In 1955, the Yakolev OKB flew the prototype of a light tactical bomber, the Yak-26, which, evolved from the Yak-25, embodied aerodynamic refinement and was powered by two Tumansky RD-9AK turbojets each rated at 3250kg with afterburning. During test, the Yak-26 achieved 1235km/h at 3000m, or Mach = 1.05, but suffered from serious instability at high attack angles, development consequently being discontinued in favour of a tandem two-seat all-weather fighter, the Yak-27
In the summer of 1951, the NKAP issued a requirement for an all-weather interceptor fighter possessing sufficient internal fuel capacity to mount standing patrols of up to 2.5 hours duration and capable of accommodating a large, new radar. This supplanted an earlier requirement to which the Mikoyan-Gurevich I-320 and Lavochkin La-200 had been evolved. The new radar, known as the Sokol (Falcon), had a 80cm diameter dish, three different scan modes and an installed mass weight of almost 500kg. To meet this new requirement, the Lavochkin and Yakolev OKBs respectively developed the La-200B and Yak-120. The latter, an all-metal stressed-skin tandem two-seater, was powered by a pair of small-diameter Mikulin AM-5A turbojets each rated at 2200kg / 4850-lb and hung beneath a wing swept back 45 degrees at quarter chord and carrying some 3 degrees of anhedral, and mounted in full-mid position. The undercarriage was of zero-track type, with wingtip-housed outrigger stabilisers, and armament comprised two 37mm N-37L cannon with their barrels accommodated in external fairings beneath the fuselage.
From 1957 the Mikulin AM 5 turbojets were replaced in the definitive Yak 25F by Tumansky RD 9s of 2600 kg (5730 lb) thrust, increasing the maximum speed.
The first of three Yak-120 prototypes was flown on 19 June 1952, State acceptance testing paralleling construction of a pre-series of 20 aircraft for avionics development and, commencing late 1953, service evaluation. With ballast equivalent in weight to the Sokol radar – which did not attain service status until late 1955 – the Yak-120 had a loaded weight of 9220kg, series production commencing late 1953 as the Yak-25 with RD-9 turbojets each rated at 2630kg. Confusing repetition of the “Yak-25” designation resulted from its initial use as an OKB appellation and subsequent use by the NKAP as an official and sequential designation, the previous Yakolev service fighter having been the Yak-23. The Yak-25 was assigned primarily to defence sectors in the Far North of the USSR, production being completed in 1958 after the delivery of 480 aircraft and service phase-out taking place in the mid ‘sixties.
The production programme took the type right through toward the end of the 1960s in role-differentiated models designated Yak-25, Yak-26 and Yak-27 with swept wings and on the Yak-25RD high-altitude reconnaisance version with straight wings.
The intercepter was codenamed Flashlight-A by NATO’s Air Standards Coordinating Committee, Flashlight B being a reconnaissance variant developed concurrently for service with the Soviet air force’s frontal aviation or tactical air arm.
A tactical reconnaissance derivative with the navigator accommodated in a glazed nose was built in 1953 as the Yak-125, but was not produced in series owing to prior adoption of the IL-28R. Other derivatives of the basic design were the Yak-25L ejection-seat test bed with individual cockpits, and the Yak-25RV long-range high-altitude strategic reconnaissance aircraft.
The Yak 25R carried the second crew member in a pointed glazed nose instead of behind the pilot, and armament was reduced from the intercepter’s pair of 37 mm (1.46 in) NR 37 cannon to a single 23 mm (0.90 in) weapon in the right-hand side of the forward fuselage.
