Visby Class Corvette Case Study

World's First Truely Stealth Vessel Powered by TF™50a Gas Turbines

The world's first truly stealth vessel was recently launched powered by four TF™50A marine aeroderivative gas turbines in a Combined Diesel Or Gas (CODOG) turbine configuration. The Visby-class corvette, also known as the YS 2000 series, was designed and built by Kockums AB at the Karlskrona Shipyard in Sweden.

This flexible stealth vessel takes advantage of the TF50A's high power density, low vibration and noise characteristics and ease of maintenance attributes. The TF50A engines were selected for this project based on the long successful performance history of the TF™ Series engines in U.S. Navy service and for the operational flexibility afforded by the twin turbine per shaft line drive concept. The small size of the TF engines coupled with the cantilever mount from the combining gearbox provides a lightweight, compact propulsion package well suited to the Visby's design.

Vericor Power Systems provided the TF50A gas turbine propulsion module systems, which are combined with two MTU 16V 2000 N90 diesel engines to comprise the ship's main propulsion system. The TF50A gas turbines were manufactured for Vericor Power Systems by Honeywell Engines and Systems.

The TF50A gas turbines provide power for medium and high-speed operation, while the diesel engines offer low-speed maneuvering. The CODOG propulsion machinery provides power to two KaMeWa waterjet propulsors instead of conventional propellers. This arrangement provides for better hydro-acoustic signature, lower shipboard noise levels, better maneuverability, lower extreme draught, lower risk of damage and lower maintenance costs. Maximum speed is in excess of 35 knots.

The small size and light weight features of the TF50A allows for the installation of three to four times the horsepower over diesel engines for the same installed weight, and at a lower installed volume. In addition, the TF50A marine gas turbine system can drive a variety of propulsors including fixed and variable pitch propellers, waterjets and, in the case of hovercraft, air props.

The Visby concept was developed as a collaboration between the Defence Materiel Administration (FMV), the Royal Swedish Navy, the Swedish defense industry, the Swedish Defense Research Establishment and Stockholm's Royal Institute of Technology. Kockums AB currently has a total of six Visby-class corvettes on order. The Visby corvette is a flexible surface combatant, designed for a wide range of roles such as anti-surface warfare, anti-submarine warfare, mine counter measures, and patrol. The Visby is designed to minimize all signatures, such as optical and infrared signature, above water acoustic and hydro-acoustic signature, underwater electrical potential and magnetic signature, pressure signature, radar cross section and actively emitted signals. Commissioning of the second Visby corvette is slated for early 2002, with one ship to be commissioned every 12 months thereafter.