Category Soviet x-plenes

Purpose: To meet an IA-PVO demand for a high-performance automated interception system.

Design Bureau: OKB-51 ofP O Sukhoi, Moscow.

In late 1957 the threat of USAF strategic bombers able to cruise at Mach 2 (B-58) and Mach 3 (B-70) demanded a major up­grade in the PVO defence system. At the start of 1958 a requirement was issued for manned interceptors with a speed of 3,000km/h (l,864mph) at heights up to 27km (88,583ft). Mikoyan and Sukhoi responded. Creation of the T-3A-9 interception system was autho­rised by the Council of Ministers on 4th June 1958. The air vehicle portion of this system was a derivative of the T-3 designated T-3A, and with the OKB-51 factory designation T-37. Detail design of this aircraft took place in the first half of 1959. In February 1960 the single flight article was approaching completion when without warning the GKAT (State Com­mittee for Aviation Equipment) terminated the programme and ordered that the T-37 should be scrapped. The role was temporari­ly met by the Tu-128 and in full by the MiG-25P.

Though derived from the T-3 the T-37 was an entirely new aircraft which, because of aerodynamic guidance by CAHI (TsAGI) and the use of the same type of engine, had more in common with the MiG Ye-150. The T-3A-9 system comprised this aircraft plus the Looch (ray) ground control system, the ground and airborne radars, a Barometr-2 data link, Kremniy-2M (silicon) NPP (sight) system and two Mikoyan K-9 (R-38) missiles. The aircraft had a wing which was basically a strength­ened version of the T-3 wing, with no dog­tooth and with anhedral increased to 3° (ie, -3° dihedral). Each flap could be extended out on two rails to 25° and did not have an inner corner cut off at an angle. A more im­portant change was that to avoid scraping the tail on take-off or landing the main landing gears were lengthened, which meant that the wheels were housed at an oblique angle in the bottom of the fuselage. The fuselage was totally new, with a ruling diameter of 1.7m (12ft 7in). This was dictated by the Tumanskii R-l5-300 afterburning turbojet, with dry and reheat ratings of 6,840kg (15,080 Ib) and 10,150kg (22,380 Ib) respectively. The TsP-1 radar was housed in a precisely contoured radome whose external profile formed an Os – watitsch centrebody with three cone angles to focus Shockwaves on the sharp inlet lip. The whole centrebody was translated to front and rear on rails carried by upper and lower inlet struts. Surplus air could be spilt through two powered doors in each duct outer wall at Frame 8. The pressurized cockpit had a KS-2 seat and a vee windscreen ahead of a low- drag upward-hinged canopy with a metal­skinned fixed rear fairing. The detachable rear fuselage was made mainly of welded ti­tanium, and terminated in an ejector sur­rounding the engine’s own variable nozzle. Initially a sliding ring, this ejector was changed to an eight-flap design during proto­type manufacture. Ram air cooling inlets

were provided at Frames 25 and 29, and in the detachable rear section were four door-type airbrakes. Under this section were two radial underfins, each incorporating a steel bumper. Pivoted 140mm (51/2in) below mid­level the tailplanes had 5° anhedral and did not need anti-flutter rods as they were irre­versibly driven over a range of ±2°. Each main landing gear had levered-suspension carrying a plate-braked KT-89 wheel with an 800 x 200mm tyre. The long nose gear had a power – steered lower section with a levered-suspen – sion K-283 wheel with a 570x140mm tyre, and retracted backwards. A total of 4,800 litres (1,056 Imperial gallons) of fuel could be housed in three fuselage tanks (No 3 being of bladder type) and Nos 4 and 5 between wing spars 2 and 3. Provision was made for a 930 litre (204.6Imperial gallon) drop tank. Missile pylons could be attached ahead of the ailerons. Avionics included the radar, RSIU – 5A vhf/uhf with fin-cap antennas, RSBN-2 Svod (arch) navaid and SOD-57M transpon­der (both with fin slot antennas), Put (course) longer-range navaid, MRP-56P marker receiv­er, SRZO-2 Khrom-Nikel (chrome-nickel) IFF, Lazur (azure) beam/beacon receiver of the Looch/Vozdukh (rising) ground control sys­tem, KSI compass system and a ventral blade antenna for the flight-te st telemetry.

