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A left wing heavy RV-6A

Earl Findlay

Active Member
I was able to fly in an RV-6A this morning. What a ride!

One thing that I noticed is that the airplane was very left wing heavy. In other words, it would not fly straight and level hands off. I noticed that the left aileron on this airplane was slightly higher than the right, which would seem to be the cause of the left wing heavy appearance, but I am not certain.

My question, as a soon to be builder .. if this happens on my build, is it something that can be fixed without huge amounts of trouble? Or, is it an "oh $@*@ moment, and you're forever stuck with an airplane that does not fly straight, or face the prospect of rebuilding a portion of the airplane? I suppose that this means at some point, the builder neglected to check something??
 
This exact thing happened to me - left wing heavy on my -10. Sighting down the top of the wing I could see the left aileron was slightly higher than the right one, on the outboard end. Maybe 1/32 - 1/16?. Removed the aileron, removed the mounting bracket. Used a file to elongate the hole about 1/32? vertically. Partially filled the hole with JB Weld, re-drilled, filed sides flat. Remounted everything, heavy left wing is now gone. If you need more than a bit of elongation, Vans sells undrilled brackets for just this purpose.
 
What Bob Turner is describing is balancing the height of the aileron skin at the hingeline gap with the wing skin. If you lay a straight edge on the wing skin, overhanging enough to go back over the aileron, with the aileron fixed in the true neutral position (lined up tooling holes in tip rib as per the instruction manual), then look at the gap or contact between the straight edge and the aileron skin.

You would like them to touch, or for the aileron to be slightly high, so that the straight edge is lifted up off the wing skin slightly. Something less than a 1/32" or so. You would prefer not to have the aileron skin low. BUT the key is that this arrangement should be the same left and right, and the same at the inboard and outboard ends of the aileron.

It is a safe bet that the aileron on the side that is "light" (meaning it rises if hands off) is set below the wing skin by more than the other side.
The aerodynamic mechanism at work here is something I have explained in other threads. But all you need to do to fix it is as Bob Turner suggests, adjust the hinge bracket up or down as needed, most desirably by making new brackets.
 
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Yes, a heavy wing can be corrected.

Apparently, it is not hard to build a heavy wing. I had one, my 10 friend had one. Yes, a heavy wing is fixable. Undrilled hinges are available for the 7, not sure if the 6 is the same, and none are available for the 10. They can be welded and holes moved.

SCSMITH is the man!
 
I have a heavy right wing at the moment. I am about 12hrs into my phase 1. For now I added a trim tab to the bottom of the light aileron, once I install the wheel pants and gear leg fairings, I am going to adjust the hinge brackets. I will slot them for testing and then replace once I have determined the correct position. The ailerons are in trail when I hold the wings level, so I am confident the vertical adjustment will solve the problem.
 
I wanted to follow up on this thread. I had a heavy right wing. After careful measurement, I decided to shift the right (heavy) aileron down 1/8". I test flew it today and my heavy wing is 90% gone. I need to make a few other minor tweaks, but it looks like this was the right way to go!
 
Wing heavy 6A

I've lived with a left wing heavy 6A for too long. Finally tried rotating the nose gear leg fairing trailing edge a few degrees away from the heavy wing and flew today. Problem solved. John
 
Heavy wing- RV14-A

John,
How far out (left or right) was the ball? Did you add a trim tab or adjustment to the flaps or aileron? Was it just a simple rotation of the nose gear leg fairing?

I am in the process of making some adjustment on my RV 14-A so I can remove the taped-on trim-tab under my left aileron and right side of my rudder.
The Van's "Heavy Wing fix" memo was not written for the RV14-A. Any expert recommendations would be appreciated.
 
Trailing edge radius

Why is noone talking about squeezing the trailing edge of the aileron, per Vans plans, to alleviate this condition?
 
Good questions

I just looked at recent photos of my EFIS in flight before and after adjustment to my nose gear leg fairing. In both cases I was in straight and level cruise on autopilot. I have a trim tab on the rudder. With the fairing straight the ball was about 1/4 over the right line. After adjusting the fairing the ball in the picture appeared to be about 1/3 over the right line.

I've never tried reducing the trailing edge radius on my light side aileron. Have been more focused on panel upgrades, etc. I don't mean to contradict Van's recommendations. My aileron trailing edge radiuses look equal to me though and the alinements with the wing skins looks good. In flight the ailerons line up with the wing tips in straight and level.

I should add that I have an Antisplat mod on my nose gear leg and that I necessarily rotated it slightly to allow the fairing to be rotated. And, the idea of using the nose gear leg fairing as a trim adjuster is not mine. I read it on an old thread on this web site. I'm no expert. Just tried an idea I picked up here and it helped. John
 
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It would be helpful to communicate some definition of "heavy wing", along with other variables such as pilot weight, single pilot vs two, fuel loading, aileron trim condition and position. Some indication of roll rate is needed, also. I have the spring type of aileron trim, and there are conditions and speeds where it is fully to the right. When the aircraft is balanced left/right, no trim is needed.
 
