The experimental helicopter, likely built circa 1925 by Marquis Raúl Pateras Pescara de Castelluccio, is the only aircraft remaining that bears witness to the research of this helicopter pioneer. His machines were the first to feature a system allowing cyclical variation of blade speed, the principle of which is vital to the operation of the helicopter. This experimental helicopter is among the oldest pieces in the museum’s collection.
The Marquis of Pateras-Pescara developed and piloted at least five experimental helicopters, first in Spain and then in France, with help from the Service Technique de l’Aéronautique at Issy-les-Moulineaux between 1920 and 1931. They were built according to identical principles: coaxial rotors rotating in the opposite direction, covered biplane blades, car axles. With his third helicopter he set the world record for distance in a straight line, covering 736 m, on 18 April 1924 at the Issy-les-Moulineaux aerodrome.
The experimental helicopter on display at the museum is one of the last machines built by Pescara, probably from parts taken from his previous helicopters. It features the cyclical pace control system which allows the helicopter to move horizontally, varying the angle of the rotating blades. This principle, which is essential to the operation of helicopters, was established by other pioneers at the very start of the 20th century, but Pescara was the first to attempt to apply it to his machines. The system is controlled by the pilot’s joystick, which activates the cables connected to pulleys inside the blades. They produce the angling of the blades by deforming them, via warping.
Pescara also established the application of the auto-rotation principle to helicopters. His experiments showed the utility of creating a suspension effect by applying auto-rotation of propellers. The movement enables the craft to land in the event of engine failure. It involves disengaging the rotor from the engine and adopting a descent speed that allows the blades to keep turning, driven by the relative wind, which is the speed wind.
Text: Rosène Declementi