VAF Forums - Rudder Pedal SB 99-6-1

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- - Rudder Pedal SB 99-6-1 (https://vansairforce.net/community/showthread.php?t=199938)

I found cracks also

I have been doing my condition inspection over the past week and i also found cracks on my pedals, parts have been ordered.

The paint on most of my rudder pedals have all chipped away at the welds which suggests to me there is some movement, but 100% cracks were spoted on the back of the pedals.

They look like this.
https://photos.app.goo.gl/PxfgTHiiePnvhAK26

The revised service bulletin has been published.

Quote:

Originally Posted by Steve Melton (Post 1563203)

good. issue the revision and move on.

Got the email from Sterling at Van’s today (been busy picking up an airplane) that the update is in!
I’m Satisfied!!
Also, even though compliance is not mandatory (as with a certified AD), I implore you!! Make the Repair or Swap.

https://www.vansaircraft.com/service...ns/sb-99-06-1/

Im the OP who started this thread and swore I’d see this through!!

Smak

Quote:

Originally Posted by Smak (Post 1563568)

Good for you.

Yep, we have cracks too

RV6A 2100 hr
Cracks are on the forward (hard to see) side of the tube.

Quote:

Originally Posted by Smak (Post 1562360)

The wisdom from local engineers who have looked at the part is that the weld was not "normalized" with heat and this weakened the Torque tube (crystalizing some of the internal metal) which was the point of failure, NOT the weld itself which is entirely intact.

Smak

I have done a fair amount of research on this subject and the general wisdom in the welding community is that when TIG or gas welding of 4130 at thicknesses less than 1/8", normalizing is not necessary to maintain strength and integrity. precautions do exist to ensure that pre-heating is conducted when surface temps are below 70*. Pre heating the weld to 200* is good insurance when welding 4130.

Cracks will almost universally appear in the HAZ (where the crystal structure changes) on a weld like this, as it is the weak point, but that doesn't mean it did not meet the designed strength of the welded joint. Engineers generally discount some strength at many weld joints.

Larry

My rudder pedals have beein reinforced with the finger patches supplied by Vans, I just picked them up from the welder today. The pedals have not been previously installed, since I'm still building.

It took just over 2 hours of labour to fix the pedals and also to put the gussets on the steps (to prevent them from cracking.) The 8 finger patches as supplied by Vans were not a good fit to the rudder tube and needed a bit of grinding. The welder normalized the welds after using TIG.

Pic attached and I am very happy with the way they turned out and hope they will do their job for the life of the plane.

Compression Cracks

I'm not a welding expert but am a mechanical engineer. It's clear that it's unrelated to any welding technique heat treatment. The pedal is simply being forced into the tube.

Back from the bead blast, the compression crack is invisible from front or back but very obvious from the bottom. So to really see it you'd have to luck vertically from the floor underneath the pedal.

So, my pedals are off to Russ McCutcheon to make them right.

Mandatory Means Mandatory

Quote:

Originally Posted by Smak (Post 1562391)

I made a 90 right on Taxi out, felt something, let's say "weird" and thought it was just the tailwheel taking a bit to recenter. I made a Full Control Check just before takeoff and that's when the right pedal stayed full forward. I now believe the one side/arm snapped off with that first 90 right and the second broke loose with the control check. About 500 hours on a '96 kit completed in 2001.
...
Put the new pedals on!
Smak

My scenario was almost the same: I taxied, and on take off and right rudder application, things felt a little less than authoritative, and I attributed it to a crosswind. Flew to a nearby airport to pick up a friend and do some night flying and landed, but the steering seemed a little squirrelly, still not really thinking anything is wrong, just the normal tail-wheel games (all right turns at this airport to the ramp). Friend jumped in, we called ground for taxi, and as we started taxiing, my right pedal gave way completely, I gave him the controls and he taxied us back. I pried the pedal forward, and it came off completely.

This is a new-to-me RV-6, 1997, ~1150hr. When this thread first started, I went and "inspected" my rudder pedals, but I couldn't find any chipped paint or any apparent cracks (probably didn't realize well enough what to look for). I kept telling myself, I need to get that rudder pedal SB done, it could be serious if that actually fails...

I have ordered the gussets tonight from Van's, but now I wonder: are my current pedals repairable once they are broken? Or do I need all new assemblies? I didn't get a very good picture, but here it is:
Attachment 20817

Either way, it appears everything is backordered, so I am on the ground until I get something.

Meanwhile, another friend saw me getting ready to takeoff, and snapped a pic before the "interesting" flight. As DR mentions on the homepage, beautiful evening/night for flying, but things work out like they do for a reason...
Attachment 20818

Quote:

Originally Posted by rvbuilder2002 (Post 1561287)

The actual failure mode being prevented by the addition of the gussets was a buckle failure on the side of the tube loaded in compression under load from high foot pressure. That is why the gussets are added to only one side of each tube, and why some are on the fwd. side, and some are on the aft side (depending on which side of the tube is highly loaded in compression when rudder / brake pressure is applied).

The instructions I got with my gussets don't talk about installing some on the aft side of the pedals. Seems that all the pedals would be loaded in compression on the forward (firewall) side. Can you clarify how some of the pedals could be in compression on the aft side and which ones need the gussets installed on that side, please?