EJERCICIO DE PROYECCIÓN DEL ESTADO DE RESULTADOS

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 air- craft is one of the most remarkable in the sky. Any impartial observer cannot fail to see that, unless Sukhoi's brilliance has suddenly be- come dimmed, it is a creation of enormous importance. Like the rival from MiG, it pro- vides 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, especial- ly 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 (forward- swept wings) and canard foreplanes called the Sukhoi S-32. At the risk of causing confu- sion, Sukhoi uses S for projects and Su for products, the same number often appearing in both categories but for totally different air- craft (for example, the Su-32 is piston-en- gined). 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 Feb- ruary 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 manoeu- vrability, and the lower drag also translates as longer range. A further advantage is that take- offs and landings are shorter. The fundamen- tal 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 vio- lently, out of control. An FSW for a fast jet was

thus very difficult to make until the technolo- gy of composite structures enabled the wing to be designed with skins formed from multi- ple layers of adhesive-bonded fibres of car- bon 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 under Mikhail Simonov was led by First Deputy Gen- eral Designer Mikhail A Pogosyan, and in- cluded Sergei Korotkov who is today's S-37 chief designer. From 1983 the FSW was ex- haustively investigated, not only by aircraft OKBs but especially by CAHI (TsAGI) and the Novosibirsk-based SibNIA, which tunnel-test- ed 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 ab- sence of official funding, this has proved to be possible because of income from export

S U K H O I S-37 B E R K U T

Above and below: Two views of S-37 Berkut. sales of fighters of the Su-27 family. Construc- tion 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 designa- tion 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 Vik- torovich 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 car- rying a photographer. It is a long way from being an operational fighter, but that is no rea-

son 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 con- trol 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 Lyul'ka Saturn design bureau. In 1993 he con- fidentially briefed co-author Gunston on this outstanding engine. At that time it had already begun flight testing under a Tu-16 and on one side of a M1G-25PD (aircraft 84-20). Despite this 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 pro- gramme they still lacked vectoring nozzles. The engines are mounted only a short dis- tance 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 under- side of the very large LERX (leading-edge root extension), which in fact is quite distinct from the root of the wing. The wing itself compris- es 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 trailing edge. The forward-swept portion has a two- section droop flap over almost the whole leading edge, and plain trailing-edge flaps and outboard ailerons. Structurally it is de- scribed as '90 per cent composites'. The main wing panels are designed so that in a derived aircraft they could fold to enable the aircraft

S U K H O I S-37 B E R K U T

Three views of S-37 Berkut.

to fit into the standard Russian hardened air- craft shelter. Aerodynamically the S-37 is an- other 'triplane', having canard foreplanes as well as powered tailplanes. The former are greater in chord than those of later Su-27 de- rivatives, the trailing edge being tapered in- stead of swept back. Likewise the tailplanes have enormous chord, but as the leading- edge 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 out- ward. After flight testing had started the rud- ders 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 steer- able nosewheels. In the photographs re- leased so far no airbrakes or centreline braking-parachute container can be seen. In-

ternal fuel capacity is a mere 4,000kg (8,8181b), though much more could be ac- commodated. The cockpit has an Su-27 type upward-hinged canopy, and a sidestick on the right. The airframe makes structural pro- vision 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 wind- screen 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 con- ceivably house braking parachutes. These domes stand out against the startling dark blue with which this aircraft has been paint- ed. Sukhoi has stressed that this aircraft in- corporates radar-absorbent and beneficially reflective 'stealth' features, though again the objective is research. Also standing out visu- ally 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 uncon- ventional solutions, and this has in the past led to the rejection of many potentially out- standing 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 bat- tling to control the OKB.

Dimensions Span

Length (ex PVO boom) Wing area about

Weights

Take-off mass given as 16.7m 22.6m 67m2 24 tonnes 54 ft m in 74 ft 1% in 721 ft2 52,910 Ib (the design maximum is higher)

Performance

Design maximum speed 1,700 km/h, 1,057 mph (Mach 1.6) (which would explain the fixed-geometry inlets. At Mach numbers much higher than this the FSW is less attractive)

T S Y B I N Ts-1, LL

TsybinTs-1, LL

Purpose: To study wings for transonic flight. Design Bureau: OKB-256, Chief Designer Pavel Vladimirovich Tsybin, professor at Zhukovskii academy.

