Dissertations / Theses on the topic 'Aircraft modelling'
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1
Rubin, Felix. "Modelling & Analysis of a TiltWing Aircraft." Thesis, KTH, Flygdynamik, 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-244832.
Full textAbstract:
The aim of this report is the investigation of a hybrid vertical take-off and landing (VTOL) tilt wing aircraft which is in development at the company Dufour Aerospace. Using a model, programmed in MATLAB® different stages of flight can be simulated and investigated. Maininvestigation area of this report is the transition between cruise and hover conditions of the aircraft.The simulation is based on the six-degree-of-freedom nonlinear equations of motion for aircraft modified for tilt wing operation. The model characteristics have been determined using various CFD programs, wind tunnel data, as well as numerical and handbook methods.The main focus of modeling lies on the static longitudinal aerodynamic coefficients, the propeller and engine coefficients as well as a propeller slipstream model. Furthermore lateral directional aerodynamic coefficients and dynamic effects and a tail blower (Notar) system are modeled.As results, aerodynamic characteristics of the wing in the propeller slipstream are shown and discussed and the transition conditions are investigated by ’trimming’ the model at equilibrium points over its speed range and analyzing the resulting power requirements.
2
Harasani, W. "Aircraft conceptual design decision through operational modelling." Thesis, Cranfield University, 2005. http://dspace.lib.cranfield.ac.uk/handle/1826/11093.
Full textAbstract:
Aircraft manufacturing is not only a difficult business but also a very competitive one,
the consequences of any drop in sales would cost billions, loss of jobs, and maybe an
economical failure. Therefore, concentrating on just flight performance and adding new
technologies just because they exit is not enough to win the airlines attention, especially
the flow cost carriers.
Manufactures must be able to convince operators that the application of a new design or
technology will produce a favourable change in the bottom line of their balance sheets
and not just a reduction in fuel burn.
Aircraft designers must put more emphasis on what happens to the aircraft after it leaves
the assembly line, through the designed life operation cycle of the aircraft with the airline
customer, quality should be built in to the aircraft. Knowing what are the airline's
concerns, how the aircraft with a given design behaves, and the issues that the airline has,
is vital.
Firstly, it is important to know what are the issues that the airline has, the costumer
(airlines) needs are identified, and, since fleet planning is the top level decision making
department in the airline in which a decision is made to buy one aircraft over the other, it
is important to understand the process and the elements that are involved in fleet
planning. So fleet planning was studied.
Second different technologies for the design have been looked at and selected. Then the
aircraft, airline, airport, and air traffic control are studied, as well as the interaction
between them.
A key element of the research is a simulation program DEBOS that has been built to see
the impact of the different design technologies and concepts through the operation of a
simulation fleet size of 23 aircraft. The Boeing777 aircraft has been chosen to be the base
line of the study.
Finally, it was found that a given technology with improved performance, or a new
concept, would improve the aircraft attractiveness only if it has better life cycle behaviour
characteristics.
3
Poudel, Minesh. "Aircraft emergency evacuation : analysis, modelling and simulation." Toulouse 2, 2008. http://www.theses.fr/2008TOU20026.
Full textAbstract:
Cette thèse s’intéresse à l’évacuation d’urgence des avions et plus particulièrement à la conception d’un simulateur numérique capable de représenter de façon réaliste ce processus afin de contribuer à la certification de configurations et de procédures d’évacuation d’urgence pour les avions gros porteurs. Cette thèse est composée de deux grandes parties. Dans la première partie, il s’est agi d’identifier le problème, de réaliser un état de l’art et de caractériser le comportement des passagers pendant l’évacuation. Dans la deuxième partie de la thèse il s’est agi de concevoir les élément constitutifs d’un simulateur d’évacuation d’urgence des aéronefs. Après avoir analysé les modèles existants et revu les méthodes de modélisation des systèmes dynamiques cellulaires, le schéma conceptuel d’un tel simulateur a été développé. Le simulateur d’évacuation d’urgence a été conçu via UML en langage Java. En conclusion, les perspectives concernant la poursuite de cette étude sont présentéesThis thesis is about aircraft emergency evacuation and its principal objective is to establish a computational model able to simulate realistically it. This will contribute to the certification process of new aircraft emergency evacuation layouts and egress procedures for large capacity airliners. This thesis is composed of two main parts. In the first one, the main problem issues are identified, a state of the art in emergency evacuation from aircraft is realized and human behaviours during such an event are described. In the second part of this work, the elements of the emergency evacuation model are identified. After analysing existing models and different models of dynamic cellular systems, the conceptual model of this simulator is proposed. Its framework has been designed using UML and the routines are written in Java. Finally future research directions are given
4
Shao, Liang. "GNSS performance modelling for high interrity aircraft applications." Thesis, Cranfield University, 2012. http://dspace.lib.cranfield.ac.uk/handle/1826/7442.
Full textAbstract:
Till recently, no significant attempts have been made of developing Aircraft
Based Augmentation System (ABAS) architectures capable of generating
integrity signals suitable for safety-critical GNSS applications and no
commercial ABAS products are available at present.
The aim of this research is to support the design a system that generates
integrity signals suitable for GNSS application. The conceptual design and key
mathematical models were recently developed by the Italian Air Force
Experimental Flight Test Centre (CSV-RSV) [1, 2]. Such a system, would be
able to provide steering information to the pilot, allowing for real-time and
continuous integrity monitoring, avoidance of safety/mission-critical flight
conditions and fast recovery of the required navigation performance in case of
GNSS data losses.
The key elements addressed in this thesis are the development of a CATIA
model for military and civil aircraft, supporting antenna obscuration and
multipath analysis. This is to allow the ABAS system to generate suitable
integrity flags when satellites signals are lost. In order to analyse the GNSS
signal loss causes, the GNSS constellation models, the flight dynamics models,
fading models, multipath models, Doppler shift models, and GNSS receiver
tracking technology previously developed by CSV-RSV, are considered in this
research.
5
Wu, Tao. "Integrative system modelling of aircraft electrical power systems." Thesis, University of Nottingham, 2010. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.537690.
Full text
6
Areerak, Kongpan. "Modelling and stability analysis of aircraft power systems." Thesis, University of Nottingham, 2009. http://eprints.nottingham.ac.uk/12944/.
Full textAbstract:
The more-electric aircraft concept is a major trend in aircraft electrical power system engineering and results in an increase in electrical loads based on power electronic converters and motor drive systems. Unfortunately, power electronic driven loads often behave as constant power loads having the small-signal negative impedance that can significantly degrade the power system stability margin. Therefore, the stability issue of aircraft power systems is of great importance. The research of the thesis deals with the modelling and stability analysis of an aircraft power system. The aircraft power system architecture considered in the thesis is based on the More Open Electrical Technologies (MOET) aircraft power system with one generator as only a single generator can be connected to a system at any one time. The small-signal stability analysis is used with the system dynamic model derived from the dq modelling method under the assumption that the aircraft power system operating point does not change rapidly during normal operation mode. The linearization technique using the first order terms of a Taylor expansion is used so as to achieve a set of linear models around an equilibrium point for a small-signal stability study. The thesis presents the development of effective models capable of representing the electrical power system dynamic behaviour for stability studies. The proposed model can be used to predict the instability point for variations in operating points and/or system parameters. Agreement between the theoretical estimation, simulation, and experimental results for a simple system are achieved that ranges from acceptable to very good. Finally, the subsystem models described in the thesis can be interconnected in an algorithmic way that is representative of a more generalized aircraft power system model. The generalized model is also applied to a more complex and realistic aircraft power system with simulation validations for thorough investigations of aircraft power system stability. This model may be considered as a powerful and flexible stability analysis tool to analyse the complex multi-converter electrical power systems.
7
Coetzee, Etienne. "Modelling and nonlinear analysis of aircraft ground manoeuvres." Thesis, University of Bristol, 2011. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.541611.
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8
Hoff, J. C. "Aircraft parameter estimation by estimation - before - modelling technique." Thesis, Cranfield University, 1995. http://dspace.lib.cranfield.ac.uk/handle/1826/10748.
