bluuebunny/crossref_metadata_2025_split huggingface dataset:
Flight test results and analysis of SBAS-like algorithm from the implementation of the Asia-Pacific GNSS test bed
Authors: Pringvanich N. , Satirapod C. 
Published: February 2016

AbstractThe Asia-Pacific GNSS Test Bed is a regional collaborative programme that brings together aviation practitioners in the field of satellite navigation within the Asia-Pacific to study the performance of global navigation satellite systems (GNSS) and to develop a regional plan that will lead to a successful implementation of GNSS in the region. The program is a work program under the Asia-Pacific Economic Cooperation GNSS Implementation Team (APEC GIT), a working group under the APEC. The Test Bed has been in operation since August 2006. The system architecture reflects hybrid architecture between a satellite-based augmentation system (SBAS) and a ground-based augmentation system (GBAS). Test reference stations (TRSs), consisted of a dual-frequency GPS receiver, a communication interface, and a data archival hardware, have been installed in the participating economies. GPS data collected at the TRSs will be transmitted to the test master station (TMS) in Bangkok, Thailand. SBAS messages will be generated and the messages will be broadcasted through a test VHF station (TVS). A test user platform (TUP) will receive GPS signal and the SBAS messages broadcast from TVS and then calculate and archive the TUP’s positions.This paper discusses performance analysis and flight test results conducted in Thailand in September 2007. During flight trials, noting that the Test Bed broadcasts SBAS messages through a VHF data link (VDL) similar to that of GBAS, the impacts of VHF broadcast, such as transmitting power, terrain effects, and impacts of different aircraft attitudes and positions are analysed. Preliminary analysis result indicates that, while the GBAS VDL coverage is very good through out the 30nm airport terminal area, during approach, and even during taxi, considerations should be given to levels of transmitting power to eliminate possible intermittent loss of VHF messages received by the aircraft receiver. This intermittent loss of VHF messages results in very strong fluctuation of horizontal protection levels (HPL) and vertical protection levels (VPL) calculated by the TUP. To yield with possible problem, windowing techniques are proposed and analysed.
Pneumatic flow control studies using steady blowing on a supercritical aerofoil
Authors: Wong C. , Kontis K. 
Published: February 2016

AbstractExperimental studies have been conducted on a NASA 17-percent thick supercritical aerofoil with a Coanda trailing edge at subsonic speeds in both the boundary-layer control and circulation control regimes. Detailed boundary-layer surveys were performed along the mid span on the suction surface and around the Coanda trailing edge. The wake located at 43% chord-length behind the aerofoil was measured with a single-component hotwire anemometer, and the profile drag coefficients were calculated from the integration of wake momentum deficit. Lift forces and pitching moments were recorded from –20deg to +20deg incidence using a 3-component force balance. In the circulation control regime, the boundary-layer results indicated that separation bubbles are not present at high incidences compared to the boundary-layer control regime, and that minimised the potential for flow separation delay around the Coanda trailing edge. The spectral analysis of the wake showed a significant reduction of wake fluctuations at high incidences and improvement of the stability at the edge of the wake. The study of aerodynamic forces suggested the need to increase the blowing momentum coefficient if the circulation control is used near the stalling angle-of-attack.
Interactional aerodynamics and acoustics of a hingeless coaxial helicopter with an auxiliary propeller in forward flight
Authors: Kim H. W. , Kenyon A. R. , Brown R. E. , Duraisamy K. 
Published: February 2016

