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Yakovlev Piston Trainers & Stunters

v1.1.0 / 01 oct 16 / greg goebel

* Aleksandr Sergeyevich Yakovlev began his career as an aircraft designer for the Soviet state in the 1920s, ultimately developing a wide range of civil and military aircraft. His designs included a number of piston trainers and aerobatics aircraft, some of which were produced in quantity and many of which remain in service in the 21st century. This document provides a history and description of Yak piston trainers and stunter aircraft.

Yakovlev Yak-52


[1] AIR-10 / UT-1 & UT-2
[2] YAK-18 TRAINER / YAK-18U / YAK-18A / CHINESE CJ-6 / YAK-20
[3] YAK-18P-SERIES STUNTERS
[4] YAK-18T
[5] YAK-50 / YAK-52 / YAK-55 / YAK-54 / YAK-152
[6] COMMENTS, SOURCES, & REVISION HISTORY

[1] AIR-10 / UT-1 & UT-2

* Aleksandr Yakovlev started out his work in aircraft development in 1927, building a two-seat biplane for the OSOAVIAKhIM, the Soviet civil aviation society, which promoted aviation among the public and trained youngsters for flying careers, particularly in the military. The biplane, the "AIR-1" -- "AIR" standing for Alexei Ivanovich Rykov, head of the OSOAVIAKhIM -- led to a sequence of other AIR machines, most of them being experimental.

One of the experimentals, the "AIR-8", was a two-seat parasol monoplane trainer. It never went beyond a single prototype, the VVS -- Voyenno Vozdushniye Sily (Red Air Force) deciding it wasn't what the service needed -- and so Yakovlev decided to work on a tandem-seat sports aircraft, the "AIR-9", instead, with the AIR-9 taking to the skies in 1934. It was a low-wing monoplane with spatted taildragger landing gear, powered by a five-cylinder M-11 air-cooled radial engine with 75 kW (100 HP) driving a two-blade fixed-pitch wooden propeller. It was of mixed metal / wood / fabric construction and had an enclosed cockpit.

The AIR-9 was refined into the "AIR-9bis" of 1935, the "bis" being Latin / French for "encore" and roughly translating in aircraft nomenclature as "plus". The AIR-9bis featured a ring cowl over the engine cylinders and an odd forward-sloped windscreen. The forward-sloped windscreen appears to have been a global fad at the time, with a number of contemporary aircraft featuring it; it may have been for improved field of view, but in any case the idea was generally abandoned as quickly as it arose. It is unclear if the AIR-9bis was a rebuild of the original AIR-9 or a new-build aircraft; either way, it didn't go into production.

* Or at least it didn't go into production directly. In 1935 Yakovlev developed a two-seat trainer, the "AIR-10", based on the AIR-9/9bis. The AIR-10 was much like the AIR-9, the major difference being twin open cockpits instead of an enclosed cockpit, with fold-down doors on both sides of each cockpit for access. It did not feature the ring cowl of the AIR-9bis. The AIR-10 won flight competitions sponsored by OSOAVIAKhIM in 1935 and 1936, attracting the attention of the VVS.

The VVS did not find the AIR-10 desireable for service as it was, but saw it as a basis for development to both single-seat and two-seat derivatives. The single-seater, the "AIR-14", performed its first flight in 1936. The AIR-14 was much along the lines of the AIR-10, with the same general airframe configuration except for the single cockpit, and also powered by the M-11 radial engine driving a two-bladed propeller. Evaluation demonstrated that the AIR-14's handling was not entirely benign, but it was seen as useful for advanced flight training for fighter pilots.

The production machine was designed the "UT-1", where "UT" stood for "uchebno trenirovochniyy [samolyot]" or "trainer aircraft", with the aircraft nicknamed the "Utyonok (Duckling)" as a play of words on its designation. It was initially powered by the uprated M-11G engine with 85 kW (115 HP), but later production was fitted with the M-11Ye engine with 110 kW (150 HP). Earlier production machines may have been upgraded to the M-11Ye.

Yakovlev UTI-1

The UT-1 was the first aircraft designed by Yakovlev's OKB (experimental design bureau) to be built in large quantity: total production from 1937 to 1940 was 1,241 aircraft, these aircraft being used for fighter pilot proficiency training and as utility "hacks" for line fighter squadrons. The number of UT-1s built was in excess of requirements and so some were transferred to the OSOAVIAKhIM -- which accepted them with a certain reluctance, the UT-1 being seen as a handful for a novice pilot.