Full textAbstract:
The use of the
estímation-before-modellíng (EBM) two step identification
procedure for the determination of aircraft aerodynamic derivatives from flight
test data is
analysed and illustrated. In the first step of the identification
procedure the usual Extended Kalman Filter (EKF) associated with the Modified
Bryson-Frazíer (MBF) smoother is compared with a new alterative filtering and
smoothing process. The new smoother is simpler and less computationally
demanding than the MBF smoother. However, its main advantage is that it
enables simultaneous data
smoothing with state derivative estimation, thereby
avoiding the need for a separate differentiation algorithm. The new smoother differentiator
has an
important feature that is the determination of the noise
characteristics of the measurement
signal under analysis prior to the smoothing
process. This is done by variance matching between the theoretical and
measured autocorrelation of the innovation
process generated by a Kalman filter.
The new
technique is compared with the old one by determining the aerodynamic
models for a EMB-312 Tucano dutch roll manoeuvre. It is demonstrated that
the new smoother
may be used to replace the MBF. Otherwise the new
technique
is used in the
analysis of the Handley Page Jetstream-100 aircraft low speed
controls free
phugoid trying to identify the contribution of the power Variation
observed
during the phugoid to the stability of the oscillation. Finally the models
obtained from the
phugoid analysis are reprocessed using the Total Least Square
regression and the results are compared with those from the ordinary Least
Square formulation.
9
Von, Klemperer Nicholas. "Dual-axis tilting quadrotor aircraft: Dynamic modelling and control of dual-axis tilting quadrotor aircraft." Master's thesis, Faculty of Engineering and the Built Environment, 2018. http://hdl.handle.net/11427/30156.
Full textAbstract:
This dissertation aims to apply non-zero attitude and position setpoint tracking to a quadrotor aircraft, achieved by solving the problem of a quadrotor’s inherent underactuation. The introduction of extra actuation aims to mechanically accommodate for stable tracking of non-zero state trajectories. The requirement of the project is to design, model, simulate and control a novel quadrotor platform which can articulate all six degrees of rotational and translational freedom (6-DOF) by redirecting and vectoring each propeller’s individually produced thrust. Considering the extended articulation, the proposal is to add an additional two axes (degrees) of actuation to each propeller on a traditional quadrotor frame. Each lift propeller can be independently pitched or rolled relative to the body frame. Such an adaptation, to what is an otherwise well understood aircraft, produces an over-actuated control problem. Being first and foremost a control engineering project, the focus of this work is plant model identification and control solution of the proposed aircraft design. A higher-level setpoint tracking control loop designs a generalized plant input (net forces and torques) to act on the vehicle. An allocation rule then distributes that virtual input in solving for explicit actuator servo positions and rotational propeller speeds. The dissertation is structured as follows: First a schedule of relevant existing works is reviewed in Ch:1 following an introduction to the project. Thereafter the prototype’s design is detailed in Ch:2, however only the final outcome of the design stage is presented. Following that, kinematics associated with generalized rigid body motion are derived in Ch:3 and subsequently expanded to incorporate any aerodynamic and multibody nonlinearities which may arise as a result of the aircraft’s configuration (changes). Higher-level state tracking control design is applied in Ch:4 whilst lower-level control allocation rules are then proposed in Ch:5. Next, a comprehensive simulation is constructed in Ch:6, based on the plant dynamics derived in order to test and compare the proposed controller techniques. Finally a conclusion on the design(s) proposed and results achieved is presented in Ch:7. Throughout the research, physical tests and simulations are used to corroborate proposed models or theorems. It was decided to omit flight tests of the platform due to time constraints, those aspects of the project remain open to further investigation. The subsequent embedded systems design stemming from the proposed control plant is outlined in the latter of Ch:2, Sec:2.4. Such implementations are not investigated here but design proposals are suggested. The primary outcome of the investigation is ascertaining the practicality and feasibility of such a design, most importantly whether or not the complexity of the mechanical design is an acceptable compromise for the additional degrees of control actuation introduced. Control derivations and the prototype design presented here are by no means optimal nor the most exhaustive solutions, focus is placed on the whole system and not just a single aspect of it.
10
Linehan, Rory Daniel. "Modelling simulation and control of a remotely piloted vehicle." Thesis, Coventry University, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.363857.
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11
Vaziry-Zanjany, Mohammad Ali. "Aircraft conceptual design modelling incorporating reliability and maintainability predictions." Thesis, Cranfield University, 1996. http://dspace.lib.cranfield.ac.uk/handle/1826/3437.
Full textAbstract:
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.
12
Macey, P. "Probabilistic risk assessment modelling for passenger aircraft fire safety." Thesis, Cranfield University, 1997. http://hdl.handle.net/1826/4260.
Full textAbstract:
This thesis describes the development
of a computer simulation model
for the
investigation
of airliner
fire
accident safety.
The
aim of the work
has been to create a computer-based analysis tool that generates
representative aircraft accident scenarios and then simulates their outcome
in terms of
passenger injuries
and
fatalities. The details
of the accident scenarios are
formulated
to closely match the type of events that are
known to have
occurred
in
aircraft
accidents over the last 40
years.
This information has been obtained
by
compiling a
database
and undertaking
detailed
analysis of approximately
200
airliner
fire
accidents. In
addition to utilising
historical data, the modelling work
has incorporated
many of the key findings
obtained
from
experimental research undertaken
by the
world's air safety community.
An
unusual
feature of the simulation process is that all critical aspects of the accident
scenario have been analysed and catered for in the formative
stages of the programme
development. This has
enabled complex effects, such as cabin crash
disruption,
impact trauma injuries, fire
spread, smoke
incapacitation
and passenger evacuation to
be
simulated
in
a
balanced and
integrated manner.
The
study
is intended to further the general appreciation and understanding of the
complex events that lead to fatalities in
aircraft
fire
accidents.
This is
achieved
by
analysing all contributory
factors that are
likely to arise
in
real
fire
accident scenarios
and undertaking quantitative risk assessment through the use of novel simulation
methods. Future development
of the research could potentially enable the undertaking
of a systematic exploration and appraisal of the effectiveness of
both
current and
future
aircraft
fire
safety policies.
13
Vaziry-Zanjany, Mohammad Ali (F). "Aircraft conceptual design modelling incorporating reliability and maintainability predictions." Thesis, Cranfield University, 1996. http://hdl.handle.net/1826/3437.
Full textAbstract:
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.
14
Prescott, Darren Richard. "Safety modelling for the time limited dispatch of aircraft." Thesis, Loughborough University, 2007. https://dspace.lboro.ac.uk/2134/12235.
Full textAbstract:
Time-limited dispatch (TLO) allows aircraft to dispatch with known faults present in the engine control systems. These systems govern the thrust control of engines and, in order for a TLO scheme to be certified, the failure rates to loss of thrust control (LOTC) must lie within or below prescribed bounds. The aim of the work presented in this thesis was to develop a tool that could be used to model the time-limited dispatch (TLO) of aircraft and compare this with currently recommended techniques for modelling TLO. Currently techniques for modelling TLO require the failure rates to LOTC from various dispatchable system configurations, i.e. system configurations where a number of faults are present. These rates determine how long the system may be dispatched with certain faults present and also a failure rate to LOTC can be computed for the whole system. A number of approximations are used within the models, intended to make them simple to use. The concern is that these approximations might not accurately model the system behaviour and that the results obtained might as a consequence be unreliable. Monte Carlo simulation (MCS) was identified as an analysis method that could deal with the intricacies and complexities involved in the application of TLD. Software, written in C++, allowed TLO to be modelled using MCS. Full use was made of the flexibility of MCS and many TLO maintenance scenarios were considered as the code was developed. The MCS code was written in such a way that all failure rates to LOTC, i.e. those representing the system LOTC and the dispatchable fault LOTC rates, would be produced as outputs. Results obtained using the developed software and the currently recommended techniques were compared. Finally, the MCS code was embedded within an optimisation procedure in order to demonstrate how such a tool could be used in the design process for a system. A simple genetic algorithm procedure was employed to carry out this optimisation process.
15
Jordan, Philip [Verfasser]. "Scalable Modelling of Aircraft Environmental Control Systems / Philip Jordan." München : Verlag Dr. Hut, 2019. http://d-nb.info/118151441X/34.
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16
Kiébré, Rimyalegdo. "Contribution to the modelling of aircraft tyre-road interaction." Phd thesis, Université de Haute Alsace - Mulhouse, 2010. http://tel.archives-ouvertes.fr/tel-00601774.
