bluuebunny/crossref_metadata_2025 huggingface dataset:
Experimental and computational
investigation into the use of co-flow fluidic thrust
vectoring on a small gas turbine
Authors: Banazadeh A. , Saghafi F. , Ghoreyshi M. , Pilidis P.
Published: February 2016

This paper presents the application of a relatively new
technique of fluidic thrust-vectoring (FTV), named
Co-flow, for a small gas-turbines. The performance
is obtained via experiment and computational fluid
dynamics (CFD). The effects of a few selected
parameters including the engine throttle setting,
the secondary air mass-flow rate and the secondary
slot height upon thrust-vectoring performance are
provided. Thrust vectoring performance is
characterised by the ability of the system to
deflect the engine thrust with respect to the
delivered secondary air mass-flow rate. The
experimental study was conducted under static
conditions in an outdoor environment at Cranfield
University workshop that was especially designed for
this purpose. As part of this investigation, the
system was modelled by CFD techniques, using
Pointwise’s Gridgen software and the
three-dimensional flow solver, Fluent. Also,
Cranfield’s gas-turbine performance code
(TurboMatch) was utilised to estimate boundary
conditions for the CFD analysis with respect to the
integrated nozzle. The presented technique is
easy-to-use approach and offers better result for
thrust-vectoring problems than previously published
works. Experimental results do show the overall
viability of the blowing slot mechanism as a means
of vectoring the engine thrust, with the current
configuration. Computational predictions are shown
to be consistent with the experimental observations
and make the CFD model a reliable tool for
predicting Co-flow fluidic thrust-vectoring
performance of similar systems.
Simulation interoperability — where are the challenges?
Authors: Tomlinson B. N.
Published: February 2016

This paper will discuss and review the nature of simulation interoperability. It will analyse the scope of interoperability in terms of basic intercommunication features (technical interoperability), fitness for purpose (functional interoperability) and suitability for use in distributed training (training interoperability). Only technical interoperability has received close attention, through DIS and HLA standards. Other aspects still present many challenges. The ability to create a common ‘outside world’ database is frequently cited as the dominant component and principal challenge in any discussion of interoperability. While this is often true, this paper identifies how interactions among all participants in the shared operational space (‘battlespace’) should be the starting point in defining interoperability, these interactions of course being dictated by the training requirement. Interactions are accomplished through ‘sensors’, which could be the human eye, night vision goggles (NVGs), radios, data links, radar, FLIR etc. Comprehensive interoperability demands comparable levels of modelling among all participants, including the effect of the environment (whether terrain or meteorology) on the performance of each simulator’s sensor suite. The paper will identify these significant effects and discuss where simulation technology is challenged and needs to advance, particularly in the context of mission simulation of future joint (Air/Land/Maritime) operations. The paper concludes with some discussion of the way ahead, including how guidelines based on experience could augment the use of standards.
Interchanging simulation databases with third parties using SEDRIS
Authors: Harris R.
Published: February 2016

Successful, seamless interchange of simulation databases has long proved surprisingly difficult to achieve. Numerous technical difficulties, arising from the different environmental representations used by different simulation systems, have proved to be only one facet of this difficulty. Often such problems are in fact the result of more fundamental underlying issues, such as the mathematical relationships between different co-ordinate systems. Logistical issues, and collaborative aspects of database interchange between different groups or companies, also contribute to the problems.

Thales has encountered many of these issues over the years in generating a range of databases for its simulation systems. These databases are required to correlate closely with other sensor systems, in particular the visual, but it is often the case that these other systems are third party products, using databases modelled by companies other than Thales. In these circumstances, the strategy used by Thales to generate its databases has typically been to derive them directly from the visual database. This has involved directly processing the visual database, extracting relevant geometry and attribution and formatting it for use by the Thales simulation systems. Historically, such visual databases have been provided by third parties using the SIF/HDI interchange format and imported directly into the Thales database generation toolset. While generating such derived databases in this way has been achieved successfully, many interchange issues referred to above were encountered and needed to be addressed.

When the need arose to replace SIF/HDI, the opportunity was taken to seek a replacement that would not only provide better representational capabilities but also address many of the wider, non-technical issues as well. Analysis of a variety of formats was undertaken and SEDRIS emerged as by far the strongest contender. Not only did it provide the best all round support for existing data representation requirements, it also gave good support for addressing wider interchange issues and offered a variety of opportunities to enhance the database generation toolset, both during initial development and over time.

