During ground manoeuvres a loss of lateral stability due to the saturation of the main landing gear tyres can cause the aircraft to enter a skid or a spin. The lateral stability is governed not only by aspects of the gear design, such as its geometry and tyre characteristics, but also by operational parameters, for example, the weather and taxiway condition. In this paper we develop an improved understanding and new presentation of the dynamics of an aircraft manoeuvring on the ground, ultimately aimed at optimisation and automation of ground operations. To investigate turning manoeuvres we apply techniques from dynamical systems theory to a modified version of a nonlinear computer model of an A320 passenger aircraft developed by the Landing Gear Group at Airbus UK. Specifically, we present a bifurcation analysis of the underlying solution structure that governs the dynamics of turning manoeuvres with dependence on the steering angle and thrust level. Furthermore, a detailed study of the behaviour when lateral stability is lost focuses on how the tyre saturation at different wheel sets lead to qualitatively different types of overall behaviour. The presented bifurcation diagrams identify parameter regions for which undesirable behaviour is avoidable and, thus, they form a foundation for defining the safe operating limits during turning manoeuvres.

The dynamics of passenger aircraft on the ground are influenced by the nonlinear characteristics of several components, including geometric nonlinearities, the aerodynamics and interactions at the tyre-ground interface. We present a fully parametrised mathematical model of a typical passenger aircraft that includes all relevant nonlinear effects. The full equations of motion are derived from first principles in terms of forces and moments acting on a rigid airframe, and they include implementations of the local models of individual components. The overall model has been developed from and validated against an existing industry-tested SimMechanics model.The key advantage of the mathematical model is that it allows for comprehensive studies of solutions and their stability with methods from dynamical systems theory, in particular, the powerful tool of numerical continuation. As a concrete example, we present a bifurcation study of how fixed-radius turning solutions depend on the aircraft's steering angle and centre of gravity position. These results are represented in a compact form as surfaces of solutions, on which we identify regions of stable turning and regions of laterally unstable solutions. The boundaries between these regions are computed directly and they allow us to determine ranges of parameter values for safe operation. The robustness of these results under the variation of additional parameters, specifically, the engine thrust and aircraft mass, are investigated. Qualitative changes in the structure of the solutions are identified and explained in detail. Overall our results give a complete description of the possible turning dynamics of the aircraft in dependence on four parameters of operational relevance.

Despite the significant improvement in safety linked to the fourth generation of airliners, the risk of encountering upset conditions remains an important consideration.Upset -which may arise from faults, external events or inappropriate pilot inputs spins. The analysis shows that these spirals and spins are connected in two-parameter space and that, by an inappropriate pilot reaction to the spiral, it is possible to enter the oscillatory spin.

This paper details five aeroelastic modelling methods applied to the study of an example high aspect ratio wing subject to high loads resulting in large structural deformations. Each method is discussed in turn and example static results from each are compared. Overall agreement is illustrated between the methods for key quantities of interest although aerodynamic modelling choices regarding the orientation of aero forces is observed to play a significant role in the agreement between predicted distributed loads and deflections. Quantitative differences resulting from linearisation of the wing model are also presented and discussed. It is found that by linearising the problem, wing deflection, aerodynamic forces and root bending are all over-estimated. Large differences are also observed between linear and nonlinear predictions of root twist, however the modelling of drag effects is deemed important to the exact nature of the observed discrepancy. Altogether, linearised assumptions are shown to have a noticeable impact on the accuracy of predicted results for the considered wing test case and are deemed unsuitable in isolation for the analysis of this class of flexible problem.

This paper proposes a low-order geometrically exact flexible beam formulation based on the utilization of generic beam shape functions to approximate distributed kinematic properties of the deformed structure. The proposed nonlinear beam shapes approach is in contrast to the majority of geometrically nonlinear treatments in the literature in which element-based—and hence high-order—discretizations are adopted. The kinematic quantities approximated specifically pertain to shear and extensional gradients as well as local orientation parameters based on an arbitrary set of globally referenced attitude parameters. In developing the dynamic equations of motion, an Euler angle parametrization is selected as it is found to yield fast computational performance. The resulting dynamic formulation is closed using an example shape function set satisfying the single generic kinematic constraint. The formulation is demonstrated via its application to the modelling of a series of static and dynamic test cases of both simple and non-prismatic structures; the simulated results are verified using MSC Nastran and an element-based intrinsic beam formulation. Through these examples, it is shown that the nonlinear beam shapes approach is able to accurately capture the beam behaviour with a very minimal number of system states.