Pratt & Whitney TF30 / JTF10A
SNECMA / Pratt & Whitney TF106
SNECMA / Pratt & Whitney TF306
The Pratt & Whitney TF30 (company designation JTF10A) was a military low-bypass turbofan engine originally designed by Pratt & Whitney for the subsonic F6D Missileer missile carrier, but this project was cancelled. It was later adapted with an afterburner for supersonic designs, and in this form it was the world's first production afterburning turbofan, going on to power the F-111 and the F-14A Tomcat, as well seeing use in early versions of the A-7 Corsair II without an afterburner. First flight of the TF30 was in 1964 and production continued until 1986.
In the 1958, the Douglas Aircraft Company proposed a short-range, four-engined jet airliner to fill the gap below its new DC-8 intercontinental; it was known internally as the Model 2067, and to be marketed as a four engine DC-9 which was later developed in a scaled down 2 engine DC-9 using the same engines due to emerging market demands. Pratt & Whitney (P&W) had offered its JT8A turbojet for the airliner, but Douglas preferred to go with a turbofan engine, which would have a greater fuel efficiency than a turbojet. P&W then proposed the JT10A, a half-scale version of its newly developed JT8D turbofan. Development of the new design began in April 1959, using the core of the JT8. Douglas shelved the model 2067 design in 1960, as the targeted US airlines preferred the newly offered Boeing 727.
In 1960, the United States Navy selected the JT10A, designated TF30-P-1, to power the proposed Douglas F6D Missileer, but the projected was canceled in April 1961. Meanwhile, the TF30 had been chosen by General Dynamics for its entrant in the TFX competition for the United States Air Force and USN, which was selected for production as the F-111. The version of the TF30 for the F-111 included an afterburner.
The F-111A/E used the TF30-P-103 (aka P-3) turbofan. The F-111 had problems with inlet compatibility, and many faulted the placement of the intakes behind the disturbed air of the wing. Newer F-111 variants incorporated improved intake designs and most variants featured more powerful versions of the TF30 engine. The F-111E used TF30-P-3 engines, the F-111D included TF30-P-9, and the F-111F had the TF30-P-100.
In 1964, the subsonic LTV A-7A Corsair II won the US Navy's VAL competition for a light attack aircraft to replace the Douglas A-4 Skyhawk. The A-7A used a non-afterburning variant of the TF30, which would also power the improved A-7B and A-7C. In 1965, the USAF selected the A-7D as a replacement for its fast-jet F-100 and F-105 supersonic fighter-bombers. Though the USAF had wanted the TF30, Pratt & Whitney was unable to meet the production timetable because its facilities were already committed to producing other engines. Instead of producing the TF30 under license for P&W, the Allison Engine Company offered its own TF41 turbofan, a license-built version of the RB.168-25R Spey, to the AIr Force. The more powerful TF41 was selected by the USAF for the A-7D, and by the USN for its similar A-7E.
The Grumman F-14 Tomcat with the TF30 was underpowered, because it was the Navy's intent to procure a jet fighter with a thrust-to-weight ratio (in clean configuration) of unity or better (the US Air Force had the same goals for the F-15 Eagle and F-16 Fighting Falcon). The F-14A's thrust-to-weight ratio was similar to the F-4 Phantom II; however the new fuselage and wing design provided greater lift and a better climb profile than the F-4. The TF30 was found to be ill-adapted to the demands of air combat, and was prone to compressor stalls at high angle of attack if the throttles were moved aggressively. Because of the Tomcats' widely spaced engine nacelles, compressor stalls at high AOA were especially dangerous because they tended to produce asymmetric thrust that could send the Tomcat into an upright or inverted spin, from which recovery was very difficult.
The F-14's problems did not afflict TF30 engines in the F-111 to nearly the same extent, because that airplane was used as a strike aircraft. This type of mission is characterized by discrete phases so less abrupt changes in throttle, angle of attack and altitude are required. Though the F-14A entered service with the Navy powered by Pratt & Whitney TF30, by the end of the decade, following numerous problems with the original engine, the Department of Defense began procuring F110-GE-400 engines and installed them in the F-14A Plus (later redesignated to F-14B in 1991), which entered service with the fleet in 1988. These engines solved the reliability problems and provided nearly 30% more thrust, achieving a 1:1 dry thrust to weight ratio. The F-14D also used F110-GE-400 engines.
JTF10 - Company designation for the TF30 family of engines
JTF10A-7 - (TF30-P-2)
SNECMA / Pratt & Whitney TF106 - A derivative of the TF30 to power the Dassault Mirage III-V VTOL fighter.
SNECMA / Pratt & Whitney TF306 - A derivative of the TF30 to power the Dassault 'Mirage' IIIV 02 and tested in the Dassault Mirage F2.
Dassault Mirage F2
Dassault Mirage G2
General Dynamics F-111
General Dynamics F-111C
General Dynamics/Grumman EF-111A Raven
General Dynamics/Grumman F-111B
General Dynamics F-111K
Grumman F-14A Tomcat
LTV A-7A/B/C Corsair II
Length: 241.7 in. (6.139 m)
Diameter: 48.9 in. (1.24 m)
Dry weight: 3,985 lb. (1807 kg)
Compressor: 2 spool axial: 3 fan and 6 low pressure stages, 7 high pressure stages
Turbine: 3 stage low pressure turbine, 1 stage high pressure turbine
Maximum thrust: 14,560 lbf (64.766kN), 25,100 lbf (111.65kN) w/ afterburning
Overall pressure ratio: 19.8
Bypass ratio: 0.878:1
Turbine inlet temperature: 2150F (1176C)
Thrust-to-weight ratio: 6.0