Technological demonstration of an adaptive aileron system

Variation of trailing edge camber proved to be one of the easiest and most effective ways to modify aerofoil shape to match different aircraft operational weights, with benefits approaching 3% of fuel savings or, equivalently, range extension. This is particularly the case of commercial planes, where both initial take-off conditions (because of the unpredictable payload or the specific required mission-transfer flight, for instance) and in-flight states (for the kerosene consumption) can undergo significant differences. Several studies (like the European Research Programs SARISTU or JTI-GRA) demonstrated that the most sensible region for installing an adaptive trailing edge system for those aims is towards the wing tip. This is unfortunately a very delicate area where usually ailerons are deployed and where significant mass insertions could affect the aeroelastic response with some risks of instabilities. Furthermore, the volume available are really limited so that the installation of a fully embedded system is challenging. Moving from the experience taken in many former projects as the cited ones, the authors faced the problem of installing a fully integrated adaptive trailing edge system within the existing structural skeleton of a reference aileron and defined a design strategy to take into account the aeroelastic modifications due to the installation of such a device. Besides, the architecture preserved the original function of that control surface so that it could work as a standard aileron (classical rigid tab movement) with the augmented function of a deformable, quasi-static shape. In this sense, the proposed system exhibited a double functionality: A conventional rigid aileron with augmented shape modification capability plus a continuous, slow change of the trailing edge, occurring during flight for compensating aircraft weight variation. The research was carried out within the Italian-Canadian program MDO-505 and led to the realisation of a multifunctional aileron with two operational motor systems (one for the classical aileron working and the other for the morphing enforcement), completely integrated so that no external element was visible or affected the aerodynamics of the wing. The manufacture of this device was possible thanks to the development of a suitable design process that allowed taking into account both the structural and the aeroelastic response of the integrated architecture. This system was part of an adaptive wing section that was completed with the realisations made by the ETS of Montreal, the Quebecoise Consortium for Aerospace Research and Innovation (CRIAQ) and the IAR-NRC, supported by Bombardier and Thales Canada. The joint demonstrator was tested in the wind tunnel at the NRC facilities in Ottawa and gave confirmation of the aerodynamic, aeroelastic and structural predictions. The paper that is herein presented deals therefore with the design process and the manufacture of an adaptive trailing edge, installed within the existing aileron system of a wing segment, to undergo wind tunnel tests. The resulting device considers the definition of the kinematic structural system, the development of the integrated actuator system, their integration and the assessment of their static and dynamic structural response, and the verification of a safe aeroelastic behavior. Numerical and experimental results are presented, achieved in lab and wind tunnel environments.