AbstractThe aerodynamics and acoustics of a generic coaxial helicopter with a stiff main rotor system and a tail-mounted propulsor are investigated using Brown’s Vorticity Transport Model. In particular, the model is used to capture the aerodynamic interactions that arise between the various components of the configuration. By comparing the aerodynamics of the full configuration of the helicopter to the aerodynamics of various combinations of its sub-components, the influence of these aerodynamic interactions on the behaviour of the system can be isolated. Many of the interactions follow a simple relationship between cause and effect. For instance, ingestion of the main rotor wake produces a direct effect on the unsteadiness in the thrust produced by the propulsor. The causal relationship for other interdependencies within the system is found to be more obscure. For instance, a dependence of the acoustic signature of the aircraft on the tailplane design originates in the changes in loading on the main rotor that arise from the requirement to trim the load on the tailplane that is induced by its interaction with the main rotor wake. The traditional approach to the analysis of interactional effects on the performance of the helicopter relies on characterising the system in terms of a network of possible interactions between the separate components of its configuration. This approach, although conceptually appealing, may obscure the closed-loop nature of some of the aerodynamic interactions within the helicopter system. It is suggested that modern numerical simulation techniques may be ready to supplant any overt reliance on this reductionist type approach and hence may help to forestall future repetition of the long history of unforeseen, interaction-induced dynamic problems that have arisen in various new helicopter designs.
Macro-fiber composite actuators for a swept wing unmanned aircraft
Authors: Bilgen O. , Kochersberger K. B. , Inman D. J. 
Published: February 2016

AbstractThe purpose of the research presented here is to exploit actuation via smart materials to perform shape control of an aerofoil on a small aircraft and to determine the feasibility and advantages of smooth control surface deformations. A type of piezoceramic composite actuator known as Macro-Fiber Composite (MFC) is used for changing the camber of the wings. The MFC actuators were implemented on a 30° swept wing, 0·76m wingspan aircraft. The experimental vehicle was flown using two MFC patches in an elevator/aileron (elevon) configuration. Preliminary flight and wind-tunnel testing has demonstrated the stability and control of the concept. Flight tests were performed to quantify roll control using the MFC actuators. Lift and drag coefficients along with pitch and roll moment coefficients were measured in a low-speed, open-section wind tunnel. A vortex-lattice analysis complemented the database of aerodynamic derivatives used to analyse control response. The research, for the first time, successfully demonstrated that piezoceramic devices requiring high voltages can be effectively employed in small air vehicles without compromising the weight of the overall system.
Flow visualisation of the helicopter brown-out phenomenon
Authors: Nathan N. D. , Green R. B. 
Published: February 2016

AbstractQuantitative and qualitative results of a series of experiments conducted on a rotor in ground effect at low forward speeds are presented. The velocity over a wide area of the ground effect wake was measured using particle image velocimetry, and the evolution of the flow is described as the forward speed increases. The formation of a dust cloud leading to so-called helicopter brown-out was simulated through a series of flow visualisation experiments. The technique involved sprinkling a fine dust on the ground below and ahead of the rotor. Larger dust clouds were observed at lower forward speed, and the dust cloud penetrated into the areas of the flow including those where vorticity levels were of low magnitude and occasional velocity fluctuations from the mean were large.
The effect of multiple stores arrangement on flutter speed of a shear deformable wing subjected to pull-up angular velocity
Authors: Fazelzadeh S. A. , Mazidi A. , Rahmati A. R. , Marzocca P. 
Published: February 2016

AbstractThe aeroelastic modeling and flutter characteristics of a shear deformable wing/stores configuration under pull-up angular velocity is investigated. An isotropic non-uniform wing, which structural model incorporates flexibility in transverse shear and warping effects, is considered. The aeroelastic governing equations and boundary conditions are determined via Hamilton’s variational principle. In order to exactly consider the span wise location and properties of the attached stores the generalised function theory is used. The partial differential equations are transformed into a set of eigenvalue equations through the extended Galerkin’s approach. Numerical simulation highlighting the effects of the pull-up angular velocity and store parameters and configurations, such as mass ratio and their attachment locations, on the flutter speed are presented. The results of flutter analyses are validated with the published results and good agreement is observed. Furthermore, the procedure for an optimal deployment of stores is obtained for the case of the wing with four stores.
Computational aeroelastic studies of a generic hypersonic vehicle
Authors: Thuruthimattam B. J. , Friedmann P. P. , Powell K. G. , Bartels R. E. 
Published: February 2016

