I CDUK... You could look up some stats on Lycoming engines, and find out that in aviation use they are practically rev limited for safety purposes, and to ensure a long life. The Red-Line is set at 2800 rpm.
If you were to install one in a car, then you could most likely rev it to 4000+rpm where the power would peak to a maximum. So in aviation use you are in the situation where the power always increases as the revs rise to the arbitrary Red-line figure.
A fixed bladed prop needs power proportional to the square of its speed, because as revs rise... More air is passed backwards. That air is moved back quicker. (~ M.V ). The intersection of the power available (straight) line, and power required (curved) line, will give the rpm for that particular engine/prop configuration.
A constant speed prop is just mechanically governed to keep the engine speed constant. In a loop for instance... When climbing upwards it sets a low pitch, and when diving it sets the coarse pitch.
Last edited by phiggsbroadband; 24th Jul 2014 at 15:27.
Reason: get the formula right Phi...