Like the rival Mikoyan Ye-150 series (which were produced more quickly) this weapon system was overtaken by later designs.

Dimensions

Span 8.56 m 28 ft 1 in

Length overall 1 9.4 1 3 m 63ft8!iin

Wing area (gross) 34 m2 366 ft2

(net) 24.69 m2 265.8ft2

Weights

Empty 7,260kg 16,005Ib

Loaded (normal) 1 0, 750 kg 23,699 Ib

(maximum) 12 tonnes 26,455 Ib

Performance (estimated)

Max speed at 15 km (49,21 3 ft) 3,000 km/h Service ceiling 25-27 km

Range 1,500km

(with external tank) 2,000 km

Two artist’s impressions of a T-37.

sors and loggers, computers, oscilloscopes and many kinds ofinstrumentation, overseen by a test and research crew which usually numbers five. The flight crew typically num­bers three. Among the engines tested are the NK-86, D-18T and PS-90A turbofans, and the D-236 and NK-93 propfans. One of the pho­tographs shows a former IL-76M used for test­ing large turbofans of the D-18 family. The other shows a former civil IL-76T used to test the TV7-117S turboprop and its six-blade Stupino SV-34 propeller. The propeller blades are heavily strain-gauged, the instrumenta­tion cable being led forward from the tip of the spinner.

Another Ilyushin aircraft used in significant numbers as an experimental test-bed is the IL-18. Possibly as many as 30 have been used, mainly at the Zhukovskii and Pushkin test centres, for upwards of 50 test programmes. Nearly all are basically of the IL-18D type, powered by four 4,250hp AI-20M turboprops. The most famous ofthese aircraft is the IL-18 No75442, named Tsyklon (cyclone). Instantly recognisable from its nose boom like a joust­ing lance, this meteorological research air­craft is equipped with something in excess of 30 sensors used to gether data about atmos­pheric temperature, pressure and pressure gradient, humidity, liquid and solid particu­late matter (including measurement of droplet and particle sizes) and various other factors which very according to the mission. The sensors extend from nose to tail and from tip to tip. Other IL-18 and IL-18D aircraft have helped to develop every kind of radar from fighter nosecones to giant SLARs (slide-look­ing airborne radar) and special mapping and SAR (synthetic-array radar) installations.

Top: IL-76LL with TV7-1 ITS Centre: Nose of IL-18 Tsyklon Bottom: Tu-134 radar testbed

Opposite page, bottom: IL-76LL with D-18T

A small number based at Pushkin tested the main radars and pointed radomes of super­sonic aircraft, though this was done mainly by the Tu-134.

Total production of the Tu-134 passenger twin-jet was 853. Of course, the majority were delivered to Aeroflot and foreign customers, but a few went to the WS. From the mid – 1970s aircraft built as passenger transports began to be converted for use as military crewtrainers, including the Tu-134BUformil – itary and civil pilots to Cat IIIA (autoland) stan­dard, Tu-134Sh for navigators and visual bomb aimers (actually dropping bombs to FAB-250 (551 Ib) size), Tu-134BSh for Tu-22M

navigators andbomb-aimers, and Tu-134UBL for Tu-16 0 pilots. These are not experimental, nor is the Tu-134SKh with comprehensive navaids and avionics for worldwide land-use and economic survey. On the other hand at least 15 aircraft were converted for equip­ment testing and research. One has flown over 6,000 hours investigating the behaviour of equipment and Cosmonauts underweight­less (zero-g) conditions. Several have been fitted with nose radars under development for other aircraft, including the installations for the Tu-144, Tu-160 and MiG-29. With the designation IMARK, aircraft 65906 has tested the Zemai polarized mapping radar able to operate on wavelengths of4, 23, 68 or 230cm (from Am to 7ft 7in). Arrays ofantennas look down and to the right side from the starboard side of the fuselage and a large ventral con­tainer. A generally similar but more versatile test aircraft is 65908. This is based at Zhukovskii together with a Tu-134 fitted with a giant parachute in the tail for emergency use during potentially dangerous research into deep-stall phenomena, which caused the loss of several aircraft with T-tails and aft-mounted engines.

