Cierva C.26
{{Short description|Unbuilt 1931 design for an "autogyro-helicopter" }}
{{Use dmy dates |date=May 2025 }}
{{Use British English|date=May 2025 }}
{{this |an unbuilt 1931 design for an unconventional autogyro and helicopter hybrid| the more conventional Cierva autogiro that possibly shared this designation |Cierva C.24 }}
| {{Infobox aircraft begin
|name=C.26 |image= |caption= }}{{Infobox aircraft type |type=Experimental autogyro |national origin=UK |manufacturer= |designer=Juan de la Cierva |first flight= |introduced= |retired= |status=Unbuilt design |primary user= |number built= |developed from= |variants with their own articles= |developed into= }} |
The Cierva C.26 was a 1931 design for an unorthodox autogyro by Juan de la Cierva that was never built.Brooks 1988, p.163–64"Bennett 1961, p.658 Cierva described it as an "autogiro-helicopter",Brooks 1988, p.163{{refn|group=lower-alpha|Cierva used the unconventional spelling "autogiro" for his creationsLeishman 2002, p.12}} a term he had coined the previous year to describe an aircraft with the characteristics and advantages of both more familiar types.Cierva 1930, p.911
The designation C.26 was possibly later applied to an unrelated Cierva design, a modified Cierva C.24,The Illustrated Encyclopedia of Aircraft 1983, p.1154 although aviation historian Peter W. Brooks considers this "unlikely".Brooks 1988, p.160
Design
The aircraft was to have fixed wings, with a Pobjoy R radial engine mounted on each. One of these engines was to be modified to reverse the direction of its drive shaft, so that the aircraft's propellers would contra-rotate. The starboard engine would also have driven the aircraft's rotor, with the rotor torque compensated by differential thrurst from the two propellers, together with a small rudder in the propeller slipstream. The rotor would also be equipped with a {{convert |12 |hp |kW |adj=on }} mechanical starter to pre-rotate it to 80–85% of its flight speed.
An unusual flight characteristic of the C.26 design was its way of climbing vertically and hovering. These flight modes, typical of helicopters, are ones that autogyros are not capable of with their unpowered rotors.Venkatesan 2014, p.12 The C.26, however, was designed to be able to fly like this with its fuselage oriented vertically, that is, with its nose pointing straight upwards and tail pointing straight down.Brooks 1988, p.164 Thrust for vertical climb and for hover would therefore be provided by the wing-mounted propellers. Cierva acknowledged that this would be an uncomfortable attitude for the pilot (and add complexity to the fuel system), but said that it would only be adopted for very short times. For example, vertical take-off could be used during take-off in the vicinity of high obstacles, and that more conventional climb attitudes could otherwise be used.
Specifications (as designed)
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|ref=Brooks 1988, p.163–64
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Notes
{{reflist|group=lower-alpha}}
=References=
{{reflist}}
=Bibliography=
- {{cite magazine |last=Bennett |first=J. A. J. |title=The Era of the Autogiro |magazine=Journal of the Royal Aeronautical Society |volume=65 |number=610 |pages=649–660 |date=October 1961 }}
- {{cite book |last=Brooks |first=Peter W. |title=Cierva Autogiros: The Development of Rotary-Wing Flight |publisher=Smithsonian Institute |location=Washington D.C. |year=1988 }}
- {{cite magazine |last=Cierva |first=Juan de la |title=The Autogiro |magazine=Journal of the Royal Aeronautical Society |volume=34 |number=239 |pages=902–921 |date=November 1930 }}
- {{cite book |title=The Illustrated Encyclopedia of Aircraft |publisher=Aerospace Publishing|location=London }}
- {{cite book |last=Leishman |first=J. Gordon |title=Principles of Helicopter Aerodynamics |year=2002 |publisher=Cambridge University Press |location=Cambridge }}
- {{cite book |last=Venkatesan |first=C. |title=Fundamentals of Helicopter Dynamics |year=2014 |publisher=CRC |location=Boca Raton FL }}
{{Cierva aircraft}}
Category:1930s British experimental aircraft