Sukhoi S-37 Berkut
Purpose: To provide data to support the design of a superior air combat fighter.
Design Bureau: AOOT 'OKB Sukhoi',Moscow.
Almost unknown until its first flight, this aircraft is one of the most remarkable in the sky.
Any impartial observer cannot fail to see that, unless Sukhoi's brilliance has suddenly become dimmed, it is a creation of enormous importance. Like the rival from MiG, it provides the basis for a true 'fifth-generation' fighter which with rapid funding could swiftly become one of the greatest multirole fighters
in the world. Unfortunately, in the Russia of today it will do well to survive at all, especially as the WS has for political and personality reasons shown hostile indifference. In fact on 1st February 1996, when the first image of a totally new Sukhoi fighter leaked out in the form of a fuzzy picture of a tabletop model, the WS Military Council instantly proclaimed that this aircraft 'is not prospective from the
point of view of re-equipment within 2010- 25'. In fact the first hint of this project CAME during a 1991 visit by French journalists to CAHI (TsAGI), when they were shown a model of an aircraft with FSW (forwardswept wings) and canard foreplanes called the Sukhoi S-32. At the risk of causing confusion,
Sukhoi uses S for projects and Su for products, the same number often appearing in both categories but for totally different aircraft (for example, the Su-32 is piston-engined).
In December 1993, during the Institute's 75th-birthday celebrations, its work on the FSW was said to be 'for a new fighter of Sukhoi design'. The model shown in February 1996 again bore the number '32' but clearly had tailplanes as well as canards.
It had been known for many years that the FSW has important aeroelastic advantages over the traditional backswept wing (see OKB-1 bombers and Tsybin LL). At least up to Mach 1.3 (1,400 tol,500km/h, 870 to 930mph) the FSW offers lower drag and superior manoeuvrability, and the lower drag also translates as longer range. A further advantage is that takeoffs and landings are shorter. The fundamental aeroelastic problem with the FSW can be demonstrated by holding a cardboard wing out of the window of a speeding vehicle. A cardboard FSW tends to bend upwards violently, out of control. An FSW for a fast jet was thus very difficult to make until the technology of composite structures enabled the wing to be designed with skins formed from multiple layers of adhesive-bonded fibres of carbon or glass. With such skins the directions of the fibres can be arranged to give maximum strength, rather like the directions of the grain in plywood.
The first successful jet FSW was the Grumman X-29, first flown in December 1984. This exerted a strong influence on the Sukhoi S-32 design team, which Ander Mikhail Simonov was led by First Deputy General Designer Mikhail A Pogosyan, and included Sergei Korotkov who is today's S-37 chief designer. From 1983 the FSW was exhaustively investigated, not only by aircraft OKBs but especially by CAHI (TsAGI) and the Novosibirsk-based SibNIA, which tunnel-tested several FSW models based loosely on the Su-27. By 1990 Simonov was determined to create an FSW prototype, and three years later the decision had been taken not to wait for non-existent State funds but instead to put every available Sukhoi ruble into constructing such an aircraft. Despite a continuing absence of official funding, this has proved to be possible because of income from export sales of fighters of the Su-27 family. Construction began in early 1996, but in that year Western aviation magazines began chanting that the S-32 was soon to fly. Uncertain about the outcome, Simonov changed the designation to S-37, so that he could proclaim The
S-32 does not exist'. It had been hoped to fly the radical new research aircraft at the MAKS-97 airshow, but it was not ready in time. It was a near miss, because the almost completed S-37 had begun ground testing in July, and by August it was making taxi tests at LII Zhukovskii, the venue for the airshow. After
MAKS 97 was over it emerged again, and on 25th September 1997 it began its flight test programme. The assigned pilot is Igor Viktorovich Votintsev. A cameraman at the LII took film which was broadcast on Russian TV, when the aircraft was publicised as the Berkut (golden eagle). On its first flight, when for a while the landing gear was retracted, the S-37 was accompanied by a chase Su-30 carrying a photographer. It is a long way from being an operational fighter, but that is no reason for dismissing it as the WS, Ministry of Defence and the rival MiG company have done. Fortunately there are a few objective
people in positions of authority, one being Marshal Yevgenii Shaposhnikov, former WS C-in-C. Despite rival factions both within the WS and industry (and even within OKB Sukhoi) this very important aircraft has made it to to the flight-test stage. Whether it can be made to lead to a fully operational fighter is
problematical.
