Category Soviet x-plenes

Tupolev Tu-2 Experimental Versions

Tupolev Tu-2 Experimental Versions
Tupolev Tu-2 Experimental Versions

Purpose: To use Tu-2 aircraft for various experimental purposes.

Design Bureau: Originally, CCB-29 (or TsKB-29) and GAZ (Factory) No 156.

Created during A N Tupolev’s period in de­tention under a ludicrously false ‘show trial’ charge, the Tu-2 (previously ‘Aircraft 103’, but really the 58th ‘ANT’ design), was an out­standing multirole tactical bomber. Its ridicu­lous gestation, with its creator working on a drawing board in a locked cell, meant that it did not enter service until May 1942, but de­spite this some 3,300 were delivered from Factories 156, 166 and 125. As soon as spare examples became available they were snapped up for use as test-beds. The very first series aircraft, No 100716, was used to test the ASh-83 engine, rated at l,900hp, driving four-blade AV-5V propellers (replacing the standard 1,850hp ASh-82FN driving the three – blade AV-5V-167 or four-blade square-tip AV-9VF-21K). Maximum speed of this test­bed was 635km/h (395mph) at 7,100m (23,294ft).

Numerous test versions appeared in 1944, including the first two of three Shturmovik (armoured ground attack) versions with spe­cial armament, all proposed by Tupolev’s ar­mament brigade leader A D Nadashkevich. The first, actually given the designation Tu-2Sh, had its capacious weapon bay occu­pied by a specially designed aluminium box housing 88 modified PPSh-41 infantry ma­
chine carbines (sub-machine guns). These fired standard 7.62mm pistol ammunition, and all fired together pointing obliquely down at a 30° angle. The obvious shortcoming was that, even though the drum magazines held 71 rounds, they were quickly emptied.

The second 1944 Sh version had a massive 75mm gun under the fuselage, reloaded by the navigator. Two more ground-attack ver­sions appeared in 1946. The first had the dev­astating forward-facing armament of two 20mm ShVAK, two NS-37 and two NS-45. The 37mm gun was 267mm (101/2in) long and weighed 150kg (33lib). The 45mm version had a shorter barrel but still fired its 1.065kg (2.35 Ib) projectiles at 850m (2,790ft) per sec­ond, and weighed 152kg (335 Ib).

The last of these variants was the two-seat RShR, or Tu-2RShR. This was a dedicated anti-armour aircraft, carrying a high-velocity 57mm RShR automatic cannon with the bar­rel projecting ahead of the metal-skinned nose and fitted with a prominent recoil brake.

The most startling modification was the Tu-2 Paravan (paravane). Two of these were built, to test a crude way of surviving impact with barrage-balloon cables. A special cable woven from high-tensile steel was run from one wingtip to the other via the end of a monocoque cone projecting over 6m (20ft) ahead of the nose. The nose and wingtips were reinforced. First flown in September 1944, this lash-up still reached 537km/h (334mph) despite the strange installation and
a 150kg (331 Ib) balancing weight in the tail. These trials were not considered to have been successful.

Yet another 1944 modification was the Tu-2K (Katapult), fitted with test ejection – seats. The first Tu-2K fitted the test seat in the navigator’s cockpit just behind the pilot. A second ejection-seat tester had the experi­mental seat mounted in an open cockpit at what had been the radio operator’s station in the rear fuselage.

In early 1945 the Type 104 radar-intercep­tion system began flight testing (the first to be airborne in the Soviet Union). The system had been designed from 1943, by a team led by A L Mints, and the Type 104 test aircraft had begun flighttesting on 18th July 1944 but with the vital radar simulated by ballast. The pilot had a modified sight, which was later linked to the radar, and fired two VYa-23 cannon in­stalled under the forward fuselage. The rear fuselage was faired over and contained noth­ing but a balancing mass.

The designation Tupolev Tu-2G was ap­plied to several Gruzovoi (cargo) conver­sions. It appears that all of these were experimental, carrying special loads either in the remarkably large bomb bay or slung ex­ternally, and in many cases the load was dropped by parachute. No fewer than 49 GAZ – 67b armoured reconnaissance cars were dropped, the Tu-2G in this case being limited to a height of 6km (19,685ft) and a speed of 378km/h (235mph).

