Before the experimental
Cierva C.19 Mk V, autogyros had been controlled in the same way as fixed-wing aircraft, that is by deflecting the air flowing over moving surfaces such as ailerons, elevators and rudder. At the very low speeds encountered in autogyro flight, particularly during landing, these controls became ineffective. The experimental machine showed that the way forward was a tilting rotor hub fitted with a hanging stick extending to the pilot's cockpit with which he could change the rotor plane. This was known as direct control and was fitted to the
C.30. The production variant, called C.30A in England, was preceded by several development machines. The first production design in the series was the C.30, a radial-engined autogyro with a three-blade, 37 ft (11.3 m) rotor mounted on an aft-leaning tripod, the control column extending into the rear of the two cockpits. The engine was the five-cylinder, 105 hp (78 kW)
Armstrong Siddeley Genet Major I used in the C.19 series. The fabric-covered fuselage carried an unbraced tailplane, without elevators but with turned-up tips. The port side of the tailplane had an inverted aerofoil section to counter roll-axis torque produced by the propeller. As with most autogyros, a high vertical tail was precluded by the sagging resting rotor, so the dorsal fin was long and low, extending well aft of the tailplane like a fixed rudder and augmented by a ventral fin. The wide-track undercarriage had a pair of single, wire-braced legs and a small tail wheel was fitted. This model flew in April 1933. It was followed by four improved machines designated C.30P (P here for pre-production) which differed in having a four-legged pyramid rotor mounting and a reinforced undercarriage with three struts per side. The rotor could be folded rearwards for transport. The C.30P used the more powerful (140 hp, 104 kW) seven-cylinder
Armstrong Siddeley Genet Major IA radial engine. 's
Rearsby Aerodrome in June 1951 The production model, called the C.30A by
Avro, was built under licence in Britain, France and Germany and was similar to the C.30P. The main alteration was a further increase in undercarriage track with revised strutting, the uppermost leg having a pronounced knee with wire bracing. There was additional bracing to the
tailplane and both it and the fin carried small movable trimming surfaces. Each licensee used nationally built engines and used slightly different names. In all, 143 production C.30s were built, making it by far the most numerous pre-war autogyro. Between 1933 and 1936, de la Cierva used one C.30A (
G-ACWF) to test his last contribution to autogyro development before his death in the crash of a
KLM Douglas DC-2 airliner when taking off at
Croydon Airfield in England on 9 December 1936. To enable the autogyro to take off without forward ground travel, Cierva produced the "autodynamic" rotor head, which allowed the rotor to be spun up by the engine in the usual way but to higher than take-off r.p.m at zero rotor incidence and then to reach operational positive pitch suddenly enough to jump some 20 ft (6 m) upwards. At least one
Royal Air Force (RAF) C.30A was on
floats as a
Sea Rota in January 1935.
Production ;Avro Avro obtained the licence in 1934 and subsequently built 78 examples, under their model designation, fitted with an
Armstrong Siddeley Genet Major IA (known in the RAF as the Civet 1) 7-cylinder radial engine producing . The first production C.30A was delivered in July 1934. ;Lioré-et-Olivier Twenty-five aircraft were built in France by
Lioré-et-Olivier as the LeO C.301 with a 175 hp (130 kW)
Salmson 9NE 9-cylinder radial engine. ;Focke-Wulf Forty aircraft were built in Germany as the Focke-Wulf Fw 30 Heuschrecke (Grasshopper) with a 140 hp (105 kW)
Siemens Sh 14A 7-cylinder radial engine. ==Operational history==