The high cost of new weapon systems and the loss of tactical capability when vehicles are out of operation for unscheduled repairs are forcing the military services to require a higher order of structural reliability. Fleets are being kept in operation for many years beyond the time originally anticipated during design, resulting in many cases, in the need for costly structural repairs and modification to cure fatigue problems. Consequently, new weapon system procurement contracts are being written with a “fatigue-life” guarantee as a contractual requirement. This situation calls for careful attention to details during the design phase. More testing, both exploratory to aid in detail design decisions, and confirmatory to validate the design and demonstrate compliance with the contractual requirements, is required. Better test methods and more meaningful test results are demanded from the test laboratory. Methods for more accurate predictions of the loads experience during the entire service usage are required of the structural analysts.

For the past half-century the tank has dominated the land battle by virtue of its armour.

During the last war, the discovery of the shaped high explosive charge (or hollow charge) was the first significant step towards its decline. This type of warhead could penetrate the thickest armour then in use, without the need for its carrier to have any significant velocity. No longer were projectiles of high kinetic energy, and therefore high velocity, required.

Recent developments in the design of rigid airships, as commercial air liners in England and Germany, and for military purposes in America, show a demand for greater lifting capacity, cruising range and speed. The increase in size is mainly responsible for radical changes in the structural arrangement of the transverse frames, introduced by the designers of the British airships, R.100 and R.101.

The small deflection/initial buckling behaviour of elastic, homogeneous plates is characterised by the absence of coupling between in-plane and out-of-plane quantities, i.e. stress couples, shear strains etc. By contrast, heterogeneous plates, of which generally laminated plates are an example, exhibit ‘shell-type’ behaviour in as much as in-plane and out-of-plane quantities are coupled. Reissner and Stavsky were the first to correctly formulate the field equations for such plates. Since that time a large number of papers on the influence of coupling on the behaviour of many different types of laminated structural elements, such as beams, plates and shells have appeared in the literature. However, it appears that until quite recently, the analysis of these structural elements in the presence of a general (Winkler/Pasternak) elastic foundation has not been undertaken.

This paper investigates the feasibility of improving the aircraft landing performance by design the damping orifice parameters of the landing gear using lattice Boltzmann method coupled with the response surface method. The LBM is utilised to simulate characteristics of the damping orifice after model validation. The numerical model of the landing gear using simulated damping force is validated by single landing gear drop test. Based on the numerical model and the response surface functions, the sensitivity analysis and the optimisation design are performed. The maximum error of mean velocity simulated using LBM with experimental data is 7.07% for sharp-edged orifices. Moreover, the numerical model predicts the landing responses adequately, the maximum error with drop test data is 2.51%. The max overloading of the aircraft decreases by 5.44% after optimisation, which proves that this method is feasible to design the damping orifice for good landing performance.

The dynamic analysis of heated structures is of considerable importance. Significant heating of a flight vehicle may take place at high speed causing reduction in its structural stiffness and vibration frequencies. Such changes in frequencies and mode shapes can substantially affect various static and dynamic aeroelastic instabilities.

In general, availability of a similarity law simplifies the solution of a problem. The following presentation studies similarity relations existing between an unheated vibrating cylinder and one with temperature gradient across its thickness.

This paper describes a preliminary investigation of the torsional stress concentration factors for circular shafts containing grooves determined using an analogue computer. The range covered by this analysis is for grooves which increase in depth from a minimum of 0·05 of the diameter of the shaft, with radii which vary from 0·5 to 0·05 of the diameter at the minimum section. Results are presented in the form of a data sheet, and a comparison is made with the approximate expression of Neuber. An investigation is also made of the modifications to the stress concentration factor if the flank is not perpendicular to the centre-line of the shaft.

The Gliding and Soaring Flight movement is as old as History. The observation of bird flight must have shown the men of former centuries in the same way as our own generation, that apart from power flight with wing beats there must be another flight possibility, enabling the use of the energy in the movement of air masses for flight without the expenditure of other power. The experiments undertaken in these times on the solution of the flight problem have come down to us only through myths and sagas, and we cannot differentiate between truth and imagination in these stories.

Experimental research, which can certainly be considered as the foundation of modern physics, has also in the realm of aerodynamics laid the basis for modernaeronautics. In this gliding and soaring flight plays the rôle of full–scale experiments, not as an end in itself, but as a proving-ground and last station before the invention of power flight.

Submerged intakes are widely used on aircraft as a means of supplying internal flow systems with ambient air. It is the purpose of this note to show by analysis of existing experimental data that the boundary layer at the location of the submerged intake can have an appreciable effect on its performance.

Information here relates to the NACA type of divergent submerged intake with a ramp angle, a, of 7° and an aspect ratio, w/d, of 4 because this particular combination of planform and geometry is now almost universally used.

The developments in the use of composite honeycomb in passenger aircraft structures has been growing rapidly over the past ten years. Starting with its use in the semi-structural internal use as a flooring material such as the cross plied UD glass-nomex cored floors of the wide body jet aircraft — 747 — L1011 and DC10, to the external uses for control surfaces, fins, undercarriage doors, engine pods, etc, and the ultimate all-composite fuselage of the LearFan project.

