How often did wing-folding mechanisms fail in flight?

[Big Jake]

From the pictures I saw of the recovered wreckage of the Hudson's helicopter, it doesn't seem as if the rotor separated from the fuselage.

All naval aircraft with folding wings have mechanisms incorporating interlocking pins and hooks in such a way that ensures security of the wing attachment. The wing fold locking mechanism is usually accompanied by the aileron control interconnect that doesn't work if the wing is not locked. Once engaged, a mechanical indicator shows the pilot that the wing is locked. He should also operate the ailerons to make sure that they operate correctly. If he fails to pay attention, he would wind up taking off with an unlocked wing, ruining the rest of his day. I never heard of a locking mechanism failing, causing the wing to fold. Anyone?

 

[MiTasol]

There is absolutely no reason not to make them stronger (apart from obvious cost and weight reasons)

As D don4331 said - making any area stronger means a stress concentration. That causes the surrounding structure to fail because the loads are transferred to them.

One of the LEAP mods on the Lockheed L188 Electra was to remove certain structural elements in the wing to fuselage joint area because they were too strong.

 

[MiTasol]

From the pictures I saw of the recovered wreckage of the Hudson's helicopter, it doesn't seem as if the rotor separated from the fuselage.

All naval aircraft with folding wings have mechanisms incorporating interlocking pins and hooks in such a way that ensures security of the wing attachment. The wing fold locking mechanism is usually accompanied by the aileron control interconnect that doesn't work if the wing is not locked. Once engaged, a mechanical indicator shows the pilot that the wing is locked. He should also operate the ailerons to make sure that they operate correctly. If he fails to pay attention, he would wind up taking off with an unlocked wing, ruining the rest of his day. I never heard of a locking mechanism failing, causing the wing to fold. Anyone?

That F4U photo shows that it could happen. My sole experience with folding wing aircraft was with the TBF and TBM Avengers. They had a klaxon behind the pilots head that squawked at you unless the wings were fully locked or fully folded. NOT pleasant.

 

[MIflyer]

I recall reading of an incident where a drunk pilot got in an A-1 and tried to take off with the wings folded. I guess that was deliberate; he claimed it would fly like that.

And then there was a famous incident where an F-8 took off with the wings folded. They can't be seen from the cockpit and the pilot was unaware. They called him on the radio and told him to come back very carefully and he made it down Okay.

Never heard of one failing in flight. The original design of the F8F had the wingtips blow off in the event the wing was being overstressed, but I don't think it was anywhere near the wing fold joint.