This thesis discusses the research and development of a program to aid the aircraft designer with determining the pilot's visual acuity. The discussion involves the use of Object-Oriented programming, the use of a graphical user interface based upon the graphics standard PHIGS (Programmers Hierarchical interactive Graphics System) and the integration of this Pilot's View Module with an existing aircraft CAD (Computer Aided Design) program known as ACSYNT. The result is a program that lends itself to reuse and easy modification and is device independent. The main purpose of the pilot's view module is to provide total vision plots for the pilot in accordance with the military standards as stated in the document 850B. These standards include visibility design goals for several types of aircraft as well as methods for calculating and presenting the vision plots. The integration of the pilots view module with ACSYNT affords the designer the ability to examine the trade-offs associated with a particular cockpit design and the performance of that design within one CAD program. / Master of Science

A methodology for the conceptual design phase risk assessment of an aerospace system was proposed. The method was designed to examine political, social, and economic risk over a systems lifecycle through the use of future scenarios to bound uncertainty. A decision support framework was developed to allow the user to visualize the differences in performance and economic metrics between design options as well as allowing the user to visualize the effects of mitigating certain risks. A historical proof of concept was developed to test the methodology. The results indicated that the new method will work to examine political, social, and economic risk during conceptual level design, and that this information can be used to aid in design down-selection and decision making. The use of scenario-based analysis as an alternative to traditional probabilistic analysis allowed for better traceability and bounding of uncertainty. Other findings regarding the use of a risk analysis early during concept design and future work are also discussed.

Call number: LD2668 .T4 1986 H44 / Master of Arts / History

The design of unconventional aircraft requires early use of high-fidelity physics-based tools to search the unfamiliar design space for optimum designs. Current methods for incorporating high-fidelity tools into early design phases for the purpose of reducing uncertainty are inadequate due to the severely restricted budgets that are common in early design as well as the unfamiliar design space of advanced aircraft. This motivates the need for a robust and efficient global optimization algorithm. This research presents a novel surrogate model-based global optimization algorithm to efficiently search challenging design spaces for optimum designs. The algorithm searches the design space by constructing a fully Bayesian Gaussian process model through a set of observations and then using the model to make new observations in promising areas where the global minimum is likely to occur. The algorithm is incorporated into a methodology that reduces failed cases, infeasible designs, and provides large reductions in the objective function values of design problems. Results on four sets of algebraic test problems are presented and the methodology is applied to an airfoil section design problem and a conceptual aircraft design problem. The method is shown to solve more nonlinearly constrained algebraic test problems than state-of-the-art algorithms and obtains the largest reduction in the takeoff gross weight of a notional 70-passenger regional jet versus competing design methods.

Current aircraft conceptual design practices result in the selection of a single (hopefully) Pareto optimal design to be carried forward into preliminary design. This paradigm is based on the assumption that carrying a significant number of concepts forward is too costly and thus early down-selection between competing concepts is necessary. However, this approach requires that key architectural design decisions which drive performance and market success are fixed very early in the design process, sometimes years before the aircraft actually goes to market. In the presence of uncertainty, if the design performance is examined for individual scenarios as opposed to measuring performance of the design with aggregate statistics, the author finds that the single concept approach can lead to less than desirable design outcomes. This thesis proposes an alternate conceptual design paradigm which leverages principles from economics (specifically the Nobel prize-winning modern portfolio theory) to improve design outcomes by intelligently selecting a small well diversified portfolio of concepts to carry forward through preliminary design, thus reducing the risk from external events that are outside of the engineer’s control. This alternate paradigm is expected to result in an increase in the overall profit by increasing the probability that the final design matches market needs at the time it goes to market. This thesis presents a portfolio based design approach, which leverages dynamic programming to enable a stochastic optimization of alternative portfolios of concepts. This optimization returns an optimized portfolio of concepts which are iteratively pruned to improve design outcomes in the presence of scenario-driven uncertainties. While dynamic programming is identified as a means for doing a stochastic portfolio optimization, dynamic programming is an analytical optimization process which suffers heavily from the curse of dimensionality. As a result, a new hybrid stochastic optimization process called the Evolutionary Cooperative Optimization with Simultaneous Independent Sub-optimization (ECOSIS) has been introduced. The ECOSIS algorithm leverages a co-evolutionary algorithm to optimize a multifaceted problem under uncertainty. ECOSIS allows for a stochastic portfolio optimization including the desired benefit-to-cost tradeoff for a well-diversified portfolio at the size and scope required for use in design problems. To demonstrate the applicability and value of a portfolio based design approach, an example application of the approach to the selection of a new 300 passenger aircraft is presented.

