The early history of the autogyro can be summed up by the history of one man, named don Juan de la Cierva. Cierva was born in Murcia, Spain, September 21, 1895. He was eight years old when the Wright brothers first flew on Dec. 17, 1903. They finally showed the rest of the world their machine in 1908. He was intrigued and inspired by their achievements, and decided to venture off and build his own airplane. No more than four years after the Wright brothers showed their airplane in 1908, had Cierva built his first airplane, which he named the BCD-1 El Cangrejo, or the BCD-1 Crab.
He did all this by age 17. His plane flew well, and was considered the first Spanish airplane. Cierva coninued to make modifications to his airplane twice more, but they didn't quite live up to what he had hoped. His third and final version of his airplane was used in a bombing competition. It flew too slowly, stalled, and crashed. He needed an aircraft that would fly low, and slow enough to get what he needed to be done. After tossing a toy helicopter from his parents balcony and studying the flight, Cierva came up with the idea of an autogyro.
Cierva came up with several ideas for his invention. The first, called the C.1, consisted of counter-rotating rotors, meaning one at the very top spinning one way, and one directly underneath it spinning another way. Unfortunately, this design never flew because the top rotor seemed to spin faster than the one beneath it, which caused it to tilt to one side.He moved onto his next design, the C.2. This design looks a little more like a conventional autogyro. It had one rotor, but with five blades. These were to be made out of a material called duralumin.
Because of the difficulty of finding duralumin and the lack of accessible funds, however, the C.2 was postponed, and he moved onto the C.3. This is the version that we know of (or don't know of until you stumbled upon this site). It had one rotor, but with three blades. Many of the things that had gone wrong with the C.1 he had fixed, but the gyro still did not fly but for a few short hops of inches maybe. He went back to the C.2 and tried again, and finally completed the C.2 in 1922. This had slightly better performance than the C.3 but the hops only increased by a few feet. The machine still did not fly. One of the main problems with Cierva's initial designs was that the rotor was rigid, meaning it was just a rotating mast with blades sticking out from it.
This created two problems. First was that it created a gyroscopic effect. As soon as the aircraft tried to move, this effect would cause the aircraft to tilt. The other problem came from unbalanced lift. As the rotor was spinning, one side would be moving the same way the aircraft was moving, increasing the relative wind speed, while the other side would be moving opposite the direction the aircraft was moving, decreasing the relative wind speed. The side with the higher wind speed would have a higher lift than the side with lower wind speed, causing the aircraft to tilt.
Cierva came up with a solution to this problem while watching an opera. One of the props for the opera was a windmill with hinged blades. Cierva decided to use hinges in his rotor designs. This allowed the blades to rise and fall depending on what direction they were moving. The blades moving with in the direction of the aircraft rose because of the higher lift, but this also decreased the speed at which they were moving through the air. The blades traveling in the opposite direction of the gyro would fall because of the lower lift, but this would increase their air speed.
The combination of the rising and falling action, which came to be known as flapping, and the increase and decrease this had on the relative wind speeds served to balance the lifts created on each side of the aircraft. The hinged blades also eliminated the gyroscopic effect caused by the rigid blades. Cierva made his new design, the C.4, with these hinged blades. On January 17, 1923, the C.4 flew, marking the first controlled flight of an autogyro. The C.4 also demonstrated the autogyro's large factor of safety in low speed flight. On January 20 of the same year, the autogiro went into a steep nose-up position after an engine failure at about 25-35 ft. In an airplane, this would have certainly resulted in an almost unrecoverable stall but the autogyro just descended gently to the ground without damage to the machine or injury to the pilot. This low speed safety was demonstrated again on January 16, 1925, when another design, the C.6, lost power after take-off at about 150-200 ft. The pilot was still able to turn the autogyro around and bring it in for a safe landing, with only slight damage to the machine.
This maneuver would have been much more difficult in an airplane, and almost certainly would have caused a horrible accident. Cierva went on to make many more designs of his invention, and many of his flight control designs were used in the development of the helicopter.