Cierva C.4

Cierva C.4
Type:	experimental gyroplane
Design country:	Spain
Manufacturer:
First flight:	January 17, 1923
Number of pieces:	one each C.4 and C.5

The Cierva C.4 (originally Autogiro No.4 ) was an experimental gyroplane from the designer Juan de la Cierva , with which the first successful flights of a gyroplane were carried out in 1920. The subsequently built C.5 differed only slightly from the C.4.

history

Autogiro No.4 (Cierva C.4)

As a consequence of the failures with the first three test gyroscopes C.1, C.2 and C.3, Cierva no longer fixed the rotor blades rigidly to a mast. Instead, he used a horizontally arranged flapping hinge that allowed the leaves to move up and down. If the blade rotates forwards, as seen in the direction of flight, the increased lift can cause the blade to rise, reducing its effective wingspan and angle of attack. The returning sheet should return to its normal horizontal position by centrifugal forces. The deflection angle was limited by rubber buffers and cable tension. The control to the sides should be achieved by a right and left tiltable rotor head. The control around the longitudinal and transverse axes as well as the directional stability should be guaranteed by a normal horizontal tail unit and rudder.

For the construction of the C.5, Cierva used the shortened hull of a summer monoplane with an 80 HP Le Rhône rotary engine. Possibly this came from the unsuccessful C.3. However, the first attempts at flight remained unsuccessful and after a flapping joint fractured, a crash could only just be avoided. Only after blocking the ability to tilt the rotor head did the machine show the first tendencies to lift, but at the same time the roll tests continued to show the lateral overturning tendency already observed in all previous test machines. The final solution consisted of a slight relocation of the still non-tilting rotor head together with the use of ailerons, which were attached to the outriggers on both sides of the fuselage.

With the modified C.4 Gomez Spencer made the first flight of a gyroplane on the Getafe airfield on January 17, 1923. After the machine was transferred to Cuatro Vientos , Spencer flew there for the first time in a closed circle on January 31, 1923, and achieved a flight time of four minutes.

Cierva C.5

For the C.5, Cierva used the fuselage of the earlier C.2, equipped with a 110-hp Le Rhône engine and a three-blade rotor with a Göttingen 430 profile. Like the C.4, the machine also received flapping joints and ailerons on arms for side steering. Although the C.5 was initially successfully tested by Spencer, it crashed in July 1923, whereby Spencer was killed. Cierva himself rated it as "not a good airplane". The cause of the crash could have been the relatively heavy fuselage, which had previously been reinforced by the “differential horizontal stabilizer” due to the high torsional load.

impact

After the C.5 crashed, Cierva realized that he could no longer finance further development. 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 Cierva C.6 could be built in the workshops of the Spanish Air Force in Cuatro Vientos.

See also

• List of gyroplanes

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 compilation of aviation. No. 51, pp. 1424 ff., 1984, Marshall Cavendish.
• TR Hiett: Cierva's rotating wings . In: AIR Enthusiast July / August 2003, pp. 26–31

Web links

• Photo of the C.4 on fly.historicwings.com (accessed October 6, 2017)

Individual evidence

1. ↑ ^{a b} Bruce H. Charnov: From Autogiro to Gyroplane , Praeger, Westport Connecticut 2003, ISBN 1-56720-503-8 , p. 31