Category Soviet x-plenes

Purpose: Experimental rocket-engined interceptor-fighter.

Design Bureau: Designers Aleksandr Yakovlevich Bereznyak and Aleksei Mikhailovich Isayev, working at OKB of Bolkhovitinov, later managed by CAHI (TsAGI).

In 1939 Bereznyak was an observer at the sta­tic tests of the first reliable rocket engine de­veloped by Leonid Stepanovich Dushkin. In early 1940 he watched flight tests of the prim­itive RP-318 (see later under Korolyev). He discussed rocket aircraft with Isayev, who had been a Dushkin engineer involved with the RP-318. In late May 1941 they decided to propose a high-speed rocket-engined fighter. They put the suggestion to Prof Bolkhovitinov (see later entry). After discussion with all in­terested parties Bolkhovitinov sent a letter to GUAP (chief administration ofaviation indus­try) on 9th July 1941 putting forward a de­tailed proposal. Soon a reply came from the Kremlin. The principals were called to GUAP before Shakhurin and A S Yakovlev, and with­in a week there was a full go-ahead. The order was for five prototypes, with the time to first flight cut from the suggested three months to a mere 35 days.

A complete Bolkhovitinov team were con­fined to the OKB for 40 days, working three shifts round the clock. Tunnel testing was
done at CAHI, supervised by G S Byushgens. The first (unpowered) flight article was built without many drawings, dimensions being drawn directly on the materials and on tem­plates. B M Kudrin made the first flight on 10 th September 1941, the tug being a Pe-2. All necessary data were obtained in 15 flights. On 16th October the OKB and factory was evac­uated to a half-built shed outside Sverdlovsk. The first (experimental) D-1A engine was in­stalled in late January 1942, but exploded dur­ing testing on 20th February, injuring Kudrin (sent to hospital in Moscow) and a techni­cian. The replacement pilot was Capt G Ya Bakhshivandzhi. He was in the cockpit on the first tied-down firing on 27th April 1942. On 15th May 1942 he made the world’s first flight of a fully engineered rocket interceptor, still fitted with skis.

By March 1943 seven BI prototypes had been constructed, but the flying was entirely in towed or gliding flight because of serious problems caused by explosions and acid spillages. Powered flying did not resume until February 1943. By this time Kudrin had re­turned to flight status, and was assigned one of the Bis. On powered flight No 6 on 21st March 1943 a height of 3km (9,843ft) was reached in 30 seconds. On powered flight No7, with aircraft No 3, on 27th March, Bakhshivandzhi made a run at sustained full power; the aircraft suddenly pitched over and

dived into the ground. Tunnel testing later showed that at about 900km/h the BI would develop a nose-down pitching moment which could not be held by the pilot.

This terminated the delayed plan to build a production series of 50 slightly improved air­craft, but testing of the prototypes continued. Until the end of the War these tested various later Dushkin engines, some with large thrust chambers for take-off and combat and small chambers to prolong the very short cruise en­durance (which was the factor resulting in progressive waning of interest). Other testing attempted to perfect a sealed pressurized cockpit. To extend duration significantly BI No 6 was fitted with a Merkulov DM-4 ramjet on each wingtip. These were fired during test in the CAHI T-101 wind tunnel, but not in flight.

By 1944 the urgency had departed from the programme, and the remaining BI Nol (some were scrapped following acid corrosion) were used as basic research aircraft. BI No7 was modified with revised wing-root fairings and stronger engine cowl panels, but at high speed tailplane flutter was experienced. BI No 5s (on skis) and BI No 6 (on wheels) were modified and subjected to investigative glid­ing tests, initially towed by a B-25J.

In 1948 Bereznyak proposed a mixed – power interceptor with a three-chamber rocket engine of 10,000kg (22,046 Ib) sea – level thrust, for ‘dash’ performance, and a Mikulin AM-5 turbojet of 1,900kg (4,1891b) sea-level thrust. Estimated maximum speed was Mach 1.8, and range 750km (466 miles). This was not proceeded with.

The BI Nol had a small and outstandingly simple all-wood airframe. The straight-ta­pered wing, 6 per cent thick, had two box spars and multiple stringers supporting skin mainly of 2mm ply. Outboard were fabric – covered ailerons. Inboard were split flaps with light-alloy structure (the only major metal parts), with a landing angle of 50°. The fuselage was a plywood monocoque with fabric bonded over the outer surface. It was constructed integral with the upper and lower fins. The rudder and elevators were fabric-covered. On the tailplane were added small circular endplate fins, and the powered aircraft had the tailplane braced to both the upper and lower fins.