   YAKOVLEV UT-1 (M-11YE ENGINE):
   _____________________   _________________   _______________________
 
   spec                    metric              english
   _____________________   _________________   _______________________

   wingspan                7.3 meters          23 feet 11 inches
   wing area               9.58 sq_meters      103 sq_feet   
   length                  5.75 meters         18 feet 10 inches
   height                  2.34 meters         7 feet 8 inches

   empty weight            429 kilograms       946 pounds
   MTO weight              598 kilograms       1,318 pounds

   max speed at altitude   235 KPH             145 MPH / 125 KT
   service ceiling         4,600 meters        15,100 feet
   range                   670 kilometers      420 MI / 365 NMI
   _____________________   _________________   _______________________

The UT-1 was used for a number of trials, including fits of float and ski landing gear; alternate powerplants such as inverted inlines; and an enclosed cockpit plus retractable landing gear. After Nazi Germany invaded the Soviet Union in June 1941, all the OSOAVIAKhIM UT-1 machines reverted to the VVS, with a number converted to attack configurations -- in several variations, one of the most prominent being the "Moskit (Mosquito)", which had a ShKAS 7.62-millimeter machine gun mounted above each wing and racks under the wings for a total of four RS-82 rockets. Apparently attack-configured UT-1s saw a substantial amount of combat in the defense of the south in 1941 and into 1942. Although obsolescent, it seems to have been a peppy and agile little aircraft, which probably enhanced its survivability. It was unlikely that it was particularly survivable, and it didn't persist in frontline service after more formidable attack aircraft became available.

* As noted above, a two-seat trainer was more directly derived from the AIR-10, this trainer being designated the "UT-2" and taking to the air in 1937. It was much like the AIR-10 except for the tandem seats, with individual open cockpits; use of all wood framing except for a few significant elements; and also reinforcement to permit aerobatics. After experimental fits of both inverted inline and radial engines, in 1938 the UT-2 was put into production with the M-11G engine.

Yakovlev UTI-2

The UT-2 had a tendency to go into a flat spin from which recovery was difficult, thanks to the fact that its center of gravity (CG) was towards the rear of the aircraft, and so the aircraft had an inclination to fly tail-first. A revised production variant was introduced in 1940 to address the spin problem, primarily with a forward fuselage stretch of 15 centimeters (6 inches), along with some alterations of flight surfaces. The 1940 standard UT-2 also featured an M-11D radial engine with 95 kW (125 HP) maximum power. After the modifications, the UT-2 proved highly satisfactory, with production moving on to the "UT-2M" in 1941, this machine featuring revised flight surfaces -- most notably wings with a slight leading-edge sweep -- and other tweaks.


   YAKOVLEV UT-2 (M-11D ENGINE):
   _____________________   _________________   _______________________
 
   spec                    metric              english
   _____________________   _________________   _______________________

   wingspan                10.2 meters         33 feet 5 inches
   wing area               17.1 sq_meters      184 sq_feet   
   length                  7.15 meters         23 feet 6 inches
   height                  2.99 meters         9 feet 10 inches

   empty weight            628 kilograms       1,385 pounds
   MTO weight              940 kilograms       2,073 pounds

   max speed at altitude   210 KPH             130 MPH / 115 KT
   service ceiling         5,000 meters        16,400 feet
   range                   1,130 kilometers    700 MI / 610 NMI
   _____________________   _________________   _______________________

A total of 7,243 UT-2 machines of all variants was built to end of production in 1946, with many provided in the postwar era to Warsaw Pact states. There were a number of trials and experimental fits, for example prototypes with inverted inline engines; a single-seat "Yak-5" fighter trainer, with retractable landing gear; experimental radio-controlled drones; and one machine fitted with hovercraft-style landing gear -- experiments with air-cushion landing gear were conducted in various nations for decades and never amounted to much. There were also bomber and torpedo bomber trainer configurations, as well as combat configurations along the lines of the UT-1 Moskit. However, there's little information that suggests the UT-2 saw much combat.