Photographs show two other aircraft from the many hundreds used in the former Soviet Union for special tests. One shows an IL-28 used for research into the design, materials and behaviour of skis on different kinds of surface. A large ski mounted under the bomb bay near the centre of gravity could be rammed down against the ground by hy­draulic jacks. On the ski were test shoes of different sizes, shapes and materials. The other photograph shows the Yak-25 test-bed fitted on the starboard side with the engine in­stallation proposed for the Yak-28, with a sharp lip and moving central cone. Ahead of it was a water spray rig for icing trials.

Purpose: To improve BICh-7, the next stage beyond BICh-3.

Design Bureau: B I Cheranovskii.

BICh followed his Type 3 with the impressive BICh-5 bomber, powered by two BMW VI en­gines, but never obtained funds to build it. In 1929 he flew the BICh-7, almost a 1.5-scale re­peat of BICh-3 with two seats in tandem. The problem was that he replaced the central tail by rudders (without fixed fins) on the wingtips, and the result was almost uncon­trollable. He modified the aircraft into the BICh-7A, but was so busy with the BICh-11 and other projects that the improved aircraft did not fly until 1932. Apart from returning to a central fin and rudder he replaced the cen­treline wheel and wingtip skids by a conven­tional landing gear. The BICh-7A gradually became an outstanding aircraft. Testing was done mainly by N P Blagin (later infamous for colliding with the monster Maksim Gorkii), and he kept modifying the elevators and ailerons until the aircraft was to his satisfac­tion.

This larger ‘parabola-wing’ aircraft was again made of wood, veneer and fabric, with various metal parts including the convention­al divided rubber-sprung main landing gears and tailskid. The tandem cockpits were en­
closed, which in 1932 was unusual. The en­gine was a l00hp Bristol Lucifer, and one of the unsolvable problems was that the Lucifer was notorious for the violence of the firing strokes from its three cylinders, which in some aircraft (so far as we know, not includ­ing the BICh-7A) caused structural failure of its mountings.

This aircraft appears to have become an unqualified success, appearing at many air – shows over several years.

Purpose: To use aircraft to test experimental landing gears.

Design Bureau: Various.

No country has as much real estate as the for­mer Soviet Union, and the land surface is at times soft mud, sand, snow and hard frozen. Several designers concentrated on devising landing gears that would enable aircraft to operate from almost any surface. One of the first was N A Chechubalin, who in the 1930s was working at BRIZe, a division of Glavsev – morput’, the chief administration of northern (Arctic) sea routes. He devised neat tracked main gears to spread the load and enable air­craft to operate from extraordinarily soft sur­faces. His experimental gears were tested on a U-2 and a much heavier Polikarpov R-5.

In 1943 SAMostovoi picked up where Chechubalin had left off and designed cater­pillar main landing gears for an Li-2 transport (the Soviet derivative of the DC-3) These gears were retractable, and made little differ­ence to the performance of the aircraft, but they were ‘unreliable in operation’ and were therefore not put into production. Pho­tographs have not yet been found.

In 1937 Nikolai Ivanovich Y efremo v collab­orated with Aleksandr Davidovich Nadiradze
to design a unique inflatable gear which of­fered a totally different way of reducing foot­print pressure in order to operate from almost any surface. Their answer was an ‘air pillow’ inflated under a semi-rigid upper sheet at­tached under the aircraft centreline. The scheme was called SEN, from the Russian for ‘Aircraft Yefremov/Nadiradze’. The pillow was tested on a Yakovlev AIR-20 (UT-2), which was fitted with a 20hp motorcycle en­gine driving a compressor to keep the bag in­flated. The only known photo does not show the wingtips clearly, so it is not known if wingtip skids were needed to stop the aircraft rolling over. In 1940 the SEN was test-flown by such famous pilots as Gromov, Shelest and Yumashev, but it never went into general use.