AbstractThe hypersonic aeroelastic problem of a generic hypersonic vehicle having a lifting-body type fuselage and canted fins is studied using third order piston theory and Euler aerodynamics. Computational aeroelastic response results are used to obtain frequency and damping characteristics, and compared with those from piston theory solutions for a variety of flight conditions. Aeroelastic behavior is studied for the range of 2·5 < M < 28, at altitudes ranging from 10,000ft to 80,000ft. Because of the significant computational resources required, a study on optimal mesh selection was first carried out for use with Euler aerodynamics. The three dimensional flow effects captured using Euler aerodynamics was found to lead to significantly higher flutter boundaries when compared to those based on nonlinear piston theory. The results presented here illustrate some of the more important three dimensional effects that can be encountered in hypersonic aeroelasticity of complex configurations.
Aspects of battle damage repair of helicopter structures
Authors: Wang J. , Baker A. 
Published: February 2016

AbstractThis paper summarises recent research conducted at the Defence Science and Technology Organisation in the area of aircraft battle damage repair, covering aspects such as ballistic testing, ballistic damage prediction, non-destructive damage inspection, structure residual-strength assessment, repair materials and techniques, repair design approaches, repair implementation and demonstration. The research has been focused on military helicopter composite structures. This paper provides an overview of a wide range of research conducted and detailed information in selected areas. Considerations for future research directions are also briefly discussed.
Enhanced vortex stability in trapped vortex combustor
Authors: Vengadesan S. , Sony C. 
Published: February 2016

AbstractThe Trapped Vortex Combustor (TVC) is a new design concept in which cavities are designed to trap a vortex flow structure established through the use of driver air jets located along the cavity walls. TVC offers many advantages when compared to conventional swirl-stabilised combustors. In the present work, numerical investigation of cold flow (non-reacting) through the two-cavity trapped vortex combustor is performed. The numerical simulation involves passive flow through the two-cavity TVC to obtain an optimum cavity size to trap stable vortices inside the second cavity and to observe the characteristics of the two cavity TVC. From the flow attributes, it is inferred that vortex stability is achieved by circulation and the vortex is trapped inside when a second afterbody is added.
Investigation of Chinook helicopter operations with an external slung load after cable failure
Authors: Pavel M. D. 
Published: February 2016

AbstractThe Royal Netherlands Air Force (RNLAF) conducts frequent operations of Chinook helicopters with external slung loads. The normal RNLAF practice is for large external loads to be underslung by means of a two-strop suspension system backed up by a third point of suspension, the so-called ‘redundant HUSLE (Helicopter Underslung Load Equipment)’ comprising a redundant set of slings which come into action if one of the normal strops fails. The redundant HUSLE is relatively expensive in terms of time and operating costs. The present work has investigated the behaviour of a Chinook helicopter with an underslung load following failure of a front or rear strop, to determine whether the three-point suspension system can be safely replaced by a two-point suspension, eliminating the redundant HUSLE. The paper will demonstrate that although in general the redundant HUSLE results in a less violent helicopter reaction to a cable failure, it does not necessarily guarantee safety. It is concluded that flying with loads up to around two tonnes could be done safely with a two-point suspension system. A novel feature of this analysis of helicopter operations with slung loads is the integrated approach used for simulating pilot-in-the-loop load failures using a full non-linear model.
Upset recovery training: Lessons from accidents and incidents
Authors: Crider D. A. 
Published: February 2016

