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Van's Air Force
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SB 12-09-26: Loose U-1202 Attach Bolts
- Thread starter DeltaRomeo
- Start date
Its kind of an incomplete SB. Check for cracks before further flight and if you find any call us...not before Monday of course. Huh? Shouldn't the fix be part of the SB?
Van?s engineering staff is actively evaluating the information we?ve been receiving from the field and will release ?generic? repair/reinforcement information as it becomes available
Van?s engineering staff is actively evaluating the information we?ve been receiving from the field and will release ?generic? repair/reinforcement information as it becomes available
I appreciate Van's stepping up to the Plate on this one, and think this forum - if nothing else - has served as a valuable conduit for that....
But - "Before Further Flight" is the most serious of all airworthiness Directives. It means "Grounding" - the very most draconian of all categories. You 175+ flying airplanes are now officially GROUNDED - a BIG switch from "Send us your reports." VERY serious situations rarely require invocation of that mantra - instead they might say "Within 10 hours" or "Within 25 landings" or some such. (In big airplanes, the absolutely most extreme situations will say the airplane may be flown to a facility where the inspection may be performed." (I use the latter VERY often!)
Guess we need to go from INFO to ACTION on this one!
Bob Bogash
N737G
But - "Before Further Flight" is the most serious of all airworthiness Directives. It means "Grounding" - the very most draconian of all categories. You 175+ flying airplanes are now officially GROUNDED - a BIG switch from "Send us your reports." VERY serious situations rarely require invocation of that mantra - instead they might say "Within 10 hours" or "Within 25 landings" or some such. (In big airplanes, the absolutely most extreme situations will say the airplane may be flown to a facility where the inspection may be performed." (I use the latter VERY often!)
Guess we need to go from INFO to ACTION on this one!
Bob Bogash
N737G
Actually, it is not an Airworthiness Directive. Those can only be issued by the FAA and only on Type Certificated aircraft.
All customer built RV-12's are Experimental (either E-AB or E-LSA). There is technically no regulatory binding notification that any kit manufacturer can make for an airplane certificated as experimental. That being said, it is then the pilots responsibility to make a determination of whether their RV-12 is in a condition for safe operation, without first checking the torque of said bolts.
I guess it doesn't matter what the situation.... when Van's doesn't issue a notice the first day they receive info from one owner, everyone is up in arms about it.
When they do issue something, based on a pattern of available information, people complain about having to inspect something before the fly again.
Or they complain that the information is incomplete.... The issuance could have been delayed, but then there probably would have been complaints of "why is it taking so long"?
Sheesh
Yes.... should say U-1202
Van's supports some 7800 flying RVs out of that little hangar in Oregon. That's more than the number of Boeing 737s out there. Give 'em a BREAK, guys
Tony
What Tony said! I will second the "sheesh".
Me too, and note also " as of the date of this bulletin, Van's is actively evaluating this issue to determine if other factors may be relevant."
The guys at the factory are taking these reports seriously, so let's give them some time to work through it.
Further information from N712BK
I provided additional information to Van?s at their request since I submitted my RV-12 Feedback Form on 9/16/12. I removed the forward outer landing gear nuts and washers and inspected the area around the bolt holes for signs of cracking. On each side I found a single crack radiating forward from the bolt hole to the front edge of the C-Section. This was the first reported case of a single crack radiating from the forward hole and provided evidence that supported Van?s analysis of where the first crack would appear if you had loose landing gear outer bolts. I also removed the two small side skins to inspect the saddle and bolt heads from below and found a gap between the forward bolt head and saddle. There was also interference between the shop head of the rivet on the forward bulkhead and the saddle.
It only took 33 landings from my Second Condition Inspection on 5/29/12 to my inspection on 9/11/12 for the fuselage skin wrinkles to get worse and for the C-Section crack from each forward bolt hole to occur (this is speculation on my part since I did not remove the nuts and washers at the Second Condition Inspection).
My advice is to pay attention to the Service Bulletin. Had I continued to fly N712BK I am sure that there would have been additional damage to the side skins and C-Section (again speculation) and a more difficult repair. Bob Kibby
I provided additional information to Van?s at their request since I submitted my RV-12 Feedback Form on 9/16/12. I removed the forward outer landing gear nuts and washers and inspected the area around the bolt holes for signs of cracking. On each side I found a single crack radiating forward from the bolt hole to the front edge of the C-Section. This was the first reported case of a single crack radiating from the forward hole and provided evidence that supported Van?s analysis of where the first crack would appear if you had loose landing gear outer bolts. I also removed the two small side skins to inspect the saddle and bolt heads from below and found a gap between the forward bolt head and saddle. There was also interference between the shop head of the rivet on the forward bulkhead and the saddle.