In 1991 the new private company Aeroric, at Nizhny Novgorod (in Communist days called Gorkii), began the design of amultirole transport called Dingo. Powered by a 1,100- shp Pratt & Whitney Canada PT6A-65B turbo­prop, driving a Hartzell five-blade pusher propeller, the Dingo is made mainly of light alloy and accommodates one or two pilots and up to eight passengers or up to 850kg (1,8741b) of cargo. Its most unusual feature is that it has no conventional landing gear. In­stead it has a 250hp Kaluga TBA-200 (in effect
a turbofan) which generates an air cushion underneath, contained by inflated air blad­ders along each side and hinged flaps at front and rear. At full load the ground pressure is a mere 0.035kg/cm2 (71.71b/ft2), enabling the Dingo to ride over water, snow or any other surface and to cross ditches, ledges and pro­jections up to 30cm (1ft) high. Cruising speed is275km/h(170mph).

Though a surface skimmer rather than an aeroplane, the Stela M.52 seen at the 1995 Zhukovskii airshow was interesting for riding on an air cushion. This is contained by side skegs (underfins), a large rear flap and front hinged curtains.

Purpose: To evaluate a fighter with a variable-incidence wing.

Design Bureau: Zhukovskii WA, Soviet air force academy; design team led by Professor S G Kozlov.

Kozlov was perpetually seeking after new targets, and one that he had considered for many years was the pivoted wing, able to change its angle of incidence. Thus, for ex­ample, the aircraft could take off or land with a large angle of attack yet with the fuse­lage level. Four Russian designers had made unsuccessful variable-incidence aircraft in 1916-17. Design of the El (Eksperimentalnyi Istrebitel, experimental fighter) began in 1939. Under Kozlov’s direction the wing was designed by V S Chulkovand the landing gear by M M Shishmarev. D O Gurayev was assis­tant chief designer, and S N Kan and IA Sverdlov handled the stressing. The single El was constructed at a factory in the Moscow district, but its completion was seriously de­
layed, mainly by technical difficulties and re­peated alteration of the drawings. At last the El was almost complete in autumn 1941, but on 16th October the factory was evacuated. The El and all drawings were destroyed.

The El was said to have been a good-look­ing single-seat fighter, powered by a 1,650hp M-107 (VK-107) liquid-cooled engine. The fuselage was a Duralumin stressed-skin semi- monocoque of oval section, with heavy ar­mament around the engine. The wings had spars with steel T-booms and Duralumin webs, with glued shpon (Birch veneer) skin. The wing was fitted with flaps and differential ailerons, and was mounted on ball-bearing trunnions on the front spar and driven by an irreversible Acme-thread jack acting on the

While no illustration has been found of the El, this 1940 drawing recently came to light showing a fighter project with a more powerful engine (M-106P) and greater span.

rear spar. To avoid problems it is believed the main landing gears were attached to the fuse­lage and retracted into fuselage compart­ments. No other details survive.

There is no reason to believe that the El would not have met its designer’s objectives, but equally it had little chance of being ac­cepted for production. The only successful variable-incidence aircraft was the Vought F8U (F-8) Crusader.

Dimensions

Span 9.2m 30 ft 2K in

No other data.

