Airspace is identified through well defined volumes of the Earth's atmosphere. Airspace control is defined to consist of rules and procedures by which aircraft conduct their flight and by which aircraft approach and cross volume boundaries. Airspace control should optimise the flow of traffic under the constraint that no collision occurs. To date, the design of airspace control has been largely heuristic. Two fundamentally opposed philosophies and designs have evolved over the last fifty years. There has been little, if any, formal comparison of the relative performance of these designs.

A new conceptual conflict-avoidance model is presented showing the need to maintain situational awareness for all conflicts. It reveals the essential requirement for communication channels in the conflict avoidance function. Human perceptual performance is related the required system response to conflict. These human factors can be mathematically related to physical parameters embodied in airspace rules and procedures. The impact of changes in airspace performance due to variations in physical parameters derived from models of the communication channels can now be measured. Use of the conflict-avoidance model presented in this paper identifies serious deficiencies in present designs and postulates that fundamental architectural changes are required to reduce safety hazards and produce designs of sufficient reliability, particularly for uncontrolled airspace. Designs based on stable and adequate communications are shown to be required and are now technologically feasible.

The degree of complexity and randomness of aircraft tracking which can be safely managed is a fundamental question for a given airspace design. To answer this question and to provide optimum conflict resolution strategies, the nature of conflict needs to be thoroughly understood. This paper reviews traditional conflict models showing how these models may be integrated into a more unified model based on computational geometry. This mathematical approach is being investigated for the specification and management of future airspace, achieving a more solid architectural basis for airspace design. This approach has the potential to significantly reduce the subjectivity when attempting to model controller and pilot workload, an important requirement in future designs.

An Euler correction method is developed for unsteady, transonic inviscid flows. The strategy of this method is to treat the flow-field behind the shock as rotational flow and elsewhere as irrotational flow. The solution for the irrotational flow is obtained by solving the unsteady full-potential equation using Jameson's rotated time-marching finite-difference scheme. Clebsch's representation of velocity is followed for rotational flow. In this representation the velocities are decomposed into a potential part and a rotational part written in terms of scalar functions. The potential part is computed from the unsteady full potential equation with appropriate modification based on Clebsch's representation of velocity. The rotational part is obtained analytically from the unsteady momentum equation written in terms of Clebsch variables. This method is applied to compute the unsteady flow-field characteristics for an oscillating NACA 64A010 aerofoil. The results of the present calculation are found to be in good agreement with both Euler solution and experimental results.

A new approach to deriving analytical approximations for the free modes of motion of an aircraft is presented. Based on an asymptotic analysis, it eliminates the need for a priori assumptions regarding the characteristic motion of each mode, and is thus particularly suitable for an introductory exposition. In its basic form, it yields expressions for natural frequencies, damping factors and time constants which agree, to leading order, with well established results. At a more advanced level, it allows us to assess the validity of these results. In particular, we find that the two degree-of-freedom approximations to the short period oscillation and Dutch roll are asymptotically incorrect. This is unlikely to have a significant effect on the accuracy of the former, but is the reason for the poor damping predictions of the latter.

A comparison has been made between the composite beam designs produced by minimum mass optimisation using two different sets of constraints. The first approach constrained the design to have a given separation between fundamental bending and fundamental torsional natural frequencies; the second constrained the design to have a given flutter and divergence speed. The beams are modelled as a series of elements, stepped in thickness at discrete nodes, with the Dynamic Stiffness Method being used for calculation of their natural frequencies. The aeroelastic constraints are obtained from the Fortran program CALFUN. The results show that for similar flutter and divergence speeds, the optima produced using aeroelastic constraints have a slightly lower mass (up to 4% lower) and a less ‘hard’ flutter onset. However, the time taken to produce these optima is significantly longer (in excess of 2 orders of magnitude). A preliminary study discusses the merits of a combined optimisation method where frequency constrained optimisation is used to provide a near-optimum starting point for flutter and divergence constrained optimisation. In addition, a wind-tunnel model of one of the optima has been manufactured and subject to both modal analysis and wind-tunnel tests to validate the flutter speed calculations. This shows that when using strip theory, CALFUN predicts a conservative value of flutter speed for this design. Further investigation has shown CALFUN's lifting surface theory to be more accurate for low aspect ratio models.

The aerodynamic performance of supercritical aerofoils at transonic speeds is strongly influenced by the shock wave-boundary-layer interaction. Passive shock control is one of the techniques used for controlling the undesirable effects of strong shock wave-boundary-layer interaction leading to extensive separation. Using passive shock control, the stall margin is increased and the onset of buffeting is delayed. Passive shock control is modelled by introducing a closed plenum chamber underneath a perforated surface at the foot of the shock wave where a combination of blowing and suction is generated. As a result, a strong normal shock wave is changed into a series of weak shock waves with lambda shape. Since the Baldwin-Lomax turbulence model has been used extensively for passive shock control modelling, which exhibits poor predictability for separated flows, an attempt has been made to modify the Reynolds normal stresses for this model so as to improve the accuracy of numerical results for flows with separation. Further modification to the Baldwin-Lomax model has been employed so that the mass transpiration effects are taken into account for the passive shock control computations. In this paper, a brief description on an implicit finite-volume TVD scheme in general coordinates is given and the details of the Balwin-Lomax turbulence model and its modifications are presented. The validated numerical results for several RAE 2822 aerofoil problems plus corresponding results for the modelled methods are presented and compared with some experimental data and other numerical results.