The primary design objective of this aircraft is to investigate the aerodynamics and control systems needed to manoeuvre at angles of attack up to at least 100°.
From the outset it was designed to be powered by two AL-41F augmented turbofans from Viktor Chepkin's yul'ka Saturn design bureau. In 1993 he confidentially riefed co-author Gunston on this utstanding engine. At that time it had already begun flight testing under a Tu-16 and on one ide of a M1G-25PD (aircraft 84-20). Despite his considerable maturity it was not cleared as the sole source of propulsion in time for the S-37, though the aircraft could be re-engined later. Accordingly the Sukhoi prototype is at present powered by two AL-31F engines, with dry and afterburning thrusts of 8,100 and 12,500kg (17,557 and 27,560 Ib), respectively.
Special engines were tailored to suit the S-37 installation, but at the start of the flight programme they still lacked vectoring nozzles. The engines are mounted only a short distance apart, fed by ducts from lateral inlets of the quarter-circle type. At present the inlets are of fixed geometry, with inner splitter plates standing away from the wall of the fuselage and bounded above by the underside of the very large LERX (leading-edge root extension), which in fact is quite distinct from the root of the wing. The wing itself comprises an inboard centroplan with leading-edge sweep of 70°, leading via a curved corner to the main panel with forward sweep of 24° on the leading edge and nearly 40° on the training edge. The forward-swept portion has a twosection droop flap over almost the whole leading edge, and plain trailing-edge flaps and outboard ailerons. Structurally it is described as '90 per cent composites'. The main wing panels are designed so that in a derived aircraft they could fold to enable the aircraft to fit into the standard Russian hardened aircraft shelter.
Aerodynamically the S-37 is another 'triplane', having canard foreplanes as well as powered tailplanes. The former are greater in chord than those of later Su-27 derivatives, the trailing edge being tapered instead of swept back. Likewise the tailplanes have enormous chord, but as the leadingedge angle is over 75° their span is very short.
As in other Sukhoi fighters, the tailplanes are pivoted to beams extending back from the wing on the outer side of the engines. Unlike previous Sukhois the tailplanes are not mounted on spigots on the sides of the beams but on transverse hinges across their aft end.
These beams also carry the fins and rudders, which are similar to those of other Sukhois apart from being further apart (a long way outboard of the engines) and canted outward.
After flight testing had started the rudders were given extra strips (in Russia called knives) along the trailing edge. When the S-37 is parked, with hydraulic pressure decayed, the foreplanes, tailplanes and ailerons come to rest 30° nose-up. The landing gear is almost identical to that of the Su-27K, with twin steerable nosewheels. In the photographs released so far no airbrakes or centreline braking-parachute container can be seen. Internal fuel capacity is a mere 4,000kg (8,8181b), though much more could be accommodated.
The cockpit has an Su-27 type upward-hinged canopy, and a sidestick on the right. The airframe makes structural provision for 8 tonnes (17,637 Ib) of external and internal weapons, including a gun in the left
centroplan. It is also covered in numerous flush avionics antennas, though the only ones that are functional are those necessary for aerodynamic and control research. A bump to starboard ahead of the wraparound windscreen could later contain an opto-electronic (TV, IR, laser) sight, while the two tail beams are continued different distances to the rear to terminate in prominent white domes, doubtless for avionics though they could conceivably house braking parachutes. These domes stand out against the startling dark blue with which this aircraft has been painted.
Sukhoi has stressed that this aircraft incorporates radar-absorbent and beneficially reflective 'stealth' features, though again the objective is research. Also standing out visually are the white-bordered red stars, though of course the aircraft is company-owned and bears 'OKB Sukhoi' in large yellow characters
on the fuselage, along with callsign 01, which confusingly is the same as the MiG 1.44.
The Russians have traditionally had a strong aversion to what appear to be unconventional solutions, and this has in the past led to the rejection of many potentially outstanding aircraft. The S-37 has to overcome this attitude, as well as the bitter political struggle within the OKB, with RSK MiG, with factions in the Ministry of Defence and air force and, not least, two banks which are battling to control the OKB.
