The basic function of a propeller is to convert engine power into thrust. The propeller works like a spinning wing, explains Boeing, pulling the plane forward in the same way a plane's wings give it lift, pulling it up.
A fixed-pitch propeller has a blade angle that is fixed. This means there is only one combination of rotational speed and airspeed at which the blade angle can work at its optimum to produce maximum thrust.
A pilot can adjust the rotational speed and blade angle of variable-pitch propeller so that maximum thrust can be produced under different conditions. This can result in faster takeoffs and climbs, as well as lower fuel consumption. This type of propeller is more complicated than a fixed-pitch propeller and requires more training to use.
