USCG Exam PracticeTwin-screw vessel handling
The largest single contributor to propeller side force on a conventional shaft-driven vessel is which of the following?
- ✓ Unequal blade thrust caused by differing effective pitch angles of ascending and descending bladesCorrect
- B. The discharge screw current acting on the rudder blade
- C. The frictional wake layer dragged along the hull
- D. Aeration of the blade at the top of its arc
Why A is correct
§10-A identifies the angle of the propeller shaft as the largest contribution to side force: the descending blade has a higher effective pitch and produces more thrust than the ascending blade, making blade thrust unequal around the arc and pushing the stern to one side.