Engines: 2 x Klimov VK-5, 8820 lb thrust Max take-off weight: 10900 kg / 24031 lb Wingspan: 11.00 m / 36 ft 1 in Length: 15.67 m / 51 ft 5 in Height: 4.32 m / 14 ft 2 in Wing area: 28.94 sq.m / 311.51 sq ft Max speed: 1090 km/h / 677 mph Cruise speed: 820 km/h / 510 mph Ceiling: 13900 m / 45600 ft Range: 2730 km / 1696 miles Armament: 2 x 37m cannon
Developed in parallel with the Yak-23, the similarly-powered Yak-25 was conceptually more advanced and derived from the Yak-19. By comparison with the earlier fighter, the Yak-25 employed the higher-speed TsAGI S-9S-9 laminar section at the wing root translating to a KV-4-9 section at the tip with a constant thickness of 9% throughout. Despite the greater diameter of the 1625kg RD-500 (Rolls-Royce Derwent) – similar to that installed in the Yak-23 prototypes – than the RD-10F of the Yak-19, the diameter of the fuselage of the Yak-25 was unchanged. Sweptback horizontal tail surfaces were adopted, provision was made for two 200-litre drop tanks under the wing tips and armament comprised three 23mm NR-23 cannon. The first of two prototypes was flown on 31 October 1947, but, although the subsequent flight test programme was allegedly successful, no production contract was issued for the Yak-25. One of the prototypes was utilised during 1948 for (fixed) tandem-wheel undercarriage trials as part of the Yak-50 development programme.
Max take-off weight: 3235 kg / 7132 lb Empty weight: 2285 kg / 5038 lb Wingspan: 8.88 m / 29 ft 2 in Length: 8.65 m / 28 ft 5 in Wing area: 14.00 sq.m / 150.69 sq ft Max. speed: 972 km/h / 604 mph Range: 1445 km / 898 miles
Soviet rotorcraft development was suspended during World War 2, and it was not until late summer 1952 that the USSR made its first major effort to close the design gap between itself and the USA in regard to large transport helicopters. In response to order of Stalin at a Kremlin meeting autumn 1951, two basic projects were selected, the first, for a 12-passenger machine of single main rotor configuration, being assigned to the Mil design bureau. The second, entrusted to the bureau headed by Aleksandir S. Yakolev, was for a twin-engined, tandem-rotor machine capable of seating 24 passengers. Prototype flights of both types were required to take place within one year.
Mil had already prepared suitable design, and Yak gained permission to use essentially same main rotor and drive from similar engine, merely doubling up to use two engine rotor systems at ends of boxcar fuselage. Yak assembled a large team including Erlikh, veteran helicopter man N.Skrzhinskii, P.D.Samsonov (famed flying-boat designer who had long managed Yak prototype dept), L.Shekhter, L.S.Vil’dgrub and many other well-known engineers. The plan was to build four four Yak-24, already called LV (Letayushchii Vagon, flying wagon), two for static and resonance test and two for flight. Yakolev was promised “unlimited support” for the rush programme.
A S Yakolev has described how, in autumn 1951, he and other designers were called to the Kremlin and told by Stalin to create two helicopters, one to carry a useful load of 1,200kg or twelve armed infantry and the other just twice as much, prototypes to be ready in one year. It was to be a ‘crash programme’, with ‘unlimited support’ from the national research institutes. Nobody was eager, but eventually Mikhail L Mil agreed to tackle the smaller machine and Yakolev the larger, Yakolev having the idea of simply using tandem rotors based on those of the Mil’ design.
Designing the Yak-24 started in December 1951. Though the first prototype was built extremely quickly, this programme was to prove more protracted than any previous endeavour by the OKB. Including later versions the chief engineers comprised I A Erlikh (the original leader) and P P Brylin, Yu I Orlov, V P Lashkov, G I Rumyantsev and G I Ogarkov.
Mil, with CIAM, CAHI and other organizations, including Shvetsov’s engine KB, developed the rotor and its drive system. The engine was the ASh-82V, a special helicopter version of the fourteen-cylinder radial used in some Yak fighter prototypes. Rated at l,430hp, and with 1,700hp available for takeoff, it was developed with a cooling fan and centrifugal clutch and cleared to operate in any attitude. It was decided to install the front engine between the cockpit and cabin at an angle of 60deg to drive the gearbox under the front rotor. The rear engine was installed in the normal attitude in the base of an enormous rear fin which formed the pylon for the rear rotor, driving through a 90deg bevel gearbox.
