sensitive aileron, unstable roll

hydroguy2 · #1 12-23-2010, 07:29 PM

Getting more comfortable with my plane and the engine break-in is going well. So I'm starting to expand the testing envelope. I'm still zipping around at 175kts, so expect the aileron to be a little sensitive. But when I give bump left or right and release pressure, she seems to want to oscillate more and more. I stop this cycle after 3-4 times.

Search showed the this thread:
http://www.vansairforce.com/communit...t=34298&page=2

so I'll be looking at the trailing edge of my QB ailerons next trip to the hangar.

Any other thoughts?

Sid Lambert · #2 12-23-2010, 08:45 PM

Unless your trailing edge radius is just way too big I'd be looking elsewhere. At 175kts an RV should be rock solid in roll. Check all the rigging again. Look for slack in the ailerons or even play in the flaps. It's a -7 so I assume the hinges are not too low like some of the older RVs.

Mike S · #3 12-23-2010, 09:05 PM

Where is the CG??

hydroguy2 · #4 12-23-2010, 09:13 PM

CG was 80.2 empty. Should it matter in roll? Pitch is very stable.

I had a test pilot do the first flight. He said they were light but he said they were perfect for him and I would get used to it. I don't have any problem controlling the plane, just seemed like things oscillated too much.

flyeyes · #5 12-23-2010, 10:18 PM

Quote:

Originally Posted by hydroguy2

(snip) release pressure, she seems to want to oscillate more and more. I stop this cycle after 3-4 times.

Search showed the this thread:
http://www.vansairforce.com/communit...t=34298&page=2

so I'll be looking at the trailing edge of my QB ailerons next trip to the hangar.

Any other thoughts?

The airplane oscillates in roll with your hand off the stick? Mine absolutely does not do that.

I've read about rudder trailing edge radius problems causing an oscillation. Is it possible the rudder is oscillating and coupling in roll?

I also remember reading about an rv with roll instability that didn't hav the rear spar bolts installed. That might be worth a look

DakotaHawk · #6 12-23-2010, 10:25 PM

Quote:

Originally Posted by hydroguy2

I had a test pilot do the first flight.

Was your test pilot an RV pilot? This ain't your grandpa's ole caddy!

hydroguy2 · #7 12-23-2010, 10:38 PM

Quote:

Originally Posted by DakotaHawk

Was your test pilot an RV pilot? This ain't your grandpa's ole caddy!

Retired USAF fighter pilot who flew his whole career, CFI, 1000hrs in RV's and Rockets and done many first flight of various aircraft. He's very qualified and came highly recommended. I sent him a message also.

hydroguy2 · #8 12-23-2010, 10:47 PM

Quote:

Originally Posted by flyeyes

The airplane oscillates in roll with your hand off the stick? Mine absolutely does not do that.

I've read about rudder trailing edge radius problems causing an oscillation. Is it possible the rudder is oscillating and coupling in roll?

I also remember reading about an rv with roll instability that didn't hav the rear spar bolts installed. That might be worth a look

It doesn't do it by itself, I have to bump the stick to start the process and it starts rocking the wings. Not bad, but not what I thought it should do....maybe I should let it go further to see if it will stop on its own.

Rear spar bolts are in place. no play in any of the linkages, controls are positive, balanced and smooth. Like I said, Jim(testpilot) thought it flew perfect.

Ironflight · #9 12-23-2010, 11:43 PM

If you are checking your ailerons, remember that it is not just a matter of trailing edge radius - it is about straight top and bottom surfaces right until the "final" radius starts. If our ailerons have a "bulge" before the final radius (or the straight edge doesn't lay flat, because the top or bottom is convex), this can lead to very sensitive ailerons.

terrykohler · #10 12-24-2010, 05:25 AM

I'd probably rely on the test pilot's opinion more than anything else. If he's got the hours and range of experience you suggest (especially in multiple RVs) AND, he's flown your aircraft, you're likely getting great information. The responses you see here are more likely to offer wide variety, but be more limited to experiences in one or just a few RVs. These forums are a great help, (the rear spar check was an eye-opener), but the opinions offered sometimes need to be carefully weighed, especially before you start changing things. If you can, get a ride in a couple of similar RVs and try to replicate your "test".
Terry, CFI
RV-9A N323TP