Catherine Cavagnaro, associate professor and chair of Sewanee’s Department of Mathematics and Computer Science, has been working with a team of flight research professionals in order to groom one of the University of Tennessee Space Institute's airplanes to perform like NASA's icing research planes. It is part of UTSI Professor Richard J. Ranaudo's preparation for a three-day short course in September on "In-flight Icing and Its Effects on Aircraft Handling Characteristics." “Ice build-up on aircraft in flight is incredibly dangerous in that the stability of the airplane is altered by the ice on the wing. For instance, if you and I were flying Sally, my airplane, and you bumped the control wheel by mistake, without me even touching the control wheel, the plane would right herself all on her own,” says Cavagnaro. “With ice, however, if the control wheel were bumped, the plane might diverge and be very difficult to bring back to the proper attitude. Airplanes like this are VERY difficult (perhaps impossible) to fly.”
“I'm working with Rich Ranaudo, formerly of NASA Lewis Icing Research Center, at UTSI,” said Cavagnaro. “At NASA Lewis, Rich flew the DeHavilland Twin Otter in icing conditions and the stability behavior of the airplane was recorded. Our task is to use this information to determine the settings in the Navion to simulate the Twin Otter in that flight condition. It’s a math problem.” Cavagnaro explains that UTSI has two variable stability airplanes (both Navions) in their fleet. Each is equipped with many potentiometers, which can simulate varying stability characteristics. To the pilot flying the airplane, the airplane can be made to "feel" like many other airplanes, including one covered in ice. “My job is to model the motion of the airplane and come up with the appropriate potentiometer settings,” says Cavagnaro. “This model will also serve for future Navion projects. As a pilot, I am also flying with Rich (Ranaudo) and am learning about flight testing in the process. When we're through, he will also use me as a test subject before his short course.”
"Dr. Cavagnaro is an accomplished pilot and flight crew member on the Navion during our research flights," Ranaudo noted. In September, Ranaudo is hosting a course at UTSI for pilots, each of whom will experience a flight in the Navion N66UT under this reduced stability (read unstable) condition. "This is a project I suggested to provide a short course for operational pilots, test pilots, and flight test engineers," said Ranaudo, research assistant professor in UTSI's Aviation Systems. "The training will show them how aircraft handling characteristics are degraded by ice formations on aircraft. In the 1980's, UTSI obtained two of the Variable Stability Navions, developed by Princeton University, and restored them to first-class flying condition. Shown above is Catherine Cavagnaro. Below Cavagnaro and her colleagues at UTSI pose in front of a Navion.