It only took 33 landings from my Second Condition Inspection on 5/29/12 to my inspection on 9/11/12 for the fuselage skin wrinkles to get worse and for the C-Section crack from each forward bolt hole to occur (this is speculation on my part since I did not remove the nuts and washers at the Second Condition Inspection).
My advice is to pay attention to the Service Bulletin. Had I continued to fly N712BK I am sure that there would have been additional damage to the side skins and C-Section (again speculation) and a more difficult repair. Bob Kibby
I'm well aware of the technical differences between "true" AD's and Experimental Amateur Built's, Scott, but try having an incident without being in compliance with a Van's SB, and see what the insurance company's claims adjuster will tell you. Or worse yet, the Plaintiff's attorney. Van's SB's are just as binding as the FAA's, except they're not issued by the government. Non-comply at your (legal) peril.
I have followed this thread carefully since started and have not been clamoring for Van's to "do something." Since you posted Van's awareness and engineering evaluation, I figured you guys were doing just that. My heartburn is with the "Before Further Flight", and the switch from Idling to Full Throttle. If you read all of the RV-12 SB's, you'll find a pronounced tendency to use that classification. In the T/C world, those words are essentially NEVER used, even in the most dire circumstances (the DC-10 got one after the ORD accident.) There's almost always a little wiggle room, which is what I'm suggesting - something like "Within the next 10 landings", or "Within the next 10 hours flight time", or, one Boeing uses frequently, "At the earliest opportunity where tools, equipment, man-power, and/or facilities are available to perform the noted tasks."
As Van's has written it, if you're away from your home base and find out about this, you're SOL. So, Tony, if you're surfing VAF on your new Ipad while waiting for your fish & chips to arrive up at the Spruce Goose at Jefco (or maybe Hoquiam or Friday Harbor), you're suddenly DIW (Dead In the Water for you non-nautical types.) This applies to any other RV'er who is out on a trip somewhere - say Oshkosh, or visiting Aunt Sarah. If you read the compliance description, it doesn't look like something that would be easily accomplished with your fly-away tool kit. Or out on the ramp (or grass) somewhere.
So, Scott, I applaud the SB, but don't think a "Sheesh" is warranted because I complained about your going from Open Circuit to Closed Circuit.
And - Tony - having that many airplanes out there means you're not a Mom & Pop outfit cranking a few kits out in your garage.
While we're at it, let me say that we're not just talking tools, but also parts and supplies. I just this week replaced the large AN6 bolts on my airplane. I replaced them because after looking at them carefully -- due to this thread, -- they were suspect to my mind, being drilled bolts for a castellated nut. It took me two order cycles with Van's for me to get the "right" bolts - AN6-24 bolts per 35-03 Rev 1. (Invoice 21367). To my surprise, they came drilled. I installed them anyway, just using the AN365 elastic stopnuts and one NAS1149 washer - as called for on the Plans sheet - and which I also bought new.
After reading the SB, I learned that they SHOULD have been AN6-24A bolts - the "A" being undrilled. And, they should be -23's and not 24's. That's because of Rev 2 to 35-03, which was made 05/10/11 (but not released to builders until 10/12/11.) I reviewed this Revision and could find no changes that would affect me.
Of course, I was wrong. But, how could I know? None of Van's Revisions give the slightest clue (as far as I've been able to determine), as to what the changes are. So the user is left to try and proof every detail on every page trying to discern what the changes are, and their significance. This has really been apparent in the Rev 1 Update (?) to the Skyview POH.
I will start a new thread on this, and have been planning to for quite some time. Maybe now's the time.
Bob Bogash
N737G
David Paule
Well Known Member
Van's does say that they'll suggest repairs on a case by case basis for now.
Dave
Dave
I disagree. If you have an accident that is in no way related to the landing gear, it is highly unlikely that the Ins company would have any grounds to deny the claim since in the FAA's eyes, a service bulletin doesn't constitute unairworthy (not even with certificated aircraft).
I disagree - see above
I believe work is being done towards changing the revision documenting process, so that this doesn't happen any longer.
I agree, Scott - but if you did, say - buckle a leg, and the airplane slewed off the runway and took out half a dozen parked airplanes, that's where the gotcha is gonna get 'ya.
Obviously, you only get into trouble for something that happens that's related to the SB or AD in question.
Excellent! Big cheer! I'll save my new thread.
