Installing the Inspection Covers

August 1, 2010

The kit comes from Avipro with the inspection holes cut into the wing bottom and also comes with the pre-cut inspection covers and rings.

The cover and ring are pre-drilled with one hole in each corner to help you get the alignment correct.

Note: I didn't have the proper size cleco for the factory made alignment holes, so I just used a couple of screws/nuts for alignment.

There are 3 sizes; a large one for the aileron bellcrank area, a small one for the hole in front of the spar near where the wing strut attachment is, and the rest are all medium size.

Start by drawing a line on the inspection cover ring connecting the four holes. Figure out what screw spacing you want and lay out the hole locations on the line. I put on hole in the center of each narrow end and two holes along each long edge. Drill the holes with a #40 bit:

These will eventually be screws and anchor nuts.

Now lay out a rivet line exactly 1/4" in from the outside perimeter of the inspection cover ring as shown here. Drill these holes with a #40 bit as well:

I used 1 1/8" spacing for these holes.

Now to locate the inspection ring perfectly centered in the wing inspection hole.  Cleco the inspection cover on the bottom side of the inspection ring. Then simply place the ring and cover in the hole making sure that the cover is centered in the wing inspection hole. Note: you may need to file the edges of the cover and/or the hole in the wing for a proper fit:

Double check that the cover is in the wing inspection hole, drill and cleco the inspection ring to the hole. Note: Be careful to not push down too hard while drilling these holes. There is no support rib underneath and in pushing down you might deform the wing skin downward while drilling. This may cause the inspection hole area to be a low spot in the wing instead of level with the surrounding skin. Just let the drill do the work and cut the hole.

With all of the holes drilled, mark the ring, the cover, and wing skin so you will be able to reinstall them later in the same orientation.

Now you can take it apart and put the inspection ring under the skin and cleco it in place:

Now test fit the cover in the hole to make sure the holes line up properly:

I found that I had to lightly file the edges of the inspection cover and the hole in the wing to make them fit together correctly.

Now we'll remove the ring and install the anchor nuts using the same techniques that we used on the fuel tank bay cover.

After installing the anchor nuts, the outside row of rivet holes were deburred and dimpled:

The holes in the wing skin were also deburred and dimpled.  The ring was then clecoed and riveted in place using a squeezer:

Note:  Don't push down too hard while squeezing these rivets. Since there is no supporting rib and this skin is fairly thin at .020", if you push down too hard while squeezing these rivets it will result in a dip (low spot) in the wing skin at the inspection hole location. To get nice flat inspection holes, press down just hard enough to keep the rivet seated in the dimpled hole and squeeze the rivet.

One hint for you, make sure to mark each inspection ring and cover for location and direction.

My coding indicates this is inspection cover #2 for the right wing and the arrow always points toward the leading edge of the wing.  When you do your annual inspections and all of the inspection covers are sitting on the work table in a big pile, you will need to know where each one goes and its orientation.

For now, the inspection covers are just lightly screwed in place with 4 screws:

Now I'll do the rest of them.

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