As explained in the stories of the Pe-2 and Pe-8 experimental versions, the German Fi 103 (‘V. 1’) flying bomb was the basis for a large Soviet programme of air-launched cruise missiles in the immediate post-war era. One ofthe later variants was the 16Kh Pri – boi (surf, breaking waves). The fact this was fitted with twin engines meant that it could be carried under the Tu-2. The first modified Tu-2 launch aircraft began testing at LII on 28th January 1948, and live missile launchings took place on the Akhtuba range between 22nd July and 25th December 1948, testing the D-312 and D-14-4 engines and various electric or pneumatic flight-control systems. The Tu-2 launch aircraft continued in the
process of refining guidance and improving reliability until at least 4th November 1950, by which time the Tu-4 was being modified as carrier aircraft with one missile under each outer nacelle. The WS rejected the 16Kh on grounds of poor accuracy, and eventually the argument reached Stalin who shortly before his death terminated this missile.

Experimental Tu-2 aircraft were also used to develop air-refuelling.

Not least, in the immediate post-war era the Tu-2 was the most important aircraft con­verted to air-test turbojet engines. Occasion­ally the designation Tu-2LL (flying laboratory) was used, but one of the most important was (possibly unofficially) designated Tu-2N,
because it was allocated to test the imported Rolls-Royce Nene. This required the test engine to be mounted in a nacelle of large diameter (basic engine diameter 1.26m, 4ft 11/2in). Later more than one Tu-2 was used to test Soviet RD-45 and VK-1 derivatives of the Nene, including variants with an afterburner. However, these were all preceded by aircraft, some of which had been Tupolev Type 61 prototypes, which were converted to test cap­tured German axial engines: the BMW 003A (Soviet designation RD-20) and the Junkers Jumo 004B (Soviet designation RD-10). An­other 61 prototype was used to test the first Soviet turbojet to fly, the Lyul’kaTR-1, in 1946.

Belyayev 370, EOI

Purpose: Experimental fighter.

Design Bureau: V N Belyayev, working at GAZ (factory) No 156, Moscow.

This EOI (Eksperimental’nyi Odnomestnyi Istrebitel’, experimental single-seat fighter) was proposed in early 1939, and personally approved by Stalin in August of that year. De­sign and manufacture proceeded through 1940, and at the German invasion of 22nd June 1941 the first flight was only a few months away.

In October the Moscow factories were evacuated. It was decided to abandon the project, and the part-complete EOI, drawings and calculations were destroyed. When pho­tographs of the FBI (see above) were discov­ered it was at first thought that this must be the same aircraft. In fact, there was little sim­ilarity between the two designs apart from the basic configuration.

The EOI had the cockpit in the nose, almost perfectly streamlined, with armament in the same location. Possibly for the first time in history, Belyayev designed the entire front section of the aircraft to be separated in emergency, so that the pilot would not have to bail out ahead of the propeller. The latter was to be driven by a Klimov M-105 engine, rated at l,100hp and fitted with a TK-2 tur­bocharger. In the original scheme, like fight­ers of 1917 by Gallaudet in the USA and Dufaux in France, the propeller was to have a large-diameter hub through which passed a tube carrying the rear fuselage. Some of the ‘370’ drawings are reproduced overleaf. One shows the proposed cockpit, armament of two underfloor VYa-23 cannon and location of the cartridge-severed attachments. Anoth­er drawing shows the unique arrangement in which the wing was to be provided with a slat. This auxiliary surface was normally
housed in a recess immediately ahead of the flap or aileron. For take-off and landing it was to be swung down and forward to adopt a leading-edge-down attitude ahead of the leading edge of the wing. Thus, it was a bold­er precursor of today’s Krueger flap. Whether or not this aerodynamically powerful idea was abandoned is unknown, but Belyayev certainly abandoned the original rear fuse­lage. By late 1939 he had decided to use con­ventional twin tail booms. The specification overleaf applies to this revised scheme.

According to one document it was intend­ed that a production version should have had the M-106 engine. This would have been rated at 1,350hp, instead of 1,100hp. Whether the unconventional configuration, and espe­cially the potentially dangerous slat system, would have shown to advantage will never be known.

Sketch drawings of 370

 

Belyayev 370, EOI

11.4m 37 ft 5 in

19 nf 205ft2

700km/h 435 mph

 

On take-off and landing

Belyayev 370, EOI

 

Model of the final EOI configuration.

 

Belyayev 370, EOIBelyayev 370, EOIBelyayev 370, EOI

Bolkhovitinov S

Purpose: Ultra-fast attack bomber.

