bluuebunny/crossref_metadata_2025 huggingface dataset:
The asymptotic structure of the turbulent attachment-line boundary layer
Authors: van Oudheusden B. W.
Published: July 2022

The method of matched asymptotic expansions has been applied to analyse the asymptotic structure of the incompressible turbulent attachment-line boundary layer at large Reynolds numbers. Inner and outer solutions were obtained that give the ‘wall-unit’ and ‘velocity-defect’ represention of both the spanwise and chordwise velocity profiles. The predictions from the theory agree with experimental and DNS data in the range of fully developed turbulence.
Aerofoil at low speeds with Gurney flaps
Authors: Brown L. , Filippone A.
Published: July 2022

This paper reviews the research on Gurney flaps and related high lift trailing edge devices. It investigates aerofoil performances at Reynolds numbers Re ≅ 105 and below, both with the clean configuration and various Gurney flap sizes. The device height is optimised, and a semi-empirical formula linking flap height to free stream speed and aerofoil chord is proposed. The analysis shows that the optimal size of the device is always below the boundary-layer thickness at the trailing edge. Discussion of results includes analysis of hysteresis loops occurring in the L/D performances. These are mostly due to large changes in drag and small changes in lift, which occur when the aerofoil is restored to the reference angle of attack.
A numerical study of drag reduction by mini-belts in a smooth wall turbulent boundary layer
Authors: Djenidi L. , Antonia R. A. , Savill A. M.
Published: July 2022

A numerical study of drag reduction by mini-belts in a smooth wall turbulent boundary layer is carried using a second-moment closure turbulence model. The main objective of this exploratory work is to investigate the possibility of using mini-belts, driven by frictional drag only, to reduce the drag of a smooth wall. The results clearly show that such technique can be an effective and cheap means for achieving drag reduction. Furthermore, it is observed that, in contrast to riblets, the use of mini-belts does not suffer from geometrical or size constraints in the context of drag reduction. Also mini-belts will always reduce the skin friction regardless of the flow regime (laminar, transitional and turbulent). These advantages may quite well balance the major difficulty related to their mounting in practical situations
The effects of apex flap on the leading-edge vortex breakdown of a cropped double delta wing
Authors: Wang J. J. , Liu J. Y. , Li Q. S.
Published: July 2022

The dye-injection flow visualisation technique was used to investigate the effect of the apex flap on the leading-edge vortex breakdown over a cropped 76°/40° double delta wing. The angle-of-attack of the experimental model varied from 20° to 40°, and the length of the apex flap was 25%c and 50%c respectively. By changing the angle of the apex flap, we found that the apex flap is an efficient method to control the leading-edge vortex breakdown, and that there exists an angle of the apex flap at which the value of the leading-edge vortex breakdown delay reaches maximum. Moreover, it is found that, for α < 28°, the small apex flap is a better choice for delaying the vortex breakdown; for α > 28°, the large apex flap is superior to the small one.
Time-linearised transonic computations including entropy, vorticity and shock wave motion effects
Authors: Ly E. , Nakamichi J.
Published: July 2022

The effect of small perturbations on steady nonlinear transonic small disturbance flowfields, in the context of two-dimensional flows governed by the general-frequency transonic small disturbance equation with nonreflecting far-field boundary conditions, is investigated. This paper presents a time-linearised time-domain solution method that includes effects due to the shock-generated entropy and vorticity and shock wave motions. The solution procedure correctly accounts for the small-amplitude shock wave motion due to small unsteady changes in the aerofoil boundary conditions, and correctly models a flowfield with embedded strong shock waves. Steady and first harmonic pressure distributions for the NACA 0003 aerofoil with a harmonically oscillating flap, and NACA 0012 aerofoil undergoing a sinusoidal pitching oscillation, are predicted and compared with the Euler results.
Systems and avionics
Authors: Collins P. H. , Perry B. L.
Published: July 2022

This paper looks to future developments and concepts in Systems and Avionics. One hundred years ago neither ‘avionics’ nor even ‘systems’ would have been recognised as having a place in aeronautics. The concept of aircraft systems developed, as the complexity of each element of the aircraft grew, requiring specialism in the design, operation and maintenance of those elements. Early examples would have been the propulsion and flying controls systems. By the 1930s passenger aircraft might have carried, in addition to the pilots, a navigator, flight engineer and radio operator, each responsible for his own collection of systems, with the aircraft itself probably having an embryonic electrical system.
The human–machine partnership in UCAV operations
Authors: White A. D.
Published: July 2022

At a time when a great deal of research on UCAVs is aimed at maximising their autonomy it should not be forgotten that human operators will, ultimately, remain ‘in control’ to some degree. The decision-sharing relationship between the operator and the UCAV depends on political constraints as well as the intelligence of the UCAV system. This in turn dictates the amount and type of information to be exchanged and the way in which it is communicated with the operator.

