Univair Service Bulletin LPC-1 (1995)

[Jim]

If you've ever received a notice from Univair about installing additional gussets in your 22/20 gear legs, do it. If you're not sure if your plane is in compliance, it's definitely time for a look under there to make sure.

http://www.shortwingpipers.org/forum/attachment.php?attachmentid=9141&stc=1http://www.shortwingpipers.org/forum/attachment.php?attachmentid=9142&stc=1

[Steve Pierce]

Ouch. :shock: I have the service bulletin at the shop. I will post it. Actually a library of these type of documents is my next project here. My Pacer had the gussets added. They look terrible. :x I am about to change bungees and intend to replace the gussets at that time.

[taildraggerpilot]

Just a note of interest:

If anyone who has a pacer or a conversion who's gussets are missing (not installed) can simply call Univair and they will supply you with the parts and instructions FREE. I was suprised by this as nothing, especially from Univiar, is free. The gussets are now on my gear as well.

[Jim]

Hi again,

Univair really stepped up when I had my problem with their product. I originally purchased the legs from them in 1983 and didn't have a problem until 21 years later. They more or less agreed that the wording in their SB LPC-1 about using your plane on "unimproved runways or skis" didn't relay the real possibility of gear collapse, just mentioned "improved serviceability".

They did agree that they should re-issue a notice to owners as it's been a bunch of years and there were quite a few at Oshkosh without the upgrade.

Univair offered up a free gear replacement/repair on whatever I sent them. They also offered any parts I may need, at their costs, to get things fixed, strut, step, prop, bolts, exhaust, whatever. I doubt you'll find another aircraft part house that'll stand behind a part they provided 20+ years prior.

Luckily my 0290 was a tad over TBO so there wasn't much of a loss there. I then bought a runout dynafocal mounted 0320 E2D from a 76 Cessna thinking I'd just get the dynafocal mount pictured in our parts books. Turns out Piper never had a dynafocal in these short wingers, just a ring beefed up conical. Well anyway, that leads into another can of worms story better left for later.

[smcnutt]

You can find both the Univair Service Buletin (PDF) in the column marked "Restoration / Rebuild" and pictures (Univair Landing Gear Mod JPG) in the column marked "STC's / Alterations / Repairs" on page 2 of Andy's site http://home.earthlink.net/~flynrow/id1.html

I actually just did this update last weekend when we replaced the bungees. We pulled both gear off and it only took about 30 minutes to do the welding. When you look at the gear priot to the update you have to wonder what Unvair was thinking when they originally made the gear. I'm no engineer (but I stayed at a Holiday Inn Express once :roll: ) but without the added gusset I thought the gear looked extremely weak and unsupported. Now that I've seen that, I'm REALLY glad we did the fix.

If the pictures of Jim's plane :shock: aren't enough motivation to do the update, crawl up under your landing gear where it attaches to the bungees and tell me that looks strong enough with only a gussett on one side tubing.[attachment=1:2v7oipkz]1204071302a.jpg[/attachment:2v7oipkz]

[BatPacer]

I could call around to Pacer owners I know here in Alaska and ask them to bring their collapsed gear to a central location and it would make quite a tangled pile. The gussets called out in the service bulletin are a must but to really strengthen the gear, they should be supersized top and bottom. The gussets alone don't do a thing toward preventing a streamline tube collapse, though. This tube won't take a serious side load unless it is tied to the rear member of the attachment triangle (see photos). There are some that would argue that "something is going to bend" if the load gets too severe and that if it isn't the gear it will be the longerons and beyond. Well, I think Jim's pictures pretty well sum up the end point of an arguement like that!

Paul[attachment=1:2jzvyh0r]Pacer Gear mod 2.jpg[/attachment:2jzvyh0r]

[Steve Pierce]

Thanks for the pictures Paul. I always thouht the reinforcement went to the front tube. I now see it goes to the back.

[Steve Pierce]

Here is the bulletin.

[mmoyle]

My PA20 had these gussets..... Failed due to improper welding technique.http://images.tapatalk-cdn.com/15/10/19/05f9c986a71d00e3e96838cf8dd52ad3.jpghttp://images.tapatalk-cdn.com/15/10/19/8a7400d6c7b2301fd706be537b05d369.jpg


Sent from my iPad using Tapatalk

[Steve Pierce]

Looks like it ripped the base metal of the tube out. I don't really see those gussets failing a gear. Clipper and stock Pacer gear did not have those gussets. What was the circumstance and what does the rest of the gear look like?

