What is prop pitch speed?

I get my pitch speed estimates from MotoCalc, which I highly recommend. Pitch speed is the velocity of the air coming out the back of the prop while at full throttle while the motor is static on the ground. It's useful because it provides a rough measure of top speed capability. For example, with the Himax 2015-4100 and 9x6 prop in my Hornet, the pitch speed is 49 mph and the calculated top speed is 51 mph. Pretty close. The reason top speed is a little bit higher is because the prop unloads some at speed.

[Steve, F18 thread]