bluuebunny/crossref_metadata_2025 huggingface dataset:
BAE Systems/EPSRC integrated research programme in aeronautical engineering
Authors: McDougall N.
Published: February 2016

BAE Systems and the Engineering and Physical Sciences Research Council (EPSRC) have recently formed a partnership to invest in strategic research in aerospace and defence. The framework which has been developed as part of this new alliance places a strong emphasis on collaboration. This contrasts with the conventional approach to industry led research which is normally based on the establishment of ‘centres of excellence’ in specific subject areas. By using a collaborative approach, the funding partners aim to benefit from inter-disciplinary collaboration which will take place during the project, giving rise to a more effective use of the invested funds.

The objective of the research programme is to develop technologies which would support the design of low cost (both to acquire and operate) flapless unmanned aerial vehicles (UAVs). This work includes fundamental aerodynamic research to provide control forces without the use of conventional flaps, coupled with developments in the areas of control systems, manufacturing engineering, structural engineering, the electromagnetic behaviour of these structures and design optimisation. The output from the research has been extended to include the design, manufacture, assembly and flight of a demonstrator vehicle, which will provide the research teams with a platform on which to evaluate the performance of their technology in a realistic flight environment. A total of fourteen research groups at ten universities are involved in the five year programme, which has a total value of £6·5M (€9·75M).
Some hypersonic intake studies
Authors: Lanson F. , Stollery J. L.
Published: February 2016

A ‘two dimensional’ air intake comprising a wedge followed by an isentropic compression has been tested in the Cranfield Gun Tunnel at Mach 8·2. These tests were performed to investigate qualitatively the intake flow starting process. The effects of cowl position, Reynolds number, boundary-layer trip and introduction of a small restriction in the intake duct were investigated. Schlieren pictures of the flow on the compression surface and around the intake entrance were taken. Results showed that the intake would operate over the Reynolds number range tested.

Tests with a laminar boundary layer demonstrated the principal influence of the Reynolds number on the boundary-layer growth and consequently on the flow structure in the intake entrance. In contrast boundary layer tripping produced little variation in flow pattern over the Reynolds number range tested. The cowl lip position appeared to have a strong effect on the intake performance. The only parameter which prevented the intake from starting was the introduction of a restriction in the intake duct.

The experimental data obtained were in good qualitative agreement with the CFD predictions. Finally, these experimental results indicated a good intake flow starting process over multiple changes of parameters.
A methodology for the assessment of unit cost drivers for commercial aircraft
Authors: Tirovolis N. L. , Serghides V. C.
Published: February 2016

Presented in this paper are the prerequisite steps in a methodology for the identification and assessment of unit cost drivers for use in the development of a new design-oriented unit cost estimation methodology for large commercial jet aircraft with minimum seating capacity of 100 passengers. The work presented here focuses on unit cost, which is a significant element of the total aircraft cost and for the initial aircraft design process in particular. The methodology aims to investigate how aircraft design properties could influence cost. Cost estimation relationships, containing a wide range of the most highly correlated parameters, are retrieved from detailed regression analysis conducted on two different aircraft generation categories. Since the methodology is based on actual cost and technical data, it is accurate both in terms of predicting the aircraft unit cost or conducting cost-comparative studies between different aircraft concepts. The emphasis in this paper is mainly on the development approach and parameter assessments, adopted towards the final unit cost estimation methodology.
An analysis of exit availability, exit usage and passenger exit selection behaviour exhibited during actual aviation accidents
Authors: Galea E. R. , Finney K. M. , Dixon A. J. P. , Siddiqui A. , Cooney D. P.
Published: February 2016

The exits which passengers select in evacuation situations and the exits which are available post-crash is of great interest to aviation safety regulators who make rulings defining exit separation and aircraft evacuation certification, aircraft designers who develop the interior layout of aircraft cabins and position exits within the fuselage, cabin safety specialists who develop procedures for managing aircraft evacuation and cabin crew who must control aircraft evacuations. In this paper we examine issues associated with passenger exit selection behaviour and exit configurations frequently experienced during survivable crashes. This work makes use of the latest version of the Aircraft Accident Statistics and Knowledge database AASK V4.0, which contains information from 105 survivable crashes and over 2,000 survivors.
Experimental investigations on the application of lift enhancement devices to forward-swept aircraft model
Authors: Zhang W. , Wang J. J. , Wu Z.
Published: February 2016

The force measurements were conducted in low speed wind tunnel to investigate the effects of the scale, shape and the installation type of Gurney flap on a forward-swept aircraft model. The results indicated that both rectangular and triangular Gurney flaps can enhance the lift coefficient of the model tested, but with a little decrease of stall angle from 38° to 36°. The lift and drag coefficients increased with the Gurney flap scales. Meanwhile, the triangular Gurney flap can improve the aerodynamic performance more effectively when its high side is located near the wing root than the reverse installation with the low side near the wing root and the high side near the wing tip. Additionally, for the same Gurney flap, the model with smaller forward-swept angle can generate higher lift-enhancement in comparison with the larger forward-swept angle model.
The performance of round synthetic jets in quiescent flow
Authors: Jabbal M. , Wu J. , Zhong S.
Published: February 2016

