Adaptive Wings: Pathway to Birds’ Superior Flight Performance

Keenan Thungtrakul/The Avion Newspaper
Photographed above, Dr. Wissa speaks about her research about looking to birds for inspiration in UAS innovation.

Keenan Thungtrakul/Senior Reporter

On Thursday, Feb. 16, the Aerospace Engineering Department hosted Dr. Aimy Wissa, assistant professor at the University of Illinois at Urbana. Dr. Wissa came to discuss her research into making adaptive wing structures that mimic bird wings. The goal of her work is to intersect biological knowledge with adaptive structural dynamics. Birds are superior at flying, so why should we not take our flying machines and adapt them to increase their performance?

Instead of making fixed wings, let us make multifunctional adaptive wings, wings that can change configuration based on different circumstances and flap. Dr. Wissa and her team of graduate and undergraduate students have already done this. They created a wing with a “compliant spine,” an engineered hinge allowing the wing to fully extend on the downstroke and twist on the upstroke. When tested, the fabric covered surface behind the spar behaved like a bird wing when flapping and the spar mechanism consumed about half as much energy compared to using a rigid spar. That is great, but are there more aerodynamic secrets we can glean from birds?

For instance, birds do not require a long runway to land, and they can change their wing shape to adapt to changing flight conditions. The secret lies in how they use their wings at high angles of attack and stall conditions. Dr. Wissa’s team noticed small spoilers close to the trailing edge on some birds that when simulated showed a reduced wake. This means the birds can delay stall so they can perch or land without need of stopping distance. These spoilers are smaller than the speed brakes on modern airliners and only work within a certain range of angles of attack. In level flight, they increase drag. The team also noted gaps in the wingtips of large birds like hawks. Wind tunnel testing of a wing model with these gaps at the tip showed an increase in lift with little effect on drag. Though how are we going to apply these newfound discoveries?

One method proposed by Dr. Wissa is unmanned aircraft. Having manned aircraft with flapping wings would be unpractical. The pilots and passengers would be subjected to nearly constant high G-force acceleration. The main point that came out of this presentation is that we are continuing to adapt our flying machines to replicate biological phenomena.

Where this might go, we shall see.