[Jim]

Hi again,

.....Looks like it ripped the base metal of the tube out.

The gusset on the right should have been welded more oriented along the edge of the streamlined tube. On my original Univair legs the gusset on the left was just welded along one of its edges allowing it to flex the joint and break out of the tube. I'm sort of happy mine didn't break the wing in half too.

[Steve Pierce]

I went and looked at several gear and I think I see what you are saying Jim. They did not weld the gusset at the edge of the doubler but in the middle of the tube on the picture Mark posted.
http://www.shortwingpipers.org/forum/attachment.php?attachmentid=9146&stc=1

http://www.shortwingpipers.org/forum/attachment.php?attachmentid=9147&stc=1

http://www.shortwingpipers.org/forum/attachment.php?attachmentid=9148&stc=1

[mmoyle]

My gussets were different compared to the pictures Steve posted. If you enlarge my pic you'll see only the edge of the weld bead was welded to the tube. The bulk of the bead was laid on the tube, wasn't hot enough to melt the tube the at the gusset..


Sent from my iPad using Tapatalk

[mmoyle]

http://images.tapatalk-cdn.com/15/10/20/36231e224068cf4bc18fb520cdf43b0d.jpghttp://images.tapatalk-cdn.com/15/10/20/76bb969b83e39c0ca73056a8addfba73.jpg


Sent from my iPad using Tapatalk

[Jim]

Hi guys,

By the pictures you've both posted, it seems to boil down to minimal workmanship as delivered and/or produced. I don't think people look where the problems originate until it's too late.

[mmoyle]

A friend of my took his Husky in for annual.....different A&P from his usual. The mechanic...an old codger wanted to strip the paint from the landing gear. Arne's like why...other than chipped paint they look great. Due to cracks....wish I had pics....Arne is now sporting new gear legs.... Maybe it's a Husky thing?..... I do know this.....most of the super cubs out here have safety cables..... I'll probably be adding more drag......too.


Sent from my iPad using Tapatalk

[mmoyle]

Looks like it ripped the base metal of the tube out. I don't really see those gussets failing a gear. Clipper and stock Pacer gear did not have those gussets. What was the circumstance and what does the rest of the gear look like?

Old and cracked all to H...E..double L. Accident waiting to happen.http://images.tapatalk-cdn.com/15/10/20/aac4d2c307f0459380ca91f2b0f56a43.jpghttp://images.tapatalk-cdn.com/15/10/20/6c7b466b1ae6c23a0e8f6bc823a8f1f3.jpghttp://images.tapatalk-cdn.com/15/10/20/7c481f378b4e4c6f58556a441407e57a.jpghttp://images.tapatalk-cdn.com/15/10/20/093c608c927bafe6b8ca67e2cecc008a.jpghttp://images.tapatalk-cdn.com/15/10/20/a6206ef05cfcc1ad18571bf618f6b142.jpg
http://images.tapatalk-cdn.com/15/10/20/ceccdfe249f7597cfcc42c5679afaced.jpg


Sent from my iPad using Tapatalk

[mmoyle]

This gear leg was sand blasted, painted and recovered just before I arrived in Arkansas to pick it up. The cracks were missed, perhaps due to the sand blasting moving the metal at the surface. I had bought a used motor mount for my rebuild. Sandblasted it....looked really good... After the very first light coat of epoxy primer I discovered a crack.... Bought a new engine mount. I've tried to get a die penitrant magnuflux kit shipped to Platinum.....can't get the vendors to ship the kit from the lower 48 to Alaska... When I rebuild my next airplane.... Will try to get a kit..... Like buy it in person when the bride and I make a trip to Osh, Copper state....or some other event...


Sent from my iPad using Tapatalk

[Jim]

Hi again,

Found a couple of more pictures showing how mine came apart. http://www.shortwingpipers.org/forum/attachment.php?attachmentid=9149&stc=1http://www.shortwingpipers.org/forum/attachment.php?attachmentid=9150&stc=1Easy to see how it was only welded on one side of the gusset. It was the welded side that cracked the tube where I found the rust.

