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Juan de la Cierva | |
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| Born | Juan de la Cierva y Codorníu (1895-09-21)21 September 1895 Murcia, Spain |
| Died | 9 December 1936(1936-12-09) (aged 41) Croydon, United Kingdom |
| Resting place | La Almudena Cemetery,Madrid, Spain |
| Alma mater | Escuela Especial de Ingenieros de Caminos, Canales y Puertos |
| Occupation(s) | Civil engineer,aviator,inventor |
| Known for | Inventor of theautogyro |
| Awards | Daniel Guggenheim Medal(1932) Elliott Cresson Medal(1933) |
Juan de la Cierva y Codorníu, 1st Count of la Cierva ([ˈxwandelaˈθjeɾβajkoðoɾˈni.u]; 21 September 1895 – 9 December 1936), was a Spanishcivil engineer, pilot and a self-taught aeronautical engineer. His most famous accomplishment was the invention in 1920 of arotorcraft[1][2] calledAutogiro,[3] a single-rotor type of aircraft that came to be calledautogyro in the English language. In 1923, after four years of experimentation, De la Cierva developed the articulated rotor, which resulted in the world's first successful flight of a stable rotary-wing aircraft, with hisC.4 prototype.
Juan de la Cierva was born to a wealthy, aristocratic Spanish family, and for a time his father was the war minister.[4] At the age of eight he was spending his pocket money with his friends on experiments with gliders in one of his father's work sheds. In their teens they constructed an aeroplane from the wreckage they had bought from a French aviator who had crashed the plane. The final aeroplane used wood from a Spanish bar counter for the propeller.[4] He eventually earned a civil engineering degree and after building and testing the first successful autogyro, moved to the United Kingdom in 1925, where, with the support of Scottish industrialistJames G. Weir, he established theCierva Autogiro Company.
At the outbreak of theSpanish Civil War, De la Cierva supported the Nationalist coalition forces, helping the rebels to obtain theDe Havilland DH-89 'Dragon Rapide' which flew General Franco from theCanary Islands toSpanish Morocco. His brother was summarily executed by theRepublican army inParacuellos del Jarama.
De la Cierva started building aircraft in 1912. In 1914, he designed and built a tri-motor aeroplane which was accepted by the Spanish government.[4] In 1919 he started to consider the use of arotor to generate lift at low airspeed, and eliminate the risk ofstall.
In order to achieve this, he used the ability of a lifting rotor toautorotate, whereby at a suitable pitch setting, a rotor will continue to rotate without mechanical drive, sustained by the torque equilibrium of the lift and drag forces acting on the blades. With De la Cierva's autogyro, the rotor was drawn through the air by means of a conventionalpropeller, with the result that the rotor generated sufficient lift to sustain level flight, climb and descent.
Before this could be satisfactorily achieved, De la Cierva experienced several failures primarily associated with the unbalanced rolling movement generated when attempting take-off, due todissymmetry of lift between the advancing and retreating blades. This major difficulty was resolved by the introduction of the flapping hinge. In 1923, De la Cierva's first successful autogyro was flown at Getafe aerodrome in Spain by Lt. Gomez Spencer.[4]
This pioneering work was carried out in De la Cierva's native Spain. In 1925, he brought hisC.6 to Britain and demonstrated it to theAir Ministry atFarnborough, Hampshire. This machine had a four blade rotor with flapping hinges but relied upon conventional airplane controls forpitch, roll andyaw. It was based upon anAvro 504K fuselage, initial rotation of the rotor was achieved by the rapid uncoiling of a rope passed around stops on the undersides of the blades.
The Farnborough demonstration was a great success, and resulted in an invitation to continue the work in the UK. As a direct result, and with the assistance of the Scottish industrialistJames George Weir, the Cierva Autogiro Company, Ltd., was formed the following year. From the outset De la Cierva concentrated upon the design and the manufacture of rotor systems, relying on other established aircraft manufacturers to produce the airframes, predominantly theA.V. Roe Company.
The Avro builtC.8 was a refinement of the C.6, with the more powerful180hp Lynx radial engine, and several C.8s were built. The C.8R incorporated drag hinges, due to blade flapping motion causing high blade root stresses in the rotor plane of rotation; this modification resulted in other problems such as ground resonance for which drag hinge dampers were fitted.