Full textAbstract:
This thesis is a part of the French national project called MACAO (Modélisation Avancée de Composants Aéronautiques et Outils associés). In collaboration with Messier-Dowty company (a landing gears manufacturer), the thesis has contributed to better understand the actual literature studies in the field of aircraft tyre-road interaction modelling and therefore, to help making an optimal choice of model for a specifie application. The objectives have been to propose models for representing the tyre behaviour on the ground with respect to the aircraft run types. Physical oriented models are preferred. To complete this study, a literature survey of the previous researches in tyre modelling for steadystate responses is first carried out. Then, based on the main factors playing an important role in tyre modelling, it is proposed a classification for the physical and the semi-empirical models, which are also investigated. Based on this classification, the study requirements and the measurement data constraints, an a priori choice of suitable models are studied. A further investigation of the tyre deformation at pure lateral slip is carried out. It has allowed to physically describe the mechanism of generation of the longitudinal component of the tyre force at pure lateral slip. This force is refened as induced longitudinal force. By taking this force into consideration, it has been possible to explain why the self-aligning moment can drop to zero before the tyre gets to full sliding at pure lateral slip. Besides, the sensitivity analysis is proposed as a means for determining the parameters that have most influence on the model output and thus, are responsible for the output uncertainty.
17
Pervier, Hugo. "Emissions modelling for engine cycle and aircraft trajectory optimisation." Thesis, Cranfield University, 2013. http://dspace.lib.cranfield.ac.uk/handle/1826/10396.
Full textAbstract:
The aviation industry is currently experiencing a growth rate of about 4% per annum and this trend
is expected to continue into the future. One concern about this growth rate is the impact it will have
on the environment particularly in terms of emissions of CO2, NOx and relatively recently also cirrus
clouds induced by contrails.
The ACARE has set emissions reduction targets of 50% reduction of CO2 and noise and 80% reduction
of NOx by 2020 relative to Y2000 technology. Clean Sky and other large EU collaborative projects
have been launched in an effort to identify new, more efficient, aircraft and engine technologies,
greener operational and asset management practices and lower life cycle emissions. This PhD
research was funded by and contributed to the Systems for Green Operations Integrated Technology
Demonstrator (SGO-ITD) of the Clean Sky project.
The key contribution to knowledge of this research is the development and application of a
methodology for simultaneous optimisation of aircraft trajectories and engine cycles. Previous
studies on aircraft trajectory optimisation studies, published in the public domain, are based on
relatively low fidelity models. The case studies presented in this thesis are multi-objective and based
on higher fidelity, verified aircraft, engine and emissions models and also include assessments of
conceptual engines with conceptual LPP combustors.
The first task involved the development of reactor based NOx emission prediction models for a
conventional aero gas turbine combustor and a novel conceptual lean pre-mixed pre-vaporised
combustor. A persistent contrails prediction model was also developed.
A multi-disciplinary framework comprising a genetic algorithm based optimiser integrated with an
engine performance, an aircraft performance and an emission prediction model was then
developed. The framework was initially used to perform multi-disciplinary aircraft trajectory
optimisation studies and subsequently both aircraft trajectory and engine cycle optimisation studies
simultaneously to assess trade-offs between mission fuel burn, flight time, NOx production and
persistent contrails formation ... [cont.].
18
Premachandran, Sarah. "Advanced computational modelling for aircraft landing gear unsteady aerodynamics." Thesis, University of Southampton, 2017. https://eprints.soton.ac.uk/418073/.
Full textAbstract:
High-fidelity turbulence modelling techniques have been applied to simulate the flow field around a simplified landing gear bay geometry. Three-dimensional Detached Eddy Simulation (DES) simulations have been performed for a cavity with the front 2/3 covered, as is representative of a nose landing gear bay. Resonant modes were observed in the shear layer, with frequencies in good agreement with the Rossiter cavity modes. The side-walls of the cavity, when compared to quasi-two-dimensional simulations with infinite span, were found to suppress the presence of acoustic modes inside the cavity, as well as causing a greater degree of breakdown in the shear layer, and changing the dominant resonant modes. The geometry was varied to incorporate a single strut, and (separately) open rear doors, to test their separate contributions to the flow field in the landing gear bay. Both were found to produce small, high-frequency vortex structures, which interacted with the cavity shear layer and caused higher resonant modes to be present than with the clean cavity. A Large Eddy Simulation (LES) methodology has been developed and improved using the in-house solver software. An improved subgrid-scale model has been implemented, and the sensitivity of the solution to a variety of settings has been tested. Using a method for efficiently simulating flat-plate turbulence by tripping the flow using a small step, realistic wall-bounded turbulence has been modelled, with mean and turbulent quantities in good agreement with the literature for flat plate boundary layer flows. The best-practice guidelines from this study were then applied to a turbulent flat plate upstream of the cavity with LES. The boundary layer turbulence structures were found to disrupt the coherence of the shear layer vortices, and lengthwise acoustic modes dominated inside the cavity in most cases. The sensitivity of this baseline simulation to several different parameters was investigated. These included the condition and thickness of the upstream boundary layer, the geometry around the lip of the cover, the turbulence modelling technique, and the spanwise length of the domain. The most significant difference was obtained by adding side walls, which was found to promote the development of shear layer resonance. Lower-mode tones were observed, with the associated pressure fluctuations being imposed and amplified inside the cavity.
19
Reytier, Thomas. "Modelling fatigue spectra of aircraft structure under gust loads." Toulouse 3, 2012. http://thesesups.ups-tlse.fr/1614/.
Full textAbstract:
Cette thèse est consacrée à l'analyse de fatigue et de tolérance aux dommages des structures d'avions soumis aux rafales de vent. L'analyse de fatigue et de tolérance aux dommages est un enjeu essentiel dans la conception des structures d'avions. Elle permet de définir un programme d'inspection de la structure afin d'assurer sa sécurité tout au long de la vie de l'avion. La première partie passe en revue l'état de l'art dans les différents domaines impliqués dans le processus global d'analyse de fatigue des structures d'avions soumis aux rafales de vent: la modélisation de la turbulence atmosphérique, le calcul des charges et des contraintes à l'aide d'analyses par éléments finis, la construction du spectre de fatigue et enfin, l'analyse de fatigue et de tolérance aux dommages. La deuxième partie présente le processus complet actuellement implémenté au sein d'Airbus. Les points forts et les points faibles de ce processus sont d'identifiés et permettent de dégager des axes d'amélioration. A partir du modèle de turbulence continue basé sur la densité spectrale de puissance (DSP) de Von Karman, les contraintes calculées sont insérées selon des statistiques établies par des mesures envol dans le spectre de fatigue pour former une séquence de cycles de contraintes. Les données d'entrée pour l'analyse de fatigue et tolérance aux dommages sont obtenues à partir de la définition des différents profils de mission, des valeurs de contraintes unitaires, de la réponse dynamique de la structure et des statistiques de turbulence. Dans la troisième partie, une nouvelle méthodologie est présentée afin d'obtenir des séquences temporelles des contraintes dues à la turbulence de manière précise et efficace. Cette méthode s'appuie sur de nouveaux résultats permettant de générer des signaux temporels corrélés à partir des DSP. Tout d'abord, les DSP des différentes composantes des contraintes sont directement obtenues à l'aide d'une analyse par éléments finis à partir de la DSP de Von Karman. Puis, les séquences temporelles corrélées de ces contraintes sont générées et sont ensuite distribuées dans le spectre de fatigue selon la loi statistique de l'intensité de la turbulence atmosphérique. Ce nouveau processus permet d'améliorer le calcul des contraintes et la génération du spectre de fatigue. Il remplace les statistiques de turbulence par des statistiques de franchissement de niveaux de contraintes raisonnablement conservatives définies par une formule analytique. De plus, le temps de livraison des données d'entrée pour l'analyse de fatigue et tolérance aux dommages est significativement réduit. Les résultats présentés, issus de l'analyse de fatigue et de tolérance aux dommages, permettent de souligner la qualité des améliorations apportées à la fois en termes de précision et de durée du processusThis thesis is dedicated to the fatigue and damage tolerance analysis of the aircraft structures under gust loads. The fatigue and damage tolerance analysis is a significant issue in the aircraft structure design. It aims at defining the inspection program of the aircraft structure in order to ensure its safety through its entire life. The first part reviews the state-of-the-art in the various involved topics for the global process for fatigue analysis of aircraft structure under gust loads: the atmospheric turbulence modelling, the load and stress computation by a finite element analysis, the generation of the fatigue spectrum and at the end, the fatigue and damage tolerance analysis. The second part presents the whole process currently implemented at Airbus. The main strengths and weaknesses are pointed out and this en-ables the identification of several improvement axes. From the continuous turbulence model based on the Von Karman Power Spectral Density(PSD), the computed stresses are included according to statistics established from in-flight measurements in the fatigue spectrum in order to build a stress cycle sequence. The input data for the fatigue and damage tolerance analysis are obtained from the definition of the various fatigue mission profiles, the unitary stress values, the dynamic response of the structure and the turbulence statistics. In the third part,a new methodology is presented in order to obtaine efficiently and accurately the temporal stress sequences due to the atmospheric turbulence. This method relies on new results enabling the generation of correlated time signals from the PSD functions. First, the PSD of the various stress components are directly obtained from the Von Karman PSD via a finite element analysis. Then, the correlated temporal stress sequences are generated and distributed in the fatigue spectrum according to the turbulence intensity statistical law. This new process enables the improvement of the stress computation and the fatigue spectrum generation. It replaces the turbulence statistics by stress exceedance statistics which are defined by an analytical formula in a reasonably conservative way. In addition, the lead time to build the input data for the fatigue and damage tolerance analysis is significantly reduced. Results from the fatigue and damage tolerance analysis are presented in order to highlight the quality of the improved processes both in terms of accuracy and lead time
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Manimala, Binoy James. "Mathematical modelling for the evaluation of a tiltwing aircraft." Thesis, Glasgow Caledonian University, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.287856.
