Category Soviet x-plenes

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.

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.

Purpose: To continue stratospheric-flight research with an aircraft superior to BOK-1. Design Bureau: Bureau of Special Design, Smolensk. Chief designer Chizhevskii.

Design of this aircraft began in 1936. The Tupolev RD was again used as the starting point, but with features intended to enable greater heights to be reached. The test pilots were Petrov and Stefanovskii. According to Shavrov the BOK-7 was first flown in 1938, and ‘showed the same characteristics as the BOK-1’. Several two-man crews, including such important long-distance pilots as Gro­mov, Yumashev, Danilin, Spirin, Baidukov, Belyakov and others, spent periods of several days sealed in the GK checking all aspects of human life in preparation for proposed high- altitude long-distance flights in the BOK-15. According to some historians the ultimate ob­jective was a high-altitude circumnavigation, and that the by-function designation of this aircraft was K-17, from Krugosvetnyi (round the world). Photographs originally thought to be of the BOK-7 are now known to show the BOK-11.

The BOK-7 had the full-span wing of the RD, and aft-retracting landing gears, but com­pared with the RD the legs were redesigned for much lighter gross weight, and fitted with single wheels. Attention was concentrated on the fuselage, which unlike the BOK-1 had the GK (pressure cabin) integral with the air­frame, the centre fuselage being a slim cylin­der sealed by gaskets and adhesives, and with grommets fitting round the control wires and other services passing through apertures in the wall. The normal oxygen supply to the pilot and pilot/observer ‘compensated for the insignificant amount of air escaping’. The sealed drum was fitted with two hemispheri­cal domes, the front with eight and the rear with six transparent portholes so that the oc­cupants could see out, with a better view than from the BOK-1. The GK was kept at pressure by a tapping from a centrifugal PTsN (super­charger) blower driven by step-up gears from the engine. The engine was an 890hp M-34FRN fitted with two TK (turbosuper­chargers). It is probable that these delivered compressed air to the PTsN which then fed the engine, the cabin supply being taken off a small bleed pipe. Shavrov states that ‘all sys­tems worked well’, and that the experiments were ‘very interesting’.

According to Shavrov this aircraft had ‘the first GK of the combined type’ with both a sealed compartment kept under pressure and an oxygen supply. Some accounts state that AI Filin at the NIl-WS worked out details of the proposed circumnavigation, in 100- hour stages, but that the project was aban­doned after he was arrested in 1939 and executed in Stalin’s Terror of 1940. This air­craft led to the BOK-8, BOK-11 and BOK-15, but it appears that no illustrations of it have been discovered.

Purpose: To test the guidance system of a cruise missile.

Design Bureau: OKB-155 ofAI Mikoyan.

In late 1947 the Kremlin ordered the develop­ment of a large cruise missile which could be launched (primarily against ships) from the Tu-4. Because of the importance of this pro­ject it was assigned to a joint team formed by OKB No 155 (MiG) and a new semi-political group called SB-1 (Special Bureau Nol). The OKB assigned one of the founders, M I Gure­
vich, as titular head, but the Chief Designer was A Ya Bereznyak who has figured previ­ously on page 29 of this book. Head of SB-1 was S L Beria, son ofthe formidable Politburo member who in 1953 succeeded Stalin. In fact, SB-1 faded from the scene, as it had little to contribute, though it did have P N Kusenko as Chief Designer. Under intense pressure a swept-wing turbojet-engined missile was created, which later went into production as the KS-1 Komet. In early 1949 its guidance sys­tem was tested in an Li-2 (Soviet derivative of
the DC-3), and later in that year a more repre­sentative system was tested in the FK (also called MiG-9L, Laboratoriya). This was too large to be carried aloft by a Tu-4, so it for­mated with the Tu-4 parent aircraft and thence simulated the missile on its flight to the target. Subsequently this aircraft was used to test different cruise-missile guidance systems, assisted by the K-l, a manned ver­sion of the KS-1 missile.

Aircraft FK was a modified MiG-9 twin-jet fighter, the first type of turbojet aircraft to fly in

the Soviet Union. Features included a straight-tapered wing oflaminar profile of9% thickness with large slotted flaps and Frise ailerons, a pressurized cockpit ahead of the wing, a ground-adjustable tailplane mounted part-way up the fin, a nosewheel retracting forwards and main landing gears retracting outwards, and a nose inlet feeding air to two RD-20 turbojets (Soviet copies of the German BMW 003A, each rated at 800kg, l,7641b, thrust) mounted under the wing with jet noz­zles under the trailing edge. The final produc­tion series had an ejection-seat, and the FK was from this batch. The heavy nose arma­ment of three NS-23K guns and all armour
were removed, and the fuselage was extend­ed by splicing in an extra section accommo­dating an unpressurized rear cockpit with a side-hinged canopy for the guidance-system operator. As in the Komet, the missile’s radar dish antenna was mounted above the nose, and a receiver antenna was mounted on the leading edge of each wing. Above the fin was a streamlined container housing the aft-fac­ing transmitter and receiver antennas for the radio-command guidance from the parent aircraft after launch. Once the autopilot had set the correct course the nose radar homed on the parent’s radar signals reflected back from the target. Nearer the target the missile’s
own radar became active, steering by signals received by the leading-edge antennas.