Bob Bogash
N737G
dick seiders
Well Known Member
Just wrapping up the annual condition inspection on my 12. Checked gear bolts today and found all at torque specs with no signs of any damage of any kind to channel, skins, or brake lines. I had torque sealed the nuts and bolt heads originaly and saw no disturbance in the materials. There was no wiggle or looseness determined in any of the components. I suspect this is the case with most of the 12's out there based on what I have read in the related thread. So the big question remains. What is going on with roughly 5 % or so of the flying 12's? Hopefully an answer soon.
Dick Seiders
Dick Seiders
I applaud van's for addressing this issue, even as an intermediate step. I have two questions:
How to tap on the bolt heads?
Seems one must jack up the airplane to ascertain for sure seating or rivet interference of the 1202 plates. I think mine seated well during assembly but not absolutely sure.
My nuts required a 1/2 turn to torque them last week after only 16 hours and approx 35 landings, thid prior to the service bulletin.
Also my volume seems to be stuck on full - the vol knob has no effect. Any ideas?
Doug Dahl
How to tap on the bolt heads?
Seems one must jack up the airplane to ascertain for sure seating or rivet interference of the 1202 plates. I think mine seated well during assembly but not absolutely sure.
My nuts required a 1/2 turn to torque them last week after only 16 hours and approx 35 landings, thid prior to the service bulletin.
Also my volume seems to be stuck on full - the vol knob has no effect. Any ideas?
Doug Dahl
Scott
Remember everyone...Scott is on here because he wants to be. I, for one am thrilled to watch him take it and give it right back. Unfortunately, sometimes you have to "bait him" to get his opinion. But then his opinions are invaluable. He is not just a Van's employee...he is part of the team that builds the new designs and provides the process...then he maintains what he builds. He is truly the first builder. As you can tell, he's not shy or afraid to speak his mind. He does get frustrated but so do we. I like Scott, just the way he is...and will continue to enjoy his input (even when he's wrong...lol).
Remember everyone...Scott is on here because he wants to be. I, for one am thrilled to watch him take it and give it right back. Unfortunately, sometimes you have to "bait him" to get his opinion. But then his opinions are invaluable. He is not just a Van's employee...he is part of the team that builds the new designs and provides the process...then he maintains what he builds. He is truly the first builder. As you can tell, he's not shy or afraid to speak his mind. He does get frustrated but so do we. I like Scott, just the way he is...and will continue to enjoy his input (even when he's wrong...lol).
Scott is not wrong very often. I appreciate the very helpful advice that he has given over the years. He does not like criticism of Van's Aircraft. That is to be expected. Most of us have pride in the work that we do. Keep up the good work, Scott.
One thing that the service bulletin does not mention is lifting the RV-12 to take the weight off from the landing gear while tightening bolts. I think doing that is a good idea to minimize possible binding of the bolts. It is not hard to lift the aircraft using the sawhorse method. Push the tail down, put a sawhorse under the bulkhead near the steps, then lift the tail with a scissor jack under the tie-down eye-bolt.
Joe Gores
One thing that the service bulletin does not mention is lifting the RV-12 to take the weight off from the landing gear while tightening bolts. I think doing that is a good idea to minimize possible binding of the bolts. It is not hard to lift the aircraft using the sawhorse method. Push the tail down, put a sawhorse under the bulkhead near the steps, then lift the tail with a scissor jack under the tie-down eye-bolt.
Joe Gores
yankee-flyer
Well Known Member
A lot more than 5%, Dick
Of those who have reported checking their outboard bolts, it look like over 80% have found them loose, ever after as little as 35 lours flying time. Now the percentage with buckled skins IS small, and I think is due to something else entirely.
Wayne 120241/143WM
Of those who have reported checking their outboard bolts, it look like over 80% have found them loose, ever after as little as 35 lours flying time. Now the percentage with buckled skins IS small, and I think is due to something else entirely.
Wayne 120241/143WM
Jacking up the airplane to ascertain seating
Seems one must jack up the airplane to ascertain for sure seating or rivet interference of the 1202 plates. I think mine seated well during assembly but not absolutely sure.
. Any ideas?
Doug Dahl[/QUOTE]
I would think you would want the weight on the gear to see that the the bolt head was seated to the saddle. With the weight off the gear I would think that the weight of the gear leg and wheel assembly would possibly pull down on the saddle and close any gap there was with the saddle. I found that my bolt heads were not seated with the weight on the gear. I have removed the small fuselage side skins so I could see the bolt heads but had trouble tellling whether they were seated or not. I took a photo with my iPhone and then downloaded it to Picasa 3 on my Desktop. By magnifying the bolt head to saddle area of the photo you can really see if there is a gap or not. I also sent the photo to Rian and he confirmed that I had a gap and pointed out the interference with the shop head of the bulkhead rivets. An interesting aside is that I thought I had found a sigificant problem when I noticed that I had a gap between the saddle and scuff plate at both ends of the saddle. Rian responded with the following:
"There should be a gap between the saddle and the scuff plate. This assures that the saddle is snug against and holding the gear leg."
