Question 59 ONC03 - Master LT 500-1600 GRT

The Correct Answer is C **Why option C is correct:** A tunnel bow thruster is designed to provide a lateral (sideways) thrust to move the bow of the vessel to port or starboard. Because the thrust is directed horizontally across the vessel's beam, it generally provides this lateral control without creating significant forward or backward movement (headway or sternway). Its primary function is low-speed maneuvering, specifically docking and undocking. **Why the other options are incorrect:** * **A) It is fully effective at speeds up to about six knots:** Bow thrusters lose significant effectiveness rapidly as the vessel increases speed due to the water flowing past the hull, which reduces the pressure differential needed for the thruster to work efficiently. They are designed for use at very low or zero speed, typically becoming ineffective above three or four knots, and are certainly not "fully effective" up to six knots. * **B) It will allow you to hold a position when the current is from astern:** A bow thruster only provides lateral thrust (sideways movement of the bow). It has no capability to hold the vessel against a current from astern, which requires longitudinal thrust (forward power), typically provided by the main propulsion. * **D) It can be used to slow the ship in addition to backing down:** Bow thrusters provide only lateral thrust, not longitudinal thrust (forward/aft). They cannot be used to slow or stop the ship; that function is reserved for the main engine reversing (backing down) or using specialized braking systems.