Ref the ejection seat test rig, when I went through training we all had to have a go. It was mounted on a Queen Mary trailer and the seat travelled up a ramp. I believe it was a one-third charge (one cartridge instead of three?). The idea was strap in (tight), pull the face blind and bingo, there you were some fifteen feet up the ramp. A couple of months after I left South Cerney, one chap was using it when they had a misfire. While it was being sorted out, he loosened his straps and leant forward. The cartridge went off, and damaged his back such that his flying days were over.