ESTRUCTURA DE PROYECCIÓN DEL ESTADO DE RESULTADOS

Purpose: To create a supersonic radar- equipped interceptor.

Design Bureau: Reopened OKB-51 of P O Sukhoi, Moscow.

After closure of his OKB, in December 1949 Sukhoi became deputy to his old colleague A N Tupolev, where among other things he collaborated with CAHI (TsAGI) in establish- ing the best wing for supersonic fighters. He played the central role in deciding on two contrasting forms. For tactical fighters the choice was an S (Strelovidnoye, arrow like) swept wing with a !4-chord sweep angle of 60° or 62°, and for radar-equipped interceptors the best answer was a T (Treoogol'noye, three-angled, ie delta) wing with J4-chord sweep angle of 57° or 60°. For obvious rea- sons, the latter type of wing was soon dubbed Balalaika. On Stalin's death Sukhoi applied for permission to reopen his OKB. This was at once granted, and in May 1953 he gathered his team at the original premises at 23A Po- likarpov Street. Following from his aerody- namic research he received MAP contracts for basically similar aircraft, S-l with the S wing and T-l with the T wing. As he chose to build large aircraft powered by a powerful Lyul'ka engine, which matured rapidly, their development was swift. S-l led to the pro- duction Su-7 and many other aircraft. T-l was replaced on the drawing board by T-3, and

this was flown by V N Makhalin on 26th May 1956. Just over a month later it was the final aircraft in the parade of new fighters at Tushi- no on 24th June, causing intense interest and great confusion in the West. A few weeks be- hind came the PT-7. These were tested inten- sively by a pilot team which included Pronyarkin, Koznov, Kobishkan and the fu- ture Sukhoi chief test pilot Vladimir Ilyushin, son of the General Designer.

Like S-l, the T-3 had a barrel-like fuselage, much of its length being occupied by the big afterburning AL-7F engine, rated at 9,000kg (19,840 Ib) with afterburner and 6,500kg (14,330 Ib) dry. The tails of the two aircraft were almost identical, and there were only minor differences in the cockpit, landing gear and most of the systems. The wings of both aircraft were in the low/mid position, at- tached by precision bolts to strong forged root ribs on heavy forged fuselage frames. The wing had S-9s profile with a thickness/chord ratio of 4.2 per cent over most of the span. The shape was almost a perfect delta, with a lead- ing-edge angle of 60°. The leading edge was fixed, while the trailing edge comprised rec- tangular slotted flaps with a maximum angle of 25° and sharply tapered ailerons with inset hinges which extended to the near-pointed tips. Incidence was 0° and dihedral -2° (ie, 2° anhedral). Structurally the wing had three main spars, each principally a machined forg-

ing, plus a rear spar to carry the trailing-edge surfaces. The leading edge was attached to the front of a further spar forming the front of the structural box. The forward triangle ahead of Spar 1 and the volume between Spars 2 and 3 were sealed and formed inte- gral fuel tanks. The whole space between Spars 1 and 2 was occupied by the retracted main landing gear. The flaps were driven at their inboard ends by electro-hydraulic power units inside fairings under the lower wing surface. The circular-section fuselage was liberally covered with access doors and hatches. The nose was just one of several contrasting answers tested by Sukhoi to the problem of fitting radar into a supersonic fighter. The fire-control system was to be one of the Uragan (Hurricane) family, with the search scanner at the top of the nose and the Almaz (Diamond) ranging radar underneath inside the inlet. The main scanner was inside a low-drag radome in the form of a flattened cone (with a curious upward tilt) from which projected the PVD-7 instrumentation boom combining the pitot/static heads with pitch and yaw vanes. Additional instrument booms were mounted inboard of each wingtip. Even though the T-3 was to be a supersonic aircraft there seemed no alternative to making the radome over the ranging set a bluff hemi- sphere, which had an adverse effect on pres- sure recovery in the air inlet. The latter

S U K H O I T-3 A N D PT-7

immediately divided into left and right ducts which quickly expanded into vertically sym- metric ducts along each fuselage wall. These combined behind the cockpit into a circular tube passing above the wing and then ex- panding to fill virtually the entire fuselage cross-section to mate with the face of the en- gine compressor at Frame 29. Between Frames 31 and 32 on each side of the top of

Below: Two views of T-3.

the fuselage was a large grilled aperture through which hot air could be violently ex- pelled from the compressor during engine start. At Frame 32 a bolted joint enabled the entire rear fuselage to be removed for servic- ing or changing the engine. At Frame 38 were hinged four door-type airbrakes with large slot perforations. At Frame 43 were the skewed pivots for the horizontal tailplanes, each of which was a single-piece 'slab' with a leading-edge sweep of 60° and an anti-flutter mass projecting forwards near each tip. The large fin curved away from a dorsal extension

in which a screwed panel gave access to the power unit driving the rudder, which was hung on three inset hinges. Each tail sur- face had chem-milled skins attached to ribs at 90° to the surface rear spar. The fuselage tail end was mainly of titanium. The nose landing gear had a 660 x 200 tyre and retract- ed forwards. Each main unit had an 880 x 230 tyre and, unlike the swept-wing Sukhois, re- tracted straight inwards. Track was 4.65m (15ft Sin) and wheelbase 5.05m (16ft 7in). The cockpit housed an ejection-seat and had a bulletproof windscreen and one-piece

S U K H O I T-3 A N D PT-7

frameless canopy sliding to the rear. Among the comprehensive avionics suite were two items with antennas in the top of the fin, the slots for the Svod (Arch) navaid and SOD-57 transponder and the RSIU-5V inside the di- electric fin cap. The wings were plumbed for drop tanks, to be carried on pylons only just in- board of the instrument booms. The planned armament was two guns (Sukhoi assumed the NR-30), and steel blast panels were pro-

vided in the sides of the forward fuselage. Be- fore the T-3 was completed the guns were re- placed by missiles. The intended weapon was the K-6, to be carried on interfaces attached where the tanks would have been.

