Sorry for the stupid question, but how on earth is this possible? Can't
you tell if you're upside down or not? Or is it like being deep
underwater?

If you're in cloud, you can't see out. When flying, you can generate g
forces (by turning, banking, climbing, etc) which can fool you into
thinking that "down" is in any direction. So, it's quite easy to not
know where up and down are. I suppose it's like being deep underwater,
but for different reasons.

This is one of the first things one must learn in instrument flying -
trust the instruments over your inner ear. They are less likely to be
lying to you.

Jose
--
"Never trust anything that can think for itself, if you can't see where
it keeps its brain." (chapter 10 of book 3 - Harry Potter).
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