Props and chocs
We were doing engine runs on a rebuilt Stamp SV4 fitted with the Renault engine. This had an air starter with a little knob on the panel that you pulled out. This in turn had a little spring loaded lock, so both hands were required to operate it.
One of our junior mechs was in the seat and got ready to start, while I put the chocks in front of the wheels. With not much pressure in the cylinder, the knob needed to be pulled out over an inch before anything happened, but I had been running the engine just before, so the cylinder was fully charged. As soon as he moved the knob the engine turned, and fired, as he had the switches on.....The blade went through the hair on the back of my head (had more then..) Choice words followed about not taking anything for granted, and sticking to the rules.
DW