A Multifunctional Rotor Concept for Quiet and Efficient VTOL Aircraft
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Joby Aviation

One promising solution in the search for a quiet, efficient VTOL aircraft configuration employs two-blade rotors which lock into a fixed position during horizontal flight, becoming lifting surfaces. The design of these blades and their integration onto an airframe pose many challenges, including performing this blade repositioning with a mechanism that is adequately simple, reliable, lightweight, and aerodynamic; determining a blade geometry that strikes the right compromise between performance as a rotor blade and as a wingtip; and providing sufficient pitch and yaw control in vertical and transitional flight without resorting to overly complex and heavy mechanisms, such as rotor cyclic. A spiral development model is employed in which a series of increasingly large and complex subscale prototypes are built and tested. Results from these tests demonstrate the strengths, weaknesses, and design tradeoffs of this configuration. Conceptual design is aided by an aerodynamic and structural mission analysis code. Detailed aerodynamic analysis of these designs is performed in CFD, which illuminates the unusual aerodynamics of this design in vertical and horizontal flight and the effects of these aerodynamics on overall performance. Compelling applications of this concept to the personal air vehicle and on-demand aviation markets are examined.