Juice,
Like racer said, in RC you decrease the diameter when increasing the pitch to keep the same RPM. In full scale, cruise RPM is lower than climb or takeoff RPM. So when you increase pitch the engine slows down. This is desirable and is the same thing that would happen in rc if you increased pitch while maintaining diamater.
In the King air (and other PT6 powered airplanes) we have a much larger range of engine operating options than in the direct drive turboprops mentioned. The prop, reduction gearing, and power turbines are not attached to the engine. Hence the "free turbine" designation. Engine operation is independant of prop operation. You can hold the prop during engine start and run the engine with the prop stationary. We have a full range of engine speeds available from 52% (idle) to 101.5%. If I remember correctly 101.5% is 38,100RPM. On takeoff, the prop reaches 2000rpm (red line) around 1000-1200 ft-lbs of torque. (Torque is just like MAP on a piston) So that is how much power it takes to turn the prop 2000rpm at its finest normal pitch. As power is increased to the 2230 ft-lb max the prop increases pitch to absorb the extra power to maintain rpm. I have a picture taken in flight of the prop pitch. This was probably around 20,000ft cruising around 270 TAS with the prop RPM at 1700rpm and engine power around 1800 ft-lbs. I was shocked how much pitch is on the prop, although I just worked it out to a pitch of 193". I don't know if that is is correct or not but it is impressive.