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[2] YAK-18 TRAINER / YAK-18U / YAK-18A / CHINESE CJ-6 / YAK-20

* In 1942, 13 examples of a "UT-2L" liaison or "limousine" aircraft were built, featuring an enclosed tandem cockpit. A thoroughly revised version of the UT-2L was flown in 1944, featuring not only an enclosed canopy but many other tweaks including fairings over the engine cylinders. Although there was interest in manufacturing it in quantity, the Soviets decided against new production of a wood-construction aircraft.

However, instead of giving up on the design, in early 1945 work began on a derivative aircraft of metal construction, with the first "Yak-18" prototype performing its initial flight on 6 May 1946. It looked very much like the UT-2L externally, the major visible difference being retractable landing gear -- the main gear retracting backward into the wing, the tires remaining exposed after retraction, which helped reduce damage on a wheels-up landing. The wing was flat out to the main landing gear, with a dihedral outboard. The Yak-18 was made largely of aircraft aluminum alloy, with mixed alloy and fabric skinning. It was powered by an M-11FM radial with 105 kW (140 HP), driving a two-blade variable-pitch prop.

Yakovlev Yak-18

A second prototype of refined configuration took to the air in mid-May, this machine having an M-11FR-1 engine providing 120 kW (160 HP). Test pilots praised the Yak-18 for its benign handling, though some changes were required, such as fit of an improved propeller. The Yak OKB offered two configurations, one being a primary trainer, and the other a two-seat aerobatic aircraft; the VVS chose the primary trainer configuration, with the Yak-18 ordered into production in March 1947. Three state factories were assigned to build the trainer: Number 135 in Kharkov, Number 272 in Leningrad, and Number 116 in Semyonovsk (now Arsen'yev). When NATO became aware of the type, it was assigned the reporting name "Max".


   YAKOVLEV YAK-18:
   _____________________   _________________   _______________________
 
   spec                    metric              english
   _____________________   _________________   _______________________

   wingspan                10.06 meters        33 feet
   wing area               17 sq_meters        182.8 sq_feet   
   length                  8.03 meters         26 feet 4 inches
   height                  2.99 meters         9 feet 10 inches

   empty weight            769 kilograms       1,695 pounds
   MTO weight              1,085 kilograms     2,390 pounds

   max speed at altitude   250 KPH             155 MPH / 135 KT
   service ceiling         6,000 meters        19,700 feet
   range                   1,080 kilometers    670 MI / 580 NMI
   _____________________   _________________   _______________________

Initial production Yak-18 trainers were very similar to the second prototype after its equipment refinements; various small tweaks were added through production. The Yak-18 was provided to a number of Soviet client states. The North Koreans apparently used a handful of them for night nuisance bombing raids against South Korean and US forces during the Korean War. A small number of baseline Yak-18 trainers were built in Hungary. China was more enthusiastic, building almost 400 from 1954 to 1958 at a state plant in Nanchang, with the Chinese variant designated the "Chuji Jioalianji (Basic Trainer) 5".

* While the Yak-18 was well-liked, of course consideration was given to improvements. One refinement was tricycle landing gear, the taildragger landing gear arrangement of the first-series Yak-18 being seen as inadequate for training pilots in the handling of modern jet aircraft with tricycle landing gear. Tricycle landing gear also improved the forward field of vision for the pilot and reduced the tendency of an aircraft to flip nose-over in a ground accident. In 1950, a trials Yak-18 was converted to a tricycle landing gear configuration, the nose gear retracting backward, the main gear being moved to the rear of the wings and retracting forward, the wheels in the main gear remaining mostly exposed.


   YAKOVLEV YAK-18U:
   _____________________   _________________   _______________________
 
   spec                    metric              english
   _____________________   _________________   _______________________

   wingspan                10.06 meters        33 feet
   wing area               17 sq_meters        182.8 sq_feet   
   length                  8.13 meters         26 feet 8 inches
   height                  3.25 meters         10 feet 8 inches

   empty weight            882 kilograms       1,944 pounds
   MTO weight              1,166 kilograms     2,570 pounds

   max speed at altitude   230 KPH             140 MPH / 125 KT
   service ceiling         3,300 meters        10,830 feet
   range                   750 kilometers      465 MI / 405 NMI
   _____________________   _________________   _______________________

This experiment working out well, the Yak-18 with tricycle landing gear went into production in 1952 as the "Yak-18U". Along with the tricycle landing gear, the Yak-18U featured a longer forward fuselage; a new and less cluttered cowling design, retaining less prominent "helmets" for the engine cylinders; a wider cockpit, with a windscreen between the seats in case the windshield was shattered by, say, a birdstrike; smaller fuel tanks; and many other tweaks. The Yak-18U was only exported to East Germany. Total production of the first-series Yak-18 and the Yak-18U amounted to 5,680 machines from 1946 into 1957. One was modified for instrument landing training as the "Yak-18T", but there was no follow-up; that designation would be reused, as described below.