PIV measurements in the near-field region of a jet flow emanating from a round synthetic jet actuator into quiescent air were conducted over a range of operating conditions. The primary purpose of this work was to investigate the nature of synthetic jets at different operating conditions and to examine the jet flow parameters that dictate the behaviour of synthetic jet actuators. The effects of varying diaphragm displacement and oscillatory frequency for fixed actuator geometry were studied. It was observed that the characteristics of synthetic jets are largely determined by the Reynolds number and stroke length. An increase in the former is observed to increase the strength of consecutive vortex rings that compose a synthetic jet, whereas an increase in the latter results in an increase in relative vortex ring spacing and for further increases in stroke length, shedding of secondary vortices. Correlations were also made between the operating parameters and the performance parameters most effective for flow control and which therefore determine the impact of a synthetic jet on an external flow. Relations of time-averaged dimensionless mass flux, momentum flux and circulation with the jet flow conditions were established and found to widely support an analytical performance prediction model described in this paper. It is anticipated that the experimental data obtained in this study will also contribute towards providing a PIV database for macro-scale synthetic jet actuators.
Ordinal logistic regression analysis of flight task ratings
Authors: Bradley R. , Maclaren W. M.
Published: February 2016

The relationship between a pilot workload rating for a simulated flight task in the proximity of an offshore platform helideck and three experimental factors – wind speed, wind direction and pilot is investigated. The statistical method employed is ordinal logistic regression, which allows the specifying and fitting of regression relationships between ordered categorical response variables and explanatory variables. The response variable in this context is a pilot’s rating of the workload induced by certain flight tasks, measured on an ordered categorical scale 1 to 10. Estimates of the effects of the explanatory variables are given and their practical significance discussed.
Circular flight kite tests: converting to standard results
Authors: Stevenson J. C. , Alexander K. V.
Published: February 2016

Kite testing by flying in a horizontal circle, was developed in order to address the inevitable accuracy problems inherent in pre-existing kite measurement techniques. However the raw results from this circular flight method are not directly comparable with traditional kite performance measurements. To enable direct comparisons to be made, modifying equations have been developed to convert the raw circular flight results into the traditional measurements of lift to drag ratio, and lift coefficient. This paper derives the modifying equations, and presents experimental results comparing traditional measurements with both the raw and modified circular flight results. The modifying equations are applied to an example set of results to assess the sensitivity of the test environment parameters. It is concluded that for many cases, the discrepancy between the raw circular flight test results and traditional measurement techniques is small enough to ignore. Alternatively, the modifying equations given in the paper may readily be encoded so that traditional results may be quickly obtained from this novel test method.
Operations and aircraft design towards greener civil aviation using air-to-air refuelling
Authors: Nangia R. K.
Published: February 2016

As civil aviation expands, environmental aspects and fuel savings are becoming increasingly important. Amongst technologies proposed for more efficient flight, air-to-air refuelling (AAR), ‘hopping’ and flying in close formation (drag reduction), all have significant possibilities. It will be interesting to know also how these technologies may co-exist e.g. AAR and formation flying.

In military use, AAR is virtually indispensable. Its benefits are real and largely proven in hostile and demanding scenarios. We present a case for applying AAR in a civil context to show that substantial reductions in fuel burn for long-range missions are achievable. Overall savings, including the fuel used during the tanker missions, would be of the order of 30-40% fuel and 35-40% financial. These are very significant in terms of the impact on aviation’s contribution to reducing atmospheric pollution.

AAR allows smaller, efficient (greener) aircraft optimised for about 3,000nm range to fulfil long-range route requirements. This implies greater usage of smaller airports, relieving congestion and ATC demands on Hub airports. Problems due to shed vortices and wakes at airports are reduced. Smaller engines will be needed.

Integrated (accepted) AAR could lead to further benefits. Aircraft could take-off ‘light’, with minimum fuel and reserves and a planned AAR a few minutes into the flight. The ‘light’ aircraft would not require over-rating of the engines during take-off and would therefore be less noisy during take-off and climb-out, permitting more acceptable night operations.

The availability of civil AAR will enable opportunities for hitherto borderline technologies to be utilised in future aircraft. Laminar flow will provide fuel savings and increased efficiency in its own right but could be significantly enhanced within a civil AAR environment. Similarly, supersonic transport may become an acceptable economic option.

