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My RV-10 left aileron jammed at full deflection!

DCBrown198

Active Member
Patron
Something I thought might be of interest to RV-10 people. Perhaps other models as well. I also shared this with Van's.

I was laying on my back doing some modification to wiring underneath the instrument panel. While I was doing that work the control stick was deflected to the left. After completion of my work underneath the panel I discovered that the control stick was jammed in the full left position. Forward / rear travel was unrestricted, but there was no ability to move the stick left / right.

At the ailerons themselves, the right aileron (deflected down) could be deflected only very slightly (consistent with normal control system "slop"), however, the left aileron was locked very tightly in the full up position. No movement at all was possible.

I disconnected the left aileron push rod (W-1018) at the bellcrank inside the wing. (See page 23-9 in RV-10 plans). Only after lifting up on the rod did I free the aileron.

Here's what I discovered.

1. During final aileron installation/rigging what I believed to be aileron contact at the aileron stop was actually the shopped end of the vertical rivet on the W-1018 pushrod contacting the rear face of the rear wing spar opening. Please see the attached image. This contact mimicked what could reasonably be determined to be aileron stop contact.

The ailerons demonstrated required deflection angles even with the rivet/rear spar contact.

With the rivet acting as the false aileron stop there was approximately a .125 gap still remaining between the aileron and the actual aileron stop.

The behavior of the rivet/spar contact was easily confused with solid aileron stop contact. Furthermore, it is not easy to visually confirm proper aileron stop contact.

Both ailerons had this condition.

2. Over time the shopped end of the rivet, while making contact with the rear face of the rear wing spar, lost some of its squared finish. The rivet had rounded just enough to allow the rivet to "hop" over the rear spar and then snap down snugly on the forward side of the spar.

Remember that, due to the aileron pivot geometry, the W-1018 pushrod moves forward and down with forward movement. So when the pushrod moved forward, and the rivet "hopped" over the rear spar, the pushrod was held down even more securely with the rivet jammed on the forward side.

3. I had to add clearance at the bottom of the rear wing spar openings on both wings in order to assure no rivet/spar contact. The ailerons now properly contact the aileron stops without rivet interference.

4. This situation would likely have been unrecoverable if it had happened in flight. However, to get this situation to occur in flight would have been the result of hard-over full control stick deflection- something I hate to think of as responsive as the RV-10 is.

See the pics.

David
 

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Yup

I saw this on m 9A too. My pushrods are welded for this reason. The other option is to remove spar material around the hole to avoid this.

Everyone should check this, and it should be part of conditional inspection, not to mention first flight inspection.
 
Did the contact point also wear a hole in the pushrod forward of the rivet?

Glad this was found on the ground...almost certainly a serious if not fatal accident waiting to happen.

Good on ya for posting this, and a reminder to check ALL control systems carefully throughout the entire system for ANY rubbing/chafing/contact prior to first flight. Another potential chafe point, at least on the 7s, is the elevator pushrod where it passes through the rear spar...a lot of us have had to remove some material from the spar to make the pass-through large enough to avoid chafing (just a small arc of removed material is usually enough).

Excellent catch!
 
"Did the contact point also wear a hole in the pushrod forward of the rivet?"

No...that's a bit of powder coat paint peeled back. Likely from my fumbling with it.
 
Ditto

Also had this hang up on my 9a- had to smooth and file down shop head side, alter the “down” side and also remove extra opening material to ensure no hangup in flight. Scary.
 
Pretty tight in there

I don’t know how to weld and didn’t trust JD Weld epoxy.
 

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Very interesting. Glad you found it the way you did. I'm at this point in my -14A build. Could these ends be countersunk and double flush riveted instead?
 
Very interesting. Glad you found it the way you did. I'm at this point in my -14A build. Could these ends be countersunk and double flush riveted instead?

They are hard rivets to set so I would not countersink especially that they are small diameter tubes. You just need to make sure you have enough clearance which needs to be check regardless of riveted or welded piece.
 
They are hard rivets to set so I would not countersink especially that they are small diameter tubes. You just need to make sure you have enough clearance which needs to be check regardless of riveted or welded piece.

I haven't done these yet, but I'm unclear on why they are hard rivets to set. Don't they just get squeezed on the tube? What makes them difficult?
 
I haven't done these yet, but I'm unclear on why they are hard rivets to set. Don't they just get squeezed on the tube? What makes them difficult?

