I was an Instrument Fitter at RAF Feltwell and we were often detailed to go up on the first flight after a major service. The theory being that we would work carefully knowing that one of us would be detailed for the flight. One day it was my turn and I climbed into the right seat of a dual control aircraft which had parachutes built into the seats.
The sergeant tucked a sick-bag into my tunic even though I told him I was never air-sick and I waited with oxygen mask and headphones on for the pilot to arrive. He came and we roared off down the runway to climb up to about 10,000 ft where he turned the a/c upside down and told me to collect all the toffee papers and other bits of rubbish which dropped into the canopy.
He then had to make some performance notes and asked me to hold the stick and keep it straight and level before he then took control and dived the a/c to start a loop during which I blacked out. I told him about this and he said I hadn't blacked out, it was simply my eyeballs being forced down and blocking vision, and I was to look upwards at the start of the next loop which I then saw all the way over.
He continued to do stall turns, barrel rolls, wing overs, and I remember seeing the fields of East Anglia spinning below as we did a spiral dive. By this time I was feeling slightly queasy but luckily we landed and I did not need to use the sick-bag.
It was worth doing National Service just to have had a flight like that ....