Yakovlev Yak-25 (1947)
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__NOTOC__ The Yakovlev Yak-25 was a
Soviet The Soviet Union,. officially the Union of Soviet Socialist Republics. (USSR),. was a transcontinental country that spanned much of Eurasia from 1922 to 1991. A flagship communist state, it was nominally a federal union of fifteen nation ...
military aircraft, an early turbojet-powered fighter aircraft designed by the
Yakovlev The Joint-stock company, JSC A.S. Yakovlev Design Bureau (russian: ОАО Опытно-конструкторское бюро им. А.С. Яковлева) is a Russian aircraft designer and manufacturer (design office prefix Yak). Its head offi ...
OKB OKB is a transliteration of the Russian initials of "" – , meaning 'experiment and design bureau'. During the Soviet era, OKBs were closed institutions working on design and prototyping of advanced technology, usually for military applications. ...
. The designation was later reused for a different interceptor design. Tasked by the Council of Ministers in a directive issued on 11 March 1947, with producing a straight winged fighter similar to the earlier Yak-19, but powered by a Rolls-Royce Derwent V, OKB-115 swiftly produced the Yak-25, which blazed several trails as the first Soviet fighter with a fully pressurised cockpit, air conditioning, jettisonable canopy, and hydraulic airbrakes on the fuselage amongst other innovations.Gunston, 1997


Development

The Yak-25 closely followed the Yak-19 in layout if not in detail. The straight wings, though similar in planform, were fractionally larger and much thinner (9% t/c throughout), using laminar flow sections. The CAHI flaps were also hydraulically powered. The vertical tail unit differed from the Yak-19 in being swept back at 40° on the leading edge, while the horizontal tail was swept back at 35 degrees.Gunston, 1997 The Derwent V engine was attached to the rear of the centre fuselage in a manner similar to the Yak-19. Though the fuselage had a different non-circular cross-section from the Yak-19, a similar double bulkhead directly behind the wing allowed the rear fuselage to be completely removed, giving access to the engine for removal or maintenance. The undercarriage was very similar to the Yak-19.Gunston, 1997 The cockpit was very similar to the earlier Yakovlev jets, though the Yak-25 was pressurized using an air-cycle system based on engine bleed. The single aft-sliding canopy was powered. The bulletproof front windscreen was 57 mm thick, while 8 mm of armor protected the pilot from behind. The ejection seat was an improvement over the Yak-19, with a longer stroke gun, and leg restraints. Armament was also improved, with three NR-23 cannon, each with 75 rounds.Gunston, 1997


Testing

The Yak-25-I was given the callsign "yellow 15", and had a number "2" painted on the airbrake rudder. It was flown in factory testing by Anokhin between 31 October 1947 and 3 July 1948.Gunston, 1997 Flight tests followed quickly, and showed that the Yak-25 was easy to fly, and had exceptional performance and maneuverability for a straight-wing aircraft. Unfortunately it soon became clear that the laminar flow section used for the tail unit was totally unsuitable, with extremely severe buffeting setting in at 500 km/h (310 mph). Test pilot L.L. Selyakov reporting that the buffeting was so bad that he was thrown about in the cockpit, banging his head on the canopy, and the needles fell off all the flight instruments. The tailplane section was changed with much improved results. Worse yet, both its rivals, the
Lavochkin La-15 The Lavochkin La-15 ( Plant 21 product code Izdeliye 52, USAF reporting name Type 21, NATO reporting name Fantail), was an early Soviet jet fighter and a contemporary of the Mikoyan-Gurevich MiG-15. Design and development Lavochkin had produced ...
and rival swept-wing
MiG-15 The Mikoyan-Gurevich MiG-15 (russian: Микоя́н и Гуре́вич МиГ-15; USAF/DoD designation: Type 14; NATO reporting name: Fagot) is a jet fighter aircraft developed by Mikoyan-Gurevich for the Soviet Union. The MiG-15 was one of ...
had superior performance, with the Mig-15 selected for mass production and the La-15 produced in relatively small numbers (235). Yakovlev was never again to build a single-engine fighter superior to the rival aircraft coming from OKB Mikoyan-Gurevich, though neither was OKB Lavochkin. Development was halted, but two of the prototypes were used for test and development purposes.Gunston, 1997 The Yak-25 never received an ASCC reporting name or USAF type number despite being known to the west at the time.Gunston, 1997


Experimental work

Further development, replacing the straight wing with one of 35° sweepback, was undertaken as the Yak-30.Gunston, 1997


Yak-25E

The Yak-25E (Eksperimentalnyi) was the Yak-25-II specially modified to be towed by a
Tupolev Tu-4 The Tupolev Tu-4 (russian: Туполев Ту-4; NATO reporting name: Bull) is a piston-engined Soviet strategic bomber that served the Soviet Air Force from the late 1940s to mid-1960s. It was reverse-engineered from the American Boeing B-29 ...
strategic bomber. This came in response to a proposal by the headquarters of Long Range Aviation, calling for a method of towing short-range jet fighters, code-named ''Burlaki'' (barge hauler).Gunston, 1997 Production aircraft would have used Klimov RD-500 engines. At the same time the Soviets were developing the Yak-25E, the U.S. Air Force was experimenting with a similar system known as Project Tom-Tom. The U.S. system would have employed either a specially modified
F-84 The Republic F-84 Thunderjet was an American turbojet fighter-bomber aircraft. Originating as a 1944 United States Army Air Forces (USAAF) proposal for a "day fighter", the F-84 first flew in 1946. Although it entered service in 1947, the Thu ...
or an
XF-85 Goblin The McDonnell XF-85 Goblin is an American prototype fighter aircraft conceived during World War II by McDonnell Aircraft. It was intended to deploy from the bomb bay of the giant Convair B-36 bomber as a parasite fighter. The XF-85's intended ...
parasite aircraft. Early attempts differed by attaching two fighters to the bomber's wingtips. Later plans called for a
parasite aircraft A parasite aircraft is a component of a composite aircraft which is carried aloft and air launched by a larger carrier aircraft or mother ship to support the primary mission of the carrier. The carrier craft may or may not be able to later reco ...
to be stowed internally within the belly of a
B-36 The Convair B-36 "Peacemaker" is a strategic bomber that was built by Convair and operated by the United States Air Force (USAF) from 1949 to 1959. The B-36 is the largest mass-produced Reciprocating engine, piston-engined aircraft ever built. It ...
.


Specifications (Yak-25 c/n 115001)


See also


References


Bibliography

* Gordon, Yefim. "Early Soviet Jet Fighters". Hinkley: Midland. 2002. * * Green, William & Swanborough, Gordon. "The Complete Book of Fighters". London: Salamander Books. 1994. * Gunston, Bill. ''The Osprey Encyclopedia of Russian Aircraft 1875-1995''. London: Osprey, 1995. . * Gunston, Bill. ''Yakovlev Aircraft since 1924''. London, UK: Putnam Aeronautical Books, 1997. . {{Soviet straight-winged jet fighters 1940s Soviet fighter aircraft Yak-025 1947 Abandoned military aircraft projects of the Soviet Union Single-engined jet aircraft Mid-wing aircraft Aircraft first flown in 1947