Question 322General Subjects - Assistant Engineer

The correct answer is B) Controllable-pitch propeller. A controllable-pitch propeller allows the pitch of the propeller blades to be adjusted, which enables the propeller to maintain unidirectional shaft rotation regardless of the direction of thrust required. This makes it the optimal propulsor type for unidirectional propulsion shafting. The other options are not suitable for unidirectional shafting. A fixed-pitch propeller (A) can only provide thrust in one direction. Tandem propellers (C) and detachable-blade propellers (D) do not inherently allow for unidirectional shaft rotation.