In September 1945 the LIl-MAP (Flight Re- search Institute) asked Tsybin to investigate wings suitable for flight at high Mach num- bers (if possible, up to 1). In 1946 numerous models were tested at CAHI (TsAGI), as a re- sult of which OKB-256 constructed the Ts-1, also called LL-1 (flying laboratory 1). Almost in parallel, a design team at the OKB led by A V Beresnev developed a new fuselage and tail and two new wings, one swept back and the other swept forward. The LL-1 made 30 flights beginning in mid-1947 with NIl-WS pilot M Ivanov, and continuing with Amet- Khan Sultan, S N Anokhin and N S Rybko. On each flight the aircraft was towed by a Tu-2. Casting off at 5-7km (16,400-23,000ft), the air- craft was dived at 45°-60° until at full speed it was levelled out and the rocket fired. In win- ter 1947-48 the second Ts-1 was fitted with the swept-forward wing to become the LL-3. This made over 100 flights, during which a speed of l,200km/h (746mph) and Mach 0.97 were reached, without aeroelastic problems and yielding much information. The swept- back wing was retrofitted to the first aircraft to create the LL-2, but this was never flown.

The original Ts-1 (LL-1) was essentially all- wood. The original wing had two Delta (resin- bonded ply) spars, a symmetric section of 5 per cent thickness, 0° dihedral and +2° inci- dence. It had conventional ailerons and plain flaps (presumably worked by bottled gas pressure). Take-offs were made from a two- wheel jettisonable dolly, plus a small tail- wheel. In the rear fuselage was a PRD-1500 solid-propellant rocket developed by 11 Kar- tukov, giving 1,500kg (3,307 Ib) (more at high altitude) for eight to ten seconds. Flight con- trols were manual, with mass balances. On early flights no less than one tonne (2,2051b) of water was carried as ballast, simulating in- strumentation to be installed later. This was jettisoned before landing, when the aircraft (now a glider) was much more manoeu- vrable. Landings were made on a skid. Vari- ous kinds of instrumentation were carried, and at times at least one wing was tufted and photographed. The LL-3 was fitted with a metal wing with a forward sweep of 30° (ac- cording to drawings this was measured on the leading edge), with no less than 12° dihe- dral. The new tailplane had a leading-edge sweepback of 40°. To adjust the changed cen- tres of lift and of gravity new water tanks were fitted in the nose and tail. Both LL-1 and LL-3 were considered excellent value for money.

LL-1, showing take-off trolley

LL-3

LL-2, with LL-3 shown dotted

T S Y B I N Ts-1, L L

LL-3, showing take-off trolley

Left: LL-1. Below left: LL-2.

Below: LL-2, left wing tufted.

Dimensions (LL-1) Span Length Wing area Weights Empty Loaded Landing Performance Max speed reached Landing speed 7.1m 8.98m 10.0m2 1 tonne 2,039 kg 1,100kg l,050km/h 120km/h 23 ft 3^ in 29 ft 514 in 108ft2 2,205 Ib 4,495 Ib 2,425 Ib 652 mph 74.6 mph Dimensions (LL-3) Span Length Wing area Weights Loaded Landing Performance Max speed reached Landing speed 7.22m 8.98m 10.0m2 2,039kg 1,100kg l,200km/h 120km/h 23 ft 814 in 29 ft 5^ in 108ft2 4,495 Ib 2,425 Ib 746 mph 74.6 mph

Tsybin RS

T S Y B I N RS

Purpose: To create a winged strategic delivery vehicle.

Design Bureau: OKB-256, Podberez'ye, Director P V Tsybin.

In the early 1950s it was evident that the forth- coming thermonuclear weapons would need strategic delivery systems of a new kind. Until the ICBM (intercontinental ballistic missile) was perfected the only answer appeared to be a supersonic bomber. After much plan- ning, Tsybin went to the Kremlin on 4th March 1954 and outlined his proposal for a Reak- tivnyi Samolyot (jet aeroplane). The detailed and costed Preliminary Project was issued on 31st January 1956, with a supplementary sub- mission of a reconnaissance version called 2RS. Korolyov's rapid progress with the R-7 ICBM (launched 15th May 1957 and flown to its design range on 21st August 1957) caused the RS to be abandoned. All effort was trans- ferred to the 2RS reconnaissance aircraft (de- scribed next).

