NDOF Simulation Model for Flight Control Development with Flight Test Correlation

traditional design constraints. One such issue is the coupling of an aircraft’s rigid body dynamics and structural modes that can result in issues ranging from poor flying qualities to a phenomenon known as Body Freedom Flutter (BFF). This phenomenon was first seen over five decades ago and is significant in vehicles with low tail volume and high aspect ratio wings or with a high fineness ratio fuselage. When encountered in flight, BFF can lead to divergent oscillations and catastrophic destruction of the aircraft. The solution to BFF often results in too much of a compromise in some areas of the aircraft design. In previous cases where BFF existed within the flight envelope, additional structure was added at the expense of performance. In other cases, BFF has been avoided by limiting the vehicle’s flight envelope. A possible alternative solution of active suppression has been forwarded that holds the promise of a full flight envelope and reduced structural weight. To assist the development of active flutter suppression the Flight Controls and Flutter communities must work together and develop a common language and methodology. This is important in the modeling of the vehicle so that control systems can be properly developed. This paper discusses the development of an Integrated Flight and Aeroelastic Control (IFAC) Integrated Product Team (IPT). The paper describes the modeling used by the IFAC IPT to develop the vehicle dynamic model and how the model was validated and correlated through ground and flight test.