Curtiss YP-20 was a United States Army Air Service biplane fighter project. In 1929, three Curtiss P-11 Hawks were ordered with 600 hp (447 kW) Curtiss H-1640 Chieftain engines. These proved a failure, and before completion, the third was converted to use a 9 cylinder 575 hp (429 kW) Wright Cyclone, being completed as the YP-20. Testing with the R1820 was prolonged, so the Army's intention to promptly switch to a Curtiss V-1570 Conqueror engine and redesignate the aircraft XP-22 was dropped; another P-11 was chosen for that instead.