Browsing by Author "Fielding, John"

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    Acquisition cost estimating methodology for aircraft conceptual design
    (Cranfield University, 2008) Zhao, Tienan; Fielding, John
    The research was conducted in the light of a training programme which will train a total of 150 engineers of AVIC I in Cranfield University during a period of 3 years. Cost has become an essential driver to aircraft design, as well as performances due to either the limited defence budget or competitive airline market. Consequently, knowing the possible cost prior to making actual expenditure will help managers to make proper decisions and allocate resources efficiently, and designers to optimize their work. Existing aircraft cost estimating models are outdated and mainly based on a database including both military and civil aircraft with various missions. This research concentrated on commercial jet aircraft and was to develop a suitable acquisition cost estimating methodology for conceptual design from a commercial aircraft manufacturer’s perspective. The literature reviewing took a comprehensive overview of some widely-applied cost estimating methods: Analogy, Parametric, Bottom-up, Feature-based costing, Activitybased costing (ABC), Expert judgement, and etc. Some practical cost models were also reviewed to learn the application of cost estimating in the aerospace industry. Then, analogy and parametric approaches were selected to perform the methodology development considering the limited data available at the conceptual design phase. An investigation was deployed to identify the actual problems in practice. The results helped to recognize the needs of industry. Also, the preparation works for development are presented to understand the environment. With subjective judgement and statistical techniques, a series of cost estimating relationships (CERs) were achieved, in which some historic explanatory parameters remained or were eliminated, and some new ones introduced. Size of aircraft became another variable besides weight. As to engines, all developed explanatory variables have been revealed in prior researches. The validation of CERs proves that they can provide reliable cost estimates with high accuracy and can be applied to conceptual design. In addition, a case study was conducted using a baseline aircraft defined in the group design project (GDP) and presents cost forecasting for the proposed aircraft. At last, discussion and conclusion presents an overview of the research. A framework for cost estimating system can be educed. Also, the future work is proposed for in-depth research.
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    Actuation technology for flight control system on civil aircraft
    (Cranfield University, 2009-01) Xue, L; Lawson, C. P.; Fielding, John
    This report addresses the author’s Group Design Project (GDP) and Individual Research Project (IRP). The IRP is discussed primarily herein, presenting the actuation technology for the Flight Control System (FCS) on civil aircraft. Actuation technology is one of the key technologies for next generation More Electric Aircraft (MEA) and All Electric Aircraft (AEA); it is also an important input for the preliminary design of the Flying Crane, the aircraft designed in the author’s GDP. Information regarding actuation technologies is investigated firstly. After initial comparison and engineering consideration, Electrohydrostatic Actuation (EHA) and variable area actuation are selected for further research. The tail unit of the Flying Crane is selected as the case study flight control surfaces and is analysed for the requirements. Based on these requirements, an EHA system and a variable area actuation system powered by localised hydraulic systems are designed and sized in terms of power, mass and Thermal Management System (TMS), and thereafter the reliability of each system is estimated and the safety is analysed. These two systems are then compared in fuel penalty, safety, maintenance and installation, cost, risk and certification. A conventional Fly-By-Wire (FBW) actuation system is used as the reference case. The results show that both the EHA system and the variable area actuation system are feasible for the FCS on civil aircraft. The EHA system is proved to be quite efficient in power consumption and mass reduction. However, the reliability of EHA needs to be improved and the TMS of this system may lead to an increase in aircraft drag. The variable area actuation system demonstrates that it can significantly reduce the system design point and system size; while the localised hydraulic system is not as efficient as a centralised hydraulic system. Finally, a variable area actuation system powered by the centralised hydraulic systems is suggested for the FCS on civil aircraft and the Flying Crane. A variable area actuation system powered by localised hydraulic systems is recommended as the first step towards MEA and AEA in the future.