The engine bay was lined with refractory materials and stainless steel. The standard engine was the Dushkin D-1A-1100, the des­ignation reflecting the sea-level thrust (2,425 Ib), rising to about 1,300kg (2,866 Ib) at high altitude. The propellants, fed by com­pressed air, were RFNA (red fuming nitric acid) and kerosene. These were contained in cylindrical stainless-steel tanks in the centre fuselage. The pneumatic system not only fed the propellants but also charged the guns and operated the flaps and main landing gears. The latter retracted inwards into the wings and normally had wheels with 500 x 150 tyres. Under the ventral fin was a retracting tail-
wheel. In winter these units were replaced by skis, the main skis retracting to lie snugly under the wings.

The cockpit had a simple aft-sliding canopy, and a bulletproof windscreen. Cer­tain of the prototypes had armament, com­prising two ShVAK 20mm cannon, each with 45 rounds, fired electrically and installed in
the upper half of the nose under a cover se­cured by three latches on each side. Between the spars under the propellant cylinders was a bay which in some aircraft could house a small bomb load (see below). Structural fac­tor of safety was 9, rising to no less than 13.5 after using most of the propellants.

By any yardstick the BI No 1 was a remark­
able achievement, and all pilots who flew it thought it handled beautifully. It was killed by the time it took to overcome the problems, and – crucially – by the impracticably short flight endurance.

OKB drawing of BI No 6/PVRD.

Purpose: Reconnaissance from submarines. Design Bureau: Brigade of Ivan Vyacheslavovich Chetverikov in CAHI (TsAGI).

Later a famous designer of marine aircraft in his own right, Chetverikov was intrigued by the British submarine M-2, which carried a small aircraft for reconnaissance purposes. Though this proved a disaster in January 1932 when the M-2 was dived with the hangar door open, this did not invalidate the basic con­cept. Funds were obtained from both the MA (naval aviation) and the Glavsevmorput’ (ChiefAdministration ofPolar Aviation N orth – ern Sea Route). Accordingly Chetverikov de­signed a small monoplane in two forms: the OSGA-101 amphibian for Glavsevmorput’ for use from icebreakers and the SPL (Samolyot dlya Povodnikh Lodok, aeroplane for subma­rine boats), a slightly smaller non-amphibious
flying boat able to fold into a small hangar. OSGA flew in spring 1934. The SPL was com­pleted in December 1934, taken by rail to Sev­astopol and flown there by A V Krzhizhevskii in spring 1935. Testing was completed on 29th August 1935. Though the SPL was gener­ally satisfactory, the idea of submarines with aircraft hangars was never adopted by the MA.

Like its predecessor, the SPL was a neat monoplane, of mainly wooden construction but with the tail made of Dl alloy covered with fabric and carried on booms of welded steel tube through which the control wires passed. The cockpit seated a pilot and ob­server side-by-side, and there was provision for a third seat or cargo immediately to the rear. The engine was a modest M-l 1 rated at l00hp, in a Townend-ring cowl and driving a two-blade wooden propeller. The wings were fitted with plain flaps, and could be un­
locked and manually folded back with the upper surface facing outwards, the under­wing floats also being hinged. The engine na­celle, on a steel-tube pylon, could likewise be pivoted straight back through 90°, so that after four minutes the whole aircraft could be pushed inside a watertight drum 7.45m (24ft 5Kin) long and 2.5m (8ft 21/2in) diameter (in­ternal dimensions).

One report states that the MA claimed the SPL to have ‘inadequate seaworthiness’, while another states that it was difficult to take off from the open sea and was prone to stall because of poor longitudinal stability. The underlying factor was that the MA decid­ed not to build large submarines with SPL hangars.

Purpose: To test a liquid-propellant rocket engine in flight.

Design Bureau: RNII, rocket-engine scientific research institute; head ofwinged-aircraft department Sergei Pavlovich Korolyov.

Korolyov was a pioneer of light aircraft and, especially, high-performance gliders before, in early 1930s, concentrating on rocketry. In

1934 he schemed the RP-218, a high-altitude rocket aircraft with a two-seat pressure cabin and spatted main landing gear. The engines were eventually to have comprised three RD – 1, derived from the ORM-65 (see below), and in a later form the structure was refined and the landing gear made retractable. The RP – 218 was never completed, partly because Ko­rolyov was assigned to assist development of the BICh-11 (see under Cheranovskii). In

