bluuebunny/crossref_metadata_2025_split huggingface dataset:
Trade disputes in the commercial aircraft industry: A background note
Authors: Hayward K. 
Published: February 2016

AbstractThe long-running debate between the US and the EU over government supports for large commercial aircraft has recently boiled over into a major dispute involving the World Trade Organisation (WTO). While the two sides have currently backed off from what could be a very damaging WTO outcome, there are still wide differences over the legitimacy of government supports (direct or indirect) for Airbus and Boeing airliners. This paper:
•Describes the background to the current dispute.•Analyses the 1992 US–EU Agreement on Large Aircraft Subsidies.•Outlines the WTO Agreement on Subsidies and Countervailing Measures and the decision by the US to mount an action under the WTO complaints procedures against launch investment for Airbus and the EU’s counter claim against Boeing.•Considers the precedents set by the WTO rulings on the Brazilian–Canadian dispute over regional jet supports.•Summarises the US–EU complaints to the WTO.•Considers potential outcomes and the implications for the civil aerospace industry on both sides of the Atlantic.•Analyses the wider issues surrounding government intervention in the aerospace sector.The paper views the dispute as a reflection of fundamental differences, based primarily on divergent economic doctrines and values, between the US and the EU states. There could be especially damaging consequences for the EU should the WTO rule against the systems of repayable launch investment used by the Airbus governments. But both sides could lose heavily from the affair and there is a good case for maintaining some form of direct government intervention in civil aerospace technology acquisition, even near market research, in support of environmental sustainability objectives.
Kite performance testing by flying in a circle
Authors: Stevenson J. , Alexander K. , Lynn P. 
Published: February 2016

AbstractWith the advent of recreational sports like kite surfing and buggying, the performance of kites has become a market driven item. Producers increasingly require methods to measure and improve the performance of the kites they manufacture. The Mechanical Engineering Department at the University of Canterbury has been working with a local kite producer to develop testing procedures suitable for kite manufacturers. The primary performance measurement is the lift to drag ratio. An early test rig was mounted in the top of a car, but limitations inherent in the design meant that it lost precision as the lift to drag ratio approached that of more advanced kites. This led the investigators to look for alternatives, and resulted in the development of the circular flight method. This method allows the test apparatus to be tuned to the performance of each kite, significantly improving the precision of the results while reducing the time taken for each test. In their raw form, the L/D results are not quite the same as those of the more traditional methods. But they reflect the underlying aerodynamic characteristics, and when used comparatively they can be used in the kite development process. Alternatively, with suitable processing the circular flight results can be converted to the traditional forms.
Semi–optimal co–ordinated manoeuvres for aircraft conflict resolution
Authors: Parastari J. , Malaek M. B. 
Published: February 2016

AbstractIn this manuscript, a new concept of 2D-semi-optimal-circular-3-arced-path manoeuvres with constant speed for multiple aircraft cooperative conflict resolution is presented. This type of manoeuvres is based on appropriate commands to heading, speed and manoeuvreing time. According to aircraft turning dynamics, each aircraft manoeuvre is composed of three tangent circular arcs. The optimality of manoeuvres is based on the minimisation of weighted sum of kinetic energy for aircraft two-legged manoeuvres. In comparison, aircraft with lower weight factors bear more responsibility to resolve the conflicts. The effectiveness of the proposed algorithm for real time conflict resolution is guaranteed, where the number of encountering aircraft is less than five. Otherwise, the current method could also be jointed to one of the fast resolution methods, like probabilistic resolution algorithm or genetic algorithm – as a tool to choose the convex domain – to become more computationally effective. Considerable number of case studies has been done to evaluate the effectiveness of the proposed methodology, while some are presented in the paper.
Effects of leading-edge bevel angle on the aerodynamic forces of a non-slender 50° delta wing
Authors: Wang J. J. , Lu S. F. 
Published: February 2016

