Open and closed loop gust loads analyses for a flying wing configuration with variable longitudinal stability

Abstract

This work presents results of dynamic “one-minus-cosine” gust load simulations for a flying wing configuration. The in-house toolbox Loads Kernel is used for the loads analysis of the free flying aircraft. Flight mechanical characteristics are captured by application of a non-linear equation of motion in the time domain. The underlying aerodynamic methods are the Vortex Lattice and the Doublet Lattice Method with a rational function approximation (RFA) for unsteady simulations in the time domain. The structural model was created using DLR's parametric ModGen/Nastran design process. The structure is optimized for minimum structural weight with typical design load cases including maneuver, gust and landing loads. In this article, the focus lies on gust encounters and the flight characteristics of a flying wing configuration. It differs from classical configurations (wing-fuselage-empennage) due to a pronounced nose-up pitching motion when the aircraft enters the gust field. Finally, a flight controller is designed to increase the pitching stability. This is essential for the flight of a naturally unstable configuration. It is shown that the loads during a gust encounter increase significantly. The influence on the structural weight is small as the layout is very robust and the required material thickness is below the minimum thickness in most areas.