Active Gust Load Alleviation by Combined Actuation of Trailing Edge and Leading Edge Flap at Transonic Speeds

Abstract

Gust load analysis plays a substantial role in the certification process of aircraft. Active gust load alleviation techniques exhibit a high potential in significantly reducing the transient gust loads and thus the overall structural weight. In this paper, two dynamic actuator concepts are studied by means of CFD methods on a generic wing-fuselage aircraft configuration. The concepts comprise spanwise segmented trailing edge flaps (TEF) and leading edge flaps (LEF), which are already existent on the research model for high-lift and maneuvering purposes. Simulations based on Euler and RANS equations are utilized to assess the aerodynamic potential of the actuators regarding alleviation of critical idealized "1-cos" type vertical gusts. 2D simulations of a representative wing section are considered in an extended parametric study to derive an initial guess for the required actuation deflections on the aircraft configuration. An iterative analysis of spanwise varying actuator amplitudes is conducted in order to obtain strong control authority over the wing bending moment (WBM) and wing torsional moment (WTM). It is shown that the TEFs are promising in terms of mitigation of gust induced WBM and the LEFs are able to compensate the WTM induced by the deflected TEFs. Unsteady phenomena are identified at large TEF deflections resulting in unfavorable response of the aircraft. The transient behavior of the force coefficients shows significant dependencies on the flap scheduling. Only small improvements are achieved through segmented flap actuation compared to continuous flap actuation for the limited investigated setups.