The round, smooth, and hard steel tube is hard to stabilize fully, and rivets are pretty long. They tend to want to bend over. I found that a series of partial sets worked better.
 
The round, smooth, and hard steel tube is hard to stabilize fully, and rivets are pretty long. They tend to want to bend over. I found that a series of partial sets worked better.

OK thanks.:) I'll be sure to practice first on some scrap now.
 
The round, smooth, and hard steel tube is hard to stabilize fully, and rivets are pretty long. They tend to want to bend over. I found that a series of partial sets worked better.
A very good advice. I found them setting them in a vise will give me the most control.
 
+1. Luckily I have a good friend that knows how to TIG weld.

Carl

I found a guy at our local airport with a machine shop and tossed him a few ten-buck bills to weld them. I did it mostly to avoid having to rivet the ends, but it's good to know that the welded ends might possibly be safer, too.
 
This same clearance issue can be found on all RV models not just the 10 if the holes were not "adjusted' to provide clearance, I have fixed numerous ones.
 
A very good advice. I found them setting them in a vise will give me the most control.

Yes - I was afraid of damaging the tube so used a vise with padding, limiting force to avoid crushing tube, but still a little tendency to move. In retrospect it might have helped to put some gaffers tape on the tube to give the vise a little more friction without so much force that it might crush the tube.
 
A couple things

First off, great discovery ! I assume this -10 hadn't been flown yet? When the FAA rep did my inspection before the pink slip, he sat in my -4 and slowly, meticulously moved the stick through every possible position, feeling and listening to everything..that was the only real thing he had that level of focus on. My main aileron torque tube was touching the nylon gatortail I had around the fuselage exit 2" cut-out making a nearly unnoticeable squeak just before the aileron hit the stop. he said "fix that before flight" and signed my pink slip. When I rivet those end fittings, I prefer to lay the MFG head on a steel block/bucking bar, and shoot the bucktail down with a 5/32" universal set. This gives you a nice rounded bucktail with minimal sharp edges, and keeps the gun control much better. The MFG head will slightly flatten, but that's acceptable.
 
Squeezing aileron pushrod rivets

The round, smooth, and hard steel tube is hard to stabilize fully, and rivets are pretty long. They tend to want to bend over. I found that a series of partial sets worked better.

The RV-14 Builder's Manual calls for AN470AD4-11 rivets to attach the threaded rod ends to the aileron pushrod tubes. The CS-00013 pushrod tube is 0.035" x 1/2" material, which has an OD of about 0.5" before powder coating. The -11 rivet length is such that the shop head end of the rivet shank sticks out of the pushrod tube just about the recommended 1.5D. I don't think you'd want to use a shorter rivet, because the threaded rod end is hollow with an ID of about 0.285", and the rivet shank is going to expand into that empty space when you squeeze it.

The RV-14 Builder's Manual states, in the bottom left corner of page 23-04, "Permanently install the threaded rod ends to the bellcrank to aileron pushrods as shown in Figure 3. These rivets can be difficult to set without them leaning over. Use a hand squeezer to squeeze them a little at a time. If the rivet begins to lean over, adjust the position of the rivet in the squeezer dies to oppose the leaning tendency." That comports with the "series of partial sets" that Dr. Billingsley found to work.

I like the suggestion by fixnflyguy. I might modify his approach by using a C-Frame riveting setup with a 1/8" universal set in the bottom and another 1/8" or 5/32" universal set in the shaft that the rivet gun drives. It would be helpful to tightly clamp the pushrod tube when doing this.
 
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Flex

The question arises if there are any flex under loading that would cause the clearance on the ground to be insufficient in the air?

How much extra clearance to leave for flying stresses?
 
"I assume this -10 hadn't been flown yet?"

Yes it had flown. It was reviewed by one of the best RV examiners. I shared it with him as well.

The ability of this situation to so effectively mask itself as proper aileron stop contact, and the possible after effects, is what drove me to want to share. The rivet to rear spar contact felt just like, and sounded just like, aileron stop contact.

Anyway, in all likelihood this situation would have manifested with others iust like me - during a pre-flight control check or similar. Highly unlikely that the stick would have been driven this hard over in flight.

David
 
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The question arises if there are any flex under loading that would cause the clearance on the ground to be insufficient in the air?

How much extra clearance to leave for flying stresses?