Design Bureau: WIA (air force engineering academy) located at the Zhukovskii Academy, Moscow, where Viktor Fedorovich Bolkhovitinov was Professor of Aircraft Design and head of design team.

The objective was to make the fastest bomber in the world, by using a fighter-type layout with two powerful engines in tandem. This arrangement was adopted in order to achieve engine-out safety with minimum drag. Design of the propulsion system began in 1936 and of the aircraft itself a year later. The designation stood for Sparka (Twin), but other designations were S 2M-103 (in usual Soviet style, showing the engines), BBS-1 (short-range bomber, fast, the S here mean­ing Skorostnii, speedy) and LB-S (light bomber, twin). Construction of the single pro­totype began in July 1938, the first flight was made by B N Kudrin in late 1939, and NIl-WS testing took place between March and July 1940, the pilots being Kudrin and AIKa – banov. It was found that take-off run was ex­cessive. In 1940-41 the aircraft was subjected to major modifications. ZI Itskovich re­designed the wing with increased area and a changed aerofoil profile. A different front en­
gine was fitted, and the rear engine and its propeller were replaced by an inert mass. The oil coolers were incorporated in the main radiator duct. As the redesigned aircraft neared completion snow was still on the ground, and the landing gears were all re­placed by fixed skis.

No way was found to make proper use of the bay previously occupied by the rear en­gine, and in any case performance was now unimpressive. After the German invasion work was abandoned. Plans for an improved S bomber and a derived I (or I-1) fighter with two M-107 engines were also dropped.

The airframe was entirely a modern light – alloy stressed-skin structure. The wing was based on a structural box with two plate spars with flanged lightening holes, sheet ribs and heavy upper and lower skins with flush rivet­ing. The fuselage basically comprised top, bottom and side panels all joined to four strong angle-section longerons (Shavrov: ‘later this construction was used for the IL-28’, a post-war jet bomber). The twin-finned tail had thin Dl skin throughout, the rudders hav­ing inset balanced hinges, the tailplanes being pivoted and driven by irreversible trim­ming motors and the elevators having trim tabs and a variable geared drive. Each main
landing gear retracted electrically back­wards, the wheel turning through 90°.

The 960hp M-103 engines (V-12 liquid – cooled derived from the Hispano-Suiza 12Y) were mounted in tandem, the rear engine dri­ving the rear unit of the contra-rotating six – blade propeller. Some reports state that the drive was taken via left/right twin shafts past the front engine’s crankcase, but in fact (as in the Italian Macchi M. C.72 racing seaplane of 1933) the rear engine drove a single shaft be­tween the front-engine cylinder blocks which finally passed through the centre of the front – engine propeller shaft. Both engines were served by a large ducted radiator with a con­trollable exit flap (this was positioned by one of the 29 on-board electric actuators) and two oil coolers were fitted in ducts on each side of the front engine. Four fuel tanks were housed between the wing spars, and on the trailing edge were electrically driven slotted flaps (in several reports, incorrectly called Fowler

type).

Pilot and navigator sat in tandem, far apart under a long Plexiglas canopy. The navigator also had a bomb sight, and the entire area around his seat was skinned in Plexiglas. Turning to the rear he could fire a 7.62mm ShKAS, and it was the intention later to re-

Подпись:

place this by twin 12.7mm UBT. Behind the rear spar, under the pilot’s cockpit, was a bay housing 400kg (882 Ib) of bombs, with two electrically driven doors. It was the intention later to fit fixed guns in the wings.

The second wing, of NACA-230 profile, gave improved field length. One report states that a remotely controlled ShKAS was added in the extreme tail, but this does not appear in any known photographs. Continued poten­tially dangerous problems with the rear en­gine and its drive resulted in this being removed. The front engine was changed to an M-l 05P, ofunchanged 960hp, driving a sin­gle three-blade propeller. Even with weight considerably reduced the S was then judged a failure, though tandem-engine studies con­tinued. The factory was tooled up for Pe-2 production.

Though an article by Ing V Mikhailov and Ing VPerov states that, following initial Nil testing ‘the design team was instructed to continue development’, there is no doubt the S was always on the verge of success but never getting there. The high wing loading and the failure to solve the rear-engine drive problem made it one of the programmes abandoned after the invasion of June 1941.

Dimensions

Span (original)

11.38m

37 ft 4 in

(new wing)

12.2m

40 ft X in

Length (original)

13.2m

43 ft 4 in

(one engine)

13.0m

42ft73/iin

Wing area (original)

22.9 m2

246.5ft2

(new wing)

23.43m2

252.2 ft2

S (as built)

Bolkhovitinov S

 

Bolkhovitinov S

S (as built).

