"Twitchy" ailerons on my RV-7

dougweil · #1 07-23-2014, 01:06 PM

My RV-7 has now been flying for just over two years. The Hobbs meter has clicked past 300 essentially trouble free hours. My wife and I have flown it from Maine to California and it has proven to be everything we wanted in a fast and efficient cross-country machine.

But.. since its first flight it has had ?twitchy? ailerons. So what does that mean? Well I truly think it could rival an Extra 300 in roll rate. It handled too nice. The lateral control seemed really fast? way fast. It was uncomfortable to fly in turbulence and if I hand flew it under IMC, I was ?this close? to declaring an emergency. My old RV-4 never flew like this. It was smooth and responsive but not overly so. I?ve got almost 2000 hours in RVs; made 12 initial test flights in all models and never did I find one that handled quite like my -7. Frankly I flew it on autopilot 95% of the time so I wouldn?t have to hand fly this hyper-active RV with a bad case of ADHD.

A few weeks ago I was flying another RV-7 and marveled at how it flew. Nice smooth ailerons, no snapback like I had in mine. That was enough. Time to look into this deeper. My -7 is a quick build and the ailerons came all finished and ready to install. I just assumed that they were built correctly. Hmm? maybe not. I really got to looking carefully at how the trailing edge was formed and discovered that they had the dreaded ?round? shape that Van warned about years and years ago when rolling your own ailerons. I closely looked at my hangar partner?s RV-7A and saw a nice ?sharp? trailing edge (his was a quickbuild also). A call to Van?s confirmed that not all quick-build ailerons are created equal. They suggested trying the ?squeeze-the-trailing-edge? technique to see if I could get back that nice RV feel.

So today I spent about an hour laying out two oak 1x3?s and a half dozen clamps and squeezing down the trailing edge on both ailerons (careful not to mar by multi-thousand dollar paint job). Mission accomplished, I headed out for a test flight. WOW?. I couldn?t believe this? a totally new airplane!!! Smooth ailerons... certainly not a competition acro machine anymore but no snap-back, no ultra-lightness, and no twitchiness. It handled WAY better in turbulence and even the autopilot now was 100% better in making turns, intercepting a course to a waypoint and tracking an LNAV path.

Moral of the story folks? check your trailing edges on even those pristine quickbuild ailerons. Lay a straight edge along the top and bottom and be sure they are flat right up about a quarter inch from the trailing edge (mine started curving about an inch from the TE). And remember to make the squeeze the same to both ailerons (if your effort results in a heavy wing, squeeze the radius a little more on the light side). Now that I have a ?new? RV-7, I might even be brave enough to try a little hand flown IFR!!

Here's the "before" photo. Note the rounded trailing edge compared to the ruler.

Here's the "after" shot. The aileron is flat (in my case a little concave) right up to the trailing edge.

rightrudder · #2 07-23-2014, 03:25 PM

I'm glad you achieved such a transformational result. I will check my QB ailerons tonight, although I can't remember offhand if they're AEX wedge (like the 9's empennage TEs) or folded.

John Courte · #3 07-23-2014, 03:40 PM

I have this exact same issue, although I didn't know what to expect from the roll rate, other than my transition training in Mike Seager's -7. It seemed a little more jittery than Mike's 7, but I assumed that was because there was no Mike in the pax seat during my flight testing.

for me, the problem manifested itself in a divergent oscillation in the roll axis. A mild, imperceptible squeeze along the trailing edge reduced this issue to almost nothing, but it still twitches, and the autopilot has trouble keeping it under control. It could stand another round of squeeze, I think.

dougweil · #4 07-23-2014, 04:04 PM

Yes, John... Try a little more squeezing and you likely will solve your issue.

MarkW · #5 07-23-2014, 04:06 PM

Doug,
Your nine will not have this problem. It is built with the AEX trailing edge as you mention.

rvbuilder2002 · #6 07-23-2014, 04:33 PM

I would suggest that instead of squeezing the trailing edges trial and error style in an attempt to correct a handling problem, that you measure and adjust them to the specific shape they are supposed to be.

Section 5.7 in THIS document on the Van's web site gives details on how to do it.

RVG8tor · #7 07-23-2014, 04:58 PM

I just addressed the same issue. I always knew my aileron stick force was very light. I did some flights In RV7s and a friends 8 and they did not have the issue.

It was really nice having it be so responsive, but flying instruments was a chore, even the autopilot would get into a roll oscillation if I had the sensitivity too high.

I finally decided to do something about it when on my first flight with the Blackjack Formation group, the guy riding with me commented on my twitchy wings. I gave him the plane and he understood my issue.

There was an A&P on the field who was also a builder, he gently squeezed the trailing edges of my ailerons and I took it out for a test flight. He nailed it, less twitchy in roll and still balanced. It was like turning off super sensitive power steering.

The plane now handles much better on approach and in formation.

Cheers

GLPalinkas · #8 07-24-2014, 05:52 AM

Quote:

Originally Posted by rvbuilder2002

I would suggest that instead of squeezing the trailing edges trial and error style in an attempt to correct a handling problem, that you measure and adjust them to the specific shape they are supposed to be.

Section 5.7 in THIS document on the Van's web site gives details on how to do it.

Yep, just wish I had this info prior to finishing and painting my -6. The old manual was a little vague

As it is, I was able to get my ailerons back to a correct shape but cracked a little paint doing it

LettersFromFlyoverCountry · #9 07-24-2014, 06:13 AM

I'm having a devil of a time seeing the difference in the pictures. Truth be told, I had a hard time seeing the difference in the instructions too.

You'll just have to come over and fly my 7.

Mel · #10 07-24-2014, 06:27 AM

Quote:

Originally Posted by LettersFromFlyoverCountry

I'm having a devil of a time seeing the difference in the pictures. Truth be told, I had a hard time seeing the difference in the instructions too.
You'll just have to come over and fly my 7.

Look closely. In picture #1 from the 4" mark aft the scale does not touch the surface. Aileron surface is convex.
In picture #2, the 4" mark has a gap between the surface and the scale and the aft end of the scale is sitting on the aileron surface. Surface is concave.