AbstractThe aerodynamic performances of a non-slender 50° delta wing with various leading-edge bevels were measured in a low speed wind tunnel. It is found that the delta wing with leading-edge bevelled leeward can improve the maximum lift coefficient and maximum lift to drag ratio, and the stall angle of the wing is also delayed. In comparison with the blunt leading-edge wing, the increment of maximum lift to drag ratio is 200%, 98% and 100% for the wings with relative thickness t/c = 2%, t/c = 6.7% and t/c = 10%, respectively.
Progress toward CFD for full flight envelope
Authors: Tinoco E. N. , Bogue D. R. , Kao T-J. , Yu N. J. , Li P. , Ball D. N. 
Published: February 2016

AbstractThe value of computational fluid dynamics, CFD, delivered to date has mainly been related to its application to high-speed cruise design. To increase its applicability CFD must apply to the full flight envelope frequently characterised by large regions of separated flows. These flows are encountered by transport aircraft at low speed with deployed high lift devices, at their structural design loads conditions, or subjected to in-flight upsets that expose them to speed and/or angle-of-attack conditions outside the envelope of normal flight conditions to name a few. Such flows can only be characterised by the Navier-Stokes equations. This paper will report the progress toward CFD for full flight envelope. The CFD methods in use at Boeing will be described. Examples presented will address high-lift, loads and stability and control concerns including Reynolds scaling from wind tunnel to flight, vortex generator simulation, spoiler and horizontal tail effectiveness. In general, results shown are in ‘good enough’ agreement with experimental data. Deficiencies and the need for further algorithm and process improvement are noted. The need for automation to enable the large scale use of CFD will also be discussed.
Normal shock wave/turbulent boundary-layer interaction control using ‘smart’ piezoelectric actuators
Authors: Couldrick J. S. , Gai S. L. , Milthorpe J. F. , Shankar K. 
Published: February 2016

AbstractThis paper looks at active control of the normal shock wave/turbulent boundary layer interaction (SBLI) using smart flap actuators. The actuators are manufactured by bonding piezoelectric material to an inert substrate to control the bleed/suction rate through a plenum chamber. The cavity allows rapid thickening of the boundary-layer approaching the shock, which splits into a series of weaker shocks forming a lambda shock foot, thus reducing wave drag. Active control allows optimisation of the interaction, as it would be capable of either positioning the control region around the original shock position using a series of unimorph flaps or fixing the shock position by controlling the rate of mass transfer.The level of control achieved by unimorph piezoelectric actuators is not large because of small amounts of deflection possible. It is believed that to provide optimal control a piezoelectric material, which can provide greater strain and hence higher amounts of deflection is needed. However, currently such a piezoelectric material is not commercially available.
Fracture of layered composites by internal fibre instability: effect of interfacial adhesion
Authors: Soutis C. , Guz I. A. 
Published: February 2016

AbstractIn this paper, a mechanism of compressive fracture for elastic and elastic-plastic composite materials with interfacial adhesion defects is investigated. A classification of different approaches in modelling compressive response of layered materials is given. The analysis finds the upper and the lower bounds for the critical load. In order to achieve this, the problem of the internal fibre (layer) instability is considered within the scope of the exact statement based on the application of the model of a piecewise-homogeneous medium and the equations of the three-dimensional (3D) stability theory. The solution of the 3D problem is found for the most general case accounting for the bi-axiality of compressive loads. The characteristic determinants are derived for the first four fibre instability (microbuckling) modes, which are more commonly observed. Special attention is given to the calculation of critical loads for practical elastic and elastic-plastic layered materials.
Sub boundary-layer vortex generators for the control of shock induced separation
Authors: Cohen G. S. , Motallebi F. 
Published: February 2016