This paper will discuss experiences using SEDRIS in this context. It will examine the basic representational requirements that needed to be met and the interchange problems that were to be overcome. The ways in which SEDRIS was seen to address these problems will be considered, along with the other advantages SEDRIS offered. Experiences developing SEDRIS software and interchanging databases using SEDRIS will also be described, including some lessons learned concerning both the use of SEDRIS and database interchange in general.
Structural health monitoring systems – benefits and airworthiness issues
Authors: Lloyd P. A.
Published: February 2016

In recent years there has been an increasing interest in the application of advanced structural monitoring systems to aircraft structures. A great deal of research effort has, and is being directed towards technologies that can detect damage and estimate its significance. In this paper the benefits of deploying such systems are discussed and illustrated with quantitative estimates where these are available. It is concluded that significant benefits should accrue from their use, but that a number of outstanding technical issues remain which include the realistic verification of performance and reliability. The impact on aircraft airworthiness is also considered and it is suggested that while no significant new issues emerge, considerable work will need to be done to qualify systems, and that this is unlikely to be worthwhile unless the expected benefits can be assured.
On the aerodynamics of the Gloster E28/39 – a historical perspective
Authors: Brinkworth B. J.
Published: February 2016

As commissioned to demonstrate the feasibility of jet propulsion, the E28/39 needed to exceed the performance of contemporary fighters. But Carter, the chief designer, took the opportunity to look further ahead, and devised an aircraft in which the onset of compressibility effects was taken into account from the beginning of the design. Successful operation over a wide speed range required a shrewd synthesis of previous experience and practice with uncertain material emerging from the research domain. The resulting aircraft showed no significant aerodynamic vices, requiring only minor modifications from its first flight to its participation in diving trials, that took it into hitherto unexplored regions of high subsonic speed. It proved to be fully worthy of its pivotal role at the beginning of a new era in aeronautics.

The aerodynamic features of Carter’s design are reviewed in relation to the limited state of knowledge at the time. Drawing upon fragmented material, much not previously published, this study enlarges upon, and in places amends, previous accounts of this notable machine.
The generation of sound in turbulent motion
Authors: Lilley G. M.
Published: February 2016

The present paper reviews and discusses the physical mechanisms of noise generation and reduction in turbulent flows with their applications towards aircraft noise reduction at takeoff and on the approach. This work began in 1948 when Lilley undertook an experimental investigation into the source of jet noise as a necessary precursor to finding methods for the reduction of high speed jet engine noise on civil jet airliners. Westley and Lilley completed this experimental programme in 1951, which included the design of a range of devices for high speed jet noise reduction. It was about this time that similar studies on jet noise were being started elsewhere and in particular by Lassiter and Hubbard in USA. The major contribution to the subject of turbulence as a source of noise came from Sir James Lighthill’s remarkable theory in 1952. In spite of the difficulties attached to theoretical and experimental studies on noise from turbulence, it is shown that with the accumulated knowledge on aerodynamic noise over the past 50 years, together with an optimisation of aircraft operations including flight trajectories, we are today on the threshold of approaching the design of commercial aircraft with turbofan propulsion engines that will not be heard above the background noise of the airport at takeoff and landing beyond 1-2km, from the airport boundary fence.

It is evident that in the application of this work, which centres on the physical mechanisms relating to the generation of noise from turbulence and turbulent shear flows, to jet noise, there is not one unique mechanism of jet noise generation for all jet Mach numbers. This author in this publication has concentrated on what appears to be the dominant mechanism of noise generation from turbulence, where the mean convection speeds of the turbulence are subsonic. The noise generated at transonic and supersonic jet speeds invariably involves extra mechanisms, which are only briefly referred to here.
Computational aeroacoustics: The low speed jet
Authors: Avital E. J. , Alonso M. , Supontisky V.
Published: February 2016

Low speed circular, elliptic and planar jets are investigated computationally for basic sound generation and hydrodynamics. The jets are assumed to be incompressible and are simulated using the large eddy simulation (LES) approach. The emitted sound is calculated using Lighthill’s acoustic analogy. Two formulations are used, Lighthill’s stress tensor formulation and Powell’s vortex sound formulation. A new boundary correction for Powell’s formulation is developed in order to account for the finite size of the computational domain. Low to moderate Reynolds number jets are simulated. Good agreement with known hydrodynamic results is achieved. This includes the nature of the transition process, e.g. enhanced mixing and axis switching in the elliptic jet and in some statistical results. The new boundary correction for Powell’s formulation proves to be vital in order to achieve good agreement with Lighthill’s formulation. Some success in high frequency prediction at least for the circular and elliptic jets is achieved in terms of getting the expected asymptotic behaviour. Both formulations show that the elliptic jet noise level is mildly lower than the circular jet noise level. Good to very good agreement is achieved in terms of directivities and frequency spectra with known results for the various jets.
Influence of the height of the vortex generators in the control of shock-induced separation of the boundary layers
Authors: Cohen G. S. , Motallebi F.
Published: February 2016

