What type of propulsor is typically used in electric motor driven, transverse, tunnel bow thrusters to limit the starting current of the single speed drive motor?

Correct Answer: Option D — Controllable-pitch propeller

Controllable-pitch propellers allow the drive motor to start under a no-load or low-load condition by setting the blades to zero pitch. This prevents the high starting current spikes associated with fixed-pitch propellers, which would otherwise require significantly larger, more expensive electrical switchgear and motor starters.