1935 he produced his SK-9 two-seat glider, and suggested that this could be a useful rocket test-bed. In 1936, in his absence on other projects, A Ya Shcherbakov and A V Pallo began converting this glider as the flight test-bed for the ORM-65. This was fired 20 times on the bench and nine times in Ko­rolyov’s RP-212 cruise missile before being in­stalled in the RP-318 and fired on the ground from 16th December 1937. The ORM-65 was
then replaced by the RDA-I-150 Nol, cleared to propel a manned aircraft. This engine was repeatedly tested on the ground, and then flew (without being fired) in four towed flights in October 1939. After further tests the RP-318 was towed off on 28th February 1940 by an R-5 flown by Fikson, with Shcherbakov and Pallo as passengers in the R-5. The SK-9 was released at 2,800m, and then glided down to 2,600m where pilot Vladimir Pavlovich Fedorov fired the rocket. The SK-9 accelerated from 80 to 140km/h on the level and then climbed to 2,900m, the engine stop­ping after 110 seconds. Fedorov finally landed on a designated spot. Shavrov: This flight was of great significance for Russia’s rocket en­gines’. Much later Korolyov became the ar­chitect of the vast Soviet space programme.

The RP-318-1 was based on the SK-9, a shapely sailplane of mainly wooden con­struction. The rear seat was replaced by a ver­tical Dl light-alloy tank for 10kg (22 Ib) of kerosene, and immediately behind this were two vertical stainless-steel tanks projecting up between the wing spars each holding 20kg (441b)of RFNA (red fuming nitric acid). The rocket engine and its pressurized gas feed and complex control system were installed in the rear fuselage, the thrust chamber being
beneath the slightly modified rudder. The RDA-I-150 was a refined version of the ORM – 65, designed jointly by V P Glushko and L S Dushkin. Design thrust was 70 to 140kg at sea level, the figure actually achieved being about 100kg (220.5 Ib). An additional ski was added under the fuselage.

This modest programme appears to have had a major influence on the development of Soviet rocket aircraft.

Already used for a MiG-15, this designation was repeated for MiG-17s used for further tests of the guidance system of the KS-1 Komet cruise missile. The original test-bed for this system had been the M1G-9L, and like that aircraft the SDK-5 had forward-facing an­tennas on the nose and wings and an aft-fac­ing antenna above the tail. Like the MiG-9L this aircraft later assisted development of the large supersonic Kh-20 (X-20) missile.

Photograph on the opposite page:

MiG-19 (SM-10).

Purpose: A series of air-launched experimental gliders intended to lead to air – to-surface missiles.

Design Bureau: Initially OKB-21, later OKB – 30, chief designer N G Mikhel’son, later VV Nikitin.

In 1933 S F Valk proposed the development of a pilotless air-launched glider with an au­topilot, infra-red homing guidance and large warhead for use as a weapon against ships, or other major heat-emitting targets. From 1935 this was developed in four versions which in 1937 were combined into the PSN (from the Russian abbreviation for glider for special purposes). At this stage chief designer was Mikhel’son (see previous entry on MP). The concept was gradually refined into the P SN -1, of which a succession of ten prototypes were launched from early 1937 from under the wings of a TB-3 heavy bomber. By 1939 the to­tally different PSN-2 was also on test. Also designated TOS, these were initially dropped from the TB-3 and later towed behind a TB-7 and possibly other aircraft. In each case the glider was to home on its target at high speed after release from high altitude.

The PSN-1 was a small flying boat, with sta­bilizing floats under the high-mounted wing.

It had a cockpit in the nose, where in the planned series version the warhead would be. In the DPT version the payload was a 533mm (1ft 9in) torpedo hung underneath. Once the basic air vehicle had been perfect­ed the main purpose of flight testing was to develop the Kvant (quantum) infra-red guid­ance. In contrast the PSN-2 was a twin-float seaplane with a slim fuselage, low wing and a large fin at the rear of each float. This again was flown by human pilots to develop Kvant guidance. After release from the parent air­craft the manned gliders made simulated at­
tacks on targets before turning away to alight on the sea. The planned pilotless missiles were intended to be expendable, and thus had no need for provisions for alighting.

Neither ofthe PSN versions made it to pro­duction, these projects being stopped on 19th July 1940. In retrospect they appear to have been potentially formidable.

Purpose: To create a more capable interceptor for the IA-PVO (manned air – defence aviation).

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

In December 1954 the MAP (Ministry of Avia­tion Industry) requested studies of a new fighter, called P (Perekhvatchik, interceptor). Studies embraced single – and two-seat air­craft armed with every combination of guns, rockets and guided missiles, and with nine types of afterburning turbojet. On 19th Janu­ary 1955 the Council of Ministers ordered from Sukhoi prototypes of the P-l powered by a single AL-9 and the P-2 powered by two VK-11 engines. Mockups were reviewed in late 1955, and construction of the P-l was au­thorised, the P-2 being abandoned in early 1956. OKB-51’s factory constructed the single

P-l from August 1956. At a late stage it was recognized that the chosen engine would not be ready in time, and the aircraft was re­designed for an engine of rather less thrust in order to get it airborne. It was taken to the OKB’s flight-test station on 10th June 1957, and was flown there by Nikolai Korovushkin on 12th July 1957. He was joined by Eduard Elyan, and Factory Testing was completed on 22nd September 1958. The intended engine never did become available, and Sukhoi failed to obtain an alternative (the R-15B-300 went instead to the T-37). The P-l was trans­ferred to the experimental category and final­ly abandoned.

