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A heavy wing conundrum

00Dan

Well Known Member
My RV-4 has a heavy wing. The problem is, I’m not sure which it is. In level flight, the ailerons deflect themselves slightly, with the right deflected up and the left down. If I release the stick, they maintain this position and the aircraft predictably enters a slow right roll. If I use my Mk I eyeball and align the trailing edges of both ailerons with the flaps, the plane enters a left roll, with a faster rate than the stick free right roll.

Is this a heavy right wing or a heavy left wing? I’m trying to narrow down where to look next.

For background, I have already verified that the flaps retract fully, and the trailing edges of the ailerons align with the flap TE with stick neutral on the ground. The right wing tip TE is slightly out of alignment with the aileron, but what I’ve seen on here has differing accounts on if this has any effect. The ailerons deflect in flight regardless of if gear fairings are installed, so I don’t think fairing alignment is the (primary) cause.
 

I have and am still working through step one. Step two is addressed by my existing rudder trim. That’s why I’m trying to determine which wing qualifies as the heavy wing, to try and narrow down my search for rigging items. Things like wing incidence and dihedral aren’t really feasible to change but I can certain look at everything else.
 
I have and am still working through step one. Step two is addressed by my existing rudder trim. That’s why I’m trying to determine which wing qualifies as the heavy wing, to try and narrow down my search for rigging items. Things like wing incidence and dihedral aren’t really feasible to change but I can certain look at everything else.

One way to measure your heavy right wing is to fly off the right tank until it is balanced then record/measure how many gallons it is. Do this before all the work to have a baseline.
 
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The problem is, I’m not sure which it is. In level flight, the ailerons deflect themselves slightly, with the right deflected up and the left down. If I release the stick, they maintain this position and the aircraft predictably enters a slow right roll..

You have a "Heavy right wing", by definition. Read thru the document in post #4.
 
Check Aileron Mount Rigging

Check that your ailerons are in trail to the wing. Can't tell you how many RV's I've seen where you put the aileron in neutral (aligned with wingtip and flap) and run your hand under the wing and find an aileron hanging low compared to the wing. Use a straightedge to confirm your observation.

Having one end of an aileron 1/4" lower (to the wing) than the other seems all too common.

But before you get out the tools... check the flap angles. Easy to rig one flap slightly different angle than the other. Fixing that may change your opinion on the aileron.

No point chasing other stuff until the rigging is correct.
 
Same problem but with flaps

Recently purchased RV-6.
Ball was out to right in cruise by 1 ball. Rudder wedge installed and now cruise flight is perfect. Can’t believe builder and 2 other owners didn’t fix this!
When I slow and extend flaps I get a left roll (I am certain it was there previous to rudder wedge). So my conclusion is a flap problem, with right making more lift than left. I need to fix this but don’t want to affect cruise flight with flaps up.
Flaps are electric btw.
Is this just a flap rigging problem. In other words one comes down more than the other? Also what am I looking for when I see “wing template” in Van’s “Heavy Wing” procedure?

Thanks
 
“wing template”

There is a page in the plans that have the drawing. It was also printed on the inside of the shipping crate, but that's long gone!! If you don't have the plans, Order a set from Van's.
 
Check that your ailerons are in trail to the wing. Can't tell you how many RV's I've seen where you put the aileron in neutral (aligned with wingtip and flap) and run your hand under the wing and find an aileron hanging low compared to the wing. Use a straightedge to confirm your observation.

Having one end of an aileron 1/4" lower (to the wing) than the other seems all too common.

But before you get out the tools... check the flap angles. Easy to rig one flap slightly different angle than the other. Fixing that may change your opinion on the aileron.

No point chasing other stuff until the rigging is correct.

How do youn check the flap angle rigging and how do you adjust it? I'm about to dig into my heavy right wing where my left flap retracts up higher and isnt flush with the belly skin like the right wing. So would be nice to start with flap angle if I knew how to measure and adjust (if required).
 
How do youn check the flap angle rigging and how do you adjust it? I'm about to dig into my heavy right wing where my left flap retracts up higher and isnt flush with the belly skin like the right wing. So would be nice to start with flap angle if I knew how to measure and adjust (if required).

Tool needed: A digital level. Something similar to https://www.amazon.com/Electronic-Inclinometer-Horizontal-Construction-Professional/dp/B07YFCXXT6/ref=sr_1_6?dchild=1&keywords=digital+level&qid=1633489706&sr=8-6

Now, a short one is nice to check the flaps, but a longer one will be really nice for our purposes. So this one linked above may be too short.

Step 1: is the airframe level left to right? Open the canopy and lay the level crosswise across the plane. If it isn't level (virtually assured) then find some plywood and raise the low main gear until you get it level (or darn close).

Step 2: check the wing angle of incidence. Get two blocks. Place one on the wing about 2' outboard at the main spar, place the other aft above the aft spar rivet line. Lay your level on the blocks. Note the angle. Go to the other wing and repeat. Should be VERY close. Specs are in the manual. If there's difference in the angle of incidence (beyond the allowable) you've found a significant issue. Stop here and resolve it.

Step 3: use your digital level to measure the flap angle with the flaps up. A shorter level would be handy here but you can use some blocks and do it with a bigger level. Chose a mid-point in the span of the flap. Note the angle measured. Repeat on the other side. Any difference? if the difference is the same as (an acceptable) wing angle of incidence difference you're OK. Say for example that the two wings are within 0.5 degrees, with the right one being more. Having the flap on the right similarly read 0.5 degrees more is totally fine.

If these steps indicate your flaps are set unequal when up (I'd say by more than 1 degree) then you need to adjust the flap links to fix.

At least that would be my approach.
 
incidence angle

Well looking in the 6 manual I can't find the wing incidence tolerance amount. I did find my note that I got mine within less than 0.1 degree of each other.

Also some of these digital levels don't like the dihederal cant (affects the angle measured). Check the measurements by reversing the level end to end. If you get different numbers I recommend you average the two numbers - and do that for every angle you measure.
 
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