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elevator misalignment repair

GyroRon

Active Member
I have asked for input on the facebook groups and got some info but many people keep referring me to come here to learn more so here I am...

My RV4's elevators are not in alignment. When the left side is even with the horizontal ( by even I mean the counter weight section ), the right side counter weight is higher than the horizontal by a good bit.

I tried using two different " angle finders " on the elevator today, measuring the angle of one side with it held flush with the horizontal, then holding the elevator there, measured the other side.... just to see if it is the counter balance weights might be out of whack or if the tail was actually out of alignment. Measured in multiple places on the tail, I found that one elevator is roughly 2-3 degrees higher ( or lower depending on which side is centered with the horizontal ) than the other.

What research I've done this appears to be a common problem, builder of the plane likely did not hold the drill level when drilling through the control horns.

I am trying to fix this now. Plane fly's decent, but does have a tendency to roll off to the left, I have to use full right aileron trim and burn off the left tank to keep the wing level hands off. And I have to hold a touch of right rudder always to keep the ball centered. I am hoping getting the elevators even will fix most of that.

Plan of action is to have the bolt hole in the right elevators control horn welded up, and using more care and some sort of jig between the two horns, re drill a new hole that is hopefully straight and true.

I am NOT a welder by any means but I do have a 110 volt mig wire welder. It is a cheap unit, but I have done plenty of welds on things over the years and can do a decent job. Not really sure I want to tackle this, as I really want a perfect job done, but short of trying to find someone to Tig or Gas weld it, this would be something I could do myself. I already removed the elevator and have it here at home where my welder is.

Looking for pros and cons to this method of fixing my issue and pros and cons to trying to weld up the hole myself or getting a pro to do it.

Thanks Ron
 
Ron,

Have the PRO’S do it.

Don’t cause more pain than you need.
There are instructions in Vans build manual how to rig.

Get a good Tech counselor to help or
Find RV builder to guide you.

Hope it helps.

Boomer
 
Unless the deviation bothers you cosmetically, leave it alone.

I've "corrected" several and could see no difference in the flight characteristics.
 
There is not enough leverage on the elevator to cause the heavy left wing that you describe. Concentrate more on your heavy wing problem.... Follow Van's instruction on this in the back of the build manual.

If you are going to weld up and re drill the hole, make a template of the existing hole and how much it needs to be moved, before it is welded. Take it to a shop and have it tig welded. That part should be 4130.
 
Regardless how careful you are it is very difficult to drill the holes straight on both elevator horns. I had a 4130 plate of the same thickness professionally welded on outside of the horn that would give the best edge distance. I then measured how far it was off and multiplied it by the ratio of the distance between the elevator horn pivot points and the elevator front to elevator hinge point to calculate how far the hole had to move. I had to shorten the spacer slightly on one side to accommodate the welded plate.
 
Your tendency to turn left is much more likely to be an aileron rigging issue than the elevator angle mismatch.

If I were to address this, I would get 1" square or circle of 4130 (same thickness as horn) and drill an appropriated sized hole in the center), then wallow out the hole in horn. Level up and secure elevators. Add a very small dab of slow set superglue to the plate and use the bolt through the fit up to pull the plate to the horn. Then bring elevator to welder and ask him to go in steps with TIG to avoid warpage. Will need to get all parts clean and free of paint and scale before the fit up though.

Welding the hole closed would work, but that weld material will be harder than the normalized stuff and difficult to start the hole without slippage. I often weld material on to parts and then machine it to specs. You would be surprised how much harder the weld material is than the base metal. The doubler plate approach will help to insure better alignment and eliminate the machining work necessary to get the welded area perfectly flat on both sides.
 
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Had this problem

When I purchased my RV7A it also had a significant difference between the left and right elevators. I observed this during the prebuy and on my pre purchase inspection flight but figured it could be corrected if it became a problem. Several people on this forum suggested I leave it alone, since in their opinion, it wasn’t a big issue. I subsequently discovered on my flight home it was a big issue and only got worse the faster I flew.

The builder tried to compensate for the mis-alignment problem by mis-rigging the ailerons and flaps. This aircraft with totally messed up flight controls tried to roll upside down at higher cruise speeds and did not like landing in a crosswind. That flight home became scary!

The A&P/IA I used at the time (he’s since passed away) called in a gentleman from Associated Aero at KPWA (they do a lot of sheet metal work) who removed the elevators, welded closed the old holes, and re-drilled new holes in perfect alignment. He then reinstalled the elevators, re-balanced them and together we re-rigged the ailerons and flaps. The airplane now flys great! Because I mostly fly alone (and need to lose a few pounds) I later added an outboard aileron trim wedge to give aileron trim a little more authority.

Don’t ignore it! Fix it and if possible get someone to assist you who has experience. There are reasons why flight control surfaces need to be correct with flight safety being paramount.
 