I've never tried reducing the trailing edge radius on my light side aileron. Have been more focused on panel upgrades, etc. I don't mean to contradict Van's recommendations. My aileron trailing edge radiuses look equal to me though and the alinements with the wing skins looks good. In flight the ailerons line up with the wing tips in straight and level.

"Trailing edge radius on the ailerons look equal" Was this evaluated with the process detailed in Sub-section 5.7 (Folded Trailing Edges) of Section 5 of the construction manual or just eye? By eye for most people without the experience of what to look for wont tell you much.

You can access a digital copy of Section 5 HERE

The "Correcting a heavy wing" document does direct people to use the squeezing technique as a last step, but that is in the context of an airplane that has ailerons that were built/finished properly. A lot of them weren't.
There are other negative impacts to ailerons not being shaped properly.
- A possible slight dead band near the neutral point
- Excessively light control feel
- A lower level of control effectiveness
- In severe cases, aileron snatch

For that reason, I always tell people to start with confirming that the ailerons are shaped properly, and if they aren't, correct that first. Doing so, can correct a number of other issues (listed above) as well. A problem that typically exists is that people don't know what they don't know (They often times are flying the very first airplane they ever owned and they don't naturally know exactly how it is supposed to feel and handle).

If after checking, the aileron shape is confirmed to be correct, then go through all of the other possible causes before coming back to tweaking aileron shape.
 
Why is noone talking about squeezing the trailing edge of the aileron, per Vans plans, to alleviate this condition?
+1 ding ding ding winner winner chicken dinner.

If you have fat radius on the training edge edge of aileron, it can create weird control issues and heavy wing or rolling. Before squeezing the trailing edge, measure the trailing edge radius of your ailerons and that the skin is FLAT..... Make a template. Are they within in the drawing spec??? Is the skin straight before the trailing edge radius. People will not form (squeeze) the trailing edge fully and pull the skin down to the spar, creating a curve before the trailing edge. IF you have this issue FIX IT FIRST. If everything is good, then exhaust all other avenues....

WARNING: DON"T OVER DO SQUEEZE. DO A LITTLE AT A TIME. GO FLY and REPEAT. Also be careful how you squeeze it. You don't want the vertical free flange of stiffeners hitting the skin and putting an outward dent.

As other said check everything. There are many things that can cause roll.... gear leg fairings to mis-rigging of elevator (yes I have seen RV's where the elevators were uneven). Ailerons are of course the most powerful roll control. Are the flaps rigged? Sometimes the wing tip will be off slightly, and with neutral ailerons even with the wing tip trailing edge, the ailerons are off (you can see it at the flap end). I have seen that as well.
 
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It would be helpful to communicate some definition of "heavy wing", along with other variables such as pilot weight, single pilot vs two, fuel loading, aileron trim condition and position. Some indication of roll rate is needed, also. I have the spring type of aileron trim, and there are conditions and speeds where it is fully to the right. When the aircraft is balanced left/right, no trim is needed.

I found that measuring fuel delta was useful in providing a dimension. Fill both tanks full, and fly on heavy side until it flies balanced and record fuel delta Then vary speeds, climb and descend to expand the feel and understanding. This method was used to quantify my progress toward balance.
 
Template is not needed. Just use a straight edge and the process that is described in Section 5 of the construction manual.
 
Aileron trailing edge radius.

Went by the airport today with some calipers. Looks like the diameter of the radiuses of the trailing edges of both ailerons on my 6A is 7/32". The skins on the ailerons are flat. I plan to make a 2+ hour cross country Monday. Will see how it flys with the leg fairing adjustment at different speeds and as fuel burns. John
 
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Flew 2.5 hours today with a passenger in the right seat. No longer have heavy left wing after adjusting. the nosegear leg fairing. The ball stays 1/3 over the right line at 125 knots. Ailerons line up with wingtips. I switch tanks every 6 gals. Fuel volume didn't seem to make much difference. I think l need to tweak the rudder trim and the gear leg fairing to get the ball closer to center, but it's much better now without the heavy left wing. John
 
Note that when flying a side-by-side solo, the left side of the airplane *is* heavy. Burn from that tank first, then switch to the right side. On a 2.5 hour flight, you'll find both sides of the plane are "heavy" at times due to fuel burn alone.
 
I just went through this as well with my 6A...heavy right wing in my case.

Verified rigging etc, then went about squeezing the trailing edge of the light wing aileron as per Vans instructions. I was really surprised how little squeezing force was required to complete the procedure. Took 2 attempts and test flights to lighten the wing, then 1 to correct over squeezing, but now it flies much straighter.

The whole process was intimidating to me (non-builder), but I did it with an experienced builder and it went very smooth!
 
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