Sedan Wing Inspection Cover Installation

Aeronca Sedan Airplanes
bsafran
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Sedan Wing Inspection Cover Installation

Post by bsafran » Mon Jun 25, 2012 16:59

Sometime within the next year, all Aeronca 15AC Sedan owners will have to comply with the mandatory service bulletin and airworthiness directive directed at the wing spar caps. Owners will have to either cut inspection holes in both wings or drill small holes and boroscope the entire length of the spar. Ken Spires of Seville, OH (N1410H) is the only person I've heard of that has done the boroscope inspection and I am waiting to hear his story of what kind of process that entails.

Steve Hendryx of Mount Auburn, IA (N1028H) has made a small jig to assist in cutting the inspection holes and has posted a YouTube video showing how it works. I brought it to the Aeronca fly in so the Sedan owners could see it for themselves and decide if that was the route that was best for them.

John Craig of Ketchum, ID (N1159H) has made his own jig set up which involves more steps than Mr. Hendryx's system, but works just as well. Each gentleman has offered their jig kits to other Sedan owners to use to help comply with the AD.

To see Mr. Hendryx's unit and operation, please go to the link shown elsewhere in the Sedan section of this website. This topic thread is to show the alternative way of cutting these inspection holes using J.C.'s meathod. Granted, you could use the fly cutter we have been using for decades to cut circles into metal, but these jigs cut better holes and are easier to use.

One word of caution for those who choose to go the boroscope route. If there is no corrosion found, the small hole boroscope meathod is the fastest and cheapest way to go. However, it is when corrosion is found that a problem might pop up. They suggest placing the boroscope holes in the center of where the inspection plates are required so that if corrosion is found, the holes can be cut. It's just harder to cut these inspection openings once the boroscope hole is made because it eliminates the small center hole needed for the fly cutter or the two jigs.

This picture is of the jig fixture that Mr. Hendryx has made.
Attachments
Steve Hendryx Router Fixture Set.jpg
Steve Hendryx Router Fixture Set.jpg (127.03 KiB) Viewed 3174 times

bsafran
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Re: Sedan Wing Inspection Cover Installation

Post by bsafran » Mon Jun 25, 2012 17:10

The first picture shows the kit J.C. made to install the required inspection holes in his Sedan wings. The second picture shows the neat little measuring device he made to help locate where each hole goes. For some reason, the type certificate holder decided on very specific placement of the inspection rings and used tenths and hundreds of an inch measurements. J.C. went out and got a tape measure that was calibrated in tenths of an inch and included it in his kit. The most common measurement is 4.97 inches from the center of the spar and he got tired of looking at the small numbers. He made up a small plate with a hole on one end. Just place the hole overtop the rivet in the spar and it automatically measures down 4.97 inches. Great thinking J.C.!
Attachments
John Craig Router Fixture Set.jpg
John Craig Router Fixture Set.jpg (136.42 KiB) Viewed 3172 times
J.C.'s Custom 4.97 Inch Measuring Tool.jpg
J.C.'s Custom 4.97 Inch Measuring Tool.jpg (132.7 KiB) Viewed 3172 times

bsafran
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Re: Sedan Wing Inspection Cover Installation

Post by bsafran » Mon Jun 25, 2012 17:15

Step 1 is following the instructions on the service bulletin about placement of the inspection holes.

Step 2 is once the center position of each hole is determined, make a small indent in the wing skin with a center punch.

Step 3 is to drill a hole at that center punch mark using a # 40 drill.
Attachments
Step 1 - Measure Inspection Plate Placement.jpg
Step 1 - Measure Inspection Plate Placement.jpg (200.49 KiB) Viewed 3171 times
Step 2 - Center Punch the Center Mark.jpg
Step 2 - Center Punch the Center Mark.jpg (124.14 KiB) Viewed 3171 times
Step 3 - Drill Center With # 40 Drill.jpg
Step 3 - Drill Center With # 40 Drill.jpg (162.29 KiB) Viewed 3171 times

bsafran
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Re: Sedan Wing Inspection Cover Installation

Post by bsafran » Mon Jun 25, 2012 17:23

Step 4 is to match the unibit size to the center shaft of the router rig.