I'm not an ME or an AE, but it seems to me that the forces on the aileron pushrod will be tension and compression, not bending forces, assuming you don't have a bearing binding in the bellcrank attached to the spar or the rod end attached to the aileron.
 
Interestingly, in the Airbus I fly, there’s a torque tube with a rod end in it in the landing gear bay. The rod end is riveted in with cherry max rivets rather than solid rivets. I wonder if that’s an option for us too?
As I’m at just about that point with my wings, it keeps catching my attention!
 
Steel is weld able

I have had the rivet interferences early on in my building experience. Every plane that has come through RV Central gets those welded.
Seem to remember welding was an option in early plans books.
Bob Avery Avery Tools is on same airport as me,,, it’s real handy to have a Master tool man within walking distance. He has welded 108 aileron push rods for me. Two more coming in tonight! It’s a RV8..
 
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Interesting to see that those of us who have "assembled" a -12 did it the same way as Airbus. We have some pricey panel washers in common with Airbus too. :)





Interestingly, in the Airbus I fly, there’s a torque tube with a rod end in it in the landing gear bay. The rod end is riveted in with cherry max rivets rather than solid rivets. I wonder if that’s an option for us too?
As I’m at just about that point with my wings, it keeps catching my attention!
 

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Interestingly, in the Airbus I fly, there’s a torque tube with a rod end in it in the landing gear bay. The rod end is riveted in with cherry max rivets rather than solid rivets. I wonder if that’s an option for us too?
As I’m at just about that point with my wings, it keeps catching my attention!

There are several things to consider when contemplating using a CherryMax rivet in this application. Let me attempt a cocktail napkin analysis:
  • Universal head or flush head, or a compromise between the two?
  • Material compatibility (corrosion) between rivet and tube+threaded insert?
  • Grip length required?
  • Blind clearance, meaning how much clearance does the shop side of the rivet need inside the tube?

Regarding the manufactured head of the rivet, CherryMax rivets are available in universal, 100 degree and 120 degree flush, and Unisink (compromise between universal and countersunk) head styles. If the goal is minimum head height, one would go with the flush or Unisink heads. The problem with the flush head styles is one has to countersink a hole on a curved surface, in steel. That would lead me to the Unisink style. It takes a very shallow countersink.

Regarding material compatibility, I don't think you'd want to use an aluminum rivet (relatively small sacrificial surface area) in a steel tube (relatively large area). That would lead me on first impression to a Monel or INCO 600 rivet. The Unisink head CherryMax rivet is only available in Monel and aluminum.

Now for the grip length calculation: The pushrod is 0.035" and the threaded end has a wall about 0.075" thick. So let's use 0.110" as the grip required, which leads us to rivets with a grip range of say 0.063" to 0.125".

So far I've narrowed it down to a CR3555-04-2 rivet. If you think a universal head style would work, you could go with a CR3523-04-2 or similar.

But here's a problem: The blind grip length required by these rivets, meaning how far into the material you have to insert the unset rivet, is 0.355" for the CR3523-04 and 0.375" for the CR3555-04. If you subtract the required grip length of 0.110" from the pushrod tube diameter of 0.500" (maybe 0.510" with powder coat), you're left with 0.390" to 0.400". So the shop head of the set rivet better not be more than 0.025" high for the CR3555 or 0.045" high for the CR3523. And the rivet holes in the tube are opposite each other. So you might get one in, but even after you set it, you might not be able to insert the one on the opposite side all the way. One thing Cherry doesn't tell you is how much shop head sticks up above the material you're gripping. And how could they, without knowing the thickness of that material and how good a job you did of prepping (pre-lubricating, for example) and setting the rivet?

All this is not to say that there's not a blind rivet that will work. Cherry provides a lot of detailed specs on the CherryMax rivets in their document at https://www.cherryaerospace.com/docs/catalogs/CA-1011.pdf that made this analysis possible. And I don't think there's going to be a lot of torsional or tension stress on the pushrod tube that means you need the shear strength of a CherryMax rivet. Perhaps someone can take on the task of analyzing this problem with another rivet that Van's, Spruce, or SkyGeek sells.
 
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Interesting to see that those of us who have "assembled" a -12 did it the same way as Airbus. We have some pricey panel washers in common with Airbus too. :)

The MSP-42 has a grip length of 0.063" to 0.125". Check.

I think the leading 'M' means Monel. Check.

It has a head height of about 0.042" according to my dial calipers. Looks good.

It has a blind insertion depth of about 0.335". Might work.

