Load Alleviation on a Joined-Wing Unmanned Aircraft

摘要

In this paper a method of alleviating wing structural load of a flexible aircraft during a symmetric balancednmaneuver is presented. An application on the unmanned aircraft in development at the Italian Aerospace ResearchnCenter, high-altitude performance demonstrator, characterized by a joined-wing configuration, is illustrated. Thisnload alleviation technique enables a desired value of the bending moment on a fixed wing control station to benobtained. The load reduction is achieved by deflecting a suitable set of flight-control surfaces, by always keeping thenvertical load factor constant to preserve the maneuvering performance. The main hypotheses are: significantnaeroelastic effects, linear behavior of aerodynamics and structure, and unvarying tensor of inertia under structuralndeflections. High-altitude performance demonstrator is a scaled performance demonstrator of an 80m-wing spannhigh-altitude and long endurance unmanned aircraft in a joined-wing configuration. The advantages in terms ofnperformance, fatigue life extension, and weight reduction can be achieved from the integration of an onboard loadnalleviation system. The results show that the attainable value of load alleviation in terms of bending momentnreduction at the wing root is 37%.Moreover, the test-case analyses show that the maximum value of the alleviationnincreaseswith respect to the dynamic pressure although the load distribution varies because of significant aeroelasticneffects.