Step 5 is to tape the unibit as a guide to make sure you don't go too deep when drilling with the unibit.

Step 6 is to drill out the # 40 hole with the unibit down to where you taped it to show the proper depth. (or width I should say)
Attachments
Step 4 - Choose Unibit Drill Size.jpg
Step 4 - Choose Unibit Drill Size.jpg (147.27 KiB) Viewed 3171 times
Step 5 - Tape the Unibit.jpg
Step 5 - Tape the Unibit.jpg (138.5 KiB) Viewed 3171 times
Step 6 - Drill Center With Unibit.jpg
Step 6 - Drill Center With Unibit.jpg (162.22 KiB) Viewed 3171 times

bsafran
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Re: Sedan Wing Inspection Cover Installation

Post by bsafran » Mon Jun 25, 2012 17:34

Step 7 is to place the jig plate in place using a small bolt to align it in the hole you have just drilled. One side of the jig plate has a line drawn across it and a note to use that line to help align the plate parallel with the spar. Make sure that side of the plate is up and that the mark is indeed in line with the spar. While that alignment might not seem necessary, trust me, in certain cases it needs to be this way.

Step 8 is to drill the first of three holes using the # 40 drill. There are three lines on the jig plate to show which three holes to drill.

Step 9 is to cleco the jig plate where you have just drilled the rivet pilot hole.
Attachments
Step 7 - Secure Jig Plate With Bolt.jpg
Step 7 - Secure Jig Plate With Bolt.jpg (146.56 KiB) Viewed 3169 times
Step 8 - Drill First Rivet Hole With # 40 Drill.jpg
Step 8 - Drill First Rivet Hole With # 40 Drill.jpg (151.79 KiB) Viewed 3169 times
Step 9 - Cleco First Rivet Hole.jpg
Step 9 - Cleco First Rivet Hole.jpg (150.56 KiB) Viewed 3169 times

bsafran
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Re: Sedan Wing Inspection Cover Installation

Post by bsafran » Mon Jun 25, 2012 17:42

Step 10 - Drill the second rivet hole in the next marked hole using the same # 40 drill.

Step 11 - Cleco the second rivet hole.

Step 12 - Drill the third rivet hole in the last marked hole.
Attachments
Step 10 - Drill Second Rivet Hole With # 40 Drill.jpg
Step 10 - Drill Second Rivet Hole With # 40 Drill.jpg (157.28 KiB) Viewed 3169 times
Step 11 - Cleco Second Rivet Hole.jpg
Step 11 - Cleco Second Rivet Hole.jpg (168.58 KiB) Viewed 3169 times
Step 12 - Drill Third Rivet Hole With # 40 Drill.jpg
Step 12 - Drill Third Rivet Hole With # 40 Drill.jpg (154.62 KiB) Viewed 3169 times

bsafran
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Re: Sedan Wing Inspection Cover Installation

Post by bsafran » Mon Jun 25, 2012 17:59

Step 13 - Remove the jig plate. Take several of the reinforcement rings and cleco them in a small pile (whatever the cleco can hold) and this stack makes a nice drilling pattern for the # 30 drill. The stack helps you keep the drill straight. It also keeps you from using the other drill holes in the jig plate. If every Sedan owner drilled through the jig plate, it might get wallowed out enough to throw off the next user.

Step 14 - Drill all the remaining rivet holes in the ring. Now, reinstall the jig plate with clecos so we can set up to cut out the inspection hole.