AAR affords the possibility of a complete widening of the design space and this should appeal to the imagination of current and future designers.
Further analysis of self-induced roll oscillations of a non-slender delta wing
Authors: Beyers M. E. , Ericsson L. E.
Published: February 2016

In low-speed wind tunnel tests at α = 25 and 30º of a 45º delta wing with semicircular leading edges limit cycle oscillations occurred around the 50º roll trim angle. In some cases the oscillations were highly regular, in other cases, highly irregular. An analysis of the observed roll-oscillation dynamics has shown that several viscous flow phenomena are involved, which depend strongly on the leading-edge geometry, and whose relative importance can vary dramatically with the existing Reynolds number in critical flow regions. The possible role of surface roughness in modifying the viscous flow/motion coupling to cause these dramatically different test results is examined.
A turbulence criterion for safe helicopter operations to offshore installations
Authors: Rowe S. J. , Howson D. , Turner G.
Published: February 2016

This paper describes the development of a wind turbulence criterion for the safe operation of helicopters to offshore installations. The development of the criterion was recommended following a review of the environmental effects around offshore platform helidecks.

Currently, criteria exist for ambient temperature and for vertical wind component in the vicinity of helidecks, but a questionnaire-based survey of helicopter pilots revealed that the principal safety hazard and source of highest workload is turbulence around offshore installations. The new turbulence criterion will plug a long-standing gap in the guidance on offshore helideck design.

The paper describes how the criterion has been developed using piloted flight simulation in a research flight simulator together with data from wind tunnel tests on offshore platforms. Initial validation has been successfully performed, and extended to include correlation with the large database of helicopter operational flight data records being collected through the UK North Sea Helicopter Operations Monitoring Programme (HOMP).

The turbulence criterion will be used, together with existing criteria on vertical wind component and temperature, in the assessment of new offshore installation designs, or proposed modifications to existing designs, to determine wind conditions where turbulence is likely to be excessive for safe helicopter operations. These will be used to estimate helideck operability and thereby inform the installation topsides design process, and will provide input to the setting and maintenance of helicopter operational limitations for individual installations.

The work will lead to improved safety through better prediction of safe operating envelopes and helideck operability at the design stage. In addition, development of the work is expected to enable the wind environment around offshore installations to be mapped and monitored in-service using helicopter flight data records.

The new turbulence criterion has been included in updated guidance on helideck design, and offshore installation designers are now required to inform helicopter operators about wind conditions which result in violations of the turbulence criterion on their offshore installations (as is currently the case for the temperature and vertical wind component criteria).
Pressure sensitive paint measurements on a delta-wing in supersonic flow
Authors: Raju L. C. , Venkatakrishnan L. , Viswanath P. R.
Published: February 2016

Experiments have been performed documenting the pressure field on the lee-side of a delta-wing at three incidence angles (5°, 10°, and 15°) and at Mach 1·8 using a PSP (Pressure Sensitive Paint) technique. The delta-wing model having a leading edge sweep of 60° was instrumented with 31 spanwise pressure ports at 68% of mean chord location. The Optrod-B1 binary paint was utilised and the PSP images were processed employing a resection based methodology. The comparisons of PSP results with those measured employing pressure taps show good agreement at different incidence angles.
Using system engineering on an aircraft improvement project
Authors: Hsu J. C.
Published: February 2016

A complete system engineering process is applied to a pilot project that will determine the initial deployment of the system engineering process for future projects. It was a challenge to complete the entire systems engineering process to include project team utilisation of system engineering tools in such a short time span. Therefore, systems engineering products had to be useful and productive to the project. The system requirements definition, quality function deployment (QFD) evaluation, trade study, risk identification and risk mitigation processes were completed in a timely manner and assisted in the system eequirements, system design and preliminary design reviews successfully.
Lean engineering: a framework for doing the right thing right
Authors: McManus H. L. , Haggerty A. , Murman E.
Published: February 2016

Lean techniques are having a major impact on aerospace manufacturing. However, the cost and value of aerospace (and many other) products is determined primarily in product development. Migrating lean to engineering processes is ongoing in the industry, and a subject of study at the MIT Lean Aerospace Initiative. This paper summarises findings to date, with references to both research literature and successful implementation examples. To implement lean engineering, a three-part approach is needed: Creating the right products, with effective lifecycle and enterprise integration, using efficient engineering processes.
Effect of plunging amplitude on the performance of a wind turbine blade section
Authors: Soltani M. R. , Marzabadi F. Rasi
Published: February 2016

In many engineering applications (e.g. helicopters, turbines, compressors), lifting surfaces experience unsteady motion or are perturbed by unsteady incoming flows. Horizontal axis wind turbine rotors experience large time dependent variations in angle-of-attack as a result of control input angles, blade flapping, structural response and wake inflow. In addition, the blade sections encounter substantial periodic variations in local velocity and sweep angle. Thus, the unsteady aerodynamic behaviour of the blade sections must be properly understood to enable accurate predictions of the air loads and aero elastic response of the rotor system.
Some analytical and numerical solutions for the safe turn manoeuvres of agricultural aircraft – an overview
Authors: Rasuo B.
Published: February 2016

