The mathematical analysis of the induced velocity components of a screw propeller has occupied the attention of fluid dynamicists for many years. Early approaches to the problem concentrated mainly on momentum and blade element theories, neither of which are capable of providing a detailed knowledge of the flow field, except at the propeller plane or the boundary of the fluid. The early vortex theories also suffered from equally significant, but less severe, limitations and such methods were found to be completely unsatisfactory for many applications. In particular, the development of the ducted propeller for the propulsion of supertankers and VTOL aircraft has demanded a highly detailed knowledge of the flow field, especially around the propeller tip.

The elastic stress concentration factors for the torsion of solid and hollow shouldered shafts have been determined by means of a pure resistance electrical analogue. Fillet radii ranged from 0.05 to 1.0 times the diameter of the smaller shaft, and the shoulder diameter increased from 1.0 to 8.10 times the diameter of the smaller shaft. A comparison is made with the results of other techniques. A study has also been made of the formation of a plastic region in the neighbourhood of the fillet.

The effects of contraction geometry on non-isotropic free-stream turbulence were investigated experimentally. Eight nozzles of circular cross-section, having different contour shapes and various non-dimensional lengths, were tested. The contraction ratio was 10:1. The results are compared with test data for isotropic turbulence and with a well-known linear theory. It is found that the variation of the lateral component of turbulent energy along the nozzles is similar to that with isotropic free-stream turbulence, whereas the behaviour of the longitudinal component is entirely different. The change of turbulence depends on local contraction ratio only.

The influence of finite aspect ratio and yaw on the computed indicial response of a pitching wing has been studied using numerical solutions of the unsteady Euler equations. The indicial response was obtained directly from computations of the unsteady flow around two- and three-dimensional wings subjected to a step change in incidence at Mach numbers between 0·2 and 0·7. The data reveal several important characteristics in the behaviour of the unsteady response of three-dimensional wings. The initial response is shown to be independent of both aspect ratio and yaw confirming the results of linearized theory. During the subsequent development of the unsteady response significant differences are observed between the two- and three-dimensional behaviours as a consequence of changes to both wing aspect ratio and yaw angle. The formation and spanwise propagation of acoustic waves due to finite aspect ratio is shown to have a significant influence on the development of the unsteady forces, while for yawed wings the results indicate that the manner in which the windward and leeward tip vortices form is important. Based upon these observations it is suggested that the current practice within the rotorcraft community in which two-dimensional indicial response functions are employed may be unreliable for the advancing blade.

The aim of this work is to investigate how the wake vortex hazard generated by an aircraft can be reduced by modifying the wing lift distribution. The wake associated with a given lift distribution is simulated with a two-dimensional, in viscid ‘vortex method’. A numerical optimisation technique is used to guide the modifications so that a hazard measure, based on the rolling moment induced on a following aircraft encountering the wake, is minimised. The results show that a significant (~20–25%) reduction in hazard compared with conventional high-lift configurations can be achieved, via lift distributions that have a local minimum between the regions contributing to the flap and tip vortices. The counter-signed vorticity associated with this minimum appears to prevent the tip and flap vortices from merging, resulting in a safer wake. Furthermore, the hazard reduction is robust to variations in other features of the lift distribution and should thus be achievable in practice.

This paper presents a combined experimental and computational study of annular cavities on a semi-angle cone in a Mach 8·9 flow. A range of cavity length-to-depth ratios has been considered, and a parameter has been determined that distinguishes between ‘weak oscillations’ and ‘strong oscillations’ of the cavity flow. Essentially the work identifies the transition from the case where the flow can be regarded as ‘pure cavity flow’ to that where the flow behaviour is tending towards that of a ‘spiked blunt body’. The CFD simulations also suggest that, for a certain range of cavity scale, the limiting cavity flow state depends upon the flow initialisation process; it may be weak or strongly oscillating.

The 778th Lecture to be read before the Royal Aeronautical Society (the second main Society Lecture to be given at a Branch centre) was read under the auspices of the Portsmouth Branch, at the Portsmouth Municipal College, on 21st April 1949, by R. R. Duddy, B.Sc., A.F.R.Ae.S., on “ High Lift Devices and their Uses.” Sir John Buchanan, President-Elect of the Society, presided over the meeting with Mr. E. C. Green, Chairman of the Portsmouth Branch.

