Sukhoi S-54

The Sukhoi S-54 is a series of three closely related aircraft proposals; the S-54 trainer aircraft, S-55 light fighter designed for export, and the S-56 carrier-capable light fighter. All members of the family resemble the Sukhoi Su-27 in general form, or the Sukhoi Su-33 more closely, but built around a single example of the Saturn AL-31 engine instead of two, and scaled down accordingly to a smaller layout. The design was offered to several potential customers, including South Africa and India, but was turned down. Development is apparently on hold, awaiting a launch customer.

The project traces its origins to a 1990 requirement to replace the aging Aero L-39 jet trainers, which were reaching the end of their service lives. The original Aero L-29 had originally been selected as a Warsaw Pact-wide trainer in 1961, after beating out the Yak-30 and PZL TS-11 Iskra. It started to be replaced in 1974 by the greatly updated L-39, powered by the new Ivchenko AI-25 engine. By 1990 the Soviet Air Force had about 1,000 L-39s on force, when the new Czech Republic stated they would no longer be supplying spares.

The Soviet Air Force's commander-in-chief, Air Marshal Yefimov, issued a statement on the issue on 20 April 1990. On 25 June 1990 the first official RFP document was issued for the Uchebno-Trenirovochnyi Samolyot (UTS) program. Four companies responded with designs, the Mikoyan MiG-AT, Yakovlev Yak-130 (then known as the Yak-UTS), the Myasischev M-200 and the S-54. Most of these designs were typical trainers; they were built to be docile in handling, low cost in operation, and were essentially all-new in design.

Sukhoi decided to take a different approach, and develop a true high-performance design closer to a fighter than a trainer. Advances in aerodynamics and flight controls allowed even the most advanced fighters have docile handling suitable for transition training, while at the same time the older generation aircraft had handling so different from modern aircraft that it gave them limited utility. Given their extensive experience with upgraded versions of the original Su-27, Sukhoi chose to use much of this design in the new trainer. Versions with one AL-31 or two smaller engines were studied, with the single-engine version favoured throughout.

...
Wikipedia