I did that Aviation Medican Course at Upwood in about 1962 or 63, when I was a Lightning Simulator instructor...I remember we trained for about a week for that explosive decompression...For the training we were strapped into a disarmed bangseat in a classroom and we wore the kit but were pressure fed just neat air. All the stuff inflated and we had to learn to breath against the pressure.
Quite difficult really as in normal breathing the body makes a slight effort with diaphragm etc to INHALE and just relaxes to EXHALE...When you have air or oxygen being fed into your mask with the toggle down to stop leaks, if you RELAX just slightly, a gale rushes into your nose and mouth and inflates your chest to its maximum...Then you have to strain to EXHALE it by blowing strongly to get all that air out again...Slight relax...Gale up nose...Blow strongly and so on and on.
It is quite amusing and slightly frightening as you wait your turn watching the guy in the seat...The pressure comes on and he turns down the mask toggle...His pressure vest and G-suit are inflated, but there is nothing around his neck! His neck inflates out sideways like some sort of bullfrog!
On the big day you pre-breath 100% oxygen for about and hour before carrying your portable supply with you down to the decompression chamber...You have already been wired up with electrodes and as you enter the chamber and strap into the seat, the Doc plugs in all his wires so that he can monitor your physical state from outside.
The chamber is closed and up it goes slowly to about 24,000 feet...You are then given a warning that it is imminent and that your first action must be to turn down that toggle...You are also asked to keep replying to a "Thumbs Up" query with a similar gesture if all is well...You sit and wait...
BANG!...a frightening bloody great bang and the place fills with vapour and you are now at 56,000 feet...Wrestle the toggle down...feel the pressure coming in start to PRESSURE BREATH...just as you have been doing in training all week...stay calm BLOW...slight relax...GALE up nose BLOOOOOW....Thumbs up to doc through the window...BLOOOW! They bring you fairly quickly back down to sea level and you climb out with some relief.
Well, that is the end of the course really and you can go off back to base