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Amadori, Kristian. "Geometry Based Design Automation : Applied to Aircraft Modelling and Optimization." Doctoral thesis, Linköpings universitet, Maskinkonstruktion, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-73109.
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Product development processes are continuously challenged by demands for increased efficiency. As engineering products become more and more complex, efficient tools and methods for integrated and automated design are needed throughout the development process. Multidisciplinary Design Optimization (MDO) is one promising technique that has the potential to drastically improve concurrent design. MDO frameworks combine several disciplinary models with the aim of gaining a holistic perspective of a system, while capturing the synergies between different subsystems. Among all disciplines, the geometric model is recognized as playing a key role, because it collects most of the data required to any other disciplinary analysis. In the present thesis, methodologies to enable multidisciplinary optimization in early aircraft design phases are studied. In particular, the research aims at putting the CAD geometric model in the loop. This requires the ability to automatically generate or update the geometric model, here referred to as geometry-based design automation. The thesis proposes the use of Knowledge Based Engineering (KBE) techniques to achieve design reuse and automation. In particular, so called High Level CAD templates (HLCts) are suggested to automate geometry generation and updates. HLCts can be compared to parametric LEGO® blocks containing a set of design and analysis parameters. These are produced and stored in libraries, giving engineers or a computer agent the possibility to first topologically select the templates and then modify the shape of each template parametrically. Since parameterization is central to modelling by means of HLCts, a thorough analysis of the subject is also performed. In most of the literature on MDO and KBE two recurring requirements concerning the geometrical model are expressed: the model should be flexible and robust. However, these requirements have never been properly formulated or defined. Hence, in the thesis a mathematical formulation for geometry model robustness and flexibility are proposed. These formulations ultimately allow the performance of geometric models to be precisely measured and compared. Finally, a prototyping and validation process is presented. The aim is to quickly and cost-effectively validate analytical results from an MDO process. The proposed process adopts different manufacturing techniques depending on the size and purpose of the intended prototype. In the last part of the thesis, three application examples are presented. The examples are chosen from research projects that have been carried out at Linköping University and show how the proposed theoretical results have been successfully employed in practice.Kraven på ökad effektivitet utmanar ständigt produktutvecklingsprocessen. I och med att ingenjörsprodukter blir allt mer komplexa, växer genom hela utvecklingsprocessen behovet av verktyg och metoder för integrerad och automatiserad design. Multidisciplinär Design Optimering (MDO) är en lovande teknik som kan drastiskt förbättra parallell design. I ett MDO ramverk är flera disciplinära modeller sammankopplade för att uppnå ett holistiskt systemperspektiv, men där synergierna mellan olika delsystem också kan fångas upp. Bland alla möjliga discipliner spelar geometrimodellen en central roll, eftersom den innefattar en stor del av all information som är nödvändig för andra disciplinära analyser. I avhandlingen studeras ett flertal metoder för att möjliggöra multidisciplinär optimering i de tidigaste faserna av flygplansdesign. I synnerlighet är forskningen riktad mot att införa geometriska CAD modeller i designloopen. Det blir därmed nödvändigt att kunna automatiskt generera eller uppdatera geometriska modeller, vilket i avhandlingen kallas för ”geometribaserad design automation”. Avhandlingen förordar att Knowledge Based Engineering (KBE) tekniker används för att konstruktioner skall kunna automatiseras och återanvändas. Så kallade Hög Nivå CAD mallar (på engelska High Level CAD templates – HLCts) föreslås för att automatiskt generera och uppdatera geometrimodeller. HLCts kan jämföras med parametriska LEGO® klossar som innehåller variabler för design och analys. Mallarna kan samlas i bibliotek; därefter har konstruktörer eller dator agenter möjligheten att först topologiskt välja en mall och sedan ändra på dess utförande genom utvalda parametrar. Eftersom parameterisering är ett centralt begrepp för HLCt principen, föreslås även en fördjupad analys av ämnet. I stor del av MDO och KBE litteraturen ställs det två återkommande krav på geometrimodellen: modellen bör vara flexibel och robust. Eftersom dessa krav aldrig har getts en formell formulering, förordas i avhandlingen en matematisk beskrivning av modellrobusthet och - flexibilitet. Tack vore formuleringen är det möjligt att noggrant mäta och jämföra till vilken grad geometriska modeller fungerar. Slutligen presenteras en valideringsprocess baserad på kostnadseffektiva prototyper som används för att snabbt bekräfta analytiska resultat från MDO ramverket. Den föreslagna processen nyttjar olika tillverkningsmetoder, beroende på prototypens tänkta storlek och användning. I sista delen av avhandlingen presenteras även tre applikationsexempel, valda från forskningsprojekt som har bedrivits på Linköpings universitet och som visar hur de teoretiska resultaten har kommit till användning i praktiken.
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Poudel, Sabin. "Modelling of a Generic Aircraft Environmental Control System in Modelica." Thesis, Linköpings universitet, Fluida och mekatroniska system, 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-156675.
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This thesis documents the modelling of generic Environmental Control System(ECS) of an aircraft in Modelica by utilizing components from free version of theTTECCS (Technical Thermodynamic Environmental Control and Cooling Systems) library. In doing so, components used for developing ECS from the TTECCS library are mathematically verified with theoretical formula in MATLAB. Selected components are investigated with valid input data to initialize the simulation and verify its behaviors with corresponding available data. Hereinafter, the object-oriented modelling method is used to integrate ECS components to develop a functional system. The main function of ECS is to regulate the pressure and temperature inside the cabin to accepted physiology flight safetylevels. Different types of ECS architecture are presented in this document. An ECS developed here is based on the bootstrap system and consists only one cooling unit comprised with the source, pipes, two heat exchanger, compressor, turbine, temper-ature control valve, pressure control valve, and sinks. Dry air(Ideal gas) is used as a medium in the system. Temperature drop along each component corresponds to available A320 cruise flight data in order to calculate the top level parameter and to initialize the components, subsequently an ECS system. Several systematized methods for Object-oriented modelling and system design were studied and steps are extracted accordingly that suits to initiate the procedurefor this project, which is also presented. Time domain simulation is performed inModelica and Dymola. A simplified control system is built to regulate the system, therefore restrained it as a future work to develop real in-flight condition control system of an ECS.Top level parameters were selected within valid customized ranges for developing a performance map of the components. After generating the map, optimal data from the map were taken to initialize final ECS. The simulation results of the final model is then compared to A320 flight data which is comparable in behavior; this was expected. Above all, simulation environment Modelica and free version of TTECCS library components are reliable to develop ECS in order to investigate ECS components behavior and predict cabin conditions before developing a prototype.
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Reschke, Christian. "Integrated flight loads modelling and analysis for flexible transport aircraft." [S.l. : s.n.], 2006. http://nbn-resolving.de/urn:nbn:de:bsz:93-opus-27974.
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Kallinen, Valtteri A. "Collision risk modelling for unmanned aircraft separation and traffic management." Thesis, Queensland University of Technology, 2022. https://eprints.qut.edu.au/232516/1/Valtteri_Kallinen_Thesis.pdf.