AbstractThe results of an investigation into the effects that sub-boundary layer vortex generators (SBVGs) have on reducing normal shock-induced turbulent boundary-layer separation are presented. The freestream Mach number and Reynolds number were M = 1·45 and 15·9 × 106/m, respectively. Total pressure profiles, static pressure distributions, surface total pressure distributions, oil flow visualisation and Schlieren photographs were used in the results analysis. The effects of SBVG height, lateral spacing and location upstream of the shock were investigated. A novel curved shape SBVG was also evaluated and comparisons against the conventional flat vane type were made. The results show that in all but two cases, separation was completely eliminated. As expected, the largest SBVGs with height,h= 55%δ, provided the greatest pressure recovery and maximum mixing. However, the shock pressure rise was highest for this case. The experiments showed that the mid height SBVG array with the largest spacing provided similar results to the SBVG array with the largest height. Reducing the distance to shock to 10δ upstream also showed some improvement over the SBVG position of 18δ upstream. It was suggested that total elimination of the separated region may not be required to achieve a balance of improved static pressure recovery whilst minimising the pressure rise through the shock. The effect of curving the SBVGs provided an improved near wall mixing with an improved static and surface total pressure recovery downstream of the separation line. The optimum SBVG for the current flow conditions was found to be the curved vanes ofh= 40%δ, with the largest spacing, located at 18δ upstream of the shock. Overall, it was apparent from the results that in comparison to larger vortex generators with a height comparable to δ, for SBVGs the parameters involved become more important in order to obtain the highest degree of mixing from a given SBVG configuration.
Impacts of low-pressure (LP) compressor’s deterioration upon an aero-engine’s high-pressure (HP) turbine blade’s life consumption
Authors: Naeem M. 
Published: February 2016

AbstractSome in-service deterioration in any mechanical device, such as an aero-engine, is inevitable. As a result of experiencing a deterioration of efficiency and/or mass flow, an aero-engine will automatically adjust to a different set of operating characteristics; thereby frequently resulting in changes of rpm and/or turbine entry temperature in order to provide the same thrust. Rises in the turbine entry-temperatures and the high-pressure turbine’s rotational speed result in greater rates of creep and fatigue damage being incurred by the hot-end components and thereby higher engine’s life cycle costs. Possessing a better knowledge of the effects of engine deterioration upon the aircraft’s performance, as well as fuel and life usages, helps the users to take wiser management decisions and hence achieve improved engine utilisation. For a military aircraft, using a computer performance simulation, the consequences of low-pressure (LP) compressor’s deterioration upon an aero-engine high-pressure (HP) turbine blade’s life-consumption have been predicted.
Comparison of experimental and numerical investigation on a jet in a supersonic cross-flow
Authors: Kovar A. , Schülein E. 
Published: February 2016

AbstractFlow interaction of three different jet configurations ejecting air from a flat plate into a supersonic cross flow were investigated experimentally and numerically. The test conditions encompassed a jet pressure ratio of Poj, P∞ = 100 at a Mach number of M∞ = 5 and Reynolds number of about Re∞ = 25 × 106 based on the length of the flat plate. The investigated test cases are: a) single jet; b) four jets positioned in-line in main flow direction; c) four jets positioned side-by-side in spanwise direction. The prediction of the overall flow phenomena as occurring within the interaction area was in fair agreement with the experiments, although quantitatively differences occur that will be discussed in the paper.The results of the comparison are presented and the experimental data are used to validate the applied code.
Boundary condition effects on the evolution of a train of vortex pairs in still air
Authors: Yehoshua T. , Seifert A. 
Published: February 2016