The progress in the light aircraft field by comparison, is almost non-existent, the major use of composites is restricted almost entirely to the manufacture of sailplanes and the majority of these use foam stabilisation rather than honeycomb.

Classification of the winged aircraft according to the character of wing (blade) motion in horizontal and vertical plane is presented. Design of a rotor, the blades of which are driven into rotation via flapping motion similar to the movement of an ornithopter's wing is proposed and the principle of operation is considered. Mathematical model of the aerodynamics of the autorotating rotor with flapping blades in hover is made on the base of the helicopter rotor blade-element theory. Geometric and kinematic parameters influence on the rotor lift and efficiency is analysed. It is shown that in hover the efficiency of an autorotating rotor with flapping blades is approximately equal to the one of a helicopter rotor.

The results of an experimental evaluation of three assessment criteria for boundary layer two-dimensionality are presented. The criteria include the so-called ‘two pin test', the momentum balance principle and the cross-stream variation in local skin friction coefficient. Extensive spanwise measurements in the flows investigated highlight the relative merits and limitations of the criteria imposed.

The momentum balance method is found to be the most informative technique, with the proviso that the test data must be interpreted with some care if measurements are restricted along a single streamwise axis.

The two pin test is found to provide a worthwhile complimentary addition to momentum balance data, whereas the spanwise variation in local skin friction coefficient is less conclusive as regards flow two-dimensionality.

Excepting the case of adverse pressure gradient flows, the momentum balance equation is seen as a viable experimental means of estimating the local skin friction coefficient in boundary layers where measurement is problematical, as in the case of transitional boundary layers. In such cases, the two pin test could be used as the sole means of confirming the flow two-dimensionality.

This paper reviews some of the work performed on the ground effects rig at BAE Systems in Warton, the now unique facility for modelling dynamic vertical landings and measuring hot gas ingestion. The paper discusses the flow diagnostic tools which have been used in recent times, up to the complexity of 3D PIV, and uses examples from the F-35 JSF programme to illustrate these. The paper hopefully demonstrates the difficulties of using these tools, as well as the benefits they can bring to a development programme.

The ground effects rig is a facility designed to measure temperature rise in aircraft intakes during vertical manoeuvres close to the ground. It is a complex facility that comes as close as possible to accurately modelling the flowfields around an aircraft moving both vertically and horizontally near the ground, with the ability to model dynamic pitch and roll at the same time.

Standard instrumentation for the models consists of rapid response thermocouples mounted in a rake at the engine face. 45 thermocouples of 0·05mm diameter with a time constant of about 10ms are used.

Although, with its standard instrumentation, the rig can measure how much hot gas gets to the engine face, it doesn’t show how it got there, or where it came from, which is the knowledge required to improve the design. Hence there is a need for flow diagnostics.

To support a seamless transition between safety net layers in air traffic management, this article examines an extra capacity in the generation of the resolution trajectories, conditioned by future high dense, complex surrounding air traffic scenarios. The aerial ecosystem framework consists of a set of aircraft services inside a digitalised airspace volume, in which amended trajectories could induce a set of safety events such as an induced collision. Those aircraft services strive to the formation of a cost-efficient airborne separation management by exploring the preferred resolutions and actively interacting with each other. This study focuses on the dynamic analysis of a decreasing rate in the number of available resolutions, as well as the ecosystem deadlock event from the identified spatiotemporal interdependencies among the ecosystem aircraft at the separation management level. A deadlock event is characterised by a time instant at which an induced collision could emerge as an effect of an ecosystem aircraft trajectory amendment. Through simulations of two generated ecosystems, extracted from a real traffic scenario, the paper illustrates the relevant properties inside the structure of the ecosystem interdependencies, demonstrates and discusses an available time capacity for the resolution process of the aerial ecosystem.

In this paper an attempt is made to outline the hazards which can arise, with particular reference to light aircraft, due to static electricity. Accidents, some of which are described in detail later, can and do happen, yet the precautions which should be taken to reduce the dangers are very easy to carry out. These precautions are detailed in the final section of this paper and it cannot be over emphasised that the habitual use of these simple techniques could well prevent a fire from being started with the resultant loss of an aircraft and the possibility of injury or death from such a fire.

The concept of “mechanical impedance,” a quantity equivalent to Biot's Dynamic Modulus (reference i), has been utilised since 1939 by the de Havilland Aircraft Company as a standard method of treatment of vibration problems inengine airscrew systems, the method being applied principally to torsionalvibrations. In this work the effect of damping forces was neglected, on theassumption that the resonant frequencies of a system are not affected appreciablyby such forces so long as they remain of small magnitude.

The desire to justify this assumption by theoretical reasoning, and to evolve a method of attack for problems in which the damping forces are too large to be neglected, led to the application of the concept of mechanical impedance to damped systems.