Яковлев Як-15: Первый советский реактивный истребитель

Soviet first generation turbojet fighter

The Yakovlev Yak 15 (Яковлев Як 15; NATO reporting name: Feather, USAF/DOD designation Type 2) was a first generation Soviet turbojet fighter developed by the Yakovlev design bureau (OKB) immediately after World War II. The main fuselage was that of Yakovlev Yak 3 piston engine fighter modified to mount a reverse engineered German Junkers Jumo 004 engine. The Yak 15 and the Swedish Saab 21R were the only two jets to be successfully converted from piston power to enter production. 280 aircraft were built in 1947. Although nominally a fighter, it was mainly used to qualify piston engine experienced pilots to fly jets.

On 9 April 1945, the Council of People's Commissars ordered the Yakovlev OKB to develop a single seat jet fighter to be equipped with a single German Jumo 004 engine. To save time, Yakovlev based the new design (known as the Yak 3 Jumo or Yak Jumo) on the latest version of his successful Yakovlev Yak 3 piston engined fighter. The piston engine was removed and the jet engine was mounted underneath the forward fuselage so that its exhaust exited underneath the middle of the fuselage. To protect the fuselage, a steel heatshield was added to its bottom. The deeper forward part of the fuselage caused the configuration of the aircraft to resemble a "pod and boom". Very few changes were made to the metal fuselage other than at the aircraft's nose. This was recontoured to accommodate the armament of two Nudelman Suranov NS 23 autocannon, an additional fuel tank above the engine and the engine itself. No changes were made to the wings other than the elimination of the air intakes for the oil cooler and the bending of the front wing spar into an inverted U shape to clear the engine. The vertical stabilizer was slightly enlarged, but the tailplane was unmodified. The conventional landing gear was also unmodified other than the tailwheel which now used several steel leaf springs as shock absorbers. The Yak Jumo carried a total of of fuel. Taxi tests began in October 1945, but the heatshield proved to be too short and the heat from the engine exhaust melted the duralumin skin of the rear fuselage as well as the rubber tire of the tailwheel. Modifications to rectify the problems took until late December. By this time a second prototype had been completed with a solid steel tailwheel and an enlarged tailplane. After a few taxiing tests, it was transferred to the Central Aerohydrodynamic Institute (TsAGI) for full scale windtunnel testing that lasted until February 1946. On the 26th of that month, the Council of People's Commissars issued requirements that the aircraft should have a maximum speed of at sea level and a speed of at an altitude of It should be able to climb to that altitude in 4 1/2 minutes or less and it should have a range of at 90% of maximum speed. Two prototypes were to be ready for flight testing on 1 September. The Mikoyan Gurevich OKB was developing the MiG 9 at the same time. According to aviation historians Bill Gunston and Yefim Gordon, representatives from Yakovlev and Mikoyan Gurevich tossed a coin on 24 April 1946 to determine which aircraft would be the first Soviet jet to fly. Yakovlev lost and the Yak Jumo made one circuit of the airfield before landing. The manufacturer's flight testing of the aircraft was completed on 22 June, but its early success caused the Council of Ministers to issue a new requirement on 29 April for two aircraft powered by the Soviet built RD 10 engine (known as the Yak 15, Yak 15RD10 or Yak RD). Aside from the new engine, the requirement differed from the previous one only in a range of at optimum cruise speed and a reduction of the maximum ceiling to Two prototypes were ordered to be available for flight testing on 1 September 1946. The tests revealed a number of problems in that the thick wing inherited from the Yak 3 limited the top speed of the aircraft, the engine exhaust damaged the surface of the airfield, the cockpit often filled with smoke from kerosene and oil that had dripped onto the engine, and the aircraft was very short ranged. Despite these problems, the Yak 15 proved to be very easy to fly, even for pilots accustomed to piston engined fighters, and caused the VVS to accept the fighter as a conversion trainer. Even before the State acceptance trials were completed, the Council of Ministers ordered the aircraft into production in December 1946. 50 aircraft were to be built between January and April 1947, equally split between single seat aircraft and two seat trainers, armed with only a single cannon. The trainer ran into serious development difficulties and all the aircraft of the first batch were single seaters. Fifty of these participated in the May Day flypast in Moscow in 1947. A total of 280 Yak 15s were produced through the end of the year, exclusive of prototypes. The aircraft were distributed in small numbers to fighter aviation regiments based in the USSR, Poland, Romania, Hungary, and Manchuria for use as conversion trainers. The aircraft's manoeuvrability led it to be used by a number of informal acrobatic display teams throughout the late 1940s. A single prototype of the two seat trainer was the first aircraft of the first production batch built by Factory No. 31 in the fall of 1946. The prototype did not begin manufacturer's flight testing until 5 April 1947, even though the primary differences from the single seat version were limited to a redesigned forward fuselage that accommodated an additional cockpit for the trainee where the armament used to be and a sideways opening, canopy. The trainer was initially designated as the Yak Jumo vyvoznoy, but it was eventually designated as the Yak 21 although some documents refer to it as the Yak 15V, Yak 15UT or Yak 21V. Further work on the trainer was cancelled with the success of the trainer version of the Yak 17 with its tricycle undercarriage. One Yak 15 was used to test a prototype aerial refueling system in 1949, although the installation on the fighter and the Tupolev Tu 2 bomber used as the tanker were both dummies to test procedures and fit.

Only one Yak 15 survives, 'Yellow 37' at the Vadim Zadorozhny Technical Museum outside Moscow. It was purchased by the technical museum when the Yakovlev OKB's museum was liquidated in 2006.