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    The aerodynamic design and optimization of a wing-fuselage junction fillet as part of a multi-disciplinary optimization process during the early aircraft design stages
    (Cranfield University, 1996-06) Hadjiilias, Hippokrates A.; Fielding, John
    An attempt to minimize interference drag in a wing-fuselage junction by means of inserting a fillet is presented in this thesis. The case of a low-wing com- mercial transport aicraft at cruise conditions is examined. Due to the highly three dimensional behaviour of the flow field around the junction, a thin-layer Navier-Stokes code was implemented to estimate the drag forces at the junc- tion. Carefully selected design variable combinations based on-the theory of Design of Experiments constituted the initial group of feasible cases for which the flow solver had to be run. The drag values of these feasible cases were then used to create a second order response surface which could predict with rea- sonable accuracy the interference drag given the value of the design variables within the feasible region. A further optimization isolated the minimum in- terference drag combination of design variable values within the design space. The minimurn interference drag combination of design variable values was eval- uated numerically by the flow solver. The prediction of the response surface and the numerical value obtained by the flow solver for the interference drag of the optimal wing-fuselage combination differed by less than five percent. To demonstrate the ability of the method to be used in an interdisciplinary analysis and optimization program, a landing gear design module is included which provides volume constraints on the fillet geometry during the fillet sur- face definition phase. The Navier Stokes flow analyses were performed on the Cranfield Cray su- percomputer. Each analysis required between eight to twelve CPU hours, and the total CPU time required for the optimization of the six variable model described in the thesis required thirty Navier Stokes runs implementing the Design of Experimens and Surface Response Methodology implementation. For comparison, a typical optimization implementing a classical conjugate di- rections optimizer with no derivative information available would probably require more than forty iterations. Both the optimization and the flow solver results are discussed and some recommendations for improving the efficiency of the code and for further ap- plications of the method are given.
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    Aircraft conceptual design modelling incorporating reliability and maintainability predictions
    (Cranfield University, 1996-03) Vaziry-Zanjany , Mohammad Ali (F); Fielding, John
    A computer assisted conceptual aircraft design program has been developed (CACAD). It has an optimisation capability, with extensive break-down in maintenance costs. CACAD's aim is to optimise the size, and configurations of turbofan-powered transport aircraft. A methodology was developed to enhance the reliability of current aircraft systems, and was applied to avionics systems. R&M models of thermal management were developed and linked with avionics failure rate and its maintenance cost prediction methods. The impact of the environmental control system, and engine-provided bleed flow was also modelled and incorporated into CACAD. The program showed the ARINC 600 & 408A flow rates to the avionics bay, and to the deck instruments may both profitably be increased by 50%. This keeps the direct operating cost (DOC) increase at bay for long-range passenger aircraft, and offers a reduction of up to 1% in DOC for the short to medium range passenger aircraft. A methodology was developed to model all aspects of future high risk technologies, with special consideration given to reliability, maintainability, and development cost (R, M&D) predictions as applied to variable camber wings (VCW). Many aspects of VCW were modelled. These included different types of drag saving due to chord- wise, as well as span-wise camber variation. Models were also derived for mass, maintenance cost, and extra development cost increments for wing trailing edge devices, flight control, and hydraulic systems. On incorporation into CACAD, a reduction in DOC of up to 3.5% was predicted. The VCW technology were evaluated for DOC improvements, against a number of existing, future, and derivative aircraft, under different sensitivity conditions. R, M&D predictions were shown to be decisive in addressing the feasibility of a new technology. The R&M predictions of the whole study shows that, long range, low to medium capacity derivative transport aircraft are most appropriate for the VCW technology, and the short to medium range, low to medium capacity aircraft are most suitable for reliability enhancement projects of aircraft advanced systems.
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    Aircraft systems design methodology and dispatch reliability prediction
    (Cranfield University, 2005) Bineid, Mansour; Fielding, John
    Aircraft despatch reliability was the main subject of this research in the wider content of aircraft reliability. The factors effecting dispatch reliability, aircraft delay, causes of aircraft delays, and aircraft delay costs and magnitudes were examined. Delay cost elements and aircraft delay scenarios were also studied. It concluded that aircraft dispatch reliability is affected by technical and non-technical factors, and that the former are under the designer's control. It showed that the costs of aircraft delays are very significant and must be reduced. Cont/d.