In this paper, a theoretical study of the turn manoeuvre of an agricultural aircraft is presented. The manoeuvre with changeable altitude is analyzed, together with the, effect of the load factors on the turn manoeuvre characteristics during the field-treating flights. The mathematical model used describes the procedure for the correct climb and descent turn manoeuvre. For a typical agricultural aircraft, the numerical results and limitations of the climb, horizontal and descending turn manoeuvre are given. The problem of turning flight with changeable altitude is described by the system of differential equations which describe the influence of the normal and tangential load factors on velocity, the path angle in the vertical plane and the rate of turn, as a function of the bank angle during turning flight. The system of differential equations of motion was solved on a personal computer with the Runge-Kutta-Merson numerical method. Some analytical and numerical results of this calculation are presented in this paper.
An idea of distributed parameter control for scramjet engines
Authors: Daren Y. , Tao C. , Wen B.
Published: February 2016

Scramjet engines are used under extreme temperatures and with wide range of Mach numbers from 3 to 8 or higher and have shown different control properties from other airbreathing engines. New control problems involving distributed parameter control have been found concerning investigations of the control of scramjet engines whose physical states are spatially interacted and whose governing equations are partial differential equations. The work of this paper is based on the application of distributed parameter control conception to study the control problems of scramjet engines with the aim of achieving the desirable design properties and increasing control reliability. A new control idea based on shape control theory is put forward to realise the distributed parameter control of scramjet engines with the preconditions of proper space dimension and frequency-domain simplification. Simulation results and theoretic analysis for an axisymmetric, wall-injection scramjet engine show the feasibility and validity of the control idea.
The onset of compressibility effects for aerofoils in ground effect
Authors: Doig G. , Barber T. J. , Leonardi E. , Neely A. J.
Published: February 2016

The influence of flow compressibility on a highly-cambered inverted aerofoil in ground effect is presented, based on two-dimensional computational studies. This type of problem has relevance to open-wheel racing cars, where local regions of high-speed subsonic flow form under favourable pressure gradients, even though the maximum freestream Mach number is typically considerably less than Mach 0·3. An important consideration for CFD users in this field is addressed in this paper: the freestream Mach number at which flow compressibility significantly affects aerodynamic performance. More broadly, for aerodynamicists, the consequences of this are also considered. Comparisons between incompressible and compressible CFD simulations are used to identify important changes to the flow characteristics caused by density changes, highlighting the inappropriateness of incompressible simulations of ground effect flows for freestream Mach numbers as low as 0·15.
Method for aerodynamic unsteady forces time
calculations on an F/A-18 aircraft
Authors: Biskri D. E. , Botez R. M.
Published: February 2016

In this paper, a new original method based on the least
squares method is presented for the conversion of
unsteady aerodynamic forces from frequency into
Laplace domain, in which the error is written in an
analytical form as a function of the Laplace
variable, similar to the analytical form of the
aerodynamic forces calculated by use of the least
squares method. This method is applied on an F/A-18
aircraft (14 symmetric and 14 anti-symmetric modes)
for one Mach number and for a set of 14 reduced
frequencies. Two different types of results are
obtained and analysed: aerodynamic force
approximations in the Laplace domain and flutter
speeds and frequencies values. For a better
comparison of these results, different lag term
numbers are used. Results obtained by this new
method are better in terms of execution speed and
precision than the results obtained by use of the
least squares method.
Impacts of low-pressure (LP) compressor’s
deterioration of a turbofan engine upon fuel-usage
of a military aircraft
Authors: Naeem M.
Published: February 2016

Some in-service deterioration in any mechanical device,
such as an aircraft’s gas-turbine engine, is
inevitable. However, its extent and rate depend upon
the qualities of design and manufacture, as well as
on the maintenance/repair practices followed by the
users. Deterioration of an engine normally results
in the engine seeking a different steady
operating-point relative to that for an engine
without any deterioration. The variation in engine’s
steady operating point leads to changes in the
specific fuel consumption (SFC) and/or fuel flow
(FF). Any rise in SFC and/or FF and thereby the
increased quantity of fuel required is of prime
importance in military aviation.

