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SIGNIFICANCE OF DIRECTION OF PROPELLER ROTATION IN COLLISION AVOIDANCE

A single-screw ship with a right-handed propeller will turn more readily to port than to starboard; the converse applies to a ship with a left-handed propeller. After listing data from sea trials on some East German ships to illustrate this difference in turning performance, and briefly discussing its causes, the Authors examine its significance in relation to the choice between a l.h. and a r.h. propeller. Most single-screw ships have a r.h. propeller and consequently have better turning characteristics to port than to starboard, but international rules for collision avoidance stipulate, for most potential-collision situations, a change of course to starboard. This apparent anomaly is discussed in the light of present-day conditions, both for navigation in the open sea and in confined waters, and several conclusions are drawn. The superior ability of a ship with a l.h. propeller to alter course to starboard increases in importance with increasing ship-size, particularly where there is heavy traffic. In going astern for collision avoidance, the r.h. fixed-pitch propeller has the advantage over the left-handed, but this advantage can be offset if the ship with the l.h. propeller has a bow thruster. Thus, with fixed-pitch propellers, the ship size, area of operation, and provision of auxiliary manoeuvring devices should all be taken into account when choosing the direction of rotation. These considerations are hardly relevant to the very large ships, which rely on tugs in pilotage waters and need one to three n. miles to stop from full ahead in emergency, but these vessels should, in principle, have l.h. propellers. R.h. propellers are suitable for small and medium-size ships that have no auxiliary manoeuvring device and operate extensively in pilotage waters. When there is a choice of direction of rotation for the c.p. propeller of a new ship, the l.p. propeller is generally preferred by ships' officers because it has the advantages of the l.h. fixed-pitch propeller when the ship is going ahead, and those of the r.h. fixed-pitch propeller when going astern.

  • Corporate Authors:

    VEB Autobahnbaukombinat

    Templinestrasse 19
    Potsdam,   Germany 
  • Authors:
    • Hahne, J
    • Hilgert, H
  • Publication Date: 1976-9

Media Info

  • Features: References;
  • Pagination: 2 p.
  • Serial:

Subject/Index Terms

Filing Info

  • Accession Number: 00149555
  • Record Type: Publication
  • Source Agency: British Ship Research Association
  • Files: TRIS
  • Created Date: Apr 13 1977 12:00AM