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    An approach to configuration design synthesis of subsonic transport aircraft using artificial intelligence techniques
    (1991-12) Pasaribu, H. M.; Fielding, John
    This thesis outlines a computer system developed to tackle the configuration design synthesis of subsonic transport aircraft. The system provides an interactive design environment which combines the reasoning process of the aircraft configuration definition and the numerical analyses that lie behind the reasoning. The system applies Artificial Intelligence (AI) techniques to the configuration analysis. This gives the system the capability to reason with the configuration choices. The system is built in modules, with each module is clearly separated to deal with a complete analysis in a specific aspect of design. The integration of the modules is done through an intelligent interface and a common database. The interface also incorporates AI techniques in deciding the sequence of execution of the modules and the processing of the input/output data for a particular module. The interface permits the sharing of information among the modules and supports modularity and flexibility of the system for future development. Since each module is independent, it can be easily modified or replaced without disturbing the balance of the system. An extensive library of application programs is included in the engineering analysis module which enable detailed analysis to be performed. The system is equipped with a simplified database management and a special purpose graphics module which is extensively used for the presentation of the output. The system has been validated and tested. It can handle both propeller driven and jet engined aircraft. An example of the case studies is presented. The improvement of the system for future development is also considered. These include the extension of the knowledge base for dealing with problems in other modules, the enhancement of the application programs in the engineering module, and a possible interface with an established Computer Aided Drafting (CAD) system.
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    ASTOVL Combat Aircraft Design Synthesis and Optimization
    (Cranfield University, 1992-01) Kehayas, N.; Fielding, John
    This thesis presents the development of a Baseline Configuration for an Advanced Short Take-Off and Vertical Landing (ASTOVL) Combat Aircraft, the Design Synthesis and coding of this Baseline Congiguration (Code VERTI), the interfacing of the Design Synthesis Code VERTI with the Optimizer code RQPMIN and the optimization of the Baseline Configuration. The background and the objectives of this Research Programme are initially examined. The evaluation of the ASTOVL Combat Aircraft Baseline Configuration is then described, including all the problems, assumptions, choices and compromises that led to the specific configuration. The development of the Design Synthesis and the Code VERTI then follow, where the methodology used, the techniques adopted and the code operation are explained. A full description of the Design Synthesis is included as an appendix. Finally, the interfacing of Code VERTI with the optimizer RQPMIN and the optimization of the Baseline configuration are presented. The problems and difficulties of the RQPMIN operation are thoroughly discussed. The RQPMIN- VERTI code is used to optimize the initial Baseline Configuration and an optimization example is provided in appendix form. The optimized Baseline Configuration is partly validated against two ASTOVL combat aircraft designs. In addition to the optimization with the aircraft empty mass as objective function, a search for a better objective function is attempted.
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    Conceptual and preliminary design methods for use on conventional and blended wing body airliners
    (Cranfield University, 2019-02-19 11:40) Smith, Howard; Fielding, John
    Transcript of John Fielding and Howard Smith's 1999 lecture to Court, Cranfield University.
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    Conceptual design and optimization methodology for box wing aircraft
    (Cranfield University, 2012-06) Jemitola, Paul Olugbeji; Fielding, John
    A conceptual design optimization methodology was developed for a medium range box wing aircraft. A baseline conventional cantilever wing aircraft designed for the same mis- sion and payload was also optimized alongside a baseline box wing aircraft. An empirical formula for the mass estimation of the fore and aft wings of the box wing aircraft was derived by relating conventional cantilever wings to box wing aircraft wings. The results indicate that the fore and aft wings would use the same correction coe cient and that the aft wing would be lighter than the fore wing on the medium range box wing aircraft because of reduced sweep. As part of the methodology, a computational study was performed to analyze di erent wing/tip n xities using a statically loaded idealized box wing con guration. The analy- ses determined the best joint xity by comparing the stress distributions in nite element torsion box models in addition to aerodynamic requirements. The analyses indicates that the rigid joint is the most suitable. Studies were also performed to investigate the structural implications of changing only the tip n inclinations on the box wing aircraft. Tip n inclination refers to the angle the tip n makes to the vertical body axis of the aircraft. No signi cant variations in wing structural design drivers as a function of tip n inclination were observed. Stochastic and deterministic optimization routines were performed on the baseline box wing aircraft using the methodology developed where the variables were wing area, av- erage thickness to chord ratio and sweep angle. The conventional aircraft design showed similar performance and characteristics to the equivalent in-service aircraft thereby pro- viding some validation to the methodology and the results for the box wing aircraft. Longitudinal stability investigations showed that the extra fuel capacity of the box wing in the ns could be used to reduce trim drag. The short period oscillation of the conventional cantilever wing aircraft was found to be satisfactory but the box wing aircraft was found to be unacceptable hence requiring stability augmentation systems. The eld and ight performance of the box wing showed to be better than the conventional cantilever wing aircraft. Overall, the economic advantages of the box wing aircraft over the conventional cantilever wing aircraft improve with increase in fuel price making the box wing a worthy replacement for the conventional cantilever wing aircraft.