 

Bolkhovitinov S

S (as built).

 

Bolkhovitinov S

S (as built).

 

Bolkhovitinov S

S (converted to single engine).

 

Kostikov 302, Ko-3

Kostikov 302, Ko-3

Purpose: Simple jet (rocket + ramjet) fighter.

Design Bureau: RNII (reaction-engine scientific research institute) and OKB No 55.

By 1940 the idea ofthe PVRD (ramjet) was fa­miliar in the Soviet Union, mainly to boost the speed of piston-engined fighters. In 1940 Pro­fessor Mikhail Tikhonravov, on the RNII staff, had the better idea of making a simpler and lighter fighter with a ZhRD (liquid-propellant rocket) in the tail and PVRDs under the wings. This could put together various thing s already developed in the Soviet Union to create what might have been a cheap and quickly pro­duced fighter which, apart from short range and endurance, would have had outstanding performance. Unfortunately, perhaps be­cause it appeared unconventional, this pro­ject suffered from endless argument and foot-dragging, finally falling victim to a deci­sion to abandon all such aircraft. According to Shavrov, ‘The proposal did not attract any ob­jections from A G Kostikov, Director of the RNII. It was continued as a preliminary pro­ject, and approved by the Technical Council of the RNII in spring 1941. It was later exam­ined by a commission of specialists at the WA’ (air force academy). This commission, comprising S A Christianovich, A V Chesalov, S N Shishkin, V I Polikovskii and others, pro­claimed that This project does not bring out anything new’. Work proceeded at a snail’s pace, and Kostikov then took the proposal to the NKAP (state commissariat for aviation in­dustry), where Tikhonravov defended it on 17-18th July 1942. In No vember 1942 Ko stiko v showed the proposal to K E Voroshilov, and eventually Stalin himself gave authority for work to resume, appointing Kostikov chief designer. From this time onwards many doc­uments called the project ‘Ko-3’. Funding was
provided for two prototypes, and to build these the RNII set up OKB-55, appointing as director M R Bisnovat (see earlier) and A A Andreyev as his deputy. Tikhonravov did the aerodynamic calculations, while stress­ing was in the hands of V D Yarovitskii. By spring 1943 two 302 aircraft were almost completed. Testing in the T-104 tunnel at CAHI (TsAGI) began at this time. In 1943 the original proposed ramjets were changed to a new design by Vladimir Stepanovich Zuyev. These were initially tested in a half-scale form, but full-scale testing was never carried out. After much argument it was decided to forget the ramjets and complete the aircraft as the 302P (Perekhvatchik, interceptor) with the rocket only. The PVRD attachments under the wings were faired over, and the wing span reduced. This was flight-tested as a glider at the LII from August 1943, towed to altitude by a North American B-25 and Tu-2. The as­signed pilot was initially S N Anokhin, fol­lowed by M L Gallai and B N Kudrin, with V N Yelagin as test engineer. The 302P was found to be ‘exceptionally good, stable and pleasant to fly’, and in March 1944 the second 302P was being tested in the T-104 tunnel at CAHI. In the same month the whole pro­gramme was cancelled. A recent Russian magazine article about the 302 omits any mention ofTikhonravov.

The 302 was made mainly of wood, with a monocoque fuselage and smooth skin of

Delta and Shpon veneers bonded by Bakelite – type plastics. The wings had 15-per-cent RAF.34 profile at the root, tapering to 8-per­cent NACA-230 near the pointed tip. In con­trast, the control surfaces were of Dl alloy with fabric covering, the starboard aileron, rudder and both elevators having trim tabs. The rocket engine was a Dushkin/Shtokolov D-1A with a main chamber rated at 1,100kg (2,4251b) at sea level and a cruise chamber rated at 450kg (992 Ib). Under the wings were to have been installed the ramjets, but infor­mation on these Zuyev units is lacking. Their nacelles were to have been oval, with the major axis horizontal, faired neatly into the wing. The all-rocket 302P had tanks for 1,230kg (2,712 Ib) of RFNA (concentrated ni­tric acid) and 505kg (1,113 Ib) of kerosene. The cockpit, which was to have been pres­surized, had a canopy hinged to the right and a bulletproof windscreen and frontal armour. The main and tailwheel landing gears were to have been retracted hydraulically, and the same system would have operated the split flaps. No documents have been found de­scribing how the environmental and hy­draulic systems would have been energised. Two 20mm ShVAK cannon were to have been mounted in the nose and two more in the bottom of the forward fuselage, each with 100 rounds. In addition, there was to have been provision for underwing racks for RS-82 or RS-132 rockets or two FAB-125 bombs.