Operational flexibility is a key military driver and in order to achieve it, a variable autonomy command interface, combined with information fusion and intelligent decision-support systems, will be required. To be effective the operator will need to work in concert with the UCAV system rather than act simply as a command source and an information sink. The implications of this ‘partnership’ for command and monitoring requirements and in particular for weapons release authorisation, are discussed in this paper.
Predicting impact damage of composite stiffened panels
Authors: Davies G. A. O. , Zhang X.
Published: July 2022

This paper addresses the problem of the complex nature of low velocity impact damage in fabricated structures made of laminated carbon-epoxy composites. The structures chosen are stiffened compression panels since these are the most vulnerable to delamination and debonding. Four ‘top-hat’ stiffened panels were tested and predicted using a dynamic finite element code. The panels all had considerable postbuckling strength so the impact sites were carefully chosen to inflict maximum loss of strength. It was shown that the threshold energy for onset of delamination can be predicted using a dynamic finite element code. The amount of delamination or debonding is also predicted using a crude strength-based criterion, which seems to work only because the maximum impact force is a transient phenomenon of short duration.
Planning for super safety: the fail-safe dimension
Authors: Howard R. W.
Published: July 2022

It has long been a requirement in air transport that no single failure can have a catastrophic effect. As nothing can ever be failure free, fail-safety in design and operation must be provided in all respects.

This paper explores the design background, application and history of the concept of fail-safety in air transport and the vital role it plays in overall safety. It is suggested that fail-safety is the most important discipline of all those involved in safety in design and operations. Without it, the current air transport safety levels, even using the latest technologies, would not be possible.

In the modern air transport system, all accidents are due either to fail-safety implementations breaking down, or not having been adequately provided, or due to extremely remote multiple coincident failures. It can be argued that inadequacies in fail-safety provisions at the very low target failure rates now demanded, is the main reason for the near constancy of the accident rate, and the consequent increase in numbers of accidents as the world fleet grows. In the forefront of fail-safety problems is the inadequacy of its use in the management operations of crew in the modern air transport cockpit.
Civil helicopter operations with British Airways
Authors: Cameron J. A.
Published: July 2022

This paper is on the practical experience in British Airways on civil helicopters during the past 29 years, and my recommendation for the continued expansion and success in the vertical flight field of which the present day helicopter is the first example.

I still believe that open rotors, because of their low noise and low speed control aspects, will certainly have a future as far as we can see on short stage lengths up to the end of the century; and by short stage lengths I mean up to 4/500 miles.
The principles and practice of airworthiness control
Authors: Langford P. S.
Published: July 2022

When one is asked to present a paper in a series honouring a particular person from the past, it is always fascinating to review what is available in the way of background of his life and work. As have other Lawrence Hargrave lecturers before me, I have followed this course.

Hargrave's aeronautical work and the papers describing it show clearly the patience and logical thinking which motivated him in all he did. He was a prodigious recorder of data and kept all of this until the untimely death of his son during the first world war. Although of course the concept of airworthiness was unheard of when he was carrying out his experiments at Stanmore, airworthiness control today, some three quarters of a century later, depends almost entirely on the same processes—the proper and logical use of vast amounts of recorded data gathered from all parts of the world.
Jaguar—a collaborative military aircraft programme
Authors: Yates I. R.
Published: July 2022

The Jaguar programme resulted from a successful international collaboration in all the relevant disciplines between companies having very different backgrounds in the aviation field, namely British Aircraft Corporation and Breguet Aviation (since merged with Dassault) for the airframe and Rolls-Royce and Turbomeca for the engines. It also involved collaboration in depth between government officials having different civil service structures and national practices in the two countries. Before entering into a description of the various phases of the programme and some of the problems which were met and solved it is worth briefly reflecting on the background leading to the formal start of the project in May 1965.
Future system consideration for operations of aircraft in the terminal movement area
Authors: Howell G. C.
Published: July 2022

The operation of civil aircraft in the Terminal Movement Area is a very complex subject. Many disciplines are involved and, certainly in Europe, there are problems of international agreements on standards and procedures for the various airline operators, airport authorities and regulatory bodies. For this reason there has been a tendency for certain aspects of the Operational System to be studied and improved without fully evaluating the interactions and hence overall effectiveness of new technological developments.
Agricultural and special purpose aircraft—a manufacturer's viewpoint
Authors: Norman N. D.
Published: July 2022

Britten-Norman started out as converters of Tiger Moths for export to New Zealand as top-dressers. As new aircraft came into that particular scene (Cessna 180s) we turned our attention to spray equipment. As luck would have it during our researches into available ground spraying techniques, I ran into Edward Bals who had perfected some very simple rotating gauze atomisers to make possible ultra low volume spraying applications upon, for example, orchards.