This designation applied to the MiG-19 fitted with a booster rocket engine in a pod under­neath. Whereas previous mixed-power fight­ers had been primarily to test the rocket, the SM-50 was intended as a fast-climbing fighter, able very quickly to intercept high-flying bombers. The first SM-50 was a MJG-19S fitted with a removable ventral pack called a U-19 (from Uskoritel’, accelerator). Made at the MiG OKB, this was basically formed from two tubes arranged side-by-side with a nose fair­ing. It contained an RU-013 engine from L S Dushkin’s KB, fed by turbopumps with AK-20 kerosene and high-test hydrogen per­oxide. The pilot could select either of two thrusts, which at sea level were 1,300kg (2,866Ib) or 3,000kg (6,614Ib). To avoid the rocket flame the aircraft’s ventral fin was re­placed by two vertical strake-fins under the engines (which were RD-9BM turbojets with variable afterburning thrust but unchanged maximum rating). The first SM-50 began factory testing (incidentally after the Ye-50, and long after the first MiG-21 prototypes) in December 1957. Despite a take-off weight of 9,000kg (19,841 Ib) a height of 20,000m (65,617ft) was reached in under eight min­utes with the rocket fired near the top of the climb, boosting speed to l,800km/h (1,118mph, Mach 1.695). Dynamic zoom ceil­ing was estimated at 24,000m (78,740ft). Five pre-production SM-50s were built at Gor’kiy, but they were used only for research.

SM-12

Early in the production of the MiG-19 it was re­alised that the plain nose inlet was aerody­namically inefficient at supersonic speeds, and that a properly designed supersonic inlet would enable maximum speed to be signifi­cantly increased without any change to the engines. By the mid-1950s the OKB was well advanced with the prototypes that led to the MiG-21 and other types, all ofwhich had inlets designed for supersonic flight. In fact produc­tion of the MiG-19 in the Soviet Union was quite brief – it was left to other countries to discover what a superb fighter it was – and all had the original inlet. A total of four SM-12 (plus two derived) aircraft were built, with the nose extended to terminate in a sharp­lipped inlet. As in standard MiG-19s, across the inlet was a vertical splitter to divide the airflow on each side of the cockpit. This was used to support a conical centrebody whose function was to generate a conical shock­wave at supersonic speeds. For peak pres­sure recovery, to keep the shock cone focussed on the lip of the inlet the cone could be translated (moved in or out) by a hydraulic ram driven by a subsystem sensitive to Mach number. A similar system has been used on all subsequent MiG fighters, though the latest types have rectangular lateral inlets. SM-12/1 was powered by two RD-9BF-2 engines with a maximum rating of 3,300kg (7,275 Ib). SM – 12/2, /3 and /4 were powered by the R3-26, with a maximum rating of 3,800kg (8,377 Ib). All four SM-12 aircraft were fitted with im­proved flight control systems, wing guns only and new airbrakes moved to the tail end of the fuselage. A fifth aircraft, designated SM-12PM, was fitted withpylons fortwo K-5M guided missiles, which were coming into production as the RS-2U. This required a guid­ance beam provided by an RP-21 (TsD-30) in­terception radar. The scanner necessitated a greatly enlarged nosecone, which in turn demanded a redesigned forward fuselage with hardly any taper. Both guns were re­moved, and there were many other modifi­cations. The sixth and final version was the SM-12PMU, armed with two or four RS-2U missiles. This aircraft was intended to inter­cept high-altitude bombers faster than any other aircraft, so it combined two R3-26 en­gines with the U-19D rocket package. Numer­ous MiG-19 variants served as armament test-beds, mainly for guided missiles.

Purpose: Improved version of IS-1 Design Bureau: OKB-30, chief designer V V Shevchenko

The initial funding allocated to Shevchenko’s project actually paid for two prototypes. Though construction of both began in parallel it was soon decided to incorporate improve­ments in the dubler (second aircraft). Desig­nated IS-2, and also known as the I-220t>/s, this emerged from GAZ No 156 in early 1941. Surviving documents differ. One account states that the IS-2 ‘was ready in January 1941…the War broke out and only four test flights were carried out.’ Three other ac­counts, in Russian, French and English, state that the aircraft was completed in April 1941 but had not flown when the Germans invad­ed. Shavrov is non-committal, but notes that all performance figures are estimates. The
walk-round outdoor photos were all taken with snow on the ground.