For a military aircraft’s mission-profiles (consisting
of several flight-segments), using a bespoke
computer simulations, the consequences of
low-pressure compressor’s deterioration of an
aeroengine upon the weight of the fuel that has to
be carried and consumed are predicted. This will
help in making wiser management decisions (such as
whether to remove an aero-engine from the aircraft
for maintenance or to continue using it with some
changes in aircraft’s mission profile). Hence
improved engine utilization can be achieved, so
resulting in lower overall life-cycle costs.
Flight parameter based fatigue analysis approach for a fighter aircraft
Authors: Tikka J. A.
Published: February 2016

This paper describes a flight parameter based fatigue life analysis approach, which is developed for the Finnish Air Force F-18 fighters. It produces a flight specific fatigue life estimate for structural details using flight parameter data stored by each aircraft. Artificial neural networks are used to model structural response of analyzed details as a function of flight parameters. The analysis development is based on strain gauge data from 25 flights of an instrumented aircraft. The results show a satisfactory accuracy for the fatigue life estimates and prove the concept level analysis capability. The average difference between measured and modelled fatigue life is 21% for the fuselage bulkhead and 30% for the leading edge flap’s hinge area. The total differences in the Finnish Air Force average usage are extremely small, being –2% for the bulkhead and +2% for the leading edge flap.
Lateral-directional controller design using a pilot model and flight simulator experiments
Authors: Tokutake H. , Fujinaga J. , Miura Y.
Published: February 2016

A new controller design method of lateral-directional dynamics is proposed. This method is based on the formulated pilot model, and the controller is designed so that the pilot-aeroplane system attains the desired requirements. Robust stabilities and handling qualities can be taken into account. The proposed method was applied to B747 dynamics, and flight simulator experiments were performed, and the designed controller was verified.
What price supersonic speed? an applied market research case study Part 2
Authors: Chudoba B. , Oza A. , Coleman G. , Czysz P. A.
Published: February 2016

The first supersonic business jet to enter the market will not face its competition from rival supersonic designs under development. Its true competitors are the then current generation of highly evolved high-subsonic business jets when compared on economic grounds. For a price tag of $1m for the new conception of very light jets, ranging up to $45m for the highest-performing ‘race-horse’-like corporate jets, this breed of aircraft is able to accommodate the needs of most executives, VIPs, officials, from corporate transportation to cargo services of civil to military origin. Understanding the state of modern business class aircraft and their market is essential in gaining base knowledge required for any supersonic business jet endeavor aiming at a prospective market. The key descriptors for this marketplace are market potential, market productivity, and market drivers, altogether being a measure for growth and consumer demand. Such common denominator is used to gain the understanding necessary to ascertain and visualise the top level implications regarding any supersonic business case. Having assembled an understanding of the key descriptors for business aviation, the study first analyses the flight operation of traditional subsonic and high-subsonic business jets. Such perceptive is then complemented with the peculiarities associated with supersonic operation, ultimately defining the supersonic solution space consisting of market viability, efficiency, and overall flight performance. Consequently, a vehicle development strategy and mission specification are suggested for the first generation of supersonic business jets (SSBJ) and supersonic cargo jets (SSCJ).
Active sensing of impact damage in composite sandwich panels by low frequency Lamb waves
Authors: Soutis C. , Diamanti K.
Published: February 2016

The development of a robust non-destructive system to detect and monitor the extent of damage in carbon fibre reinforced plastics (CFRP) during service life is a key problem in many practical applications, especially in the aircraft industry. The lack of such technique has severely limited the potentially extensive use of composite materials. In this study a cost and time effective inspection strategy for in-service health monitoring of composites is demonstrated using the fundamental anti-symmetric A0 Lamb mode at frequencies of 15-20kHz. In principle, this method involves analysis of the transmitted and/or reflected wave after interacting with the test-piece boundaries or discontinuities (defects). In the present work, the applicability of the technique to composite sandwich structures is explored and defects of critical size are successfully detected.
Conceptual design assessment of a suborbital tourist space access vehicle
Authors: Chudoba B. , Coleman G. , Huang X. , Czysz P. A.
Published: February 2016

Space transportation remains in the pioneering stages. What might this century bring if we had a ‘railroad to space’ that embodied the characteristics of the transcontinental undertaking? The X-33 and Venture Star projects were one attempt to achieve the characteristics of that transcontinental railroad. There are others, here and in other countries, but perhaps we need to begin with a smaller first step, a small, commercial reusable rocket with ballistic ascent to space altitude with a hypersonic glider return? Our challenge in space today is to develop vehicles that are in continuous use, maintained and operated on a fixed schedule despite weather or environmental hazards, which move payloads not only into space but back again. The X PRIZE was a $10 million prize awarded to Scaled Composites as the first privately financed spaceship that launched the equivalent of three persons to an altitude of at least 100 kilometers on two consecutive flights within two weeks. What about an analogous vehicle that flies two or three times a week, every week for a number of years? A major difference is that this challenge is to be accomplished without government support or government developed vehicles. The aerospace vehicle design (AVD) Laboratory team at the University of Texas at Arlington is developing a generic space access vehicle (SAV) design synthesis environment with focus on the conceptual design phase. The AVD Lab has applied elements of this toolbox to the study of a tourist aerospace vehicle under a grant from Rocketplane Limited, Inc. The development of a low-cost tourist vehicle based on the adaptation of a Learjet 25/35/45 series aircraft is the focus of this paper.
Effect of amplitude and mean angle-of-attack on the boundary layer of an oscillating aerofoil
Authors: Soltani M. R. , Bakhshalipour A.
Published: February 2016

Extensive experiments were conducted to study the effect of various parameters on the surface pressure distribution and transition point of an aerofoil section used in a wind turbine blade. In this paper details of the variation of transition point on the aforementioned aerofoil are presented. The aerofoil spanned the wind-tunnel test section and was oscillated sinusoidally in pitch about the quarter chord. The imposed variables of the experiments were free stream velocity, amplitude of motion, mean angle-of-attack, and oscillation frequency.

