It doesn't always work. I had a case on a GP Giant stick this summer where it turned out the servo tray was not glued in properly. I had gone over it like all my planes with ca on all the structural stuff but did not do the servo tray. So I was up flying and next thing I know it is stuck at full throttle. Every time I moved the throttle the tray would move not the throttle on the engine. So I flew it around to a location I knew I could make a safe dead stick and hit the engine kill. With out it I would have had to fly it full throttle until it ran out of fuel. I always install some type of secondary engine kill for those unexpected occasions. A little extra safety never hurts. Normally I don't use it, I just shut it off with the engine cut off on my tx.