What's new
Van's Air Force

Don't miss anything! Register now for full access to the definitive RV support community.

My RV-8A has a heavy wing (Yes another one, But with Pictures!)

scott08

Active Member
So my RV 8A has a left heavy wing. I have read all of the posts about previous heavy wings, I just want to be sure I am taking the correct course of action.

The Facts:
  • Left wing is heavy, evens out after about 45-1 hour worth of flight or approximately 8 gallons.
  • The Aileron is deflected to offset the heavy wing by about 0.5" at the far edge during cruise. If I level the aileron to be even with the flap and the wing tip on both sides, it rolls pretty significantly. Ailerons are even on both sides if level with wing tip and flap. Meaning I don't have a high and a low one with relation to the flap or wingtip.
  • Ball is pretty centered in the cage, maybe a slight right hand bias, but not much.

The Plan:
  • Take Current Aileron brackets, both inboard and outboard and slot them appoximately 1/8".
  • Move brackets to the projected position to even out the aileron forces and hopefully remove some of the heavyness.
  • Measure the amount of bracket movement required to neutralize the heavy wing, and drill the blank brackets I purchased for finalization.

The questions I have are:
Do you move both the inner and outter bracket?
If I move the aileron with relation to the chord of the wing, will that stop the aileron deflection required to keep the heavy wing up? What is the best way to measure this?
Which aileron do I adjust? Heavy or light side?

Thanks,
Scott
23h5ahk.jpg

2h2qybo.jpg
 
Which wing... ??

Scott, I think your photos show the top surface of the right wing, with the right aileron deflected downward... doesn't this mean that the RIGHT wing is heavy and requires additional lift to level the wings? Did the images get reversed/mirrored?
- Roger
 
Scott, does the amount of aileron unbalance required to maintain level flight remain constant as airspeed changes?
- Roger
 
So my RV 8A has a left heavy wing. I have read all of the posts about previous heavy wings, I just want to be sure I am taking the correct course of action.


I had a similar problem with my -8 and religiously followed the Vans heavy wing instruction from their web site. Recommend you do the same before doing anything else. Took a number of flights, but it worked.

-John
 
Scott, don't suppose you could fly it from the passenger's seat... I fly a -7A...:D. A passenger is worth about 8 gallons of fuel, by my calculations.
 
I will check the trailing edges, I didn't see that before.

It's funny you pointed that out. The left wing is heavy, and the left aileron is deflected up, you are seeing that correctly. The right aileron is deflected down.

The builder did mention one of the wings was not mounted perfectly. Could this be a side effect of that?
 
Hey Scott, have you checked the trailing edges of all your surfaces for proper bend

Section 5.7 shows an easy way to both check it and correct it. That may help your situation before you have to slot the mounting points (which you still may need to do if everything else checks out).

Scott

I have a similar situation, my thoughts are, changes to trailing edge radius and vertical movement of hinge will only make the aileron fly in a different position.

In your case you need more lift on one wing while the aileron is neutral, adjustments described above will only allow the ailerons to fly in their current displaced positions without trim pressure.
 
That was my concern with the deflection as pointer out earlier. Any thoughts on how to correct the root cause?
 
More questions...

Scott, I think your photos show the top surface of the right wing, with the right aileron deflected downward... doesn't this mean that the RIGHT wing is heavy and requires additional lift to level the wings? Did the images get reversed/mirrored?
- Roger

Scott, How do you know that the left wing is heavy? Does the airplane bank to the left when you release the stick?

Does your weight/balance data show a CG offset to the left? Adding a supplemental mass to the inside of the right wingtip would help bring the CG back to centerline, if that is the root cause. If the cause is aerodynamic, the solutions are... varied.

When you talk about burning fuel to achieve balance, do you mean more fuel in the right tank or left?

Do you have an aileron trim? ...is it the spring bias type? Is there enough range in the aileron trim to counteract the heavy wing?

Does the stick rest neutrally in center when on the ground? Are the ailerons in trail (neutral) when the stick is vertical?

Does the amount of heavy wing correction force/trim required to keep wings level change with airspeed? This might indicate

Have you used an accurate level to check the angle of incidence of the wings relative to each other in several span-wise locations? This might show the built-in error that the builder alluded to.

Check the angle of incidence of the wingtips, too. They have a lot of surface area, and a really long moment arm, so can create a large rolling moment. (My wingtips were far from true as received, and required internal ribbing to regain/retain proper shape.) A deformed wingtip could cause an asymmetric lift problem.

So... the builder/seller knew that there was a heavy wing problem, but didn't or couldn't correct it...?? Maybe he has more clues that would help you understand the root cause of the problem.

The fact that your photos show the right aileron deflected downward and you claim a heavy left wing is puzzling... ?? Do you see this photographic evidence as contrary to the claim of a heavy left wing? Displacing the right aileron down by half an inch should make the plane roll to the left.

Is there anything significantly asymmetric about the plane?

Check the aileron trailing edges first...

Just trying to understand the true nature of the problem...

