Still Ailerons at High Airpseeds RV-7

Heavy aileron forces on RV7 at high airspeeds

I have a RV7 that now has about 23 hours on a new airframe and engine (O-360 with controllable propeller). The aircraft flies great except for one item:

When descending at airspeeds above 150 kts. indicated, the ailerons stiffen up. They are still movable but not without at least 10 pounds of force on the stick. They seem to lock up in the neutral position. Once enough ?breakout force? is applied the plane will bank left or right but the controls are still stiff. After the airspeed slows, the anomaly gradually goes away. Once back to airspeeds of 130 kts. and less, the aileron forces seem ?normal?.

Can anyone shed light on what it is I am experiencing? Many thanks in advance!
Jay Carpenter / Georgetown, Texas

If the ailerons are not flat front to back along the length of them, it can cause this.

If they bow out, the stick wil be very light and twitchy, if they are bowed in, stiff and solid feeling....

Perfectly flat is the goal for best feel.

Forces

Probably the shape of the aileron near the trailing edge. Outward bulge near trailing edge lightens forces, inward bend makes forces heavier. This is generic theory, works on most ailerons. Look up the Barnaby Wainfan articles in Kitplanes from several years ago. He goes into great detail about trailing edge profile and much more. Put a straightedge chord wise on your ailerons and see what you have.
Apples to oranges: Pitts aircraft have 1" wide trailing edge strips, ailerons are fabric covered. Bulging trailing edges remove ALL centering force in the ailerons. Let go of the stick and it will slowly go to the stop. Squeeze the trailing edges to eliminate the bulge and aileron forces become normal.

Had the same issue with my -4. We reshaped the trailing edge just slightly and it made a tremendous improvement. At first we thought something was binding up. The shape of the aileron has some crazy aerodynamic affects at higher speeds.

Stiff Ailerons

Hi Arlie,

How did you "reshape" your ailerons?

Jay

It's those naughty air molecules impinging on your surfaces....

Well Jay, I kind of went the unconventional route. I took a piece of 1/8" steel rod and ran it through the trailing edge. I then took two 2x4's, one on top one on the bottom and squeezed the trailing edge using some C-Clamp vice grips. You can build a similar setup mounted on your work bench but I didn't want to remove the ailerons. I did it on the plane. So the radius on my trailing edge is the same as the 1/8" rod plus it tightened up the skins in the process.

Vice grip hand seamer

I found using a vice grip hand seamer the easiest way to accurately tweak the trailing edges during construction.
http://www.cleavelandtool.com/HAND-SEAMER-3-1_2-JAWS/productinfo/575/#.V7Erlph96hc
You just move along slowly along the trailing backwards and forth, adjusting the dial a little each time, using a ruler to ensure you haven't bowed the trailing edge too far. Use a ruler parallel with the ribs as you move along to check that you are not over squeezing. Cover the squeezer plates with duct tape so that they don't mark your paint.There are a number of posts on the forums that talk about how to adjust trailing edges.
Cheers,
Tom.

Brantel said:

If the ailerons are not flat front to back along the length of them, it can cause this.

If they bow out, the stick wil be very light and twitchy, if they are bowed in, stiff and solid feeling....

Perfectly flat is the goal for best feel.

Click to expand...

This works on the elevators too. I flattened them a bit (were bowed out a bit) and it made a noticeable difference in pitch sensitivity. Also, I was pinching my aileron trailing edges to deal with a heavy wing and I could feel them getting stiffer, so I banged them back and went to trim tab. A little goes a long way when dealing with the trailing edge.

Larry

Chapter 5.7 of Section 5 of the construction manual is a good resource for checking and adjusting the shape of control surface bent trailing edges.
This applies to the elevators and rudder as well