This work aims at improving the resilience and damage tolerant properties of CFRP by using cork, which is a natural material with good energy absorption capacity and thermal insulating and vibration damping characteristics. Two types of materials were considered: a sandwich formed by carbon-epoxy facesheets with a cork-epoxy core and a carbon-epoxy laminate with embedded cork granulates. The damage tolerant properties were evaluated by low velocity impact tests according to the type of material. Additionally, this work intends to evaluate the feasibility of using a cork agglomerate combined with CFRP in a sandwich configuration in order to improve the aeroelastic properties of certain types of aerospace components aiming at preventing the occurrence of damage due to flutter. A computational analysis was used to determine the critical flutter speed of a cork based sandwich plate and other conventional materials, such as aluminium alloy and CFRP.

Results are clear about the benefits of using cork based composites either by improving the damage tolerant properties under impact loading or by extending the flight envelope without weight penalty by increasing the flutter critical speed.

Aerodynamic properties of oblique wings have been studied intensively at NASA Ames Research Center and also by the Boeing Commercial Airplane Co. Figure 1 shows the design proposed by Boeing for a 200 passenger transport intended to fly in the transonic speed range; the design employs an oblique wing of high aspect ratio.

One feature of the oblique wing design that has not been fully documented is its aeroelastic stability. Since the oblique wing has one panel swept forward and the other swept back, it is perhaps natural to try to relate its behaviour to well known phenomena associated with conventional swept-forward or swept-back wings. This approach would lead one to expect aeroelastic divergence of the forward wing panel.

This paper reports on the experimental validation of a new model of slider-reefed ram-air parachute opening, using jump data collected by this investigator and others. The model is based on the parachute load equation of motion coupled with a new differential equation which describes the rate of change of the parachute's drag area. The model clearly identifies the important factors which determine the inflation peak load and opening time. It also features many scaling relationships useful for design work. Several predictions are shown to be design-independent. The experimental data used in this model validation were gathered during sport parachuting jumps performed by this author. Also used are data generated by the US Navy during tests of the MC-5, MT-1X/SL and MT-1XX parachutes. The experimental results and model predictions are found to agree within 20% accuracy over a wide range of opening speeds and deployment altitudes.

This article attempts to look forward in the field of aircraft structures, at what is likely to happen, and what current R&D is necessary to achieve this. It becomes clear that structural performance is always improving but that the main drivers are likely to be cost, both capital cost and in-service costs. The capital cost is likely to improve by reducing the design and development time as well as low-cost manufacturing. The use of all components of the synthetic environment are here playing an increasing role. The in-service costs will be reduced by more robust structures and better NDE to automate inspections and lengthen their intervals.

Flying locust swarms have already been found to provide particularly efficient three-dimensional targets for ultra-low-volume aircraft spraying. An exceptionally large proportion of the total insecticide applied can be picked up on the insects themselves, and kills exceeding one tonne of locusts per litre of insecticide have been assessed in the course of such operations. There is reason to believe that it was by aircraft spraying of swarms, often in flight, in Morocco during 1960, that locust control operations may for the first time have had a significant impact on the overall Desert Locust situation. Similar operations during 1968, in Ethiopia (with an outstanding Ethiopian senior pilot, Ato Abebe Wordofa) and again in Morocco, appear to have played a considerable part in suppressing the unusually short-lived recent upsurge of the Desert Locust, Schistocerca gregaria Forskal.

This work investigates the propeller’s influence on the stability of High Altitude Long Endurance aircraft, incorporating all resultant loads at the propeller hub, propeller slipstream, and gyroscopic loads. Such effects are usually neglected in the aeroelastic simulation of HALE aircraft. For that goal, a previously developed framework, which couples a geometrically nonlinear structural solver with an Unsteady Vortex Lattice method (uVLM) for lifting surfaces and a Viscous Vortex Particle (VVP) method for propeller slipstream, was employed to generate time-data series. Also, a method, based on a combination of Proper Orthogonal Decomposition and system identification, to extract dynamic information (frequencies, damping, and modes) of the aircraft from a time-series signal is proposed and successfully tested for a purely structural case, for which reference data is available. The method is then applied to investigate the stability of aeroelastic cases. The results demonstrate that the presence of propellers can influence the aeroelastic stability of a Very Flexible Aircraft.