The spatial-temporal progressions of the leading-edge transition point and the state of the unsteady boundary-layer were measured using eight closely-spaced, hot-film sensors (HFS). The measurements show that:

(i) Reduced frequency has a pronounced effect on the variations of the transition point.

(ii) There exists a hysteresis loop in the dynamic transition location and its shape varies with the reduced frequency and mean angle-of-attack.
CVF ski-jump ramp profile optimisation for F-35B
Authors: Fry A. , Cook R. , Revill N.
Published: February 2016

This paper presents a summary of the principles and processes used to design a ski-jump ramp profile for the UK’s Future Aircraft Carrier (CVF) optimised for the Joint Strike Fighter (JSF).

The paper includes an overview of the CVF and JSF programs, a history and summary of the ski-jump ramp and the principles of its use in the shipborne Short Take-Off (STO) manoeuvre.

The paper discusses the importance of defining optimisation boundaries including specified objectives, aircraft configurations and environmental conditions. It then demonstrates the process of balancing the design drivers of air vehicle performance and landing gear loads to achieve an optimum profile. Comparisons are made between the proposed candidate CVF ramp profile and the current in service ski-jump design as designed for the Harrier family of aircraft.

The paper briefly covers some of the important issues and factors that have been experienced when a theoretical profile is translated into a physical ramp fitted to a ship, principally the effects on aircraft operations due to build and in-service variation from the nominal profile.
Large Eddy Simulation of a complete Harrier aircraft in ground effect
Authors: Page G. J. , McGuirk J. J.
Published: February 2016

This paper aims to demonstrate the viability of using the large eddy simulation (LES) CFD methodology to model a representative, complete STOVL aircraft geometry at touch down. The flowfield beneath such a jet-borne vertical landing aircraft is inherently unsteady. Hence, it is argued in the present work that the LES technique is the most suitable tool to predict both the mean flow and unsteady fluctuations, and, with further development and validation testing, this approach could be a replacement, and certainly a complementary aid, to expensive rig programmes. The numerical method uses a compressible solver on a mixed element unstructured mesh. Examination of instantaneous flowfield predictions from these LES calculations indicate close similarity with many flow features identified from ground effect flow visualisations, which are well known to be difficult to model using RANS-based CFD. Whilst significant further work needs to be carried out, these calculations show that LES could be a practical tool to model, for example, Hot Gas Ingestion for the Joint Strike Fighter aircraft.
On the characteristics of a twin-jet STOVL fountain
Authors: Saddington A. J. , Knowles K. , Cabrita P. M.
Published: February 2016

The interaction of multiple jets with the ground is of great importance for the design and operation of short take-off, vertical landing aircraft. The fountain upwash flow, generated by the impingement of two axisymmetric, compressible, turbulent jets onto a ground plane was studied using laser-based particle image velocimetry and laser Doppler velocimetry. Measurements were made with nozzle pressure ratios of between 1·05 and 4, nozzle height-to-diameter ratios of between 2·4 and 8·4, nozzle splay angles of between ±15 degrees and a nozzle spacing-to-diameter ratio of seven. The effect of varying these parameters on the fountain velocity decay, spreading rate and momentum flux ratio are discussed. Mean fountain upwash velocity profiles were found to be self-similar for all test conditions. A distinct frequency of fountain oscillation was identified but only at a nozzle height of 4·4 diameters.
Predicting the response of low-aspect ratio, flexible aircraft
Authors: Meirovitch L. , Tuzcu I. , McGrory W. D.
Published: February 2016