The PT-7 differed mainly in having an area- ruled fuselage, with a visibly waisted middle section, and a new ranging radar with a point- ed downward-inclined radome projecting from the bottom of the nose. Other differences

included unperforated airbrakes and a revised fin-cap antenna which extended around the top of the slightly shortened rudder.

These aircraft were the first in what proved to be a long succession of prototype and ex- perimental aircraft in the search for the best interceptor. This underscored the Soviet Union's determination to accept nothing but the best, because any of these aircraft could have been accepted for production.

Dimensions (T-3)

Span 8.7 m Length (inc instrument boom) 18.82 m Wing area (net) 24.9 m!

Weights Empty Loaded (normal) Maximum Performance Maximum speed at 10 km (32,808 ft) Service ceiling Range (internal fuel)

(maximum) 7,490kg 9,060 kg 11,200kg 2,100 km/h 18km 1,440km 1,840km 28ft6!fln 61 ft m in 268.8ft2 16,512 Ib 19,974 Ib 24,691 Ib 1, 305 mph (Mach 1.98) 59,055 ft 895 miles 1,1 43 miles Take-off and landing runs,

both about 1,100m 3,600 ft

Dimensions (PT-7)

Span 8.7m 28ft6^in Length (inc instrument boom) 18.82 m 61 ft 8% in Wing area (net) 24.9m2 268.8ft2

Weights

In each case approximately 150 kg (331 Ib) heavier than the T-3

Performance Maximum speed

at 1 0 km (32,808 ft) 2,250 km/h 1 ,398 mph (Mach 2. 1 2)

Top: The T-3 at the 1956 Tushino Fly Past. Bottom: PT-7 inlet.

S U K H O I T-3 A N D PT-7

T-3

T-3

T-5

S U K H O I T-49

Sukhoi T-49

Purpose: To create a further-improved interceptor.

Design Bureau: OKB-51 of P O Sukhoi, Moscow.

In May 1958 the OKB-51 decided that, after more than four years of effort, they had still not found the best answer to the problem of how to arrange the radar, air inlet(s) and ar- mament of a single-engined supersonic inter- ceptor. It was recognized that guided missiles would be carried externally, probably under the wings, leaving the nose free for radar, but the engine inlet still posed a problem. The PT-8 and T-47 had large radars centred in a nose inlet, and this was considered to de- grade the aerodynamics. Accordingly a new arrangement was devised, and the OKB con- veniently were able to graft it on to the in- complete T-39 (T-3 derivative). The result

thus received the designation T-49. By June 1958 work on the T-39 had been stopped, and this project was transferred as a test-bed to the Central Institute of Aviation Motors. Conversion to the T-49 was completed by Oc- tober 1958. In 1959 M Goncharov was ap- pointed to supervise flight testing, but the T-49 remained on the ground - much of the time being used for various tests - until in January 1960 it was flown by Anatoly Koznov. He re- ported outstanding acceleration and good all- round performance, but by this time aircraft in this class had been overtaken by later tech- nology. In April 1960 the T-49 was damaged in an inflight accident, and though it was re- paired it never flew again.

The T-49 was by virtue of its ancestry very similar to the simpler versions of T-4 family aircraft such as the production Su-9. Like that aircraft it was intended to be armed with two

guided missiles carried on pylons under the outer wings, but these would have been of the K-8 type as carried by the Su-11. The large fixed radome was uncompromised by the in- lets, which were located well back on each side. In side elevation each inlet was vertical, seen from the front it formed a 90° segment curved round the side of the fuselage, and in plan it was swept back at 60°. To match pres- sure recovery over the whole range of flight Mach numbers the inner wall was made vari- able in angle and throat area. The intention was to make the whole inlet system isentrop- ic (causing no change in entropy) to achieve maximum compression of the airflow. Like several other Sukhoi designs of the period there were two vertical doors in each side of the fuselage at Frame 7 to spill excess air from the ducts. The engine was a Lyul'ka AL-7F-100, with a dry rating of 6,900kg (15,212 Ib) and maximum afterburning thrust of 9,900kg (21,82515). This was achieved without the need for the injection of water, the T-39's rear-fuselage water tank being re- placed by one for fuel. Other features includ- ed steel doubler plates left over from the T-39 near where gun muzzles would have been had they been fitted, tailplanes fitted with anti-flutter masses and driven over the ex- ceptional angular range +97-16°, and flaps whose trailing-edge roots were cut away at 45°, which was also a feature of the pro- duction Su-11.

This promising aircraft was overtaken by galloping technology.

Dimensions (Broadly similar to PT-7) Length 19.8m No other data.

64 ft m in

S U K H O I T-49

S U K H O I P - l