All very good inputs in the posts above. And yes, bring it to the pros, even for the welding closed of a hole…
The non-pre-punched -4 build takes a lot of attention to details in rigging to have a safe and straight flying bird. Assuming your correction of the elevators works, all good :)

If not, there are plenty of things to check, some of them already mentioned above, mainly:
- trailing edge radiuses
- vertical stab offset
- ailerons rigging
- flaps rigging
- landing gear wheel pants and fairings rigging
- wings AOA rigging
 
Welding

Your tendency to turn left is much more likely to be an aileron rigging issue than the elevator angle mismatch.

If I were to address this, I would get 1" square or circle of 4130 (same thickness as horn) and drill an appropriated sized hole in the center), then wallow out the hole in horn. Level up and secure elevators. Add a very small dab of slow set superglue to the plate and use the bolt through the fit up to pull the plate to the horn. Then bring elevator to welder and ask him to go in steps with TIG to avoid warpage. Will need to get all parts clean and free of paint and scale before the fit up though.

Welding the hole closed would work, but that weld material will be harder than the normalized stuff and difficult to start the hole without slippage. I often weld material on to parts and then machine it to specs. You would be surprised how much harder the weld material is than the base metal. The doubler plate approach will help to insure better alignment and eliminate the machining work necessary to get the welded area perfectly flat on both sides.
Hardening of 4130 is caused by improper welding technique, or in rare cases cold temperatures in welding area. TIG or Oxy/Acy I can make a demo weld that can be easily drilled or alternatively a weld that is difficult to drill.
 
When I purchased my RV7A it also had a significant difference between the left and right elevators. I observed this during the prebuy and on my pre purchase inspection flight but figured it could be corrected if it became a problem. Several people on this forum suggested I leave it alone, since in their opinion, it wasn’t a big issue. I subsequently discovered on my flight home it was a big issue and only got worse the faster I flew.

The builder tried to compensate for the mis-alignment problem by mis-rigging the ailerons and flaps. This aircraft with totally messed up flight controls tried to roll upside down at higher cruise speeds and did not like landing in a crosswind. That flight home became scary!

The A&P/IA I used at the time (he’s since passed away) called in a gentleman from Associated Aero at KPWA (they do a lot of sheet metal work) who removed the elevators, welded closed the old holes, and re-drilled new holes in perfect alignment. He then reinstalled the elevators, re-balanced them and together we re-rigged the ailerons and flaps. The airplane now flys great! Because I mostly fly alone (and need to lose a few pounds) I later added an outboard aileron trim wedge to give aileron trim a little more authority.

Don’t ignore it! Fix it and if possible get someone to assist you who has experience. There are reasons why flight control surfaces need to be correct with flight safety being paramount.

To prove a problem, fix only one thing and test it. It would have been nice to see if re-rigging the ailerons and flaps first, corrected your problem.
 
To prove a problem, fix only one thing and test it. It would have been nice to see if re-rigging the ailerons and flaps first, corrected your problem.

In fact the elevator re-installation and rebalancing did occur at the same time. Re-rigging the other flight controls did in fact take several flights to address but for brevity I failed to say that.:🤬
 
Thanks for the input guys.

I found a specialist who can tig weld up the hole.

Another pilot buddy of mine at my airport had to do the same thing with his tail on his RV6, and he came up with a nifty little jig and method to insure a straight drill through on the control horns.

Plan is to take the elevator tomorrow to get the hole welded up and then ill clean up both sides smooth with a grinder or flap disk and then have my buddy help ( he will probably do most of the work since he has done this already ) and we will reinstall the elevator and get the hole drilled right.

With some luck and good fortune, the plane will fly more or less straight and true afterwards.

If not then at least the tail is even....

I ironically was watching a video I took on my phone of a recent flight to the beach in the plane and I had turned the camera around to video the view to the rear and guess I had not noticed it before, but sure enough.... The left elevator was flush / level with the horizontal and the right side counter weight was a good 1/4-3/4 up on in comparison to the horizontal.

Seeing how we measured both elevators behind the hinge line ( and also on the counter weights ) and there was a 2-3 degree difference between the angle of both, I feel like there is good possibility that the tail is causing a slight twist as I fly and causing the plane to want to bank to the left.

It is not like the plane goes wildly out of control to the left, but to keep it wings level hands off, it takes all the right aileron trim I have, and even then if both tanks are full, it still ever so slightly falls off to that direction. If I burn off the left tank to near empty I have to trim the ailerons more neutral. Essentially it isn't bad, it just isn't ideal either.

The yaw issue is also not bad. I can put my right foot on the rudder pedal and give just a tiny bit of pressure and keep the ball centered. Take my feet off and the left side of the ball now is just outside the " centered " right side line. Essentially its one ball out. Again, might have nothing to do with the tail, but maybe it does...

All in all the plane flys great. Doesn't have any changes or difference in flight handling from any reasonable cruise speed ( say 140 to 170 mph ) nor does it get any different if I push it past 180. Can't really say much to slow flight as I only go below 100 to land and I am never really hands off during the landing approach.