* The Yak-18U retained the M-11FR engine, but there had been a desire for a more powerful engine all along, with ongoing experiments in alternate engine fits. In the mid-1950s, the Ivchenko AI-14R became available, this being a nine-cylinder air-cooled radial providing 195 kW (260 HP), and it seemed to fit the bill. A prototype for a Yak-18 was built in early 1956 through modification of a stock Yak-18U, with a second prototype following, also modified from a stock Yak-18U. The new variant was proven in trials into 1957, when it was put into series production. It was originally designated the "Yak-20" but went into service as the "Yak-18A".

Yakovlev Yak-18A

The new engine required a generally revised engine installation, most notably featuring a cylindrical cowling that substantially improved the aircraft's looks. Another noticeable difference was a forward fillet on the tailfin. There were many other less visible tweaks, such as new avionics, a more powerful electrical power generator, and modest reinforcement of the airframe to deal with greater empty weight.


   YAKOVLEV YAK-18A:
   _____________________   _________________   _______________________
 
   spec                    metric              english
   _____________________   _________________   _______________________

   wingspan                10.06 meters        33 feet
   wing area               17 sq_meters        182.8 sq_feet   
   length                  8.18 meters         26 feet 10 inches
   height                  3.25 meters         10 feet 8 inches

   empty weight            1,025 kilograms     2,260 pounds
   MTO weight              1,316 kilograms     2,900 pounds

   max speed at altitude   263 KPH             165 MPH / 140 KT
   service ceiling         5,000 meters        16,400 feet
   range                   725 kilometers      450 MI / 390 NMI
   _____________________   _________________   _______________________

A total of 950 Yak-18A trainers was built into 1960, with the type finally withdrawn from VVS service in 1975. Some were also provided to East Germany and Egypt. The Chinese obtained a sample Yak-18A as a first step towards production of a derivative, with the Shenyang factory performing development and the result, the "CJ-6", being placed into production at Nanchang in 1962. The CJ-6 looked so much like the Yak-18A as to make the two types very easy to confuse, but in reality the CJ-6 was to a large degree a new aircraft. One easily recognized difference was that the tail surfaces of the CJ-6 were angular, not curved as they were in the Yak-18A; another was that the main gear on the CJ-6 retracted towards the fuselage, not forward.

Nanchang CJ-6

The CJ-6 was, however, powered by the AI-14R engine -- or more precisely a Chinese copy of it, the "Huosai (Piston Engine) Type 6A (HS-6A)". An improved version of this engine was introduced in 1965, with CJ-6 production adopting it, the new trainer variant being designated the "CJ-6A". A handful of armed "CJ-6B" counter-insurgency (COIN) were built as well. Over 2,000 CJ-6 machines were built for Chinese service, with about 200 more being exported. The CJ-6 is a popular "warbird", being lively to fly and sturdy, with the type being a relatively common sight at airshows around the world.

* It should be noted that in the late 1940s, the Yak OKB developed another aircraft with the designation of "Yak-20" -- this aircraft intended to be a simple, cheap, docile trainer for air club service. As it emerged, the Yak-20 was a low-wing aircraft with fixed taildragger landing gear; metal tube construction with mixed aluminum alloy / fabric skinning; and an AI-10 five-cylinder radial engine with 60 kW (80 HP) driving a two-bladed variable-pitch prop. The Yak-20 had a simple rounded cowling instead of the Yak-18's helmeted cowling; it also had a side-by-side cockpit -- unusual among Soviet trainers, this configuration being seen as preferable to tandem seating for training very novice pilots, the flight instructor being able to physically interact with the trainee.

