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Rudder Flutter

I’m amazed when we see these type of posts about a dangerous design change or dangerous build, and many experts who weigh in, yet the poster’s slowness to absorb the warnings.

Or we're being trolled. I'm just sayin'....
 
Well said

Good point Dan. I forgot the troll angle.

I think of that troll stuff every time I see a post questioning the fact Vans uses TAS rather than IAS. Hopefully a service bulletin One day from Vans will Clarify that troll bait.

Or we're being trolled. I'm just sayin'....
 
Rudder flutter

Hang in there folks. 1) working with someone at the factory. 2) scheduled renown RV expert to look at the tail 3) can’t get to airport because of road construction. Will get you photos as soon as I can 4) I am well aware that I own a Lemon. I can’t sell it in this condition. Are you seriously condemning this airplane without ever seeing it? A dozen A&Ps deemed it airworthy over the last twenty two years. They actually inspected it and signed the airframe logs. None of the other owners did anything. We are trying to correct problems as they occur. Rudder oscillation is the latest. 5) we haven’t flown it since you made your comments, so have patience. We will update you as soon as we learn something. 6) trolling? Don’t people come to this forum with real problems seeking advice of the RV community? This is my first post on this forum. I turned to you when two local RV mechanics and the factory had no ideas. You have been great with ideas to check. What have I done to cause vitriol?
 
Hang in there Frenchy. Lots of constructive feedback has been shared and I think you've been very receptive. The troll thing was from another topic not too long ago.. a guy was basically gloating that he did 250kts indicated or something in his RV-9A and what a hoot it was.. and dozens of concerned experts here warned him about that sort of thing.. and he basically said his flight instructor told him it was fine to do that and he was listening to his "expert" instructor over all the collective wisdom of everyone who participates here... leading to speculation the guy was trolling everyone on this forum for kicks and giggles..
 
Are you seriously condemning this airplane without ever seeing it?
In a word, yes. Based on what you've shown, and what you've described, grounding the plane until this is sorted out *is* the only prudent response.

trolling? Don’t people come to this forum with real problems seeking advice of the RV community? This is my first post on this forum. I turned to you when two local RV mechanics and the factory had no ideas. You have been great with ideas to check. What have I done to cause vitriol?
We've had a couple of threads recently where someone went much further down the rabbit hole than you have in terms of describing a situation that was clearly dangerous to most of the VAF crowd, but denying that there was any issue. After a while, the only explanation that made any sense was that the poster was trolling us and didn't even own an RV. So when your first post here is something as potentially dangerous as your situation, you might be able to understand some people might think it's less than genuine.
 
Hang in there folks. 1) working with someone at the factory. 2) scheduled renown RV expert to look at the tail 3) can’t get to airport because of road construction. Will get you photos as soon as I can 4) I am well aware that I own a Lemon. I can’t sell it in this condition. Are you seriously condemning this airplane without ever seeing it? A dozen A&Ps deemed it airworthy over the last twenty two years. They actually inspected it and signed the airframe logs. None of the other owners did anything. We are trying to correct problems as they occur. Rudder oscillation is the latest. 5) we haven’t flown it since you made your comments, so have patience. We will update you as soon as we learn something. 6) trolling? Don’t people come to this forum with real problems seeking advice of the RV community? This is my first post on this forum. I turned to you when two local RV mechanics and the factory had no ideas. You have been great with ideas to check. What have I done to cause vitriol?

Yes, it is unfortunate that in this day and age of instant communication, that people assume the worst just because there hasn't been instant response to queries for more info or confirmation that certain suggestions have been followed.

Jean and his partner have provided me with a bunch of photos to look at and they for the most part show that the empenage attachment to the airplane has been properly repaired (hoping to get a couple more photos showing an alternate view that I haven't seen). In the process of doing so, re-enforcement doublers were added to the aft top deck (A fix often prescribed by Van's for mis-drilled fwd attach holes), and the modifications to the horizontal stabilizer detailed SB-14-01-31 (including incorporation of the doublers) was completed.

It appears to me that this all started with a construction error on the fuselage.
I think the 612 bulkhead was installed flush with the aft edge of the tail cone skins rather than having the skins extend beyond. This error probably wasn't discovered until work was begun to fit the vertical stab. By this time the horizontal stab would have already been fitted.
If you look closely in the photos that Jean posted in this thread, you can see unused holes for where (it looks like) the horizontal fwd spar was originally attached but then was moved aft. In other photos you can see that a skin extension was added to the aft end of the tail cone, I assume to attempt to bridge the large gap to the rudder that developed when the vertical was re-positioned aft.

