STATUS: Retired, Out-of-Service
MANUFACTURER(S): Kellett Autogiro Company - USA
OPERATORS: Imperial Japan; United States
LENGTH: 28.84 feet (8.79 meters)
WIDTH: 40.03 feet (12.2 meters)
HEIGHT: 10.30 feet (3.14 meters)
WEIGHT (EMPTY): 1,581 pounds (717 kilograms)
WEIGHT (MTOW): 2,249 pounds (1,020 kilograms)
ENGINE: 1 x Jacobs L-4 radial engine developing 225 horsepower driving a two-bladed nose-mounted propeller unit; Autorotation managed the three-bladed, mast-mounted main rotor.
SPEED (MAX): 128 miles-per-hour (206 kilometers-per-hour; 111 knots)
RANGE: 200 miles (322 kilometers; 174 nautical miles)
CEILING: 12,500 feet (3,810 meters; 2.37 miles)
Detailing the development and operational history of the Kellett KD-1 Two-Seat Observation Autogiro Aircraft.
Entry last updated on 11/18/2017.
Authored by Staff Writer. Content ©www.MilitaryFactory.com.
The Kellett Autogiro Company was founded during the "Golden Age of Flight" in 1929. Its early work involved licensed production of Cierva autogyro aircraft. Despite their appearance, autogyros were not true helicopters as their main rotor masts were not driven under normal power. Instead an "autorotation" effect was used to develop vertical lift while an engine-driven propeller provided the needed forward pull / push. The concept was developed by Spaniard Juan de la Cierva and an example first-flown in January of 1923.
Kellett produced several of the early-form Cierva products before shifting attention to a more internally-oriented design. This work produced the Kellett "KD-1" which held attributes akin to the Cierva C.30 model autogyro. The aircraft carried a traditionally-arranged airframe which sat the engine at the nose and two open-air cockpits directly aft of this. The engine (Jacobs L-4 radial unit of 225 horsepower) drove a two-bladed propeller. The tail unit incorporated the necessary horizontal and vertical planes while the undercarriage was fixed in flight and wheeled for ground-running actions. The notable physical characteristic of the aircraft was its three-bladed, mast-mounted main rotor which was installed over and ahead of the crew positions and over the engine compartment.
The prototype emerged as the KD-1 and only a single example was built. Upon completing the needed testing and certification, the KD-1 was brought to the commercial sector as the "KD-1A". Three were built to this standard. The "KD-1B" was similar in form and function but offered enclosed cockpits. Two of this mark were built.
United States Army interest in the design was enough to warrant formal evaluation of the product. This led to the developmental designation of "YG-1" being issued and covered a single KD-1A example. The follow-up "YG-1A" was given a radio suite and the first U.S. Army production model became "YG-1B" and seven were acquired. One was modified with a constant-speed propeller for testing purposes and became the "YG-1C" (later the XR-2).
An additional seven examples followed in the "XO-60" guise which carried the Jacobs R-755 radial piston engine of 225 horsepower. The "YO-60" differed in its use of a Jacobs R0915-3 radial engine of 300 horsepower. Six were produced to this standard.
The "XR-2" was the YG-1C redesignated but also carried the R-915-3 engine of 300hp. The "XR-3" was a one-off YG-1B model modified to the XR-2 standard but only ever reached the evaluation stage and was never furthered.
In practical service, the KD-1 proved a successful autogyro attempt. It was responsible for the first-ever scheduled delivery of mail by air by a rotary-wing aircraft when it completed such a flight on July 6th, 1939. For the U.S. Army, it also served as the service's first viable rotary-wing platform before more advanced types were eventually acquired. A few variants also emerged from Kabaya in Japan: "Ka-Go" was a prototype based on the KD-1A and Ka-1 was given an Argus As 10 engine of 240 horsepower. Ka-2 carried a Jacobs L-4MA-7 engine of 245 horsepower.
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This entry's maximum listed speed (128mph).
Graph average of 112.5 miles-per-hour.
Graph showcases the Kellett KD-1B's operational range (on internal fuel) when compared to distances between major cities.
Useful in showcasing the era cross-over of particular aircraft/aerospace designs.
Comm. Market HI*: 44,000 units
Military Market HI**: 36,183 units