Keystone XOK


Role Observation floatplane
Manufacturer Keystone Aircraft
First flight January 1931
Primary user United States Navy
Number built 1
Type Prototype
Serial A8357

The Keystone XOK was an American biplane observation floatplane developed for the United States Navy during the early 1930s.

Design and development

In 1929, the Navy issued requirements calling for an observation floatplane intended for service aboard Omaha class light cruisers, readily convertible to wheels or floats and light enough to operate from the cruiser-type catapult.[1]

Prototypes were ordered from Keystone-Loening (then a subsidiary of Curtiss-Wright), Berliner-Joyce and Vought, and designated as the XOK-1, XOJ-1 and XO4U-1 respectively. The Keystone design was a conventional biplane of mixed metal and fabric construction, with the pilot and observer seated in tandem in open cockpits. It made its first flight on January 5, 1931.[1]

On April 15, 1931, during a demonstration before naval officials, the XOK-1 broke up in flight after the cowling detached itself and smashed into the wings and tailplane.[1] With the Berliner-Joyce and Vought prototypes nearly ready for trials, the Bureau of Aeronautics elected to discontinue further development of the XOK-1. Eventually, the Berliner-Joyce's entry was selected for production.


 United States

Specifications (XOK-1)

Data from [1]

General characteristics

  • Crew: 2 (pilot and observer)
  • Length: 29 ft 10 in (9.09 m)
  • Wingspan: 34 ft 8 in (10.57 m)
  • Wing area: 293 sq ft (27.2 m2)
  • Empty weight: 2,219 lb (1,007 kg)
  • Gross weight: 3,395 lb (1,540 kg)
  • Powerplant: 1 × Wright R-975 radial engine, 400 hp (300 kW)


  • Maximum speed: 139 mph (224 km/h, 121 kn) at sea level
  • Range: 330 mi (530 km, 290 nmi) estimated
  • Service ceiling: 19,900 ft (6,100 m)


  • Guns: 1× fixed, forward firing .30 in machine gun; 1× flexibly mounted .30 in machine gun in the rear cockpit

See also

Aircraft of comparable role, configuration, and era

Related lists


  1. ^ a b c d Johnson, E.R. (2011). United States Naval Aviation 1919-1941. Aircraft, Airships and Ships Between the Wars. Jefferson, North Carolina, and London: McFarland & Company, Inc. pp. 118. ISBN 978-0-7864-4550-9.

External links

  • Keystone XOK-1 photograph.