Just goes to show that some gaps are "good" and some gaps are "bad". I believe that the reason the SB instructs us to "Use an even torquing sequence back and forth between each of the bolts" (fore and aft bolts- clarification by me) is that they don't want you to bottom out one side of the saddle on the scuff plate. My thoughts, Bob Kibby N712BK
Seems one must jack up the airplane to ascertain for sure seating or rivet interference of the 1202 plates. I think mine seated well during assembly but not absolutely sure.
. Any ideas?
Doug Dahl[/QUOTE]
I would think you would want the weight on the gear to see that the the bolt head was seated to the saddle. With the weight off the gear I would think that the weight of the gear leg and wheel assembly would possibly pull down on the saddle and close any gap there was with the saddle. I found that my bolt heads were not seated with the weight on the gear. I have removed the small fuselage side skins so I could see the bolt heads but had trouble tellling whether they were seated or not. I took a photo with my iPhone and then downloaded it to Picasa 3 on my Desktop. By magnifying the bolt head to saddle area of the photo you can really see if there is a gap or not. I also sent the photo to Rian and he confirmed that I had a gap and pointed out the interference with the shop head of the bulkhead rivets. An interesting aside is that I thought I had found a sigificant problem when I noticed that I had a gap between the saddle and scuff plate at both ends of the saddle. Rian responded with the following:
"There should be a gap between the saddle and the scuff plate. This assures that the saddle is snug against and holding the gear leg."
Just goes to show that some gaps are "good" and some gaps are "bad". I believe that the reason the SB instructs us to "Use an even torquing sequence back and forth between each of the bolts" (fore and aft bolts- clarification by me) is that they don't want you to bottom out one side of the saddle on the scuff plate. My thoughts, Bob Kibby N712BK
I complied with the SB today. Thanks to the suggestion (Kibby?) about removing the lower small side skins; that helped a great deal.
No cracks found; didn't expect any, no hard landings all on hard runways. Did have a little rivet interference and rounded off the u 1202's.
Took about three hours. did not jack the plane up.
Doug Dahl
No cracks found; didn't expect any, no hard landings all on hard runways. Did have a little rivet interference and rounded off the u 1202's.
Took about three hours. did not jack the plane up.
Doug Dahl
SB completed...
Completed the SB on my 12 today. I drilled off the two Cover Plates to get a good look at the hardware after 168 hours, and a lot of landings, all on hard surface.
As found, one of the U-1202 brackets did have a small rivet interference and gaps on each side did not look quite equal. The other U-1202 bracket looked square. There were a lot of threads showing beyond the nuts on the AN6-24A bolts. I believe these nuts were bottomed out on the bolts, but some clamping was taking place because there was an imprint of the washer in the powder coating on the bracket.
After taking off the nuts on the outboard AN5 bolts I found no cracks in the C-channel but it was apparent that the washers do not bear the full 360°, as was noted in previous posts:
I corrected the rivet interference by slightly grinding the U-1202 per the SB. I used the even torquing sequence and verified the U1202s were holding the gear leg evenly. I added an additional washer on each of the AN6-24A bolts per the SB.
One thing that I would like to see is a change from rivets to nutplates and screws holding on the F-1275G left and right Cover Plates. This might be something we could do individually, post AW inspection.
Tony
Completed the SB on my 12 today. I drilled off the two Cover Plates to get a good look at the hardware after 168 hours, and a lot of landings, all on hard surface.
As found, one of the U-1202 brackets did have a small rivet interference and gaps on each side did not look quite equal. The other U-1202 bracket looked square. There were a lot of threads showing beyond the nuts on the AN6-24A bolts. I believe these nuts were bottomed out on the bolts, but some clamping was taking place because there was an imprint of the washer in the powder coating on the bracket.
After taking off the nuts on the outboard AN5 bolts I found no cracks in the C-channel but it was apparent that the washers do not bear the full 360°, as was noted in previous posts:
I corrected the rivet interference by slightly grinding the U-1202 per the SB. I used the even torquing sequence and verified the U1202s were holding the gear leg evenly. I added an additional washer on each of the AN6-24A bolts per the SB.
One thing that I would like to see is a change from rivets to nutplates and screws holding on the F-1275G left and right Cover Plates. This might be something we could do individually, post AW inspection.