Experiments have been conducted to assess the effects that sub-boundary-layer vortex generators (SBVGs) have on reducing normal shock-induced turbulent boundary-layer separation. The freestream Mach number and Reynolds number were M = 1·45 and 15·9 × 106/m, respectively. Detailed measurements of a fully developed, flat plate turbulent boundary layer were used in order to assess the performance of ten different SBVG configurations. The SBVG performance was assessed by comparing total pressure profiles measured upstream of separation and downstream of reattachment. Static pressure distributions, near surface total pressure distributions, oil flow visualisation and Schlieren photographs were also used. The effect of SBVG height was investigated. The results show the largest SBVGs with height,h= 55%δ, provided the greatest static pressure recovery and maximum mixing. However, the shock pressure rise (wave drag) was highest for this case.
Capturing requirements for tiltrotor handling qualities – case studies in virtual engineering
Authors: Padfield G. D.
Published: February 2016

Handling qualities are expressed as requirements at the interface of the pilot and the machine. In this way, the key functionality questions facing the design engineer are seen from the perspective of the interaction of the human pilot with the aircraft system and the environment in which it operates. In this paper, the author takes a ‘virtual engineering’ approach to handling qualities, emphasising the importance of conducting ‘requirements capture’ and preliminary design as an iterative process. When stretched capabilities are required, this approach minimises the risk to finding appropriate technology solutions, through developing explicit relationships between capability and design parameters, thus facilitating fully informed trade studies and predictions. Case studies from the development of a civil tiltrotor aircraft are presented that show how the difficult challenges facing the designer first need to be structured in terms of HQ predictions and assignments. This then provides the basis on which handling qualities improvements can be constructed within the multidisciplinary context of rotorcraft engineering.
A study of various energy- and exergy-based optimisation metrics for the design of high performance aircraft systems
Authors: Periannan V. , Spakovsky M. R. von , Moorhouse D. J.
Published: February 2016

This paper shows the advantages of applying exergy-based analysis and optimisation methods to the synthesis/design and operation of aircraft systems. In particular, an Advanced Aircraft Fighter (AAF) with three subsystems: a Propulsion Subsystem (PS), an Environmental Control Subsystem (ECS), and an Airframe Subsystem – Aerodynamics (AFS-A) is used to illustrate these advantages. Thermodynamic (both energy and exergy based), aerodynamic, geometric, and physical models of the components comprising the subsystems are developed and their interactions defined. Off-design performance is considered as well and is used in the analysis and optimisation of system synthesis/design and operation as the aircraft is flown over an entire mission.

An exergy-based parametric study of the PS and its components is first presented in order to show the type of detailed information on internal system losses which an exergy analysis can provide and an energy analysis by its very nature is unable to provide. This is followed by a series of constrained, system synthesis/design optimisations based on five different objective functions, which define energy-based and exergy-based measures of performance. The former involve minimising the gross takeoff weight or maximising the thrust efficiency while the latter involve minimising the rates of exergy destruction plus the rate of exergy fuel loss (with and without AFS-A losses) or maximising the thermodynamic effectiveness.

A first set of optimisations involving four of the objectives (two energy-based and two exergy-based) are performed with only PS and ECS degrees of freedom. Losses for the AFS-A are not incorporated into the two exergy-based objectives. The results show that as expected all four objectives globally produce the same optimum vehicle. A second set of optimisations is then performed with AFS-A degrees of freedom and again with two energy- and exergy-based objectives. However, this time one of the exergy-based objectives incorporates AFS-A losses directly into the objective. The results are that with this latter objective, a significantly better optimum vehicle is produced. Thus, an exergy-based approach is not only able to pinpoint where the greatest inefficiencies in the system occur but appears at least in this case to produce a superior optimum vehicle as well by accounting for irreversibility losses in subsystems (e.g., the AFS-A) only indirectly tied to fuel usage.
Systematic review of the impact of emissions from aviation on current and future climate
Authors: Takeda K. , Takeda A. L. , Bryant J. , Clegg A. J.
Published: February 2016

Aviation emissions have an impact on the global climate, and this is consequently an active area of research worldwide. By adapting replicable and transparent systematic review methods from the field of evidence-based medicine, we aim to synthesise available data on the effects of aviation emissions on climate. From these data, we aim to calculate lower and upper bounds for estimates of the effect of aviation on climate in an objective manner.

