Cierva

History

Juan de la Cierva y Codorníu, 1st Count of la Cierva was born on 21 September 1895 to a wealthy, aristocratic Spanish family. He became interested in aeronautics as a teenager and studied the work of Samuel Langley, Clément Ader, Octave Chanute and other pioneers of glider flight. With several friends, Cierva built two gliders in 1911, but both crashed. Undeterred, in 1912 they rebuilt the wreckage of a Sommer biplane into a monoplane known as the BCD-1, which flew surprisingly well and was reportedly the first successful Spanish-built airplane.

Cierva attended Madrid Engineering College and graduated in 1917. Encouraged by his earlier aircraft fabrication experience, he entered a Spanish government military competition and designed a large trimotor bomber, but it crashed during a test flight in July 1919. Disheartened, he returned to the family business but remained interested in aviation, and soon turned his attention to the problems of low-speed flight. He arrived at a concept of auto-rotating wings attached to a conventional winged aircraft, calling this basic design concept an Autogiro, and it would be the basis for all his subsequent work. . In 1923, Cierva's first successful Autogiro was flown at Getafe aerodrome in Spain.

Though his pioneering work was carried out in his native Spain, in 1925 he brought his C.6, based upon an Avro 504K fuselage, to Britain at the invitation of the Director of Scientific Research at the Air Ministry, H. E. Wimperis, and demonstrated it to the Air Ministry at the RAE Farnborough, Hampshire on 10 October 1925, the results being evaluated against Specification 14/25 for 'Demonstration Flight of Cierva Autogiro’. The Farnborough demonstration was a great success, and resulted in an invitation to continue the work in the UK. In association with financier Hugh Kindersley, James G. Weir of G & J Weir, Ltd., a Glasgow marine engineering firm, funded Cierva's development of the Autogiro and the Cierva Autogiro Company, Ltd., was formed the following year, with James G. Weir as Chairman. From the outset Cierva concentrated upon the design and the manufacture of rotor systems, relying on other established aircraft manufacturers to produce the airframes, predominantly the A.V. Roe Company.

In February 1927, Royal Air Force test pilot Frank T. Courtney suffered a near-fatal crash when two rotor blades failed on the C.6C he was flying, leading Cierva to drastically improve the rotor hub design. The Avro built C.8 was a refinement of the C.6, with the more powerful 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.

Cierva learned to fly so he could personally test his theories on the further evolution of a practical gyroplane, gaining his RAeC Aviators Certificate (No. 8077) on 11 February 1927, flying a de Havilland Cirrus Moth. On September 18, 1928, he flew with a passenger in a C.8L across the English Channel from London to Paris, the first international flight by an Autogiro. He and RAF test pilot Flight Lt. H.C.A. Rawson later made a leisurely 3,000-mile tour of European cities in an improved model to seek licensees, drawing large crowds.

Among those requesting manufacturing rights was Harold F. Pitcairn, a Pennsylvania aircraft designer who had created the Mailwing airplane series in the late 1920s. Pitcairn became interested in developing safer aircraft, and after flying a C.8 during a visit to Britain in 1928, he saw rotorcraft as the ultimate approach to achieving this goal. He formed the Pitcairn-Cierva Autogiro Company to gain the U.S. rights to Cierva’s patents and inventions. Cierva's prototypes were built by several British companies, including Comper, de Havilland, Parnall and Westland, but by far the most were built by A.V. Roe, including Cierva’s first production machine, the C.19 of 1929 and the most successful of all, the C.30 of 1933, also built under license in Germany by Focke-Wulf, and in France by Lioré-et-Olivier. It was first the C.19, then finally the C.30, where Cierva solved the problems associated with vertical, or near vertical, take-off.

In flight, an autogyro’s rotor autorotates from the airflow passing through the rotor disc, forward propulsion being provided by the engine and its conventional propeller. If the engine fails, the machine autorotates down and can be landed in a small area. To take off, however, the rotor needed to revolve at a high enough speed to create sufficient lift to overcome the aircraft’s weight. This ‘spin-up’ proved problematic. The successful C.19 MkIV of 1929 had a biplane tail that could have the ‘elevators’ set to direct the propeller wash into the rotor disc. This worked but was itself replaced by the obvious step of using clutched power from the engine to spin the rotor up, a system fitted to the C.30 family.