Tony
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tim walter
Well Known Member
Completed the SB on my 12 today. I drilled off the two Cover Plates to get a good look at the hardware after 168 hours, and a lot of landings, all on hard surface.
As found, one of the U-1202 brackets did have a small rivet interference and gaps on each side did not look quite equal. The other U-1202 bracket looked square. There were a lot of threads showing beyond the nuts on the AN6-24A bolts. I believe these nuts were bottomed out on the bolts, but some clamping was taking place because there was an imprint of the washer in the powder coating on the bracket.
After taking off the nuts on the outboard AN5 bolts I found no cracks in the C-channel but it was apparent that the washers do not bear the full 360?, as was noted in previous posts:
I corrected the rivet interference by slightly grinding the U-1202 per the SB. I used the even torquing sequence and verified the U1202s were holding the gear leg evenly. I added an additional washer on each of the AN6-24A bolts per the SB.
One thing that I would like to see is a change from rivets to nutplates and screws holding on the F-1275G left and right Cover Plates. This might be something we could do individually, post AW inspection.
Tony
Good idea Tony, I definitely think that would help inspections down there.
Also that's a very telling photo, you should definitely send that to Vans.
The problem does not seem to be - based on your picture- interference with rivets - it appears to be a "shoulder" or non-flush machined pocket that prevents the washer from bearing 100% on the web of the channel. What's needed is a radiused washer to even the difference in height (or grinding the pocket down to flush - ouch!)
Did you do this with the airplane on the gear? Or jacked (Remember - I have your sawhorse stands....)
Could you have done this in Friday Harbor? Just wondering. You know - "Before Further Flight"?
Bob Bogash
N737G
Jetguy
Well Known Member
How about this!
After following this thread one thing I can see that I don't like is that little lip shown in Tonys picture and pointed out in other post. Maybe Vans could offer all RV12 owners a special machined washer with a set bend on the bottom of the washer but even across the top where the nut would rest on it so that when the nut is tighten it would put equal pressure 360 degrees around the surface at that location.
I'm sure with all the special tools they have this wouldn't be to much of a problem to make. As a minimum change the machine process when making the spar for future RV12 so that it is flat at that location. Just my personal observation. I have checked my and found no cracks.
After following this thread one thing I can see that I don't like is that little lip shown in Tonys picture and pointed out in other post. Maybe Vans could offer all RV12 owners a special machined washer with a set bend on the bottom of the washer but even across the top where the nut would rest on it so that when the nut is tighten it would put equal pressure 360 degrees around the surface at that location.
I'm sure with all the special tools they have this wouldn't be to much of a problem to make. As a minimum change the machine process when making the spar for future RV12 so that it is flat at that location. Just my personal observation. I have checked my and found no cracks.
After following this thread one thing I can see that I don't like is that little lip shown in Tonys picture and pointed out in other post. Maybe Vans could offer all RV12 owners a special machined washer with a set bend on the bottom of the washer but even across the top where the nut would rest on it so that when the nut is tighten it would put equal pressure 360 degrees around the surface at that location.
A stepped washer would be difficult because Van's have no way of knowing what the step height is in each case. I have a step that looks very much like Tony's. I sent a photo and measurements to Vans and they suggested I file the area flat, but I've got no chance of doing that accurately by hand in such a confined space. The next best thing is probably a nice thick oversized washer or drilled packer and slightly longer bolts to spread the load over a bigger area.
Hi Tony T., good to hear from you,
Thanks for the info and picture. Yesterday I started my SB. The first thing I did to improve visibility in that area was get rid of that huge black conduit and wrap the wires in small spiral wrap. When I'm done I will just velcro that to the side of the channel to ease future removal and inspection of the area. Seems to me that black plastic conduit with its four adel clamps was a bit of overkill anyway for those few wires.
Next task ws to clean up the softened interior paint in the channel that resulted from the Decalin spill I had a while back. Messy job, but needed to be done anyway
Then I got a couple of the nuts off the outboard bolts without having to get underneath, and preliminarily I see no cracks. Next step is to get underneath to hold the bolts and get all the nuts off so I can clean up the area and inspect thoroughly.
I will also look at the idea of removing those skiins you mention. That sure would make life easier being able to get at the bolt heads. The last time I worked on those I ended up with a permanent kink in my arm!
More info later..............
John
Thanks for the info and picture. Yesterday I started my SB. The first thing I did to improve visibility in that area was get rid of that huge black conduit and wrap the wires in small spiral wrap. When I'm done I will just velcro that to the side of the channel to ease future removal and inspection of the area. Seems to me that black plastic conduit with its four adel clamps was a bit of overkill anyway for those few wires.