For the systematic review an appropriate protocol was developed and applied by two independent reviewers, to identify research that met the inclusion criteria. These included all aviation types, original research studies, climate models with aviation as a specific component, with outcomes for emissions, radiative forcing, global warming potential and/or surface temperature changes. These studies were prioritised and data extracted using a standard process. The 35 studies reviewed here reported radiative forcing, global warming potential and/or temperature changes as outcomes, allowing direct comparisons to be made.

Tabulated results and a narrative commentary were provided for overall effects on climate, and the individual effects of carbon dioxide, water, contrails, cirrus clouds, ozone, nitrogen oxides, methane, soot and sulphur oxides. Lower and upper bounds for these effects, and their relative contributions compared to overall radiative forcing and surface temperature changes, have been described.

This review shows that the most recent estimates for the contribution of aviation to global climate are highly dependent on the level of scientific understanding and modelling, and predicted scenarios for social and economic growth. Estimates for the future contribution of aviation to global radiative forcing in 2015 range from 5·31% to 8·04%. For 2050 the estimates have a wider spread, from 2·12% to 17·33%, the latter being for the most extreme technology and growth scenario. These global estimates should be considered within the context of uncertainties in accounting for the direct and indirect effects of different contributions. Variations between lower and upper bounds for estimates of radiative forcing are relatively low for carbon dioxide, around 131% to 800% for cirrus clouds effects, and 1,044% for soot. Advances in climate research, particularly in the area of contrail and cloud effects, has led to some revision of the 1999 IPCC estimates(1), and demonstrates that the research community is actively working to further understand the underlying science.

The approaches assumptions, limitations and future work were discussed in detail. We have demonstrated how the systematic review methodology can be applied to climate science, in a replicable and transparent manner.
Experimental study of overexpanded co-flowing jets
Authors: Sharma H. , Vashishtha A. , Rathakrishnan E. , Lovaraju P.
Published: February 2016

An experimental investigation was carried out to find the effect of an annular co-flow jet on the primary supersonic jet from Mach 2 nozzle at different levels of overexpansion. In this study, a convergent-divergent circular nozzle of exit Mach number 2, surrounded by an annular convergent circular nozzle with an annular gap of 4·4mm was used. Nozzle pressure ratios (NPRs) 3, 4, 5, 6, 7 are investigated for overexpanded states of the primary jet and NPR 8 is investigated for almost correctly expanded state. The centreline pressure distributions were taken at all NPRs for both with and without co-flow case, to investigate the supersonic core extent and mixing activity in the jet field. In the radial direction pitot pressure at different axial locations at all NPRs for both the cases are measured to find the jet development and shadowgraph visualisation of jet structure was done to visualise the shock structure in near-field. It is found that the co-flow acts as mixing inhibitor at all levels of overexpansion for Mach 2 nozzle.
Distributed parameter control arithmetic for an axisymmetrical dual-mode scramjet
Authors: Tao C. , Daren Y. , Wen B.
Published: February 2016

Dual-mode scramjet is one of the candidates for hypersonic flight propulsion system which will be used in wide range of flight Mach numbers from 4 to 12 or higher, wherein dual-mode scramjet should be well designed to be suitable for subsonic/supersonic combustion operation according to the flight conditions. Therefore this system is required to operate in a finite number of operational modes that necessitate robust, stable, and smooth transitions between them by which selective operability of supersonic/subsonic combustion modes and efficient combustor operation in these modes may be realised. A key issue in making mode transition efficient and stable is mode transition control. The major problem in mode transition control is the handling of the various flow and combustion coupling effects of dual-mode scramjet whose physical states are spatially coupled and whose governing equations are partial differential equations. Involving these distributed parameter issues, our basic idea is using the shape control theory to study the control problems of mode transition for dual-mode scramjet with the aim of achieving the desirable design properties and increasing control reliabilities. This specific approach is motivated by the promise of novel techniques in control theory developed in recent years. Concrete control arithmetic of this approach, such as shape control model, sensitivity analysis and gradient-based optimisation procedure, are given in this paper. Simulation results for an axisymmetric, wall-injection dual-mode scramjet show the feasibility and validity of the method.
Flight mechanics of a free-wing tilt-body aircraft
Authors: Ro K. , Kamman J. W. , Barlow J. B.
Published: February 2016