AbstractEffects of boundary conditions on the performance of compact oscillatory momentum and vorticity generators, commonly known as ‘synthetic jet’, ejecting a train of vortex-pairs into still air, were studied experimentally. The different boundary conditions altered the near-device entrainment process of the zero-net-mass-flux actuator. The measurements included hot-wire and Particle Image Velocimetry, cavity pressures and temperatures.When the actuator operates in still air, a quasi-2D vortex pair is generated due to the extreme shear at the edges of the fluid slug ejected during the blowing stage of each excitation cycle. The vorticity flux exiting the slot determines the resulting vortex-pair circulation. The threshold slot exit velocity, for the current configuration and operating conditions, determines if the vortices will be sucked into the actuator’s cavity or be released. Once released, the vortex convection speed approximately scales with the peak velocity at the slot exit. However, the normalised convection velocity increases with the slot Reynolds number.When even a very short extension is attached to one ‘lip’ of the actuator exit, the jet is deflected in the direction opposite the extended lip, due to the restriction on the entrainment process. When long, one ‘lip’ extension is attached, such that the vortex pair is ejected parallel to a plate, the coherence of the vortices improve, their phase speed and magnitude decrease.The effects of high-frequency excitation, ejected perpendicular to a wall into still air, were also investigated. It was found that the presence of the plate does not have a measurable effect on the wall normal excitation, indicating that the majority of the entrainment is taking place from the forward 180° of the actuator exit plane. When the slot is inclined to the surface at a shallow angle of 30 degrees, an unsteady wall jet is formed, transferring momentum along the wall. This is a direct result of the symmetry break, altering the relative magnitudes of the vortex pair.
Towards a silent aircraft
Authors: Dowling A.P. , Hynes T. 
Published: February 2016

AbstractWe set a target for a ‘Silent’ aircraft to be imperceptible outside the airfield perimeter in an urban environment, and then address conceptual designs to meet this requirement. Avoiding some traditional aircraft noise sources requires a radical rethink about the configuration. An all-lifting design has many benefits, enabling a closer integration of airframe and engine than the traditional ‘tube and wing’. Low-noise design includes taking advantage of shielding of engine noise by the airframe; low-noise engines with large, low speed jets; an order of magnitude increase in absorption by liners; and operations for low-noise informing the design. Progress to date on the Silent Aircraft Initiative is presented, along with some conceptual aircraft and engine designs. The further work needed to develop these into viable future aircraft is discussed.
Efficiency parameters for modern commercial aircraft
Authors: Nangia R. K. 
Published: February 2016

AbstractCurrently, there is great emphasis, worldwide, on environmental issues. This will have an impact on civil aircraft design, manufacture and operation.Since the advent of the jet engine and swept wing aircraft, the trends have naturally tended towards greater productivity through increasing speed and payload. The cruise speed of conventional civil aircraft is unlikely to increase beyond current levels. Further increases in productivity are achieved by increasing payloads. This has led towards larger aircraft with the capability for increased ranges. It is shown that designing aircraft for longer ranges increases fuel burn significantly.A series of aircraft operational parameters have been analysed. Selected data and established trends for current and future aircraft are presented. The data has been interpreted into efficiency terms, relating payload, range, fuel consumed and a measure of unit costs. It is shown that ‘value’ (cost) and noise effective efficiencies decrease dramatically with increasing range.Environmental and economic considerations, in the future, may well demand greater efficiency in preference to productivity. One solution for long-range services is to use short-range hops. Another is via air-to-air refuelling. This will be addressed, in more detail, in a future paper.
Aerodynamic effectiveness of the flow of exhaust gases in a generic formula one car configuration
Authors: Parra F. L. , Kontis K. 
Published: February 2016

AbstractThe effects of the flow of exhaust gases intentionally orientated on the rear wing element of a generic Formula One car body have been studied. A qualitative analysis of the effectiveness of a cold nitrogen jet on a NACA 0012 type of aerofoil has been conducted. The Reynolds number of the jet was 13,000, based on the jet velocity and diameter, and of the bodywork was 54,000, based on the free stream velocity and bodywork length. The lift coefficient was measured via a three-component strain-gauge force balance at four different ground-to-aerofoil heights (32, 45, 60 and 90mm) and incidence range –20 to +20 degrees. The surface flow patterns were visualised using the oil flow technique and were compared with numerical simulations. Pressure measurements were conducted using pressure tappings. The CFD solver was FLUENT. The RNGk-ε model was selected to solve the turbulent flow transport equations. The numerical study also comprised the investigation of the aspiration generated by exhaust gases when these are ejected inside a duct of greater diameter. A parametric investigation relating the relative diameter of exhaust pipe and outer duct and the relative overlap between the sides of the duct and the exhaust pipe was performed.
Research initiatives for improving the safety of offshore helicopter operations
Authors: Howson D. A. 
Published: February 2016