Intended for a more powerful engine, the Lyul’ka AL-9 with an afterburning thrust of 10 tonnes (22,046Ib), the P-l was thus larger than all the other Sukhoi aircraft of its gener­ation. The wing was scaled up from the earli­
er PT-8, which had introduced the feature of a dogtooth discontinuity in the leading edge to create a powerful vortex at large angles of attack to keep flow attached over the upper surface. Unlike the PT-8 the leading-edge sweep was reduced at a point ahead of aileron mid-span from 60° to 55°. Otherwise the wing followed Sukhoi practice with rec­tangular slotted flaps, sharply tapered ailerons terminating inboard ofthe tips, land­ing gears retracting between Spars 1 and 2 and integral tanks ahead of Spar 1 and be­tween Spars 2 and 3. The large fuselage was exceptionally complex. In the nose was the single dish antenna of the Pantera (panther) search and fire-control radar, with the multi­function instrumentation boom projecting from the tip. With this aircraft Sukhoi gave up

trying to put the air inlet in the nose, and the radome formed the entire nose of the aircraft. Next came the bay housing the radar’s pres­surized container, around which was the main armament. After many changes this comprised five bays, each closed by a rapid – action door, each housing ten ARS-57 57mm spin-stabilized rockets. Upon automatic com­mand by the fire-control system, the rockets were either rippled in rapid sequence or fired in a single salvo, the doors quickly hingeing inwards from the front and the rocket gases being discharged through doors at the rear immediately ahead of Frame 8 (the front pressure bulkhead of the cockpit). Next came the nose landing gear, with a K-283 wheel with 570 x 140mm tyre, retracting to the rear, under the floor of the cockpit. The latter was of course pressurized, and accommodated the pilot and radar operator on tandem KS-1 ejection-seats under canopies hinged up­wards from the rear. Next came the lateral en­gine air inlets, which broke new ground in being circular (as they were cut back at a Mach angle of45° they were actually ellipses), standing slightly away from the fuselage to avoid swallowing boundary-layer air, and housing a half-cone centrebody axially trans­lated to front or rear according to flight Mach number. Downstream the air ducts, and thus the fuselage outer walls, curved sharply in­wards to form the common tube feeding the engine. This gave area-rule flow over the wings (an account stating that this aircraft was not area-ruled is mistaken). Additional non-integral tanks occupied the space be­tween the ducts, with piping in a dorsal spine linking the canopies to the fin (a new feature for Su aircraft). The engine was the well-tried AL-7F, rated at 6,850kg (15,101 Ib) dry and 8,950kg (19,731 Ib) with afterburner. At dou­ble Frames 36/36A the tail could be removed. The tail was similar to that of other Sukhoi prototypes of the era. So were the three hy­draulic systems, the two flight-control sys­tems serving a BU-49 power unit for the rudder, a BU-51 driving the one-piece tailplanes (this irreversible drive rendered anti-flutter masses unnecessary) and a BU-52 with rod linkages to the ailerons. The autopi­lot system used the AP-28 on the tailplanes and AP-39 laterally. The primary hydraulic system also drove the landing gear, the main units having KT-72 wheels with l,000x 280mm tyres, and the rocket doors, canopies, inlet centrebodies, flaps and (according to documents, though these do not appear on drawings and cannot be seen in pho­tographs) three airbrakes on the rear fuse­lage. Another puzzle is that one document mentions two NR-30 guns under the nose (one on each side of the bottom rocket com­partment, and these are shown in one draw­ing), while another states that ‘in the wing root was an armament section’, while two documents state that the main armament comprised two K-7 (replaced by K-8) guided missiles hung on underwing pylons. The lat­ter would have been outboard, ahead of the ailerons. Another document states that there was provision for an external tank under the fuselage, but this would have been difficult to accommodate because of the landing-gear doors and telemetry antenna. Other avionics included RSIU-4 V radio, SPU-2 intercom, Go – rizont (horizon) guidance and data link, SRZO-2 IFF, SOD-57M transponder, Sirena-2 (siren) passive warning receiver, ARK-51 ADF, MRP-56P marker receiver, GIK-1 and AGI-1 navaids, RVU radio altimeter and the RSBN-2 tactical landing guidance.

This complex aircraft never received the intended engine.

Purpose: To use Tu-16 aircraft for various experimental purposes, and to take the basic design further.

Design Bureau: OKB-156 ofA N Tupolev, Moscow.