The IS-2 was a refined derivative of the IS-1. The engine was an M-88 14-cylinder radial rated at l,100hp, neatly installed in a long – chord cowl with a prominent oil-cooler duct underneath and driving a VISh-23 propeller with a large spinner, but retaining Hucks starter dogs. According to Podol’nyi, the fuse­lage cross-section was reduced (which is certainly correct) and, while wing spans re­mained the same, chord was reduced in order to increase aspect ratio and reduce area. Shavrov and a French author state that the wings of the IS-1 and IS-2 were geometri­cally identical. What certainly was altered was that the landing-gear retraction system was replaced by simply connecting the main legs to the wing linkage, so that a single cock­pit lever and a single pneumatic jack folded
the lower wings and the main landing gears in a single movement. It is widely believed that the IS-2 was not intended to fly in combat as a biplane, the benefits being restricted to take-off and landing. In the IS-1 documenta­tion the idea that the aircraft might be operat­ed as a biplane is never mentioned. Ifit were, then what was the point of the folding lower wing? Further modifications in the IS-2 were that the tail was redesigned, the tailwheel could retract and the two inboard ShKAS were replaced by heavy 12.7mm Beresin BS guns.

By the time this aircraft appeared, even though it looked more modern than its pre­decessor, the WS was fast re-equipping with simple monoplane fighters. These unques­tionably stood more chance against the Luft­waffe than the IS-2 would have done.

Views of IS-2.