Yakovlev Yak-20

Flight evaluation demonstrated that the Yak-20 was everything hoped of it, being very pleasant to fly, with no handling quirks worth worrying about, and fully aerobatic. It was no hot-rod, of course, but performance wasn't the design objective. However, the state evaluation concluded that the Yak-20 should be brought up to roughly the same level of capability as the Yak-18. That led to a revised second prototype built to more robust standard, with the machine proving overweight and demonstrably inferior to the Yak-18. The Yak-20 program was given the axe -- thanks to the authorities refusing to leave well enough alone, and no doubt with OKB engineers muttering acid comments. A single-seat "Yak-22" variant was considered as well, but it never flew.

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[3] YAK-18P-SERIES STUNTERS

* The Yak-18A was seen as a useful basis for a single-seat stunter aircraft, intended for use by DOSAAF -- the youth air organization, descendant of the OSOAVIAKhIM, with DOSAAF providing flight training for youngsters with an eye to future military or civil air service. Accordingly, a Yak-18A was modified to a single-seat configuration by deleting the front seat, the resulting abbreviated canopy being set well back. This machine, designated the "Yak-18P" -- the "P" standing for "Pilotazhniy (Aerobatic)" -- or possibly the "Yak-18AP", was otherwise much like the Yak-18A, the only incidental changes being some modifications of flight surfaces and tweaks to the engine system for fully aerobatic flight. The conversion was performed in 1958 and underwent flight tests in 1959.

Roughly in parallel, a second Yak-18P prototype was put together, as a new-build aircraft, this machine having the rear seat deleted and the single-seat cockpit set forward. It also had inward-retracting landing gear. According to some sources, this machine's configuration was the one intended for production all along, but it was wrecked in a hard landing during an international aeronautical competition; the Yak-18AP was, according to the tale, put together in a hurry as a replacement for the competition.

In any case, the Yak-18P with the forward canopy went into production -- it's not clear at what plant -- featuring engine system modifications for inverted flight; considerable tweaking of flight surfaces, with more area on all of them; addition of a third fuel tank; elimination of all unnecessary kit; and airframe reinforcement for stunt flying. The Soviet national stunt flying team flew the Yak-18P in the World Aerobatic Championships in 1962 and 1964.

* The Yak-18P was well-regarded, but it had a few defects. The forward-set canopy, though it made take-offs and landings easier, was not particularly optimum for stunt flying, making it more difficult to see and feel what the aircraft was doing. In addition, the outboard-wing dihedral of the Yak-18P led to stability problems in inverted flight.

Tweaks were applied, resulting in the "Yak-18PM", the "M" effectively standing for "Modified". The most obvious change was moving the cockpit back to the rear of the wing, but it also had a more powerful AI-14RF engine, with 225 kW (300 HP); structural reinforcement; less wing dihedral; and control surface tweaks. The Yak-18PM raked in the trophies at the World Aerobatics Championships in 1966, and became a common sight at Soviet air clubs over the next decade.


   YAKOVLEV YAK-18PM:
   _____________________   _________________   _______________________
 
   spec                    metric              english
   _____________________   _________________   _______________________

   wingspan                10.06 meters        33 feet
   wing area               17 sq_meters        182.8 sq_feet   
   length                  8.18 meters         26 feet 10 inches
   height                  3.25 meters         10 feet 8 inches

   empty weight            950 kilograms       2,095 pounds
   MTO weight              1,100 kilograms     2,425 pounds

   max speed at altitude   320 KPH             200 MPH / 175 KT
   service ceiling         6,700 meters        22,000 feet
   range                   400 kilometers      250 MI / 220 NMI
   _____________________   _________________   _______________________

Early production Yak-18PM stunters featured an airbrake, but stunt pilots rarely used it -- apparently real stunt pilots don't use airbrakes -- and so it was eventually deleted. Late production machines also had cropped, squared-off wingtips and wider rudders. One Yak-18PM was also experimentally fitted with a Gulshenkov TVD-10 turboprop, providing 685 kW (920 EHP) and driving a three-bladed propeller, but that configuration didn't enter production.

Yakovlev Yak-18P

* The Yak-18PM didn't do so well in aerobatic competitions in 1968, and so Yak OKB engineers sat down to think of what might be done to refine it. The number one issue was to cut weight, and it turned out that an easy way to do that was to revert to taildragger landing gear -- a tailwheel was obviously lighter than a nosewheel assembly. That and other tweaks cut the weight by 100 kilograms (220 pounds); there were other minor changes to improve handling. A handful of tailwheel conversions were performed, with these machines designated "Yak-18PS", the "S" standing effectively for "Special". They were assigned to the Soviet national aerobatics team for competitive use.