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    Conceptual design methodologies appropriate to supersonic business jets
    (2018-11) Sun, Yicheng; Smith, Howard; Fielding, John
    This project aims to study the status of the issues related to Supersonic Business Jet (SSBJ) conceptual design, to develop design methodologies appropriate to SSBJs, and to explore the design space of low-boom low-drag supersonic transport concepts. The design model appropriate to SSBJs is developed in the Cranfield multidisciplinary design analysis and optimization environment – GENUS. The mass breakdown, engine model, aerodynamic analysis, stability and control, and sonic boom prediction methods are developed in the GENUS framework. Optimizers help to explore the design space based on the model. Through the research, the current supersonic transport concepts are analysed and the supersonic natural laminar flow wing concept is found to leave little space for sonic boom mitigation. The most significant finding is the low-boom solution through the geometry shaping to the volume and lift effects. The low-drag requirement is not necessarily contradicted by the low-boom requirement. The low-boom optimization achieves a sonic boom reduction from 2.6 psf to 0.6 psf and the L/D increase from 8.96 to 10.67. The low-drag optimization achieves a L/D increase from 8.96 to 10.81 and sonic boom reduction from 2.6 psf to 1.0 psf. A low-boom low-drag SSBJ and a low-boom low-drag supersonic airliner concepts are designed in a multidisciplinary view. Pdf available on request and Howard Smith's permission.
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    Conceptual design methodologies for waterborne and amphibious aircraft
    (Cranfield University, 1999) Chicken, S. H.; Fielding, John
    This study is laid out in 8 self-explanatory sections. The Introduction sets the scene for the thesis by describing the reasoning behind the study, defines terms and introduces the reader to the markets for amphibious aircraft which drive the design requirements. An overall floatplane design methodology is developed. The advantages and disadvantages of the 2 practical float configurations are identified, which result in a basic configuration choice methodology. A method of initially estimating float dimensions and mass for a required displacement is developed from existing references and the aircraft and float databases. Initial float support structure design solutions are proposed based, again, on the information from the databases. A method of positioning the resultant float and structure configuration relative to the existing land-based aircraft centre of gravity is then developed using existing guidance on lateral and longitudinal water-borne static stability and the aircraft database. Guidance on the initial purchase price of floats is gained from a study of commercially available items. The changes in performance due to fitting floats to a conventional aircraft are studied along with a drag comparison study of the main configurations. The work on flyingboats develops an overall flyingboat design methodology which identifies key areas where design methods are required. These methods are developed leading to initial configuration choice methodologies based on a series of generalised mass, configuration and role classifications. Having decided on the overall configuration, tools are developed to choose the method of providing on-water lateral stability and to complete the initial sizing of that choice. A method of estimating initial planing bottom dimensions is developed along with step position and configuration. Tools to estimate the mass of flyingboat-specific items are developed including planing bottom structure and the choice of lateral stability method. Knowing the mass and configuration of the flyingboat allows spray estimation and detailed on-water static stability calculations to be completed to check the acceptability of the initial configuration and dimensions. Performance estimation methods including take-off and landing, aerodynamic drag and on-water dynamic stability are proposed. Logistic support infrastructure, safety and water loading are common to both floatplanes and flyingboats and these are discussed in a separate section, along with a method of allocating values to amphibious aircraft design attributes to measure the success of the design. The methodologies are then used to design 5 floatplanes and 5 flyingboats based on a crosssection of relevant aircraft specification types. This use of the methodologies illustrates that the concept of a linked series of tools to complete the rapid conceptual design of an amphibious aircraft has been successfully achieved. A discussion chapter summarises the key discoveries in each of then former chapters and a conclusion details how the study's aim to develop integrated conceptual design methodologies for waterborne and amphibious aircraft has been successfully achieved. The study's contribution to knowledge, which includes mass, sizing, performance and cost equations for both floatplanes and flyingboats, are also detailed. A list of further work is included which concentrates on the need for further empirical information to increase confidence in the methodologies. A comprehensive bibliography of relevant texts is included.