I think the builder decided it was easier to move the horizontal stab aft to match the position of the vertical stab., than it was to correct the issues with the fuselage bulkhead (the photos I was provide appear to show that the F-612 bulkhead was replaced and located to the proper position, and the added on skin extension was removed).

Next thing...... figure out what is causing the unstable (I don't consider it actual flutter) rudder. It sounds like it may be a turbulated airflow issue caused by a now very poorly fitting emp. fairing (an apparent by product of all of the other work that has been done).

Stay tuned...... for the rest of the story
 
Neither vitrol or assumption. Merely a possibility. Scott says "not so"....good to hear.
 
Thanks, Scott

Scott has applied outstanding skills for thread-upset-recovery. :D

Applause . . .
 
My experience

In post #10 , my friend Al mentioned my recent experience .

I removed my rudder to install a TailbeaconX and stop drill cracks in the skin at 4 rivet locations at the trailing edge . I removed it so I could do the work at home .

Upon reinstalling and flying I now had a rudder buffet that started at 135-140 kts . In 10 yrs of owning the airplane it had always been solid all the way to Vne .

I attributed it to the installation of the TailbeaconX so I returned to my original configuration but the buffet remained .

That started a month long process of many checks and small changes being done with disappointing test flights . Van’s also offered suggestions to no avail .

Interestingly , the buffet could always be stopped with pressure applied to either rudder pedal but not both .

Long story short . My early vintage rudder skins were flexing . The camber would change due to airloads and the rudder would bounce back and forth .

It’s possible that my rudder was always on the ragged edge of doing this but maybe the stop drilling softened up the skin just enough to put it over the edge .

To confirm, I applied some small 0.020” aluminum stiffeners externally with VHB tape to the crack locations . Problem solved !

The long term fix is a new rudder with thicker skins , longer stiffeners being joined at the TE with RTV .

I’m mentioning it here because so far this rudder anomaly is undocumented on VAF .

It’s possible that your older 6 also has a floppy rudder .

Another lesson learned from this experience is to not fixate on recent changes as the cause of your problem. Since you had never had the airplane up to 175 mph before , you can’t be sure that your rudder issue is due to the stab mislocation .

Good luck ,

Marc
 
Mark
I’ve delt with cracks at both front & rear of those stiffeners on various planes. With new rudders, in addition to the rear RTV treatment you describe, I now shape the front of those stiffeners so I can bend a 90 deg tab at that end so a dab of RTV can glue it to the spar. Results in an even stiffer structure never to crack again.
Elevators, same treatment, always keep the RTV blobs small.
 
Thank you!

FrenchyRV-6A,

Thanks for sharing your experiences. It's times like these, I am grateful to know the "Vans Community". While it doesn't pertain to my model, it's a learning experience nonetheless.

Humbling experiences such as with your plane, while disheartening, can be learning experiences for us all.
 
Rudder Oscillation

Moving tail forward caused some slack in the rudder cables. A&P installed bushings that stretched rudder cables. Rudder oscillation disappeared. Airplane test flown to Vne with no rudder oscillations.

Factory rep agrees that ill fitting tail inspection panel probably caused disturbed flow over rudder.
 
Moving tail forward caused some slack in the rudder cables. A&P installed bushings that stretched rudder cables. Rudder oscillation disappeared.

This makes no sense. In the standard RV design if you pull the rudder pedals aft the cables go slack. You cannot ‘stretch’ them.

Factory rep agrees that ill fitting tail inspection panel probably caused disturbed flow over rudder.

This makes more sense.
 
Moving tail forward caused some slack in the rudder cables. A&P installed bushings that stretched rudder cables. Rudder oscillation disappeared. Airplane test flown to Vne with no rudder oscillations.

Factory rep agrees that ill fitting tail inspection panel probably caused disturbed flow over rudder.

I'm so glad to hear that this was all resolved well. I hope the rest of the airplane is solid and serves you well. Hopefully you have relieved it of its 'lemon' status and although you have been through more ordeal than most buyers, you are now happy with it.
 
Vne is not necessarily the number on the airspeed indicator. On RVs, it's true airspeed. Flying out of Colorado, the indicated airspeed will be lower than true airspeed, and that needs to be taken into account.

Also, it's not likely that you had full-fledged rudder flutter because you survived. Flutter is usually destructive, almost explosively so. Can you describe what happened and what the flight conditions were more thoroughly? Did the post-flight inspection reveal any damage?

Dave

Flutter is not always catastrophic. I know of several instances of it that were not catastrophic to pilot undergarments. This case sounds like a much lower frequency event so likely not flutter.

I had a similar mismatch between the hstab and vstab on my 4. There was a half inch spacer block required where the forward vstab spar attaches to the forward hstab spar. It was an old slow build kit and I just put it down to a tolerance stack up. But structurally it seems to be built to plan other than that.
 
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