Vents are not installed in the direct impact slipstream, so
ice is not usually a problem in a well designed system.


"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.