In the fifteenth century, artist and engineer Leonardo da Vinci envisioned a craft that flew using a single helix-shaped propeller — the aerial screw — viewed by many as the first vertical take-off and landing (VTOL) machine ever designed.
In 2020, the Vertical Flight Society’s (VFS) 37th Annual Student Design Competition challenged students from across the world to reimagine da Vinci’s design. Using modern-day analytical and design tools, students were tasked to design and demonstrate a feasible modern-day VTOL vehicle based on the aerial screw concept and demonstrate the consistency of its physics.
Unveiled at the Vertical Flight Society’s 2022 Transformative Vertical Flight Conference — Crimson Spin, a small, unmanned aerial vehicle (UAV) — flies through the combined lift of four whirring red spiral-shaped blades.
The craft was the culmination of more than two years’ worth of work stemming from UMD’s 2020 winning graduate entry. The prize-winning design, named Elico, derived its name from the Italian root for the words “helicopter,” “propeller,” “helix,” and “screw,” all rooted in Leonardo’s drawing of the aerial screw.
The design did in fact look functional — on paper and in computer simulations — but could it actually fly in reality? “We saw some really interesting behaviors in the lift mechanisms of the air screw in our computational fluid dynamics simulations and models, where we found an edge vortex that would form,” explained team member Ilya Semenov. “But with such a novel design, we couldn’t be 100 percent sure that the phenomenon was true, so creating a working model would help us validate if it was in fact happening.”
Developed as a technology demonstrator, Crimson Spin was designed as a fully autonomous, manned quadrotor vehicle, and improves on da Vinci’s design by using a tapered aerial screw rotor to provide all lift, thrust, and control of the vehicle. A modular framework allows Crimson Spin to adapt to changing mission requirements and has hover and forward flight capabilities. According to the team, it allows riders to experience the genius of Leonardo da Vinci first-hand, safely and easily, by using an all-electric power plant, ultralight composite airframe, and pushbutton operation.
“That first successful flight was an incredible moment,” said team member Austin Prete. “It took three months, just trying to get it to fly correctly.”
While the research and findings are far too preliminary to extract potential applications at this point, making a working model based on the design has been a success in and of itself.
“Just the way the air screw worked was surprising,” added James Sutherland, Ph.D. candidate and team captain of the 2020 design team. “It’s possible that the aerial screw might be less noisy or create less downwash than a regular rotor with the same amount of thrust, but there is still a lot to learn and study before we know where it could be applied.”
Prete added that another interesting finding of the design was that the screws can create the same amount of lift but with fewer rotations compared to a traditional rotor, which may contribute to the reduced downwash — a not insignificant issue when flying traditional rotorcrafts.
Since the technology is so new, the team agrees that characterizing the rotors is important so future work can be done to evaluate the aerial screw against existing rotor styles. That will help them to understand in what flight regimes the screw design might perform best.
“For example, can you make an adjustable rotor screw?” said Prete. “You can make adjustments to a traditional rotor inflight, so what adjustments could you make to an aerial screw mid-flight to change its performance?”