This graceful twin-jet bomber sustained what was in financial terms the most important programme in the entire history of the Tupolev design bureau up to that time. Since then, because of inflation, the Tu-154 and Tu-22/Tu-22M have rivalled it, though they were produced in smaller numbers. The pro­totype Tu-16, the Type 88, was a marriage of upgraded B-29 technology in structures, sys­tems and to some degree in avionics, with to­tally new swept-wing aerodynamics and what were in the early 1950s super-power tur­bojet engines. The Tu-16 entered production in 1953 powered by Zubets (Mikulin KB) RD-3M engines of 8,200kg (18,078 Ib) thrust. The second series block had the RD-3M-200 of8,700kg (19,180 Ib) followed by the 9,500kg (20,944 Ib) RD-3M-500, which was then retro­fitted to most earlier aircraft.

From 1953 the basic aircraft was repeated­ly examined against alternatives based as far as possible on the same airframe but using different propulsion systems. Most of the studies had four engines. Tupolev had origi­nally schemed the 88 around two Lyul’ka AL-5 turbojets, but the design grew in weight to match the big AM-3 engine, and this was the key to its win over the smaller Ilyushin with the Lyul’ka engines. In parallel with the
production aircraft one project team led by Dmitri S Markov studied versions of the 88 with not two but four AL-5 engines, and then four of the more powerful (typically 14,330 Ib, 6,500kg) AL-7 engines. These Type 90s would have been excellent bombers, with in­creased power and much better engine-out performance, but the decision was taken not to disrupt production. On the other hand, vir­tually the same inboard wing and engine in­stallation was then used in the Tu-110 transport, two of which were built using the Tu-104 as a basis. Some of the four-engined bomber studies had engines in external na­celles hung on underwing pylons.

From 1954 Type 88 prototypes and a wide range of production Tu-16s were used over a period exceeding 40 years as experimental aircraft. Some carried out pioneer trials in aer­ial refuelling at jet speeds.

One large group of about 20 aircraft was kept busy in the development of avionics, in­cluding navigation, bombing and cartograph­ic guidance, parent control of drones and targets, and the direction of self-defence gun­nery systems.

Probably the most important single duty of Tu-16LL (flying laboratory) aircraft was to air – test new types of turboj et and turbofan engine. In each case the engine on test would be mounted in a nacelle either carried inside the weapon bay or, more often, recessed into it. Usually the test engine would be suspended on vertical hydraulic jacks or a large pivoted beam so that in flight it could be extended
down fully into the airstream, with its efflux well clear of the rear fuselage. In many cases the engine pod or the Tu-16 fuselage ahead of it would be fitted with a fairing or door which could be left behind or opened as the pod was extended for test. Among the engines air-tested under Tu-16LL aircraft were: the Ivchenko (later Progress) AI-25, Lyul’ka AL-7F – 1, AL-7F-2, AL-7F-4 and AL-31F, Solov’yov (Avi – advigatel) D-30, D-30K, D-30KP and D-30F6 (in MiG-31 installation), Lotarev (Ivchenko Progress) D-36, Kuznetsov NK-6 (with and without afterburner) and NK-8-2, Tumanskii (Soyuz)R-l 1 AF-300( Yak-28nacelle)andR-15- 300 (in the Ye-150 and the totally different MiG – 25installation), MetskhvarishviliR-2I-300and R-21F with Ye-8 inlet, Khachaturov R-27 ver­sions (including the vectored R-27V-300 in a complete Yak-36M prototype fuselage, Mikulin (Soyuz) RD-3M (many versions), Kolesov (RKBM) RD-36-41 and RD-36-51, and Dobrynin (RKBM) VD-7, VD-7M and VD-19 (in a pro­posed Tu-128 installation), etc.

One Tu-16 had its entire nose replaced by that intended for the Myasishchev M-55, in order to test the comprehensive suite of sen­sors. Another tested a scaled version of the bogie main landing gear for the Myasishchev M-4 and 3M strategic bombers, replacing the normal nose landing gear. A new twin-wheel truck was added at the tail. According to doc­uments a Tu-16 with outer wings removed tested the complete powerplant of the Yak-38 (presumably in free hovering flight) though photographs have not been discovered.

Purpose: To investigate the use of cryogenic fuels.

Design Bureau: ANTKA N Tupolev,

Moscow. Technical Director Valery Solozobov, cryogenic fuels ChiefDesigner Vladimir Andreyev.

