Shvetsov ASh-73

It was primarily used as the powerplant for the Tupolev Tu-4 heavy bomber, an unlicensed, reverse engineered copy of the American Boeing B-29 Superfortress.

The ASh-73 was not a reverse-engineered copy of the Wright R-3350 Duplex-Cyclone, 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).

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.

"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.

It was tested in late 1938 and was a failure because of cracks in the master connecting rod and the geared centrifugal supercharger's impeller.

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.