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Cierva C.30A autogiro

The C.30A was one of the most numerous autogyros and was one of the few used by any military. Most were produced for civilian use, but 12 were made specifically for the RAF, which supplemented numbers they took into service from private owners after the start of WWII. While the RAF had originally used them in 1934 as liason aircraft, they proved most valuable in helping to calibrate radar stations. Since an autogyro could hover in a stiff wind, it could maintain a known altitude and distance for some time, allowing the adjustment of radar equipment. After the war, the RAF quickly got rid of them. In 1934, one operated by Spain landed and took off from a seaplane tender. Almost 150 C.30's were built, 78 under license in Britain by Avro (66 for the civilian market). Other military buyers included Argentina, Austria, Belgium, Denmark, Italy, the Soviet Union, Spain and Yugoslavia.

The C.30A had a crew of one and uses 4.7 gallons of aviation gas per hour at routine usage.

Subassemblies: Medium Helicopter chassis +2, Rotors -1, three fixed wheels +0.
P&P: 104-kW HP aerial gasoline engine with 104-kW prop and 39-gallon standard fuel tank [Body]; 2,000-kW batteries.
Occ: 1 XCS, 1 XPS Cargo: 2 Body

Armor

Body: 2/2C

Rotor: 4/10

Wheels: 3/5

Equipment
Body: Medium radio receiver and transmitter, navigation instruments, autopilot.

Statistics

HT: 12
HP: 82 Body, 22 Rotors, 3 each Wheel
 

Design Notes
Design speed was 109 mph. Loaded weight was decreased 9%. To better match the historical performance of autogyros, rotor area was raised to the 1,5 power for for determining top speed and to the 1.75 power for determining stall speed. Takeoff (120 yards) and landing (160 yards) distances are also far longer than is proper for an autogyro. A suggestion is to drop the takeoff run to 1/3 this and the landing run to 1/10.

Like other autogyros, the stall speed works differently than from fixed-wing aircraft. Below 34 miles per hour, the rotors begin losing lift but, unlike lift from a wing, it is not lost suddenly; the autogyro would simply autorotate down as it lost forward speed and make a (relatively) safe landing.

Variants

Twenty-five were license built for France as the LeO C.301, with a 130-kW engine.

Focke-Wulf in Germany built forty under license.

A single C.30A in 1936 was tested with a special rotor head known as “Autodynamic”. While autogyros had used power form the engine to pre-spin the rotors for a few years, this went a step farther and spun them at a much higher speed very briefly, causing the C.30 to leap straight up in the air twenty feet, at which point full power was applied to the propeller for forward flight. This was Cierva's last major contribution to the autogyro before his death later that year.

The C.40 (1938) was similar, but seated two men side-by-side. Nine were built, eight of which served with the RAF.