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    The conceptual design of novel future UAV's incorporating advanced technology research components
    (Cranfield University, 2011) Clarke, Adrian James; Fielding, John
    There is at present some uncertainty as to what the roles and requirements of the next generation of UAVs might be and the configurations that might be adopted. The incorporation of technological features on these designs is also a significant driving force in their configuration, efficiency, performance abilities and operational requirements. The objective of this project is thus to provide some insight into what the next generation of technologies might be and what their impact would be on the rest of the aircraft. This work involved the conceptual designs of two new relevant full-scale UAVs which were used to integrate a select number of these advanced technologies. The project was a CASE award which was linked to the Flaviir research programme for advanced UAV technologies. Thus, the technologies investigated during this study were selected with respect to the objectives of the Flaviir project. These were either relative to those already being developed as course of the Flaviir project or others from elsewhere. As course of this project, two technologies have been identified and evaluated which fit this criterion and show potential for use on future aircraft. Thus we have been able to make a contirubtion knowledge in two gaps in current aerospace technology. The first of these studies was to investigate the feasibility of using a low cost mechanical thrust vectoring system as used on the X-31, to replace conventional control surfaces. This is an alternative to the fluidic thrust vectoring devices being proposed by the Flaviir project for this task. The second study is to investigate the use of fuel reformer based fuel cell system to supply power to an all-electric power train which will be a means of primary propulsion. A number of different fuels were investigated for such a system with methanol showing the greatest promise and has been shown to have a number of distinct advantages over the traditional fuel for fuel cells (hydrogen). Each of these technologies was integrated onto the baseline conceptual design which was identified as that most suitable to each technology. A UCAV configuration was selected for the thrust vectoring system while a MALE configuration was selected for the fuel cell propulsion system. Each aircraft was a new design which was developed specifically for the needs of this project. Analysis of these baseline configurations with and without the technologies allowed an assessment to be made of the viability of these technologies. The benefits of the thrust vectoring system were evaluated at take-off, cruise and landing. It showed no benefit at take-off and landing which was due to its location on the very aft of the airframe. At cruise, its performance and efficiency was shown to be comparable to that of a conventional configuration utilizing elevons and expected to be comparable to the fluidic devices developed by the Flaviir project. This system does however offer a number of benefits over many other nozzle configurations of improved stealth due to significant exhaust nozzle shielding.The fuel reformer based fuel cell system was evaluated in both all-electric and hybrid configurations. In the ell-electric configuration, the conventional turboprop engine was completely replaced with an all-electric powertrain. This system was shown to have an inferior fuel consumption compared to a turboprop engine and thus the hybrid system was conceived. In this system, the fuel cell is only used at loiter with the turboprop engine being retained for all other flight phases. For the same quantity of fuel, a reduction in loiter time of 24% was experienced (compared to the baseline turboprop) but such a system does have benefits of reduced emissions and IR signature. With further refinement, it is possible that the performance and efficiency of such a system could be further improved. In this project, two potential technologies were identified and thoroughly analysed. We are therefore able to say that the project objectives have been met and the project has proven worthwhile to the advancement of aerospace technology. Although these systems did not provide the desired results at this stage, they have shown the potential for improvement with further development.
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    Conceptual design synthesis and multidisciplinary optimisation of unmanned combat aerial vehicles.
