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 Sukhoi S-55 |
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Sukhoi's LFI Another new fighter from ANTK Sukhoi -- Sukhoi S-55 -- competes with MAPO MIG LFI (Legkii Frontovoi Istrebitel' - light frontal fighter) for the export market to exploit the Asian success of the Su-27 and Su-30 in China, India and Indonesia. The aircraft is an ideal complement to the heavy twin-engined Sukhoi's S-37 air-superiority fighter in the two-fighter air force concept. The smaller S-55 lags far behind the S-37 prototype, being at the preliminary design stage as of fall 1997. The S-55's first flight, probably in two-seat combat trainer form, is expected before the end of 1998. The S-55 owns its origins to a S-54 single-engine two~seat advanced supersonic trainer and light combat aircraft which alongside with Myasichev entry lost to subsonic twin-engined Mikoyan and Yakovlev trainers. The S-54 did not meet official requirement as a replacement of Aero L-29 and L-39 because RusAF was mostly interested in twin-engined aircraft. Nonetheless, the ANTK Sukhoi saw an opportunity for a supersonic advanced trainer in the world's shrinking trainer marked and continued the refinement of the basic S-54 design. The S-54 is targeted at the T-38 and MiG-21U operators and complimented by more sophisticated and capable armed single-seater version can take a bite out of F-16 share. The Evolution
Since the launch of the program in 1990 configuration has been refined at least twice, in 1992 and 1996. The original layout somewhat reminiscent of scaled-down Su-27 Flanker with all-swept mid-wing configuration and twin outward-canted fins lacked Flanker's prominent sting. An early configuration featured a single ventral engine air intake positioned under the cockpit area. During the second iteration of S-54 development, the aircraft received larger LREX, its bifurcated reshaped engine intakes were moved forward under the wingroots while more outward-canted twin fins were moved to the wing trailing-edges akin F/A-18. The wing was modified to have wingtip mounts for two dogfight IR homing AAM (R-73) and two hardpoints under each wing for air-to~air and air-to~surface guided weapons. The avionics for new trainer were tested on modified Su-25 and Su-27.
The experience gained with T-10-24 and naval Flanker determined the direction for further refinement of the S-54. This involved an addition of the canards, referred PGO in Russian (Perednee Gorizontal'noe Operenie - Forward Horizontal Stabilizers). The PGO solved control problems encountered at high angle-of-attack (AOA) flight regimes when the tailerons lost their efficiency in the wake of the wing. The cockpit was moved to the aft to provide additional volume for radar and avionics, the LREX area was reduced and the rear seat was raised to give a superb view for both pilots, changing the shape of two-piece canopy. This changes indicated shift in S-54 marketing from combat capable advanced trainer to a capable multirole two-seat light fighter aircraft.
A final and natural step of S-54 evolution involved elimination of the second seat and fill the space with more fuel and avionics to increase the range and widen the capabilities of the aircraft. Sukhoi have vast experience in similar modifications trying it out with Su-17M3 and Su-25T/39 attack aircraft. The final configuration redesignated S-55 was presented at Le Bourget 1997. A scale model (which was stolen during the first days of the show) showed the aircraft of T-10-24 aerodynamics utilizing the tandem triplane layout (canard foreplanes, wings and tailplanes). The second seat was removed, the canard foreplanes were shifted further forward from the wing roots and the tailerons placed further aft. This baby Su-33 had a pair of rearward facing stings, most likely housing additional fuel, avionics and brake shute(s). The Powerplant The original S-54 powerplant was Soyuz-Tumansky R-195FS turbojet, a modified Su-25 engine, rated at 41.2 kN (9,260 lb st) dry and 60.8 kN (13,670 lb st) with afterburner. As option RD-33 could have been used with minimal airframe modification. The latest S-55 is powered by the Saturn-Lyulka Al-31F turbofan with possible retrofit with trust vectoring control (TVC) Al-37FU or its modification with two-axis vectoring nozzle. The work on this engine was well in advance by the time of the first flight of the Su-37. At the time of the Paris show Sukhoi had no plans to use any TVC developments of the basic Al-31F for the S-55.
Radar and Armament The Phazotron Sokol (Falcon in Russian) X-band phased array fire-control radar is a primary candidate for the S-55. This radar is compatible with R-27R1, R-27T1, RVV-AE, R-73E AAMs and Kh-31A air-to-surface missile. The Sokol has four target track-while-scan capability in air-to-ground mode and 24 targets in track-while-scan air-to-air mode with simultaneous engagement of six. A maximum range of 180km is thought. The models of S-54 and S-55 were seen with R-73 AAM on the wingtip stations, R-77 and Kh-29A on wing pylons. The wide range of the Sokol's compatibility suggest that sooner or later these weapons will find their way to the arsenal of the new light fighter from Sukhoi.
S-54 vital statistics
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