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RV-3: Autopilot Pitch Servo installation

Ironflight

VAF Moderator / Line Boy
Mentor
As is the case for many things on the RV-3, there are no drawings or kits to help with the installation of an autopilot and the associated servos. Since we are planning to have the airplane IFR capable, and it sure is going to be ?single pilot? IFR, we consider an A/P to be essential. That meant coming up with a pitch servo installation. Fortunately, it really isn?t very difficult ? as long as you have built an RV-8 first! When I cut the angles to mount the elevator bell crank a few months ago, I anticipated the installation, and built them to match the measurements on the -8. This worked out very well, as I had plenty of room to mount the servo, and the pushrod length was also perfect. So if you are going to mount a pitch servo in a -3, just download the -8 drawing from Tru Trak (or get that kit), and have no worries ? it all fits!

Rough assembled with temporary hardware:
IMG_4773.JPG


You need to assemble it in the right order ? there is a mounting bolt for the port-side angle hidden underneath the servo ? it needs to be attached first, then the servo, then the starboard angle (again, temporary hardware):
IMG_4774.JPG


Paul
 
Hi Paul,

I'm installing a Dynon system including 2-axis autopilot in my old RV-3. Your pitch installation looks essentially the same as mine, but I'm scratching my head on the roll installation. It should be essentially the same as most other Van's models, but the stick assembly doesn't have the clearance to bolt the pushrod to the bottom of the stick. Before I modify the assembly itself or resort to clamping a strap around the aileron pushrod, did you figure out a "better way" to control roll?

Just curious,

Bob Knauff
RV-3 N65ZM
 
Hi Bob,

While I generally prefer to keep all of the servos in the fuselage for ease of wiring and maintenance, I agree - in the case of the -3, there just isn't the room. We went with the Tru Trak install kit for a -6 right at the aileron bellcrank. Louise did it, actually, and only had to do a little bit of a mod to the diagonal brace due to the thinner wing. The servo fits fine, although you won't be able to use a back shell on the connector - again, because of the thin wing. Very straightforward installation.

There are some pictures on "Junior's" photo page: http://picasaweb.google.com/DrKarst/JUNIOR#5552969528925872162


Paul
 
Last edited:
RV-3 Roll Servo installation

Hi Paul,
Thanks for the prompt answer. I agree that the wing installation would be preferred, but I can't figure out a way to get it into the space afforded by the inspection panel on an already completed wing. Any other thoughts?

Thanks,

Bob
 
Hmmmm....I was worried about that, so we actually did a check with the wing skin clecoed on to make sure that we could remove and install it when the wing was closed out, and we were able to do it. If I recall correctly, we had to remove the bell crank. It is possible that the -3B wing has a different access panel than the -3 wing, or the Dynon servo is a different size. if you can't fit it there, I think you'll have to do the wing tip trick with a long push rod.

Paul
 
Retofit

When I installed a Trutrak in the wing of n283rv, I used trutrak's mounting kit for an RV-7. It fit perfectly except for the electrical plug. Had to remove the plastic shell, as Paul stated. It sure helped to be "a pencil-fingered" son of a gun.
I am not an autopilot sort of guy, but in an RV-3 it is REALLY practical.

Bill Newkirk,
Prather, CA
 
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