Adaptive Trailing Edge Device Research Articles

Aero-servo-elastic design of a morphing wing trailing edge system for enhanced cruise performance

The Adaptive Trailing Edge Device (ATED) was a sub-project inside SARISTU (Smart Intelligent Aircraft Structures, 2011–2015), an L2 level project of the 7th EU Framework programme coordinated by Airbus, aimed at developing technologies for realizing a morphing wing for the improvement of general aircraft performance. That study, divided into design, manufacturing and testing phases, involved universities, research centers and leading industries of the European consortium. The aim of the present work is to predict the aero-servo-elastic impact of a full-scale morphing wing trailing edge on a CS-25 category aircraft. Within SARISTU, many FE models were realized, taking into account the complete and complex adaptive wing structure behavior. Those numerical representations referred to the 5.5 m wing section that was then employed for wind tunnel tests; such segment included the winglet and was representative of the outer wing segment (namely, the so-called “aileron region”). Those models were taken as reference to develop numerical representation of the considered wing that better suited the complete wing segment, from the fuselage attachment to the end of the flap region. Therefore, a scaling process was necessary, aimed at translating the former architectures to the new geometries. This kind of extrapolation had the advantage to take into account larger rooms to host the complex actuator system with all its components. MSC Nastran® FE models were elaborated to estimate stiffness and inertial distributions that allowed constructing the stick-beam mock-up of the complete structure. Several cases of flutter analysis were investigated by an in-house code, SANDY 3.0, to verify the safety requirements imposed by the applicable aviation regulations (paragraph 25.629, parts a and b-1). Moreover, dynamic stability assessment was performed with respect to single and combined failures of the actuation line and kinematic chain enabling morphing in order to support FHA (Fault and Hazard Analysis).

Hinge rotation of a morphing rib using FBG strain sensors

An original sensor system based on Fiber Bragg Gratings (FBG) for the strain monitoring of an adaptive wing element is presented in this paper. One of the main aims of the SARISTU project is in fact to measure the shape of a deformable wing for performance optimization. In detail, an Adaptive Trailing Edge (ATE) is monitored chord- and span-wise in order to estimate the deviation between the actual and the desired shape and, then, to allow attaining a prediction of the real aerodynamic behavior with respect to the expected one. The integration of a sensor system is not trivial: it has to fit inside the available room and to comply with the primary issue of the FBG protection. Moreover, dealing with morphing structures, large deformations are expected and a certain modulation is necessary to keep the measured strain inside the permissible measure range. In what follows, the mathematical model of an original FBG-based structural sensor system is presented, designed to evaluate the chord-wise strain of an Adaptive Trailing Edge device. Numerical and experimental results are compared, using a proof-of-concept setup. Further investigations aimed at improving the sensor capabilities, were finally addressed. The elasticity of the sensor structure was exploited to enlarge both the measurement and the linearity range. An optimisation process was then implemented to find out an optimal thickness distribution of the sensor system in order to alleviate the strain level within the referred component.