PURPOSE:To prevent the generation of a high stress caused by a composite bending and tortional stress of the blades by connecting the outer edge parts of the propeller blades and the propeller boss with auxiliaryblades of a wing-shaped cross section. CONSTITUTION:The rear edges near the respective outer edges A of the propeller blades 11a-11e are connected to a propeller boss 3 by corresponding auxiliary blades 14a-14e. Each auxiliary blade has a cross section the same with that of a normal propeller blade. Thus application of a high stress to the rear edge of the blade is prevented, since the lift around the outer edges of the blades is produced by the auxiliary blades 14a-14e as well as by the propeller blades 11a-11e.
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