by Steve Pitcairn
In
1923 a young Spaniard, Juan de la Cierva, flew the first rotary-wing aircraft in controlled flight at Madrid, Spain. Cierva, the inventor and pilot of this unique aircraft, called it the Au togiro. The name came from the fact that the rotor blades rotated without power as a result of aerodynamic forces created by the movement of the aircraft through the air. The Autogiro was pulled through the air by an engine driven propeller similiar to airplanes of the day . The rotary wing which pro vided the lift, permitted slow flight and landings at virtually no forward speed . My father, Harold F. Pitcairn, who had been experimenting with rotary wing models (with limited success) heard of Cierva's work and went to Europe in 1925 to talk to Cierva and watch his new machine fly . On a sec ond trip to Europe in 1928, my father flew Cierva's latest C-8 Autogiro and in 1929 he purchased the U. S . rights to Cierva's inventions and patents. The first series of autogiros man ufactured by Pitcairn had a fixed rotor head spindle and control in flight was by means of ailerons fixed to stub wings, plus elevators and a rudder. In 1933, Pitcairn completed the design work on a tilting rotor-head (direct control) autogiro, designated the PA 22, and started flight tests . All control on the PA-22 was through movement of the rotor-head by means of the con trol stick. It was no longer necessary to have stub wings with ailerons and elevators. The rudder was retained to give extra control in slow flight and for maneuvering on the ground . Development work continued on the PA-22 and later on the AC-35, PA-33 , PA-36 and PA-39 direct-control Pit cairn autogiros. The PA-36 was an all metal, two place cabin autogiro pow ered by a 165-hp Warner Super Scarab engine located behind the cabin . The PA-36 had jump take-off capability and was designed to be driven on high ways with the rotor blades folded and the propeller disengaged. The jump take-off or vertical ascent was ac complished by rotating the rotor held in zero degree pitch until reaching 170 percent of normal flight rotor rpm. The blade angle was held in zero degree pitch by hydraulic pressure. To initiate the jump, the pilot released the hyd raulic pressure and power take-off clutch simultaneously by means of a 12 MAY 1989
button on the throttle lever. The release of hydraulic pressure automatically in creased the blade pitch to four degrees positive and the stored energy in the over-speeding blades lifted the auto giro vertically 30 feet or more. As the blades slowed to normal cruise rpm, the autogiro, with full power to the propeller, would gain forward speed and start a normal climb out. The flying characteristics of the au togiro in cruise are simliar to those of an airplane; coordination of control being through a control stick or control wheel and rudder pedals . Normal take offs are also similar to those of an
airplane in both the direct control and fixed rotor-head autogiro . The jump take-off requires an additonal degree of training and skill and obviously a maneuver not experienced by pilots of fixed-wing airplanes. Landing both types of autogiros also requires the de velopment of new skills and pilot orientation to slow and zero-speed for ward flight regimes. Before relating my experiences fly ing the PCA-2 autogiro, the differ ences in flight characteristics of the fixed spindle rotor-head autogiro and the direct control autogrio should be explained.