Susumu Matsumoto

COUNTER-ROTATING PROPELLERS

A double reverse revolution propeller apparatus having a front (6) and a rear (7) propeller is disclosed, in which the rear propeller is rotated at higher speeds than the front propeller. In another aspect, when seizure occurs, an inner shaft (8) is disconnected from an engine at an inner shaft connection unit (10) and connected to an outer shaft at an inner and outer shaft connection unit to be driven in the same direction as the outer shaft. In still another aspect, the ratio in absorption horsepower of the front propeller to the rear propeller is set to be substantially equal to the ratio in rotational speed of the front propeller to the rear propeller. In a further aspect, one or both of the front and rear propellers include a variable pitch propeller. In a still further aspect, the front propeller has more blades than the rear propeller.