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

Smak 10-09-2021 01:51 AM

Rudder Pedal SB 99-6-1
 
If You're using inspection for SB 99-6-1, STOP ASAP!

This Failure occurred this morning while taxiing out for a weekend get away. Had it happened at 80 knots on takeoff beside the Hangar Line, I wouldn't be writing this! Right Rudder Pedal Left Seat! Non Pilot Wife in right seat.

Smak 10-09-2021 01:57 AM

RUDDER Failure
 
1 Attachment(s)
Yes SB 99-6-1 was complied with by inspection within 10 hours of failure!

scrollF4 10-09-2021 11:45 AM

By whoís direction?
 
Gerard,
Have you turned in the part for an engineering assessment, perhaps to Vanís? Are you relaying Vanís engineersí direction to suspend the SB? That failure is pretty notable, and Iím glad you two are OK, but I would caution folks against simply ignoring a standing bulletin without getting a solid engineering assessment into why that happened.

Kyle Boatright 10-09-2021 11:53 AM

Quote:

Originally Posted by scrollF4 (Post 1560876)
Gerard,
Have you turned in the part for an engineering assessment, perhaps to Vanís? Are you relaying Vanís engineersí direction to suspend the SB? That failure is pretty notable, and Iím glad you two are OK, but I would caution folks against simply ignoring a standing bulletin without getting a solid engineering assessment into why that happened.

The SB is for a 10 hour inspection, with replacement if any sponginess, hard rudder forces, etc. are experienced. Here's a link:

https://www.vansaircraft.com/wp-cont.../sb99-06-1.pdf

I figured 20 years down the road everyone had already modified their rudder pedals to get past the issue.

I'd recommend people make the mod/upgrade. Ain't hard, relatively speaking.

azrv6 10-09-2021 12:26 PM

An important reminder from the original poster to all RV6 and RV6A owners, many who are new to their aircraft, to verify the status of SB 99-6-1.

Although the SB provides the option to inspect the overhead rudder pedals every 10 hours, and explains how to inspect them, it is a much better course to repair or replace them per info in the SB.

I built my RV6 and have been flying it for 25 years. I replaced my overhead rudder pedals soon after the SB was published and inspection required replacing them. Ordered from Vans and several hours later the new pedals were installed.

Smak 10-11-2021 02:19 AM

Quote:

Originally Posted by azrv6 (Post 1560878)
An important reminder from the original poster to all RV6 and RV6A owners, many who are new to their aircraft, to verify the status of SB 99-6-1.

Although the SB provides the option to inspect the overhead rudder pedals every 10 hours, and explains how to inspect them, it is a much better course to repair or replace them per info in the SB.

I built my RV6 and have been flying it for 25 years. I replaced my overhead rudder pedals soon after the SB was published and inspection required replacing them. Ordered from Vans and several hours later the new pedals were installed.

Exactly my intention. Iím new to the RV world and my ( ew do me RV) was in full compliance with this and all SBs. I expressed as strongly as I know how to Sterling at Vanís tech support that this SB be changed, removing the inspection option and ďrequiringĒ replacement or reinforcing. The wisdom Iím getting from those who have seen the parts break is that the weld wasnít cooled properly (by applying heat) and that weekend the torque tube, which was the point of failure.
I have new rudder pedals on the way. They of course now come with gusset reinforcement.

A2022 10-11-2021 05:43 AM

yes, a 10 hr inspection interval for a part like this is nonsense. it should be a strict replacement.

an end tube welded connection like this is not designed to withstand hundreds of pounds of cycling load in bending. the stress concentration at the welded joint is the limiting feature.

there is only one thing more important than the engine.... the flight controls.

DennisRhodes 10-11-2021 09:11 AM

I checked my RV9 "older kit " yesterday. Appears to have all the gusset reinforcements as mentioned. An while you're standing on you head may as well check all the other welds and cable connections . All looked "fine on the 9".

rvbuilder2002 10-11-2021 10:45 AM

A few comments......
 
I was at Van's for the static testing of rudder pedal assemblies that we did after we first became aware of a weldment failure, and when this SB was issued.

An SB issued by a kit manufacturer has no regulatory basis. An owner can choose to totally ignore it if they like. The compliance time / method is often chosen by us to imply a level of urgency, but to also give some latitude for aircraft repositioning to have the work done by someone else, scheduling of that work, etc., but as already mentioned, it is some what a moot point because there is nothing regulatory about compliance with an SB on an experimental.

