A single-blade propeller may be used on aircraft to generate thrust. Normally propellers are multiblades but the simplicity of a single-blade propeller fits well on motorized gliders, because it permits the design of a smaller aperture of the glider fuselage for retraction of the powerplant. The counterbalanced teetering mono-blade propeller generates fewer vibrations than conventional multiblade configurations. Everel Propeller Corporation in the 1940s produced the counterbalance single-blade propeller.
See also 
Samara (fruit) single blade-like seed which autorotates in Nature.