Quote Originally Posted by Delta Whisky View Post
Drowosek - I'm curious as to what is wrong with 293mps? A quick look up says the speed of sound at 20C is 1235 km/hr (343 m/s). If my research and math is correct, tip speed would be about 85% sos. That's pretty much at the limit of efficiency for most propellers but it also isn't the cruise speed.
The point is that the translational velocity is added to the circumferential velocity. In addition, the velocity of local currents due to the streamline of the profile is always greater. Local compaction jumps appear, noise and power losses increase sharply. Therefore, the circumferential speed is usually limited to 220 m/s, 240 in extreme case. Of course, the saber-shaped blade shape partially mitigates the negative effects of the sweep.