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Northrop originally built the F-5 "Freedom Fighter" (and T-38 "Talon") with two engines. Later it was re-fitted with a single F404 engine from the F/A-18, re-designating it the F-20 "Tigershark" to avoid confusion. The first F-5A and T-38 flights took place in 1959.

[Addendum: There is no real contradiction, the T-38 "Talon" was a two place trainer version of the F-5 "Freedom Fighter". Most aircraft don't re-designate between one and two seat versions, but Northrop or the military did in this case.] See the history of the F-5 YouTube Video

"Though the USAF had no acknowledged need for a light fighter, it did procure roughly 1,200 Northrop T-38 Talon trainer aircraft, which were directly based on the F-5A." https://en.wikipedia.org/wiki/Northrop_F-5

"The F-5G was an advanced single-engined variant later renamed the F-20 Tigershark." https://en.wikipedia.org/wiki/Northrop_T-38_Talon

Have any other fighters (world wide) offered a fighter with one and two engine models?

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Twin engine F-5 "Freedom Fighter".

 

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Single engine F-20 (F-5G) "Tigershark". Wikipedia

jwzumwalt
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    There were only 3 F-20's ever made, two of which crashed. The DoD decided to go with the F-16 (aka Lawn Dart) after that. – Ron Beyer Jan 09 '18 at 15:58
  • Basically for the same reasons any aircraft would have multiple engines. There may also be a difference in maneuverability but I'm not necessarily qualified to comment on that. – Dave Jan 09 '18 at 16:13
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    The T-38 was the Talon, the F-5 never had that name. – Ralph J Jan 09 '18 at 16:16
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    The F-5A/B are the "Freedom Fighter", the F-5E/F are called "Tiger II". – Ron Beyer Jan 09 '18 at 16:25
  • While they look very similar, the T-38 is not the trainer version of the F-5. The wings are different and the fuselage is more curved on the T-38. – Ron Beyer Jan 09 '18 at 16:52
  • According to the cited YouTube video The T38 is a variant of the F5. The video goes into some interesting major quick bolt add-on such as a reconnaissance and gunship version of the front half of the aircraft. This airplane was truly a jigsaw approach to a light weight fighter. – jwzumwalt Jan 09 '18 at 17:06
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    In some way, P-51 Mustang and F-82 Twin Mustang are one & two engines versions, even if there's also twin fuselage. – user721108 Jan 09 '18 at 17:08
  • @ qqjkztd - +1 great answer, I was thinking jets but yes that certainly counts! – jwzumwalt Jan 09 '18 at 17:10
  • Not a fighter, but didn't Avro develop a 4-engine version of the 2-engine Manchester bomber, during WW2? – user_1818839 Jan 09 '18 at 19:43
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    Actually, the T-38 came first, follows by a export fighter derivative called the F-5. Both are based upon Northrop’s N-156 design study, – Romeo_4808N Jan 09 '18 at 22:26
  • Not directly related but A5 has a 3 engine version proposed. – user3528438 Jan 10 '18 at 05:11
  • @jwzumwalt the F-5 was created out of the T-38 when the US government identified the need for a cheap low tech combat aircraft that could be supplied to client nations either too poor or not trusted enough to be supplied with the then current line of front end US combat aircraft. – jwenting Jan 10 '18 at 10:00
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    The F-20 wasn't a single engined F-5, it was a completely new aircraft designed out of the F-5. It's similarly related to the F-5 as the F-100 is to the F-86. – jwenting Jan 10 '18 at 10:01
  • "Though the USAF had no acknowledged need for a light fighter, it did procure roughly 1,200 Northrop T-38 Talon trainer aircraft, which were directly based on the F-5A."* https://en.wikipedia.org/wiki/Northrop_F-5* – jwzumwalt Jan 11 '18 at 18:07
  • That would be impossible since the T-38 began its life in 1959 as an N-156T derivative and the F-5 in 1962 as an N-156F derivative. Wikipedia screwed up there. – Romeo_4808N Jan 11 '18 at 19:04
  • The Dassault Balzac V was a VTOL testbed with nine engines. It was a modified Mirage III which had one engine. – Hobbes Feb 06 '20 at 08:30

3 Answers3

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The Republic F-84F Thunderstreak was a fairly normal early jet fighter, powered by a single Wright J65 turbojet engine.

Its mutant offspring, the Republic XF-84H "Thunderscreech" was a experimental turboprop fighter, powered by an experimental Allison T40 engine, which consisted of two Allison T38 engines, joined through a common gearbox.

This was a twin-engine aircraft from the maintenance point of view, since there were two sets of turbo-machinery to go wrong. It looked like a single-engine aircraft, and flew like nothing on earth, owing to the strange effects of two sets of supersonic shockwaves from the contra-rotating propellers hitting the wings several times per second. Its first test pilot refused to have anything more to do with it after the first flight; the second test pilot flew it eleven times, but Republic did not submit the aircraft for USAF trials.

Edit: The reason for doing this was that early jet engines were very fuel-thirsty, while turboprops got much better mileage. The propeller was supersonic because that was necessary to absorb the power in a small enough propeller to fit within the aircraft's ground clearance. It wasn't remotely a good idea, but it may have shown the USAF that jet-age aircraft development was harder than it had been in the piston-engine era.

