The Pratt & Whitney J75 (civilian designation: JT4A) is an

axial-flow An axial compressor is a gas compressor that can continuously pressurize gases. It is a rotating, airfoil-based compressor in which the gas or working fluid principally flows parallel to the axis of rotation, or axially. This differs from othe ...

turbojet The turbojet is an airbreathing jet engine which is typically used in aircraft. It consists of a gas turbine with a propelling nozzle. The gas turbine has an air inlet which includes inlet guide vanes, a compressor, a combustion chamber, and ...

engine first flown in 1955. A two-spool design in the 17,000 lbf (76 kN) thrust class, the J75 was essentially the bigger brother of the

Pratt & Whitney J57 The Pratt & Whitney J57 (company designation: JT3C) is an axial-flow turbojet engine developed by Pratt & Whitney in the early 1950s. The J57 (first run January 1950) was the first 10,000 lbf (45 kN) thrust class engine in the United States ...

(JT3C). It was known in civilian service as the JT4A, and in a variety of stationary roles as the GG4 and FT4.

Design and development

In military use, the J75 was used on the

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Lockheed U-2 The Lockheed U-2, nicknamed "''Dragon Lady''", is an American single-jet engine, high altitude reconnaissance aircraft operated by the United States Air Force (USAF) and previously flown by the Central Intelligence Agency (CIA). It provides day ...

, and

Republic F-105 Thunderchief The Republic F-105 Thunderchief is an American supersonic fighter-bomber that served with the United States Air Force from 1958 to 1984. Capable of Mach 2, it conducted the majority of strike bombing missions during the early years of the Vie ...

. It was also utilized in the prototype and experimental

Avro Canada CF-105 Arrow The Avro Canada CF-105 Arrow was a delta-winged interceptor aircraft designed and built by Avro Canada. The CF-105 held the promise of Mach 2 speeds at altitudes exceeding and was intended to serve as the Royal Canadian Air Force's (RCAF) ...

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Martin P6M SeaMaster The Martin P6M SeaMaster, built by the Glenn L. Martin Company, was a 1950s strategic bomber flying boat for the United States Navy that almost entered service; production aircraft were built and Navy crews were undergoing operational trainin ...

, North American YF-107, and

Vought XF8U-3 Crusader III The Vought XF8U-3 Crusader III was an aircraft developed by Chance Vought as a successor to the successful Vought F-8 Crusader program and as a competitor to the McDonnell Douglas F-4 Phantom II.Tillman 1990 Though based in spirit on the F8U-1 a ...

. Before the arrival of the

Pratt & Whitney JT3D The Pratt & Whitney JT3D is an early turbofan aircraft engine derived from the Pratt & Whitney J57, Pratt & Whitney JT3C. It was first run in 1958 and was first flown in 1959 under a B-45 Tornado test aircraft. Over 8,000 JT3Ds were produced bet ...

turbofan The turbofan or fanjet is a type of airbreathing jet engine that is widely used in aircraft engine, aircraft propulsion. The word "turbofan" is a portmanteau of "turbine" and "fan": the ''turbo'' portion refers to a gas turbine engine which ac ...

engine, the JT4A was used to power certain

Boeing 707 The Boeing 707 is an American, long-range, narrow-body airliner, the first jetliner developed and produced by Boeing Commercial Airplanes. Developed from the Boeing 367-80 prototype first flown in 1954, the initial first flew on December 20, ...

and

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models, bringing improved field performance in the medium-range Boeing 707-220 and Douglas DC-8-20, and intercontinental range in the Boeing 707-320 and the Douglas DC-8-30. By late 1959, P&W had considered introducing a turbofan version of the J75, which was to have tentatively been named the TF75 or JT4D. Apparently, little interest was shown by the aircraft industry, so the variant was dropped.

Marine & power generation

After its relatively short lifetime in the aircraft role, the JT4A found more enduring use in the naval role, where the FT4 was produced in a variety of models between . Well-known uses include the first all-turbine warships, the Canadian s, as well as the United States Coast Guard's s, the 1970s-built icebreakers ''Polar Sea'' and ''Polar Star'' (each 3 engines in

CODOG Combined diesel or gas (CODOG) is a type of propulsion system for ships that need a maximum speed that is considerably faster than their cruise speed, particularly warships like modern frigates or corvettes. For every propeller shaft there is o ...

configuration), and it was considered for the US Navy's . The same basic powerplant saw much wider use as a

peak demand Peak demand on an electrical grid is simply the highest electrical power demand that has occurred over a specified time period (Gönen 2008). Peak demand is typically characterized as annual, daily or seasonal and has the unit of power. Peak dem ...

power turbine running on

natural gas Natural gas (also called fossil gas or simply gas) is a naturally occurring mixture of gaseous hydrocarbons consisting primarily of methane in addition to various smaller amounts of other higher alkanes. Low levels of trace gases like carbo ...

. From its introduction in 1960 over 1,000 FT4s have been sold, with many of them still in operation for electrical generation. Outdated by modern standards, refits are available that add

catalytic converter A catalytic converter is an exhaust emission control device that converts toxic gases and pollutants in exhaust gas from an internal combustion engine into less-toxic pollutants by catalyzing a redox reaction. Catalytic converters are usually ...

s to lower their emissions.

Variants

;J75-P-1: ;J75-P-3: thrust ;J75-P-5: thrust ;J75-P-9: ;J75-P-11: ;J75-P-13B: thrust ;J75-P-15W: afterburning thrust ;J75-P-17: afterburning thrust ;J75-P-19: afterburning thrust ;J75-P-19W: afterburning thrust with water injection ;JT4A-3: ;JT4A-4: ;JT4A-9: ;JT4A-11: thrust ;JT4A-29: (J75-P-19W) afterburning thrust with water injection

Applications

;J75 * Avro Canada CF-105 Mk1 Arrow *

North American F-107 The North American F-107 is North American Aviation's entry in a United States Air Force tactical fighter-bomber design competition of the 1950s. The F-107 was based on the F-100 Super Sabre, but included many innovations and radical design fea ...

;JT4A *

(specifically, the 707-220 and 707-320) *

(specifically, the DC-8-20 and DC-8-30)

Specifications (JT4A-11)

Notes

References

External links

Pratt & Whitney J75/JT4 webpage
{{DEFAULTSORT:Pratt and Whitney J75 J75 1950s turbojet engines