Tanker Built In Spain First To Use New Litton Navigation System

The Carthago Nova, a 272,000- dwt tanker launched August 7, 1976 in Spain at the Astilleros y Talleres del Noroeste, S.A., shipyard for Empresa Nacional del Petroleo, S.A., will be the first vessel to use a new Litton Industries' microprocessor-based Integrated Navigation and Steering Control Systems.

Designated the Litton INAS- 2000, the new system was developed by the Automated Marine Systems Division of Litton Systems (Canada) Limited. Presently being installed in Hull 241 (Carthago Nova), the system is the first of five Litton Integrated Navigation Systems scheduled for installation in Spanish ships within the next year.

The Litton INAS-2000 accepts the output of a combination of navigation receivers (such as NNSS satellite, Omega, Loran-C, Decca or Hi Fix), and processes their output signals with data from the gyrocompass and the ship's speed log. The computer processed navigation information is automatically integrated with required course data or voyage plan entered by the navigation officer. The INAS-2000 will continuously compute either a great circle or loxodromic course between waypoints compensating for sea currents and wind. Final heading commands are fed into a digital autopilot, which holds the ship precisely to that course. The rate-of-turn of the ship is continuously monitored by a precision rate-of-turn gyroscope. The necessary corrections for the effect of sea state, draft changes and depth of water below the keel on the ship's maneuvering dynamics are made in order to provide the required steering control with minimum rudder motion.

By keeping the vessel at the corrected course heading with minimum deviation, the Litton INAS-2000 reduces distance traveled hence travel time and required fuel. Use of the rate-ofturn gyrocompass and compensation for the factors that result in reduced rudder operation not only extends the life of the rudder gear, but also markedly reduces the power required to overcome rudder drag in holding constant cruise speed. The energy saving from both these functions can be substantial, with a projected saving of 3 to 6 percent of annual fuel costs for VLCCs, LNG carriers and fast containerships. Of particular importance, at a time of high concern about oil spills, is the increased safety associated with the use of the Litton INAS-2000. The system processes the best information available from the ship's navigation sensors, and performs continuous validation to protect against false signals. The use of a computer system reduces the possibility of human error arising from stress and fatigue of round-the-clock manual operations. For free literature on the Litton INAS-2000 System, write P. Broadhurst, Litton Industries (Canada) Ltd., 25 Cityview Drive, Rexdale, Ontario, Canada.

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