Van's Electrim trim - compatible with Autopilot?

[TroyW]

I'm wondering, as I build my RV-7 tail, if the electrim trim servo I ordered (The Ray Allen Trim System) from Van's will be compatible with the TrueTrak DigiFlight autopilot.

If the TrueTrak uses it's own pitch (elevator) trim servo, then I don't want to install the electric trim I ordered from Vans with the empennage.

Unfortunately, I haven't been able to find this question asked before. Would appreciate your thoughts.

Thanks,

Troy Whistman
RV-7 empennage
Fort Worth TX
www.whistman.com < build blog

[TroyW]

What I'm seeing online (at TruTrak's site and other sites) is that the pitch servo used by the autopilot is entirely independent and separate from elevator trim... The pitch servo connects to the elevator push/pull tube and controls the elevator directly, while the elevator trim works the elevator trim tab. Correct? So I install both my Van's elevator trim servo system, and later I'll install the autopilot pitch servo (in the fuselage). Yes?

[Ironflight]

Troy,

I guess it depends on what you mean by the term "compatible". I have the Tru Trak AlTrak and the Ray Allen electric trim in my RV-8. They both work great - but they are totally indpendant of each other. I have the very simple AlTrak (without the trim sensing servo), and if you punch up Alt Hold with the plane too far out of trim, it blinks at you and eventually disconnects. No problem - just trim it out and re-engage. the trim servo drives the tab, and the pitch servo drives the elevator pushrod directly.

I'm quite happy with both, and with my setup.

Paul

[TroyW]

Thanks, Paul, that makes a lot of sense. I think when I wrote the first post, I was thinking the autopilot system used the elevator trim servo for pitch control; after reading TruTrak's manuals, and seeing pictures of other people's installations, I think I understand correctly now that the autopilot's pitch servo controls the elevator directly, not the elevator trim... and thus, as you say, the systems are totally independent of each other.

Originally Posted by Ironflight

Troy,

I guess it depends on what you mean by the term "compatible". I have the Tru Trak AlTrak and the Ray Allen electric trim in my RV-8. They both work great - but they are totally indpendant of each other. I have the very simple AlTrak (without the trim sensing servo), and if you punch up Alt Hold with the plane too far out of trim, it blinks at you and eventually disconnects. No problem - just trim it out and re-engage. the trim servo drives the tab, and the pitch servo drives the elevator pushrod directly.

I'm quite happy with both, and with my setup.

Paul