F.L. Whiteley writes
I was first introduced to the push-over at altitude while being checked
out for winch launch at RAF Bicester. It's a useful exercise for
experiencing the amount of push over required and to see the amount of
dirt and dust that might float up from the floor. It can be alarming
the first time and ignored subsequently.

On a slightly light-hearted note, I consider the chance to throw all the
dust and junk that accumulates on the cockpit floor up the nose of the
instructor behind me to be a petty but quite fitting vengeance for his
having pulled the plug on a perfectly good launch in the first case for
the sake of drill

--
Bill Gribble
http://www.scapegoatsanon.demon.co.uk
- Learn from the mistakes of others.
- You won't live long enough to make all of them yourself.