Step 15 - The router should be locked into the correct width for an accurate cut to follow the curved grooves in the jig plate. This can be checked by putting the inspection plate template on the center pivot point and making sure the router bit matches the edge of the template.
Attachments
Step 13 - Remove Jig Plate and Cleco Several Reinforcement Rings in Place.jpg
Step 13 - Remove Jig Plate and Cleco Several Reinforcement Rings in Place.jpg (141.81 KiB) Viewed 3168 times
Step 14 - Drill Remaining Rivet Holes, Remove Clecoed Rings and Reinstall Jig PLate.jpg
Step 14 - Drill Remaining Rivet Holes, Remove Clecoed Rings and Reinstall Jig PLate.jpg (152.45 KiB) Viewed 3168 times
Step 15 - Check Router Pivot Width With Inspection Plate Template.jpg
Step 15 - Check Router Pivot Width With Inspection Plate Template.jpg (141.52 KiB) Viewed 3168 times

bsafran
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Re: Sedan Wing Inspection Cover Installation

Post by bsafran » Mon Jun 25, 2012 18:07

Step 16 - Insert the center guide rod of the router unit into the center hole of the jig plate and position the router bit into one of the three curved tracks for cutting the inspection hole.

Step 17 - Start cutting counter clockwise in the groove. Don't worry if the router unit bumps into the clecos. Just stop there and go on to the next curved groove. There will be plenty of room to finish the cut a few steps down the road.

Step 18 - Route all three curved paths.
Attachments
Step 16 - Insert Router Center Guide in Jig Plate and Position Router.jpg
Step 16 - Insert Router Center Guide in Jig Plate and Position Router.jpg (160.83 KiB) Viewed 3168 times
Step 17 - Start Router Cut - Counter Clockwise Works Best.jpg
Step 17 - Start Router Cut - Counter Clockwise Works Best.jpg (167.76 KiB) Viewed 3168 times
Step 18 - Route All Three Paths in Jig Plate.jpg
Step 18 - Route All Three Paths in Jig Plate.jpg (154.59 KiB) Viewed 3168 times

bsafran
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Re: Sedan Wing Inspection Cover Installation

Post by bsafran » Mon Jun 25, 2012 18:13

Step 19 - Remove the jig plate.

Step 20 - Rotate the jig plate so that it is easy to finish routing the remaining wing skin material. Cleco the jig plate to the wing and finish routing the rest of the connecting wing skin.

Step 21 - Remove the jig plate, the wing skin circle and then vacuum the wing interior to remove all the debris from the drilling and routing.
Attachments
Step 19 - Remove Jig Plate.jpg
Step 19 - Remove Jig Plate.jpg (148.32 KiB) Viewed 3167 times
Step 20 - Rotate and Reinstall Jig Plate to Route Remaing Wing Skin Material.jpg
Step 20 - Rotate and Reinstall Jig Plate to Route Remaing Wing Skin Material.jpg (155.07 KiB) Viewed 3167 times
Step 21 - Remove Jig Plate, Wing Skin Circle and Vacuum Wing Interior.jpg
Step 21 - Remove Jig Plate, Wing Skin Circle and Vacuum Wing Interior.jpg (139.64 KiB) Viewed 3167 times

bsafran
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Re: Sedan Wing Inspection Cover Installation

Post by bsafran » Mon Jun 25, 2012 18:28

Step 22 - Redrill the rivet holes with a # 30 drill to accept the rivets. Deburr the rivet holes and sand the cut area of the inspection hole.

The next steps are just basic riveting of the reinforcement plate in place. You can slide most of them in place by snaking them through different bays of the wing. Those areas where this is not possible, you can follow the type certificate's advice and remove rivets here and there to slide the rings where they need to be. The easiest way is to cut the ring so it can be curled inside the hole you just cut. That requires a few more rivets and a doubler plate and J.C.'s jig plate helps you if you go that route.