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[4] YAK-18T

* In the mid-1960s, the Yak OKB set out to design a four-place utility aircraft based on the Yak-18PM. As it emerged, the "Yak-18T" -- recycling the designation of the Yak-18T trainer prototype, in this case with "T" effectively standing for "Transport" or "Taxi" -- was a Yak-18PM with a new fuselage, retaining some Yak-18PM assemblies but also tweaking much of what was inherited. Initial flight of a prototype was in 1967, with the type being displayed at the Paris Air Show in that year, and going into production in 1973.

As it emerged, the Yak-18T was a tidy aircraft, clearly reflecting its Yak-18 heritage, but just as clearly much different from its predecessors. It had the same general flight surface and landing gear arrangement -- tricycle configuration, with inward-retracting main gear -- as the Yak-18PM, and was powered by an AI-14RF engine, providing 225 kW (300 HP) and driving a two-bladed variable-pitch propeller. Later production had the M-14P engine with 270 kW (360 HP), plus an improved propeller.


   YAKOVLEV YAK-18T:
   _____________________   _________________   _______________________
 
   spec                    metric              english
   _____________________   _________________   _______________________

   wingspan                11.16 meters        36 feet 8 inches
   wing area               18.8 sq_meters      202.4 sq_feet   
   length                  8.39 meters         27 feet 6 inches
   height                  3.4 meters          11 feet 2 inches

   empty weight            1,215 kilograms     2,685 pounds
   MTO weight              1,650 kilograms     3,640 pounds

   max speed at altitude   260 KPH             155 MPH / 135 KT
   service ceiling         4,000 meters        13,000 feet
   range                   750 kilometers      465 MI / 405 NMI
   _____________________   _________________   _______________________

Of course the fuselage was very different, with two rows of two seats, a car-type door on each side, and a baggage hold door on the left behind the wing. There was a step behind the left wing for getting in and out, and dual controls were standard. Production machines had revised windows, plus a larger tailfin with a forward fin fillet -- arguably improving the aircraft's already good looks.

Yakovlev Yak-18T

Production was performed at State Factory 475 in Smolensk, with 537 machines built to end of (first run) production in 1982. When used as a primary trainer, the Yak-18T had seats dished out to accommodate parachutes worn by trainee and instructor; otherwise the Yak-18T had comfortable car-type seats. One machine was kitted out as an air ambulance, the "Yak-18TS", with fittings for a stretcher and medical attendant; although the Yak-18TS was recommended for series production, it didn't happen.

* The Yak-18T proved popular, also being a common sight at DOSAAF air clubs, where it was often used as an advanced aerobatics trainer. The Soviet Ministry of Civil Aviation ordered the Yak-18T phased out in 1987, with the aircraft to be scrapped; about half had gone to the wreckers when some alert official at the ministry hastily intervened, with many of the survivors going to DOSAAF and others going into storage, to end up in private hands in the 1990s.

Indeed, in the early 1990s the post-Soviet Tekhnoavia Joint Stock Company decided to put the Yak-18T back into production. In the new Russia there was a need for a small touring and business aircraft that would be substantially cheaper than foreign imports, and the Yak-18T fit the bill. Production was reinstated at the Smolensk plant in 1993, with at least 90 Yak-18T machines built, a third of them exported. They were generally similar to the Soviet Yak-18T aircraft, with minor improvements, such as a step behind each wing instead of just the left wing, and more comfortable accommodations.

Tekhnoavia also floated plans for upgrades, under the general designation of "SM-94" -- featuring such tweaks as a prop spinner, modifications for streamlining, optional wingtip tanks, an updated interior with seats for six, and modernized avionics. A number of such conversions were sold. There was consideration of a combat-capable SM-94 with underwing pylons for unguided rocket pods or other stores, but it doesn't appear any such conversions were performed. There were also plans for a substantially uprated "Yak-18TM" with new flight surfaces, which would also be combat-capable, but at last notice it hadn't happened.

BACK_TO_TOP

[5] YAK-50 / YAK-52 / YAK-55 / YAK-54 / YAK-152

* From the late 1960s, consideration was given to a follow-on to the Yak-18P series stunters, leading to the construction of three "Yak-50" prototypes. As it emerged, the Yak-50 looked so similar to the Yak-18PS taildragger stunter as to be hard to tell from it, but the Yak-50 was generally a new aircraft, very different at the detail level.