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This thesis develops models and procedures for designing safe airspace for Unmanned Aerial Vehicles (UAVs). Mid-air collision risk models with foundations in manned aviation are extended and adapted to develop separation standards for UAVs whilst addressing the unique differences from traditional manned aviation. Airspace design is also investigated using mathematical optimisation which maximises traffic throughput to make high-density operations viable, whilst still maintaining a given target level of safety.
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Guo, H. "An investigation into the finite element modelling of an aircraft tyre and wheel assembly." Thesis, Coventry University, 2014. http://curve.coventry.ac.uk/open/items/94ff9a61-2e93-49e0-880f-0586b0244dfe/1.
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This thesis reports the investigation into the modelling and simulation of an aircraft tyre and wheel assembly in finite element environment. The finite element simulations basing on aircraft tyre test and operational scenarios could predict the loads transferred from tyre and the stresses distributed to the wheel rim. The virtual analysis could assess the safety criteria of different tyre structures, which would lead to the cost and time circle reduction in tyre R&D process. An H41x16.0R20 radial ply aircraft test tyre and its corresponding test wheel, provided by Dunlop Aircraft Tyres Limited, are adopted as the subject of this research. The material properties, especially the rubber and fabric materials, have been investigated. The finite element hyperelastic models have been utilized to represent rubbers and been correlated to experimental data. The 2D and 3D finite element tyre models, along with the finite element wheel models are created in the commercial finite element code, LS-Dyna. The finite element models have been validated with either industrial standardised simulation results or experimental data. Basing on the validated models, simulations that duplicating static test and dynamic operational scenarios have been developed. The researches have provided knowledge in comparing single and double bead tyre designs with respect to wheel loading mechanisms. The computational model also allowed manufacturers to assess the performance and safety criteria of a particular tyre at its design stage. The development of such models would add to the general drive towards the use of more virtual prototypes in an area traditionally reliant on experimental testing.
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Wasiuk, Donata Katarzyna. "Modelling aircraft emissions and their impact on atmospheric composition and ozone." Thesis, University of Bristol, 2014. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.654469.
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Emissions of NOx ' from aircraft influence global atnl0spheric composition, chemistry and ultimately our climate via tropospheric 0 3 production. They are increasing the global tropospheric concentration of NOx with continuing intensity as we fly more and more of us fly. Here, the 3-D Lagrangian CTM STOCHEM-CRI with the novel CRIv2- R5 chemistry scheme was used to evaluate the impact of current global , aircraft NOx emissions on atmospheric composition as well as the concentration and global spatial distribution of tropospheric NOx and 0 3 , Further, an operational mitigation strategy for commercial aircraft impact on air quality and climate referred to as the turBoprop replacement strategy (TRS) in which jets on short-haul missions were replaced with turboprops was investigated. These assessments were based on the 4-D Aircraft Fuel Burn and Emissions Inventory spanning the time period 2005-2011 created with the Aircraft Performance Model Implementation (APMI) software which was developed in support of this project.
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Noor, Mohamed Sulfickerali. "Efficient CFD based aero-thermo-mechanical modelling for aircraft engine design." Thesis, University of Surrey, 2017. http://epubs.surrey.ac.uk/813497/.
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In this thesis, improved and faster CFD based aero-thermo-mechanical methods that can be used to optimize engine configurations early in the design process are described. Axisymmetric models of 3D non-axisymmetric features such as protrusions, holes and honeycomb liners are developed for use in this context, and 3D unsteady CFD is used to investigate the flow physics. Initially, the research focussed on modelling of a rotor-stator disc cavity. Steady CFD validations for a plane disc and for a disc with protrusion were carried out and a simplified body force model was developed for including the 3D effects of rotating and stationary bolts into the axisymmetric CFD models. The simplified rotor bolt model was verified and validated by comparing the results with Sussex Windage rig test data and 3D CFD data. The simplified stator bolt model was verified using 3D CFD results. The simplified rotor bolt model was found to predict the drag and windage heat transfer with reasonable accuracy compared to 3D sector CFD results. However, 3D sector CFD under-predicts the high core flow swirl and the adiabatic disc surface temperature inboard of the bolt, compared to experimental data. In the second part of the study, unsteady Reynolds averaged Navier-Stokes (URANS) calculations of the rotating bolts cases were performed in order to better understand the flow physics. Although the rotor-stator cavity with bolts is geometrically steady in the rotating frame of reference, it was found that the rotor bolts generate unsteadiness which creates time-dependent rotating flow features within the cavity. A systematic parametric study is presented giving insight into the influence of the bolt number and the cavity geometric parameters on the time dependent flow within the cavity. The URANS calculations were extended to a high pressure turbine (HPT) rear cavity to show possible unsteady effects due to rotating bolts in an engine case. Following this, the body force model was adapted to model the rotating hole velocity changes and flow through honeycomb liners. The honeycomb and hole models were verified by comparing the results with available experimental data and 3D CFD calculations. In the final part of the study, coupled FE-CFD calculations for a preliminary design whole engine thermo-mechanical (WETM) model for a transient square cycle was performed including the effects of non-axisymmetric features. Six cavities around the HPT disc were modelled using CFD. The coupled approach provides more realistic physical convective heat transfer boundary conditions than the traditional approach. The unvalidated baseline thermo-mechanical model results were verified using the high fidelity coupled FE-CFD solution. It was demonstrated that the FE-CFD coupled calculations with axisymmetric modelling of 3D features can be achieved in a few days time scale suitable for preliminary engine design. The simplified CFD based methods described in this thesis could reduce the computational time of transient coupled FE-CFD calculations several orders of magnitude and may provide results as accurate as 2DFE-3DCFD coupled calculations.
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Thokala, Praveen. "Life cycle cost modelling as an aircraft design decision support tool." Thesis, University of Southampton, 2009. https://eprints.soton.ac.uk/72021/.
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This report summarizes the work that has been carried out as part of the FLAVIIR project, a 5 year research program looking at technologies for future unmanned air vehicles. A novel classication of aircraft product defnition is utilised and a framework to estimate the life cycle cost of aircraft using the product definition is presented. The architecture to estimate the life cycle cost and the associated models are described. The acquisition costs are estimated using a hierarchical structure and a discrete simulation model is used to estimate the maintenance and operation costs. The acquisition cost model uses an object oriented approach with libraries of materials and processes integrated into the cost model. Risk analysis is performed to identify the important design parameters and uncertainty in the model. The acquisition cost model developed has the capability to estimate the costs of aircraft structures manufactured using metal-based materials as well as non-metal-based materials. The discrete event simulation model estimates the operation and maintenance costs of a fleet of aircraft using the mission characteristics, aircraftperformance and the logistics data as input. The aircraft performance parameters are calculated by using aerodynamic analysis along with performance analysis models and the simulation model utilises a novel methodology to link aircraft performance with survivability analysis for estimating the maintenance costs. A framework is presented in which the cost models developed can be integrated into the conceptual design process to facilitate the comparison between different configurations. The usage of the life cycle cost framework as a decision support tool is outlined and three case studies are presented which include composites vs metals trade-off analysis, optimisation studies and web deployment for real time cost estimation. The novel contributions of this research are outlined and interesting avenues for future research that can be pursued are identified.
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Dharmasaroja, Atipong. "Efficient modelling of failure envelopes and load patterns in aircraft structures." Thesis, Queen's University Belfast, 2015. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.695327.
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Due to the dynamically-varying nature of aircraft loading scenarios, a large number of global load cases are generated which must be analysed in a Global Finite Element Model (GFEM) to obtain the internal load paths going into each substructure. Analysing all load cases is often not possible due to computational constraints, so that substantial engineering judgement in load case down-selection is required. One innovation developed by QUB to reduce the number of load cases is to use Singular Value Decomposition (SVD) to derive a smaller set of characteristic loads which represent all the global load distributions. This research focuses on developing the SVD based load development process by studying factors that could affect the accuracy and proposes some robust error quantification methods suitable for different scenarios. The major downstream benefit of the process is that the analysis results for this set of characteristic loads can be superimposed to create the internal load distributions resulting from all the original load cases. The method is also used in sensitivity analysis for gradient based optimisation and shows a very large reduction in computational effort. When the SVD is performed at the local structure level, a few internal load characteristic patterns, which represent all internal loads, can also be identified. Another major development in this work is that the failure envelope can be constructed in this reduced dimensional load space. The resulting surface defines critical failure constraints under any loading. The novel parameterisatlon and adaptive mesh refinement techniques have been employed to efficiently construct the failure surface of the industry standard structural assessment tools, which are treated as a black box. The failure envelope therefore provides valuable insights into the structures, failures and loads. Moreover, the down-selection process or constraint filtering can be performed very quickly using the information from this envelope.