    (2019-12) Sepulveda Palacios, Eduardo; Smith, Howard; Fielding, John
    The purpose of this research is to investigate and develop conceptual design methodologies and computational tools appropriate to the design and analysis of low-observable Unmanned Combat Aerial Vehicles (UCAVs), performing a wide variety of missions, with various payload and performance requirements, as well as a wide range of operational constraints, from subsonic to high supersonic flight regimes. Undoubtedly, unmanned aircraft have transformed many aspects of aeronautics and aviation, with military applications often leading these transformational efforts. UCAVs have emerged as a potential strategy to counter technological, operational, and economical challenges to the future of aerial warfare. These challenges include an aging fleet of 4th generation fighters, the deployment of new, advanced 4+ and 5th generation platforms, the reported high vulnerability of current unmanned aerial vehicles, as well as the future development of hypersonic vehicles and weapons. In order to investigate future aircraft configurations, the GENUS aircraft design environment was envisioned by Prof. Howard Smith at Cranfield University’s Aircraft Design Group in 2012. This framework relies on a central architecture with high degrees of modularity and flexibility capable of designing, analysing, and optimising several species of aircraft with similar analysis tools, revealing the real differences and potential advantages of new designs. Mass estimation, propulsion, aerodynamics, performance, radar cross section estimation, and aero-thermal analysis tools have been integrated into the GENUS framework in order to investigate the design space of UCAVs. Validation of these methods has been hampered due to the often restricted access to quality data of UCAVs and similar configurations against which to compare and from which to generate higher fidelity models. Specific steps for improving the accuracy of the methods in the future have been identified and proposed in §9.2. Design space explorations performed in this research include a mission parameter trade study for subsonic UCAVs in Hi-Lo-Hi missions, the conceptual and preliminary design of a UCAV platform with performance matching that of current 5th generation fighters, a fully supersonic deep-interdiction mission trade study, and a high-supersonic (M ≥ 3.0) carrier-based UCAV for time-critical strike missions.
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    Design methodology for wing trailing edge device mechanisms
    (Cranfield University, 2007-04) Martins Pires, Rui Miguel; Fielding, John
    Over the last few decades the design of high lift devices has become a very important part of the total aircraft design process. Reviews of the design process are performed on a regular basis, with the intent to improve and optimize the design process. This thesis describes a new and innovative methodology for the design and evaluation of mechanisms for Trailing Edge High-Lift devices. The initial research reviewed existing High-Lift device design methodologies and current flap systems used on existing commercial transport aircraft. This revealed the need for a design methodology that could improve the design process of High-Lift devices, moving away from the conventional "trial and error" design approach, and cover a wider range of design attributes. This new methodology includes the use of the innovative design tool called SYNAMEC. This is a state-of-the-art engineering design tool for the synthesis and optimizations of aeronautical mechanisms. The new multidisciplinary design methodology also looks into issues not usually associated with the initial stages of the design process, such as Maintainability, Reliability, Weight and Cost. The availability of the SYNAMEC design tool and its ability to perform Synthesis and Optimization of mechanisms led to it being used as an important module in the development of the new design methodology. The SYNAMEC tool allows designers to assess more mechanisms in a given time than the traditional design methodologies. A validation of the new methodology was performed and showed that creditable results were achieved. A case study was performed on the ATRA - Advance Transport Regional Aircraft, a Cranfield University design project, to apply the design methodology and select from within a group of viable solutions the most suitable type of mechanism for the Variable Camber Wing concept initially defined for the aircraft. The results show that the most appropriate mechanism type for the ATRA Variable Camber Wing is the Link /Track Mechanism. It also demonstrated how a wide range of design attributes can now be considered at a much earlier stage of the design.
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    Design synthesis for Canard-Delta combat aircraft
    (Cranfield University, 1987-12) Serghides, V. C.; Fielding, John
    This . thesis pr*esents the development of a computerized Design Synthesis for canard-delta combat aircraft. This is complementary to and followas the philosophy of an existing RAE system for conventional combat aircraft with swept wings (Ref. 1). The background to the work and the Research Progra objectives and limitations are initially examined. The design of a baseline canard-delta combat aircraft is then described together with all the assumptions and decisions which led to its final configuration. The philosophy behind the progressive evolution of the aircraft geometry and packaging modules from the baseline configuration, is explained in detail. The development of detailed modules'for the estimation of the aircraft aerodynamics and performance is then presented. A full description of the investigations into the effects of canard-delta interference on the aircraft aerodynamics, is also included. The mathematical content of the aircraft geometry, packaging, aerodynamics and performance modules is presented separately in the appendices, in greater detail. The development and architecture of the Design Synthesis and graphics programs are finally presented and the program operation is described with the aid of flow- charts. A comprehensive user's manual and a design example are also provided.
