Spanish engineer Marquis Raul Pateras Pescara began building rotary wing machines, initially in Barcelona, but after 1922, in France.
| Compound |
| In June 1922, Pescara proposed a co-axial rotor aircraft where the rotors could stop and form a bi-plane. A pusher propeller provided forward thrust. |
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Sources:
- The V/STOL Encyclopedia Series: Volume 2 France 10 December 2002.