Yakovlev Yak-50

It was powered by a Vedeneyev M-14P radial engine providing 270 kW (360 HP), driving a two-bladed variable-pitch propeller. A total of 312 production Yak-50 stunters was built at the state factory in Arsen'yev between 1973 and 1986.


   YAKOVLEV YAK-50:
   _____________________   _________________   _______________________
 
   spec                    metric              english
   _____________________   _________________   _______________________

   wingspan                9.5 meters          31 feet 2 inches
   wing area               15 sq_meters        161.5 sq_feet   
   length                  7.68 meters         25 feet 2 inches
   height                  3.2 meters          10 feet 6 inches

   empty weight            780 kilograms       1,720 pounds
   MTO weight              915 kilograms       2,020 pounds

   max speed at altitude   320 KPH             200 MPH / 175 KT
   service ceiling         5,500 meters        18,045 feet
   range                   390 kilometers      240 MI / 210 NMI
   _____________________   _________________   _______________________

Working backwards from the Yak-50, the Yak OKB also developed a two-seat basic trainer echoing the Yak-18A, originally designated the "Yak-50U" but emerging as the "Yak-52", with a tandem-seat cockpit and tricycle landing gear -- the wheels could be easily swapped out with skis if necessary. It was also powered by the M-14P radial; it could be fitted with a tow hook for hauling sailplanes aloft.

Yakovlev Yak-52

Manufacture was actually performed in Romania, in a plant at Bacau, which became the Aerostar organization after the fall of the Soviet bloc. Almost 1,700 Yak-52 trainers -- labeled as "Iak-52" in Romania -- were built between 1977 and 1991, most of them going to the USSR, the machine being yet another common sight at DOSAAF air clubs.


   YAKOVLEV YAK-52:
   _____________________   _________________   _______________________
 
   spec                    metric              english
   _____________________   _________________   _______________________

   wingspan                9.5 meters          31 feet 2 inches
   wing area               15 sq_meters        161.5 sq_feet   
   length                  7.676 meters        25 feet 2 inches
   height                  2.7 meters          8 feet 10 inches

   empty weight            1,000 kilograms     2,200 pounds
   MTO weight              1,290 kilograms     2,840 pounds

   max speed at altitude   285 KPH             175 MPH / 155 KT
   service ceiling         6,000 meters        19,685 feet
   range                   550 kilometers      340 MI / 300 NMI
   _____________________   _________________   _______________________

In recent decades, many used Yak-52s have found their way into the hands of Western collectors, with the type being often found at airshows. From the late 1990s, Aerostar has produced an enhanced version, the "Yak-52W", with the "W" effectively standing for "Westernized". It has fuel tanks in the wings, doubling its range, and also can be fitted with wingtip tanks. It features Westernized avionics; a three-bladed prop with a spinner; and various small refinements, for example use of aluminum-sheathed control surfaces instead of using fabric covering.

Aerostar has also come up with special derivatives, including:


Aerostar Yak-52

The Russian Air Force developed its own modernized "Yak-52M" upgrade, with initial flight in 2003. The most visible change is a new bulged canopy to improve field of view, the seat for instructor in the back being raised, with the two aircrew also sitting on Zvezda SKS-94MYa "zero-zero" (zero speed, zero altitude) ejection seats -- ejection seats being a somewhat unusual feature for a small piston aircraft, but sensible given the Yak-52M's use as a trainer. It also features a modernized M-14X engine driving a three-bladed propeller with a spinner, more fuel capacity, minor revisions to flight surfaces, and generally updated avionics. The VVS wanted to upgrade their Yak-52 primary trainer fleet to Yak-52M standard, but nothing happened.

* A single "Yak-53" stunter was built in the early 1980s, this machine being a single-seat derivative of the Yak-52, or more or less a Yak-50 with tricycle landing gear. In 1982, the prototype set a number of records in its class, but it never went into production. At that time the Yak OKB was instead focusing on a completely new design stunter, which would emerge as the "Yak-55". After some zigs and zags -- two initial prototypes built in 1982 being judged unsatisfactory, resulting in a redesign -- the Yak-55 entered production at Arsen'yev in 1985, with about a hundred built for Soviet stunt pilot teams and DOSAAF.