The rotors had fully articulated hubs made of D16 and steel, with drag and flapping hinges and friction dampers. In fact, the rotor was not identical to that of the Mi-4, and indeed later Mil enlarged his rotor by using Yakolev’s longer blades. The four blades were tapered, with NACA-230 profile, based on a 30KhGSA spar with ply ribs and skin covered in varnished fabric, with tracking adjusted by a tab on the trailing edge near the tip. The fabric was replaced by a steel rotor with a metal skin on the production models. The rotors turned at 178 rpm in opposite directions, the rear rotor being a mirror image of the front rotor which it over-sailed. The gearboxes were linked by a torque shaft so that flight could just be maintained on one engine. Each engine was geared to drive one or both rotors. Unfortunately this arrangement, although intended as a precaution against failure of either engine, created the problem of ‘sympathetic’ vibration. From the outset, vibration hampered the Yak-24’s development.
The boxcar fuselage was based on a truss of welded KhGS A tube, originally fabric-covered, then skinned with unstressed Dl panels covering the engine bays, rotor pylons and fin, and by fabric elsewhere. Each engine was housed in a fire-resistant bay with large apartures for cooling air, those for the rear engine being forward-facing open inlets beside the fin leading edge. Each engine had its own fuel tank. At the front was the fully glazed cockpit for two pilots and a radio operator/engineer, with a sliding door on each side and a rear door to the engine compartment, through which a narrow passage led to the main cabin. Aluminium plank cargo floor with full-section access via rear ramp/door; passenger door forward on left side.
Rear rotor mounted on top of vertical fin (TE curved to right to give side-thrust to left in flight) with drive from engine installed in normal horizontal attitude at base of fin, with open cooling-air inlets each side of fin and clearance under engine for vehicles and other cargo on ramp. High-speed connecting shaft to front rotor, mirror-image with rotation anti-clockwise seen from above, driven by engine at 60° angle between cockpit and cabin. Nose cockpit for two pilots, radio-operator and engineer, entirely glazed with aft-sliding door each side and sliding door(s) at rear giving restricted access past engine to main compartment. This measured 10m long, the cross section being 2m square with intended accommodation for up to 40 troops on canvas wall seats or light vehicles or 4t cargo, with crane operation using central hook on underside of fuselage. There were six windows on each side, one being in a door, and at the back was a full-width ramp door through which shallow loads such as a GAZ-69 ‘Jeep’ could be moved under the rear engine on to the floor of aluminium planks. Four similar levered-suspension wheel landing gears, each normally castoring +/-30 deg, on rigid welded steel-tube outriggers. The track was 5m.
Two flying prototypes completed, and two others were built for static and dynamic testing. While numerous establishments tested complete engine/rotor rigs, blade fatigue and truss structure of fuselage, first flight article readied spring 1952 and began 300 hr endurance test with wheels tied down. Vibration in evidence from start, and usually severe. With greater experience OKB might have recognised a fundamental N1 main-rotor mode and altered critical dimension. As it was, at 178th hour, rear engine tore free from fatigued mounts, machine being destroyed by fire. Second flying article, ie, 4th airframe, finally began tethered flight piloted by Sergei Brovtsev and Yegor Milyutchyev 3 July 1952. Hops at partial power were followed by full-power flights, when vibration reared its head dangerously. Five months by every available expert found no cure; then Yakolev personally ordered 0.5m cut off each main-rotor blade, reducing diameter from 21m to 20m. This effected immediate great improvement. No.4 aircraft delivered for NII test Oct 1953, but destroyed when tethers snapped during ground running. OKB delivered improved aircraft with numerous mods including modified tail with no fins but braced tailplanes with dihedral 45°. This finally passed NII April 1955 and production began at GAZ in Leningrad. With official tests completed on later prototypes, production began in April 1955, and only four months later evaluation aircraft were demonstrated at Tushino airport during the Soviet Aviation Day display. The first four pre-series Yak-24 (visibly not all identical) flew at Tushino, Aug 1955.
Final development work on the aircraft was extremely long and complex and full-scale production for the armed forces began in 1955, about 30 months behind schedule.
Series version had strengthened floor with tracks for vehicles, tie-down rings, attachments for pillars carrying 18 stretchers, full radio and night equipment and facilities for field servicing. Normal max load 20 armed troops or 3t.
The early Yak-24’s featured a Vee tailplane, but later production examples had rectangular endplate fins on a horizontal tailplane, and both have been seen with and without a narrow auxiliary rudder.
