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ated an aircraft design contest with a prize of about $9,600. Cierva designed and built a bomber, the C- 3 which had several innovative fea- tures. The aircraft had three 225 horsepower engines, an 82.5 foot wingspan and a gross weight of 11,000 pounds (Brooks, 1988). Unfortunately, during test flights the pilot stalled the plane and crashed, ending any hope of win- ning the competition. Juan de la Cierva entered poli- tics in 1919 and became a member of the Spanish Parliament. Despite his busy schedule he never lost interest in aviation. Due to the crash of the C-3, Cierva became particularly interested in designing an aircraft that would not lose lift at slow speeds. Cierva correctly reasoned that if the wings of an airplane could be rotated to generate lift, the speed of the airplane would not matter and it would not stall. The basis for this idea was autorotation. There are documented discussions of autorotation before Cierva but no one before him had been able to successfully implement it. In 1919, Cierva began developing autorota- tional models which later progressed to full scale prototypes. Various configurations including a coaxial rotor system and three, four and five bladed rotor heads were tried. All of the designs encountered the


Opposite: Juan de la Cierva the father of the Autogiro.


Above: Amelia Earhart is shown in a Pitcairn PCA-2 on April 8, 1931 at Pitcairn Field in Willow Grove, PA. On that day Earhart flew the PCA-2 to 18,415 feet and set a world altitude record. Photos: Courtesy of Dr. Bruce H. Charnov, Hofstra University 2003 "From Autogiro to Giroplane" Conference


same problem; they were not stable and rolled over. Cierva had experi- enced success with several of his models. While trying to reconcile why the models flew but the full scale prototypes did not, he realized the problem was due to dissymmetry of lift. This fundamental problem in rotary-wing flight is caused by the advancing rotor blades creating


more lift than the retreating blades. The unequal amount of lift in the rotor disk had caused Cierva’s full scale prototypes to role over. The rotor blades of the models were made out of a very flexible palm wood. This flexibility allowed the blades to bend and equalize the lift as the blades rotated around, bal- ancing the lift in the rotor disc.


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