Purpose: To provide data to support the design of a superior air combat fighter.
Design Bureau: AOOT 'OKB Sukhoi',Moscow.
Almost unknown until its first flight, this aircraft is one of the most remarkable in the sky.
Any impartial observer cannot fail to see that, unless Sukhoi's brilliance has suddenly become dimmed, it is a creation of enormous importance. Like the rival from MiG, it provides the basis for a true 'fifth-generation' fighter which with rapid funding could swiftly become one of the greatest multirole fighters
in the world. Unfortunately, in the Russia of today it will do well to survive at all, especially as the WS has for political and personality reasons shown hostile indifference. In fact on 1st February 1996, when the first image of a totally new Sukhoi fighter leaked out in the form of a fuzzy picture of a tabletop model, the WS Military Council instantly proclaimed that this aircraft 'is not prospective from the
point of view of re-equipment within 2010- 25'. In fact the first hint of this project CAME during a 1991 visit by French journalists to CAHI (TsAGI), when they were shown a model of an aircraft with FSW (forwardswept wings) and canard foreplanes called the Sukhoi S-32. At the risk of causing confusion,
Sukhoi uses S for projects and Su for products, the same number often appearing in both categories but for totally different aircraft (for example, the Su-32 is piston-engined).
In December 1993, during the Institute's 75th-birthday celebrations, its work on the FSW was said to be 'for a new fighter of Sukhoi design'. The model shown in February 1996 again bore the number '32' but clearly had tailplanes as well as canards.
It had been known for many years that the FSW has important aeroelastic advantages over the traditional backswept wing (see OKB-1 bombers and Tsybin LL). At least up to Mach 1.3 (1,400 tol,500km/h, 870 to 930mph) the FSW offers lower drag and superior manoeuvrability, and the lower drag also translates as longer range. A further advantage is that takeoffs and landings are shorter. The fundamental aeroelastic problem with the FSW can be demonstrated by holding a cardboard wing out of the window of a speeding vehicle. A cardboard FSW tends to bend upwards violently, out of control. An FSW for a fast jet was thus very difficult to make until the technology of composite structures enabled the wing to be designed with skins formed from multiple layers of adhesive-bonded fibres of carbon or glass. With such skins the directions of the fibres can be arranged to give maximum strength, rather like the directions of the grain in plywood.
The first successful jet FSW was the Grumman X-29, first flown in December 1984. This exerted a strong influence on the Sukhoi S-32 design team, which Ander Mikhail Simonov was led by First Deputy General Designer Mikhail A Pogosyan, and included Sergei Korotkov who is today's S-37 chief designer. From 1983 the FSW was exhaustively investigated, not only by aircraft OKBs but especially by CAHI (TsAGI) and the Novosibirsk-based SibNIA, which tunnel-tested several FSW models based loosely on the Su-27. By 1990 Simonov was determined to create an FSW prototype, and three years later the decision had been taken not to wait for non-existent State funds but instead to put every available Sukhoi ruble into constructing such an aircraft. Despite a continuing absence of official funding, this has proved to be possible because of income from export sales of fighters of the Su-27 family. Construction began in early 1996, but in that year Western aviation magazines began chanting that the S-32 was soon to fly. Uncertain about the outcome, Simonov changed the designation to S-37, so that he could proclaim The
S-32 does not exist'. It had been hoped to fly the radical new research aircraft at the MAKS-97 airshow, but it was not ready in time. It was a near miss, because the almost completed S-37 had begun ground testing in July, and by August it was making taxi tests at LII Zhukovskii, the venue for the airshow. After
MAKS 97 was over it emerged again, and on 25th September 1997 it began its flight test programme. The assigned pilot is Igor Viktorovich Votintsev. A cameraman at the LII took film which was broadcast on Russian TV, when the aircraft was publicised as the Berkut (golden eagle). On its first flight, when for a while the landing gear was retracted, the S-37 was accompanied by a chase Su-30 carrying a photographer. It is a long way from being an operational fighter, but that is no reason for dismissing it as the WS, Ministry of Defence and the rival MiG company have done. Fortunately there are a few objective
people in positions of authority, one being Marshal Yevgenii Shaposhnikov, former WS C-in-C. Despite rival factions both within the WS and industry (and even within OKB Sukhoi) this very important aircraft has made it to to the flight-test stage. Whether it can be made to lead to a fully operational fighter is
problematical.