Thanks to the efficiency of his rotary atomiser he was able to dispense with almost all the carrier liquid of which hundreds of gallons were used on each acre to secure proper coverage by substituting a mist of small uniform sized droplets carried in a dratt (not a blast) of air.
Defence and industry—where now ?
Authors: Rosier Frederick
Published: July 2022

This paper can be divided into four parts; firstly, a tribute to R. K. Pierson, then a brief historical survey of events that have affected the RAF and industry, leading up to where we stand today; and finally, some thoughts on the future based on the twin aims—which I am certain you will endorse—of maintaining a healthy and viable aircraft industry in the United Kingdom, and of satisfying the future needs of the Royal Air Force at the lowest possible cost. I am going to concentrate on the military side.
Hawker Siddeley Hawk TMk 1 two-seat ground attack/trainer aircraft
Authors: Simpson D. M. S.
Published: July 2022

A paper was read to the Test Pilots’ Group of the Royal Aeronautical Society in 1974 some months before the first Hawk flew in August of that year. On that occasion the paper consisted of some background information on how the aircraft came about, followed by a technical description and outline of the projected flight test programme. Now, some two years later, it is intended to describe the flight test programme in general terms from first flight up to the end of 1975. It is hoped that in due course some detailed aspects of this programme will be presented as a separate paper to the Test Pilots’ Group. Before starting on the flight test programme I intend to give a brief description of the aircraft for those who have not seen it before, and to refresh the memories of those who have.
An easy graphical method of obtaining generalised first order yacht performance
Authors: Dawson L. G.
Published: July 2022

For many years, a first order understanding of aircraft performance has been possible from lift drag curves or forward speed/sinking speed curves for gliders. These presentations of performance are not sufficiently accurate for detailed aircraft performance analysis, but their understanding has enabled generations of aircraft engineers to grasp the importance of various aerodynamic parameters.

A new method of presenting the sailing vector triangles is described. When the locus of the possible vector triangles is drawn in the new presentation, a large portion approximates to a straight line parallel to or making a small angle with the Xaxis in the neighbourhood of the best speed to windward. A geometrical construction is given, which defines the best speed to windward point. It becomes self-evident that, as is well known, most yachts sail at nearly 45 degrees to the true wind when sailing at their best windward condition.
The response of a pitot tube in the presence of a weak shock wave
Authors: Kalghatgi G. T. , Hunt B. L.
Published: July 2022

This note is concerned with the response of a pitot tube in the region of its interaction with a weak shock wave. It will be helpful if we distinguish immediately between our usage of the terms ‘pitot pressure’ and ‘normal shock recovery pressure’. We use the former to mean the experimental reading obtained from a pitot tube and the latter to mean the theoretical stagnation pressure downstream of a normal shock at the Mach number of a point in the flow.

Across an oblique shock, the normal shock recovery pressure changes discontinuously. However, in the course of a recent study of the impingement of supersonic jets on flat plates, the authors noticed that, as a pitot probe was traversed across a weak shock wave, not only was the discontinuity smoothed out by the finite size of the probe but also values of pitot pressure were obtained which were larger than the higher of the two values of normal shock recovery pressure.
Numerical study of non-uniform axisymmetric under-expanded supersonic jet impingement on a finite disc
Authors: Sankara Rao K. , Purohit S. C. , Sarma M. S.
Published: July 2022

The study of a jet impinging on a finite disc has applications in separating the stages of a multi-stage rocket during its flight. For example, the jet plume of the upper stage impinges and therefore induces a pressure field on the upper surface of the lower stage. A knowledge of this pressure field is vital in determining the trajectory of the lower stage after separation.
Seventy years of flight instruments and displays
Authors: Chorley R. A.
Published: July 2022

It may be asked why I have chosen the subject of instrumentation for this Folland Memorial Lecture, rather than one more closely allied to that of aircraft design— the craft of which we remember Henry Folland as a master. In part I believe the two subjects are closely related, and that a study of the way in which instrumentation has developed indicates many respects in which this development has paralleled, or depended upon, the various developments which have occurred in airframe design.