The free-wing tilt-body aircraft refers to a vehicle configuration in which the wing, fuselage, and empennage are in a longitudinally articulated connection. This allows the main wing to freely rotate relative to the body, while the empennage, which is in the form of a long twin boom connected to the rear of the body, changes its incidence angle relative to the body in response to external commands. The principal advantages claimed for the configuration are short takeoff and landing capability, and reduced gust sensitivity. The aerodynamics of the free-wing tilt-body configuration has been previously studied, but analysis of its flight mechanics is limited. In this paper we present derivations of the flight dynamic equations of motion using multi-body dynamic modelling techniques, and combine the resulting equations of motion with experimental aerodynamic data to achieve a nonlinear mathematical model for flight simulation of a generic free-wing tilt-body vehicle. The mathematical model is suitable for the study of detailed dynamic characteristics as well as for model based control law synthesis. Key flight performance, and stability and control characteristics of a generic configuration are obtained from the mathematical model.
Experimental investigation of the aerodynamic characteristics of generic fan-in-wing configurations
Authors: Thouault N. , Breitsamter C. , Adams N. A. , Gologan C. , Seifert J.
Published: February 2016

This experimental investigation concentrates on the aerodynamic behaviour of a generic fan-in-wing configuration. The effects of the fan(s) on the flow circulation in a short take-off and landing or a transition flight condition without ground effect are evaluated. A wind-tunnel model has been constructed and tested to quantify the aerodynamic effects. Force measurements, surface pressure measurements, stereo-particle image velocimetry and wool tufts flow visualisation are performed. Different fan-in-wing configurations with the fans rotating in the wing plane, one fan either at the rear or front part of the wing and two fans are compared to the closed wing without fans set as reference. A fan placed near the trailing edge improves significantly the lift coefficient due to a jet flap effect on the wing lower side combined with enhanced suction on the wing upper side. The jet exiting the nozzle rolls up in a counter rotating pair of vortices affecting significantly the wing behaviour.

This experimental investigation constitutes also a useful database for further CFD comparison.
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

The 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

Experimental 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

The 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

The 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

Quantitative 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

The 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

The 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

This 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

The 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

The 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

Loss-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

Implicit 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

The 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.
Development of a parametric-based indirect aircraft structural usage monitoring system using artificial neural networks
Authors: Reed S. C.
Published: February 2016

The development of a parametric-based indirect aircraft structural usage monitoring system using artificial neural networks is described. Flight parametric data, captured during Operational Loads Measurement have been used to predict strains or stresses at key structural locations for several military aircraft types, using mapping relationships determined by artificial neural networks. A framework for the development of a neural network-based structural usage monitor is discussed and the basic architecture of the multilayer perceptron artificial neural network is described. Additionally, results from case studies are presented. It is concluded that this technology could provide the basis for accurate, cost-effective structural usage monitoring systems across the range of military aircraft types and roles.
A systems approach to training aeronautical decision making: from identifying training needs to verifying training solutions
Authors: Li W.-C. , Harris D.
Published: February 2016

The human factors analysis and classification system (HFACS) was developed as an analytical framework for the investigation of the role of human error in aviation accidents. A total of 523 accidents in the Republic of China (ROC) Air Force between 1978 and 2002 were analysed using this framework. The results showed that in a great many cases, poor pilot decision making was implicated. Following a survey of flight instructors’ opinions, two of most promising mnemonic-based methods currently available to guide the decision making of pilots were identified (SHOR and DESIDE). These methods were developed into a short (four hour) aeronautical decision making training course. A total of 41 pilots from the Republic of China Tactical Training Wing then participated in a study to evaluate the effectiveness of this training course. Half of the participants received the short ADM training programme and half did not. Their decision making skill was evaluated in a series of emergency situations presented in a full-flight simulator. Furthermore, their decision making processes were examined in a series of pencil-and-paper based tests. The results clearly showed significant improvements in the quality of pilots’ situation assessment and risk management (underpinning processes in pilot decision making) although this was usually at the expense of speed of response. Pilots used the quicker to apply SHOR mnemonic in situations that which required a fast decision and the more comprehensive but slower to perform DESIDE method when there were fewer time pressures. The results do strongly suggest that ADM is trainable and the short programme devised was effective.
Relationships between flying qualities and flight tests parameters for the F/A-18 aircraft
Authors: Botez R. M. , Rotaru M.
Published: February 2016

In this Technical Note, is shown that relationships exist between flying qualities levels 1, 2 and 3 and flight conditions expressed in terms of Mach numbers, altitudes and angles-of-attack for the F/A-18 SRA (System Research Aircraft). These relationships are helpful in detecting if derivatives are well calculated for flight tests intermediate conditions.