hydroguy2

hydroguy2

Well Known Member
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/community/showthread.php?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?
 
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.
 
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.
 
hydroguy2 said:
(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/community/showthread.php?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?
Click to expand...

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 :p
 
DakotaHawk said:
Was your test pilot an RV pilot? This ain't your grandpa's ole caddy!;)
Click to expand...

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.
 
flyeyes said:
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 :p
Click to expand...

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.
 
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.
 
Sounds Like the Best Source is Your Test Pilot

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
 
Hmmm

There is always the possibility that something has come loose, or was not fixed right in the first place. I built a Kitfox and three of us missed that there was no clevis pin installed in the aileron circuit. It could have proved fatal.

I would make a list of all the rose joints then check them off individually when rechecked. Perhaps have another experienced guy fly it if you don't believe your original test pilot or are still .

In my RV9 several times we started to get roll instability, and several times I found that the flap pushrod bolts were undone. I am convinced someone was tampering with the aeroplane so I left the covers off.......... and rechecked before every flight. They never came undone but when we refitted the covers we got the same problem and took the covers off and found a loose bolt again?? The covers stayed off.

Now I am not suggesting anyone is tampering with your aeroplane just making the point that a loose bolt can cause these problems.
 
Brian,
My QB ailerons started out way too sensitive near center and I flew the first flights with my arm locked to my thigh. Anything which shook my arm caused a wing wag, and I suspect I could have duplicated what you describe. I was a bit mystified as that didn't match previous RV-8A experience.

Didn't know about the bulge thing. Early on I started squeezing to correct a heavy wing. Overdid it on the first one, squeezed the other one and bingo, the over-sensitivity started going away. Worked both trailing edges and now it flies like it should, quick and light, but not twitchy.
 
Thanks everybody. I've been in contact with test pilot and another multi/high time RV friend. I've got some things to look at and do, then I'll report back.

DanH, that was how I felt on my first few flights. I think I was mostly nervous about the whole experience and speeds I've never flown at. Finally getting used to the speed, my brain is catching up to the plane. Yesterday was the first time I've run it down low in fast cruise. The cold winter air is a real treat, 1000'agl doing 189kts(25",2500rpm). I wasn't doing any testing at this speed other than testing my grin.
 
aileron trim?

Brian,
Do you have an electric aileron trim servo with the springs? In my 7 I had to adjust the spring tension to prevent the stick from snapping back to center too aggressively if I slap the stick and let it go... This could cause what you are describing.
f.w.i.w.
 
Ben, I have the manual trim, which uses the same spring bias setup. It does spring back to center. Never thought about the tension, as I figured it would balance each other.

one more item to check, thanks
 
If you recall I had a very twitchy and unstable aileron roll tendency at high speed. Weather has been unfriendly for much high speed runs so It's been on hold. Well I should have taken Paul's and Dan's que and messed with the aileron shape. Here's what transpired lately:

3/14
Finally got to work on the sensitivity issue. I emailed Vans and got a response "huh, never heard of that problem". My friend and test pilot said he noticed it a little but at the time I had a heavy left wing, so didn't it didn't really develop. Tuesday, I called Vans and spoke with a tech rep. He said squeeze the aileron trailing edge, but not enough to see a change. Just lightly use some seamer pliers. GO EASY. Well, I did that yesterday and flew today.

WOOHOO!!!! problem seems solved. She is still very responsive, but tapping the stick was no problem. she rocked 1 or 2 times and then rock solid....perfect.

I am able to fly faster than before due to the increased stable feeling. I was level at 186kts, but hard to snap at pic that is readable with my phone. (ignore the fuel flow, it failed last flight, now shows 3-5gph at idle).
Flying213.jpg


Went to 9S5, to visit the FBO that is helping me host the SARL race.
Flying209.jpg


Life is good. 16hrs to go and then it will be even better.
 
Ironflight said:
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.
Click to expand...

I've seen a few posts about this (convex ailerons causing 'twitchiness' in roll). My -6 has the opposite -- portions of the ailerons are quite concave in the last 2-3 inches before the trailing edge. It's a visible indented curve on both the top and the bottom of the aileron, like someone 'squeezed' the trailing 3 inches or so, rather than just the edge. Thinking about trying a pair of suction cups to straighten them; I've tried using one cup on the top of the aileron, but there's really nothing to pull against.

Any guesses on how this would manifest itself in terms of handling, etc? My -6 is the only RV I've really flown, so I don't have any frame of reference, but nothing seems amiss.

-jon
 
mosquito said:
I've seen a few posts about this (convex ailerons causing 'twitchiness' in roll). My -6 has the opposite -- portions of the ailerons are quite concave in the last 2-3 inches before the trailing edge. It's a visible indented curve on both the top and the bottom of the aileron, like someone 'squeezed' the trailing 3 inches or so, rather than just the edge. Thinking about trying a pair of suction cups to straighten them; I've tried using one cup on the top of the aileron, but there's really nothing to pull against.

Any guesses on how this would manifest itself in terms of handling, etc? My -6 is the only RV I've really flown, so I don't have any frame of reference, but nothing seems amiss.

-jon
Click to expand...

Interesting report Jon - I have wondered what happens with convexity, and it seems you are seeing no ill effects. Perhaps once it gets "flat", there is no further change if you go beyond that. At least you seem to have one data point. Sorry - I don't know of a way to get it straight from where you're at except building a set of ailerons (which isn't that hard....).

Paul
 
A friend of mine in his RV7A had this exact issue and got it resolved by squeezing the trailing edge of the aileron. But like Paul said, you need to make sure the top and bottom are flat and only if the trailing edge has a bit of curve to it. Squeezing the trailing edge will make the aileron a bit more mellow (not as snappy) also.
 
Construction Manual

Ironflight said:
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.
Click to expand...

Paul hit the nail on the head here. This information can be found in Section 5G of the Construction Manual, FIG 5-5 for the bending tool, and FIG 5-7 for the control surface shape. Note: Applies to ALL Control Surfaces with folded trailing edges. Link below off of Van's Construction FAQ for reference:

http://www.vansaircraft.com/pdf/Section_5_R10.pdf

Many Quick Builders assume that the ailerons and QB assemblies are ready to fly right out of the box. They are NOT. :eek: The same checks and verifications that are done of the Standard Build Kits should also be performed on the QB Kits. Remember, the builder is considered the aircraft manufacturer in the eyes of the FAA under EAB rules.
 
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