There is no indication in the admirable biographical lecture on H. P. Folland presented to this Society by his son, as to any special views he may have held on the subject of flight instrumentation. One thing is sure, however : his working life spanned the era in which there was a fundamental change in the views held by aviators about instruments.
Investigation into the optimum use of advanced displays in future transport aircraft
Authors: Hillman R. E. , Wilson J. W.
Published: July 2022

At last year’s Symposium ‘Designing from the inside out’ the keynote address made a strong case for improved matching of the machine to the man, starting with an understanding at the project stage of the optimum way that systems should be designed to achieve integration between man and machine. This year, we are discussing one aspect of human engineering—the presentation of information to the pilot.
Future trends in aero gas turbine design—Unconventional engines
Authors: Denning R. M. , Miller S. C. , Wright G. H.
Published: July 2022

The first part of this paper was concerned with the evaluation of the now classic form of low noise, single stage front fan engine as used on all contemporary designs of large subsonic civil aircraft.

This second part deals with other forms of the aircraft gas turbine which we have categorised as unconventional in the sense that they seek to achieve one or more of the following objectives:

(a)

a superior performance by moving towards more extreme constant pressure gas turbine cycles;

(b)

a superior performance by use of a different thermo-dynamic/propulsive system;

(c)

a performance which requires an ability to modify the thermodynamic cycle at different flight conditions;

(d)

uses for the engine which are additional to the normal propulsive role.

In the main, these engines are, as their title suggests, not generally adopted as powerplants for production aircraft and their often specialist role must detract from their wide use in a range of aircraft. However, it could be argued that the classic design of engine will soon be approaching a plateau of achievement and therefore some degree of unconventional form will be required in future to advance aircraft performance.
Lift augmentation on a moderately swept wing by spanwise blowing
Authors: Clarke Kenneth P.
Published: July 2022

At present it is still very difficult to predict for a given incidence, sweep-angle, leading-edge shape and Reynolds Number, whether the flow around a wing will remain attached or separate either from the upper surface as a bubble or from the leading edge as a vortex sheet which rolls up above the wing. Various attempts have been made to remove this uncertainty and it was suggested by Küchemann that it should be possible to design wings which combine coiled vortex sheets, originating from the inner part of the leading edge, with attached flow over the leading edge of the outer part of the wing. In this way some of the properties of slender wings could be combined with some properties of swept wings. His original model consisted of a swept-wing planform modified by inboard leading-edge wing strakes, the purpose of the latter being to provide the inboard vortex sheets. A similar idea has now been used in the wing design of the YF-16 lightweight fighter.
The pay-off for advanced technology in commercial aircraft design and operation
Authors: Brown D. G. , Lawson K. S.
Published: July 2022

The pay-off, in the final analysis needs to be a better air transport system for the traveller. This will, in turn, generate more traffic for the airline and hence more business for the aircraft manufacturer. To achieve a substantial and profitable share of the available market for new aircraft the manufacturer's product must be produced at the right time, meet the requirements of the airlines, and be competitive in terms of price and capability with the products, both new and existing, of his competitors. Advanced technology, applied in a cost effective manner, can be one of the ways of achieving this competitiveness and of improving the air transport system.
Engine noise—a look ahead
Authors: Cox M. , Higton D. R.
Published: July 2022

At the Symposium in April last year the Society met to consider how design and operation of quiet aircraft related to the often conflicting economic and environmental pressures. The prospects for quieter aircraft and engines were discussed from many technical points of view. The message emerging from the discussion was that, compared to the improvements made in the past 10 years, and which would be available now at the cost of replacing existing noisy, older generation installations, further reductions in noise at source would be very much harder to win. Moreover, they would be made against a steeply-rising trend of overall detriment to performance and direct operating cost.

So far as the possibilities are concerned for further reductions in the noise of subsonic propulsion engines, if we are to have more than modest, evolutionary improvements in levels, there will need to be radical changes affecting engine design, such as a definite move towards lower jet velocities.
The aero engine and its progress—fifty years after Griffith
Authors: Armstrong F. W.
Published: July 2022

The powerplant has always played a vital role in the development of aviation. In the beginning, the crucial need was for an engine of high enough power-to-weight ratio to enable the aircraft to fly at all. The Wright brothers had to build their own, and they took to the air with a four cylinder petrol engine having a specific weight of around 15 lb/hp. Much progress was made over the next two decades, and by the mid-nineteen twenties this figure was down to about 2 lb/hp. The aeroplane was now emerging from its infancy; the Atlantic had been flown, and the Otto cycle engine had established itself as successfully in the air as on the road.
Griffith's early ideas on turbomachinery aerodynamics
Authors: Howell A. R.
Published: July 2022

This paper is intended to supplement a part of the paper by Mr. F. W. Armstrong on ‘The aero engine and its prospects—fifty years after Griffith’. It deals in more detail with Dr. A. A. Griffith's early ideas on the aerodynamic aspects of turbomachines.

