Design of a Biplane Wing for Small-Scale Aircraft

Although the biplane wing configuration has seen little use on modern airplanes over the last 70 years, there are still a few applications where the configuration is the best solution. In the 2007 AIAA/Cessna/Raytheon Design/Build/Fly competition, a shorter wingspan yielded a better final score in the competition. The Penn State team decided on a biplane wing design for its entry, the Nittany Griffin. To properly design a biplane wing, a literature survey was completed to learn about the flow conditions unique to this configuration. The airfoil selection was based on predictions generated by XFOIL, and the wing geometry was finalized using predictions of the multiple lifting line code, FREEWAKE 2007. The configuration was driven by the goal to maximize the aircraft performance during takeoff and cruise. Minimization of induced drag was of particular importance during this process. The resulting wing geometry from the analysis was not intuitive, however, when flight tested on a remote controlled aircraft, it demonstrated much improved performance over previous wing designs. Nomenclature A, B, C = circulation coefficient