The Shvetsov ASh-73 was an 18-cylinder, air-cooled, radial

aircraft engine An aircraft engine, often referred to as an aero engine, is the power component of an aircraft propulsion system. Aircraft using power components are referred to as powered flight. Most aircraft engines are either piston engines or gas turbin ...

produced between 1947 and 1957 in the

Soviet Union The Union of Soviet Socialist Republics. (USSR), commonly known as the Soviet Union, was a List of former transcontinental countries#Since 1700, transcontinental country that spanned much of Eurasia from 1922 until Dissolution of the Soviet ...

. It was primarily used as the powerplant for the

Tupolev Tu-4 The Tupolev Tu-4 (; NATO reporting name: Bull) is a piston-engined Soviet Union, Soviet strategic bomber that served the Soviet Air Force from the late 1940s to the mid-1960s. The aircraft was a copy of the American Boeing B-29 Superfortress, ha ...

heavy bomber Heavy bombers are bomber Fixed-wing aircraft, aircraft capable of delivering the largest payload of air-to-ground weaponry (usually Aerial bomb, bombs) and longest range (aeronautics), range (takeoff to landing) of their era. Archetypal heavy ...

, an unlicensed,

reverse engineered Reverse engineering (also known as backwards engineering or back engineering) is a process or method through which one attempts to understand through deductive reasoning how a previously made device, process, system, or piece of software accompl ...

copy of the American

Boeing B-29 Superfortress The Boeing B-29 Superfortress is a retired American four-engined propeller-driven heavy bomber, designed by Boeing and flown primarily by the United States during World War II and the Korean War. Named in allusion to its predecessor, the Bo ...

Design and development

The Shvetsov ASh-73 originated in 1938 from a specification for an 18-cylinder, twin-row, development of the

Shvetsov M-25 The Shvetsov M-25 was an aircraft radial engine produced in the Soviet Union (USSR) in the 1930s and 1940s, a licensed production variant of the Wright R-1820-F3. Design and development The first M-25s were produced from kits imported from the ...

, a license-built 9-cylinder, air-cooled, radial Wright R-1820-F3 Cyclone engine. Development continued through a series of less than successful engines, before culminating in the ASh-73. The ASh-73 was not a reverse-engineered copy of the

Wright R-3350 Duplex-Cyclone The Wright R-3350 Duplex-Cyclone is an American twin-row, supercharged, air-cooled, radial aircraft engine with 18 cylinders displacing nearly . Power ranged from , depending on model. Developed before World War II, the R-3350's design require ...

, itself starting its development in 1937: "There was no need to copy the Wright R-3350-23A; the engine that was put into production was the indigenous ASh-73TK - a further development of the M-71 and M-72, which differed in being fitted with twin TK-19 turbosuperchargers (TK = ''toorbokompressor'')."Gordon and Rigmant, p. 21 rather the ASh-73 was the product of a similar specification. Since the earlier M-25 engines were a licensed copy of the Wright R-1820, there were similarities and some parts were interchangeable between the Duplex Cyclone and the ASh-73 powerplants. The two engines evolved from a common ancestor and to a similar requirement. "In the late 1930s and the early 1940s OKB-19 evolved two 18-cylinder two-row radials — the 2,000-hp M-71 and the 2,250-hp M-72 — which were similar in their design features and production techniques to the Wright Duplex Cyclone engines powering the B-29." The progenitor for the ASh-73 was the M-70. It was tested in late 1938 and was a failure because of cracks in the master

connecting rod A connecting rod, also called a 'con rod', is the part of a reciprocating engine, piston engine which connects the piston to the crankshaft. Together with the crank (mechanism), crank, the connecting rod converts the reciprocating motion of the p ...

and the geared

centrifugal supercharger A centrifugal supercharger is a specialized type of supercharger that makes use of centrifugal force in order to increase intake pressures and power. An increase in combustion intake air pressure allows the engine to burn more fuel, which results i ...

's impeller. The exhaust valves also burnt through. The M-71 of 1939 was the successor to the M-70 and it too was not a success. It used some components from the M-62 engine, but its development was slowed by the German attack on the Soviet Union in 1941. It passed its State acceptance tests in the autumn of 1942, but was not placed into production as there was not any production capacity available, although it was tested on a number of different prototypes during the war. The M-72 of early 1945 was a boosted version of the M-71 and was superseded by the ASh-73 before production could get underway.Kotelnikov, pp. 129–30 The first prototypes of the ASh-73 were built in 1945 and by the end of 1946 testing had completed successfully. The first models to enter production in 1947 lacked turbo-superchargers. They weighed and had during take-off. The ASh-73TK had two TK-19

turbocharger In an internal combustion engine, a turbocharger (also known as a turbo or a turbosupercharger) is a forced induction device that is powered by the flow of exhaust gases. It uses this energy to compress the intake air, forcing more air into th ...

