The editors of the journal Bioinspiration & Biomimetics recently came out with a special issue on the engineering of small UAVs to emulate the power, grace and precision of natural flight—not just in birds and bees, but also moths, bats, squirrels, flying snakes (!), and common houseflies (which are, according to issue editor David Lentink of Stanford University, “in many ways a gold standard for high-performance flight”).
One project, led by MIT grad student Joseph Moore, aims to figure out how birds pull off those tricky landings on tree branches and power lines. They come in fast, go into a stall, then, just as their velocity drops to zero, perch themselves on a barely visible wire. What’s more, birds land at a very high angle of attack—up to 90 degrees, as compared to 8.1 degrees for an F-18 landing on an aircraft carrier. To engineers, this is more than just impressive. If they can figure out a way for small drones to land on power lines, UAVs might be able to recharge themselves during long flights and extend their overall range.
Moore and his colleagues built a glider with a single actuator at the tail, then designed a feedback control system that allowed it to successfully approach a wire more than 10 feet away (video evidence above). The goal was to come within 2.5 inches of the perch; actual landings will come later. But the authors have already shown that “propulsion is not necessary for high performance perching,” and that their method can result in faster landings than perching methods using Vertical Takeoff and Landing (VTOL) aircraft.