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Wright R-540

R-540 Whirlwind
Wright R540 in Curtiss Travel Air 16E.jpg
Wright R-540 Whirlwind installed in a Travel Air 16E at the Historic Aircraft Restoration Museum
Type Air-cooled 5-cylinder radial piston engine
National origin United States
Manufacturer Wright Aeronautical Corporation
Major applications Various light aircraft
Produced 1929-1937
Number built around 500

The Wright R-540 Whirlwind was a series of five-cylinder air-cooled radial aircraft engines built by the Wright Aeronautical division of Curtiss-Wright. These engines had a displacement of 540 in³ (8.85 L) and power ratings of around 165-175 hp (123-130 kW). They were the smallest members of the Wright Whirlwind engine family.

The Wright R-540 should not be confused with the Kinner R-540, a generally similar engine made by Kinner Airplane & Motor Corporation.

Wright introduced the J-6 Whirlwind family in 1928 to replace the nine-cylinder R-790 series. The J-6 family included varieties with five, seven, and nine cylinders. The five-cylinder version was originally known as the J-6 Whirlwind Five, or J-6-5 for short. The U.S. government designated it as the R-540; Wright later adopted this and dropped the J-6 nomenclature.

Like all the members of the J-6 Whirlwind family, the R-540 had larger cylinders than the R-790. The piston stroke of 5.5 in (14.0 cm) was unchanged, but the cylinder bore was expanded to 5.0 in (12.7 cm) from the R-790's bore of 4.5 in (11.4 cm). While the R-790 was naturally aspirated, the R-540, like the other J-6 engines, had a gear-driven supercharger to boost its power output.

Wright gradually refined the R-540, using suffix letters to indicate successive versions. For example, the R-540A had 165 hp (123 kW), while the R-540E of 1931 had power boosted to 175 hp (130 kW) thanks to an improved cylinder head design. Wright sometimes named these versions according to their power, e.g. "Whirlwind 165" or "Whirlwind 175".

The engine was built in Spain as the Hispano-Suiza 5Q or Hispano-Wright 5Q without modification apart from the use of Hispano's patented nitriding finishing process.


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