RV9A Pitch servo Install

[Harry]

In the May issue of Kitplanes there is a story showing a Skyview A/P install where the builder installs the pitch servo with the arm pointing down due to interference issues. I am having the same issues and wondering if this is an acceptable way to correct the problem?

 

[dynonsupport]

I'm not exactly clear what they mean when they say they turned it 180 degrees, but, if you end up with something that looks like the picture that accompanies the article (page 20, lower right) - that's what you're after.

 

[Harry]

They are referring to the servo itself mounted in the normal position, but the arm rotated to the bottom side of the servo (approx 160 degrees). This fixes any clearance issues with the elevator pushrod and only changes the geometry slightly. I am looking at the online version of the article, so I can't see page numbers, but there is a picture showing the servo arm in this position. Please take a look and let me know what you think.

http://www.kitplanes.com/magazine/avionics_electronics/SkyView_to_the_Rescue_9546-1.phtml

 

[dynonsupport]

So actually I was staring at the wrong photo (the roll servo install). We can't say we've heard of RV-9 owners having this issue, so we're following up with Kitplanes to get some more information.

But, generically, if that modified position can accommodate the full range of motion of the control surface without getting close to going over center, then it is OK. You ideally want perpendicular geometry there on both ends when the control surface is in its neutral position, but this isn't always possible.

 

[RV9APlane]

I just installed both servos on my RV-9A according to Dynon instructions and had no interference issues. However, I did mount the pitch servo bracket one rivet space distance too far back and rotated the servo itself 180 to position it closer to the bellcrank so that the pushrod tube was the proper distance.  This necessitated minor material removal of the vertical flange to allow clearance of the bolt head on the arm.  I am happy with the installation and can send you a picture if you wish.  

 

[RV9APlane]

Harry, sent you three pictures of my servo installs to your Gmail address.  Let me know if you get them ok or if you need additional views.

 

[Harry]

Hi Bruce,
I got the pictures. Thanks!

Harry

 

[rfinch]

FYI, I had the same interference problem the OP and the Kitplane builder had. Perhaps it's because I didn't remove the bottom flange and didn't rivet it to the fuselage bottom skin so there is a bit of a gap there.

So I can put the servo arm upside as the Kitplane builder did...or, if I remove the plastic from the top of the servo arm, cutting about half the top hole away, it should clear the elevator push/pull tube. Then I would have to mount the control arm in hole B. Which is preferred: upside down arm, or using hole B (middle hole). Mine is also an RV-9A.

 

[jakej]

FYI, I had the same interference problem the OP and the Kitplane builder had. Perhaps it's because I didn't remove the bottom flange and didn't rivet it to the fuselage bottom skin so there is a bit of a gap there.

So I can put the servo arm upside as the Kitplane builder did...or, if I remove the plastic from the top of the servo arm, cutting about half the top hole away, it should clear the elevator push/pull tube. Then I would have to mount the control arm in hole B. Which is preferred: upside down arm, or using hole B (middle hole). Mine is also an RV-9A.

The arm position doesn't matter, up to you. With the 9A ( A lighter pitch force aircraft) I'd use the outermost hole, this will allow the a/p to cope better with the responsiveness/lightness of the 9A. You get more torque using the inner holes but that isn't needed here.

Jake J