For many years the USSR and its successor states have been replacing petroleum by nat­ural gas, which in 1999 provides over 53 per cent of the total of all Russia’s energy sup­plies. Since 1982 what is today ANTK Tupolev has been investigating the use of natural gas and also hydrogen as fuels for aircraft, because of their availability and clean burn­ing qualities. However, for use in vehicles both have to be liquefied by being cooled to exceedingly low temperatures. Liquid hydro­gen (LH2) boils at -255°C, an unimaginably low temperature at which (for example) all conventional lubricating oils are rock-solid. Moreover, this fuel is very expensive, and haz­ardous from the viewpoints of detonation and fire. On the other hand, liquefied natural gas (LNG) is widely available, at least threefold cheaper in Russia than aviation kerosenes, and also significantly improves flight perfor­mance. It is straightforward to store and han-

Below: Tu-155.

Photographs on the following page:

die, and less fire/explosion hazardous even than today’s kerosenes. After years of labora­tory work an existing civil transport was se­lected for use as an LNG flight test-bed. It has been flying since 1988. All work is now di­rected at the Tu-156, the first LNG aircraft de­signed to go into service.

T o flight-test an LNG sy stemANTKTupolev bailed back a Tu-154, No 85035, and replaced the No 3 (starboard) engine with an NK-88, fed with LNG by a completely separate fuel system. The NK-88 is a derivative of the Kuznetsov NK-8-2 turbofan (still fitted in the Nos 1 and 2 positions), with thrust unchanged at 20,945 Ib (9,500kg). The successor to Kuznetsov’s bureau is Samara/Trud. The complex feed system is shown in a drawing. The main tank, of 10ft 2in (3.1m) diameter and 17ft 81/2in (5.4m) long, is of AMG6 alu­minium alloy, with a 50mm (2in) lagging of foamed polyurethane. The NK-88 engine has a dedicated two-stage centrifugal pump dri­ven by a bleed-air turbine. LNG comes in at -152°C and is passed through a heat ex­
changer to convert it to gas. The engine com­bustion chamber is able to accept either this supply of NG or, on command, to switch to the kerosene supply normally used for the other engines. Work is still underway on a low-emissions chamber which will be used on the improved NK-89 engine to be fitted to the Tu-156. The definitive Tu-156 is expected to have the fuel in giant saddle tanks along the top of the fuselage. Instead, to reduce time and cost, at least the first Tu-156 has a main tank (capacity 28,6601b, 13 tonnes) behind the passenger cabin and, to preserve centre of gravity position, an auxiliary tank (8,377 Ib, 3,800kg) in the forward underfloor baggage hold. This reduces payload from 18 tonnes to 14 (30,864 Ib). Range will be 1,616 miles (2,600km) on LNG only, or 2,051 miles (3,300km) on combined LNG and kerosene.

Eventually the Earth’s store of petroleum will run dry. It is pointless to say ‘More keeps being discovered’. The world’s aircraft will then have no alternative but to switch to an­other fuel, and LNG is the obvious choice.

Purpose: To copy the Lockheed U-2B. Design Bureau: OKB No 49, Taganrog, General Constructor G M Beriev.

On 1 st May 1960 the world was astonished to learn that the missile defences of Sverdlovsk had shot down a Lockheed U-2 of the US Central Intelligence Agency. Parts of the air­craft were put on display in Moscow’s Gorkiy Park. What the world was not told was that for months afterwards a vast area was combed by large squads looking for every fragment of the downed aircraft (which had broken up at high altitude). All the pieces were brought to GK Nil WS, where they were carefully studied. On 28th June 1960 SovMin Directive 702-288 instructed OKB No 16 in Kazan, led by P F Zubets, to copy the J57-P-13 engine. This was a blow to Zubets, whose RD-500 was in the same thrust class, and even more to the several engine designers (Do­brynin, Lyul’ka, Kuznetsov and Tumanskii) who had engines on test which were more
powerful and of much later design than the massive Pratt & Whitney. On 23rd August 1960 Directive 918-383 ordered OKB No 49, assisted by neighbouring No 86, to study the U-2 and produce five copies, designated S-13. These were primarily to support ‘a multi­discipline study of the structural, technical and maintenance aspects of the U-2, and master its technology for use in indigenous aircraft’. It was also expected that the S-13 would be used to collect upper-atmosphere samples, destroy hostile balloons and (using the 73-13, or AFA-60, camera) undertake re­connaissance missions. Despite inexorable increases in weight over the US original, work attempted to meet the first-flight date of first quarter 1962. Much of the supporting equip­ment had already been developed for the Yak-25RV and TsybinRSR (which see). On 1st April 1961 a detailed metal fuselage mock-up was completed, with ‘models of its systems’. A Tu-16 was readied for testing the engine (now designated RD-16-75), landing gears
and other items, while CAHI tunnels con­firmed that the U-2 had the exceptional L/D ratio of25. Out of the blue, on 12th May 1962 Directive 440-191 ordered the whole S-13 project to be terminated.