The primary design objective of this aircraft is to investigate the aerodynamics and control systems needed to manoeuvre at angles of attack up to at least 100°.
From the outset it was designed to be powered by two AL-41F augmented turbofans from Viktor Chepkin's yul'ka Saturn design bureau. In 1993 he confidentially riefed co-author Gunston on this utstanding engine. At that time it had already begun flight testing under a Tu-16 and on one ide of a M1G-25PD (aircraft 84-20). Despite his considerable maturity it was not cleared as the sole source of propulsion in time for the S-37, though the aircraft could be re-engined later. Accordingly the Sukhoi prototype is at present powered by two AL-31F engines, with dry and afterburning thrusts of 8,100 and 12,500kg (17,557 and 27,560 Ib), respectively.
Special engines were tailored to suit the S-37 installation, but at the start of the flight programme they still lacked vectoring nozzles. The engines are mounted only a short distance apart, fed by ducts from lateral inlets of the quarter-circle type. At present the inlets are of fixed geometry, with inner splitter plates standing away from the wall of the fuselage and bounded above by the underside of the very large LERX (leading-edge root extension), which in fact is quite distinct from the root of the wing. The wing itself comprises an inboard centroplan with leading-edge sweep of 70°, leading via a curved corner to the main panel with forward sweep of 24° on the leading edge and nearly 40° on the training edge. The forward-swept portion has a twosection droop flap over almost the whole leading edge, and plain trailing-edge flaps and outboard ailerons. Structurally it is described as '90 per cent composites'. The main wing panels are designed so that in a derived aircraft they could fold to enable the aircraft to fit into the standard Russian hardened aircraft shelter.
Aerodynamically the S-37 is another 'triplane', having canard foreplanes as well as powered tailplanes. The former are greater in chord than those of later Su-27 derivatives, the trailing edge being tapered instead of swept back. Likewise the tailplanes have enormous chord, but as the leadingedge angle is over 75° their span is very short.
As in other Sukhoi fighters, the tailplanes are pivoted to beams extending back from the wing on the outer side of the engines. Unlike previous Sukhois the tailplanes are not mounted on spigots on the sides of the beams but on transverse hinges across their aft end.
These beams also carry the fins and rudders, which are similar to those of other Sukhois apart from being further apart (a long way outboard of the engines) and canted outward.
After flight testing had started the rudders were given extra strips (in Russia called knives) along the trailing edge. When the S-37 is parked, with hydraulic pressure decayed, the foreplanes, tailplanes and ailerons come to rest 30° nose-up. The landing gear is almost identical to that of the Su-27K, with twin steerable nosewheels. In the photographs released so far no airbrakes or centreline braking-parachute container can be seen. Internal fuel capacity is a mere 4,000kg (8,8181b), though much more could be accommodated.
The cockpit has an Su-27 type upward-hinged canopy, and a sidestick on the right. The airframe makes structural provision for 8 tonnes (17,637 Ib) of external and internal weapons, including a gun in the left
centroplan. It is also covered in numerous flush avionics antennas, though the only ones that are functional are those necessary for aerodynamic and control research. A bump to starboard ahead of the wraparound windscreen could later contain an opto-electronic (TV, IR, laser) sight, while the two tail beams are continued different distances to the rear to terminate in prominent white domes, doubtless for avionics though they could conceivably house braking parachutes. These domes stand out against the startling dark blue with which this aircraft has been painted.
Sukhoi has stressed that this aircraft incorporates radar-absorbent and beneficially reflective 'stealth' features, though again the objective is research. Also standing out visually are the white-bordered red stars, though of course the aircraft is company-owned and bears 'OKB Sukhoi' in large yellow characters
on the fuselage, along with callsign 01, which confusingly is the same as the MiG 1.44.
The Russians have traditionally had a strong aversion to what appear to be unconventional solutions, and this has in the past led to the rejection of many potentially outstanding aircraft. The S-37 has to overcome this attitude, as well as the bitter political struggle within the OKB, with RSK MiG, with factions in the Ministry of Defence and air force and, not least, two banks which are battling to control the OKB.
