Westland CL.20
| Industry | Aerospace |
|---|---|
| Founded | 1934 |
| Headquarters | Yeovil , United Kingdom |
The Westland CL.20, also known as the Cierva-Lepère C.31, was a two-seat autogyro developed and constructed by Westland Aircraft during the period from 1934 to 1938. A single prototype was completed and flown, alongside six additional airframes which remained unfinished. The aircraft suffered from control difficulties and inadequate lift capabilities. As these issues remained unresolved, the project was ultimately discontinued, with the prototype being dismantled in 1938.
Development
Prior to the unsuccessful outcome of the Westland C.29, "Teddy" Petter aimed to create a new cabin autogyro in partnership with French autogyro designer George Lepère of the Lioré et Olivier firm. The original concept originated from Georges Lepère in collaboration with the Cierva Autogiro Company, drawing upon the design of the Cierva C.27#Cierva-Lepère C.L.10B. The detailed engineering was undertaken by Westland’s Arthur Davenport alongside Petter.
By December 1934, construction was completed, and in January 1935, taxi trials were conducted at Yeovil with test pilot Harald Penrose. Subsequently, the prototype was moved to Cierva’s flight testing facility at Hanworth Aerodrome, where Juan de la Cierva piloted its maiden flight on 5 February 1935. During further development flights performed by Reginald Brie, the CL.20 displayed overly sensitive lateral controls and failed to climb above approximately 300 feet (91 m). An attempt to enhance lift involved fitting a more powerful Niagra engine; however, this modification yielded minimal improvement.
Despite its underwhelming performance, Teddy Petter convinced Westland to proceed with manufacturing six additional airframes. Nonetheless, ongoing development ceased as focus shifted towards emerging wartime demands. By the conclusion of its testing phase, the prototype had accumulated a total of 8 hours and 31 minutes of flight time across 61 sorties before being scrapped in 1938.
Design
Derived from the CL.10B, the fuselage framework of the CL.20 was constructed using three welded seamless steel tubes arranged in a flat-bottomed triangular cross section, supporting light alloy formers. Attached to these were light alloy stringers, which were then covered with fabric to create a faceted exterior surface. The cabin featured a light-alloy arched former at the rear combined with a wooden floor. Large doors and additional windows extended down to the lower longeron on each side, providing both easy entry and enhanced downward visibility.
The rotor, equipped with three blades, was designed to fold for easier storage and transportation. The aircraft incorporated three fins: two serving as endplates on the tailplane, and one half of the tailplane itself was given negative camber and incidence to counteract rotor effects.
Initially, the CL.20 was powered by a 70 hp Pobjoy radial engine driving a two-bladed tractor propeller, which had been modified to include a power take-off shaft for rotor spin-up during takeoff. Flight testing later saw the installation of a more powerful Pobjoy Niagara III engine in an effort to boost performance.