The Cessna 120-140 Association Forum

My 46 c140 with later style front bulkhead(sn is post 8800) has a crack in what I believe is appropriately referred to as the stiffener-canted bulkhead-left. I’m looking for expertise in the repair of this or a reference to what is acceptable and what isn’t. There is an AD for pre 8800 bulkheads but, not for this type.

A closer depiction of the schematic location.

Was the airplane ever flipped over? That would be my guess as to how it got got there.

Mine had the same crack. I know mine had been on its back at least once and maybe twice.

They had been doing the AD inspection on the crack even though it did not apply to the airplane due to serial number.

Since I was so far into rebuilding the entire airplane I went ahead and replace the whole door post.

Good luck.

Rick

8342 wrote: ↑Mon Sep 13, 2021 6:38 pm Was the airplane ever flipped over?

I think it may have been David Lowe who said "If your plane has never been on its back, you're missing some of the paper work."

It’s been wind damaged and ground looped. Both of these events happened 60+ years ago. What no one can tell me is what I should do about it, if anything.

The only way to fix it is to change out the whole doorpost. If you look at how it is riveted together it would take very specialized equipment to replace just that piece.

I would just inspect it every annual and see if it gets worse.
As you mentioned the AD does not apply. Not only is the Serial number not applicable, the location of the crack is not where the AD says to look.

Rick

It's stop drilled, so it's been there for a while. Do the logs indicate when it ws first discovered?

It looks like the crack has propagated past the relief hole. Is that true? If so, it should be drilled again. Given that it is not static, you might want to inspect it more frequently than every annual, like before each flight.

The logs DON’T indicate when it was stop drilled. It was obviously done prior to paint in the late 90’s/early 2000’s. What we haven’t been able to determine is what the standards for cracks in this upper area are, or if a doubler can be added over the area concerned.

AD 47-06-11 allows cracks in the stiffners concerned with it to be upt to 3/4 inch.
That may be a starting point for reference.

Just spit balling.

Rick