The RS had an aerodynamically brilliant configuration, precisely repeated in the British Avro 730 which was timed over a year later. The wing was placed well back on the long circular-section fuselage and had a sym- metric section with a thickness/chord ratio of 2.5 to 3.5 per cent. It had extremely low as- pect ratio (0.94) and was sharply tapered on both edges. Large-chord flaps were provided inboard of conventional ailerons, other flight

controls comprising canard foreplanes and a rudder, all surfaces being fully powered. The cockpit housed a pilot in a pressure suit, seat- ed in an ejection-seat under a canopy linked to the tail by a spine housing pipes and con- trols. The RS was to be carried to a height of 9km (29,528ft) under a Tu-95N. After release it was to accelerate to supersonic speed (de- sign figure 3,000km/h) on the thrust of two jet- tisoned rocket motors. The pilot was then to start the two propulsion engines, mounted on the wingtips. These were RD-013 ramjets, de- signed by Bondaryuk's team at OKB-670. Each had a fixed-geometry multi-shock inlet and convergent/divergent nozzle matched to the cruise Mach number of 2.8. Internal di- ameter and length were respectively 650mm (2ft IHin) and 5.5m (18ft 1/2in). The 1955 pro- ject had 16.5 tonnes of fuel, or nearly 3.5 times the 4.8-t empty weight, but by 1956 the latter had grown and fuel weight had in conse- quence been reduced. The military load was to be a 244N thermonuclear bomb weighing 1,100kg (2,4251b). The only surviving drawing shows this carried by a tailless-delta missile towed to the target area attached behind the RS fuselage (see below). Data for this vehicle are not known.

Outstandingly advanced for its day, had this vehicle been carried through resolutely it would have presented 'The West' with a seri- ous defence problem.

Dimensions

Span (over engine centrelines) 9.0 m Basic wing 7.77 m Foreplane 3.2 m Length 27.5 m Wing area 64 m2 Weights Empty 5,200 kg Fuel 10,470kg Maximum take-off weight 2 1 , 1 60 kg

Performance Range at 3,000 km/h (1,864 mph, Mach 2.82) at 28 km (91 ,864 ft) altitude 13,500 km Landing speed/ 245 km/h run 1,100m 29 ft 6% in 25ft53/4in 10 ft 6 in 90 ft 2% in 689ft2 ll,4641b 23,082 Ib 46,649 Ib 8,389 miles 152 mph 3,610ft RS

T S Y B I N 2RS

Tsybin 2RS

Purpose: To create a strategic reconnaissance aircraft.

Design Bureau: OKB-256, Podberez'ye, Director P V Tsybin.

As noted previously, the 2RS was launched as a project in January 1956. It was to be a mini- mum-change derivative of the RS, carried to high altitude under the Tu-95N and subse- quently powered by two RD-013 ramjets. However, it was decided that such an aircraft would be operationally cumbersome and in- flexible, and that, despite a very substantial reduction in operational radius, it would be preferable to switch to conventional after- burning turbojets and take off from the ground. The revised project was called RSR (described later). The Ministry gave this the go-ahead on 31st August 1956, but work on

the 2RS continued until is was terminated in early 1957. As it was no longer needed, Tupolev then stopped the rebuild of the Tu- 95N carrier at Factory No 18 at Kuibyshev.

The 2RS would have differed from the RS principally in having the canard foreplanes re- placed by slab tailplanes. Behind these was installed a braking parachute. Provision was made for large reconnaissance cameras in the fuselage ahead of the wing. Surviving drawings (below) also show provision for a 244N thermonuclear weapon, this time as a free-fall bomb recessed under the fuselage further aft. Carrying this would have moved the main landing gear unacceptably close to the tail.

Though there was much to be said for air launch, the basic concept looked increasing- ly unattractive.

Dimensions

Span (over engine centrelines) 9.0 m Length 27.4 m Wing area 64.0 m2

Weight

Empty 9,030 kg Fuel 11,800kg Loaded (cameras only) 20,950 kg

Performance Max (also cruising) speed

at 20 km (65,61 7 ft) 2,700 km/h Service ceiling 27 km Range (high altitude) 7,000 km Landing speed/ 230 km/h run 800 m 29 ft 6% in 89 ft 1 13/ in 689ft2 19,907 Ib 26,014 Ib 46,1 86 Ib 1,678 mph (Mach 2.54) 88,583 ft 4,350 miles 143 mph 2,625 ft 2RS

T S Y B I N RSR