Sukhoi T-58VD Posted by admin in Soviet x-plenes on November 9, 2015 Purpose: To provide full-scale STOL jet-lift data to support the T6-1. Design Bureau: OKB-51 of P O Sukhoi, Moscow. Early history of the T6-1 (see page 178) re­volved around how best to create a formida­ble tactical aircraft with a short field length. One of the obvious known methods of mak­ing a STOL (short take-off and landing) air­craft was to fit it with additional jet engines arranged vertically to help lift the aircraft at low speeds. In January 1965 the T-58D-1, the first prototype ofwhat was to become the Su – 15 interceptor, was taken off its normal flight programme and returned to an OKB factory. Here it was modified as the T-58VD, the des­ignation meaning Vertikalnyye Dvigateli, ver­tical engines. Managed by R Yarmarkov, who had been leading engineer throughout T-58D testing, ground running trials of the VD began in December 1966. This work required an enormous test installation built at the OKB-51 which used a 15,000hp NK-12 turboprop to blast air at various speeds past the T-58VD while it performed at up to full power on all five engines. It was mounted on a special platform fitted with straingauges to measure the thrust, drag and apparent weight. When these tests were completed, the T-58VD was taken to the LII at Zhukovskii where it began its flight-test programme on 6th June 1966. Initial testing was handled by Yevgenii Solov’yov, who was later joined by the OKB’s Vladimir Ilyushin. On 9th June 1967 this air­craft was flown by Solov’yov at the Domodye – dovo airshow, where NATO called it ‘Flagon-B’. Its basic test programme finished two weeks later. It then briefly tested the ogi­val (convex curved) radome used on later Su – 15 aircraft and the UPAZ inflight-refuelling pod. It was then transferred to the Moscow Aviation Institute where it was used as an ed­ucational aid. The original T-58D-1 was built as an out­standing interceptor for the IA-PVO air-de­fence force, with Mach 2.1 speed and armament of K-8M (R-98) missiles. Powered by two R-l 1F2S-300 turbojets (as fitted to the MiG-21 at that time), each with a maximum afterburning rating of 6,175kg (13,6131b), it had pointed delta wings with a leading-edge angle of 60°, fitted with blown flaps. The wings looked very small in comparison with the fuselage, which had backswept rectangu­lar variable-geometry engine inlets on each side. To convert it into the T-58VD a com­pletely new centre fuselage was spliced in. This used portions of the original air ducts to the main engines but separated them by new centreline bays for three lift jets. The front bay housed a single RD-36-35 turbojet of P A Kolesov design with a thrust of 2,300kg (5,1801b). One of the wing main-spar bulk­heads came next, behind which was a bay housing two more RD-36-35 engines in tan­dem. Each bay was fireproof and fitted with all the support systems shown to be needed in previous jet-lift aircraft. On top were large louvred inlet doors each hinged upward at the rear, while underneath were pilot-con­trolled cascade vanes for vectoring the lift-jet thrust fore and aft. Another important modifi­cation was to redesign the outer wing from just inboard of the fence, reducing the lead­ing-edge sweep to 45° and extending the aileron to terminate just inboard of the new squared-off tip. Apart from the missile pylons This page and opposite top: Views of T-58VD, one showing its final use at the MAI.   military equipment was removed, and a new telemetry system was fitted with a distinctive twin-blade antenna under the nose. The jet-lift conversion reduced take-off speed and ground run from 390km/h (242mph) and 1,170m (3,839ft) to a less fran­tic 290km/h (ISOmph) and only 500m (1,640ft). Landing speeds and distances were reduced from 315km/h (196mph) and 1,000m (3,281ft) to 240km/h (149mph) and 600m (1,969ft). This was achieved at the ex­pense of reduced internal fuel capacity and sharply increased fuel consumption at take­off and landing. Moreover, it was discovered during initial flight testing that the longitudinal locations of the three lift engines had been miscalculated. Operation of the front RD-36- 35 caused a nose-up pitching moment which the pilot could not counteract at speeds below about 320km/h (199mph), so this lift engine could not be used on landings. T-58VD   Vakhmistrov Zveno Posted by admin in Soviet x-plenes on November 9, 2015 Purpose: To enable a large aircraft to carry one or more small ones long distances, for example to attack targets that would otherwise be out of reach. Design Bureau: Not an OKB but engineer Vladimir Sergeyevich Vakhmistrov working at the LII (flight research institute). In 1930 Vakhmistrov suggested that a cheap glider might be used as an aerial gunnery tar­get, and he quickly perfected a way of carry­ing such a glider above the upper wing of an R-l reconnaissance aircraft and releasing it in flight. This gave Vakhmistrov the idea ofusing a large aircraft to carry a small one on long – range flights over hostile territory. The small aircraft could either be fighters to protect a large bomber, or bomb-carrying attack air­craft or camera-carrying fast reconnaissance aircraft which could make a pass over a target while the parent aircraft stood off at a safe dis­tance. In each case the difficult part was hook­ing on again for the long flight home. After presenting the WS and LII management with calculations Vakhmistrov received permis­sion to try out his idea. This led to a succes­sion of Zveno (link) combinations: Z-l This featured a twin-engined Tupolev TB-1 bomber carrying a Tupolev I-4 fighter above each wing. The fighters were of the I-4Z ver­sion, three of which were converted for these experiments with short stub lower wings and attachment