Not an engine failure but I had to do an autorotation for real (Twice)
First time in an R22 with a clucth actuator failure, Id just taken off and smelt burning and thought I had a fire so I proceded to land on a taxi way as I came to a hover I had a power loss and performed a hovering auto (The burning smell was from the oil which had driped onto the engine from the clucth actuator) Lesson learned keep an open mind to what the problem is.
Second time flying past a big radio antenna at about 1000ft the signal from the antenna rolled the governor down and the throttle to about 85%, I entered auto and the RPM recovered so I went back into powered flight and the governor rolled the throttle down again, This time I entered auto and landed. Heard some nice traditional Dutch music over the headsets this time which is a bit unusual when you have an emergency.
Now when ever flying past a radio antenna I always turn off the governor till Im a good distance away.