Accurate prediction of the response of low-aspect ratio, flexible aircraft requires correspondingly accurate modeling of the aircraft itself and of the aerodynamic forces, both respectable problems. Assuming that the wing can be modeled as a nonuniform plate, the discretisation process of choice is the finite element method (FEM), which demands a very large number of degrees of freedom for good accuracy. Moreover, accurate modeling of the aerodynamic forces acting on the aircraft suggests the use of computational fluid dynamics (CFD), which requires the use of an extremely large number of variables. On the other hand, feedback control design for the aircraft demands an aircraft model of relatively small order, so that the dimension of the FEM and CFD models must be reduced drastically. Based on physical considerations, reasonably accurate model reductions can be achieved, but a problem remains because the FEM and CFD grids are likely to differ from one another. It is shown in this paper how to achieve desirable model reductions for both the FEM and CFD and how to integrate the aerodynamic forces into the aircraft state equations. A numerical example demonstrates how the theory can be applied to the flight of a flexible aircraft. The analytical/computational approach developed here should permit parametric studies ultimately resulting in a reduction in the time required for aircraft design and flight testing.
Aircraft parameter estimation using a new filtering technique based upon a neural network and Gauss-Newton method
Authors: Peyada N. K. , Ghosh A. K.
Published: February 2016

A new parameter estimation method based upon neural network is proposed. The method proposed here uses feed forward neural networks to establish a neural model that could be used to predict subsequent time histories given the suitable measured initial conditions. The proposed neural model would not represent a generic flight dynamic model. The neural model in this case develops point to point fitting of the input and the output data. Thus, it could at best be referred to as flight dynamic model in restricted sense. Gauss-Newton method is then used to obtain optimal values of the aerodynamic parameters by minimising a suitable defined error cost function. The method has been validated using longitudinal and lateral-directional flight data of various test aircraft. The results thus obtained were compared with those obtained through wind tunnel test, or those obtained using Maximum likelihood and/or Filter error methods. Unlike, most of the parameter estimation methods, the proposed method does not require a prior description of the model. It also bypasses the requirement of solving equations of motion. This feature of the proposed method may have special significance in handling flight data of an unstable aircraft.
A calculation method for parametric design studies of V/STOL aircraft
Authors: Gologan C. , Broichhausen K. , Seifert J.
Published: February 2016

This paper provides a method that helps the aircraft designer to develop a performance constraint chart (PCC) for vertical/short takeoff and landing (V/STOL) aircraft that produce hybrid lift (static lift in combination with aerodynamic lift). The PPC provides a first estimation for the thrust-to-weight ratio (T0/MTOW) and wing loading (MTOW/S). The method is applicable to concepts, where static lift and main-engine thrust are coupled (e.g. the F-35B system, turbojet and lift-fan, coupled by a shaft) and to concepts, where static lift is produced by separate devices (e.g. lift-engines or other concepts for static lift). It includes thrust vectoring of the main engine.

The method includes the evaluation of certain flight stages, or segments, as short take-off and landing (STOL), vertical landing (VL), one engine inoperative (OEI) climb (for civil aircraft concept applications) and cruise, all these have to be considered. For each of these five segments, standard flight mechanics equations are extended by a static lift component, an augmentation ratio (a factor that describes the dependency of the thrust and the static lift, if coupled) and the thrust vectoring angle. Hence these equations are modified in a way that the aircraft designer can directly calculate T0/MTOW and MTOW/S for the performance requirements of each segment. Thus, an optimum design point can be selected. Inputs are aerodynamic coefficients, maximum lift coefficient of the wing, mass fraction from take-off to landing, additional static lift during take-off and landing, number of engines, augmentation ratio of the propulsion system and required take-off and landing field length.

A performance constraint chart for a JSF F-35B type aircraft is modelled to show the application of the method. As an application to civil aircraft a PCC and a parameter optimisation for the civil regional jet ‘HyLiner’ is presented.
Flight structures fundamental research trends and directions
Authors: Giurgiutiu Victor
Published: February 2016

The paper presents an overview of the fundamental research performed in the US in the field of flight structures under the sponsorship of the Air Force Office of Scientific Research (AFOSR). After presenting a general overview of AFOSR, the paper focuses on the structural mechanics program. Three large applications areas are considered: (a) future flight structures; (b) structural sustainment; (c) structural dynamics and vibration control. These three broad areas are covered at various levels of complexity and detail. Currently supported topics are presented and major funding and results are discussed. The paper ends with summary and conclusions.
In-situ impact-induced damage assessment of woven composite laminates through a fibre Bragg grating sensor network
Authors: Garrett R. C. , Peters K. J. , Zikry M. A.
Published: February 2016

Woven composite specimens with embedded fibre Bragg grating (FBG) sensor networks were impacted at low velocities, while global measurements of contact forces and dissipated energies were obtained from drop tower measurements, and local residual, post-impact strain values were obtained from the FBG sensors. Critical damage events were identified in the global data for these specimens and damage signatures in the residual strain data corresponding to these critical damage events were correlated. The results indicate that the full spectral scan information from the sensor network, although obtainable at a lower scan rate, provide more reliable residual lifetime information than average residual strains.
Flight control system design with H∞ loop-shaping approach through non-diagonal weights
Authors: Panesi R. , Mengali G.
Published: February 2016

