FFG-7 OLIVER HAZARD PERRY-class Propulsion

The engineering systems were new and innovative for their time. The unique gas turbine propulsion system can be brought "on line" and be ready to get underway in less than ten minutes, quite a difference from the four hours plus it took conventional steam powered ships.

While the previous KNOX-class ships were being designed and constructed, development was underway on employing the gas turbine engine used by air-craft for ship propulsion. The gas turbine or turbo-jet, or more simply jet engine, was developed on the eve of World War II for aircraft propulsion. In the first part of the gas turbine engine, air is compressed and drawn into a combustion chamber in which fuel is burned. From this combustion of air and fuel a steady stream of extremely hot gas that is expanding back through the second part of the gas turbine into the atmosphere in a high-velocity jet exhaust. Through a series of gears, the expanding exhaust is harnessed to turn the ship's propeller shaft.

Marine gas turbines have been successfully em-ployed in several merchant ships and in ships of destroyer and escort size in the U.S. Navy and Coast Guard and several foreign navies as well as several types of small craft. By the early 1970s, the U.S. Navy had a series of 164 and 1/2-foot gunboats at sea with gas turbine propulsion and the large SPRUANCE-class (DD-963) destroyers with gas turbine plants are under construction.

Gas turbines provide the advantages of quick start up from a shutdown or "cold iron" situation (whereas steam turbine ships must be generating steam to get underway), rapid acceleration once the ship is underway, relatively high speeds for the size of the propulsion plant, simple maintenance because of uncomplicated design of gas turbines, and comparatively simple replacement of the en-gines without having to place the ship in a dry dock.

The PF propulsion plant consists of two marine gas turbines, a modification of aircraft turbo-fan improvements were made when the plant was fan engines. This engine, designated LM2500, has a adapted to the KNOX class, resulting in increased demonstrated reliability, having been in service for automation and performance.

These engines also were used in the SPRUANCE-class destroyers. The PF propulsion plant will be half of the four-engine, two-propeller shaft plant of the SPRUANCE. With 30 destroyers planned in the SPRUANCE class, the combined requirement for gas turbines in these two ship types will be 220 engines. Thus, the large purchase of engines will help to hold down propulsion plant costs of both ships and permit similar personnel training, spare parts, and maintenance tools for both ships, resulting in additional cost-effectiveness.