Modern aerospace systems rely heavily on legacy platforms and their derivatives. Historical examples show that after a vehicle design is frozen and delivered to a customer, successive upgrades are often made to fulfill changing requirements. Current practices of adapting to emerging needs with derivative designs, retrofits, and upgrades are often reactive and ad-hoc, resulting in performance and cost penalties. Recent DoD acquisition policies have addressed this problem by establishing a general paradigm for design for lifelong evolution. However, there is a need for a unified, practical design approach that considers the lifetime evolution of an aircraft concept by incorporating future requirements and technologies. This research proposes a systematic approach with which the decision makers can evaluate the value and risk of a new aircraft development program, including potential derivative development opportunities. The proposed Evaluation of Lifelong Vehicle Evolution (EvoLVE) method is a two- or multi-stage representation of the aircraft design process that accommodates initial development phases as well as follow-on phases. One of the key elements of this method is the Stochastic Programming with Recourse (SPR) technique, which accounts for uncertainties associated with future requirements. The remedial approach of SPR in its two distinctive problem-solving steps is well suited to aircraft design problems where derivatives, retrofits, and upgrades have been used to fix designs that were once but no longer optimal. The solution approach of SPR is complemented by the Risk-Averse Strategy Selection (RASS) technique to gauge risk associated with vehicle evolution options. In the absence of a full description of the random space, a scenario-based approach captures the randomness with a few probable scenarios and reveals implications of different future events. Last, an interactive framework for decision-making support allows simultaneous navigation of the current and future design space with a greater degree of freedom. A cantilevered beam design problem was set up and solved using the SPR technique to showcase its application to an engineering design setting. The full EvoLVE method was conducted on a notional multi-role fighter based on the F/A-18 Hornet.

Chaque année, d'innombrables collisions se produisent entre des avions en vol et des oiseaux. L'impact aviaire, menace redoutée par les pilotes, concerne tant l'aviation civile que son pendant militaire. Les statistiques démontrent que, même si fort heureusement le nombre d'accidents graves reste limité, les incidents sont de plus en plus nombreux.<p>Parmi les acteurs qui luttent contre ce danger, les constructeurs d'avions jouent un rôle prépondérant. Contraints par des réglementations internationales, ils s'attachent à produire des éléments de structure qui résistent à l'impact d'oiseaux.<p>Dans la mise au point de leur produits, les avionneurs démontrent cette résistance à l'aide d'essais d'impact :on accélère un simulant d'oiseau jusqu'à la vitesse voulue -- de l'ordre de la vitesse de croisière nominale de l'avion -- et on le projette sur un aileron ou un morceau de fuselage. <p><p>La présente thèse doctorale, co-dirigée par les professeurs Philippe Bouillard de l'ULB et Marc Pirlot de l'ERM, contribue doublement à l'amélioration de ces techniques d'essais dynamiques.<p><p><p>D'une part, elle réalise la mise au point et la validation d'un lanceur pyrotechnique à double étage pour l'accélération du simulant d'oiseau. Un canon de calibre 20 mm est combiné avec un accélérateur de calibre 160 mm. La combustion d'un mélange de poudre propulsive contenu dans une douille adaptée génère les gaz à haute température et à haute pression nécessaires à l'accélération d'un simulant d'oiseau dûment confiné dans un conteneur de protection. Un dispositif de séparation arrête le conteneur afin que seul le simulant d'oiseau percute l'élément d'avion à l'essai. La solution pyrotechnique à double étage mise au point est validée par de nombreux tirs instrumentés en vitesse, en accélération et en pression ;elle se révèle conforme aux exigences de sécurité et de reproductibilité. Le lanceur pyrotechnique présente par rapport aux solutions pneumatiques, utilisées à notre connaissance dans tous les autres centres d'essais, des avantages indéniables de compacité ainsi que de rapidité et de souplesse de mise en oeuvre.<p><p><p>D'autre part, la migration des alliages métalliques vers les matériaux composites est amorcée depuis plusieurs années déjà dans le monde de la construction aéronautique. Pour optimiser les structures, une connaissance des caractéristiques de ces matériaux est indispensable. Les modes de rupture font partie des caractéristiques encore mal connues. La mesure du déplacement hors-plan lors du tir sur panneaux plans est une des manières de quantifier le comportement du matériau sous l'action d'un impact. Cette mesure s'opère généralement de manière statique, après le tir. Une méthode de mesure dynamique a été mise au point, basée sur l'emploi de techniques de stéréoscopie par corrélation numérique d'images. Cette technique a été validée au moyen d'une méthode métrologique indépendante d'extensométrie laser. <p><p><p>ABSTRACT<p><p>Countless collisions occur each year between airplanes and birds. Bird strike is a concern to both civilian and militay aircraft. Statistics show that, although the number of serious accidents fortunately remains low, the number of incidents keeps increasing.<p>Amongst the actors tackling this issue, aircraft manufacturers play an important role. In compliance with international regulations, they have to produce structural elements that withstand bird impact. During the development of their products, aircraft manufacturers have to demonstrate this resistance through bird impact trials :a bird surrogate is accelerated to the required velocity - often close to the nominal cruise speed of the aircraft - and launched onto a flap or a piece of fuselage.<p><p>This PhD thesis has been co-supervised by Professor Philippe Bouillard (ULB) and Professor Marc Pirlot (ERM-KMS). Its contribution to the improvement of the aforementioned dynamic trials is twofold.<p><p><p>One one hand, a two-stage pyrotechnical launcher for bird surrogates has been developed and assessed. A 20 mm caliber gun is connected to a 160 mm diameter launcher. The combustion of a propellant mixture in a cartridge case generates high pressure, high temperature gases which accelerate a bird surrogate protected by a cylindrical container. A stripper refrains the container from hitting the target pane. <p>The pyrotechnical solution has been assessed through an important number of firings where pressure, velocity and acceleration have been measured. The solution has proven compliance with both the safety requirements and the repeatability specifications. Its advantages compared to the pneumatic solutions used, as far as we know, in all other test centres, include compactedness as well as flexibility and high firing rate.<p><p><p>On the other hand, migration towards composite materials has been initiated years ago in the area of aeronautical constructions.<p>To optimize structures, a thorough knowledge of these new materials is required. Failure modes belong to the still badly known features of carbon reinforced plastics. Measuring the out-of-plane deformation when firing on a flat pane is one way of quantifying the material's behaviour under impact. This measurement is most frequently made in a static way, after completion of the firing. A dynamic measuring method has been developed, based upon stereoscopic digital image correlation techniques. This technique has been validated by means of an independent laser extensometer measuring method. <p> / Doctorat en Sciences de l'ingénieur / info:eu-repo/semantics/nonPublished