As it emerged, the Yak-55 was a sporty-looking, minimalist single-seat aircraft with taildragger landing gear; mid-mounted wings; an M-14P radial driving a two-bladed variable-pitch propeller; and forward-mounted bubble canopy. It looks like one really fun toy, made purely for the joy of stunt flying, something not at all traditionally associated with the Russian mindset.


   YAKOVLEV YAK-55M:
   _____________________   _________________   _______________________
 
   spec                    metric              english
   _____________________   _________________   _______________________

   wingspan                8.1 meters          26 feet 7 inches
   wing area               17 sq_meters        182.8 sq_feet   
   length                  7.29 meters         23 feet 11 inches
   height                  2.2 meters          7 feet 3 inches

   empty weight            690 kilograms       1,520 pounds
   MTO weight              855 kilograms       1,855 pounds

   max speed at altitude   285 KPH             175 MPH / 155 KT
   service ceiling         4,000 meters        13,115 feet
   range                   595 kilometers      370 MI / 320 NMI
   _____________________   _________________   _______________________


Yakovlev Yak-55

A modernized version, the "Yak-55M", went into production in 1990, this variant featuring revised wings with shorter span but more area; roughly another hundred machines were built. A decade later the Tekhnoavia firm introduced a further refined variant, the "SP-55M Slava", with a revised tailfin, revised canopy and rear fuselage, and a more powerful M-14PF engine providing 300 kW (400 HP) and driving a three-bladed variable-pitch propeller. The SP-55M remains in production.

* The Yak-55 proving satisfactory, the Yak organization decided to build a two-seat follow-on, which emerged as the "Yak-54", going into production in the mid-1990s. It has the same broad configuration as the Yak-55, aside from the tandem-seat cockpit, being a mid-wing taildragger machine with an M-14P engine -- but features considerable redesign, being distinctly different and more rakish in appearance, with a three-bladed propeller from the outset.

Yakovlev Yak-54

It was intended for use both as an aerobatics trainer and for aerobatics competitions, and has been sold both domestically and on the export market. It remains in production.


   YAKOVLEV YAK-54:
   _____________________   _________________   _______________________
 
   spec                    metric              english
   _____________________   _________________   _______________________

   wingspan                8.15 meters         26 feet 9 inches
   wing area               12.89 sq_meters     138.75 sq_feet   
   length                  6.91 meters         22 feet 8 inches
   height                  1.65 meters         5 feet 5 inches

   empty weight            769 kilograms       1,695 pounds
   MTO weight              990 kilograms       2,185 pounds

   max speed at altitude   450 KPH             280 MPH / 245 KT
   service ceiling         4,000 meters        13,125 feet
   range                   700 kilometers      435 MI / 380 NMI
   _____________________   _________________   _______________________

A number of other Yak designs for piston trainers and stunters have been considered. In parallel with the development of the Yak-54, Yak OKB engineers considered a similar two-seater, the "Yak-56", with retractable landing gear, plus a "Yak-57" single-seater derived from it, but they never happened. Similarly, a "Yak-54M" primary trainer was also proposed, this design actually being distinctly different from the original Yak-54, in particular featuring retractable tricycle landing gear. It didn't happen, either.

The Yak-54M was used, however, as the starting point for a similar machine, the "Yak-152" -- the airframe being similar, but powered by a German-made RED A03 diesel engine. It also features ejection seats and modernized avionics to support the training role, and can carry external stores for weapons training and, possibly, light attack. Initial flight was in 2016, with the VVS ordering 150 in the same year.

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[6] COMMENTS, SOURCES, & REVISION HISTORY

* There were a fair number of aircraft in Yakovlev's early AIR series, some described elsewhere, a few of which (that never entered production) are worthy of a brief mention here:


Yakovlev UT-21

* As concerns copyrights and permissions for this document, all illustrations and images credited to me are public domain. I reserve all rights to my writings. However, if anyone does want to make use of my writings, just contact me, and we can chat about it. I'm lenient in giving permissions, usually on the basis of being properly credited.

* Sources include:

Some minor details were also picked up off the online Wikipedia.

* Revision history:

   v1.0.0 / 01 dec 12
   v1.0.1 / 01 nov 14 / Review & polish.
   v1.1.0 / 01 oct 16 / Added Yak-152.
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