First Service Bulletin: SB 14-11-03

Announced recently by Van's Aircraft Company was a Service Bulletin, No. 14-11-03, requiring RV-12 owners to inspect certain wing rivets for signs of wear.  Apparently the demo plane at the factory in Oregon started showing signs that rivets were starting to wear in the wing root area, and so Van's decided that the safe course of action was for the whole RV-12 fleet to be inspected.  If signs of wear are found, then a skin-to-spar doubler is called for to beef up the area, and that's expected to take an hour and a half per wing to install by a qualified airframe mechanic.  Of course you don't have to install the doubler if there's no sign of wear; the plane will probably fly hundreds of hours just fine without showing any of the symptoms described in the SB, it's just that it's relatively easy to do now, cheap (~$20, w/shipping) and installing the doublers will likely prevent future rivet wear problems by making the wing stronger overall.  So I ordered the parts from Vans and got to work removing rivets where doubler plates are to be added at the wing root on the bottom side of the wing.

I didn't get any photos of yours truly removing rivets so I can't show any, but here's one of the bits and pieces of pop-rivets that were drilled out placed next to SB Figure 1, which shows the orientation and location of the doubler.

Step one in removing a pop-rivet is to knock out the leftover piece of mandrel through the bottom of the rivet with a suitably sized punch.  That's the little bits on the right side of the tray picture below.

Step two is to use a 1/8" drill bit to very lightly drill off just the manufactured head of the rivet.  That's the washer-looking thingys in the bottom of the red tray in the picture to the right.

Step three is to push out the shop-formed side of the rivet with a couple taps on a slightly larger punch, shown in the upper left of the tray.

There's 21 pop-rivets to drill out on each wing, and each piece, except the heads, had to be found and removed from inside the wing by reaching through the rib lightening holes and feeling around 'til I found it.  I got most of 'em but unfortunately a couple of the tiny mandrel pieces didn't want to be found.

Once the rivets are removed the SB calls for you to cleco on the doubler and match-drill 42 holes into the bottom wing skin using the doubler as a template, and enlarge 8 existing holes to accept the larger and stronger 5/32" pop-rivets.

As always, appreciation goes to my beautiful wife for taking photos for this blog, buddies who help move the wing from the ceiling to the workbench and back, and for every neighbor who steps up the driveway when the garage is open to ask "Howzitgoin?".

Appreciation also goes to Mr. B for the extended loan of his airplane building tools.  When he loaned me his tools two and a half years ago, included in one of the parts trays was a tiny little ziplock baggy of #30 high-speed "jobber" drill bits, the size used for LP4-3 pop rivet holes.  I almost can't believe they've lasted this long, but they're still cutting just fine so I keep using 'em.  Here's a couple pics of the drilled out holes:

After removing the doubler, clearing away chips and cuttings, deburring holes, and vacuuming out the inside of the wing, the SB has us "chamfer" the edges of the doubler.  I thought the word was "bevel", but what do I know?  Mr. B's belt sander (below) accomplished that task quite nicely.  I think the bevel angle is supposed to be about 45°, but I tried to aim for something closer to 60°, but lightly rounded at the edge.  You don't want a metal edge you can cut paper (or fingers) with.

With the prep work done all that's left is to rivet on the doubler, right?  There's just one little problem.  Can you see it in the picture?

        No?  How about now?

The rivet mandrel for the larger 5/32" rivets broke off above ("proud") of the rivet head.  Which means they had to be filed down flush with the top of the rivet head, which is not fun.  How did that happen?

I think what happened is Van's sent the wrong length of rivets.  SB Figure 6 calls for using "BSPQ-5-2" rivets (also known as "oops" rivets in certain unfortunate contexts), but Van's sent BSPQ-5-4 rivets, according to the parts list.

As you can see there are eight 5/32" rivets for each doubler (the rest are "regular" size)
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Builders take note:  The way you want to do this (having learned the hard way) is, counting from inboard 1, 2, 3, ... 8, do rivet #8 first, before any other rivets.  If the mandrel sits proud of the head, file it down.  Then do #7, then #6, and so on, working your way back to the wing root end.  Take care not to scratch the doubler with the file while you're doing it.  That's the tricky part.

Or you could be smart and just get the correct 5-2 rivets to start with.

After filing down the 5/32" rivets the rest was easy.

Here's the doubler installed on the bottom of the left wing:

And here's the right wing hanging from the ceiling again so I could use the bench for the other wing.  My first SB!

Recall that I said that Van's SB says that installing the doubler should only take 1.5 hours per wing?  It took me about three times longer than that.