Production was ordered at a Leningrad factory, where thirty-five were built for the VVS in 1956-58. These were painted in dark green camouflage, and except for the first few had larger tailplanes with dihedral reduced to 20deg carrying large endplate fins set at an angle of 3deg 30′ to give the required thrust to the left in cruising flight, the tail end no longer being curved to the right. They had full equipment for loading and securing vehicles and other cargo up to a maximum of 3,000kg. Canvas wall seats were provided for twenty troops, with racks for weapons and equipment, with pillar sockets for eighteen stretchers accompanied by an attendant. A three-tonne load could also be slung from a central hook, but on 17 December 1955 Milyutichev carried an overload of four tonnes to 2,092m. On the same day G A Tinyakov set a second world record in the same prototype by taking 2,000kg to 5,032m.
At an air display in Moscow in July 1956 the Yak 24 made its first appearance.
Yak-24U (Uluchshennyi, improved) flew Dec 1957 with numerous mods resulting from prolonged research. Rotor blade length unchanged but diameter restored by adding long tubular tie at root. Side-thrust at tail reduced by canting axes of rotors 2°30′ (front to right,, rear to left), so curved rear of fin removed. Fuselage frame strengthened, metal skinned throughout and cabin increased in width 0.4m. Flight-control system fitted with two-axis autostab and autopilot of limited authority, developed within OKB. External slung load attached to winch in roof of cabin with large door in floor. Rear landing gear oleos changed in rate to eliminate last vestiges of ground resonance, and other minor changes including revised fuel system.
In production GAZ-33 early 1959, though halted at No 40. This variant could at last lift 40 troops or 3.5t and at least some production machines had tailplane dihedral 0°.
In January 1958 a complete three-axis autostabilization system was cleared for service and retrofitted to each helicopter. This dramatically improved stability and control, making hands off hovering possible. The USAF called this helicopter ‘Type 38’, later replaced by the ASCC name ‘Horse’.
Initial Yak-24 production was undertaken on behalf of the Aviatsya Vozdushno-Desantnich Voisk (Aviation of the Airborne Troops), in which configuration the aircraft could accommodate up to 40 fully-equipped troops according to range. Other typical loads of the “Letayuchiy Vagon” (Flying Wagon), as it was quickly dubbed, include 18 casualty litters, 2 anti-tank guns, 2 GAZ-69 command vehicles or 3 M-20 staff cars. In 1958 the Yak-24U became the standard military model, with all-metal rotor blades and fuselage skin, the revised tail configuration already mentioned, and the rotors restored to the original 21.00m diameter.
Yak-24U This Uluchskennyi (improved) helicopter was completed in December 1957, and tested from January 1958. The rotor blade spars were connected to the hub by oval-section steel tie rods at the root, restoring rotor diameter to the original design value. The axes of the rotors were canted 2deg 30′, the front hub tilted to the right and the rear to the left, so that the entire tail could be redesigned for minimum drag without the need to generate side thrust. Avionics included a two-axis autostabilization system and limited-authority autopilot developed mainly within the OKB. The fuselage truss was strengthened and increased in width by 0.4m and made slightly higher, and metal-skinned throughout. The external slung load rating was increased to 3,500kg, and the cable passed through a large floor hatch to a winch in the roof of the cabin. The rear landing oleos were modified to eliminate any tendency to resonance (now a better understood phenomenon), and later the fuel system was improved and the capacity significantly increased. This prototype could carry thirty-seven armed troops, but its main use was as a crane, putting roof trusses on the Pushkin (Ekaterinskii) palace and carrying gas pipes from Serpukhov to Leningrad over impassable marsh.
One example built by 1960 of Yak-24A (designation from Aeroliniya, airline) similar to late Yak-24U with horizontal tailplane and latest avionics but with comfortable civil interior for 30 passenger seated 2+1. Continious glazing down sides of fuselage, compartment for 300kg baggage and the rear freight door eliminated. Appeared in Aeroflot markings though never in service. The passenger door on the left was fitted with fold-down steps, and the cabin was fitted with larger windows.
