UC Davis

An interesting feature about birds is their ability to fly with open wings, but their footprintis almost the same as the bird’s body when perched on a branch. This feature is more prominent in birds such as the albatrosses. Albatrosses can fly 10,000 miles or 16,000 km in a stretch [1]. These long distances are possible due to their long, thin wings - up to 11 feet from wingtip to wingtip - capable of using oceanic air currents. However, near the ground, their footprint is as small as the bird’s. This reduced footprint is because of the efficient tuck-in motion of their wings. This ability to manage footprint as required is the prime inspiration of this project. These birds are also known to flap their wings 10% of the time, showing that oceanic currents are harvested efficiently to minimize the energy usage required to stay airborne.

Multirotors, a class of uncrewed aerial vehicles(UAVs), can take off and land in a smallfootprint. However, their nature of flight expends quite some energy, which affects their flight time. Fixed-wing aircraft cannot take off land in a small footprint, but they can glide when powered down due to the nature of their flight. Combining these two features resulted in hybrid vehicles called VTOLs or Vertical Takeoff Landing Aircraft. This project proposes bringing UAVs closer to operating in small footprints using wing morphing techniques. The ability to morph wings allows UAVs to be more agile in a low-footprint configuration(folded wings) and to land in denser spaces, like urban environments, rainforests, etc. Opening the wings to its entire span provides an efficient, gliding flight when required. This paper proposes a novel morphing technique, with its design driving criteria being to keep the mechanism simple to allow scalability and ease of manufacturing and prototypes the proposed morphing wing technique for aircraft with long wingspans. The mechanism involves a system of wing sections supported by torsional springs and actuated by nylon string and pulley. During takeoff and landing, the wings can stay in a tucked-in position, allowing for small footprint operations, and when required, these long, thin wings can harvest thermal updrafts to stay airborne and un-powered for an extended amount of time.