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Wind Gust Damage

P

PaulR

Well Known Member
My 9A inadvertently was left outside, tied down, at KIOW the week of the 4th of July and suffered through a storm front that contained 75 mph gusts and lots of rain. I know it blew pretty hard because of the Citation that jumped its nose wheel chocks and rolled across the tarmac. The good news is it didn?t get wet inside. The bad news is, the gust locks all came off so I assume the ailerons, elevators and I know the rudder were flapping in the wind. I know the rudder was as there is now a dent about the size of a pencil eraser in one side where it contacted the trim tab.
Knowing that gusts like that could have caused more damage than was visible, I removed all the inspection covers and did a very thorough inspection the next day. Finding nothing else amiss, I flew it around the pattern a few laps and thought all was okay.
When I left the next day and got to cruise altitude I found, much to my dismay, I had to hold a little right rudder to keep the ball centered, which I have never had to do. Other than that, all was good.
So my question is, where do I start looking? Rudder looks fine and even if it twisted, wouldn?t it still be in trail and something else, i.e.: gear leg fairings, wheel fairing, etc., have to have moved to cause it to need right rudder? I have visually checked the GL fairings and wheel pants and they ?appear? to be fine. If the rudder was twisted, could it cause the need to add right rudder?
 
Could your eraser size dent actually be in the center of a larger depression of the skin?
 
az_gila said:
Could your eraser size dent actually be in the center of a larger depression of the skin?
Click to expand...

That's a good question Gil! To the naked eye no, but I don't think I've put a straight edge on it either. I'll do that this evening. Thanks
 
Rudder Damage

I had exactly the same thing happen to me. Small hole in the left hand side of the rudder, that wasn't noticed on inspection prior to take off. How I missed I'll never know.

On take off LOTS of right rudder needed to keep straight and level. On landing discovered the hole. There was no other noticeable damage, yet it just didn't feel right. Even covering the hole, thinking it was inducing drag didn't help much.

I did manage to fly the rest of the way home, but knew that the rudder may have a twist not visible to the eye. When I took it off and laid it on a bench, there was really no indication that it was bent or twisted. Did some research and was contacted by one of my local Tech Councillors from the SAAA (Sports Aircraft Association Australia), both indicated that while I could re-skin the current rudder, the best option was to replace it.

Long story short, that rudder now hangs on the wall in the hangar and I built a complete new rudder. As the rudder was one of the first things I ever built on this plane (RV7A) it probably wasn't as good as it could have been if I had the experience I had at the end of the build. The new one is MUCH better, it doesn't need the trim tab that was on the old one and the plane flies straighter than ever.

If you have damage to the rudder, experience shows in my case, it was best to replace the whole thing. The complete rudder kit wasn't too expensive (well the freight to Aus was half the cost!) it took me a week of evenings and a weekend to build, prime, paint and replace. The only part I kept was the lower fibreglass as it contained the strobe/light combination and wasn't damaged.

I have peace of mind that the rudder is how it should be now. With that one part rebuilt/replaced I did start to question how much better I could build the other parts... but haven't gone down that route. No wonder people build more than one of these planes!!
 
I'd check the bolts and torque on the front end of the vertical stabilizer. Wind hammers the aluminum and steel bolts through aluminum holes can do a number if the part gets some play. The front end of the vert should be offset 1/4" to the left of the fuselage center line. I'm wondering if slight movement to the right would cause you to need to hold right rudder. Also the rudder should clear the elevators in full deflection. I'm wondering what gave to cause the damage to your rudder.
 
Ben,
I have at least 1-1/2" clearance between rudder and elevators when fully deflected to the stop. I'd have to measure again to verify but there is plenty of clearance. I am utilizing the "internal" rudder stop that has been used a lot.

Tom,
I had a piece of 3/16" CRS bent in a "u" shape from the rudder horn to the rudder stop angle. It straightened that out.

I'm guessing that the rudder is twisted but the movement of the vertical stabilizer is a possibility I guess also. I will check closer this weekend.
 
Twisting of the VS rear spar is also a possibility, given that the internal rudder stop transfers all stop load as torque to the VS rear spar. This has been one criticism of the internal stop in the past.
 
Paul,

Please let us know what you find out. I live in an area that can get extremely windy. That information would be good to know.

Thanks!
 
krw5927 said:
Twisting of the VS rear spar is also a possibility, given that the internal rudder stop transfers all stop load as torque to the VS rear spar. This has been one criticism of the internal stop in the past.
Click to expand...

I knew it was but elected to do it since I didn't think it would ever be a problem. And it wouldn't have this time had they put it inside like I asked them to. I thought at $50 a night it was not only cheap insurance but also a little extra income for mostly nothing. They put it in the next two nights at no charge!!!

Hopefully I'll figure something out this weekend.

Gil had said that maybe the small dent was the center of a larger depression and that's possible I suppose. That depression causing enough low pressure on the left side of the rudder and pulling it and therefore needing a little pressure on the right pedal to counter act. Hoping it's as simple as building a new rudder.
 
Paul
Is it possible to check the torque on the rudder cables?
If they moved with the rudder in the wind mabye one created someslack? Im new at this so I may be way off. Good luck
 
dr_hickman said:
Paul
Is it possible to check the torque on the rudder cables?
If they moved with the rudder in the wind mabye one created someslack? Im new at this so I may be way off. Good luck
Click to expand...

The RV rudder cables aren't under tension, they are slack per design.
 
re wind damage

i'm wondering about the trim tab and left elevator?
is the left aileron is in perfect trail?
good luck
jeff H
N377CP, KWVI
 
So right now the plan is to at least check the aileron/flap rigging first and if there is anything out of line I'll investigate and fix that first then fly it again. I really think I need to eliminate that first. It doesn't appear that the gear leg fairings or wheel pants have moved.

Hopefully I'll get to that this weekend and see if the ailerons are contributing. I did check all the hinge points and the SB before I flew it so I know there's nothing broken.

Thanks for all the ideas.
 
If the dent in the rudder skin is the culprit and it is causing a non-zero hinge moment on the rudder in level flight, you could fix it for the moment with a wedge or tab and continue to fly. This assumes that nothing is damaged or broken, that this issue is just due to skin deformation. It would not be the first time a tab has been used to fix asymmetry. But you really want to be sure that there isn't something more sinister lurking under there.

If the rudder was actually twisted you would see wrinkles in the skin. But I could see a dent on one side inducing an asymmetry, especially if it was well back from the hinge line. The long term fix is to rebuild or replace the rudder. Which sucks. :mad:
 
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