Top: 302 with PVRD engines. Below: Two views of302.

Kostikov 302, Ko-3

 

Подпись: Dimensions (302) Span (302) 11.4m 37 ft Min length (excluding guns) 8.708m 28 ft &, in wing area (302) 17.8m2 192ft2
Kostikov 302, Ko-3

With the benefit of hindsight this appears to 302P in CAHI (TsAGl) wind tunnel. have been a considerable case of ‘might have been’. Kostikov was a political animal who saw in Tikhonravov’s proposal a means to gain advancement and power. Instead, in 1944 a commission headed by A S Yakovlev found him responsible for the failure of the 302 to develop on schedule; he was dis­missed from his post and later imprisoned.

Подпись: Weights Empty (302) 1,856kg 4,092 Ib Loaded not stated, but about 3,800 kg 8,377 Ib Performance Max speed at sea level, 800 km/h 497 mph at altitude 900 km/h 559 mph Time to climb to 5 km 2.1 min (16,404ft) to 9 km 2.8 min (29,528 ft) Service ceiling 18km 59,055ft Range 100km 62 miles Take-off in 16 seconds at 200 km/h 124 mph Dimensions (302P) Span 9.55m 31 fl 4 in Length (excluding guns) 8.708m 28 ft 6% in Wing area 14.8m2 159ft2 Weights Empty 1,502kg 3,31 lib Loaded 3,358kg 7,403 Ib Performance The only measured figure for the 302P was a landing speed of 115 km/h 71.5 mph 302P

Kostikov 302, Ko-3

Kostikov 302, Ko-3

Below: 302P inboard profile.

 

Above: 302 with PVRD engines.

 

Kostikov 302, Ko-3

MiG-17 Experimental Versions

Design Bureau: OKB-155 ofAI Mikoyan.

Throughout 1949 the MiG OKB was busy cre­ating the SI, the prototype of a MiG-15 deriva­tive incorporating numerous improvements. Most of these were aerodynamic, including a completely redesigned wing, a horizontal tail of increased sweep on an extended rear fuse­lage, and improved flight controls. The first flight article, SI-2, was flown on 13th January 1950, and on 1st September 1951 MAP Order No 851 required the SI to be put into produc­tion as the MiG-17. Because of the sheer mo­mentum of MiG-15 production the improved aircraft did not replace it in the factories until October 1952. The following specification refers to the MJG-17F, by far the most impor­tant version, which was powered by the af­terburning VK-1F, with a maximum rating of 3,380kg (7,451 Ib).

Dimensions Span Length Wing area

9.628 m 11.26m 22.64 m2

31 ft 7 in 36 ft 1 Min 243.7 ft2

Weights

Empty

3,940kg

8,686 Ib

Fuel/oil

1,170kg

2,579 Ib

Loaded (clean)

5,340kg

1 1,772 Ib

(maximum)

6,069 kg

13,380 Ib

Performance Maximum speed

at sea level

l,100km/h

684 mph

at 3,000m (9,842 ft)

l,145km/h

71 1.5 mph

Mach limit

(clean over 7,000m)

1.15

22,966ft

Time to climb (afterburner)

to 5,000 m

l. Smin

16,404ft

to 10,000m

3.7 min

32,808ft

Service ceiling

(still climbing 3.6 m/s)

16,600m

54,462 ft

Range (clean)

1,160km

721 miles

(maximum)

1,940km

1,205 miles

Take-off speed/

235km/h

146 mph

run

590m

1,936ft

Landing speed/

180km/h

112 mph

run

850m

2,789 ft

SN

In late 1953 the MiG Factory 155 produced an experimental fighter representing the next stage beyond the SU. This time the entire for­ward fuselage was redesigned to house the pivoted guns, the engine being fed by lateral inlets and ducts passing both above and below the wing torsion box (which was given front and rear fairings). Ahead of Frame 13 the entire nose was occupied by the SV-25 ar­mament installation devised by the TKB (Tula design bureau) of Afanas’yev and Makarov. This was based on a large frame mounted on needle-roller bearings on each side and piv­oted on a transverse axis over the range +27° 267-9° 28′ (not 9° 48′ as previously pub­lished). On this frame were mounted three TKB-495 lightweight 23mm guns, fed by box magazines mounted on the fixed structure. The whole installation weighed 469kg (l,0341b), requiring a balancing increase in the size of Tank 3 in the rear fuselage. As this