Even with reasonably optimistic use of materials and operating temperatures it was essential in 1926 that very high component efficiencies were obtained to make the gas turbine competitive with the piston engine on fuel consumption. Griffith believed that efficiencies of over 90% could be obtained for the compressor and turbine components, if the correct attention was given to the aerodynamic design of the blades. His 1926 report on ‘An aerodynamic theory of turbine design’ showed how such high efficiency designs should be carried out and gave appropriate formulae for the compressor and turbine efficiencies.
Buckling of simply supported laminated plates on elastic foundations
Authors: Turvey G. J.
Published: July 2022

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.
Spatial variations of the boundary layer in a large low-speed wind tunnel
Authors: East L. F.
Published: July 2022

In several recent reports reference is made to spanwise variations in the boundary layers growing in the working sections of various wind tunnels. Systematic investigations by Patel, Bradshaw and de Bray are in general agreement that these variations are caused by the screens which are fitted into the settling chambers of these tunnels to dampen out non-uniformities in the upstream flow. They conclude from their experiments that these variations will be much reduced if the downstream screen (or preferably the two downstream screens) has an open area ratio greater than about 0·57 and that these should be followed by a honeycomb to obtain the most steady and uniform flow, although a honeycomb in this position may increase the turbulence level in the working section.
Follower force instability of a pod-mounted jet engine
Authors: Done G. T. S.
Published: July 2022

In Figs. 1 and 2 are shown two cantilevers, one acted on by a force which maintains its direction as the cantilever deflects, and the other acted on by a follower force which remains tangential to the end of the cantilever. It can be shown, by a simple demonstration, that a follower force is non-conservative (see Bolotin), and therefore has the capability, if it exceeds a certain critical magnitude, of causing oscillatory instability. Thus, the follower force system in Fig. 2 can become unstable in the oscillatory sense while the Euler Strut in Fig. 1, being a conservative system, can become only “statically” unstable, i.e. with the strut diverging monotonically from its equilibrium position. The follower force system can, of course, also become statically unstable. The overall stability of this system has been examined by Bolotin and Beck. Herrmann and Bungay have investigated the stability of a system that combined the main characteristics of the two above in any chosen proportion.
Metallic materials for the space shuttle
Authors: Tavassoli A. A.
Published: July 2022

One of the great challenges of our time lies in the exploration of space. Part of this challenge has already been fulfilled but, up to this date, the transport of men and materials has been accomplished by means of expendable booster systems. In order to meet this challenge effectively, a new, fully reusable transportation system has been conceived which will be dramatically lower in overall cost than present-day launch systems. The proposed space shuttle is a fully reusable spacecraft consisting of a booster and an orbiter. A key factor in the design of the space shuttle is the selection and development of materials. Many current materials which have been widely and successfully used in space vehicles were developed for the most part with only a single short-time use requirement. The reusable, long-life requirements of the shuttle vehicle necessitates re-evaluation of the suitability of existing materials for this distinctly more demanding task for materials.
Flying insects as potential targets: initial feasibility studies with airborne Doppler equipment in East Africa
Authors: Rainey R. C.
Published: July 2022

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.
Advanced materials for aircraft brakes
Authors: Weaver John V.
Published: July 2022

The continued trend of increased weight and landing speeds of modern aircraft has strengthened the demand for improved materials for the manufacture of aircraft brakes.

The aircraft brake is similar to the car disc brake since both represent a medium for the conversion of kinetic energy to heat energy by means of friction. There are, however, unique problems which confront the aircraft brake designer since he is required to provide an acceptable mechanism involving components of minimum weight. The present paper discusses some general aspects of aircraft brakes and deals in more detail with some of the materials and material requirements for aircraft brakes; in particular it is hoped to show the manner in which advanced materials can provide some answers to the problems of the most recent development in design.
The Impact of the Digital Computer on Engineering Sciences
Authors: Argyris J. H.
Published: July 2022

The first question that a prospective lecturer of the august series in honour of Frederick William Lanchester should ask himself is the possible reason why he has been selected. I confess that for a considerable time I have been at a loss to understand this signal honour bestowed upon me. My mind ventilated a number of possible explanations starting from the evident but rather tenuous reasoning that both the eminent Mr. Lanchester and myself can show a connection with the leading Technological Institute of Britain, the Imperial College. But is this sufficient as a justification? I doubt it. Another path I tried to explore ventured along the intriguing intentional verbal slips and monumental sayings of Lanchester. Is it possible—I asked myself—that the wise Council of the Royal Aeronautical Society selected me on account of my undeserved reputation to have been in my Golden Youth an angry young man, an enfant terrible, and an early exponent of the anti-establishment criticism.
The Development of Small Gas Turbines for Aircraft Auxiliary Power
Authors: Paul C. H.
Published: July 2022