It is scary to poke holes in a wing that was designed to not have holes. It just isn't all that hard. What is difficult is to gather up all the metal crumbs you create when cutting into the metal and to introduce the corrosion retardant called for in the AD. Make sure your wings are painted the color you want before you spray in the corrosion fog. This stuff will leak out through every crack and make paint adhesion nearly impossible.
Attachments
Step 22 - Expand all Rivet Holes With # 30 Drill, Deburr and Sand All Edges.jpg
Step 22 - Expand all Rivet Holes With # 30 Drill, Deburr and Sand All Edges.jpg (139.64 KiB) Viewed 3167 times

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joea
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Re: Sedan Wing Inspection Cover Installation

Post by joea » Tue Jun 26, 2012 04:09

Brian,

Very good pictorial of this process.

I met with JC and Brian last week in Middletown and they went through their process shown above and glad to see that they have worked this up for those who could not make it to the fly-in.

It takes a lot of the hassle and guesswork out of making inspection covers in our wings.

Personally I am going to put at least 4-5 of the covers in each of my wings to just make things easier and use the AMOC (alternative means of compliance) method and a bore-scope.

Thanks guys!

Joe A

Carl Prather
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Re: Sedan Wing Inspection Cover Installation

Post by Carl Prather » Tue Jun 26, 2012 21:49

Guys,

Assuming one could reach into the wing, do you a think using a proper size chassis punch would be good alternative to fly cutting?

Carl Prather

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Matt
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Re: Sedan Wing Inspection Cover Installation

Post by Matt » Thu Jun 28, 2012 01:38

A fantastic tutorial. Now I REALLY understand what JC explained to me in words at Middletown.
Thank you so much to both of you, JC and Brian, for your genius and the effort to post this here in words and pictures for all of us!

Matt
Aeronca 15AC Sedan – Restoring and flying the classic 4-seater: http://www.n1331h.com

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Re: Sedan Wing Inspection Cover Installation

Post by pmanton » Thu Jun 28, 2012 08:44

How big are these holes? I've done numerous inspection openings using a large hole saw ( 3 1/2 & 4 inches)

Paul
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bsafran
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Re: Sedan Wing Inspection Cover Installation

Post by bsafran » Tue Jul 03, 2012 07:41

I have looked at many sets of Sedan wings over the years and am surprised at how different some are from the others. I have found stiffeners installed, either at the factory or during a repair, that aren't depicted on the blueprints. I had a couple of situations where I carefully plotted out exactly where the inspection holes are supposed to go and that spot fell on top of a rib or stiffener. Burl advises to just move the hole to the best nearby location where you can completely fit the doubler between the stiffeners and ribs and still have the observation area of the spar (the whole reason for installing these plates in the first place).

The first picture shows a cut out portion of a Sedan main spar so everyone can get an idea of where this corrosion problem is. You can see that the spar is made up of three different pieces, the main web and the top and bottom caps. This intergranular corrosion hides in the very edges of the spar caps and explodes it out in layers.

The second and third pictures show the corrosion found in the wings I just cut the inspection holes in for this website topic. While corrosion is evident, this is not the intergranular damage everyone is worried about. The edges of these caps are just fine. This corrosion most likely started when the owner chemically stripped the paint off the wings several years ago and never neutralized the stripping material. It has laid underneath the wing skin and over time has attacked the unprotected spar cap. This corrosion is the kind you can clean off without having to replace the entire spar cap. However, to do a complete job, the wing skin should be removed so that the top of the cap can be accessed for cleaning. This is not a fun job, but at least you don't have to buy any expensive cap replacements.
Attachments
Main Spar Section.jpg
Main Spar Section.jpg (168.03 KiB) Viewed 3037 times
Surface Corrosion on Main Spar Cap .jpg
Surface Corrosion on Main Spar Cap .jpg (99.08 KiB) Viewed 3037 times
Surface Corrosion on Main Spar Cap 2.jpg
Surface Corrosion on Main Spar Cap 2.jpg (89.54 KiB) Viewed 3037 times

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