s and an

intercooler An intercooler is a heat exchanger used to cool a gas after compression. Often found in turbocharged engines, intercoolers are also used in air compressors, air conditioners, refrigeration and gas turbines. Internal combustion engines Mo ...

fitted which were direct copies of the units used on the R-3350. The engine was upgraded over the course of its production. On the fourth series of engines the

crankshaft A crankshaft is a mechanical component used in a reciprocating engine, piston engine to convert the reciprocating motion into rotational motion. The crankshaft is a rotating Shaft (mechanical engineering), shaft containing one or more crankpins, ...

nose was changed, the articulated connecting rods were strengthened and the accessory drive was changed. The middle part of the crankcase and the pistons were strengthened and the ignition was improved in the fifth series. In the sixth series the master connecting rod and the crankshaft cheeks were strengthened, the pistons were lightened and shortened. For the seventh series exhaust valves with floating seats were introduced and the reduction gearing was improved. The displacement of the ASh-73 ended up being slightly larger than the Wright Duplex-Cyclone radials of the B-29 - while having the same cylinder count and basic layout, the ASh-73 possessed a 58.122 liter (3,546.8 in3) displacement figure, some 6% larger than its American contemporary's 54.86 L (3,347.9 in3) displacement figure. A boosted version was developed as the ASh-82TKF that had a rating of . It was bench tested, but not put into production. A further development in 1949 was the ASh-73TKFN with

fuel injection Fuel injection is the introduction of fuel in an internal combustion engine, most commonly automotive engines, by the means of a fuel injector. This article focuses on fuel injection in reciprocating piston and Wankel rotary engines. All c ...

that boosted power to , but it too was not built. Another 1949 project was an ASh-73TK with a power-recovery turbine to create a

turbo-compound engine A turbo-compound engine is a reciprocating engine that employs a turbine to recover energy from the exhaust gases. Instead of using that energy to drive a turbocharger as found in many high-power aircraft engines, the energy is instead sent to ...

, but no other information is known.Kay, p. 130 Factory No. 19 began preparation to build the ASh-73 in 1946, but production did not begin until the next year. Production continued there until 1953. Factory No. 36 in Rybinsk also produced it until 1957. A total of 14,310 ASh-73s were built. A number of these were exported to the

People's Republic of China China, officially the People's Republic of China (PRC), is a country in East Asia. With population of China, a population exceeding 1.4 billion, it is the list of countries by population (United Nations), second-most populous country after ...

during the 1950s as spare parts for their Tu-4s.

Applications

Beriev Be-6 The Beriev Be-6 ( USAF/DoD reporting name "Type 34", NATO reporting name "Madge") was a flying boat produced by the Soviet Beriev OKB. It was capable of accomplishing a wide variety of missions, such as long-range maritime reconnaissance, coas ...

Ilyushin Il-18 (1946) The Ilyushin Il-18 (NATO reporting name: Clam) was a Soviet four-engined airliner designed and built by Ilyushin immediately after World War II. Although the aircraft itself was successful, its Shvetsov ASh-73TK engines were too unreliable for ...

Petlyakov Pe-8 The Petlyakov Pe-8 () was a Soviet heavy bomber designed before World War II, and the only four-engine bomber the USSR built during the war. Produced in limited numbers, it was used to bomb Berlin in August 1941. It was also used for so-called " ...

(in service with

Aeroflot PJSC AeroflotRussian Airlines (, ), commonly known as Aeroflot ( or ; , , ), is the flag carrier and the largest airline of Russia. Aeroflot is headquartered in the Central Administrative Okrug, Moscow, with its hub being Sheremetyevo Interna ...

, post-war) *

Tupolev Tu-70 The Tupolev Tu-70 (; NATO reporting name: Cart) was a Soviet Union, Soviet passenger variant of the Tupolev Tu-4, Tu-4 bomber, an unlicensed, Reverse engineering, reverse engineered copy of the Boeing B-29 Superfortress. Designed immediately aft ...

Tupolev Tu-75 The Tupolev Tu-75 () was a military transport variant of the Tu-4 bomber, an unlicensed, reverse engineered copy of the Boeing B-29 Superfortress. The Tu-75 was similar to the Tu-70 airliner, both using a new, purpose-designed fuselage. The fir ...

Tupolev Tu-80 The Tupolev Tu-80 () was a Soviet prototype for a longer-ranged version of the Tupolev Tu-4 bomber, an unlicensed, reverse engineered copy of the Boeing B-29 Superfortress. It was cancelled in 1949 in favor of the Tupolev Tu-85 program which o ...

Specifications (Shvetsov ASh-73TK)

References

Notes

Bibliography