AbstractLoss-of-control upsets during normal flight are one of the most common types of aircraft accident. The study of these accidents reveals common characteristics that suggest areas where training can positively impact the safety of flight.A variety of causes lead to in-flight upsets, including mechanical failures, wakes, spatial disorientation, and stalls. While most upsets occur fairly rapidly, those resulting from spatial disorientation often occur more slowly. Spatial disorientation upsets in roll have occurred when the flight crew was distracted or thought that the autopilot was on when it was off. Spatial disorientation accidents in pitch also have occurred due to the somatogravic pitch-up illusion. Upsets due to mechanical failure, wakes, and spatial disorientation most often occur at unstalled conditions well within the aerodynamic flight data envelope. However, improper responses can cause the aircraft to enter a stall after the initial upset or, if the initial upset was due to a stall, continue in a stall. Such improper responses include not putting the column forward enough, or pulling back even though this makes the situation worse. These responses may be due to an over-emphasis during training on recovering with ‘minimum loss of height’; hardly relevant where hitting the ground is not a problem. Nearer to the ground, improper responses could be due to the visual cue that has been called ‘ground rush’. At all altitudes, it is crucial to train pilots to reduce angle of attack as a primary part of upset recovery at, or near, stall.Aircrews are likely to rely on stall protection systems to protect against loss-of-control upsets due to stalls. However, stalls due to airframe icing usually occur at a significantly lower angle-of-attack than stalls that occur with an uncontaminated airframe and, as a result, may occur before the stall protection system reaches the trigger angle-of-attack. Stalls may also occur without warning for uncontaminated airframes when the stall protection system fails. Such cases demonstrate the importance of recognising the stall cues and implementing positive sustained recovery controls promptly, without cues from the stall warning system. Even when the stall warning system does provide warnings, accident/incident history shows that crews may ignore stall warnings and either maintain nose-up controls or fail to execute and sustain positive recovery controls. Accident history also suggests that flight crews can be reluctant to move the pitch control in the nose-down direction when they are stalled and the aircraft is pitched nose low and/or significantly banked.In each of these scenarios, training might prepare pilots to respond correctly. This paper will present short case studies of several aircraft upset accidents and incidents and explore common threads that suggest areas of training that could prevent future upset accidents and incidents.
Implicit large eddy simulation of ship airwakes
Authors: Thornber B. , Starr M. , Drikakis D. 
Published: February 2016

AbstractImplicit large eddy simulations (ILES) of two different Royal Navy ships have been conducted as part of the UK Ship/Air Interface Frame-work project using a recently developed very high order accuracy numerical method. Time-accurate CFD data for fourteen flow angles was produced to incorporate into flight simulators for definition of safe helicopter operating limits (SHOLs). This paper discusses the flow phenomenology for the different wind directions and where possible reports on the validation of the ILES results for mean and fluctuating velocity components and spectra against experimental data.
CFD fire simulation of the Swissair flight 111 in-flight fire – Part 1: Prediction of the pre-fire air flow within the cockpit and surrounding areas
Authors: Jia F. , Patel M. K. , Galea E. R. , Grandison A. , Ewer J. 
Published: February 2016

AbstractThe SMARTFIRE computational fluid dynamics (CFD) software was used to predict the ‘possible’ behaviour of airflow as well as the spread of fire and smoke within a Swissair configured McDonnell Douglas MD-11 commercial transport aircraft. This work was undertaken by the Fire Safety Engineering Group (FSEG) of the University of Greenwich as part of Transportation Safety Board (TSB) of Canada, Fire & Explosion Group’s investigation into the in-flight fire occurrence onboard Swissair Flight 111 (SR111): TSB Report Number A98H0003. The main aims of the CFD analysis were to develop a better understanding of the possible effects, or lack thereof, of numerous variables relating to the in-flight fire. This assisted investigators in assessing possible fire dynamics for cause and origin determination. In Part 1, the numerical analyses to pre-fire airflow patterns within the cockpit and its vicinity are presented. The pre-fire simulations serve two ends. One is to provide insight into the flow patterns within the cockpit and its vicinity and further supportive numerical evidence for the airflow flight test observations. The other is to provide plausible initial flow conditions for fire simulations. In this paper, some flow patterns at a number of primary locations within the cockpit and its vicinity are highlighted and the predicted flow patterns are compared with the findings from the airflow flight tests. The predicted patterns are found to be in good qualitative agreement with the experimental test findings.
Methods for the design of energy efficient high speed aerospace vehicles
Authors: Riggins D. , Taylor T. , Terhune L. , Moorhouse D. 
Published: February 2016