The failure noted in the attached photo is nothing like the actual original failure that the gussets prescribed by the SB were designed to prevent.
The gussets might have prevented this failure if they had been installed, because they do change the load distribution, but this failure mode is not the same.
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 following is my opinion based on experience and a bit of logical reason thrown in for good measure....

I do not think this failure occurred within the span of 10 flight hrs (Reasons described below). An inspection may have been done, but I think evidence of already existing damage was missed.

One piece of info (if known) that would support my opinion is knowing what the total time in service is.

Since the airplane has ungusseted weldments, it is likely an older build (finish kit predating the issuance of the SB in 1999) which has probably accumulated quite a few flight hrs without a failure.
If the failure has occurred through just the past 10 hrs, there would have to be something that changed in the operation of the airplane very recently that made the assembly fail now but not long ago.

I know that the current owner recently purchased the airplane. An RV changing ownership usually results in an investigation of applicable SB's and whether they were complied with.
It is entirely possible that the original builder (and possibly prior owners, if there was more than one) didn't know about the SB and had never inspected the rudder pedal assemblies for this type of failure.
If that were the case, the crack that ultimately cause the failure could have been propagating for quite some time.

Couple of side comments to the main subject-

Painting any welded assembly a dark color (black would be the absolute worst choice) is a very bad idea. It makes cracks just about impossible to visually detect. That is why we have always used very light grey or white for the color on all of our powder coated parts.

Inspection of welded assemblies like the rudder pedals is something that should be done with a high level of scrutiny during a condition inspection. An SB like this is issued to highlight an area that has become know to potentially develop a problem, but in reality it should already have been being inspected.
Primary point there is that just because an SB has been physically complied with, doesn't mean that you don't need to inspect that area any longer.

scrollF4 10-11-2021 01:35 PM

Quote:

Originally Posted by rvbuilder2002 (Post 1561287)
I was at Van's for the static testing of rudder pedal assemblies that we did after we first became aware of a weldment failure, and when this SB was issued.

An SB issued by a kit manufacturer has no regulatory basis. An owner can choose to totally ignore it if they like. The compliance time / method is often chosen by us to imply a level of urgency, but to also give some latitude for aircraft repositioning to have the work done by someone else, scheduling of that work, etc., but as already mentioned, it is some what a moot point because there is nothing regulatory about compliance with an SB on an experimental.

The failure noted in the attached photo is nothing like the actual original failure that the gussets prescribed by the SB were designed to prevent.
The gussets might have prevented this failure if they had been installed, because they do change the load distribution, but this failure mode is not the same.
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 following is my opinion based on experience and a bit of logical reason thrown in for good measure....

I do not think this failure occurred within the span of 10 flight hrs (Reasons described below). An inspection may have been done, but I think evidence of already existing damage was missed.

One piece of info (if known) that would support my opinion is knowing what the total time in service is.

Since the airplane has ungusseted weldments, it is likely an older build (finish kit predating the issuance of the SB in 1999) which has probably accumulated quite a few flight hrs without a failure.
If the failure has occurred through just the past 10 hrs, there would have to be something that changed in the operation of the airplane very recently that made the assembly fail now but not long ago.

I know that the current owner recently purchased the airplane. An RV changing ownership usually results in an investigation of applicable SB's and whether they were complied with.
It is entirely possible that the original builder (and possibly prior owners, if there was more than one) didn't know about the SB and had never inspected the rudder pedal assemblies for this type of failure.
If that were the case, the crack that ultimately cause the failure could have been propagating for quite some time.

Couple of side comments to the main subject-

Painting any welded assembly a dark color (black would be the absolute worst choice) is a very bad idea. It makes cracks just about impossible to visually detect. That is why we have always used very light grey or white for the color on all of our powder coated parts.

Inspection of welded assemblies like the rudder pedals is something that should be done with a high level of scrutiny during a condition inspection. An SB like this is issued to highlight an area that has become know to potentially develop a problem, but in reality it should already have been being inspected.
Primary point there is that just because an SB has been physically complied with, doesn't mean that you don't need to inspect that area any longer.

Scott,
What a well-stated comment. To me the biggest take-away is that the part appeared to have failed in a manner completely outside the failure mode addressed by the SB. Another reason for RV-6 drivers to NOT disregard the SB (as the OP so urgently urges).
Since this part failed at the weld, Iím curious to know whether there is a history of such failures? I canít tell if the cross tube was internally primed, which is supposed to decrease the chance of corrosion developing at the weld.


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