Check out the picture on our web page of my friend that was holding an airplane from behind with a Magnum 1.80 on it. It was his plane and the firewall came out. The engine swung around when the throtle wire caught it. I do't have a picture of the guy that was in front. He had several stitches too.
I have a student who insist on being an individual. Some days I am positive he is just plain bone headed and other days I simply doubt his intelligence.
Sunday, he decided to do some radio trim work while he was kneeling in front of his unrestrained plane. Oh, yes it was running when he either bumped the throttle to wide open or hit the servo reverse switch. He only got chopped up just above the right knee.
Your friend looks worse.
I hope he mends with no long term ill effects
I feel badly because I have been able to teach my student safer methods. He knows that we WILL be changing his procedures or he will have to find another instructor (I am his 3rd or 4th and probably his last hope in my club).
One more reason to make sure when your setting up your throttle that pulling on the linkage closes the throttle. If your servo is set to push the linkage to close any looseness or engine mount, firewall breakage the throttle will be wide open. Always set it up so your servo pulls to close the throttle.