🔍 Key Concepts

• Effect of a single screw when the other screw is stopped on a twin-screw vessel • Transverse (sideways) thrust of a right-hand vs left-hand propeller when going ahead • Relationship between which screw is turning (port or starboard) and the direction of swing of the ship’s bow and stern

💭 Think About

• Visualize a twin-screw ship viewed from astern: which way does the starboard propeller turn when going ahead, and what side force does that create? • Think about which end of the ship (bow or stern) is most affected by transverse thrust when only one screw is working ahead. • If only the starboard engine is ahead and the port engine is stopped, which way will the stern tend to move, and therefore which way will the bow tend to swing?

✅ Before You Answer

• Determine whether the exam assumes conventional outward-turning screws (most common for license exam questions). • Confirm the direction of transverse thrust for a right-hand propeller going ahead (which way does the stern walk?). • Be sure you’re answering about the ship’s overall movement (what you’d see from above) rather than only the local flow near the propeller.