Aeroflot (the Russian state airline) evaluated the Yak-24A commercial version, but turned it down. The Yak-24A can also be operated as a freighter or flying crane, being able to lift an external sling load of 5000kg. It also rejected the 1960 Yak-24K deluxe short fuselage version for 8-9 passengers. The fuselage was shortened, fitted with even bigger windows, improved soundproofing and heating and an electrically-operated airstairs, and luxuriously furnished for nine passengers. The Yak-24P for 39 passengers, with two 1500shp Isotov turbines mounted above the cabin was never built.
The Yak-24UB, flown in December 1957, included many design improvements and was placed in production from 1959, about 50 being delivered; this version could carry 40 fully equipped troops or up to 3500kg of cargo.
This type resulted from an October 1946 requirement, and as one of the bureau’s first all-metal stressed-skin designs was based on a “stepped” fuselage with the RD-500 engine (in essence a British unit, the Rolls-Royce Derwent V centrifugal-flow turbojet, built in the USSR) located in the forward fuselage and ex¬hausting below the fuselage in line with the cockpit and trailing edges of the unswept wing. This kept the engine installation as short as possible, and so avoided the efficiency losses associated with a long jetpipe. The Yak-23 possessed wing and horizontal tail surfaces similar to those of the Yak-19, and was intended to fulfil a requirement for a lightweight day interceptor capable of operating from existing fields. The first of three prototypes of the Yak-23, which were of all-metal stressed-skin construction and powered by imported Rolls-Royce Derwent turbojets, was flown on 17 June 1947. Seen as something of a back-up for the very much more advanced Nene-engined fighters with wing sweep-back then under development, the Yak-23 proved itself an outstandingly agile warplane. NATO code name Flora. Manufacturer’s trials were completed on 12 September 1947. State Acceptance testing had been successfully completed before the year’s end and series production began in the late spring of 1948. The series Yak-23 was powered by a Soviet copy of the Derwent known as the RD-500 – a designation derived from GAZ-500, the factory in which the engine was produced – and rated at 1590kg. Its armament consisted of two 23mm NS-23 (later NR-23) cannon. Deliveries to the V-VS began early in 1949, by which time the first production examples of the MiG-15 had already flown. In consequence, only two V-VS regiments reportedly re-equipped (from the Yak-17) with the Yak-23, which was quickly released for export. Twelve were delivered to Czechoslovakia during 1950 (and there assigned the designation S101) and the supply of some 95 to Poland began late that year, while, in 1951, 12 each were delivered to Romania and Bulgaria. Both Czechoslovakia and Poland were to have licence-built the Yak-23 but, in the event, manufactured the MiG-15, and Soviet production of the Yakolev type terminated in 1950 with 310 built.
One example was converted by the OKB as a tandem two-seat conversion trainer (Yak-23UTI), this first being flown in the spring of 1949. One Yak-23 was rebuilt as a tandem two-seater in Romania, but the type had given place to the MiG-15 in all Warsaw Pact air forces by the mid ’50s.
Bulgarian Yak-23
Principal versions – Yak-23 (basic fighter model) and Yak-23UTI (two seat conversion trainer whose production is unconfirmed). Principal users – Czechoslovakia, Poland, Romania, USSR, and possibly other Warsaw Pact countries.
Engine: one 3,505-lb (1,590-kg) thrust RD-500 turbojet Wing span 28 ft 7.75 in (8.37 m) Length 26 ft 7.75 in (8.12 m) Wing area 145.32 sq ft (13.50 sq.m) Height: 10.827 ft / 3.31 m Empty weight 4,409 lb (2,000 kg) Maximum take-off weight 7,460 lb (3,384 kg) Maximum speed 606 mph (975 kph) Initial climb rate 9,252 ft (2,820 m) per minute Service ceiling 48,555 ft (14,800 m) Range 746 miles (1,200 km) Armament: two 23-mm cannon Bombload two 132-lb (60-kg) Crew: 1
Virtually simultaneously with redesign of the Yak-15 to produce the Yak-17, the Yakolev OKB embarked upon the design of a more advanced single-seat fighter, the Yak-19. Utilising a straight-through airflow arrangement, the Yak-19 employed a 12% thickness straight wing. The Yak-19 accommodated all fuel within the fuselage. Of all-metal stressed-skin construction with a semi-monocoque fuselage, the Yak-19 had a laminar-flow wing of TsAGI S-l-12 section, and armament of two 23mm cannon. Equipped with an ejection seat, it was the first Soviet fighter to be fitted with an afterburner, this boosting the thrust of its RD-10F turbojet to 1100kg. The design was tailored round the 2425-lb (1100-kg) afterburning thrust RD-10F located in a straight-through design with a nose inlet and tail exhaust. Two prototypes were built, the first of these entering flight test in January 1947. The second prototype differed in having revised vertical tail surfaces, several degrees of anhedral applied to the horizontal tail and provision for a 200-litre drop tank beneath each wingtip. Difficulties were experienced with the afterburner, and as more powerful turbojets (eg, the RD-500) were by now available, the Yak-19 test programme was terminated on 21 August 1947.
