The feasibility of using neutrally-buoyant (or fully-buoyant) airships for passenger and cargo transportation is investigated. The drag coefficients of rigid and non-rigid airships are deduced from flight data. Comparisons are made with empirical drag formulas and previous wind tunnel data. Some general trends for airship drag are derived. The mass breakdown of non-rigid airships with hull volumes up to 35,000m3 is analysed using parametric equations. The maximum feasible airspeed and useful load carrying capacity of projected airships are calculated. ‘Specific productivity’ is found to be lower than values achievable with fixed-wing aircraft, but ‘fuel-specific productivity’ is found to be competitive, confirming results of a previous NASA study. The use of gaseous hydrogen and fuel cells is briefly discussed.

The purpose of this paper is to present a new approach in the concept and implementation of autonomy for autonomous spacecraft. The one true ‘artificial agent’ approach to autonomy requires the spacecraft to interact in a direct manner with the environment through the use of sensors and actuators. Rather than using complex world models, the spacecraft is allowed to exploit the dynamics of its environment for cues as to appropriate actions to take to achieve its mission goals. The particular artificial agent implementation used here has been inspired by studies of biological systems. The so-called ‘cue-deficit’ action selection algorithm considers the spacecraft to be a non-linear dynamical system with a number of observable states. Using optimal control theory a set of rules is derived which determine which of a finite repertoire of behaviours the spacecraft will perform. A simple model of a single imaging spacecraft in low polar Earth orbit is used to demonstrate the algorithm.

The free flexural vibrations of rectangular plates with various boundary conditions have been considered by Warburton. The natural frequencies were calculated by the Rayleigh method, the mode assumed being the product of the characteristic beam functions for the given boundary conditions. Comparison with experimental results shows that the method gives reasonably good approximations. The present note describes a method of obtaining the approximately equivalent characteristic beam functions to enable Warburton's method to be extended to plates having one or more stiffeners parallel to an edge. As a numerical example expressions for the frequencies are derived for a plate, simply supported along two opposite edges, and having a central stiffener parallel to the other two free edges. The results are compared with those given in a recent note by Kirk, who solved the same problem by the Rayleigh-Ritz method, using a mode with one arbitrary parameter. In the case of the fundamental frequency of the unstiffened plate, the characteristic beam function in a direction perpendicular to the free edges is simply a constant, and the solution is less accurate than that given by the Rayleigh-Ritz method. However, numerical analysis of a square plate shows that above a certain stiffener depth the characteristic beam function method is more accurate than the Rayleigh-Ritz method. The two methods are also compared for the 2/2 mode.

A simple matrix method is presented for the deflection and stress analysis of cylindrical shell structures of arbitrary cross section stiffened by flexible frames. The method is an extension to fuselage structures of the Matrix Force Method developed by Argyris, in which the internal load system in the structure consists of two parts:—(a) synthetic load distribution, represented by the matrix b0, satisfying the external and internal equations of equilibrium, and (b) self-equilibrating load systems, represented by the matrix b1, which are introduced to satisfy compatibility conditions. The magnitudes of these self-equilibrating load systems are determined from the generalised compatibility equations formulated using the flexibility matrix f for the un-assembled elements of the structure. The self-equilibrating systems are non-orthogonal, but are arranged in such a way that the mixing between one system and another is kept to a minimum and, consequently, the resulting compatibility equations are well-conditioned. The three basic matrices, b0, b1; and f, are compiled using only very simple formulae. The matrices b0 and b1 depend on the geometry of the structure, while the flexibility matrix f is a function of geometry and elastic properties. The present analysis is applied to cut-out problems in fuselage structures. It can also be used for problems involving thermal loading and diffusion of loads in curved panels stiffened by flexible frames.

This paper proposes an online entry trajectory planning based on predictor corrector algorithm that satisfies terminal constraints, path constraints and geographic constraints for lifting-body entry vehicles. The vehicle is considered as a 3DOF point mass. A piecewise linear bank profile in the altitude-versus-velocity (H-V) plane is used to project the longitudinal trajectory and a heading angle corridor-based bank angle reversal logic is designed to satisfy the geographic constraints simultaneously. The algorithm in longitudinal plane solves the problem of the mismatch between terminal range and height and the algorithm in lateral plane satisfies the no-fly zone constraint. Simulation results with the CAV-H model show that the proposed algorithm can generate entry trajectories satisfying multiple constraints and has certain robustness.