MiG-17 Experimental VersionsПодпись: Two different SDK-5s. Подпись:MiG-17 Experimental Versions

aircraft was so non-standard anyway the OKB took the opportunity to try a few other changes. Of course a special gunsight was needed, and it may have been to improve the optics that a new windscreen was designed, wider and longer than before and giving a bet­ter field of view ahead. The SN was factory – tested by Georgiy K Mosolov from mid-1953. It proved a failure, with seriously reduced flight performance and useless armament. Because the guns were so far ahead of the centre of gravity and centre of pressure of the aircraft, firing them at large angles from the horizontal caused powerfulpitchingmoments which threw the aim off-target. Mikoyan de­cided the problem was not readily soluble. Numerous otherwise unmodified MiG-17s were also used as armament test-beds.

SI-10

This MiG-17 was one of the original type with the non-afterburning VK-1A engine, with call­sign 214. Having studied the wing and tail of the F-86E Sabre, this aircraft was fitted with important aerodynamic and control changes. The wing was fitted with large automatic slats over the outer 76 per cent of each leading edge, large area-increasing (Fowler-type) flaps, and spoilers (called interceptors) under the outer wings which opened whenever the adjacent aileron was deflected more than 6°. In addition, a fully powered irreversible tailplane was fitted, with limits of +37-5°, re­taining the elevators driven by a linkage to add camber. Grigorii A Sedov flew No 214 on 27th November 1954, followed by many other OKB and NIl-WS pilots. Opinions were favourable, especially regarding the horizon­tal tail, but it was not worth disrupting MiG-17 production to incorporate the changes.

NIAI RK, LIG-7

Purpose: To evaluate an aeroplane with a wing of variable area.

Design Bureau: NIAI, Leningrad.

In 1936 Grigorii (according to Shavrov, Georgii) Ivanovich Bakshayev, aged 18, joined the UK GVF, the instructional combine of the civil air fleet. He was eager to test his belief that a su­perior aeroplane could be created by arrang­ing for it to have a large wing for take-off and landing and a smaller wing for cruise. As the UK GVF was in Leningrad the NIAI adopted the idea. Called RK (Razdvizhnoye Krylo, ex­tending wing), and also LIG-7 because it was the seventh project of the Leningrad Institute GVF, the aircraft was built quickly and was first flown in August 1937. Remarkably, the
system worked smoothly and reliably (better in the air than on the ground), and it led to the evenmore unconventional RK-I fighter.

Apart from the wing the RK was a simple monoplane of mixed construction, with en­closed cockpits for a pilot and observer and powered by an uncowled l00hp M-l 1 engine driving a laminated-wood propeller. It had a two-spar wing of constant narrow-chord M-6 profile, braced by pairs of wires above and below to the top of the pilot’s hood and to a pyramid truss under the fuselage. At the root was what looked like the root section of a much larger wing, with CAHI (TsAGI)-846 aerofoil profile, but with a span of only 50cm (1ft 7%in). Inside this, nestling tightly like a set of Russian Matroshka dolls, were five further
plywood wing sections each of 50cm span. The observer could crank these out by a cable mechanism, each adding 45cm (1ft 5%in) to the span of the large-chord region. It took 30 to 40 seconds to crank the telescopic sections out to their full extent, covering 60 per cent of the semi-span, and 25 to 30 seconds to wind them back.

Seemingly a ‘crackpot’ idea, the RK per­formed even better than prediction. It is diffi­cult to account for the fact that it got nowhere. The answer must be that it introduced an el­ement of complexity and possible serious danger, sufficient to dissuade any later de­signer from following suit.

NIAI RK, LIG-7
NIAI RK, LIG-7

Purpose: To create a fighter with variable wing area.

Design Bureau: NIAI, Leningrad.