AbstractSince the late 1980s, the UK Civil Aviation Authority (CAA) has been leading a programme of research aimed at improving the safety of offshore helicopter operations. The motivation for this initiative came from a major joint CAA/Industry review of helicopter airworthiness, commissioned in 1982. This study led to a number of research projects and other reviews which, in turn, led to further research projects. A total of over 20 projects have been undertaken covering airworthiness and operational issues, and covering helicopters and helidecks. This programme of work has been jointly funded and monitored by the UK CAA-run Helicopter Safety Research Management Committee (HSRMC). This paper provides a top-level summary of current activities on the seven main ‘live’ research projects.
Rotorcraft simulation modelling and validation for control law design
Authors: Manimala B. J. , Walker D. J. , Padfield G. D. , Voskuijl M. , Gubbels A. W. 
Published: February 2016

AbstractThis paper describes the development and validation of a high fidelity simulation model of the Bell 412 helicopter for handling qualities and flight control investigations. The base-line model features a rigid, articulated blade-element formulation of the main rotor, with flap and lag degrees of freedom. The Bell 412 HP engine/governor dynamics are represented by a second-order system. Other key features of the base-line model include a finite-state dynamic inflow model and lag damper dynamics. The base-line model gives excellent agreement with flight-test data over the speed range 15-120kt for on-axis responses. Prediction of off-axis responses is less accurate. Several model enhancement options were introduced to obtain an improved off-axis response. It is shown that the pitch/roll off-axis responses in transient manoeuvres can be improved significantly by including wake geometry distortion effects in the Peters-He finite-state dynamic inflow model.
Developments in RF simulator technology – approaching the affordable fidelity limit
Authors: Pywell M. 
Published: February 2016

AbstractTechnology developments in radar frequency simulators of the type used to verify the performance of complex electronic warfare systems are described. The successful verification of this performance prior to combat use is a necessary pre-requisite of military platform survivability and mission success. These simulators and associated modelling and analysis tools have enabled a major shift during the last 15 years from expensive and limited flight trials to repeatable laboratory and anechoic chamber tests, although they will never totally supplant those trials. Most limitations of the early days of many-channel simulators, 25 years ago, have been resolved or adequately and – as importantly – affordably mitigated, largely enabled by computing power increases. Limitations remain that will, within affordability constraints driven by Defence Ministries worldwide, prevent perfect simulation (‘emulation’) and the attendant, tantalising but utopian goal of laboratory and chamber test results that precisely match those from flight test and combat.
‘Greener’ civil aviation using air-to-air refuelling – relating aircraft design efficiency and tanker offload efficiency
Authors: Nangia R. K. 
Published: February 2016

The aircraft industry, as a whole, is striving to limit its impact on the environment. Improved engine design and operation may offer a reduction in emissions of a few percent. More efficient air traffic control (ATC) may offer a limited reduction in overall fuel burn. Improvements in aerodynamic design and materials available (e.g. on A350XWB, B787) might achieve a few percent increases in efficiencies. The use of alternative fuels is some way off. The ACARE objectives present a stiff challenge.Our recent studies have shown that air-to-air-refuelling (AAR), well established in military circles, introduced to civil aircraft operations would provide fuel savings of the order of 30% – 40%. AAR will allow smaller (3,000nm range), more efficient (greener) aircraft, operating from shorter runways, to fulfil long-range route requirements. In addition, the ‘safety-net’ afforded by the availability of AAR will enable a host of hitherto borderline technologies to be accepted and utilised in future aircraft designs. Laminar flow will provide fuel savings and increased efficiency in its own right provided it is enabled within a civil AAR environment. Similarly, supersonic transport becomes an acceptable economic option.