The tilt rotor/SLT concept is a hybrid of two hybrids. By combining the benefits of a separate lift/thrust system with those of a tilt rotor, this airframe carries significantly less dead weight during both horizontal and vertical flight operations.
The tilt rotor/SLT uses nacelles that are actuated by differential thrust. IMUs and/or position sensors are located within the nacelles which are independently stabilized.
The use of multiple smaller rotors on the nacelles instead of a single, larger rotor provides faster reaction time which increases stability.
The Ehang184 is an amazing Chinese aircraft that is currently being tested in the United States and will be used as an air taxi in Dubai as soon as July of 2017. One great thing about the success of this aircraft is that it demonstrates the ablity of electrically powered, VTOL aircraft to operate safely and practically. Many said multi-rotors would not scale up. Others said rotors could not practically exceed 700mm. Then, Ehang went and built a manned multi-rotor with 1600mm rotors and 48km of range. An electric, autonomous, flying car.
The Ehang184 demonstrates that the technologies required to build something like the tilt rotor/SLT hybrid are already available and practical. By taking these developments and applying them to a wing-borne and more efficient tilt rotor/SLT airframe, both speed and range can be enhanced. Because the tilt rotor/SLT airframe is completely controlled by motor speed, the desired simplicity of a multi-rotor is retained.
Unlike other tilt rotors, the TR/SLT concept has vertical lift distributed along the wingspan instead of lifting the aircraft by the wingtips. This eliminates the normal structural issues while allowing the wings to be of thin and lightweight construction.
Coaxial electric propellers are popular in electric aircraft design. For VTOL applications, they provide a compact method of increasing lift while providing redundancy. For cruise applications, coaxial propellers provide redundancy while increasing efficiency.
Image courtesy of Wired magazine.
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