| FT4 | |
|---|---|
| Type | Gas turbine |
| National origin | United States |
| Manufacturer | Pratt & Whitney |
| First run | 1962 |
| Number built | 1,000+ |
| Developed from | Pratt & Whitney J75 |
ThePratt & Whitney FT4 is an aero-derivativegas turbine engine developed from thePratt & Whitney J75/JT4 turbojet line.[1][2] Development of FT4 began in 1961 at the request of theBureau of Ships for a lightweight, high power engine forhydrofoils,[3] whose great speed opened new possibilities for small craft.[4] The FT4 was run for the first time late in 1962, after which it was delivered to theUnited States Navy for testing.
In 1965,STAL-LAVAL placed an order for the FT4's gas generator for use with a self-designed turbine and housing for installation on thePeder Skram-class frigates of theRoyal Danish Navy.[5] The same year, theUS Coast Guard picked the FT4 for use on theHamilton-class cutters. Both classes made use of aCODOG powerplant arrangement, retaining the propulsion diesel engines that had been used on their predecessors. The first application of the engine on its own would occur in 1967, when a pair of the type were installed inGTS Admiral W. M. Callaghan as a testbed for the all-gas turbine powerplant at sea. However, the engines had severe reliability problems and were replaced with an equal number ofGeneral Electric LM2500s in 1969.[6] Around this time,Pratt & Whitney suffered a major blow whenLitton's LM2500 powered design won the contract for US Navy's newSpruance-class destroyers.[7] However, they did secure a contract with theRoyal Canadian Navy to use the systems on theIroquois-class destroyers.[8] The engine would go on to be used on the US Coast Guard'sPolar-class icebreakers. The US Navy's FT9 engine combined the high pressure compressor and turbine of thePratt & Whitney JT9D-70 with the housing, low pressure compressor, power turbine, and numerous other components of the preexisting FT4C-1.[9]
The FT4 gained its first commercial customer very early on, withDelaware Power & Light installing a set as apeaker plant inWilmington, Delaware in 1963.[10] The set found itself very well suited to power generation due to its containerized and rugged design that had been mandated by the US Navy, and was picked up by numerouspower companies throughout the 1960s and 1970s, selling over 1,000 units and accumulating over 5 million hours of operation by June 30, 1976.[10]
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