Twin-screw steamer

A twin-screw steamer (or steamship) (TSS) is a steam-powered vessel propelled by two screw propellers, one on either side of the plane of the keel.^[1]

Arrangement

All propellers produce a transverse thrust, also called screwing effect or starting bias, which gives a tendency for end of ship to move sideways. In a twin-screw ships the port propeller is usually left-handed and the starboard right-handed, to cancel out the transverse thrust and avoid propeller walk.^[2]

References

1. "Maritime Acronyms and Abbreviations". Royal Institution of Naval Architects. TSS. Archived from the original on 19 August 2016.
2. Danton, Graham (31 October 1996). "The Principles of Ship Handling". The Theory and Practice of Seamanship. Routledge. pp. 51–55. ISBN 978-0415153720.