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    Development of a combat aircraft operational and cost-effectiveness design methodology
    (Cranfield University, 2005-02) Nilubol, Otsin; Fielding, John
    This study set out to develop an aircraft design methodology, which gives com- bat aircraft more operational and cost-effectiveness by considering these factors early in the design process. In this methodology, an aircraft will be considered as a sub-system of an overall system, representing an entire operation scenario. Measures of operational and operational cost-effectiveness indicate the quality of, and relationships between, the major design aspects; i. e. susceptibility, vulnerability, reliability, maintainability, and operational cost. These measures are functions of aircraft measures of performance and measures of effectiveness. A mission operation simulation was developed as the transfor- mation tool, to performance and effectiveness measures. The measures of aircraft performance developed in this methodology have been evalu- ated by simple, yet sufficient, models because of the paucity of available data, information and the appropriateness of such assessment methods during the early design stages. An aircraft performance in susceptibility terms is measured both in the forms of probability of detection, which is predicted through its radar cross section (RCS), and probability of hit. The RCS prediction model in this study generally uses an aircraft's external shape, and the probability of hit is also evaluated from the aircraft presented areas. The probability of kill is a measure of aircraft performance used the vulnerability design methods. This value relates directly to number and sizes of the critical components installed in the aircraft, and their layout. The modification of the critical component layout can directly affect the aircraft probability of kill. In this study, only two major threat types are considered; i. e. contact and proximity warheads. Manoeuvrability probability has been introduced, and been used together with the sus- ceptibility and vulnerability probabilities to predict the overall operational survivability probability in this study. Aircraft reliability and some maintainability probabilities are predicted by using avail- able unclassified data and fundamental aircraft design parameters and variables by dint of statistical analysis and the Pareto principle. Operational cost in this methodology is calculated throughout the aircraft Life Cycle Cost (LCC) by averaging the total operation cost over the total number of operational aircraft in one base and total number of flying hours for an aircraft fleet's entire life. The average operation cost in conjunction with the number of aircraft lost and of weapons released during the mission simulation gives the total operational cost for the overall scenario. An alternative method used to integrate all probabilities into the operation mission simulation is by using the reliability block diagram technique in conjunction with an event tree diagram. The Monte Carlo simulation technique has been used to generate more accurate results by means of random value usage. Most results from the operation mission simulation are in the form of integer num- bers; therefore, the genetic algorithm optimisation method was mainly used in this study. However, the gradient-based optimisation method can also be used to give approximate predictions. The results from the optimisation can finally be used as examples of how to design a combat aircraft for operational and cost-effectiveness.
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    The development of a design methodology for large cargo aircraft
    (2008-11) Mederer, A.; Fielding, John
    Detailed specialist knowledge of pre-design, design, aerodynamics, engine performances and flying performances is necessary for the pre-design of transport aeroplanes. In this paper, studies are described which provide the main detailed information on the above-mentioned specialist topics. All studies consists of a problem with a suitable solution and the associated results. The studies are part of the overall task “Systematic design study on a number of configurations for large aircraft types, in particular for cargo aeroplanes”. As part of the overall task, a design method was developed which is very user-friendly and which is suitable for the design of any aeroplane configurations, in particular for configurations of large passenger or transport aeroplanes. This thesis version shows how 11 transport aeroplane configurations of very different types can be drawn up. The configuration results are shown on a scale of 1 : 500 and can be directly used for more detailed studies, as they are based on calculations. 4 of the first 5 transport aeroplane configurations are basic configurations and were scaled between 200 to 10001 . Important flying performance characteristics were calculated for the configurations by the use of 8 PC programs additionally developed for this purpose. Validity studies have shown that the described design method provides useful results. The main result of the method is that very different transport aeroplane versions can be developed and compared in terms of flying performances. Currently, only a few very complex design methods are offered elsewhere which have the disadvantage that they are only intended for one aeroplane version. So far, the design method described in this method is fully applied to the first five configurations. A next step could be to also investigate the additional six configurations listed here with the method.