Your President and Mr. B. D. Blackwell of the Rolls-Royce company were brash enough to have suggested that I present the Halford Memorial Lecture. And 1 fear that I was impetuous in having accepted. I am sorry that I did not know Major Frank Halford, but from what I have read and from those with whom I have discussed his achievements, he was indeed a leader, an engineer, a designer, a man of much foresight, without whom our world of air transport would not have progressed so far. I know he would have been interested in the engine design trends which form the subject of my discussion—The Development of Small Gas Turbines for Aircraft Auxiliary Power.
Recent experience in flight testing for pilot induced oscillations (PIO) on transport aircraft
Authors: Lee B. P.
Published: July 2022

Though the subject of pilot induced oscillations (PIO) is not new, it has garnered significant attention in the past several years. Since the mid-1990s, Boeing Commercial Airplanes has been conducting specific flight tests of its products in order to evaluate PIO tendencies. Beginning with the 777-200, a generic suite of test manoeuvres has been used to evaluate PIO tendencies on each product. The testing has been conducted on a ‘window of opportunity’ basis with the intent to gather data and evaluate each model. To date, specific evaluations have been carried out on six different aircraft models spanning a wide range of aircraft sizes, inertial characteristics, and control system implementations. Each manoeuvre in the generic suite is discussed in detail. In addition, along the way, a large number of other manoeuvres have been used at various times to evaluate PIO tendencies. These are briefly described. No single test manoeuvre or technique has been identified which provides effective discrimination of PIO tendencies. Finally, the subject of the pilot in the loop is discussed with regard to achieving consistency in conducting PIO evaluations.
Elastic–plastic buckling behaviour of shafts in torsion
Authors: Robotham W. S. , Hyde T. H. , Williams E. J. , Taylor J. W.
Published: July 2022

The development of more powerful and efficient aero-engines requires ways of increasing the torque transmitted by shafts, whilst also restricting their dimensions and weight. Thin-walled designs can assist this objective, but their use is limited by their torsional collapse behaviour. Of particular interest are conditions leading to buckling instability. The paper investigates the factors influencing this behaviour in order to provide the basis for an improved analysis method applicable to typical gas turbine aero-engine components.

The Riks finite element algorithm has been successfully applied to both plain shafts and shafts with holes. In the former case, it is shown that the perfect cylindrical geometry must be given an initial perturbation in order to give accurate predictions. The perturbation imposed is obtained by scaling the mode shape from an eigenvalue solution so that the maximum radial deformation is a percentage of the wall thickness. The predictions for both plain and holed shafts have been validated experimentally.
The United Kingdom’s contributions to the development of aeronautics. Part 1. From antiquity to the era of the Wrights
Authors: Ackroyd J. A. D.
Published: July 2022

The Millennium now being upon us, it is perhaps appropriate to pause a while and take stock before leaping into an ever more problematic future. But why pause? Indeed, why bother with the past? Surely our newest, ever more sophisticated computer packages provide all the necessary paths to that next commercial edge, that future, unassailable military superiority? To this the German polymath, Gottfried Wilhelm von Leibniz, provides an apt, timely and, indeed, timeless corrective:

“It is an extremely useful thing to have knowledge of the true origins of memorable discoveries, especially those that have been found not by accident but by dint of meditation. It is not so much that thereby history may attribute to each man his own discoveries and others should be encouraged to earn like commendation, as that the art of making discoveries should be extended by considering noteworthy examples of it.”
The role of aero engineering in the sustainable development of the aviation industry
Authors: Thomas C. , Raper D.
Published: July 2022

The aviation industry plays a critical role in modern society, supporting global, regional and local economies and facilitating long distance travel for business and leisure. However the environmental impact of the industry is significant and this threatens the sustainability of future growth and the consequential benefits which could arise from it. Technological, operational and infrastructure improvements designed to reduce emissions and noise from aircraft are continually being eroded by the rapid growth of the industry, with the result that the environmental impact of air travel is increasing. Consequently, the sustainable development of the aviation industry will require that in future, technological innovation and fleet replacement continues at a rapid pace and that the highest priority is given to achieving a ‘step change’ in aircraft technology.
Stress analysis of door and window of a passenger aircraft
Authors: Ukadgaonker V. G. , Awasare P. J. , Gade S. V.
Published: July 2022

The stresses around the passenger door, emergency door and window of an aircraft, Airbus A300B, are considered in this paper. By idealising these opening as rectangular holes with rounded corners in an infinite plate subjected to inplane loads and considering the presence of adjacent holes the stresses are determined using the complex variable method along with Schwarz Alternating Method. The results of the analytical solution are found to be in good agreement with those of the finite element analysis using ANSYS 5.0 software within 5%.
ACFD applications to store separation — status report
Authors: Cenko A. , Lutton M.
Published: July 2022

During the past decade, the Navy has considerably improved its capabilities in aircraft-weapon integration. In 1989 it took more than 400 hours of wind-tunnel testing, which cost $1,5000,000, and 20 flights to clear the JSOW from the F-18 to Mach 0·95. This year the Mk-83 JDAM was cleared after only 60 hours of wind-tunnel testing and five flights to the full F-18 aircraft envelope of Mach 1·3. This reduction occurred because the Navy not only learned to test smarter, but also developed an integrated approach to modelling and simulation (M&S), wind-tunnel and flight testing which allowed lessons learned on previous programmes to be applied to new ones. However, the present approach still requires a fairly large commitment of time and financial resources to accomplish the mission.