Yak-19 Max take-off weight: 3050 kg / 6724 lb Empty weight: 2200 kg / 4850 lb Wingspan: 8.7 m / 29 ft 7 in Length: 8.36 m / 27 ft 5 in Wing area: 13.5 sq.m / 145.31 sq ft Max. speed: 904 km/h / 562 mph Ceiling: 15000 m / 49200 ft Range: 550 km / 342 miles
Development of the Yakolev Yak-18 by Aleksandr Sergei Yakolev started during the Second World War. During the closing stages of the War, the Yak-18 tandem two-seat primary trainer appeared, entering service with Soviet training elements in 1946. Since the Yak-18 has been progressively developed and has remained in continuous production for over forty years.
The initial Yak-18 tandem two-seat version was powered by the 160 hp M-11 engine in a “helmeted” cowling and tailwheel landing gear.
The Yak-18U featured a tricycle landing gear (the main units which retracted forward) and a lengthened front fuselage.
The Yak-18A was a development of the Yak-18U with a 260 hp AI-14R (later 300 hp AI-14RF) engine, NACA-type cowling, enlarged canopy, and dorsal fin extension.
The Yak-18P single seat development of the -18A was built in two versions. One with the cockpit aft of the wing and forward retracting main wheels. The other with the cockpit over the wing and inward retracting main wheels. There was a fuel system for 5 minutes of inverted flight and longer span ailerons.
The Yak-18PM single seat aerobatic version was produced for the 1966 World Aerobatic Championships was powered by an AI-14RF engine and featured reduced dihedral, and the cockpit further aft than the -18P.
Yak-18PM
The Yak-18PS was similar to the -18PM but with tailwheel landing gear.
Evolved from Yak-18, the Yak-18T has an extensively redesigned cabin, a new fuselage centre section, and a new wing centre section and an increased wing span. The aircraft was designed by the Yakolev Design Bureauas as a multi-role light transport aircraft. The Yak-18T was noticed first in 1967 and over 200 aircraft were built. Production initially ceased in 1989, but was resumed by the Smolensk Aircraft Factory in 1993. While primarily used for training Aeroflot pilots, the Yak-18T was widely used for more generalised flight training, air ambulance and light transport. The Yak-18T is equipped with a 269kW / 300 hp Ivchenko Vedeneyev AI-14RF nine cylinder, air-cooled engine. The 400 hp Vedeneyev M-14P 9-cylinder air-cooled radial engine can also be fitted.
Yak-18T
NATO code name ‘Max’, both the 18PM and 18PC had 300 hp Ivchenko AI14RF engines. The Yakolev Yak-18T is aerobatic-capable, with an inward retractable tricycle landing gear.
Yak-18 Engine: M-11FR, 160 hp / 118kW Max take-off weight: 1112 kg / 2452 lb Empty weight: 810 kg / 1786 lb Wingspan: 10.6 m / 35 ft 9 in Length: 8.0 m / 26 ft 3 in Height: 2.2 m / 7 ft 3 in Wing area: 17.0 sq.m / 182.99 sq ft Max. speed: 248 km/h / 154 mph Ceiling: 4000 m / 13100 ft Range: 1015 km / 631 miles Crew: 2
Yak-18U Seats: 2
Yak-18A Engine: 260 hp AI-14R Seats: 2
Yak-18A Engine: 300 hp AI-14RF Seats: 2
Yak-18P Seats: 1
Yak-18PM Engine: Ivchenko AI-14RF, 300 hp Wingspan: 34 ft 9.25 in / 10.60 m Length: 27 ft 4.75 in / 8.35 m MTOW: 2425 lb / 1100 kg Max level speed: 173 kt / 199 mph / 320 kph ROC SL: 970 fpm / 600 m/min Range max fuel: 217 nm / 250 mi / 400 km Seats: 1
The Yakolev design bureau designed an experimental helicopter with coaxial rotors, the Yak-100, in 1949. It did not progress beyond the experimental stage.
