The Curtiss R-600 Challenger was a six-cylinder, double-row, air-cooled, radial engine for aircraft use built in the United States in the late 1920s.

Curtiss started work on a small six-cylinder engine in May 1927.

[1] The engine was unusual in its design with aluminium cylinders mounted at 60°, so that it was in effect two staggered three cylinder engines.

[2] The engine was first run in December 1927, and was taken to market producing between 170 and 180 horsepower (127 and 134 kW) at 1,800 rpm.

[1] Data from Nutt, 1928 p.842[3] Comparable engines Related lists Media related to Curtiss R-600 at Wikimedia Commons