separately, but if you use the disconnect switch to engage, it will do both. You can activate either or both via the screen or the AP74.

As WR said, the AP74 is really nice because of the knobs and buttons. Much quicker access, but not required.

Also note that if you are running extra wires for Skyview upgrade, the ADAHRS uses the two pairs of blue/green wires, but it uses different power wires from the servos (again, you can run ground(s) or ground locally. The adahrs also likes to have 2 separate power wires, and they can be smaller gauge because of the low power usage.

Another interesting note formSkyview is that all network cables have 9 wires, 2 powers, 2 grounds, 2 pairs of blue/green wires, and a ninth wire (Orange I think) that is only used by the EMS module. So, if your EMS module is plugged into one of the screens directly and you are making your own cables, then you only need 8 wires instead of 9. Or, if it's plugged into a hub, then only the cable going from the hub to the screen and the hub to the EMS module require the 9th wire.

Thanks for the info and the advise. I wish the panel was IFR capable but I don't think I want to intentionally go looking for the soup. If I get the deal done I might end up with more questions.

If you have any questions about Trutrak autopilots, please let me know. I'm happy to help.