Once I get the tail back on and finish the other work I am doing ( need to remove prop and give everything a inspection... also need to fool with my carb heat set up as I was in the process of removing it cause it seems to not do much, but now I think its better to have it on the plane even if it isn't doing much than to not have it at all )... I will test fly it and hope all is good and will report back. If the work to the tail doesn't produce much for results, I might leave it as is, or might try to see if I can find someone with more experience that can help me do the squeeze on the trailing edges thing you guys are talking about.

Oh and btw, the ailerons, in flight, the inside of them are dead nuts even with the flaps with the flaps full up. both are slightly lower than the wing tips though. They appear to be evenly low in relation to the wing tips. Almost as if the wing tips are just slightly angled high if that makes sense.
 
The yaw issue is also not bad. I can put my right foot on the rudder pedal and give just a tiny bit of pressure and keep the ball centered. Take my feet off and the left side of the ball now is just outside the " centered " right side line. Essentially its one ball out. Again, might have nothing to do with the tail, but maybe it does...

Others may disagree, but a full ball out is, IMO, a LOT.
 
There is not enough leverage on the elevator to cause the heavy left wing that you describe..

I was just having this same conversation with Van (Dick) over lunch today (for a different reason). That will definitely cause the aircraft to roll. Same as dissimilar flaps. Problem gets worst as speed increases.

The discussion was in regards to an RV that would roll faster to one side than the other. Turns out the elevator was out. One issue that i have seen (and several verified during the same conversation) is that people line up the control weldment for drilling vice the elevators.
 
Elevator counter-balance mis-alignment

I dealt with the same issue with my 4 with the counter-balance arms being aprox. 3/8” from flush. In my case it wasn’t the control horn indexing but a twist in one of my elevators.
 
Others may disagree, but a full ball out is, IMO, a LOT.


I am a very natural " Seat of the pants " kind of pilot. The yaw bugs the heck out of me. Feels way out of whack.

So maybe one ball out is actually bad. I don't know. I know I don't like it.

But it will fly along happily like that without any issue I can see. But it bugs me and there isn't much room for my feet and legs in the thing anyway so it is most comfortable for me to keep my feet on the pedals, so I just have to have the slightest bit of pressure on the pedal and it flys straight.

Considered a trim tab on the rudder, but want to try this elevator thing first.
 
Trim wedge

You will find a tab or wedge on almost every RV you see. I tried to anticipate vertical offset fin location to not have one on my RV-4 that I built, but I missed my mark. I had about a half ball out at cruise during phase 1 testing, so I made a wedge for the rudder that I installed with double sided tape to get the size dialed in. Eventually bonded on with Pro-seal. I hated to put it on, but the rest of rig geometry was in spec, so I live with it and hardly notice it now, and it doesn't protrude like a tab. Heavy wings can be a myriad of things from aileron trailing edge radius, aileron hinge height ,wing incidence and twist ,ect. The RV-4 as you know is hand built and there are plenty of ways to get things a hair from perfect. The "ball out" is usually vertical fin/rudder, or gear leg and wheel pants rigging. The vertical fin can be moved with a lot of work, but the intersection fairing will need to modified as well. Id recommend you try the trim wedge first.
 
Hardening of 4130 is caused by improper welding technique, or in rare cases cold temperatures in welding area. TIG or Oxy/Acy I can make a demo weld that can be easily drilled or alternatively a weld that is difficult to drill.

I wasn't referring to hardening of the base metal, which I agree can be minimized outside the HAZ. I was referring to the weld deposit metal itself, which is what the OP would be drilling through in this case. I have machined many welded components and have the dulled mill bits to how much harder the outside layer of a weld deposit is compared to the base metal or even the bulk of the deposit. The outside layer of the weld deposit cools fast enough to partially harden it and makes machining through that layer a real bear.
 
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Oh and btw, the ailerons, in flight, the inside of them are dead nuts even with the flaps with the flaps full up. both are slightly lower than the wing tips though. They appear to be evenly low in relation to the wing tips. Almost as if the wing tips are just slightly angled high if that makes sense.

And what leads you to believe that the flaps and wing tips are where they are where they are supposed to be? Unfortunately those can only be used as a reference if set perfectly in trail. I helped someone with a problem similar to yours. Builder set the left flap down over 1" from proper location to address the heavy wing, which turned out to be a mis-alinged aileron hinge.

I have my doubts that this journey will end with the mis-aligned elevators.
 
I was just having this same conversation with Van (Dick) over lunch today (for a different reason). That will definitely cause the aircraft to roll. Same as dissimilar flaps. Problem gets worst as speed increases.

The discussion was in regards to an RV that would roll faster to one side than the other. Turns out the elevator was out. One issue that i have seen (and several verified during the same conversation) is that people line up the control weldment for drilling vice the elevators.

I would defiantly go with Van's response on this issue.

Don't propeller powered aircraft roll faster opposite of prop rotation?
 
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