The notched fatigue strength of the aluminium alloy HE 15, under stress conditions similar to those occurring in aircraft structures, is greater when the material is naturally aged than when it is fully heat-treated. This is attributed to the lower proof stress of the naturally aged material, which enables the high stresses in regions of stress concentration to relax more readily. However, no further improvement was obtained by re-solution-treating the alloy to reduce the proof stress further.

An experimental study of the supersonic vortices from a 75° swept-back delta wing has been carried out in a Mach 2.49 stream. Five-hole conical probe surveys were conducted at the trailing edge of the planform for 7° and 12° angles-of-attack. The main objective was to determine the Mach number and pressure distributions in the primary vortex. A novel approach of utilising a computational flow solver was used to generate the calibration data for the five-hole probe over a range of Mach numbers and pitch angles. Measurements indicate significant static and total pressure deficits in the vortex core. Both the magnitude and the spatial scale of these deficits increase with the higher incidence angle. The swirl profiles have supersonic peak magnitudes and resemble the low speed Lamb-Oseen vortex. Similar to the case of supersonic wing tip vortices, and contrary to the experimental results from transonic and low speed leading-edge vortices, the axial Mach number distribution in the vortex core is found to have strong wake-like profile.

A simple analysis is presented for the air flow and nozzle power requirements of hovercraft fitted with skirts on which the peripheral jet is blown down the inner skirt face—the “single-wall” type. The theory, which utilises experimental wall-jet data, is applicable to the equilibrium jet state.

A comparison is made with analyses for the air flow and nozzle power requirements of plenum chamber craft and hovercraft fitted with twin-wall skirts. It is concluded that, for a given gap between the skirt bottom and the terrain, at normal operating conditions the order of merit is twin-wall skirt, single-wall skirt, plenum chamber.

This paper presents a mathematical approach for the simulation of rotor-fuselage aerodynamic interaction in helicopter aeroelasticity and flight dynamics applications. A Lagrangian method is utilised for the numerical analysis of rotating blades with nonuniform structural properties. A matrix/vector-based formulation is developed for the treatment of elastic blade kinematics in the time-domain. The combined method is coupled with a finite-state induced flow model, an unsteady blade element aerodynamics model, and a dynamic wake distortion model. A three-dimensional, steady-state, potential flow, source-panel method is employed for the prediction of induced flow perturbations in the vicinity of the fuselage due to its presence in the free-stream and within the rotor wake. The combined rotor-fuselage model is implemented in a nonlinear flight dynamics simulation code. The integrated approach is deployed to investigate the effects of rotor-fuselage aerodynamic interaction on trim performance, stability and control derivatives, oscillatory structural blade loads, and nonlinear control response for a hingeless rotor helicopter modelled after the Eurocopter Bo105. Good agreement is shown between flow-field predictions and experimental measurements for a scaled-down isolated fuselage model. The proposed numerical approach is shown to be suitable for real-time flight dynamics applications with simultaneous prediction of structural blade loads, including the effects of rotor-fuselage aerodynamic interaction.

Airbus and Boeing are cooperatively presenting this topic dealing with transport aircraft stalls. The paper will begin by defining a stall, followed by a review of requirements, predictive validation and flight testing. There are various ways of designing modern jet transports for the stall regime such as aerodynamic approaches, flight deck indications, and augmentation control laws to deal with the high angle-of-attack (α) arena. The goal of augmented control laws for high α is common – no full aerodynamic stall or loss of climb performance should occur in the operational flight envelope, in Normal flight control modes. The validation techniques employed in preparation for a flight test campaign will follow. These include flight characteristic predictions based on wind-tunnel data as well as pilot-in-the-loop simulation rehearsals. The preparation for flight testing will be reviewed from both the engineer and pilot viewpoints. This will be followed by a review of various flight testing that has been conducted. The paper will close with a brief foray into what the future of transport stalls could be – perhaps protection features in degraded flight control modes? What are the benefits as well as drawbacks to increased augmentation for high α?

The effort required to produce very accurate supersonic nozzles has suggested the need for criteria from which the order of accuracy required for quantitative experiments can be deduced. The purpose of this note is to indicate a way of obtaining such criteria for measurements of aerodynamic forces, but also to point out that “ sufficiently accurate ” nozzles for such measurements are indeed very difficult to produce and to suggest that a remedy might first be sought in interference corrections.