- Roger
 
aileron trailing edge radius

I recall reading an article by Barnaby Wainfan (my childhood hero) in Kitplanes magazine several years ago. I cannot find the article but found a reference to it on a Yahoo Bearhawk web posting.


https://groups.yahoo.com/neo/groups/Bearhawk/conversations/messages/14814

Quote>>

14814aileron trailing edge

collinc2002 <[email protected]>

Feb 1, 2003

There seems to be some confusion as to the purpose and nature of
altering trailing edges to trim an airplane. I don't consider myself
to be an expert or anything on the subject, but I did build a RV-6A
once upon a time and still have a copy of a newsletter from Van's
covering the subject. The article is quite lengthy but very
informative (August 92' edition)

Briefly Van notes the dramatic effect that the trailing edge radius
can have on aileron control loads and the undesirable effects (even
dangers) of excessive trailing edge radii. He notes that there is a
tendency among builders to "underbend" the trailing edges and end up
with a trailing edge which bulges out somewhat. This causes a lower
hinge moment which means lighter control forces. In some cases it
causes "aileron snatch", a tendency for the ailerons to seek a
neutral (hands off) position slightly to either side of center. This
condition is impossible to trim and makes the airplane touchy to fly
because the stick must be held in the center; a condition which is
easily upset by light turbulence and/or pilot inattention.
Fortunately the condition is easily accomplished by clamping blocks,
hand seamers, or even hand pressure.

A by-product of this technique can be used for lateral (aileron)
trim. Since altering the trailing edge radius alters stick force, it
follows that altering only one aileron could affect laterl trim. The
essential info is that lateral balance can be achieved by decreasing
the trailing edge radius of the aileron on the light wing.

Van refers to an article in Dec. 91 KITPLANES magazine by Barnaby
Wainfan on "Wingtip Trailing Edges". Information in this article
helps explain why this phenomenon works. The simplest explanation is
as follows. Air flowing over any surface of the aircraft tends to
remain attached to the surface. When the surface curves, the air will
tend to stick to that surface until the curvature is too sharp and
separation occurs. This is what happens on the trailing edge radii
of the ailerons. Because the air pressure on the bottom of the
aileron is greater than on the top, the bottom air tends to follow
the trailing edge curvature more than the top air does. What
results is an upward jet of air. This upward jet of air pulls (or
pushes?) the aileron down and lifts the wing. Thus ,if we reduce the
radius of an aileron trailing edge, we will decrease the jet action,
that the aileron will move upward, and the wing will come down
(become heavier).

Hope this helps...

Collin Campbell #370
Bolivar, MO

<< End Quote

Hope this helps...
- Roger
 
I would fly it without wheel pants before doing anything. You would not want to slot a bracket, or pinch an aileron only to find it is something else later.
 
ditto this

Scott

I have a similar situation, my thoughts are, changes to trailing edge radius and vertical movement of hinge will only make the aileron fly in a different position.

In your case you need more lift on one wing while the aileron is neutral, adjustments described above will only allow the ailerons to fly in their current displaced positions without trim pressure.

I agree with this statement.
 
Scott,
A few comments...
1. Aileron position in flight can not be judged for proper in trail position relative to the wing tips or flaps without first verifying that the wing tips and flaps are correct... control systems are often rigged wrong because someing incorrectly aligned is used to align everything else.

2. The information regarding which wing is heavy does not jive with the position of the one aileron in your photos (possible cause explained in item one).
3. A photo of each aileron while in level flight might be of some help.

Jumping to try remedy's that others have used, without actually troubleshooting the problem and determining the cause(s) will lead to a long and frustrating process.

I have resolved this type of problem on a lot of different RV's.

Considering that it appears you are having somewhat odd behavior,
what you need to do as start from the beginning and check through the entire system.
Verify that the ailerons are shaped correctly using the guide in section 5.
Recheck the wing incidence
Check the rigging of the ailerons relative to the wing, not to the wing tip or the flap. This would include checking the vertical position as well as the position angle of each aileron when in the neutral position.
 
Last edited:
Scott agree with RVBuilder2002 about starting at the beginning.

Regarding checking the aileron aligned to the wing if you take the wing tips off and use some string or a straight edge the tooling holes and the trailing edge of the aileron should all line up as here ....
FP20012014A0000P.jpg

Regarding wing incidence a digital level guage on the same aft rib each side will show up any difference - value is not really important, only the difference with your issue.
 
So another question. If the wing incidence is off, how does one correct it?

It all depends on how severe it is.
It is rather unlikely that is the cause so my recommendation is that you not loose any sleep over it at this point.... but it is a possible cause, so it needs to be ruled out during the investigation process.
Regardless of what some people believe, the ailerons can have a huge influence. They contribute a large percentage of the wing area. If they are mis-shaped, mis-positioned, or mis-rigged (or a combination of all three) they can have a strong influence in ways you would never suspect.

My recommendation

- Check wing incidence
- Check aileron shape as described in Chapter 5.7 of the the latest Rev. of Section 5 HERE, and make any adjustments to them as needed (if you want the airplane to fly/handle as designed, you should do the same checks on the elevators and rudder also).
- Check the rigging of the ailerons relative the cord line of the wing airfoil (ignore the alignment relative to the wing tip and flap), and adjust as necessary.
- Check and if necessary, adjust flaps to align with neutral ailerons.
- Reposition wing tips to align with neutral ailerons, (if they are off enough to bother you... wing tip alignment has a low level of influence on roll trim).
Once all of these things have been checked/corrected and you still have a roll trim problem, then you should investigate vertical position of the ailerons.
 
Back
Top