Purpose: To test previously invented ‘parabola wing’ in a powered aircraft Design Bureau: Not an OKB but a private individual, Boris Ivanovich Cheranovskii (1896-1960). Throughout his life he scratched around for funds to build and test his succession of 30 types of gliders and powered aircraft, all of ‘tailless’ configuration.

In 1924 Cheranovskii tested his BICh-1 ‘Para­bola’ glider and the refined BICh-2, which demonstrated ‘normal longitudinal stability and controllability and is considered to have
been the world’s first successful flying wing’. In 1926 he followed with the BICh-3, which was almost the BICh-2 fitted with an engine. Cheranovskii’s gliders had been flown at the All-Union meetings at Koktebel, Crimea, but most of the flying of his first aeroplane was done by B N Kudrin (later famous) in Moscow.

The BICh-3 was a basically simple aircraft, constructed of wood with thin ply skin over the leading edge, inboard upper surface and landing-gear trousers, and fabric elsewhere. The BICh-2 had flown without a rudder (it was better with one) since turning was
achieved by the ailerons. With the BICh-3 the addition of an engine required a vestigial fuselage with a fin and rudder. The main con­trols remained the trailing-edge elevators and ailerons, operated by rods and bellcranks and hung on inset balanced hinges. The engine was a Blackburne Tomtit, an inverted V-twin of 698 cc rated at 18hp. Skids were provided under the tail and outer wings.

Kudrin described the BICh-3 as ‘not very stable, but controllable’. It was sufficiently successful to lead to the many successors.

Purpose: To modify established jet aircraft in order to test ejection-seats.

Design Bureau: Initially the seats were designed by special teams formed in the jet – aircraft OKBs. However, in 1952 a special organization was created to specialize in life-support and safety-equipment systems, and in 1994 this was transformed into NPP Zvezda (Star) joint-stock company. From the 1960s this organization captured the market until it was providing ejection-seats for virtually all Soviet combat aircraft.

Soviet ejection-seats, called Katapul’tnoye Kreslo, were initially diverse, and drew heav­ily on designs by US, Swedish and, especially, the British Martin-Baker companies. After 1945 a few flight tests took place with German seats, developed in 1944 for such aircraft as the He 219 and Do 335. The detailed history has not been written, but some of the earliest
flight tests were carried out from about mid – 1947. Probably the first Soviet ejection-seat was designed in the MiG OKB from January

1947. On 11th March 1947 this OKB received an order to test this seat in the FT-2, the sec­ond prototype of the M1G-9UTI trainer. After ten test ejections in a ground rig the experi­mental seat, weighing 128.5kg (283 Ib), was initially installed in the considerably modified rear cockpit of FT-1 (the first two-seater which was still with the MiG OKB). Flight test­ing took place throughout the first half of

1948, but only up to 700km/h (435mph). The very similar FT-2 was then fitted with two ejection-seats, the front one at a rail angle of 22.5° and the rear at 18.5°. The modified air­craft was delivered to NIl-WS, the air force flight test institute, on 29th September 1948. After two tests with dummies live testing con­tinued between 7th October and 13th No­vember 1948. An automatic sequence firing
the canopies and seats was then perfected (though ofcourse the FT-2 was never left with both cockpits empty). From the results of these tests the OKB gradually developed the first production seat, called the SK. This was then developed through 14 production series.

Probably the next Soviet aircraft to be used for ejection-seat testing was the Ilyushin IL-28 tactical twin-jet bomber. First flown on 8th July 1948, using the imported Rolls-Royce Nene and later the Nene-derived RD-45 and VK-1 A, this excellent aircraftwas used for sur­prising tests using seats fired from the ex­treme tail. Unlike the very similar British Canberra, which was undefended, for this aircraft the Ilyushin OKB developed a power­ful tail turret with two NR-2 3 guns, manned by the radio operator who had an escape chute. In several aircraft the turret was replaced by a special test installation for an ejection-seat. Both upward – and downward-firing seats

were tested, and cine films showed that in some cases firing the seat imparted to the air­craft a pronounced kick in the pitching plane, either nose-up or nose-down. Some of the IL-28 seat tests were at airspeeds exceeding 800km/h (497mph).

