Optimal wing aspect ratio of highly efficient long-range aircraft

Abstract

This work investigates the potential of higher aspect ratio wings to improve the fuel efficiency of long-range aircraft. The main characteristics of high aspect ratio wings are briefly discussed and a process for aerostructural wing optimization is presented. Adaptive wing technologies based on trailing edge control surface deflections to achieve optimal lift distributions to minimize drag in cruise flight and maximize load reduction in maneuver flight are considered and supplemented by advanced structural technologies with increased strain allowable and post-buckling to reduce wing mass. In the optimization process, high-fidelity simulation methods are used to determine the flight performance in transonic cruise flight, the loads on the wing in maneuver flight and the mass of the composite wing box. Static aeroelastic effects are taken into account in all flight conditions. The minimization of fuel consumption for three typical flight missions represents the objective function. The geometric integration of the control surfaces and aircraft trim are taken into account. The application of the process to optimize the wing planform, twist distribution and the control surface deflections forms the main part of this publication. The results show an optimal wing aspect ratio in the order of 12. A further increase in aspect ratio to a value of 13.5 shows no further improvement in aerodynamic performance and the resulting fuel consumption.