Gust load alleviation and aerodynamic stability derivatives of flexible composite wing

Abstract

Gust load due to atmospheric turbulence is mandatory to be considered in the aircraft analysis as part of airworthiness requirement. The gust load alleviation plays an important role to effectively utilize the wing structural flexibility without ignoring the safety issue. In the present work, a method to alleviate the wing gust load is proposed by considering the structural flexibility of the wing and proper arrangement of composite material layers. The approach takes into account the wing planform, wing composite thickness and material direction, wing structural dynamic frequencies and modes, steady and unsteady aerodynamics of the wing surface. The objective of the study is to minimize the wing root bending moment power spectral density. The constraint of the study includes the wing material requirement, wing configuration, and the aerodynamic wing performance. The gust load analysis of the present structural model will be compared to the literature for the validation purpose. A finite element approach is used to simulate the wing structure in combination with the doublet lattice method to model the wing aerodynamics. The gust load profile, according to aviation regulations, is used. The proposed method gives a contribution to the gust load alleviation of large transport aircraft and unmanned air vehicles. It is clearly seen that the best configuration for reducing the bending moment power spectral density is swept back wing then swept forward. The swept-back configuration (45 degrees) showed an average decrease of the bending moment by 12% for a frequency range of 0 to 100 Hz. The present work also shows that the wing composite thickness and material direction affects the aerodynamic stability derivatives as function of Mach number which are important for the design of the aircraft flight dynamic and performance.