A rotary wing vehicle includes a body structure having an elongated tubular backbone or core, and a counter-rotating coaxial rotor system having rotors with each rotor having a separate motor to drive the rotors about a common rotor axis of rotation. The rotor system is used to move the rotary wing vehicle...http://www.google.es/patents/US7789341?utm_source=gb-gplus-sharePatente US7789341 - Rotary wing aircraft having a non-rotating structural backbone and a rotor blade pitch controller
Rotary wing aircraft having a non-rotating structural backbone and a rotor ...
