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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

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    $\begingroup$ 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. $\endgroup$
    – Ron Beyer
    Jan 9, 2018 at 15:58
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    $\begingroup$ The T-38 was the Talon, the F-5 never had that name. $\endgroup$
    – Ralph J ♦
    Jan 9, 2018 at 16:16
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    $\begingroup$ The F-5A/B are the "Freedom Fighter", the F-5E/F are called "Tiger II". $\endgroup$
    – Ron Beyer
    Jan 9, 2018 at 16:25
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    $\begingroup$ In some way, P-51 Mustang and F-82 Twin Mustang are one & two engines versions, even if there's also twin fuselage. $\endgroup$
    – user721108
    Jan 9, 2018 at 17:08
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    $\begingroup$ 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, $\endgroup$
    – Carlo Felicione
    Jan 9, 2018 at 22:26

3 Answers 3

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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.

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  • $\begingroup$ Very interesting. Yes I would say that counts too! $\endgroup$
    – jwzumwalt
    Jan 9, 2018 at 18:23
  • $\begingroup$ 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. $\endgroup$
    – Carlo Felicione
    Jan 9, 2018 at 22:30
  • $\begingroup$ Who is the heck would even dream of such an abomination? $\endgroup$
    – RonJohn
    Jan 10, 2018 at 1:15
  • $\begingroup$ @RonJohn: Explained some of the reasons. $\endgroup$
    – John Dallman
    Jan 10, 2018 at 8:21
  • $\begingroup$ @CarloFelicione it's just as much a twin engined F-84 as the F-20 was a single engine F-5 :) $\endgroup$
    – jwenting
    Jan 10, 2018 at 10:02
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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.

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    $\begingroup$ Do you have a citation to back up this claim? This YouTube documentary says they are the same plane... youtube.com/watch?v=AvDfs6s4tbA&t=10s $\endgroup$
    – jwzumwalt
    Jan 9, 2018 at 21:25
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    $\begingroup$ 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. $\endgroup$
    – Carlo Felicione
    Jan 9, 2018 at 22:17
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    $\begingroup$ @jwzumwalt just another case of youtube being wrong I'm afraid. $\endgroup$
    – jwenting
    Jan 10, 2018 at 10:04
  • $\begingroup$ 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). $\endgroup$
    – jwenting
    Jan 10, 2018 at 10:07
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    $\begingroup$ 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. $\endgroup$
    – Carlo Felicione
    Jan 11, 2018 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.

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  • $\begingroup$ That's true, I hadn't thought of that. I guess any single engine aircraft with jato would also be in a gray area. $\endgroup$
    – jwzumwalt
    Jan 15, 2018 at 22:53
  • $\begingroup$ 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. $\endgroup$
    – jwenting
    Jan 16, 2018 at 7:15
  • $\begingroup$ 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. $\endgroup$
    – AMGiddings
    Jan 16, 2018 at 16:20

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