Many people get shocked upon realizing how big modern fighter jets actually are. The length of the Sukhoi Su-27 Flanker is almost 22 meters (72 ft) – just slightly shorter than the fuselage of the Boeing B-17 Flying Fortress, the iconic strategic bomber from WWII. Some of the newer variants based on the Su-27 – such as carrier-based Su-33 or ground attack Su-34 – are even larger.
To be fair, the Su-27 is one of the biggest 4th generation fighter jets, and the majority of its analogues – such as the McDonnell Douglas F-15 Eagle – are somewhat smaller. Nevertheless, despite being such a beast of a plane, the Flanker still became one of the most mass-produced combat aircraft of its generation. In many of the world’s largest air forces – such as the Indian Air Force and People’s Liberation Army Air Force of China – derivatives of the Su-27 still constitute a significant part of the fighter fleet.
But among its many variants, derivatives and spin-offs, there was one crazier than the others. That was the S-54 and its two variants – S-55 and S-56, designed by Sukhoi in the early 90s as a proposal for a trainer, a light fighter jet, and carrier-based aircraft respectively. And the main idea of those proposals was shrinking the massive Su-27 until it becomes the smallest fighter jet in the world.
Russia’s First Jet Trainer Contest
The inciting incident to create such aircraft came in April 1990, when the Commander-in-Chief of the Soviet Air Force issued a request for the design of a new advanced jet trainer.
Before that, Soviet fighter pilots were mainly training on Czechoslovakian Aero L-29s and L-39s. By the late 80s the jets started showing their age, and were not sufficient to serve as the last steps before transitioning onto advanced 4th generation fighter jets.
Something faster, more manoeuvrable and more powerful was needed. Initially, the request for a new trainer was addressed at Mikoyan design bureau, whose MiG-29 was a successful light counterpart to the heavy Su-27. But in 1991 other bureaus – Myasischev, Yakovlev and Sukhoi – were attached. Each of them offered a project of an advanced trainer. In 1993 Yakovlev was selected as the winner. Its proposal (after heavy modification, cooperation with Italian Aermacchi and a further decade of development) eventually became the Yak-130, Russian Air Force’s current jet trainer aircraft. But Sukhoi’s and Mikoyan’s proposals did not compete with it. They were rejected right away, in 1992, supposedly – for not meeting the requirements of the contest.
The reality was, in the years right after the Soviet Union’s disintegration, Russia’s economy collapsed. It was clear that the trainer contract had to be given to one of the smaller design bureaus, as Sukhoi and Mikoyan were already building Su-27s and MiG-29s – the country’s main fighter jets. Favouring one of them with an order for an additional aircraft would be detrimental for other manufacturers, who would lose their last chance for receiving government funding. So, the disqualification had nothing to do with the proposals themselves. It was purely a result of Russia’s economic situation. That situation was also reflected in four trainer designs that were offered. All of them were focused on being as cheap as possible, using previous research and elements of other aircraft, as well as making an emphasis of aircraft’s adaptability for various missions and purposes.
Sukhoi’s design took both of those ideas the farthest.
Shrinking The Flanker
In the late 80s Sukhoi spent quite a lot of effort designing improved versions of the Su-27: the Su-30 (Flanker-C), the Su-33 (Flanker-D) and the Su-37 (Flanker-F), as well as some others. All of them retained the basic layout of the original Su-27, but featured extensive upgrades to the avionics, engines and armament. To further improve Flanker’s high manoeuvrability, canards were added – additional flight control surfaces in front of the wings that became the most prominent feature of this new family of jets.
These aircraft were very advanced, yet they carried a cost to match. Finding a way to make them cheaper while retaining much of the capability would be a lucrative proposal for the Soviet Air Force, which was strapped for cash.
This idea greatly correlated with the requirement for an advanced trainer. After all, having a fleet of training aircraft that are – by design – very cheap, but almost as capable as a true fighter jet, means having a fleet of light, affordable fighter jets too. So, Sukhoi came up with three versions for its new airplane. The S-54 would be an advanced trainer; the S-55 would be a light fighter intended to supplement the heavier ones, and the S-56 would be its carrier-borne variant.
All of them were scaled-down versions of the Su-27 platform, both visually and functionally. Of course, the design process was quite far from simply making the measurements smaller: aircraft design does not work like that, and the engineers had to perform myriads of complicated calculations to make the new jet work. Yet, to the naked eye, the result speaks for itself: the new aircraft looked exactly like a small Flanker.
All of this means that had the S-54 been built, it would have become the smallest and lightest modern fighter jet, being on par with Korean War-era aircraft, such as the MiG-15 and the F-86. Light fighter jets of the fourth generation – such as the F-16, the MiG-29 and the HAL TEJAS – were all substantially bulkier, and even previous-generation designs, such as the F-5 and the MiG-21, were heavier by several hundreds of kilograms.
Performance-wise the S-54 would, of course, be no match for full-sized aircraft, but by no means would it be a push-over. With the top speed of Mach 1.5 and a range of 2,000 km (1,100 nm) it would carry a full range of Soviet armament for both air-to-ground and air-to-air missions.
The most significant difference from the Su-27 was S-54’s engine: instead of two it would carry just one. Initially slated to be the Tumansky R-13 (also used on the MiG-21 and Su-25), it was later swapped for the Saturn AL-31, two of which are featured on a normal Su-27.
This would mean that the baby jet would have half of Su-27’s thrust for just one-fourth of its weight, making it’s thrust-to-weight ratio unmatched: a significant advantage in air combat, even nowadays.
Of course, neither the S-54 nor any of its variants were ever built. After the rejection from the trainer program Sukhoi continued to work on the jet for several years, but eventually it was dropped. In the late 90s the company attempted to offer S-55 and S-56 for export, to no success. In the early 2000s the design saw some resurgence once again – reportedly, Russian Air Force evaluated it, only to discard the idea. Yet, in some way, Sukhoi’s intention of having a super-light fighter jet in the world of heavy and expensive 5th generation stealth fighters was a bit ahead of its time. KAI T-50 Golden Eagle, Korean advanced jet trainer, saw great success and was purchased as a light fighter jet (FA-50) by numerous countries – its appearance in 2002 kickstarted Sukhoi’s last attempts to lobby for S-55. The same happened to Yak-130 and Alenia Aermacchi M-346 trainers, employed as light fighters by some countries that possess them.
So, had Russia proceeded with its plans for the baby Flanker, it could have had an aircraft with great export potential. On the other hand, the time was not right for it, as even the full-sized Soviet jets were being bought left-and-right by third world countries.
Anyway, at least one result of the S-54 program is undeniable: it resulted in, possibly, the cutest fighter jet ever. Of course, the combat potential of this feature is up for a debate.