Westland CL.20
{{Use dmy dates|date=February 2017}}
{{Use British English|date=February 2017}}
| {{Infobox aircraft begin
| name = CL.20 | image = | caption = | alt = }} {{Infobox aircraft type |type = Two seat cabin autogyro |national origin = United Kingdom |manufacturer = Westland |designer = |first flight = 5 February 1935 |introduced = |retired = |produced = |number built = 1 completed, 6 airframes not completed |program cost = |unit cost = |developed from = Cierva-Lepère CL.10B |variants with their own articles = }} |
The Westland CL.20 (aka Cierva-Lepère C.31{{Cite web|url=https://www.secretprojects.co.uk/threads/cierva-designations.13436/|title = Cierva designations| date=23 August 2011 }}) was a two-seat autogyro designed and built by Westland Aircraft between 1934 and 1938. One flying prototype and six airframes were built, which had control problems and insufficient lift. Before these problems could be solved the programme was abandoned and the prototype was scrapped in 1938.
Development
Before the Westland C.29 had proven to be a failure, "Teddy" Petter sought to design another cabin autogyro in collaboration with George Lepère, a French autogyro designer with the Lioré et Olivier aircraft company. The initial design was by Georges Lepère in association with the Cierva Autogiro Company and was based on the Cierva-Lepère C.L. 10B. Detailed design was by Westland's Arthur Davenport and Petter.
Construction was completed in December 1934 and in January 1935 taxi-ing trials were carried out at Yeovil by Harald Penrose, after which it was transported to the Cierva flight test centre at Hanworth Aerodrome, where Juan de la Cierva flew the prototype on its first flight on 5 February 1935. During development flying, carried out by R.A.C. Brie, the CL.20 exhibited over-sensitive lateral control and was unable to exceed a height of {{convert|300|ft|m|abbr=on}}. To improve lift, a more powerful Niagra engine was fitted but this made little difference.
Despite the poor performance of the prototype, Teddy Petter persuaded Westland to manufacture another six airframes, but further development was abandoned due to emerging work as a result of the threat of war. At the end of development flying the prototype had logged 8 hours 31 minutes flying time over 61 flights, before the flying prototype was scrapped in 1938.
Design
Based on the CL.10B, the load bearing structure of the CL.20s fuselage was based on three welded seamless steel tubes (forming a flat bottomed triangle in cross section) carrying light alloy formers. On this, light alloy stringers were fixed and covered in fabric, producing a multi-faceted surface. The cabin structure consisted of a light-alloy arched former at the back with a wooden floor. On each side a large door and additional windows reached down to the bottom longeron, giving both excellent access and downward vision.
The three-bladed rotor could be folded for storage and transport. Three fins were fitted, two as endplates to the tail-plane, one half of which was fitted with negative camber and incidence, in order to help offset the effects of the rotor.Lukins, A,; "The Book of Westland Aircraft", Aircraft (Technical) Publications, 1942.
The CL.20 was initially powered by a {{convert|70|hp|kW|abbr=on}} Pobjoy radial engine, driving a two-bladed tractor propeller, modified to include a power take-off shaft to spin up the rotors for take off.{{cite book|last1=James|first1=Derek, N|title=Westland Aircraft since 1915|date=1991|publisher=Putnam|isbn=0-85177-847-X|pages=253–256}} During flight testing, in an attempt to improve performance, a more powerful Pobjoy Niagara III was fitted.
Specifications
{{Aircraft specs
|ref=James and Augusta Westland{{cite web|title=Aircraft Data Sheet: Cierva CL-20 (1935)|url=http://history.whl.co.uk/cierva_cl_20.html|website=Westland History|accessdate=31 August 2014}}
|prime units?=imp
|crew=1
|capacity=1 passenger
|length ft=31
|length in=9
|height ft=10
|height in=3
|empty weight lb=840
|gross weight lb=1400
|more general=
|eng1 number=1
|eng1 name=Pobjoy S Niagara III
|eng1 type=7-cylinder air-cooled radial piston engine
|eng1 hp=95
|eng1 note=
|prop blade number=2
|prop name=fixed pitch wooden propeller
|prop dia ft=7
|prop dia in=3
|rot number=1
|rot dia ft=32
|rot dia in=0
|max speed mph=106
|max speed note=
- Landing speed: {{convert|25|mph|km/h kn|abbr=on}}
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