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Carmai, Julaluk. "The modelling of matrix-coated fibre composite consolidation." Thesis, University of Oxford, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.365724.
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Liu, Chengyuan. "Turboelectric Distributed Propulsion System Modelling." Thesis, Cranfield University, 2013. http://dspace.lib.cranfield.ac.uk/handle/1826/8408.
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The Blended-Wing-Body is a conceptual aircraft design with rear-mounted, over wing engines. Turboelectric distributed propulsion system with boundary layer ingestion has been considered for this aircraft. It uses electricity to transmit power from the core turbine to the fans, therefore dramatically increases bypass ratio to reduce fuel consumption and noise. This dissertation presents methods on designing the TeDP system, evaluating effects of boundary layer ingestion, modelling engine performances, and estimating weights of the electric components. The method is first applied to model a turboshaft-driven TeDP system, which produces thrust only by the propulsors array. Results show that by distributing an array of propulsors that ingest a relatively large mass flow directly produces an 8% fuel burn saving relative to the commercial N+2 aircraft (such as the SAX-40 airplane). Ingesting boundary layer achieves a 7-8% fuel saving with a well-designed intake duct and the improved inlet flow control technologies. However, the value is sensitive to the duct losses and fan inlet distortion. Poor inlet performance can offset or even overwhelm this potential advantage. The total weight of the electric system would be around 5,000-7,000 kg. The large mass penalties further diminish benefits of the superconducting distributed propulsion system. The method is then applied to model a turbofan-driven TeDP system, which produces thrust by both the propulsors array and the core-engines. Results show that splitting the thrust between propulsors and core-engines could have a beneficial effect in fuel savings, when installation effects are neglected. The optimised thrust splitting ratio is between 60-90%, the final value depends on the propulsor intake pressure losses and the TeDP system bypass ratio. Moreover, splitting the thrust can reduce the weight of the electric system with the penalty of the increased core-engine weight. In short, if the power density of the superconducting system were high enough, turboshaft-driven TeDP would be preferable to power the N3-X aircraft
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Anastasiadis, P. T. "The influences on optimal structural designs of the modelling processes and design concepts." Thesis, Cranfield University, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.267196.
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Tarkian, Mehdi, and Zaldivar Tessier Francisco Javier. "Aircraft Parametric 3D Modelling and Panel Code of Analysis for Conceptual Design." Thesis, Linköping University, Department of Management and Engineering, 2007. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-10607.
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Throughout the development of this report there will be a brief explanation of what the actual Aircraft Design Process is and in which stages the methodology that the authors are proposing will be implemented as well as the tools that will interact to produce this methodology.
The proposed tool will be the first part of a methodology that, according to the authors, by integrating separate tools that are currently used in different stages of the aeronautical design, will promote a decrease in the time frame for the initial stages of the design process.
The first part of the methodology above, that is proposed in this project, starts by creating a computer generated aircraft model and analyzing its basic aerodynamic characteristics “Lift Coefficient” and “Induced Drag Coefficient”, this step will be an alternative to statistical and empirical methods used in the industry, which require vast amount of data.
This task will be done in several steps, which will transfer the parametric aircraft model to an input file for the aerodynamic analysis program. To transfer the data a “translation” program has been developed that arranges the geometry and prepares the input file for analysis.
During the course of this report the reader will find references to existing aircrafts, such as the MD-11 or Airbus 310. However, these references are not intended to be an exact computer model of the mentioned airplanes. The authors are using this as reference so the reader can relate what he/she is seeing in this paper to existing aircrafts. By doing such comparison, the author intends to demonstrate that the Parametric Model that has been created possesses the capability to simulate to some extend the shape of existing aircrafts.
Finally from the results of this project it is concluded that the methodology in question is promising. Linking the two programs is possible and the aerodynamic characteristics of the models tested fall in the appropriate range. None the less the research must continue following the line that has been discussed in this report.
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Jansson, Ahmed Sara. "Modelling the dynamics of an unmanned aircraft using a graphical simulation tool." Thesis, KTH, Flygdynamik, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-100820.
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Complex systems can be modelled using graphical tools such as Simulink. Here, the equations of motion in combination with the necessary data were modelled using Simulink to describe and analyze the unmanned Predator C Avenger. The aerodynamic data was obtained from the potential ow solver dwfs (dry water ow solver). The Simulink model is initially in steady state, disturbances are then added to investigate the ying qualities of the aircraft both in the longitudinal and lateral direction. The modes calculated from the model are compared to the modes produced from the linearized matrices containing the aerodynamic derivatives. The other task for the Simulink model is for some of its subsystems to be integrated with the simulation program ARES, which is used at Saab. The Simulink subsystems are converted into C code and are built into ARES. The rst expected result is that the modes from the linearized model should indicate the values of the modes from the Simulink model. The largest dierence - which regards the spiral mode - was about 24% and assumed acceptable as the approximative solution for this mode is considered poor [4]. The other dierences were at most about 15%. The second expected result is that the outputs from simulating the complete model using Simulink should match the outputs obtained from simulating through ARES connected to the Simulink subsystems. It was the discovered that the obtained results - which are the values of the longitudinal trim parameters and the modes - from Simulink match almost exactly the results from ARES with some few deviations. The trim results had a maximum difference of about 6% and the values of the modes had a maximum dierence of about 10% and also assumed acceptable.
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Lippert, Stephan [Verfasser]. "Efficient vibro-acoustic modelling of aircraft components with parameter uncertainties / Stephan Lippert." Aachen : Shaker, 2010. http://d-nb.info/1081884940/34.
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Andrews, Stuart P. "Modelling and simulation of flexible aircraft : handling qualities with active load control." Thesis, Cranfield University, 2011. http://dspace.lib.cranfield.ac.uk/handle/1826/7705.
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The study of the motion of manoeuvring aircraft has traditionally considered the aircraft
to be rigid. This simplifying assumption has been shown to give quite accurate results for
the flight dynamics of many aircraft types. As modern transport aircraft have developed
however, there has been a marked increase in the size and weight of these aircraft. This
trend is likely to continue with the development of future blended-wing-body and supersonic
transport aircraft. This increase in size and weight has brought about a unique set
of aeroelastic and handling quality issues.
The aerodynamic forces and moments acting on an aeroplane have traditionally been
represented using the aerodynamic derivative approach. It has been shown that this quasisteady
aerodynamic model inadequately predicts the aircraft’s stability characteristics,
and that the inclusion of unsteady aerodynamics “greatly improves the fidelity” of aircraft
models.
This thesis thus presents a novel numerical simulation of an aeroelastic aeroplane for
real-time analysis. The model is built around the standard six degree-of-freedom equations
of motion for a rigid aeroplane using the mean-axes system, and includes unsteady
aerodynamics and structural dynamics. This is suitable for pilot-in-the-loop simulation,
handling qualities and flight loads analysis, and control law development. The dynamics
of the structure are modelled as a set of normal modes, and the equations of motion are
realised in state-space form. The unsteady aerodynamic forces acting on the aeroplane
are described by an indicial state-space model, including unsteady tailplane downwash
and compressibility effects. An implementation of the model is presented in the MATLAB/
Simulink environment.
The interaction between the flight control system, the aeroelastic system and the rigidbody
motion of the aeroplane can result in degraded handling qualities, excessive actuator
control, and fatigue problems. The introduction of load alleviation systems for the management
of loads due to manoeuvres and gusts is also likely to result in the handling
qualities of the aeroplane being degraded.
This thesis presents a number of studies into the impact of structural dynamics, unsteady
aerodynamics, and load alleviation on the handling qualities of a flexible civil transport
aeroplane. The handling qualities of the aeroplane are assessed against a number of
different handling qualities criteria and flying specifications, including the Neal-Smith,
Bandwidth, and CAP criterion. It is shown that aeroelastic effects alter the longitudinal
and lateral-directional characteristics of the aeroplane, resulting in degraded handling
qualities. Manoeuvre and gust load alleviation are similarly found to degrade handling
qualities, while active mode control is shown to offer the possibility of improved handling
qualities.
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Yang, Tao. "Development of dynamic phasors for the modelling of aircraft electrical power systems." Thesis, University of Nottingham, 2013. http://eprints.nottingham.ac.uk/13548/.
