The XOS2U-1 was first in a series of Vought aircraft to become known affectionately around the world as the “Kingfisher, Saver of Men.”

In March 1937, Vought contracted with the Navy to build a new observation/scout prototype, the XOS2U-1.  Engineers, led by Rex Beisel, set out to meet new and stiff requirements to produce a monoplane that would do the job better than the traditional biplane ever did. As recalled by Frank Allbright, project engineer on the OS2U-1, “…when the proposal for the XOS2U-1 was first submitted to the Navy, it was nearly turned down because the Navy engineers did not believe that a monoplane could be designed to meet the weight and performance requirements.  Vought was requested to take the proposal back home and spend two weeks checking and re-checking the weight, and especially the landing speed, to see if some mistake had not been  made.”

One XOS2U-1 was built. Using advanced design and structural features allowed the XOS2U-1 to attain the low landing speed and light weight that traditionally were believed to belong to the biplane. Some of these features included high-lift devices, “deflector plate” flaps used on the trailing edge of the wing, and “drooping” ailerons which served the same function as flaps at low speed.

Another innovative feature was spoilers, worked out by W.C. Schoolfield and test pilot Paul Baker on a Fairchild F-24. This feature supplanted the ailerons at low speeds and provided lateral control. The structure incorporated spot-welded aluminum alloy construction rather than the usual rivet-studded surfaces. This was the first design to use spot-welding, creating a non-buckling, smooth surface which was conducive to higher speeds. The aircraft was convertible to a seaplane by addition of float gear.

The XOS2U-1 made its first flight in May 1938.  The low-powered monoplane with its Pratt & Whitney R-985-4 engine outperformed the biplanes in speed, range, and general performance.

Following successful flight testing of the XOS2U-1, Vought was awarded a contract in April 1939 for 54 OS2U-1’s. These differed from the XOS2U-1 in small changes to the float attachments and by having an R-985-48 engine in place of the 4. They were delivered in 1940.