Next task ws to clean up the softened interior paint in the channel that resulted from the Decalin spill I had a while back. Messy job, but needed to be done anyway
Then I got a couple of the nuts off the outboard bolts without having to get underneath, and preliminarily I see no cracks. Next step is to get underneath to hold the bolts and get all the nuts off so I can clean up the area and inspect thoroughly.
I will also look at the idea of removing those skiins you mention. That sure would make life easier being able to get at the bolt heads. The last time I worked on those I ended up with a permanent kink in my arm!
More info later..............
John
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Jetguy
Well Known Member
I would think since Vans has the exact engineering specs on the main spar channel and I assume builds them in house with a precision milling machine each one should be exactly the same or extremely close so making the previously stated washer shouldn't be much of a problem.
Maybe Scott could chime in and explain how this piece is made.Although without first hand knowledge on this I maybe I wrong.
I totally agree that builders trying to sand this area flat would result in many uneven surfaces across the spectrum of RV12s. Not a good idea at all.
__________________
rgmwa[/QUOTE]
When I raised this with Vans they checked more than 20 channels in 2 batches in stock and none had steps, so I guess there might have been a setup error in some (perhaps many) of the earlier channels. I'm thinking of using an AN970 (large) washer under the standard washer, trimmed on three sides to fit the bottom of the cutout.
Jetguy
Well Known Member
Here is a thought!
Ok, they must have changed their machining process some where along the way. However I bet if they check their red factory built and Mitch Lockes Blue RV12 they could easily use those as a guide to make the machined washer for the earlier planes you are seeing on this thread. A simple email to all RV12 builders from Vans Records would let them know how many washers would be required. Or a request here for each owner who does the check to send them an email would work to.
Ok, they must have changed their machining process some where along the way. However I bet if they check their red factory built and Mitch Lockes Blue RV12 they could easily use those as a guide to make the machined washer for the earlier planes you are seeing on this thread. A simple email to all RV12 builders from Vans Records would let them know how many washers would be required. Or a request here for each owner who does the check to send them an email would work to.
"Problem"?
I wasn't posting a "problem", since I didn't find cracks. Apparently, at least within the load envelope I have operated the plane, there is enough bearing area under the washer. Not all my landings are rollers. I don't know how hard (crash) or rough (dirt/grass) landing it takes to crack the channel but I would guess pretty hard. I did post the picture off to Van's engineering to give them a data point.
The SB does not indicate to jack the plane for this work. In fact, the weight will have to be on the gear to remove the U-1202 bolts. I wondered what happened to my heavy stands, just kidding, my memory isn't that bad yet.
This could be done after lunch at Friday Harbor. I am sure Mr. Tea would loan tools and help.
Tony
I wasn't posting a "problem", since I didn't find cracks. Apparently, at least within the load envelope I have operated the plane, there is enough bearing area under the washer. Not all my landings are rollers. I don't know how hard (crash) or rough (dirt/grass) landing it takes to crack the channel but I would guess pretty hard. I did post the picture off to Van's engineering to give them a data point.
The SB does not indicate to jack the plane for this work. In fact, the weight will have to be on the gear to remove the U-1202 bolts. I wondered what happened to my heavy stands, just kidding, my memory isn't that bad yet.
This could be done after lunch at Friday Harbor. I am sure Mr. Tea would loan tools and help
.Tony
Found a very easy way to deal with the inspection without any broken nickles or bleeding hands. I located the two bolt heads that we have to reach,... ON THE BOTTOM OF THE AIRCRAFT!! I drilled four 3/4 inch holes in the skin, being sure to avoid getting to close to the rivet lines. With an open hole the bolt heads are easy to reach with a torque wrench, and when it is necessary to use the HAMMER via dowel to make sure the bolts are seated. After the inspection and re-tightening simply insert 4 metal hole covers found at your local hardware store, inspection complete in less than 2 hours. Good luck.Paul Johnson.
"I would think since Vans has the exact engineering specs on the main spar channel and I assume builds them in house with a precision milling machine each one should be exactly the same or extremely close..."
"Variation" is the enemy of Quality, and having a 'precision milling machine' or computer controlled numerical machine is no guarantee that sequential parts will be close to identical. Numerous variables enter into the equation, including bit condition, spindle condition, speeds and feeds, operator technique, etc etc.
The "problem" with the step (which may not be the "problem" at all with regard to the loose bolts and cracking in this thread, is that is a poor design situation any which way, which could lead to future problems, undefined at present. The fastener compression forces are not spread evenly around the circumference of the washer, and the lip can act as a stress-riser.
Even worse, close examination of your photo, Tony, reveals the hole itself penetrates the lip of the pocket - a situation just asking for crack formation at the two locations where the hole intersects the lip.