From the start of his telescopic-wing studies young Bakshayev had really been thinking about fighters. He had regarded the RK mere­ly as a preliminary proof-of-concept exercise. He calculated that a fighter able to retract most of its wing area and powered by the M – 105 engine ought to be able to reach a world – record 800km/h (497mph), overlooking the fact that a fighter with a relatively small wing would have poor combat manoeuvrability. Indeed, as described below, he found a way to make the relative difference between the small and large wings even greater than in the RK, the ratio of areas being 2.35:1. In October 1938 he submitted a preliminary design sketch for the RK-I (Russian abbreviation for extending-wing fighter). After much argu­ment the concept was accepted by CAHI (TsAGI) and the WS. A one-fifth-scale model was tested in a CAHI (TsAGI) tunnel from Jan­uary 1939, but it was difficult to find an indus­trial base capable of building even the prototype. Worse, the RK-I attracted the at­tention of Stalin, who took a keen interest in combat aircraft. Excited, he demanded that this aircraft should use the M-106 engine, the most powerful then on bench test. Under
some difficulty a prototype RK-I was com­pleted in early 1940, but the M-106 engine (later designated VK-106) was still far from ready. The aircraft could have flown with the M-105, but nobody dared to fit anything but the engine decreed by Stalin. In order to do at least some testing a full-scale model was con­structed with the nose faired off, fixed landing gears and a projecting canopy, with no at­tempt to simulate armament or the radiator ducts in the rear fuselage. This mock-up was then tested in the CAHI (TsAGI) full-scale tun­nel. The resulting test report was generally favourable, but noted that sealing between the telescopic wing sections was inadequate. The CAHI (TsAGI) aerodynamicists neverthe­less concluded that with the M-106 the speed might be 780km/h (485mph). Lacking an en­gine the project came to a halt, and after the German invasion in June 1941 it was aban­doned. Bakshayev was appointed to super­vise increased production of the 156km/h (97mph) U-2 (Po-2) at Factory No 387.

The lifting surfaces of the RK-I were unique, and quite unlike anything attempted by any other designer. The aircraft was all-metal, the large fuselage being a light-alloy monocoque which would have housed the 1,800hp M-106 in the nose with the oil cooler underneath and surrounded by two 20mm ShVAK can­non and two 7.62mm ShKAS machine guns.

Behind the firewall were successively the fuel tanks, backwards-retracting single-strut main landing gears, enclosed cockpit and the gly­col coolant radiator with controllable air ducts on each side of the rear fuselage. The amazing feature was that there were two wings of equal span and narrow tapering chord, one in front of the cockpit and the sec­ond, set at a slightly lower level, behind. Each had upper and lower skins of spot-welded SOKhGSA stainless steel, and the rear wing was fitted with three hinged trailing-edge sur­faces on each side serving as flaps and ailerons. These movable surfaces, like the tail, were made of light alloy. The unique fea­ture was that on this aircraft the root of the large wing extended completely around the front wing and back almost to mid-chord of the rear wing. Nested inside it were 14 further wing profiles, which in 14 seconds could be winched out over the entire span by an elec­tric motor and cable track along the rear wing leading edge, which was at right angles to the longitudinal axis. Each section of the large wing comprised a Dural leading edge and rib with a fabric skin, the first section sealing the side of the fuselage in the high-speed condi­tion and serving as a wing end-plate in the ex­tended low-speed configuration. Shavrov gives the weight of all 28 telescopic sections as approximately 330kg (727.5 Ib). Changing

RK-800

 

to the large-area configuration was intended to have no significant effect on the rod-oper­ated flight controls, a fact confirmed by CAHI (TsAGI). Bakshayev left drawings showing that a production aircraft would have had only nine larger telescopic sections, and vari­ous other changes.

Had an M-106 engine been available this aircraft might have flown. Pilots would then have been able to assess whether (as seems doubtful) the ability to fly with much less wing

 

Dimensions

Span

Length

Wing area (large) (small)

 

area than needed for take-off and landing really offered any advantage to an aircraft designed to engage in close combat.

 

8.2m

26 ft 10s/, in

8.8m

28 ft 1014 in

28.0m2

301 H2

11.9m2

128ft2

not recorded

3,100kg

6,834 Ib

 

Weights

Empty

Loaded (estimate)

 

Performance (estimated)

Max speed (small wings) 780 km/h 485 mph

Endurance 2 hrs 27 min

Landing speed (large wing) 115 km/h 7 1.5 mph

 

Sketches of RK-I showing its two configurations.

NIAI RK, LIG-7

 

NIAI RK, LIG-7NIAI RK, LIG-7

Sukhoi T-49

Подпись: Dimensions (Broadlysimilarto PT-7) Length 19.8m 64 ft m in No other data. Sukhoi T-49

Purpose: To create a further-improved interceptor.

