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| Shvetsov ASh-73 | |
|---|---|
| Name | ASh-73 |
| Caption | Shvetsov ASh-73 radial engine |
| Country | Soviet Union |
| Manufacturer | Shvetsov |
| First run | 1947 |
| Produced | 1947–1950s |
| Type | 18-cylinder radial piston engine |
| Bore | 155 mm |
| Stroke | 170 mm |
| Displacement | 58.1 L |
| Power | 2,400–2,800 hp |
Shvetsov ASh-73 is a Soviet 18-cylinder, twin-row radial aircraft piston engine developed in the late 1940s and used primarily on heavy piston-engined transport and bomber aircraft. It represents the culmination of the Shvetsov design bureau's piston-engine work derived from earlier radial families, providing increased power for post‑World War II designs and for a transitional period before wide turboprop adoption. The ASh-73 became the powerplant for several notable Tupolev and Ilyushin types and influenced Soviet aeronautical propulsion policy during the early Cold War.
The ASh-73 evolved from the earlier M-25 and ASh-82 lineage designed by the Shvetsov bureau under the direction of designers associated with the legacy of Mikulin and Dobrynin engine schools, with organizational links to NKAP and later MAP. Development traces included comparative studies with contemporaneous Western designs such as the Wright R-3350 and design lessons from wartime production experience with engines used on Lavochkin, Yakovlev, and Petlyakov aircraft. Initial bench and flight testing began in the immediate postwar period at facilities associated with TsAGI and NII-1, and the engine received iterative upgrades to increase power and reliability while adapting to Soviet fuel and oil standards governed by agencies like Gosstandart.
Certification and deployment decisions were influenced by strategic planners in Soviet Air Forces and aircraft manufacturers including Tupolev Design Bureau and Ilyushin Design Bureau, as they sought replacements for wartime powerplants on heavy transports and long-range bombers. The ASh-73 incorporated improved supercharging and strengthened crankcase design developed with metallurgical support from institutes such as TsNIIChM and production methods refined at plants that had built earlier Shvetsov engines.
The ASh-73 is an 18-cylinder, two-row, air-cooled radial engine with a 58.1-litre displacement, employing a single-stage two-speed centrifugal supercharger and contra-rotating propeller gear options in certain variants. The power unit used forged steel crankshafts, nitrided cylinder barrels, and aluminum alloy crankcases produced with precision techniques influenced by staff from Zaporozhsky Automobile Plant collaborations; lubrication and cooling systems were adapted to harsh operating environments encountered in Arctic service with units like Long Range Aviation.
Valve train design combined hydraulic tappets with robust pushrods and rocker arms similar in concept to earlier Pratt & Whitney practice, while ignition systems used dual magnetos developed in coordination with Elektron enterprises. Fuel delivery relied on precise carburetors patterned after wartime designs and later modified for higher octane fuels available from refineries tied to Gosplan directives. The engine had a dry weight and power-to-weight ratio that enabled cruise and maximum power outputs suitable for heavy airframes such as the Tupolev Tu-4 derivatives and the Ilyushin Il-12.
Operational deployment began in the late 1940s with service entries on strategic and transport types operated by units of Aeroflot and Soviet Air Forces. The engine saw use on long‑range patrols, transport runs to remote bases in Siberia and the Far East, and on prototype long‑distance flights organized by figures such as Valery Chkalov's successors in Soviet aviation promotion. Maintenance experience in field conditions led to iterative factory retrofits and overhaul procedures developed by repair depots linked to VVS logistics chains. Reliability was generally acceptable for its class but was eventually superseded by turboprop and turbojet installations developed at establishments like Kuznetsov and Ivchenko-Progress.
A number of factory and experimental variants addressed different power, accessory, and installation requirements. Production variants included models with differing supercharger gear ratios and accessory drives for bomber and transport installations, while experimental versions tested contra-rotating propeller gearboxes and upgraded ignition and fuel systems. Specialized adaptations were created for cold-weather operation in concert with Arctic research programs sponsored by Glavsevmorput and for naval applications evaluated by representatives of Soviet Navy aviation branches.
The ASh-73 was installed in several significant Soviet aircraft, notably on postwar heavy bombers and transports. Primary applications included the Tupolev Tu-4 derivatives and the Ilyushin Il-12 series, and it powered prototypes and limited-production types evaluated by design bureaus such as Myasishchev and Sukhoi in transition projects. The engine was also trialed on testbeds associated with TsAGI aerodynamic programs and employed in conversions conducted at state repair plants for Aeroflot fleets operating in remote regions.
Production occurred at major engine plants across the Soviet Union under supervision of ministries and institutes influenced by planners in Gosplan and Sovnarkom successors. Total production numbers were modest compared with wartime mass-produced designs, as strategic emphasis shifted toward gas turbine technology championed by engineers at Nikolay Kuznetsov's bureau and factories retooled for Klimov and Soloviev turboprops. The ASh-73 nonetheless represents a key evolutionary step in Soviet piston engine technology, bridging wartime radial practice and the postwar move to turbomachinery; its design lessons informed later work at institutes like TsIAM and had operational impact across Soviet civil and military aviation sectors.
Category:Aircraft piston engines