Even higher speeds were reached during seat testing with ST-10 aircraft, which were specially modifiedtwo-seat UTI MiG-15s. This was the principal type used from 1951 on­wards in development of the SK and SK-1 seats which were used in thousands of early MiG jets, and later for the much better KM-1 family used in later MiG fighters, cine films and photographs have shown seats being fired from ST-lOs with callsigns 15, 23, 101U, 102U and 401U. These aircraft were painted with bold horizontal black lines in known po­sitions to assist determination of the seat tra­jectory. What is surprising is that about half the photographs of tests appear to have in­volved firing the test seat from the front cock­pit. Using dummies and human occupants many hundreds of combinations of canopy, seat, ejection gun, stabilizing drogue and parachute system were investigated. Early SK seats were notoriously unreliable, and when they did fire on command the pilot often suf­fered spinal damage. Gradually, and espe­cially after the ST-10 testing began, the SK seats improved. A faceblind was provided to
protect the occupant’s face, additional firing triggers were incorporated in both armrests, improved ejection guns were developed im­parting a precisely repeatable phased accel­eration using different cartridges for summer and winter, and the original restrictive limits of airspeed and altitude were progressively increased. A photograph shows 101U, one of the aircraft with a completely open front cockpit. The final ST-10,401U, was fitted with a new type of front-cockpit canopy which was hinged at the rear to the top of the seat so that on ejection the canopy served as a wind­break to protect the occupant. This became a feature of early MiG-21 fighters.

Photographs have been found of at least two Yak-25L (Laboratoriya) seat-test aircraft. The production night fighter seated the pilot and radar operator in tandem under a large one-piece canopy which opened by sliding on rails 2.2m (7ft Sin) to the rear. Both the seat test-beds had a pressure bulkhead separating the front cockpit from the rear cockpit, from which the seat under test was fired. Aircraft callsign 18 retained the original type of canopy but with the portion over the rear cockpit opaque (on being jettisoned this usu­ally passed perilously close to the tail). Air­craft callsign 01 had a completely modified arrangement, the pilot having a short upward – hinged canopy and the test cockpit having a
prominent light-alloy superstructurewhich in most tests was open at the top. This aircraft was later used to test the Yakovlev OKB’s KYa-1 rocket-boosted seat, the first to have ‘zero/zero’ capability (able to be fired with the aircraft at rest on the ground).

The only Sukhoi aircraft known to have been an ejection-seat test-bed was an Su-9U with callsign Red 10. Liberally covered on the starboard side with black lines for use as tra­jectory references, this Mach-2 aircraft always fired the test seat from the rear cockpit. This was open-topped and sealed from the pres­surized front cockpit. The only photographs released on this aircraft must have been taken since the 1970s, as they show modern Zvezda zero/zero rocket assisted seats, at least one being of the K-36 family. One pho­tograph shows a test at ground level.

While the Su-(U was used for tests at high subsonic Mach numbers, at least on M1G-25U has been used to confirm behaviour in ejec­tions at supersonic speeds. Details of the seats and Mach numbers have yet to be dis­closed, but Zvezda believe this aircraft has been used to check successful ejections at mach numbers significantly higher than any­where else in the world.

Purpose: To make an invisible aeroplane. Design Bureau: Zhukovskii WA, Soviet air force academy; designer Professor Sergei Kozlov.

Professor Kozlov was eager to see to what de­gree it would be possible to construct a ‘transparent’ aeroplane, difficult to see (for example, by enemies on the ground). In 1933 a preliminary experiment was made with a U – 2 biplane whose rear fuselage and tail were stripped of fabric and re-covered with a trans­parent foil called Cellon (unrelated to the British company of that name). In 1935 the WA was assigned Yakovlev’s second AIR-4, which already had experimental status. The airframe was completely stripped of all cov­ering and internal equipment, and reassem­bled as described below. Though it was called the Nevidimyi Samolyot, invisible aero­
plane, it received the unexplained official designation of PS. It first flew on 25th July 1935.

The AIR-4, one of A S Yakovlev’s first de­signs, was a neat parasol monoplane, first flown in 1930. Powered by a 60hp Walter NZ – 60 five-cylinder radial, it had two seats in tan­dem. The structure was almost entirely wood, with skin of ply and fabric. The pairs of wing bracing struts were mild-steel sheet wrapped round to an aerofoil section 64 x 32mm (21/2 x l!4in). Of course, Kozlov could do nothing to hide these struts, nor the rub­ber-sprung divided main landing gears, or the engine, fuel tank and other parts. Virtually the whole airframe was covered in a French transparent plastic called Rodoid. This was cut from sheet, each panel being drilled and secured by aluminium rivets inserted through eyelets. As far as possible the opaque parts

were painted silver-white.

The PS was officially judged to have achieved results which had ‘a measure of im­portance’. Apart from the invisibility effect, the transparent skin was also held to improve the field of view of the occupants, and Kozlov did preliminary studies for a transparent re­connaissance aircraft. On a low-level flypast the PS was said to be not easily seen except by chance, though of course observers could narrow the field of search from judging the source of the aircraft’s sound. After a few weeks, however, the foil skin was of little use, partly because of progressive darkening by solar radiation and partly because of the ef­fect of dust and oil droplets from the engine.

Left: PS accompanied by a U-2.