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Kellett KD-1
Kellett XR-3 modification of YG-1B (KD-1) of U.S. Army preserved at Yanks Air Museum, Chino airfield California, in January 2008
Role Autogyro
National origin United States
Manufacturer Kellett Autogiro Company
First flight 1934
Primary users United States Army Air Forces
Eastern Airlines

The Kellett KD-1 was a 1930s American autogyro built by the Kellett Autogiro Company. It had the distinction of being the first practical rotary-wing aircraft used by the United States Army and inaugurated the first scheduled air-mail service using a rotary-wing aircraft.


Using the experience gained in building Cierva autogyros under licence the Kellett Autogiro Company developed the KD-1 which was similar to the contemporary Cierva C.30. It had two open cockpits, a fixed tailwheel landing gear and was powered by a 225 hp (168 kW) Jacobs L-4 radial engine. After testing of the prototype a commercial variant designated the KD-1A was put into production. The KD-1A had a three-bladed rotor with folding blades and a number of minor detail improvements. A KD-1B which was a KD-1A with an enclosed cockpit for the pilot was operated by Eastern Airlines and inaugurated the first scheduled rotary-wing air-mail service on 6 July 1939. In 1935 the United States Army bought a KD-1 for evaluation and designated it the YG-1, a second aircraft followed which had additional radio equipment and was designated the YG-1A. These two aircraft were followed by a batch of seven designated YG-1B. In 1942 seven more were bought for use in the observation role as the XO-60. Six XO-60s were re-engined with 300 hp (224 kW) Jacobs R-915-3s and re-designated YO-60.[1] One YG-1B was modified with a constant-speed rotor and was re-designated the YG-1C, it was later re-engined with the more powerful R-915 and re-designated again as the XR-2. The XR-2 was destroyed by rotor ground resonance problems and the evaluation was continued with another modified YG-1B designated the XR-3.


YG-1 (KD-1) at Langley

Prototype, one built
Commercial variant with open cockpit and a 225 hp (168 kW) Jacobs L-4 radial engine; three built.
Commercial variant with enclosed cockpit; two built.
United States Army designation for one KD-1A acquired for evaluation.
One aircraft as YG-1 with the addition of radio equipment.

YG-1B at Langley

Production aircraft for the United States Army; seven built.
One YG-1B modified with a constant-speed rotor for evaluation, later designated the XR-2.

A Kellett XO-60

Production aircraft for the United States Army with a 225 hp (168 kW) Jacobs R-755 radial engine, seven built.
Six XO-60s re-engined with a 300 hp (220 kW) Jacob R-915-3 radial engine.
The YG-1C re-designated after being re-engined with a 300 hp (220 kW) Jacobs R-915-3 radial engine.
One YG-1B modified to XR-2 standard for evaluation.
Kayaba Ka-Go prototype
Prototype; it was an airframe which had repaired KD-1A by Kayaba.
Kayaba Ka-1
Imperial Japanese Army developed referring to KD-1A. Powered by a 240 hp (180 kW) Argus As 10 engine, airframe that changed engine of prototype.
Kayaba Ka-2
Imperial Japanese Army developed, referring to KD-1A. Powered by a 245 hp (183 kW) Jacobs L-4MA-7 engine, airframe that changed engine of Ka-1 for the same thing as prototype.


United States

Specifications (KD-1B)

General characteristics

  • Crew: 2
  • Length: 28 ft 10 in (8.79 m)


See also


  1. "ARMY AUTOGIRO" Popular Science, June 1944, photo of YO-60
  • Taylor, Michael J. H. (1989). Jane's Encyclopedia of Aviation. London: Studio Editions. 
  • The Illustrated Encyclopedia of Aircraft (Part Work 1982-1985). Orbis Publishing. 
  • Andrade, John (1979). U.S.Military Aircraft Designations and Serials since 1909. Midland Counties Publications. ISBN 0-904597-22-9. 

External links

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