Years back, a local flight school had a Trinidad TB-20. The
owner of the flight school told me this story. A rental pilot
called him up during a flight and stated that his wings were collapsing.
The advice was to get the airplane on the ground as quickly as possible.
The cause was blockage of the fuel vent(s) from ice I believe, which
caused the deformamtion of the sheet metal sections of the wings where
the fuel tank(s) were located. It did quite a bit of damage to the wing.

Ronnie


"Peter" wrote in message
...
Is there any known case of the above happening, on an aircraft flying
below say FL200?

On a known-ice aircraft, the vents are normally heated.

One reads a fair number of stories of pilots picking up a huge amount
of ice (inches) but not (that I have seen) of engine failures caused
by vacuum in the tanks.