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As the More-Electric Aircraft (MEA) has been identified as a major trend of future aircraft, the on-board Electrical Power System (EPS) will see significant increased numbers of Power Electronic Converters (PECs) and motor drive systems. In order to study the behaviour and performance of the EPS in MEA, extensive simulation studies need to be done during the system design process. This in return, gives the need to have computationally efficient and accurate models to reduce the design period. In this thesis, the Dynamic Phasor (DP) is used for modelling EPS in the MEA. The DP technique is a general averaging method and naturally a frequency-domain analysis tool. Compared with other averaging models, which is only efficient under balanced conditions, the DP model maintains efficiency under both balanced and unbalanced conditions. The DP technique has been widely used in modelling the constant, single frequency EPS. In this thesis, the DP technique is extended to modelling time-varying frequency EPS. The application of DP in modelling a multi-generator, multi-frequency system is for the first time, developed in this thesis. The developed theory allows a wider application of the DPs. The developed DP model covers key elements in MEA electrical power systems, including the synchronous generator, control, transmission lines, uncontrolled rectifiers, PWM converters and 18-pulse autotransformer rectifier units. The DP model library developed based on this thesis allows the flexibility to study various EPS’s by integrating elements from the library. A twin-generator aircraft EPS, which is based on the More Open Electrical Technology (MOET) large aircraft EPS architecture, is used to demonstrate the application of DP models. Comparing the DP model with the ABC model (models in three-phase coordinates) and the DQ0 model (models in a synchronous dq frame), the efficiency and the accuracy of the DP model are demonstrated under both balanced and unbalanced conditions.
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Velikov, S. "Wind Tunnel Modelling of Aerodynamic Baffle Arrays for Aircraft Exhaust Plume Control." Thesis, Cranfield University, 2015. http://dspace.lib.cranfield.ac.uk/handle/1826/9290.
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Local air quality is one of the factors constraining the development of airports. In
countries of the European Union where new, stricter regulations for emissions of
nitrogen oxides (NOx) have been introduced since 2010, the limits of mean annual
concentrations are already exceeded at certain ground monitoring locations of large
airports. This research project investigates the possibility of abating the aircraft exhaust
plume at take-off by placing an array of aerodynamic windbreaks (‘baffles’) in the
runway end safety area close to the aircraft starting position.
The undertaken experimental investigation comprised sub-scale wind tunnel tests
and full-scale field trials with a BAe 146-301 aircraft, performing take-off and landing
cycles at Cranfield Airport. The initial wind tunnel experiments investigated the effect
of a solid baffle row, placed in the path of a buoyant nozzle jet, on the development of
the plume downstream. Using flow visualisation, the positive effect of the baffle row of
promoting buoyant rise of the plume away from the ground was demonstrated
successfully without the presence of wind tunnel flow. The investigation highlighted the
importance of the distance of the baffles relative to the jet source on their effectiveness.
In the presence of wind tunnel flow, the baffles caused an increased vertical spread of
the plume downstream, but the plume was not observed to separate from the ground.
In preparation of the field trials, the spatial arrangement of the baffle array was
investigated by means of wind tunnel drag measurements, performed with a skinfriction
balance. The experiments focused on key parameters such as the baffle slope
angle and row spacing, favouring a configuration of three rows of baffles of increasing
height. Based on the wind tunnel measurements, full-scale baffle prototypes were
designed and manufactured at Cranfield University and were deployed in the field trials.
Lidar and point sampler measurements during the field trials suggested that the
plume had risen away from the ground on one occasion when the aircraft was located
close to the baffles. A positive effect was shown in terms of reduced concentrations
downstream of the baffles. This result was not replicated when the aircraft was further
away from the baffles.
The subsequent wind tunnel experiments focused on replicating the field trials at
1:200 scale in Cranfield’s Atmospheric Boundary Layer Wind Tunnel. The aircraft was
represented at sub scale with a single stationary nozzle while the jet speed and buoyancy
were modelled using similarity parameters such as the Froude number and the ratio of
ambient and jet density. Mean concentration measurements were performed using a
Flame Ionisation Detector method releasing methane as tracer gas. The effect of the
baffles was observed to be mainly local in terms of reduced concentrations close the
ground due to their sheltering effect. A more prolonged effect was found to be the increase of the plume’s vertical spread resulting in an increase in mean concentrations
away from the ground.
39
Velikov, S. "Wind tunnel modelling of aerodynamic baffle arrays for aircraft exhaust plume control." Thesis, Cranfield University, 2014. http://dspace.lib.cranfield.ac.uk/handle/1826/9290.
Full textAbstract:
Local air quality is one of the factors constraining the development of airports. In countries of the European Union where new, stricter regulations for emissions of nitrogen oxides (NOx) have been introduced since 2010, the limits of mean annual concentrations are already exceeded at certain ground monitoring locations of large airports. This research project investigates the possibility of abating the aircraft exhaust plume at take-off by placing an array of aerodynamic windbreaks (‘baffles’) in the runway end safety area close to the aircraft starting position. The undertaken experimental investigation comprised sub-scale wind tunnel tests and full-scale field trials with a BAe 146-301 aircraft, performing take-off and landing cycles at Cranfield Airport. The initial wind tunnel experiments investigated the effect of a solid baffle row, placed in the path of a buoyant nozzle jet, on the development of the plume downstream. Using flow visualisation, the positive effect of the baffle row of promoting buoyant rise of the plume away from the ground was demonstrated successfully without the presence of wind tunnel flow. The investigation highlighted the importance of the distance of the baffles relative to the jet source on their effectiveness. In the presence of wind tunnel flow, the baffles caused an increased vertical spread of the plume downstream, but the plume was not observed to separate from the ground. In preparation of the field trials, the spatial arrangement of the baffle array was investigated by means of wind tunnel drag measurements, performed with a skinfriction balance. The experiments focused on key parameters such as the baffle slope angle and row spacing, favouring a configuration of three rows of baffles of increasing height. Based on the wind tunnel measurements, full-scale baffle prototypes were designed and manufactured at Cranfield University and were deployed in the field trials. Lidar and point sampler measurements during the field trials suggested that the plume had risen away from the ground on one occasion when the aircraft was located close to the baffles. A positive effect was shown in terms of reduced concentrations downstream of the baffles. This result was not replicated when the aircraft was further away from the baffles. The subsequent wind tunnel experiments focused on replicating the field trials at 1:200 scale in Cranfield’s Atmospheric Boundary Layer Wind Tunnel. The aircraft was represented at sub scale with a single stationary nozzle while the jet speed and buoyancy were modelled using similarity parameters such as the Froude number and the ratio of ambient and jet density. Mean concentration measurements were performed using a Flame Ionisation Detector method releasing methane as tracer gas. The effect of the baffles was observed to be mainly local in terms of reduced concentrations close the ground due to their sheltering effect. A more prolonged effect was found to be the increase of the plume’s vertical spread resulting in an increase in mean concentrations away from the ground.
40
Bradley, Luke R. "Mechanical testing and modelling of carbon-carbon composites for aircraft disc brakes." Thesis, University of Bath, 2003. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.426204.
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Morgan, Luke N. C. "The development of SQUID-based NDE through experimentation and computational modelling." Thesis, University of Strathclyde, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.366527.
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Sillén, Mattias. "Application of Parallel Computers to Enhance the Flow Modelling Capability in Aircraft Design." Licentiate thesis, Linköping University, Linköping University, Department of Management and Engineering, 2006. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-6398.
Full textAbstract:
The development process for new aircraft configurations needs to be more efficient in terms of performance, cost and time to market. The potential to influence these factors is highest in early design phases. Thus, high confidence must be established in the product earlier than today. To accomplish this, the concept of virtual product development needs to be established. This implies having a mathematical representation of the product and its associated properties and functions, often obtained through numerical simulations. Building confidence in the product early in the development process through simulations postpones expensive testing and verification to later development stages when the design is more mature.
To use this in aerodynamic design will mean introducing more advanced physical modelling of the flow as well as significantly reducing the turn around time for flow solutions.
This work describes the benefit of using parallel computers for flow simulations in the aircraft design process. Reduced turn around time for flow simulations is a prerequisite for non-linear flow modelling in early design stages and a condition for introducing high-end turbulence models and unsteady simulations in later stages of the aircraft design process. The outcome also demonstrates the importance of bridging the gap between the research community and industrial applications.