The gusset pretty much just pealed out of there, just a tad of rust where the crack started some time back. http://www.shortwingpipers.org/forum/attachment.php?attachmentid=9151&stc=1When it all hit flat on the ground it also broke both tubes that went over to the gear hinge.

I'm hoping bringing this thread out of the past will find a plane or two that won't go through all this. Such a waste of effort and expense for not fixing the problem.

[tim bandy]

somewhere (here?) I have seen a gear strengthening mod where some short strips of steel are added to the
upper corners of the gear legs. (as diagonals I think-)
Cant remember which kind of piper it was (16,18 20,22) -----

Is this an STC's mod (I dont remember seeing it in any STC lists) ---- or is this just a field approved mod
for planes expected to see rough use (?)

just curious where I could read more details on this mod----

Tim

[Steve Pierce]

The Light Planes Components (Univair) landing gear. Merged your thread with one on the subject with good pictures.

[tim bandy]

Thank you Steve----
BatPacer seemed to indicate that he did his gussets a bit bigger than spec-- and it looks like he added a pic to his post but all I see is the string under the post--- no pic. Can you see a pic there or just a line of code ?

[Steve Pierce]

That picture was of the ski tube between the rear gear tube and the streamline tube as pictured in this thread. Lost in the software upgrade years ago.
https://www.shortwingpipers.org/forum/showthread.php?7292-Landing-Gear-Strength-and-Beef-Ups/page2

[tim bandy]

Steve--- thinking about those univair small gussets-----
Like to run this by your sanity meter----

Looks like Univair's narrow strips may not have enough surface area at the welds----
what if I was to take some tubing sized so that it that would telescope on the gear leg--- cut off a section about 6 inches long--
take that tube and cut it down the sides so I now have a saddle that could go 40% around the circumphrence of the gear leg----- weld the brace part to the manufactured "saddle piece" --- then weld the outer edge of the saddle to the gear leg. Then do something like this on both ends of the gusset. Seems like this would drastically increase the weld area on the gear leg. seems like it would also give much more support in compression because of the large area saddle. The gusset could be a bit thicker than stock to equal the added strength of the saddle.

I guess this would be equivalent to welding on a scab to the tubes before the gusset was added.

Do you think this would be less likely to tear out of the tubing like one of the poster's showed his doing ?

Tim

[Steve Pierce]

I have seen no issue with what Univair shows in the bulletin. The gear I see bent is bent in the middle of the streamline tube from a groundloop. The ski-tube is installed there because of the side loads imposed on skis.

[tim bandy]

Thanks Steve---- I went out and looked at mine--- it DOES have the gussets from factory---- but the tabs are only welded on one side and the beads do not go past the end of the tab. Since I will have the gear off in the near future--- should I weld them also on the OTHER side of the tab and on the ends ? ( so the welds go 360 around the tab ?)

This is the fail pic I was thinking of ref the previous post----
http://www.shortwingpipers.org/forum/attachment.php?attachmentid=9149&stc=1
he mentioned that some rust may have started the problem. Looks like it ripped out at the HAZ. This is why I wondered if more weld bead might help lower the stress on it.

Tim

[Jim]

Hi Tim,

That picture you posted is the original, single gusset, that tore out. The Univair fix installs a second gusset which ties in the second round tube as well. It's been a while, but I seem to recall their fix also does some bridge building with additional welds. If you ever see a leg with a single gusset there's a real good chance something bad is lining up for the owner.

[Marc Davis]

Hey, Jim. Thanks for reviving this from time to time. I just looked at my gear, no gussets. That's now next on the todo list. Also adding the "ski tube" and maybe a fuel step too.

[mmoyle]

Welding tip. One of the things that got drilled into every fabricator/welder’s brain at RAHCO was.......wrap your welds.


Sent from my iPad using Tapatalk Pro

[Jim]

Hi,

I've never heard the term, weld wrapping. Sure seems like more of that common sense I've missed over the years.

http://www.google.com/search?q=Wrap+your+welds&source=hp&oq=Wrap+your+welds&gs_l=mobile-heirloom-hp.3..0i333.15052.22286.0.25283.16.11.0.5.5.0.294. 1697.0j10j1.11.0....0...1c.1j4.34.mobile-heirloom-hp..1.15.1793.1pmBf0GQKRI