The solution is - assuming we discard the idea of in-situ grinding or filing down of the pocket - to fill the gap below the washer that constitutes the space between the surface of the U-channel chord and the bottom surface of the pocket. The difficulty is that this may be a variable distance between different parts due to the variability in the pocket machining process.
Also, the intersection between the chord and the web of the U-channel is not a step, but is radiused. At Boeing, we used to use small pieces called radius-fillers, but they would have been used in a situation where the hole was in the web and the radius filler meshed with the radius to the chord. In this case, what is needed would be a custom shim that matched the chord-web radius and had the thickness that exactly matched the mismatch dimension between the pocket and U-channel chord. Not an easy part to make.
This might be the desired solution - someone earlier mentioned Liquid Weld - that or some sort of structural epoxy that would allow a washer to be bedded in. Please note, however, that the curved sides of the pocket preclude use of a really large fender-type washer, without running into yet more radius problems in yet another plane.
In any event, seeing that hole penetrate that lip really gives me pause...
Bob Bogash
N737G
Airborne on Tony's sawhorses
Power on and Skyview functional since Monday 1 October!
"Variation" is the enemy of Quality, and having a 'precision milling machine' or computer controlled numerical machine is no guarantee that sequential parts will be close to identical. Numerous variables enter into the equation, including bit condition, spindle condition, speeds and feeds, operator technique, etc etc.
The "problem" with the step (which may not be the "problem" at all with regard to the loose bolts and cracking in this thread, is that is a poor design situation any which way, which could lead to future problems, undefined at present. The fastener compression forces are not spread evenly around the circumference of the washer, and the lip can act as a stress-riser.
Even worse, close examination of your photo, Tony, reveals the hole itself penetrates the lip of the pocket - a situation just asking for crack formation at the two locations where the hole intersects the lip.
The solution is - assuming we discard the idea of in-situ grinding or filing down of the pocket - to fill the gap below the washer that constitutes the space between the surface of the U-channel chord and the bottom surface of the pocket. The difficulty is that this may be a variable distance between different parts due to the variability in the pocket machining process.
Also, the intersection between the chord and the web of the U-channel is not a step, but is radiused. At Boeing, we used to use small pieces called radius-fillers, but they would have been used in a situation where the hole was in the web and the radius filler meshed with the radius to the chord. In this case, what is needed would be a custom shim that matched the chord-web radius and had the thickness that exactly matched the mismatch dimension between the pocket and U-channel chord. Not an easy part to make.
This might be the desired solution - someone earlier mentioned Liquid Weld - that or some sort of structural epoxy that would allow a washer to be bedded in. Please note, however, that the curved sides of the pocket preclude use of a really large fender-type washer, without running into yet more radius problems in yet another plane.
In any event, seeing that hole penetrate that lip really gives me pause...
Bob Bogash
N737G
Airborne on Tony's sawhorses
Power on and Skyview functional since Monday 1 October!
"Epoxy Grout", JB Weld or ?
JB Weld compressive allowable is 10,733 psi (don't know if this is yield or ultimate) per the link below. Does anyone know how to convert the prescribed torque values into the compressive load on a given sized washer? Also, what are the real risks of using a dremel tool with a sanding drum to level the lip in the channel -creating a low spot or worse?
http://www.homedepot.com/buy/j-b-weld-2-piece-cold-weld-epoxy-set-8265-s.html#.UG33gVFKWls
JB Weld compressive allowable is 10,733 psi (don't know if this is yield or ultimate) per the link below. Does anyone know how to convert the prescribed torque values into the compressive load on a given sized washer? Also, what are the real risks of using a dremel tool with a sanding drum to level the lip in the channel -creating a low spot or worse?
http://www.homedepot.com/buy/j-b-weld-2-piece-cold-weld-epoxy-set-8265-s.html#.UG33gVFKWls
Fixes...
At this point, any attempt to fix the "lip" would be a mistake. Best plan would be to proceed with the published SB and then to wait for the other shoe to drop...from Van's.
If it is deemed that the lip is a problem, there will be an engineered solution. One that comes to mind would be a machined steel bridge to span the rear to forward bolts and transfer the load to the center web of the channel away from the holes.
But wait, hush my mouth, I'm a dirt engineer...this is outside my pay grade.
Tony
At this point, any attempt to fix the "lip" would be a mistake. Best plan would be to proceed with the published SB and then to wait for the other shoe to drop...from Van's.
If it is deemed that the lip is a problem, there will be an engineered solution. One that comes to mind would be a machined steel bridge to span the rear to forward bolts and transfer the load to the center web of the channel away from the holes.