The computer platforms are very important to reduce the turn around time for flow simulations. With the recent popularity of Linux–clusters it is now possible to design cost efficient systems for a specific application. Two flow solvers are investigated for parallel
performance on various clusters. Hardware and software factors influencing the efficiency are analyzed and recommendations are made for cost efficiency and peak performance.
Report code: LiU-TEK-LIC-2006:27.
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Chan, Kwok Wing. "The introduction of a condition monitoring approach into the design of aircraft systems." Thesis, University of the West of England, Bristol, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.321833.
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Blake, Simon. "The development and use of aircraft evacuation modelling as a viable tool for the certification and safety analysis of passenger aircraft." Thesis, University of Greenwich, 2003. http://gala.gre.ac.uk/6115/.
Full textAbstract:
Evacuation modelling technology offers designers and regulators of aircraft new opportunities to rigorously test designs and theories. However, before evacuation models can be used effectively they need to be understood by the regulatory and aviation industry, validated and developed further. This thesis tackles each of these aspects. This thesis provides a detailed review of evacuation modelling with special emphasis on aviation evacuation models and the available data upon which models and understanding can be based. Of these the airEXODUS model is selected for this thesis and it is described in detail and critically evaluated. The evaluation revealed three main issues that needed to be addressed in order for aircraft evacuation modelling to advance. These issues relate to, (1) the limited quantity of model verification, (2) the inability of models to represent crew procedures, and (3) the limited behavioural capabilities of these models with regard to simulating real accidents as opposed to certification scenarios. The fundamental accuracy and predictive capability of airEXODUS is evaluated. This is followed by a comprehensive investigation of cabin crew and passenger behaviour in 90-second certification trials and real emergency evacuations. The conclusions from this investigation serve as the basis for the development of new algorithms to addresses issues (2) and (3). Behavioural algorithms are developed to simulate cabin crew bypass in conjunction with algorithms for passengers exit choice and methods for simulated passengers to optimise their chosen route to an exit. Finally, this thesis concludes by demonstrating the value of evacuation modelling in the design of future aircraft, the regulation of current aircraft and in understanding some of the contributing factors involved in past evacuation related disasters.
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Mert, Ahmet. "Modelling And Controller Design Of The Gun And Turret System For An Aircraft." Master's thesis, METU, 2009. http://etd.lib.metu.edu.tr/upload/3/12610429/index.pdf.
Full textAbstract:
Gun and gun turret systems are the primary units of the weapon systems of an aircraft. They are required to hit targets accurately during operations. That is why a complete, high precision control of weapon systems is required. This function is provided by accurate modeling of the system and the design of a suitable controller.
This study presents the modeling of and controller design for the gun and turret system for an aircraft. For the controller design purpose, first the mathematical model of the system is constructed. Then the controller is designed to position the
turret system as the target comes into sight. The reference input to the controller will either be obtained from a FLIR (Forward Looking Infrared) unit or from a HCU (Hand Control Unit). The basic specification for the controller is to hold theerror signal within the 5.5°positioning envelope. This specification is satisfied by designing Linear Quadratic Gaussian and Internal Model Control type controllers. The performance of the overall system has been examined both by simulation studies and on the real physical system. Results have shown that the designed system is well over being sufficient.
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Sillén, Mattias. "Application of parallel computers to enhance the flow modelling capability in aircraft design /." Linköping : Department of Mechanical Engineering, Linköpings universitet, 2006. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-6398.
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Materano, Blanco Gilberto Ignacio. "Numerical modelling of pressure rise combustion for reducing emissions of future civil aircraft." Thesis, Cranfield University, 2014. http://dspace.lib.cranfield.ac.uk/handle/1826/9259.
Full textAbstract:
This work assesses the feasibility of designing and implementing the wave rotor
(WR), the pulse detonation engine (PDE) and the internal combustion wave
rotor (ICWR) as part of novel Brayton cycles able to reduce emissions of future
aircraft. The design and evaluation processes are performed using the
simplified analytical solution of the devices as well as 1D-CFD models. A code
based on the finite volume method is built to predict the position and
dimensions of the slots for the WR and ICWR. The mass and momentum
equations are coupled through a modified SIMPLE algorithm to model
compressible flow. The code includes a novel tracking technique to ensure the
global mass balance. A code based on the method of characteristics is built to
predict the profiles of temperature, pressure and velocity at the discharge of the
PDE and the effect of the PDEs array when it operates as combustion chamber
of gas turbines. The detonation is modelled by using the NASA-CEA code as a
subroutine whilst the method of characteristics incorporates a model to capture
the throttling and non-throttling conditions obtained at the PDE's open end
during the transient process. A medium-sized engine for business jets is
selected to perform the evaluation that includes parameters such as specific
thrust, specific fuel consumption and efficiency of energy conversion. The ICWR
offers the best performance followed by the PDE; both options operate with a
low specific fuel consumption and higher specific thrust. The detonation in an
ICWR does not require an external source of energy, but the PDE array
designed is simple. The WR produced an increase in the turbine performance,
but not as high as the other two devices. These results enable the statement
that a pressure rise combustion process behaves better than pressure
exchangers for this size of gas turbine. Further attention must be given to the
NOx emission, since the detonation process is able to cause temperatures
above 2000 K while dilution air could be an important source of oxygen.
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Abramov, Nikolay. "Modelling of unsteady aerodynamic characteristics for aircraft dynamics applications at high incidence flight." Thesis, De Montfort University, 2005. http://hdl.handle.net/2086/4108.
Full textAbstract:
A traditional representation of aerodynamic characteristics based on the concept of aerodynamic derivatives fails to be accurate at high angles of attack due to significant dynamic effects generated from separated and vortical flow. As the possibility of performing controlled flight at high angles of attack has already become a common requirement for modern combat aircraft, the problem of an adequate model for aerodynamic loads at high incidences is the issue of the day. This thesis presents a phenomenological approach to modelling of unsteady aerodynamic characteristics at high angles of attack. In this approach aerodynamic characteristics are considered as a combination of two components having different characteristic time scales which describe the contribution to the total aerodynamic load from the different flow structures. It is assumed that all dynamic properties of the flow are amassed in the' slow' component. To describe its behaviour specially designed nonlinear differential equations are used. Depending on the parameters, this model can reproduce both 'weak' and 'strong' nonlinear effects including static hysteresis. A special identification technique has been developed for the estimation of the model parameters using dynamic wind tunnel test data.
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Köhler, Marcus Oliver. "Modelling the global impact of nitrogen oxides from subsonic aircraft emissions on ozone." Thesis, University of Cambridge, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.615951.
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Lee, Brian P. "Pilot and control system modelling for handling qualities analysis of large transport aircraft." Thesis, Cranfield University, 2012. http://dspace.lib.cranfield.ac.uk/handle/1826/10203.
Full textAbstract:
The notion of airplane stability and control being a balancing act between
stability and control has been around as long as aeronautics. The Wright
brothers’ first successful flights were born of the debate, and were successful at
least in part because they spent considerable time teaching themselves how to
control their otherwise unstable airplane.
This thesis covers four aspects of handling for large transport aircraft: large
size and the accompanying low frequency dynamics, the way in which lifting
surfaces and control system elements are modelled in flight dynamics analyses,
the cockpit feel characteristics and details of how pilots interact with them, and
the dynamic instability associated with Pilot Induced Oscillations.
The dynamics associated with large transport aircraft are reviewed from the
perspective of pilot-in-the-loop handling qualities, including the effects of
relaxing static stability in pursuit of performance. Areas in which current design
requirements are incomplete are highlighted. Issues with modelling of dynamic
elements which are between the pilot’s fingers and the airplane response are
illuminated and recommendations are made.
Cockpit feel characteristics are examined in detail, in particular, the nonlinear
elements of friction and breakout forces. Three piloted simulation experiments
are described and the results reviewed. Each was very different in nature, and
all were designed to evaluate linear and nonlinear elements of the cockpit feel
characteristics from the pilot’s point of view. These included understanding the
pilot’s ability to precisely control the manipulator itself, the pilot’s ability to
command the flight path, and neuro-muscular modelling to gain a deeper
understanding of the range of characteristics pilots can adapt to and why.
Based on the data collected and analyzed, conclusions are drawn and
recommendations are made. Finally, a novel and unique PIO prediction criterion is developed, which is based
on control-theoretic constructs. This criterion identifies unique signatures in the
dynamic response of the airplane to predict the onset of instability.