locks on the landing gear and under the rear fuselage. The bomber was pro­vided with attachments for the Zveno aircraft above each wing: two small pyramids for the landing gear and a large tripod for the rear – fuselage attachment. The first flight took place from Monino on 3rd December 1931. The TB-1 was flown by AI Zalevskii and A R Sharapov, with Vakhmistrov as observer. The fighters, with ski landing gears, were flown by V P Chkalov and A S Anisimov. The take-off was made with the fighter engines at full power. The TB-1 copilot forgot the release sequence and released Chkalov’s axle before releasing the aft attachment, but Chkalov reacted instantly and released the rear lock as the fighter reared nose-up. The second fighter was re­leased correctly. For a few seconds the TB-1 flew with no tendency to roll with an I-4Z on one wing. Z-la First flown in September 1933, this comprised the TB-1 carrying two Polikarpov I-5 fighters. The latter were fitted with a reinforcing plate under the rear fuselage carrying the rear hold­down, but had no special designation. The pi­lots were P M Stefanovskii (TB-1) and I F Grodz’ and V K Kokkinaki (I-5). Z-2 This was the first of the more ambitious hook­ups using a TB-3 as parent aircraft. The bomber was an early TB-3/4 M-l 7, and it was given attachments for an I-5 above each wing and a third above the fuselage with its wheels on a special flat platform. On the first test in August 1934 the TB-3 was flown by Zalevskii and the fighters by T P Suzi, S P Suprun and T T Al’tnov. Z-3 This combination would have hung a Grig – orovich I-Z monoplane fighter under each wing of the TB-3. It was not flown. Z-4 No information. The complete sequence of Zveno developments (not all were tried).   Z-5 This was the first attempt to hook back on. The parent aircraft was again the TB-3/4 M-l 7, and the fighter was an I-Z fitted with a large suspension superstructure of steel tubes, plus a curved upper guide rail terminating in a sprung hook releasable by the pilot (almost identical to the arrangement used on the air­ship-borne US Navy F9C Sparrowhawks). This was designed to hook on a large steel-tube trapeze under the bomber, which was folded up for take-off and landing. V A Stepanchy- onok flew the I-Z on several tests with the bomber flown as straight and level as possible by Stefanovskii. The first hook-on took place on 23rd March 1935; this was a world first. Z-6 The final combination of the original series was the mating oftwo I-16 monoplane fighters hung under the wings ofthe TB-3. The fighters were provided with local reinforcement above the wings to enable them to be hung from sliding horizontal spigots on large tripod links of streamlined light-alloy tube pin-joint­ed to the bomber’s wing structure. Bracing struts linked the bomber to a latch above the fighter’s rear fuselage, and one ofthe fighters (M-25A-engined No 0440) was photographed with a lightweight pylon above the forward fuselage to pick up under the bomber’s wing. The first test took place in August 1935; Ste – fanovskii flew the TB-3 and the fighter pilots were K K Budakov and AI Nikashin. Aviamatka Named ‘mother aircraft’, this amazing test, not part of the original plan, took place in No­vember 1935. The TB-3/4M-17 took off from Monino with an I-5 above each wing and an I-16 below each wing. At altitude it folded down the under-fuselage trapeze and Stepan – chenok hooked on the I-Z, making a combi­nation of six aircraft of four types all locked together. After several passes all the fighters released simultaneously. By this time Vakhmistrov had schemes for up to eight fighters of later types all to be carried by large aircraft such as the full-scale VS-2 tailless bomber projected by Kalinin. Instead Stalin’s ‘terror’ caused the whole effort to wither, but there were still to be further developments. SPB (Russian initials for fast dive bomber) This was a special version of the Polikarpov I-16 equipped with a rack to carry an FAB-250 (bomb of 250kg, 551 Ib) under each wing. Such an aircraft could not have safely taken off from the ground. In 1937 a later TB-3/4AM – 34RN was made available, and two SPB air­craft were hung under its wings. The first test took place on 12th July 1937, the TB-3 being flown by Stefanovskii and the dive bombers by A S Nikolayev and IA Taborovskii. Z-7 In November 1939 one final combination was flown: the TB-3/4AM-34RN took off with an I – 16 under each wing and a third hooked under the fuselage in flight (with severe difficulty). The I-16 pilots were Stefanovskii, Nyukhtikov and Suprun. In early 1940 the WS decided to form a Zveno combat unit. Based at Yevpatoriya, this was equipped with six modified TB-3/4AM – 34RN and 12 SPB dive bombers. During the Great Patriotic War a famous mission was flown on 25 th August 1941 which destroyed the Danube bridge at Chernovody in Roma­nia, on the main rail link to Constanta. Surviv­ing SPBs flew missions in the Crimea. BICh-8 Posted by admin in Soviet x-plenes on November 9, 2015 Purpose: To test the use of wingtip rudders. Design Bureau: B I Cheranovskii. Few details of this machine have survived. It was built and tested in 1929. Cheranovskii was so distressed by the failure of the BICh-7 that he built this simple glider to see ifwingtip rudders could be made to work. The BICh-8 was dubbed T reoogol’nik (little triangle). It had an open cockpit and centre­line skid. The wing was built as a centre sec­tion, integral with the nacelle, and outer panels fitted with inboard elevators, outboard ailerons and wingtip rudders with inset hinges mounted on small fins. This machine may have flown satisfactori­ly, because Cheranovskii repeated tip rud­ders in the BICh-11. 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