The Size Of Blue Jays: Tiny Planes To Show Their Stuff In Competition

May 3, 1999

GAINESVILLE — As an avid windsurfer, Peter Ifju knows firsthand how a strong, light, flexible sail can make the best of whatever the wind has to offer.

So when the assistant professor of aerospace engineering at the University of Florida began pondering how to design tiny airplanes that would fly well, one strategy he decided to try was replacing traditional rigid wings with flexible ones.

The bat-like planes that resulted are the smallest, lightest and most reliable planes created to date as part of a 3-year-old research effort in the UF department of aerospace engineering, mechanics and engineering science. They will be put to the test Saturday, when designers of so-called “micro-aerial vehicles” from the United States and Canada gather near Gainesville for the third annual International Micro Air Vehicle Competition.

Ifju and Dave Jenkins, a UF associate professor of aerospace engineering, began looking last fall into trying flexible wings on the remote-controlled airplanes after receiving a $20,000 exploratory grant from the National Science Foundation for the research.

The Pentagon has proposed a $35 million effort to develop 6-inch micro-air vehicles as 21st-century surveillance planes. The military envisions soldiers using the planes, equipped with miniature videocameras, to scope out hostile terrain. The planes also could have civilian uses. Police, for example, could use them to gather information covertly in a hostage situation or gather advance information on an emergency scene.

The object of Saturday’s event is for competitors’ planes, equipped with cameras, to fly about a third of a mile, then beam back a video image of a target on the ground.

The first year of the competition, the winner’s plane had a maximum dimension of 30 inches. Last year, the winner was 14.5 inches. This year, the winner likely will be under 10 inches, said Rafi Haftka, a UF professor of aerospace engineering who is coordinating the competition with Jenkins and Ed Walsh, a UF professor of aerospace engineering. UF’s smallest entry is 8 inches and weighs just 3 1/4 ounces.

Funded with a $500,000 grant from the Defense Advanced Research Projects Agency and the U.S. Air Force, UF aerospace engineering researchers are taking several approaches. Ifju said he is trying flexible wings to overcome two problems inherent in tiny planes: achieving adequate lift and withstanding strong winds.

As planes get smaller and smaller, they have more trouble overcoming aerodynamic drag and staying in the air, Ifju said. The planes also become increasingly vulnerable to turbulence such as wind gusts, with a small gust that would leave a full-sized plane unruffled able to send a small one into a tailspin, he said.

Ifju said flexible wings help with the turbulence problems because they change shape to accommodate excess wind. Made of carbon fiber and latex, they resemble insects’ or bats’ wings, which have evolved as extremely effective tiny flying machines.

Ifju, Jenkins and several student researchers worked unsuccessfully on flexible wing designs for months before hitting on a reliable design. The student researchers include Craig Yates, an aerospace engineering student; Louis Martinez, an engineering science student and Scott Eddinger, an electrical engineering student.

Carbon fiber, used in the fuselage as well as the wings, is stronger than aluminum but weighs a third as much, Ifju said. Though the wings bend easily at the touch, they also withstand rough landings or crashes. A gasoline-powered model plane motor, the smallest one available commercially, provides the power. The 8-inch model and others, including a 12-inch model, have been successfully flight-tested.

Ifju said he expects the UF team to enter as many as six planes, ranging in sizes from 8 to 14 inches, in Saturday’s competition. So far, two other teams have signed up to compete, including a team from Arizona State University and one independent team from Canada. The competition, which offers a cash prize to the winner, will start at 9 a.m. at a grassy field near Archer, about 15 miles southwest of Gainesville.

The competition is sponsored by the aerospace engineering department; Sanders, a Lockheed Martin company; the International Society of Structural and Multidisciplinary Optimization; and Boeing.