Design Bureau: OKB-51 ofP 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 ar­mament of a single-engined supersonic inter­ceptor. 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 de­grade the aerodynamics. Accordingly a new arrangement was devised, and the OKB con­veniently were able to graft it on to the in­complete 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 Oc­tober 1958. In 1959 M Goncharov was ap­pointed 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 re­ported outstanding acceleration and good all­round performance, but by this time aircraft in this class had been overtaken by later tech­nology. In April 1960 the T-49 was damaged in an inflight accident, and though it was re­paired 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 in­lets, 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 pres­sure recovery over the whole range of flight Mach numbers the inner wall was made vari­able 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 re­placed by one for fuel. Other features includ­ed 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 ex­ceptional angular range +97-16°, and flaps whose trailing-edge roots were cut away at 45°, which was also a feature of the pro­duction Su-11.

This promising aircraft was overtaken by galloping technology.

This page and opposite top: Three views of T-49.

Sukhoi T-49

 

Sukhoi T-49

Sukhoi T-49

Tupolev Tu-4 Experimental Versions

Purpose: To use Tu-4 aircraft for various experimental purposes.

Design Bureau: OKB-156 of A N Tupolev.

In The Great Patriotic War the Soviet Union had no modern strategic bomber. Stalin cast covetous eyes on the Boeing B-29, and told Tupolev and Myasishchev to design aircraft in the same class. However, in 1944 three intact B-29s fell into Soviet hands and it was decid­ed just to copy them. Tupolev was given two years to do this immense task. The first air­craft to appear was the Tu-70 transport, which actually used the wing, engines and pro­pellers of one of the B-29s. The production bomber was designated Tu-4, and had Soviet ASh-73TK engines of2,400hp (more powerful than the B-29 engine) and a totally new defensive system with guns of 12.7mm (1st Series), 20mm (from the 8th Series) or 23mm calibre (from the 15th Series). Total produc­tion was close to 1,000. Several Tu-4 aircraft were used in air-refuelling experiments.

The Tu-4T was a single unpressurized trans­port conversion which initially was used for trials with 28 paratroops. In 1954 a small number
of 52-seat versions, again called Tu-4T, were built for the VTA (military transport aviation).

Several Tu-4K conversions were used as carrier aircraft for trials with the Mikoyan KS-1 cruise missile, for use chiefly against ships. This 3 tonne (6,614 Ib) turb ojet-engined weapon was a miniature swept-wing aero­plane with radar guidance (see page 101). The Tu-4K played a major role in the devel­opment of the entire Kompleks (electronic system) which after being cleared for pro­duction was installed in the Tu-16KS, which was the operational carrier of these missiles. Several Tu-4s were used for trials with other missiles, the earliest being with captured FilOS (so-called V-l) pulsejet cruise missiles captured in 1944-45. From March 1945 the Soviet X-10 (Kh-10) copy was on test, and numerous examples were launched from ground ramps and from Tu-2, Yer-2 and Pe-8 aircraft. In 1947 the Tu-4 became available, and several were used to test the 14Kh-l and twin-engined 16Kh, but all this work petered out by July 1955 and none of these missiles entered service.

At least 12 Tu-4s were used as engine test­
beds. Some of the early examples tested tur­boprops, of which the most startling were the three aircraft whose No 3 (starboard inner) engines were replaced by TV-12 turboprops. Take-off power ofthis single-shaft engine was initially ll,995hp, or almost six times that of the engine it replaced. The colossal thrust, which in the Tu-4 could not all be used, was transmitted by a pair of AV-60 co-axial pro­pellers each with four broad blades of 5.6m (18ft 41/2in) diameter. Later this unique pow – erplant was developed into the NK-12M of nearly 15,000hp for the Tu-95 and Tu-142. Other turboprops tested included the ex­Junkers TV-2, Klimov VK-2 (TV-4), Kuznetsov NK-2 and NK-4, and the Ivchenko AI-20, one AI-20 installation (for the Ilyushin 18) having the thrust line and jetpipe above the wing and the other (for the Antonov 10 and 12) having the thrust line and jetpipe below the wing. Jet engines tested under the fuselage of Tu-4LL aircraftincludedtheNene, AL-5,AL-7,7Fand 7P, AM-3 (RD-3), AM-5 and 5F, VD-5, VD-7, VK-2, VK-7 and VK-11.

Tu-4test-bedforNK-12turboprop.

Tupolev Tu-4 Experimental Versions