This paper deals with the design methodology of multi-variable flight control systems through a H∞ loop-shaping technique. A new procedure for the design of non-diagonal pre-and post-compensators is described. In particular, important improvements over existing methods are introduced to both make the selection of weights easier and to contain the order of the resulting controller. The new procedure can be easily managed through suitable Matlab commands and functions, thus simplifying the whole algorithm implementation and providing an effective control system design with a minimum effort. Two typical design problems are addressed: a pitch pointing control system and a lateral controller for coordinated turns. In both cases, a good decoupling between existing channels is obtained by means of a non-diagonal pre-compensator which shapes the plant transfer function, and provides the desired response settling time. The design approach is particularly effective even for nominal plants with strong cross-coupling between channels. The design procedure is illustrated with the aid of a Matlab/Simulink model of a single seat fighter aircraft. We show that a trade-off between the conflicting requirements of fast response and moderate use of control surfaces can be easily managed by varying the constant terms of the diagonal post-compensator.
Increasing persistence of UAVs and MAVs through thermal soaring
Authors: Cowling I. D. , Willcox S. , Patel Y. , Smith P. , Roberts M.
Published: February 2016

This work looks to harness atmospheric energy through thermal soaring to optimise the flight persistence of Micro Air Vehicles (MAVs) and Unmanned Air Vehicles (UAVs). There are two key challenges when considering thermal soaring, the first being the locating of thermals and the second being the extraction of the maximum potential energy from the thermals. Thermal location is by no means an exact science with experienced glider pilots needing to consider many factors to improve the probability of encountering a thermal. As thermals are caused by the uneven heating of the Earth’s surface it is, however, possible to predict likely thermal locations. With the application of a suitable guidance algorithm which considers these ‘hot spots’ it is possible to increase the likelihood of encountering a thermal. Once a thermal is found it is important to attempt to extract the maximum energy from the thermal. To do this the vehicle needs to move quickly to the centre of the thermal. There are many potential techniques for thermal centring, some of which appear to be entirely contradictory to each other, the crucial factor determining the success of such a technique has been found to be the response time of the onboard sensors. This paper considers the many aspects of thermal soaring such as locating thermals, thermal detection and thermal centring. Five different thermal models are presented which are used to demonstrate the thermal centring techniques. Finally a commercial glider simulation package is used to demonstrate the control architecture and simulate a fully autonomous flight.
An aviation approach to space transportation
Authors: Ashford D.
Published: February 2016

This paper presents a strategy for developing the first orbital spaceplane soon and at low cost and risk. The paper then shows how this vehicle will introduce an aviation approach to orbital space transportation to replace the present missile paradigm, leading to far lower costs and improved safety.

To illustrate the potential benefits, the paper presents preliminary sizing and cost estimates of a simple lunar base. Even including the cost of developing the spaceplanes and other vehicles required, the total cost is about ten times less than that of present plans that use large new expendable launch vehicles. Timescales need not be greatly affected.
A methodology for optimisation design and analysis of stratosphere airship
Authors: Wang Q. , Chen J. , Fu G. , Duan D. , Zhao H.
Published: February 2016

This paper presents a methodology for studying the feasibility of stratosphere airship for high altitude long endurance missions and arriving at the baseline specifications of conventional configuration of stratosphere airship, given the performance and operational requirements. Based on this methodology, the AODAP platform (Airship Optimisation Design and Analysis Platform) was developed. Some innovative concepts used in AODAP that are different from previous methods and codes are presented. The shape optimisation of airship was introduced into the design process, and several optimum objectives can be selected including minimum drag, minimum weight and composite objective based on MDO (Multidisciplinary Design Optimisation). The methodology was validated for other design concepts previously developed for similar missions and also was compared to a low altitude vehicle. The baseline specifications of stratosphere airships designed for various shapes using this methodology are presented. The results of sensitivity analyses for a specified airship are discussed, and the sensitivity of airship length with some critical parameters including area density of envelope fabric, area density of solar cell, efficiency of solar cell and efficiency of fuel cell for the specified shape is also provided.
Analysis of helicopter vibratory hub loads alleviation by cyclic trailing-edge blade flap actuation
Authors: Gennaretti M. , Molica Colella M. , Bernardini G.
Published: February 2016

The aim of the present work is the investigation about the use of blade trailing-edge flaps for the reduction of vibratory loads arising at the hub of helicopter main rotors in forward flight. The alleviation of these loads is achieved through multicyclic higher harmonic actuation of the blade flaps, which is related to measured vibratory loads amplitude. The feedback control law is obtained by an optimal control process based on the minimisation of a cost function, under the constraint of compatibility with the nonlinear equations governing blade aeroelasticity. In the numerical investigation concerning a four-bladed rotor in level flight conditions, a computationally efficient local controller methodology is applied, with the attention focused on the effectiveness of the control algorithm, along with its robustness with respect to differences (existing in real applications) between the aeroelastic models used for control law synthesis and validation.