What impact do fixed speed, variable pitch propellers have at low thrust?

Fixed speed, variable pitch propellers are designed to allow adjustments to the blade angle while maintaining a constant rotational speed. At low thrust settings, these propellers often struggle to maintain efficiency because the propeller design is optimized for higher thrust and operational speed.

As the propeller operates at lower thrust, it can experience a decrease in performance, resulting in a situation where it may lose up to thirty percent of full thruster power. This reduction is primarily due to the hydrodynamic effects encountered at lower speeds, where the angle of attack may cause a loss in lift and overall thrust. Consequently, the propeller may not be able to deliver the expected thrust, thereby leading to notable power losses.

This phenomenon highlights the limitations of fixed speed, variable pitch propellers in low-thrust scenarios, illustrating how their operating characteristics influence efficiency and overall effectiveness.