Cierva C.6
| Cierva C.6 | |
|---|---|
 Replica of the Cierva C.6bis (C.6B) in the Cuatro Vientos Air Museum, Madrid |
|
| Type: | Gyroplane |
| Design country: | |
| Manufacturer: |
Spanish Air Force, |
| First flight: |
February 1924 |
| Number of pieces: |
4th |
The Cierva C.6 is a gyroplane by the designer Juan de la Cierva , two of which were built in Spain in the mid-1920s and two of which were manufactured by Avro in Great Britain.
C.6 and C.6bis
After the crash of the Cierva C.5 , Cierva realized that he was unable to cope with the financing of the further development of his car giro concept. In the meantime, however, the Spanish Air Force, especially in the person of Emilio Herrera Linares , who worked at the Laboratorio Aerodinámico de Cuatro Vientos and had previously supported Cierva, showed interest in this new type of aircraft. So the first two copies of the successor design C.6 could be built in the workshops of the Spanish Air Force in Cuatro Vientos . The C.6 received the fuselage of an Avro 504 K trainer aircraft including the 110 hp Le Rhône rotary engine. The four-blade rotor with flapping hinges had a constant depth and used a symmetrical Göttingen 429 profile. The appearance of the rotor with the blades hanging down was due to the fact that the blade spars were already bent in this shape before installation. As with the two previous machines, Cierva also used ailerons mounted on booms (tubular steel spars).
In February 1924 JL Ureta tested the machine with success. For reasons not known in detail, however, there is no further information about further flights until December 12, 1924. On that day, Joaquin Loriga made the first overland flight of a gyroplane from Cuatro Vientos to Getafe over a distance of 12 km. In January 1925, Vickers Ltd. in Cuatro Vientos a demonstration of the machine, which suffered an engine and rotor damage. Due to discrepancies between the wind tunnel results obtained in Spain and those won by Vickers in Weybridge, further negotiations were suspended.
As its successor, the C.6bis flew for the first time in May 1925 , which differed from the C.6, which had been used up until then, primarily in that it had a larger rotor diameter. The rotor blades now had hooks ( pegs ) on their underside at a distance of 0.61 m from the mast to wind up the starter rope. Until then, the rotor was turned by hand, with which it was brought to a sufficient autorotation speed before the start. The only additional change was to replace the standard horizontal stabilizer on the Avro 504 with one with enlarged and balanced rudders. The machine was on June 24, 1925 by Loriga in Cuatro Vientos to the Spanish King Alfonso XIII. demonstrated. Since many military attachés from other nations also attended the demonstration, interest in the Cierva Autogiros awoke again abroad.
When the Spanish authorities did not want to guarantee permanent support for the Autogiro development in Spain, Cierva tried to advertise financial participation in his invention in France and England. While France hesitated, Cierva was invited to England to demonstrate the C.6bis at the Royal Aircraft Establishment (RAE) in Farnborough. The first flight took place there on October 10, 1925 with Frank Courtney at the wheel instead of the sick Loriga. Until October 31, when the plane was damaged in a hard landing, flights lasting a total of four hours could be carried out in front of government officials, the military and the press. The C.6bis could be flown safely in a speed range between 107 and 46 km / h.
During this screening period, Cierva gave his first lecture to the Royal Aeronautical Society on October 22, 1925 . Then JG Weir and a few friends approached Cierva with the aim of using his patents and licenses to build his autogiros in Great Britain. This resulted in the establishment of the Cierva Autogiro Company on March 24, 1926, with offices in Bush House in London. The company limited itself to construction tasks and the issuing of licenses; later production took place at AV Roe in Hamble (Hampshire).
After the repair of the C.6bis, Courtney presented it to French authorities in Villacoublay in January and February 1926. After a long delay, this finally led to the license building in France, which was carried out by Lioré et Olivier. The whereabouts of the C.6bis is not known, but it was probably converted back into an Avro 504K.
The C.6 and C.6bis were subsequently referred to as C.6A and C.6B.
C.6C and C.6D
The extensive and successful testing of the C.6B by the RAE and most recently the demonstrations in France prompted the British Air Ministry to order two similar copies from Avro, as a licensee of the Cierva Autogiro Co. (Contract 680624/26). The C.6C (Avro 574) and C.6D (Avro 587) built in Hamble were largely similar to the C.6A and C.6B, but had Clerget engines with 130 hp instead of the Le Rhône engines. The system according to which Avro assigned its design numbers for the Cierva samples is difficult to understand. Sometimes new numbers were assigned with only minor changes to existing aircraft, with many gyroplane cells often being changed and rebuilt. The same cell could have two or three different design numbers.
The C.6C flew with RAF registration and Courtney at the controls in Hamble for the first time on June 19, 1926. When presented to King George V on the occasion of the Hendon RAF display on July 3, it then also bore the RAF serial number J8068 . Later, the ailerons attached to the booms were supplemented by stub wings to reduce the load on the rotor during forward flight. On February 7, 1927, the C.6C crashed, probably caused by the fatigue fracture of a leaf root, the cause of which was the lack of flexibility of the leaves in the plane of rotation.
The subsequent C.6D was the first two-seat gyroplane and flew for the first time on July 29, 1926 in Hamble. The next day, Juan de la Cierva himself was the first passenger to be carried in a gyroplane. On September 5, 1926, Ernst Udet also flew the plane that was being transported overland to Tempelhof. After returning, it was converted to the Cierva C.8R and received a three-bladed rotor with greater depth and vertical joints , which should eliminate the risk of fatigue fractures at the blade root. These new hinges allowed the rotor blade to have limited movement fore and aft as it rotated. The C.6D also received additional stub wings. Controls were only available at the back. This work was completed on October 15, 1926. Avro's chief test pilot Bert Hinkler flew the C.8R with a two-bladed rotor in September 1927. However, due to strong vibrations, the two-blade rotor was removed.
Samples C.8V and C.8L, which are described under Cierva C.8, were not related to the Cierva C.6 .
literature
- PT Capon: Cierva's first autogiros Part 2 . In: Airplane Monthly May 1979, pp. 234-240
- Planes from A – Z - Cierva Autogyros . In: AERO - The illustrated collective work of aviation, No. 51, pp. 1424 ff., 1984, Marshall Cavendish.
- AJ Jackson: Avro Aircraft since 1908 , Putnam, 1965, 2nd edition 1990, ISBN 0-85177-834-8 , pp. 233-240
- TR Hiett: Cierva's rotating wings . In: AIR Enthusiast July / August 2003, pp. 26–31
Web links
Individual evidence
- ↑ Hiett, 2003, p. 29