The next requirement was ‘direct control’, where the rotor disc itself could be used to manoeuvre the aircraft in pitch, roll and yaw. This was also achieved with the C.30 with the hanging control stick and movable rotor head. Until then, autogyros had used conventional flying control surfaces, which at slow speeds, such as take-off or touchdown, had insufficient airflow to manoeuvre.

On 9 December 1936, Cierva was killed in the Croydon KLM airliner accident when the aircraft in which he was a passenger crashed after taking off in fog. Dr. James Allan Jamieson Bennett (1903 – 1973), who had joined G & J Weir, Ltd. as physicist in 1932, and later worked on autogyro and helicopter development under the direction of Chief Engineer Cyril G. Pullin before becoming Cierva's Technical Assistant, now became Technical Director of the Cierva Autogiro Company, and remained in the position until leaving in 1939. It was Bennet who developed the last innovation in autogyro design, the jump-takeoff mechanism. In addition to making important contributions to autogyro controls while at Cierva, Bennett carried through with Cierva's decision to offer the Royal Navy an aircraft capable of true vertical flight. Bennett's innovative design, a new type of rotorcraft that combined key features of the autogyro and helicopter, was tendered to the Air Ministry as the Cierva C.41 Gyrodyne, but preliminary work was abandoned with the outbreak of World War II. Bennett joined Fairey Aviation in 1945, where he continued the development of the C.41 design to create the first gyrodyne, the Fairey FB-1, that first flew in 1947.

With £2,000 per month monthly expenses with no significant offsetting income, G & J Weir, Ltd. suspended operations of the Cierva Autogiro Company in 1939, retaining the resulting shell as a patent holding company only. Its staff was reassigned to various aircraft development and operations responsibilities. Work proceeded under Air Ministry development contracts for the C.41 Gyrodyne and Weirs' own W.6 helicopter, but in June 1940 G & J Weir, Ltd. terminated development to free up resources for more pressing needs related to the war effort.

At the insistence of James G. Weir, the Ministry of Aircraft Production authorized development of a helicopter under Specification E.16/43, and the Aircraft Department of G & J Weir, Ltd. was reconstituted as the Cierva Autogiro Company, and moved to Mollart Engineering's premises in Thames Ditton in 1943. There the company developed a helicopter to test Weir's conception of an unstallable, low vibration rotor, simplified pilot controls, and alternate means of torque correction and yaw control. This became the W.9 with automatic “collective control” (which controls lift from the blades) and the world’s first NOTAR (no tail rotor) system, using the engine exhaust for anti-torque control.

The Cierva Autogiro Co. Ltd moved to to Eastleigh in 1946, where they produced the three-rotor Air Horse, at the time the world's largest helicopter. Unfortunately, the first prototype of the Air Horse crashed, killing all on board. This led Weir to cease further investment in the company and its development contracts were transferred to Saunders-Roe.

Company References

1. Cierva Autogiros - The Development of Rotary-Wing Flight, Peter W. Brooks (Airlife, 1988)
2. Autogiro, Arthur W.J.G. Ord-Hume (Mushroom Model Publications, 2009)
3. Wessex Aviation Industry, Mike Phipp (Amberley Publishing, 2009)
4. Scottish Contributions to Rotary Wing Flight, Prof. Dugald Cameron and Dr Douglas Thomson (AHS 64th Annual Forum, April 29th - May 1st, 2008, Montreal, Canada)
5. https://www.historynet.com/juan-de-la-cierva-autogiro-genius/ (Originally published in the September 2012 issue of Aviation History).
6. The Cierva Autodynamic Rotor by Jean-Pierre Harrison, NASA
7. The Cierva Gyrodyne by Jean-Pierre Harrison, NASA
8. Flight 25 Mar 1943

Project Data