2-bladed rotors mounted on the wingtip provide thrust in takeoff and landing, but scissor closed in flight to become part of the wing. Custom Joby electric motors directly drive both wingtip blades, as well the tilting tail rotor, and contribute to a low noise signature. Joby motor controllers drive the wingtip motors and provide precise and reliable control of both RPM and position.
A future 275 lb-class hybrid-electric UAV development of this configuration has the potential to become the first VTOL aircraft to achieve 24 hour endurance.
Drag the slider to illustrate the transition between VTOL and cruise configurations. The tail propeller, which provides pitch control in vertical flight, tilts forward as the aircraft gains speed after a vertical takeoff to become the sole propulsion source in forward flight. The wingtips also tilt — differentially for yaw control in vertical flight, and together to provide more forward thrust when accelerating after takeoff.
The Lotus has its roots in the NASA "Dos Samara" UAV concept. Although clever, this configuation experiences various structural and aerodynamic compromises by using single-bladed wingtip rotors. The Lotus addresses all of these with a 2-bladed configuration incorporating a deceptively simple mechanism to transform these surfaces from rotor blades to wingtips in seconds.
Extensive CFD analysis was employed in the design of the wingtip rotor blades, which must be aerodynamic in wildly different flight conditions, since they also form the tips of the wings in forward flight.
|Demonstrator||Potential Production UAV|
|Gross weight||55 lb||275 lb class|
|Payload||7 lb||60 lb|
|Wingspan||11 ft||22 ft|
|Endurance||1+ hr||24 hr|
|Cruise speed||62 knots||100 knots|
|Cruise altitude||10,000 ft||21,000 ft|
|Total power||4 hp||20 hp|
|Total battery mass||10 lb||25 lb|
|Fuel capacity||N/A||9 gallons (diesel)|