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    Development of a design methodology for transport aircraft variable camber flaps suitable for cruise and low-speed operations
    (Cranfield University, 2003-02) Ammoo, M. S.; Fielding, John
    This thesis describes the development of a generic design methodology for variable camber flap systems for transport aircraft, intended to be used for cruise and low-speed operations. The methodology was structured after several revisions were performed on conventional high-lift device design methodologies for existing transport aircraft. The definition and detail explanations are given at every phase of the methodology. A case study was performed in order to give an example of the implementation of the methodology where a transport aircraft called A TRA, a design study from previous PhD report, was taken as a model. Experimental work could not be performed, due to budget constraints, so the case study was only carried out using computer-based analyses. Software packages such as MSES-code (a Computational Fluid Dynamic software), CATIA and PATRANINASTRAN were used for this case study to analyse aerodynamic characteristics, layout as well as simulation and structure analyses respectively. The results obtained showed that it was practically feasible to deploy such a high-lift device to transport aircraft when the effect from aerodynamic loads gave minimum effect on structural deformation. The deflections of the flap as well as spoilers under critical loads were below the allowable limits, which had a minimal effect due to the additional lift force generated from the movable surfaces.
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    Development of an approach and tool to improve the conceptual design process of the wing box structure of low-subsonic transport aircraft
    (Cranfield University, 2009-02) Syamsudin, Hendri; Fielding, John
    To produce a better airframe design, it is imperative to investigate the problems of design and manufacturing integration early on at the conceptual design stage. A new design approach and support tool is required which will aid the designer in future product development. This is a particular necessity in the current context of increasing complexity and challenging economic situations. The present work focuses on the development of a design approach and design aids for designing metallic wingbox structures of low-subsonic transport aircraft with small wing sweepback angles. Its aims are two-fold: to assist in producing alternative structural concepts, and to capture the effects of new materials and manufacturing processes on weight and cost. It will form the basis for selecting the structural concept at the early stage of the design process. The target users of this design approach and tools are relatively inexperienced structural designers and students. The developed process and tools are quite general in their application as they use stand-alone modules which can be employed separately or jointly with existing techniques and tools used by industry, research centres and academia. A comparison of the result from the developed analytical tools against a detailed study undertaken by an aircraft company on the original configuration was made. It showed stress analysis and sizing results that were within a 10% margin. A case study was performed to investigate the reduction of Direct Operating Cost (DOC) of a turboprop transport aircraft by redesigning the wingbox structure. Weight reductions of wing box structure of 16% were achieved using new configurations and advanced metallic materials. The purchase price of the aircraft could also be reduced through use of cheaper labour and new manufacturing processes. These cost savings, if converted into DOC reductions, are only 0.36% of DOC due to fuel saving and 0.25% of DOC due to manufacturing cost reduction for the wingbox structure only. It is obvious that the overall DOC reduction is the result of the total impact of relative DOC effects due to fuel cost saving, material prices, labour rates, and manufacturing process improvements. Within the range of the calculated parameter values, the overall DOC reductions could be as much as 0.61% relative DOC. It appears that fuel prices, material cost and labour rates give greater impacts on DOC than high speed machining processes. Due to the use of advanced aluminium, maintenance cost is also predicted to be less. It has better fatigue life and fracture toughness than the standard aluminium and therefore will increase the aircraft maintenance periods for inspection and repair due to slower crack damage growth. This cost saving will contribute in reducing the life cycle cost of the aircraft. In addition, the number of crack stoppers could be reduced, therefore minimising weight and manufacturing cost. These benefits however have not been analysed.
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    ItemOpen Access
    Development of safety and reliability prediction methodology for aircraft systems with common-cause failures
    (Cranfield University, 1996-04) Nam, G. W.; Fielding, John
    A methodology has been developed for predicting aircraft safety and reliability incorporating both C.C.F.s(Common-Cause Failures), and phased missions. Failure behaviour of an aircraft, or its systems due to both independent failures and C.C.F.s are modelled by the Markov process, and simulated using Monte Carlo method with the robust variance reduction techniques. Prediction of safety and reliability is made through discrete-event simulation of aircraft operations. Validation was made by comparing the predicted safety and reliability results of B767 ETOPS aircraft propulsion system, using the developed methodology, to those obtained from the analysis of real operation data. The credibility and the accuracy of the developed methodology are shown through the comparison of results. A case study was conducted for investigating the safety and reliability of the propulsion system of two-, three- and four-engined aircraft using the developed methodology. The case study produced valuable results concerning the safety of ETOPS flight, which were not previously known. These results were able to be used for further trade studies of aircraft design to decide the number of engines, and also for establishing new regulations for ETOPS flights.