During the autumn of 1946, the Yakolev OKB initiated a relatively modest redesign of the Yak-15 which was initially referred to as the Yak-15U – Uluchshennyi (improved). The prototype, flown early in 1947, differed essentially in having a nosewheel rather than tailwheel undercarriage. Owing to the position of the engine, it was physically impossible to retract the nosewheel completely, and this was therefore partly enclosed by a fixed fairing. Introduction of a nosewheel demanded transfer of the main undercarriage members from the forward to the rear wing spar and dictated considerable structural redesign and a reduction in wing tankage. To compensate, a jettisonable 300-litre tank was added beneath each wing tip. Redesignated Yak-17, this fighter was restressed throughout and, in series form, was fitted with a redesigned vertical tail and an RD-10A engine rated at 1000kg. Armament remained two 23mm NS-23 cannon.
The Yak 17 was powered by the uprated RD 10A rated at 1000 kg (2205 lb) of thrust. The NATO code named Feather was slightly faster and lighter than its competitor, the La 150, and was substantially superior in range; rough field performance of the Yak 17 was very much better than that of the Lavochkin design, which had a heavy narrow track undercarriage. The La 150 was abandoned in April 1947 and the Yak 17 was ordered into production. A second cockpit was added in front of the existing position and a long sliding canopy was fitted; an enlarged fin was also adopted for both the Magnet and Feather. The Yak-17UTI entered flight test in April 1948, and about 150 were eventually built, 20 of these being exported to Poland and several to China.
Yak-17U
One Yak-17 fighter was delivered to Czechoslovakia for evaluation, where it received the designation S 100, and three were supplied to Poland. Poland acquired manufacturing licences in 1950 for both the Yak-17 and its RD-10A turbojet, which were to be built at Mielec and Rzeszow respectively. The Polish programme was terminated in the winter of 1950-51 before any aircraft had been built as the Yak-17 had been overtaken by better fighters, but 30 RD-10 A engines were completed at Rzeszow.
The Yak-17 and Yak-17UTI were phased out by the V-VS in 1951 and 1953 respectively, and the latter from the Polish air arm by 1955.
Production of the Yak-17 from late 1947 to August 1949 and totalled 430, including a proportion of tandem two-seat Yak-17UTI conversion trainers. The Yak 17UTI was the Soviet air force’s first specialist jet trainer and remained in service until replaced by the MiG-15UTI.
Gallery
Engine: RD 10 A, 9810 N / 1000 kp Max take-off weight: 3323 kg / 7326 lb Empty weight: 2430 kg / 5357 lb Wingspan: 9.20 m / 30 ft 2 in Length: 8.78 m / 28 ft 10 in Wing area: 14.85 sq.m / 159.84 sq ft Height: 9.514 ft / 2.9 m Max. speed: 750 km/h / 466 mph Cruise speed: 600 km/h / 373 mph Range: 717 km / 446 miles Service ceiling: 42651 ft / 13000 m Armament: 2x MK 23mm Crew: 1-2
A 1949 ten-passenger transport aircraft powered by two 559kW ASh-21 radial engines.
Engines: 2 x Ash-21, 515kW Max take-off weight: 6400 kg / 14110 lb Empty weight: 5200 kg / 11464 lb Wingspan: 20.0 m / 66 ft 7 in Length: 14.5 m / 48 ft 7 in Max. speed: 370 km/h / 230 mph Cruise speed: 300 km/h / 186 mph Ceiling: 5000 m / 16400 ft Range: 1000 km / 621 miles Crew: 2 Passengers: 10
All Aero 