The resolution of these fundamental rotor problems opened the way to progress, confidence built up rapidly, and after several cross-country flights a C.8L4 was entered for the 1928Kings Cup Air Race. Although forced to withdraw, the C.8L4 subsequently completed a 4,800 km (3,000 mi) tour of the British Isles. Later that year it flew fromLondon toParis thus becoming the first rotating wing aircraft to cross theEnglish Channel. The tour was subsequently extended to includeBerlin,Brussels andAmsterdam.
A predominant problem with the autogyro was driving the rotor prior to takeoff. Several methods were attempted in addition to the coiled rope system, which could take the rotor speed to 50% of that required, at which point movement along the ground to reach flying speed was necessary, while tilting the rotor to establish autorotation.
Another approach was to tilt the tail stabiliser to deflect engine slipstream up through the rotor. The most acceptable solution was finally achieved with theC.19 Mk.4, which was produced in some quantities; a direct drive from the engine to the rotor was fitted, through which the rotor could be accelerated up to speed. The system was then declutched prior to executing the take-off run.
As De la Cierva's autogyros achieved success and acceptance, others began to follow and with them came further innovation. Most important was the development of direct rotor control through cyclic pitch variation, achieved initially by tilting the rotor hub and subsequently byRaoul Hafner by the application of a spider mechanism that acted directly on each rotor blade. The first production direct control autogyro was theC.30, produced in quantity by Avro,Liore et Olivier, andFocke-Wulf. This machine allowed for change of motion in any direction – upwards, downwards or sideways – by the tilting of the horizontal rotors and also effected a minimising of some of controls used in more conventional aircraft of the period.[5] Development of cyclic pitch variation was also influenced by the Dutch helicopter pioneerAlbert Gillis von Baumhauer, who adoptedswashplate principle in his designs and probably influenced Cierva in their meeting in 1928.[6]
The introduction of jump take-off was another major improvement in capability. The rotor was accelerated in no-lift pitch until the rotor speed required for flight was achieved, and then declutched. The loss of torque caused the blades to swing forward on angled drag hinges with a resultant increase in collective pitch, causing the aircraft to leap into the air. With all the engine power now applied to the forward thrusting propeller, it was now possible to continue in forward flight with the rotor in autorotation.
TheC.40 was the first production jump takeoff autogyro.
Autogyros were built in many countries under De la Cierva licences, including France, Germany, Japan, Russia and the United States.
De la Cierva's motivation was to produce an aircraft that would not stall but near the end of his life he accepted the advantages offered by the helicopter and began the initial work towards that end. In 1936, the Cierva Autogiro Company, Ltd. responded to a British Air Ministry specification for a Royal Navy helicopter with thegyrodyne.
On the morning of 9 December 1936, he boarded a DutchDC-2 ofKLM atCroydon Airfield, bound forAmsterdam. After delay caused by heavyfog, the airliner took off at about 10:30 am but drifted slightly off course after takeoff and exploded after flying into a house on gently rising terrain to the south of the airport, killing 15 people, among them de la Cierva.[7]
Juan de la Cierva's work on rotor-wing dynamics made possible the modern helicopter, whose development as a practical means of flight had been prevented by a lack of understanding of these matters. The understanding that he established is applicable to all rotor-winged aircraft; though lacking true vertical flight capability, work on the autogyro forms the basis for helicopter analysis.[8]
De la Cierva's death in an aeroplane crash in December 1936 prevented him from fulfilling his recent decision to build a useful and reliable aircraft capable of true vertical flight for the Royal Navy, but it was his work on the autogyro that was used to achieve this goal. Technology developed for the autogyro was used in the development of the experimentalFw 61 helicopter, which was flown in 1936 by Cierva Autogiro Company licenseeFocke-Achgelis. His pioneering work also led to the development of a third type ofrotorcraft, thegyrodyne, a concept of his former technical assistant and successor as chief technical officer of the Cierva Autogyro Company, Dr.James Allan Jamieson Bennett.
In 1966, Juan de la Cierva was inducted into theInternational Aerospace Hall of Fame for his innovation in rotor blade technology, using them to generate lift and to control the aircraft's attitude with precision.[9] TheJuan de la Cierva scholarship from the SpanishMinistry of Science is named after him.[10]
| Awards | ||
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| Preceded by | Recipient of theElliott Cresson Medal 1933 | Succeeded by |
| Spanish nobility | ||
| New creation | Count of De La Cierva 1954 | Succeeded by Jaime de la Cierva Gómez-Acebo |