But wait, hush my mouth, I'm a dirt engineer...this is outside my pay grade
.Tony
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Van's Engineering Status Report
Please read the following update from Van's
http://www.vansaircraft.com/images/open/RV-12 landing gear update.pdf
The reason why the SB requires inspection for cracking before further flight and why aircraft are grounded that do have cracks is to prevent an aircraft from forming a crack of such magnitude as to completely fail the center section or have a crack propagate to such an extent as to make the center section not repairable. Both situations would require replacement of the entire center section assembly (including bulkheads which are precision reamed in assembly with the c-channel). So far all failures reported to Van's are repairable without replacement of the c-channel.
For those of you wanting to bond your channel back together I would not depend on it. Van's fix for the channel will no longer rely on the cracked area to transfer the load.
Please read the following update from Van's
http://www.vansaircraft.com/images/open/RV-12 landing gear update.pdf
The reason why the SB requires inspection for cracking before further flight and why aircraft are grounded that do have cracks is to prevent an aircraft from forming a crack of such magnitude as to completely fail the center section or have a crack propagate to such an extent as to make the center section not repairable. Both situations would require replacement of the entire center section assembly (including bulkheads which are precision reamed in assembly with the c-channel). So far all failures reported to Van's are repairable without replacement of the c-channel.
For those of you wanting to bond your channel back together I would not depend on it. Van's fix for the channel will no longer rely on the cracked area to transfer the load.
N712BK outer gear bolt washers
I have a single crack in each of the 2 forward outer bolt holes. It radiates forward to the front edge of the C-section. I sent Van's photos today of all 4 of my outer landing gear bolt holes which look like to me that the washers on all 4 holes only contacted the area that was machined out of the C-section. Hope this provides additional data on our gear problem. since none of us know what the "Root Cause" of the gear problem is we need to let Van's get to the root cause of the problem. As a retired Aerospace Engineer I have participated in several of these "Root Cause" investigations. it is not fun and it costs a lot of money. bottom line is that the fact that washers don't contact over there entire area may not make a "hill of beans" difference. I am as anxious as anyone else to have a fix and get airworthy. If this was a simple problem we would have a fix identified. since we don't have repair instructions I think we stand by and let Van's figure out the correct fix. you don't want to fix it twice.
Bob Kibby
I have a single crack in each of the 2 forward outer bolt holes. It radiates forward to the front edge of the C-section. I sent Van's photos today of all 4 of my outer landing gear bolt holes which look like to me that the washers on all 4 holes only contacted the area that was machined out of the C-section. Hope this provides additional data on our gear problem. since none of us know what the "Root Cause" of the gear problem is we need to let Van's get to the root cause of the problem. As a retired Aerospace Engineer I have participated in several of these "Root Cause" investigations. it is not fun and it costs a lot of money. bottom line is that the fact that washers don't contact over there entire area may not make a "hill of beans" difference. I am as anxious as anyone else to have a fix and get airworthy. If this was a simple problem we would have a fix identified. since we don't have repair instructions I think we stand by and let Van's figure out the correct fix. you don't want to fix it twice.
Bob Kibby
Low whistle........ think we've hooked a big one here, boys.
I don't think anyone wants to glue their cracked channels back together - or at least I hope not. If you're referring to the JB Weld, North Up, that would be to act as a solid shim filling the gap between the bottom of the pocket and the U-channel web on uncracked channels..
N/S DonFromTx - You took a certain amount of heat early on when you started this thread - stuff about unsubstantiated reporting, too melodramatic, sky is falling, exaggeration, etc. I'm here to say Thanks, Don - we all owe you a beer, and I'll buy you one personally if I ever get down there again.
Bob Bogash
N737G
JerryG150
Well Known Member
We have an addendum ...
SB 12-9-26 now has Addendum 10-3-12 as well as the RV-12 Landing Gear Upgrade Analysis
Addendum can be seen at end of SB 12-9-26, just click here ...
As I said before, "Once you're a builder, you're a builder for life" ... not my intention during my 3 year build, but it is what it is. I guess improvements and safety should and is Van's main concern ... as it should be, but ...
SB 12-9-26 now has Addendum 10-3-12 as well as the RV-12 Landing Gear Upgrade Analysis
Addendum can be seen at end of SB 12-9-26, just click here ...
As I said before, "Once you're a builder, you're a builder for life" ... not my intention during my 3 year build, but it is what it is. I guess improvements and safety should and is Van's main concern ... as it should be, but ...
DonFromTX
Well Known Member
txaviator
Well Known Member
Ditto, Don. You da' man. Thank you.