John Dallman
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  • Very interesting. Yes I would say that counts too! – jwzumwalt Jan 09 '18 at 18:23
  • I don’t know if you would call the XF-84H an option for a twin engined version of the F-84 airplane. It was an experimental prototype used to study the possibility of a supersonic propeller driven fighter which never went into production. – Romeo_4808N Jan 09 '18 at 22:30
  • Who is the heck would even dream of such an abomination? – RonJohn Jan 10 '18 at 01:15
  • @RonJohn: Explained some of the reasons. – John Dallman Jan 10 '18 at 08:21
  • @CarloFelicione it's just as much a twin engined F-84 as the F-20 was a single engine F-5 :) – jwenting Jan 10 '18 at 10:02
  • Kind of but really not. The XF-84H was a research aircraft and never really intended for production whereas the F-20 was in a production ready state and was being marketed by Northrop for sale to allied nations. – Romeo_4808N Jan 10 '18 at 17:34
  • @CarloFelicione they fully intended to build the F-84H or a close derivative, until they actually tried it. I think there even was an MOU for a production batch signed before the XF even was built. That was the norm at the time. X meant prototype as much as research. – jwenting Jan 16 '18 at 07:13
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Well, the F-20 is a different airplane from the F-5, albeit an evolution of the original Northrop N-156 design which developed into both the F-5 and F-18 families of airplanes, so no aircraft model was ever offered with the option of having one or two engines.

Ideally fighters are more suited toward the single engine configuration as powering one with multiple engines invariably adds more complexity, systems to manage and weight. The only justification for which is an increased thrust to weight ratio on a larger, heavier airframe. I’d guess Northrop would have dearly loved to have the F-5 powered by a single GE J-79 turbojet given its for the time supreme thrust to weight ratio, but I don’t know if the engine was available for export back at that time. The F-5 was also an export fighter derivative of the T-38 airplane which was currently powered by a pair of GE J-85 turbojets, originally designed for expendable use powering cruise missiles, which offered the Talon good performance and were available to sell to other nations.

Twenty years of both fighter aircraft and engine development provided the F-20 design team with the new GE F-404 engine, comparable in performance with the J-79 but with 6000 fewer parts and greater thrust to weight ratio, highly resistant to compressor stalls, and greater reliability than the older J-79. This along with the availability for export made the F404 the preferred choice on the F-20; there was never any attempt to make a multi engine variant of the F-20.

Romeo_4808N
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    Do you have a citation to back up this claim? This YouTube documentary says they are the same plane... https://www.youtube.com/watch?v=AvDfs6s4tbA&t=10s – jwzumwalt Jan 09 '18 at 21:25
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    The doc describes the F-20 as “the final development of the F-5 family” ie a development which became a new aircraft. The YF-17/F-18 Family is also a development of the F-5 family of fighters. The F-20 did begin its design life as the F-5G but was given a new designation of F-20. While it does have a similar configuration to the original F-5, it’s a different aircraft underneath. – Romeo_4808N Jan 09 '18 at 22:17
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    @jwzumwalt just another case of youtube being wrong I'm afraid. – jwenting Jan 10 '18 at 10:04
  • AFAIK the engines were chosen for the F-5A based on cost and performance requirements. The requirement was for a subsonic or transonic combat aircraft with low cost and maintenance requirements, for distribution to nations with no qualified personel to maintain front line US combat aircraft and/or for which export of such was not allowed. That's why the radar installation and provisions for guided weapons were also stripped out (though some F-5A variants like the Canadian and Dutch ones could carry some guided weapons). – jwenting Jan 10 '18 at 10:07
  • Lacks supporting citation - just an opinion. – jwzumwalt Jan 10 '18 at 15:29
  • "Though the USAF had no acknowledged need for a light fighter, it did procure roughly 1,200 Northrop T-38 Talon trainer aircraft, which were directly based on the F-5A."* https://en.wikipedia.org/wiki/Northrop_F-5* – jwzumwalt Jan 11 '18 at 18:04
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    Sorry, But Wikipedia doesn’t know what it’s talking about in that case. The Northrop N-156 design evolved into the T-38 first, then an N-156 derivative became the F-5 family. Wikipedia while pretty good is not always accurate. – Romeo_4808N Jan 11 '18 at 18:46
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Technically, several single-engine aircraft has been either designed or modified to utilize a second rocket engine at some point during their lives.

For one example, see the Lockheed NF-104A

The Soviet WWII era Su-6 and Su-7 would examples of a piston engine single (the Su-6) being re-equipped with a hybrid piston and rocket propulsion system.

It could also be argued that the Mirage IV fits this criteria, as its design was derived from the existing Mirage IIIA.

AMGiddings
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  • That's true, I hadn't thought of that. I guess any single engine aircraft with jato would also be in a gray area. – jwzumwalt Jan 15 '18 at 22:53
  • and then there's the ill fated Balzac, another multi engine Mirage variant. Twin Mustang fits the idea, and the various German attempts to mate 2 bombers at the wing to create a larger bomber. – jwenting Jan 16 '18 at 07:15
  • The UH-1 Huey and AH-1 Cobra/SuperCobra could also be considered examples. Initial versions used a single engine, while later models use twin engines to drive the main rotor. – AMGiddings Jan 16 '18 at 16:20