In this paper we present a Bayesian belief network (BBN) sociotechnical model for investigating the accident rate for multi-crew civil airline aircraft. The model emphasises the influence of airline policy and societal behaviour patterns on the pilots within the piloting system. The main claim of this paper is that a BBN can be used to bring most aviation safety-critical elements into a common quantitative safety assessment despite the unique problems posed by the very low probability of accidents. We support this claim by replicating certain phenomena such as the low accident rate, the difference between the ‘more’ and ‘less’ safe airlines and other statistical factors of civil aviation. In particular, the model succeeds in explaining the large gap of six to seven orders of magnitude between in-flight measurements of pilots’ error and accident rate.

It is considered that the blended wing body may offer the possibility of improvements in performance efficiency over the conventional civil transport. Such configurations will require transonic wind tunnel testing. Hence, a feasibility study has been carried out at ARA to investigate possible model support systems that could be used for this purpose. The study addressed issues arising from the mechanical design of two support systems; namely, a blade or Z-sting and a standard rear sting. In particular, the relatively restricted space available within the model fuselage has presented challenges in the design of the layout of the balance and instrumentation required for the model. CFD analysis has been carried out to assess the relative interference effects of the two support arrangements. This initial work has shown unexpectedly significant interference effects associated with the Z-sting support and attention is drawn to the need for further design work to minimise these effects.

The development of the non-linear equations of motion for the hang glider from first principles is described, including the complex geometry of control by pilot ‘weight shift’. By making appropriate assumptions the linearised small perturbation equations are derived for the purposes of stability and control analysis. The mathematical development shows that control is effected not by pilot weight shift, but by centre of gravity shift and that lateral-directional control by this means is weak, and is accompanied by significant instantaneous adverse response.

The development of a comprehensive semi-empirical mathematical model of the flexible wing aerodynamics is described. In particular, the modelling attempts to quantify camber and twist dependencies. The performance of the model is shown to compare satisfactorily with measured hang glider wing data obtained in earlier full scale experiments. The mathematical aerodynamic model is then used to estimate the hang glider stability and control derivatives over the speed envelope for substitution into the linearised equations of motion.

Solution of the equations of motion is illustrated and the flight dynamics of the typical hang glider are described. In particular, the dynamic stability properties are very similar to those of a conventional aeroplane, but the predicted lateral directional stability margins are significantly larger. The depth of mathematical modelling employed enables the differences to be explained satisfactorily. The unique control properties of the hang glider are described in some detail. Pitch and roll control of the hang glider is an aerodynamic phenomenon and results from the pilot adjusting his position relative to the wing in order to generate out of trim aerodynamic control moments about the centre of gravity. Maximum control moments are limited by hang glider geometry which is dependent on the length of the pilot‘s arm. The pilot does not generate control moments directly by shifting his weight relative to the wing. The modelling thus described would seem to give a plausible description of the flight dynamics of the hang glider.

This paper shows the theoretical development and application of dynamic gain scheduled control – a novel method for the control of nonlinear systems – to an aircraft model. The idea behind this method is to schedule the control law gains with a fast varying state variable rather than with a slow varying state or an input parameter. This is advantageous as it is then possible to schedule the gains with a state variable that is dominant in the mode that we are most interested in controlling. The use of this type of gain scheduling is shown to improve the transient response of the aircraft model when stepping between trim conditions and to overcome some of the problems associated with conventional gain scheduled controllers (such as control surface position limit saturation). ‘Hidden coupling terms’ that introduce unwanted dynamics when scheduling gains with a fast state (rather than the input design parameter) are eliminated directly by applying a transformation to the classical parameter-scheduled gain distributions which are calculated using eigenstructure assignment. A second order longitudinal model and a 5th order longitudinal/lateral model of the ICE 101-TV tailless delta-wing aircraft configuration are used to demonstrate the design process.

Typically, aircraft wing structural panels are designed against buckling for a very large number of possible loadings that may occur during the operation of the aircraft. If the optimisation procedure accounts only for a limited number of design loads, the structure may be vulnerable to a specific type of loading that may cause the structure to fail. A novel approach for the optimisation of ribs or plates of arbitrary shapes under uncertain loads is proposed. The geometry of the rib is defined by a single closed spline or several connected splines. The loading distribution is not considered to be uniform but it is allowed to vary within an admissible set, conferring uncertainty to the applied loads. The admissible load space comprises distributed normal and shear loadings that can be represented through a collection of piecewise linear functions defined along the plate boundary. A special procedure is applied to handle the constraint that the loading must be self equilibrating. A minimax strategy is used to deal with the loading variability such that the resulting optimal design is able to withstand an entire class of linear piecewise loadings along the rib boundary. The refinement of the loading representation may be completely independent of the refinement of finite element mesh. The validity of the proposed approach is assessed by applying it to an aeronautical wing rib.

The aim of this paper is analyse the practicality or otherwise of solar-powered propulsion (after launch using conventional chemical rocketry) for a space vehicle’s late pre-orbital trajectory phase, for orbital transfer and for post-orbital flight. We introduce a ‘concept’ vehicle that in principle permits the use of solar-powered propulsion in each of these stages. Some of the technical challenges that such a vehicle might face are analysed, including the problem of how to keep a large ultra-low mass optical concentrator arrangement sufficiently accurately positioned in different parts of such a trajectory.

It is argued that acoustic resonance phenomena in open cavities such as weapons bays cannot be adequately predicted through numerical solution of Reynolds averaged Navier-Stokes (RANS) equations. The requirement to resolve the growth of the shear layer instability from the lip of the cavity inevitably implies that turbulence further downstream is resolved while also being modelled thus making RANS over dissipative. Large eddy simulation (LES) models only unresolved scales and a hybrid method combining RANS near walls with LES in the cavity appears a practical alternative to pure RANS. This paper compares computations of the M219 cavity configuration made with unsteady RANS and with the hybrid method known as detached eddy simulation (DES). It is shown that whilst unsteady RANS and DES give very similar predictions for the 1st and 3rd modes of the acoustic resonance the 2nd mode (which is dominant near the centre of the cavity) is absent in the RANS results but well predicted by DES. The 2nd mode is thought to arise from an interaction with vortical structures in the shear layer which are suppressed in the highly dissipative RANS method. The 4th mode, which is much weaker than the other three modes, is over-predicted by DES and under-predicted by a smaller amount in RANS.

After identifying the ecological and economic drivers for use of laminar flow technology, we outline the mechanisms of laminarturbulent boundary layer transition and review the status of natural laminar flow (NLF) and hybrid laminar flow control (HLFC). New ways to reduce the complexity of HLFC systems are presented, and the remaining steps to achieve technology readiness are discussed.