The Curtiss O-11 Falcon was a version of the O-1 observation aircraft that was produced for the National Guard, and used surplus Liberty engines. The Curtiss D-12 engine used on the O-1 was also used in their Hawk fighters, and so was in somewhat limited supply.
In order to produce a suitable observation aircraft for the National Guard the Army decided to install surplus Liberty engines in the O-1 Falcon airframe. The first XO-11 prototype was produced by fitting a Liberty engine in the fourth production O-1. At the same time the aircraft was given the fuselage lines of the O-1A.
The XO-11 was a success and so the type was ordered into production. A total of sixty-six O-11s were ordered in three batches (serial numbers 27-1 to 35; 27-98 to 107 and 28-196 to 217). Although they were produced for the National Guard, they were also used by the 103rd Observation Squadron and by the 42nd School Squadron at Kelly Field, Texas.
One of the O-11s was given dual controls and a modified tail and became the O-11A.
Several were used for experimental work or as prototypes. One became the XO-12 with a Pratt & Whitney Wasp engine. Another became an O-13C, then an O-13C before finishing up as a O-1B. Another became the XO-16.
Engine: Liberty 12A
Length: 27ft 3.5in
Height: 10ft 3in
Empty weight: 3,012lb
Gross weight: 4,532lb
Max speed: 146.9mph
Climb Rate: 1,066ft/ min
Service ceiling: 16,630ft
Range: 437 miles
Armament: One fixed and one flexibly mounted machine gun