So far as is known, the FK played a valuable role in the development of one of the world’s first turbojet cruise missiles. So did the KSK, a piloted version ofthe missile itself.

Dimensions (FK)

Span 10.0m 32ft9Kin

Length 10.12m 33 ft 2 in

Wing area 18.2m2 195.9ft2

No other data.

Purpose: To exceed Mach 1 and possibly serve as the basis for a fighter.

Design Bureau: P O Sukhoi, Moscow.

Note: this aircraft was not related to later aircraft with the same designation.

In late 1947 the Council of Ministers issued a plan for 1948-49 calling for the construction of new experimental aircraft. One type was to research high-subsonic, transonic and low supersonic speeds, and also if possible pro­vide the basis for the design of a supersonic tactical fighter. Contracts were issued to Yakovlev (Type 1000) and Sukhoi (Aircraft R). In each case funds were provided for one flight article and one static test specimen, and Sukhoi’s design proceeded rapidly. From the outset provision was made for two heavy can­non, and in 1949 the WS designation Su-17 was issued. As early as July 1949 the flight ar­ticle was taken to LIl-MAP at Zhukovskii, where the assigned pilot, Sergei Anokhin, car­ried out increasingly fast taxi tests. Just as he was about to make the first flight the Su-15 radar-equipped interceptor suffered violent flutter and crashed, Anokhin ejecting. Rather precipitately, CAHI (TsAGI) blamed Sukhoi, and moreover claimed that the wing of Air­craft R was also torsionally weak and would flutter at high airspeeds. CAHI therefore re­fused to issue flight clearance for this aircraft. In turn this led Stalin to order that Sukhoi’s OKB should be liquidated on 1st November 1949. It was reopened in 1953 after Stalin’s death.

This outstanding design was made possi­ble by the rapid development of the powerful TR-3 (later called AL-5) afterburning axial tur­bojet by A M Lyul’ka, qualified in January 1950 at4,600kg (10,141 Ib), with a dry rating of 4 tonnes (8,8181b). Had the Su-17 continued it would certainly have later flown with more powerful Lyul’ka engines. The propulsion system was ‘straight through’ from the plain nose inlet, which immediately divided to pass each side of the cockpit, to the tail. Amid­
ships, at Frames 15/15A and 20/20A, the main wing spars passed through at mid-level. The wing had CAHI (TsAGI)-9030 profile at the root, changing to symmetric SR-3-12s at the tip, the!4-chord sweep being 50°. Above each wing were two full-chord fences plus another from the leading edge to the aileron. Three tracks carried each of the Fowler-type flaps. High on the large vertical tail was mounted the fixed tailplane, again with 50° A-chord sweep and ground adjustable over the range ± 1.5°. The port aileron and starboard elevator had tabs, and the rudder had a section of ‘knife’ (thin strip behind the trailing edge). This aircraft pioneered Soviet use of hydrauli­cally boosted flight controls, on all axes. All units of the landing gear had levered suspen­sion, using high-pressure shock absorbers pi­oneered on the Su-15, and retracted into the fuselage. The nose unit had a 530 x 230mm tyre and retracted to the rear, while each main unit had an 800 x 225mm tyre and pneu­matic plate brake and retracted forwards about a skewed axis under the wing root, to be covered by a large door. The ventral bulge under the tail had a steel underside and made provision for housing a cruciform braking parachute. On each side of the rear fuselage was a door-type airbrake, opened to 60°, which like the flaps, landing gear and flight controls, was operated by a hydraulic system at what was then a new high pressure of 211kg/cm2 (207-MPa, 3,000lb/in2). The cock­pit was pressurized, maintaining 0.65kg/cm2 (9.2 lb/in2) up to 7km (22,966ft) and holding a constant dp of 0.3kg/cm2 (4.3 lb/in2) above that level. Like several previous Soviet air­craft, the pilot’s ejection-seat was mounted in a nose section designed to separate from the fuselage in an emergency. The planar joint, sealed by an inflatable ring, sloped forward to avoid the nose-gear, and it could be broken by firing a cordite charge at the bottom joint, allowing the nose to pivot and separate from the two upper connections. Separation was triggered automatically if vertical accelera­
tion reached ± 18 g, or under pilot commcind. The separated nose streamed a drogue which after a delay extracted the main ribbon parachute. The pilot could then eject, experi­encing a maximum of 5 g. The pilot could also eject normally, from the intact aircraft, but only after jettisoning the sideways-hinged canopy. A total of 1,219 litres (268 Imperial gallons) of fuel was housed in the fuselage, there being one metal and two bladder tanks behind the cockpit and three metal tanks (one a toroidal hollow ring) around the jet- pipe. Provision was made for a jettisonable 300 litre (66 Imperial gallon) tank to be scabbed under each wing, and for two N-37 guns, each with 40 rounds, to be mounted in the fuselage. The avionics were comprehen­sive, including vhf, radio compass, an IFF transponder and precision radio altimeter.

