fitted with Conqueror engine for the 1927 National Air Races. XO-13A Second XO-13, fitted with wing skin radiators. O-13B One O-1C fitted with a Conqueror engine, tested as an observation aircraft, and provided to Secretary of War. YO-13C Three O-1Es re-engined with direct-drive Conqueror engines. YO-13D One O-11 fitted with supercharged Conqueror engine. XO-16 One O-11 with Prestone cooling system. XO-18 One O-1B testbed for Curtiss H-1640 Chieftain engine. Y1O-26 One O-1E fitted with a geared Conqueror engine. O-39 O-1G refitted with a Conqueror engine and cockpit canopy; ten built. U.S. Navy and Marine Corps A-3 Helldiver Registry name of XF8C-8, not adopted by USN. A-4 Helldiver Civil version of XF8C-8 for use by Assistant Secretary of Navy David Ingalls. Later redesignated XF8C-7. XF8C-1 Model 37C variant developed from XO-12; two built for the U.S. Navy. F8C-1 Falcon Model 37C powered by the Pratt & Whitney R-1340 Wasp radial piston engine; four built in 1928 for the U.S. Marine Corps as light bombers, fighters and observation aircraft, later redesignated OC-1. XF8C-2 Model 49, one prototype for F8C Helldiver. Original crashed on first factory flight and was replaced by Curtiss with a second bearing identical sn. F8C-3 Falcon Second production batch of Navy Falcons; 21 built for USN/USMC in 1928, later redesignated OC-2. XF8C-4 Second Helldiver prototype, modified tail skid assembly. F8C-4 Helldiver Model 49B, production dive-bomber variant for the USN/USMC; 25 built, later designated O2C. F8C-5 Helldiver Model 49B with ring cowling; 63 built in 1930–31, later designated O2C-1. XF8C-6 Two F8C-5s modified with superchargers, slats, and wing flaps; one later modified as O2C-2. XF8C-7 Redesignation of A-4 Helldiver, later redesignated XO2C-2. XF8C-8 Two prototypes built with canopy-enclosed front cockpit, later redesignated O2C-2. O2C-1 Helldiver Redesignation of 63 F8C-5; 30 production O2C-1s in 1931. O2C-2 Helldiver Redesignation of XF8C-8s and one XF8C-6. XOC-3 One XF8C-1 prototype fitted with a Chieftain engine. XF10C-1O2C-2 re-engined with a R-1510 engine, also temporary designated XS3C-1. Civil and export Civil Falcon 20 civil versions: Conqueror Mail plane; D-12 Mailplane; Lindbergh Special, sold to Charles Lindbergh; Liberty Mailplane, 14 single-seat mailplanes, powered by a Liberty piston engines, sold to National Air Transport. Export Falcon also South American D-12 Falcon. One seaplane version of the O-1B was sold to Colombia, followed by an order for 15 more. Another 10 Model 35Fs were sold to Peru. Colombia Cyclone Falcon Model 37F fitted with the Wright Cyclone radial piston