I have no idea what its shear strength is. In a flaperon application, the pushrod should see higher compression loads than tension loads.

But I've already drilled my pushrods to #30. See Rick6a's post at https://vansairforce.net/community/showpost.php?p=91757&postcount=4

That last thing having been said, on page 23-03 of the RV-14 Builder's Manual, Van's has you drill the aileron torque tube and the VA-111 Threaded Rod Ends to #30 and rivet the rod ends to the torque tubes using six MSP-42 rivets.

And on page 23-06, Van's has you drill the CS-00009 Torque Tube Subassemblies and VA-162 Pushrod Ends to #30 and rivet them together with two MSP-42 rivets. Same with the WD-1014 Torque Tube Subassemblies and VA-162 Pushrod Ends. However, there is very little stress on the VA-162 Pushrod Ends, because they are just used to support the torque tubes between a bearing on the tank attach bracket and a bearing on the connector bracket on the aft part of the wing.

Update: Van's store sells the MSP-42 rivet, see https://store.vansaircraft.com/msp-42-blind-rivet-rivet-msp-42.html. On that page, they list as a cross-reference the SSD42SSBS rivet. See https://www.stanleyengineeredfastening.com/en-US/catalog-global/ssd42ssbs/p for specifications. These specs say the minimum hole size for the SSD42SSBS is 0.129" and the max hole size is 0.133". #30 is 0.1285". The SSD42SSBS rivet is pretty strong: 550 lbf in shear and 700 lbf in tensile strength. By contrast, an AN470AD4 rivet, properly set, has a shear strength of 319 lbf and a tensile strength of 466 lbf. (These numbers are based on Aircraft Spruce's figures of 26,000 psi and 38,000 psi for shear and tensile strength of a rivet made of 2117-T4 Al, and a cross sectional area of a 0.125" diameter rivet of about 0.0123 square inches.) And the SSD42SSBS rivet is made of stainless steel, so I wouldn't worry too much about corrosion in contact with the steel parts it's holding together. The only remaining question in my mind is whether I can fully insert one after inserting and setting one on the opposite side of the tubing.

Aircraft Spruce sells the CCP-42, for which they x-ref the SSD42SSBS: https://www.aircraftspruce.com/catalog/hapages/cherrynrivet.php.

Further update: I riveted together a piece of 0.063" scrap material and a piece of 0.040" scrap material using an MSP-42 rivet. The "shop head" of the rivet sticks up about 0.112" on the back side of the 0.103" of material. So the total length of the rivet from the underside of the manufactured head to the end of the "shop head" is about 0.215". If this were the 0.5" diameter aileron pushrod with the threaded rod end inserted, I would not be able to insert the 0.335" shaft of the MSP-42 rivet all the way into the opposite hole, even after pulling the first rivet. I leave to your imagination how you might still be able to pull the two MSP-42 rivets on opposite sides of the aileron pushrod and get the heads to set flush with the outside of the pushrod. On the RV-14A, you'd need to make that work eight times.

I hope I get partial credit for showing my work.
 
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Welding pics?

To me, this is a scary thing. I have not had any issues but I like the idea of having them welded. Can someone post a picture so I can show my welder? Thanks
 
Welded Pushrods

To see a number on photos showing preparation and finished welded push rods go to my post here, along with a number of informative posts regarding the process.

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I have been flying with these in my RV-7A for six years now with no issues.
 
There's certainly nothing wrong with welding them in, but the riveted versions will work fine, too. Regardless of how they're attached, you *still* have to ensure that there's no chafing or binding anywhere, and that may require relieving one or more pass-throughs throughout the airframe. You just may have to relieve it a little more if the rod ends are riveted in, that's all.

Welding won't obviate the need to ensure the systems is free of chafe points or the like.
 
two if by welding... one if by...

So If I have them welded, can I proof load test them?

How much weight should I hang from the ends to proof test the welds?
what is twice the expected flight loads in tension?
 
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Thank you Jim. I appreciate the pictures and link to the other thread.

To see a number on photos showing preparation and finished welded push rods go to my post here, along with a number of informative posts regarding the process.

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I have been flying with these in my RV-7A for six years now with no issues.
 
Here’s the Airbus tube I was talking about.
 

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I wonder if welding of the control pushrod is a non-standard aviation practice. It seems using rivet is standard, and according to Vans and Airbus. I wonder if Mel will ding you if you weld.
 
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