The Cessna 120-140 Association Forum

Just did a pre buy on a metallized with C-140. All well docuemented in logs and 337's from the 50's. I noted there are no inspection holes anythere. Do the rag wings have inspection holes?

Looked a some pics of a 140A wing, and didn't see any inspection holes either.

Comments?

I believe the idea was back on the day that fabric didn’t last long and of course with the fabric removed you can inspect everything in fine detail. Plus they likely thought the service life of the aircraft was 10 years or so.
I have metal wings, I installed several, I think 5 in total inspection holes in each wing.
Two schools of thought, one is to cut the hole and install a ring that reinforces the skin and the covers attach to the ring.
Second school is to just cut a hole as the skin isn’t really much of a stressed member and install the hole covers.
Covers can of course be the pop in type or the screw on type.

I used a hole saw to cut the holes, and installed screw on covers using the tinnerman clips you find all over the airplane. Takes maybe 5 min per cover or less.

In my opinion it’s a minor alteration if your an A&P.

Be sure to debur the holes so they don’t have sharp edges.

In my opinion you need to be able to see inside and with holes and a decent bore scope, you can see and inspect everything.

There are two issues. The first is the ability to inspect the inside of the wings. The second is an AD requiring inspection of the drag and anti-drag wire nuts. If the STC used to cover the wings does not allow for the wires to be removed then the AD still applies. If it does, you're back to the first issue.

There are other threads in this forum that discuss this in greater detail.

On the 140A there are very few what most call inspection holes. They are actually access holes to allow for installation of the strut attach bolt and nut, and to adjust components for the ailerons. Aside from the fuselage/wing fairing strip which gains access to the wing attach bolts, wiring, and fuel/vent lines there are only two (2) covers, one(1) in back of the wing strut attach point and one (1) in front of the aileron bell crank. Wings tips on the 140A are also removable, but aside from performing attention to a wing tip nav light all one can do from the tip end is use a flashlight to look at a few wing ribs.

As John said, this has been discussed previously in this thread:

viewtopic.php?f=7&t=983

I posted a 337 from 1954 on metalized wings. They had inspection holes on that 337. My plane eventually was restored back to fabric a few years after that with different original wings.

The discussion in that thread may be very helpful. Steve