The present approach has optimised the use of available resources; any further gains will have to come not by improving existing techniques, but by bringing new resources into the process.
Calculation of compressible indicial response
Authors: Shaw S. T. , Qin N.
Published: July 2022

The present paper addresses the problem of extracting indicial response functions from solutions of the Navier-Stokes equations. Two approaches are considered.

In the first, the indicial response is computed directly by modifying the local grid velocity to reflect the step change in plunge velocity. The computed data are then fitted using an assumed form for the response function and numerical optimisation techniques.

In the second (indirect) approach, the general form of the lift transfer operator is determined analytically from the functional form of the assumed response. Using the lift transfer operator explicit solutions of the in-phase and quadrature components of the normal force time history can be obtained. The unknown coefficients in the response function are then extracted from computed data for harmonic motion by fitting the time history using the explicit solution.

Computed response functions are presented for a range of Mach numbers and are compared with analytical results and indicial models currently used within the rotorcraft community. For the cases considered there is no significant difference between the response functions determined using the direct or indirect approach. Comparison of the computed results with existing models suggests that generalisation of the response to step changes in incidence using a two-pole approximation of the circulatory response together with the Prandtl-Glauert factor is not possible. However, comparison with higher order semi-empirical models is much improved, providing some justification for the use of such models. In addition to these observations, the extracted response functions suggest improvements to piston theory to account for thickness effects. The proposed modification of piston theory is based upon properties of the static pressure distribution and so can be used in conjunction with both CFD and experimental data.
Free-Jet Testing of a Supersonic Engine/Intake Combination
Authors: Morriss D. P. , Williams D. D.
Published: July 2022

The design and development of aircraft powerplants for sustained supersonic operation proves to be an exacting task which involves careful balancing of the requirements for high installed performance and system viability. The latter question may be dominated by the need to ensure flow compatibility at the intake/engine interface.
Aircraft Development and World Aviation Growth
Authors: Steiner J. E.
Published: July 2022

It is an honour and a privilege to commemorate the memory of Sir Charles Kingsford-Smith. It is 41 years since he linked by air the United States and Australian nations. Those 41 years have been years of phenomenal progress and growth from the infant industry of that time to the monumental industry of today.

Forty-one years ago the flying time from San Francisco to Australia was 83½ hours and the elapsed time was 10 days.
Pilot modelling and inverse simulation for initial handling qualities assessment
Authors: Cameron N. , Thomson D. G. , Murray-Smith D. J.
Published: July 2022

This paper describes the development of an approach to handling qualities investigation that can be applied at an early stage in t he design of the vehicle. It makes use of inverse simulation techniques, together with a pilot model to provide an integrated description of the man-machine control system. In order to incorporate pilot effects into data generated by inverse simulation, the output from an inverse simulation run is applied as input to a closed-loop system model that includes the vehicle dynamics and a simple parametric model of the pilot. Parameters of the pilot model are determined by optimisation and the pilot effect is added to the system output. Validation of the approach is achieved through a case study involving a predefined mission task involving a lateral manoeuvre. Equalisation characteristics estimated for each pilot are compared with those found by inverse simulation for the same manoeuvre. This approach may be applied using a simple real-time simulation on a desk-top computer and could be of value in identifying any potential deficiencies in a helicopter flight control system at an early stage in its development
Whitman’s Undemocratic Vistas: Mortal Anxiety, National Glory, White Supremacy
Authors: TURNER JACK
Published: July 2022

Walt Whitman’s Democratic Vistas (1871) has become a touchstone of democratic theory. Commentators of unusual ideological range uphold the book as politically exemplary. This article demonstrates that recent theoretical celebrations of Democratic Vistas are sanitized and incomplete. I expose the antidemocratic side of Democratic Vistas by analyzing (1) its philosophy of death and (2) its politics of race. Whitman framed his immortalist response to death within an imperialist historical teleology. That teleology entailed violations of Native sovereignty, the political inequality of Black Americans, and the projection of both Black and Native peoples’ evolutionary extinction. Democratic Vistas emerges from this analysis as both necropolitical and white supremacist. If, as Richard Rorty argues, Vistas models a salutary form of reformist “national pride,” then it also illustrates the dangerous susceptibility of such pride to moral innocence and self-deceit.
Singular elliptic equations with nonlinearities of subcritical and critical growth
Authors: Stapenhorst Matheus F.
Published: July 2022

