center section repair

In anticipation of the by now assigned AD regarding the Center section of our beloved Ercoupes, I took the wings off this winter and had a closer look. First I washed the center area with high pressure air and solvent for an hour - the gunk of over fifty years had to come out.

I found some surface corrosion on all parts where previous primer applications did not reach. Nothing major. It just needs a cleanup and prime and done. Then I found what we all are afraid of, something which looked like corrosion on the inboard spar of the trailing edge on the right side of the center section. It is hard to see, because one has to look through two lightening holes, with the wings detached, And even then you can see just a fraction of the rib. I had my mechanics look at it and after discussing several methods of remedy we decided to open up the lower skin. This is what I found.

Location of corroded rib

closer ...

As one can see, the Alclad is separated

The other side of the rib

See how the layers of aluminum peel off

These ribs are hard to get out because they are also riveted into the web which supports the walkway.

Finally I got it out.

The area around the lightening hole was just like paper. The rib fell apart by removal

Only the area close to the trailing edge was still intact.

To my surprise was the cancer restricted just to this rib. The rear spar was not affected at all, after clean up appeared just fine.

These ribs can be reached and looked at from the inside of the plane through a lightening hole behind the rear spar.

To get your head there you would have to remove all baggage compartment floorboards, seats etc. But it is possible either with a mirror or a scope to reach down there and have a look. One could even test the structural integrity with a hammer or so.

I recommend doing so, because if you let the cancer proceed, the rear spar might get affected, which will be an expensive fix.

Here the area after cleaning and priming

Ready for the new rib.

This last picture shows the rib all riveted in place

My mechanic did the last steps without me, so no pictures of that process. The last picture was done through the lightning holes of the fuselage from inside of the baggage compartment. Hartmut