Secret Files: Cierva Autogyros

The Mighty Cierva Air Horse at Eastleigh

Little Nellie

Many readers have seen the 1967 James Bond film ‘You Only Live Twice’, starring Sean Connery as Bond, and one of Bond’s most famous ‘leading ladies - ‘Little Nellie’. She was the miniature rocket and gun-firing tiny ‘helicopter’ featured in the film – also popular with schoolboy model makers who made the Airfix kit of her over the years following the film’s release. The Wallis WA-116 Agile Series 1, to give her the correct name, isn’t actually a helicopter, but one of a long line of autogyros [gyroplanes] originally devised by Juan de la Cierva in the 1920’s. An autogyro [anglicised spelling] is an aircraft where the lifting rotor, rather like a helicopter, when pitched at the precise angle, will ‘autorotate’ without the need for a direct drive from the engine, unlike that of a helicopter, and generate enough lift to maintain climbing, descending and level flight, but is unable to hover like a helicopter. The autogyro therefore needs an engine, which is either in front of the fuselage or, as in ‘Little Nellie’ at the rear to propel the aircraft as a normal aeroplane’s propeller would do.

Cierva (r) with A.V.Roe

This weird and wonderful type of aircraft was invented by Juan de la Cierva y Codoriniu, 1st Count of De La Cierva [to give him his full title!], the son of a wealthy Spanish family, who had trained as an aeronautical and civil engineer and also as a pilot. The young Cierva, while studying aeronautics, was determined to solve the ‘stall problem’ of existing aircraft, most of which were inherently unstable and frankly dangerous, and also investigate the ideas of a ‘helicopter’. The word ‘helicopter’ to describe a hovering flying machine had been coined in 1861 by a French inventor, d’Amecourt, and throughout the next fifty years numerous inventors including Edison, Trouve, Forlanini, Breguet and Cornu amongst many others had tried with models and full sized strange contraptions that even if they lifted off, were unstable after a few feet of altitude and could only realistically fly when tethered. Cierva’s idea was to produce an aircraft that was a hybrid of aeroplane and helicopter design that while not a helicopter in the truest sense of the word was at least stable and practical. After numerous experiments and the inevitable failures in such a new science, Cierva solved the instability that had plagued previous inventors by the almost simple expedient of incorporating a flapping hinge on the rotor blades which solved the dissymmetry between the blades as they rotated. His first successful design using the new developments was the Cierva C4, which within a month of its first flight in January 1923, had flown a 2 ½ mile circuit in 4 minutes at the average height of 100 feet – probably a total distance of more than all previous helicopter flights combined!

Cierva C6

Realising that he needed, with investment in mind, to take his aircraft and ideas to a more advanced aviation-minded nation, Cierva brought his latest aircraft, the Cierva C.6 to Britain in 1925. The C.6 was based on the Avro 552A, a variant of the tried and tested British Avro 504K fuselage, it had a four blade rotor, but the existing controls of the Avro retained for pitch, roll and yaw. Still with an air of the ‘Heath-Robinson’ about the aircraft, the method of starting the rotor spinning while stationary was by the technical [sic] use of a rope which rapidly uncoiled while passing around stops located on the underside of the rotor blades, thus bringing the rotor to 50% of the required speed for takeoff, although a direct drive to the rotor replaced this method on a later aircraft, the C.19. Cierva demonstrated the aircraft in front of a large gathering of the Air Ministry and interested parties at Farnborough in October 1925. The Air Ministry invited Cierva to continue his experiments in Britain, and with the assistance of the Scottish industrialist Air Commodore James Weir, formed the Cierva Autogiro Company Ltd in 1926, to build the aircraft in Hamble.

Not for the faint of heart! A Cierva at takeoff

Cierva’s main role in the new company, and indeed his interest, was to design and manufacture his patent rotor systems, leaving other established companies, such as Avro, to supply the main airframes and engines, although with the C.9, Cierva started to produce his own designed airframes, rather than relying on proprietary airframes from other manufacturers. The American engineer, Harold Pitcairn, had similar ideas, and came to Britain to see Cierva’s designs and obtained licensing orders to produce his own autogyros in the US, alongside his existing light aircraft products.