At present, the lack of UAV regulations and standards precludes UAVs from being certified to operate commercially in un-segregated civilian airspace. Because of strategic, economical and security requirements, it is necessary to devise a method to operate UAVs in South African airspace within existing regulatory arrangements. This paper suggests specific UAV missions, viz; maritime patrol/boarder control, search and rescue, and cargo transport, together with design considerations and possible concepts of UAV; operations, maintenance and training, that will enable UAVs to satisfy the immediate South African strategic requirements whilst further UAV standards and regulations are being developed.

The Cooper-Harper scale is currently the only well-established scale for assessing aircraft handling qualities. However, as a result of having a unidimensional format the Cooper-Harper scale lacks diagnostic power and has also been criticised for exhibiting poor reliability. The Cranfield Aircraft Handling Qualities, Rating Scale (CAHQRS) is a new, multidimensional rating scale using concepts from two established scales, the NASA-TLX workload scale and the Cooper-Harper scale. This paper provides an overview of the development of the CAHQRS and the results from a series of validation trials in an engineering flight simulator. An in-flight refuelling task and an approach and landing task using a range of control laws were used in these evaluations. The results showed that the CAHQRS had high positive correlations with the Cooper-Harper scale. However, the CAHQRS also demonstrated greater validity, diagnostic power and higher test/re-test reliability than the previous scale.

This paper presents the development of visual oriented tools for the dynamic performance simulation of a turbojet engine using a cross-application approach. In particular, the study focuses on the feasibility of developing simulation models using different programming environments and linking them together using a popular spreadsheet program. As a result of this effort, a low fidelity cycle program has been created, capable of being integrated with other performance models. The amount of laboratory sessions required for student training during an educational procedure, for example for a course in gas turbine performance simulation, is greatly reduced due to the familiarity of most students with the spreadsheet software. The model results have been validated using commercially available gas turbine simulation software and experimental data from open literature. The most important finding of this study is the capability of the program to link to aircraft performance models and predict the transient working line of the engine for various initial conditions in order to dynamically simulate flight phases including take-off and landing.

The article includes study on the influence of a LEX (leading-edge extension) and wing tip plates on aerodynamic characteristics of the Rocket Plane in tailless configuration for manned suborbital flights. The research was conducted only for the low speed regime in the wind tunnel at the Warsaw University of Technology. Tests were carried out for a few configurations of the Rocket Plane. Moreover, two shapes of LEX were investigated. Analysis of results was focused on the aerodynamic synergism effect only. The influence of LEX and the wing tip plates of the Rocket Plane on the aerodynamic coefficients was identified.

Landing gear structure is developed predominantly using safe life design criteria. Health monitoring and structural prognosis techniques for landing gear cannot focus on crack detection; techniques for determining input loads and calculating damage or methods for directly measuring material damage must be employed. This paper will discuss Messier-Dowty’s research into structural monitoring over the past several years. Principally, direct damage detection systems and load monitoring systems will be discussed.

It was recently stated by Cockrell, Diamond and Jones(1) that attempts to correlate diffuser loss coefficients with the inlet boundary layer momentum thickness were generally unsatisfactory. In particular, it had proved impossible to align various results from diffuser tests which had been made with differing inlet flow conditions. The two methods of thickening the diffuser inlet boundary layer, using either

(a) a length of parallel pipe, or

(b) screen rings at inlet to the diffuser

led to a corresponding variation in diffuser performance.

The conclusion was drawn that “the manner by which an inlet boundary layer has been thickened is as significant in determining diffuser performance as is the thickness of the layer. No satisfactory inlet flow parameter is at present known”.

Two interesting flow phenomena have been observed during the course of some transition measurements carried out on a swept-back wing with a curved tip. Firstly, the influence of leading-edge sweep angle on the type of instability responsible for transition has resulted in two distinct types of transition occurring simultaneously over different portions of the wing under certain critical conditions. Secondly, unlimited spanwise turbulent contamination of the flow was observed with an excrescence located close to the leading edge. The circumstances in which this occurred are believed to be somewhat exceptional, although much further work is desirable on this point.