[psychobob]

One of the main problems about getting piston engine planes to these kind of speeds was the propeller, whose rotating tips went supersonic well before the airspeed of the plane and tended to break apart.

I was at the Tillamook, Oregon air museum reading about the propellers on the B-50's. I don't remember the exact words, but it was something to the effect that they had to figure out how to make them big enough to handle the huge horsepower, but shaped just right because the tips moved beyond the speed of sound.