This paper relates the advantages of centrifugal, mechanically-driven fuel pumps and quotes their ability to operate with hot contaminated fuel. It also shows the substantial weight saving when compared with positive displacement pumps. The poor part load efficiency of the conventional centrifugal pump at its design speed, giving considerable temperature rise in the fuel, has resulted in the development of the vapour core principle where flow regulation is effected by a throttle at the eye of the impeller.

Reference is made to the associated control and distribution equipment which, although not peculiar to the vapour core pump must be made compatible with a pump having an inherent pressure-raising capability which decreases with engine speed. The inlet throttle feature permits adequate control of the temperature rise to be maintained over the whole working range of the gas-turbine fuel systems.

The fundamentals of the pump are explained and the development progress reviewed for application to main and reheat fuel systems. Reference is also made to control methods that are being currently developed for combined engine and reheat systems supplied from a common pump.

The spill nozzle, which was developed specifically for use with hot contaminated fuel, possesses satisfactory characteristics for use with the vapour core pump. The temperature rise data associated with combination of vapour core pump and spill nozzle are quoted, and temperature rise data are also given where the pump is used either for reheat supply or for both combined reheat and main engine fuel systems.

Alec Young spent over 30 years in academic life. He has been active, not only in nurturing the teaching of and research in aeronautical engineering, first in the Aerodynamics Department at Cranfield College of Aeronautics, and then in the Department of Aeronautical Engineering at Queen Mary College, but also in participating in wider academic developments as Vice Principal of Queen Mary College and as Senator of the University of London. Hence, it is appropriate that in such a tribute, there should be an article on an academic topic. A review of undergraduate aeronautical engineering education, its past, present, and future, has been chosen. Such a review is timely as a contribution to the current debate on engineering education in general, initiated by the newly formed Engineering Council.

In recent years, there has been an increasing interest in the research and development of hybrid airships for various applications. Airship design involves multiple design parameters from various disciplines that interact mutually. Existing design methodologies, however, are often limited to fixed shapes and geometry. This paper provides a comprehensive parametric design approach for the sizing of multi-lobed hybrid air vehicles for low- and high-altitude applications. The proposed design techniques are robust so that the designer has the freedom to change the number of lobes, the relative location of lobes, the envelope profile, and the optimiser for the design optimisation process. The outcomes of the proposed methodology are envelope volume, wetted surface area, length and span of the envelope, sizing and layout of the solar array, and sizing and layout of the fins. The modeling techniques highlighted in this paper are very efficient for the design and optimisation of multi-lobed airships in the conceptual design phase with a large design exploration space. The robustness of the shape generation algorithms is tested on some of the standard envelope profiles of airships. The effect of the shape and geometry of the multi-lobed envelope on added mass is demonstrated through the added mass estimation using Boundary Element Method.

The aim of axiomatic aerodynamic modelling is introduced, namely to understand the validity of aerodynamic modelling in the context of aircraft dynamics with particular emphasis on understanding the relationship between full-scale flight behaviour as compared with that predicted from data based on wind tunnel tests.

The possible steady rates of roll of an aeroplane are determined in the case when inertia cross-coupling is present. This phenomenon not only changes the simple linear relationship between aileron angle and rate of roll, but may lead to more than one possible rate of roll for a given aileron angle. Simplified equations of motion are given for the cases in which the rolling takes place (a) from level flight, (b) during a pull-out manoeuvre. In both cases, these equations, which are non-linear, are solved numerically for typical examples. The static stability of the possible steady motions is considered in detail, and the dynamic stability is determined in the numerical examples.

The object of the present paper is to draw attention to some of the recent researches which have had as object the improvement of the aerodynamic characteristics of aircraft. Such characteristics can be classified into two groups; those concerned with performance and those concerned with stability and control. In the former group come all those researches which aim at the reduction of drag, while in the latter group come those directed to the attainment of satisfactory stability and control in normal flight, as well as those concerned with the behaviour of auxiliary devices such as flaps and slots which are used under special conditions and in particular during landing and taking-off. The problems associated with flutter also belong to this group. The two groups may be broadly characterised by the words economy and safety.