Cierva C19

Through various designs, including a floatplane variant, Cierva came to his, at the time, most successful variant, the C.19 of 1929. He not only produced 30 aircraft of this type at Hamble, but also agreed to licence production by Focke-Wulf in Germany and Loire et Olivier in France.

This type was exported to customers in Australia, Germany, Japan, and to the Spanish Air Force, and two went to the RAF for evaluation [K1696 and K1948]. The De Havilland/Cierva C.24 used the cabin of a DH Puss Moth with a Cierva rotor, making the first enclosed autogyro, primarily aimed at the civil market.

Cierva C30

Solving the lift problem of autogyros came with the C.30 – an aircraft with a tilting [now commonplace] rotor head. Cierva produced 78 aircraft, with 12 entering service 1933-35 as the Avro Rota I at RAF Old Sarum. Again the export and licensing market was strong, in addition to Hamble-built aircraft exported around the world, Focke-Wulf and Loire et Olivier building many aircraft under licence, with a total production of the C.30 almost reaching 150 aircraft – no mean feat in the mid-1930’s. Sadly, Cierva didn’t see further development of his aircraft – a keen test pilot, he would often be the first to fly his designs, however, as he was killed in December 1936 as a passenger on a KLM Douglas DC-2 which crashed in fog shortly after take-off from Croydon Airport. The final pure Cierva design, the C.40, had a small production run just pre-war. An improvement on the C.30, on the outbreak of war most civilian aircraft in the UK were requisitioned by the RAF and Fleet Air Arm, and the surviving civilian C.30’s and C.40’s were no exception.

Initially part of 1448 Flight based at RAF Duxford, from late 1940 until the end of the war, the ‘Rotas’ were on 529 Squadron at RAF Halton, being used for radar calibration flights. The early link with Weir from the 1920’s continued in the late ‘30’s after Cirva’s death, became formalised, with the move towards pure helicopters rather than autogyros. The twin-rotor Cierva W[Weir]5 was very similar to the slightly earlier Focke-Wulf Fw 61, famously flown INSIDE a sport pavilion by Hannah Reitsch. Post-war, the company, now based at Eastleigh, and with the prime investor being G & J Weir, produced an innovative design that had been on the drawing board since 1943 – the W.9. This helicopter used a jet efflux [very advanced for the time] in place of a tail rotor for directional control.

Cierva W9

Sadly, the aircraft was destroyed in an accident, and despite showing promise, the design was abandoned in 1946. Cierva/Weir persevered, though, and in 1948 produced what was at the time the largest helicopter in the world – the Cierva W.11 ‘Air Horse’. An enormous aircraft designed for freight and transport, it had three 47ft diameter rotors powered by a single Rolls-Royce Merlin 24 piston engine. It was projected that an even larger version could be built powered by two Merlins or two of the new Dart turboprops. The two Air Ministry prototypes were constructed by Cunliffe-Owen at Eastleigh, with the first flight 7 December 1948.

The Cierva Air Horse

Solent Sky’s Director, Alan Jones, remembers as a young lad seeing the Air Horse fly over his house – the following day, 13 June 1950, the first prototype crashed during testing, killing the crew who comprised Cierva’s chief test pilot, the Ministry of Supply’s pilot and the flight engineer. Alan’s father, an ambulance crewman, attended the crash. Cunliffe-Owen had ceased their aviation interests by then, and Sir James Weir withdrew his financial support to Cierva, with the result that existing Cierva/Weir designs were passed to Saunders-Roe, who also took over the Cunliffe-Owen factory at Eastleigh. The final product from Cierva/Weir was the W.14 of 1948, which became from 1951 the Saunders-Roe Skeeter light military helicopter – two versions of which exist in Solent Sky Museum. Along with Westland’s cancelled designs, the Skeeter [very successful in export and the home market] saw the end of Britain’s indigenous autogyro and helicopter designs and production – Westland reduced to producing US Sikorsky helicopters under licence.

The Skeeter Helicopter