12 Hybrid Aircraft Aerodynamics and Aerodynamic Design Considerations of Hover‐to‐Dash Convertible UAVs

Ron Barrett

The University of Kansas, Lawrence, KS, USA

12.1 Why Hover‐to‐Dash Conversion is Important

The general concept of hovering in place like a helicopter, then dashing at high speeds is not a new one. Although vertical takeoff and landing craft can be traced as far back as the time of da Vinci, truly high performance rotorcraft would not come about until the 1930s, with the record setting flights of the FA‐61. Although a plethora of helicopters came into being in the 1940s and early 1950s, forward‐flight speeds significantly beyond 100 kts would remain elusive until some unusual aircraft configurations were employed. Because of the drive to takeoff and land vertically and to dash while between these two flight phases, different combinations of powerplants, rotors, propellers, wings and thrusters were tried and tried again and again. Indeed, aircraft like the Fairey Rotodyne was a wonderful example of this chimera‐like approach to VTOL‐capable, high‐speed dashing aircraft [1]. Figure 12.1 shows an artist’s rendition of the aircraft in high speed flight. The aircraft was specifically designed for the London city center to Paris city center route without the use of conventional airports. Although the aircraft first flew in 1957, with a maximum speed of nearly 200 mph, and made 350 flights with not a single noise complaint, the primary reason given for program ...

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