There is no reason to doubt that this aircraft would have been most valuable, and prevent­ing it from flying appears in retrospect to have been a serious error. The Soviet Union suf­fered from its thoughtless precipitate actions.

Purpose: To investigate the maximum load that could be carried by an aeroplane powered by a single M-l 1 engine.

Rivals included the Grokhovskii G-31 and KhAI-3, both described later.

Design Bureau: Oleg K Antonov, Kiev.

The idea was that of L E Malinovskii, Director of the Civil Aviation Scientific-Technical Insti­tute (hence the designation). AviAvnito and Osoaviakhim (the Society of Friends of Avia­tion and the Chemical Industry) provided funds in 1936, enabling the Kiev (Ukraine) constructor to create his first powered air­craft. The single example built was given the OKB designation of OKA-33, because it was their 33rd design. The flight-test programme was opened by test pilot N I Ferosyev on 20th April 1937. Results were satisfactory.

The LEM-2 was predictably almost a flying wing, based on the aerodynamics of Prof V N Belyayev, with a PZ-2 aerofoil modified from the common CAHI (TsAGI) R-ll. The M-l 1 five-cylinder radial, rated at l00hp, was mounted on the front in a long-chord cowl­
ing, driving a two-blade carved-wood pro­peller of the type mass-produced for the U-2 (later called Po-2). Construction was almost entirely wood, with ply skins of varying thick­ness. The wing comprised a centre section and two outer panels with long-span but nar­row ailerons. The inboard part of the wing had a chord of 6.7m (22ft) and so was deep enough (1.47m, 4ft 1 0in) to house the payload of 1,280kg (2,822 Ib). The payload compart­ment between the spars measured 2.4 x 1.5 x 1.2m (7’101 /2"x4’ll"x3’ll"). In the LEM-2 built the pilot was the only occupant, though it was the intention that a production aircraft should have provision for 11 passenger seats. Access to the main payload space was to be via large doors in the leading edge ahead of the front spar, but these were absent from the LEM-2 built. There was also a door in the upper surface behind the cockpit. The twin – finned tail was carried on two upswept booms attached at the extremities of the wing centre section. Landing gears comprised two main wheels (the intended spats were never fitted) attached to the centre-section end ribs,

and a skid under the trailing edge.

Development of aircraft in this class was soon discontinued, it being decided they were of limited practical use. In fact, espe­cially with slightly more power, they could have been used in the USSR in large numbers in huge regions devoid of roads and railways.

Purpose: To create a more manoeuvrable fighter.

Design Bureau: Brigade led by Mikhail Ivanovich Gudkov, Moscow.

Gudkov was one of the three partners who created the LaGG design bureau, later led by Lavochkin only. In early 1940 Gudkov be­came convinced that the Bell P-39 Airacobra, with the engine behind the cockpit, had a su­perior configuration. It gave the pilot a better view, and by placing the heavy engine in the centre of the aircraft greatly reduced the long­
itudinal moment of inertia, and thus should improve manoeuvrability. As well as working on supposed improved derivatives of the LaGG, Gudkov managed to obtain funding for a mid-engined fighter in early 1942, as well as a contract with the A A Mikulin bureau for the supply of an engine. The resulting Gu-1, also called the Gu-37, was completed in the early summer of 1943. After prolonged taxi trials test pilot A I Nikashin said ‘It seems glued to the ground’. On 12th June 1943 Nikashin at­tempted the first flight. The Gu-1 reached about 200m (650ft) but then appeared to sideslip into the ground, Nikashin being killed. Gudkov’s brigade was disbanded.

The configuration followed the Airacobra exactly, with the major difference that the Gu-1 was constructed largely of wood, with bakelite-ply skin. Metal parts included the fuselage back to the firewall between the cockpit and engine (aligned with the front spar), which was based on a steel-tube truss with skin of removable Dl panels, Dl wing spars and Dl control surfaces. The wing was of 1V-10 Type V-2 aerofoil profile, and was fit­ted with automatic leading-edge slats and hy­draulically driven split flaps. The engine was an AM-37 rated at l,380hp (the designer’s notes on the preliminary drawing show that he wanted an AM-41). Carburettor inlets were in the wing roots, and long inlets further out­board served the radiators inside the wing ahead of the inwards-retracting main landing gears. The drive was taken through a steel tube of 120mm (4%in) diameter to the reduc­tion gear in the nose. The long nose gear re­tracted back into a bay in the lower part of the nose. Armament comprised a massive Taubin 37mm cannon firing through the pro­peller hub, fed by an 81 – round magazine (sur­prisingly large for this calibre) and six ShKAS machine guns in the fuselage and wing roots.

Few documents on the Gu-1 have been found. One is led to conclude that either the wing or vertical tail was too small, or possibly both.