CIERVA  C.7 / C.8

 El C.7 fue el número asignado a dos autogiros del tipo Cierva construidos en España por Jorge Loring, volando en Cuatro Vientos en el año 1926; estaban equipados con un motor Hispano-Suiza de 300 HP.

Avro construyó el tipo C.8, que sería hasta ese momento la serie mas importante. La designación C.8R (AVRO TIPO 587) se le dio al tipo C.6D, modificado con palas de rotor tipo remo, alas embrionarias y con un motor Clerget de 130 hp volando indistintamente con un rotor bipala o tripala. Un fuselaje biplaza Avro tipo 552 con motor Wolseley Viper de 180 hp recibió un rotor similar al C.8R pero se le adoso una aleta dorsal; el aparato denominado C.8V (AVRO TIPO 586), voló en 1926. Luego nació el C.8L (AVRO TIPO 611), basado en un fuselaje del TIPO 504N con motor Armstrong Siddeley Lynx de 180 hp. Un C.8L MK IV (designado C.8W) fue construido y vendido al constructor aeronáutico Harold Pitcairn, con un motor Wright Whirlwind de 225 hp; Pitcairn compró los derechos para EEUU y fundó en Pensylvania la Pitcairn-Cierva Autogiro Co.

 Cierva's first successful Autogiro (and the first successful rotary-wing aircraft of any kind), the C.4, took flight on January 17, 1923 at Getafe airfield in Madrid, Spain. Over the next three years, Cierva made progressive improvements that resulted in the standard monoplane configuration for gyroplanes that remained in use until the mid-1930s. The greatest improvements came in the design of the rotor blades and the hinges, both of which would later prove essential for helicopters. Cierva constructed his first C.8 model, the C.8V, in close association with A.V. Roe & Co. Ltd. (commonly known as Avro). The airframe was based on the fuselage of the Avro 552A, a variant of the venerable Avro 504 biplane. The most innovative component of the C.8V was its new four-bladed cable-braced rotor that incorporated drag hinges to reduce the stresses on the blades. The "V" in the model designation indicated the type of engine used in the variant - in this case, a Wolseley Viper. Cierva constructed six different C.8 configurations, all of which were experimental testbeds built to test improvements in autogiro technology before a production model, the C.19, was to appear in 1929. Given the limited knowledge of rotary wing aerodynamics of the time and the necessity of relying on trial-and-error methods, it is not surprising that Cierva constructed two dozen experimental autogiros before he completed a model worthy of production.

The most powerful of the six C.8s constructed was the two-seat C.8W fitted with a 220 horsepower Wright Whirlwind J-5. Cierva had equipped the aircraft with an American engine at the request of its buyer, Harold Pitcairn. As a teenager, Pitcairn had developed a fascination with the possibilities of rotary-wing aircraft and had avidly followed news of Cierva's progress. In 1924, he had established himself in the aircraft manufacturing industry by building rugged biplanes, one of which, the PA-5 Mailwing (see NASM Collection), was to gain a legendary reputation amongst pilots who flew the nascent airmail routes. Nonetheless, Pitcairn pursued his dream to enter the then highly dubious field of rotary-wing aviation. In 1925 and 1926 he traveled to England for discussions with Cierva about either license-building Autogiros or using them as the basis of his own helicopter designs. While there with his engineer, Agnew Larsen, Pitcairn viewed film footage of the aircraft in operation. They observed that, while the Autogiro was capable of landing in short distances within a confined space, it also required considerable amounts of high-speed taxiing to build up sufficient rotor rpm to take off. Clearly, the ability to land short was of little value without the capability to take off from the same terrain. Nonetheless, Pitcairn remained interested, and in the summer of 1928 he returned to England and flew in the C.8, which greatly impressed him. A rope sling pulled by a ground crew spun up the rotor of the C.8 to near takeoff rpm, which meant that less taxiing was required before a takeoff of only (100 ft). Pitcairn decided to purchase one of the experimental Cierva C.8s as a testbed for his own company's rotary wing program.

European engines turned counter-clockwise when viewed from the rear, while the American Wright Whirlwind J-5 turned clockwise, which caused Pitcairn some apprehension over its affects on rotor rpm. After Cierva confirmed that this would not be an issue, Pitcairn agreed to purchase a new C.8 with the Wright engine. On December 11, 1928, the C.8W arrived in the United States onboard the S.S. Aquitania. Pitcairn planned to have the Autogiro make its flight on the twenty-fifth anniversary of the Wright brother's first powered flight, on December 17, at his Bryn Athyn, Pennsylvania airfield. However, he was conservative when dealing with the experimental testing of the newly reassembled aircraft and was extremely anxious that all should go well on the first flight. Thus, not until December 18, would the C.8W perform the first flight of a gyroplane in the United States, with Cierva test pilot, Arthur "Dizzy" Rawson at the controls. Pitcairn himself flew the aircraft the following day. Whatever doubts Pitcairn had concerning the potential of rotary-wing aircraft evaporated as he completely reorganized his company to support autogiro production. His first step was to acquire the American patent rights to Cierva's innovations and to manage and license them under the direction of the Pitcairn-Cierva Autogiro Company of America. This enterprise, later renamed the Autogiro Company of America, would remain separate from the production side of Pitcairn Aircraft, which would become the Pitcairn Autogiro Company, Inc. in 1933.

Technical data for C.7 

Characteristics
Características

Information
Información

Characteristics
Características

Information
Información

1 Hispano-Suiza

1

300 HP

Lb

Ft

Lb

Ft

Kt

 Ft

Kt

NM