AbstractThis paper continues development of the fundamental analytical science, methodology and tools required for the analysis, design, and optimisation of high speed aerospace vehicles in terms of the efficient use of on-board energy. Specifically, it presents the complete second-law characterisation and related system-level energy management effectiveness for high-speed vehicles (coupling both aerodynamic and propulsive subsystems). Modelling of the fluid dynamics utilises high-level (multi-dimensional) flow-fields representative of generic configurations of interest. Capability has been recently developed which allows detailed second-law performance audits in terms of the ‘common currency’ of entropy generation for high-speed vehicles (involving complete synthesis of both internal and external flow-fields, i.e. both aerodynamic and propulsive sub-systems). This capability is now extended to encompass and utilise multi-dimensional flow-fields generated by computational fluid dynamics solvers, including Navier-Stokes solvers. Furthermore, the methodology is shown in this paper to provide insight and fundamental direction for management of onboard energy (‘price paid’) for maximum performance missions.
A proposed reference framework for unmanned aerial vehicle and system airworthiness requirements
Authors: Maneschijn A. , Jones T. , Backström T. W. von , Ingham L. A. 
Published: February 2016

AbstractVarious programmes are underway internationally to establish legislative instruments for regulating civil and military unmanned aerial vehicles and systems. An analysis of a selection of these programmes revealed that the approaches used for airworthiness regulation are not harmonised and are usually limited to specific unmanned aerial vehicle types, indicating the need for a generic framework for airworthiness requirements. A functional Reference Framework for unmanned aerial vehicle and system airworthiness requirements was developed using Annex 8 of the Chicago Convention as a reference basis, supplemented with airworthiness procedures and functional requirements derived from manned aircraft regulations, unmanned aerial vehicle and system airworthiness material, and flightworthiness guidelines for reusable launch vehicles. Various airworthiness elements were identified for which further research is required to develop appropriate airworthiness requirements. This paper summarises the development of the framework and proposes the Reference Framework as a functional basis for generating comprehensive South African civil and military airworthiness requirements for unmanned aerial vehicles and systems.
High resolution computational unsteady aerodynamic techniques applied to manoeuvring UCAVs
Authors: Morton S. A. , Cummings R. M. , Forsythe J. R. , Wurtzler K. 
Published: February 2016

AbstractA method of high resolution simulation is proposed for Unmanned Combat Air Vehicles (UCAVs) undergoing manoeuvress at high angle-of-attack or transonic speeds. Motivation for the need to develop such a method is first presented to show payoff in the design cycle, followed by results of using the method on current manned fighter aircraft. Finally, a notional UCAV shape from Boeing military aircraft is presented to show the possibilities of how the method can accurately capture the relevant phenomenon of these difficult flight regimes.
A review of some current research on pressure sensitive paint and thermographic phosphor techniques
Authors: Kontis K. 
Published: February 2016

AbstractThe paper discusses the development and application activities within the Aero-Physics and Measurement Technology Laboratory at the University of Manchester on pressure sensitive paint and thermographic phosphor optical imaging systems for gas dynamic applications. It provides a brief review of the basic principles, fundamental theory, properties, chemical characteristics and bonding technologies associated with the two systems. A number of case studies are presented, which exhibit the range of applicability, limitations and potential for further development of the technologies.
Active control of swept shock wave/turbulent boundary-layer interactions
Authors: Couldrick J. S. , Gai S. L. , Milthorpe J. F. , Shankar K. 
Published: February 2016

AbstractThis paper looks at active control of the swept shock wave/turbulent boundary-layer interaction 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 provides communication of signals across the shock, allowing rapid thickening of the boundary-layer approaching the shock, which splits into a series of weaker shocks forming a lambda shock foot, reducing wave drag. Active control allows optimum control of the interaction, as it would be capable of positioning the control region around the original shock position and control the rate of mass transfer.