In this paper, we consider the problem $-\Delta u =-u^{-\beta }\chi _{\{u>0\}} + f(u)$ in $\Omega$ with $u=0$ on $\partial \Omega$, where $0<\beta <1$ and $\Omega$ is a smooth bounded domain in $\mathbb {R}^{N}$, $N\geq 2$. We are able to solve this problem provided $f$ has subcritical growth and satisfy certain hypothesis. We also consider this problem with $f(s)=\lambda s+s^{\frac {N+2}{N-2}}$ and $N\geq 3$. In this case, we are able to obtain a solution for large values of $\lambda$. We replace the singular function $u^{-\beta }$ by a function $g_\epsilon (u)$ which pointwisely converges to $u^{-\beta }$ as $\epsilon \rightarrow 0$. The corresponding energy functional to the perturbed equation $-\Delta u + g_\epsilon (u) = f(u)$ has a critical point $u_\epsilon$ in $H_0^{1}(\Omega )$, which converges to a non-trivial non-negative solution of the original problem as $\epsilon \rightarrow 0$.
On the rationality of semi-secular simultaneity: a non-doxastic interpretation of the seemingly inconsistent worldviews of some Swedish ‘nones’
Authors: Palmqvist Carl-Johan , Jonbäck Francis
Published: July 2022

Proponents of religious non-doxasticism standardly aim to show how a commitment to traditional religion can be rational in the absence of religious belief. We demonstrate how the non-doxastic framework can be given a much wider application. In a study on Swedish semi-secularity, sociologist Ann af Burén has discovered a pattern where subjects simultaneously entertain naturalistic and supernatural explanations of extraordinary events. We reject Burén's interpretation of these people as irrational and compartmentalized and offer a contrasting non-doxastic reading in which the subjects involved are fully rational in their belief-less engagement with significant supernatural possibilities.
Cost-utility of a web-based intervention to promote maternal mental health among postpartum women presenting low risk for postpartum depression
Authors: Monteiro Fabiana , Antunes Patrícia , Pereira Marco , Canavarro Maria C. , Fonseca Ana
Published: July 2022

Objectives

Web-based interventions for the promotion of maternal mental health could represent a cost-effective strategy to reduce the burden associated with perinatal mental illness. This study aimed to evaluate the cost-utility of Be a Mom, a self-guided web-based cognitive behavioral therapy intervention, compared with a waiting-list control.

Methods

The economic evaluation alongside a randomized controlled trial was conducted from a societal perspective over a 14-month time frame. Postpartum women presenting low risk for postpartum depression were randomized to the intervention (n = 191) or control (n = 176) group and assessed at baseline, postintervention and 4 and 12 months after postintervention. Data regarding healthcare use, productive losses and quality-adjusted life years (QALYs) were collected and used to calculate incremental cost-effectiveness ratios (ICERs). Uncertainty was accounted for with nonparametric bootstrapping and sensitivity analyses.

Results

At 14 months, and after accounting for a 3.5 percent discount rate, the intervention resulted in a yearly cost-saving of EUR 165.47 (−361.77, 28.51) and a QALY gain of 0.0064 (−0.0116, 0.0244). Bootstrapping results revealed a dominant ICER for the intervention group. Although results were statistically nonsignificant, cost-effectiveness acceptability curves showed that at a EUR 0 willingness to pay threshold, there is a 96 percent probability that the intervention is cost-effective when compared with the control group. The sensitivity analyses generally supported the acceptable likelihood of the intervention being more cost-effective than the control group.

Conclusions

From a societal perspective, the implementation of Be a Mom among low-risk postpartum women could be a cost-effective way to improve perinatal mental health.
“Wow, I Didn’t Know These Options Existed”: Understanding Tenure-Track Start-Up Packages
Authors: Farris Emily M. , Key Ellen M. , Sumner Jane L.
Published: July 2022

Start-up packages vary enormously, particularly across institutions, and not all faculty know what items they may negotiate for to support their probationary period. To demystify this part of the hidden curriculum, we discuss the components of start-up packages and other benefits that may be provided to new faculty at the time of hire. We focus on five broad topics: compensation and personal support, general support, research support, teaching support, and service and professional development. Drawing on the results of a survey of tenure-track assistant political science professors in the United States, we also provide an overview of the prevalence of a variety of items at different types of institutions and discuss other considerations in the negotiation process to close the knowledge gap for candidates during negotiations.