The nexus of advanced manufacturing methods, computer-aided design tools, and modern structural-analysis software has enabled the design and fabrication of structurally complex wing structures with unique features. This is particularly true for small unmanned aircraft, in which discrete structural hinges can easily be integrated into the overall vehicle design. This paper examines the use of discrete structural hinges for tailoring the low-frequency flight dynamics of the vehicle. For sufficiently soft discrete structural hinges, substantial coupling between flexible and rigid modes occurs, leading to the potential to modify the flight dynamic behavior through structural flexibility. Using a multibody flight dynamics simulation tool with a nonlinear lifting-line aerodynamic representation, different structural-hinge elastic properties, orientation, and location on the aircraft are examined. The results for a small unmanned aircraft indicate that flexibility mostly affects the longitudinal modes and associated handling qualities of the vehicle. Changes in the short-period and phugoid modes due to flexibility caused by a set of discrete structural hinges are often antagonistic. A structural-hinge stiffness above a certain critical value tends to improve short-period flying qualities; below this value, the short-period flying qualities degrade. In addition to the stiffness characteristics of the discrete structural hinge, orientation of the hinge has a significant effect on flight dynamics. Orienting the structural hinge to produce pitch-flap coupling can triple the short-period-mode damping, which could improve a nominally Level 3 rated aircraft to a Level 1 rated aircraft.
Use of Compliant Hinges to Tailor Flight Dynamics of Unmanned Aircraft
Journal of aircraft ; 52 , 5
2015
Article (Journal)
English
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