A variable pitch propeller is one in which the pilot is able to adjust the blade pitch during flight. The blade angle can thus be adjusted to its optimum value for the phase of flight, be it takeoff, climb or cruise. In some installations, it is possible to feather the propeller. For a variable pitch propeller, the pilot controls the blade pitch with the propeller control. However, the propeller RPM will vary, in the same fashion as a fixed pitch propeller, as a function of engine RPM or of airspeed. A more sophisticated variant of the variable pitch propeller is the constant speed propeller which, while in flight, will maintain the same RPM irrespective of throttle lever movement or airspeed.