In the last half century, the aerospace industry has seen a dramatic paradigm shift from a focus on performance-at-any-cost to product economics and value. The steady increase in product requirements, complexity and global competition has driven aircraft manufacturers to seek broad portfolios of advanced technologies. The development costs and cycle times of these technologies vary widely, and the resulting design environment is one where decisions must be made under substantial uncertainty. Modeling and simulation have recently become the standard practice for addressing these issues; detailed simulations and explorations of candidate future states of these systems help reduce a complex design problem into a comprehensible, manageable form where decision factors are prioritized. While there are still fundamental criticisms about using modeling and simulation, the emerging challenge becomes ``How do you best configure uncertainty analyses and the information they produce to address real world problems?” One such analysis approach was developed in this thesis by structuring the input, models, and output to answer questions about the risk and economic impact of technology decisions in future aircraft programs. Unlike other methods, this method placed emphasis on the uncertainty in the cumulative cashflow space as the integrator of economic viability. From this perspective, it then focused on exploration of the design and technology space to tailor the business case and its associated risk in the cash flow dimension. The methodology is called CASSANDRA and is intended to be executed by a program manager of a manufacturer working of the development of future concepts. The program manager has the ability to control design elements as well as the new technology allocation on that aircraft. She is also responsible for the elicitation of the uncertainty in those dimensions within control as well as the external scenarios (that are out of program control). The methodology was applied on a future single-aisle 150 passenger aircraft design. The overall methodology is compared to existing approaches and is shown to identify more economically robust design decisions under a set of at-risk program scenarios. Additionally, a set of metrics in the uncertain cumulative cashflow space were developed to assist the methodology user in the identification, evaluation, and selection of design and technology. These metrics are compared to alternate approaches and are shown to better identify risk efficient design and technology selections. At the modeling level, an approach is given to estimate the production quantity based on an enhanced Overall Evaluation Criterion method that captures the competitive advantage of the aircraft design. This model was needed as the assumption of production quantity is highly influential to the business case risk. Finally, the research explored the capacity to generate risk mitigation strategies in to two analysis configurations: when available data and simulation capacity are abundant, and when they are sparse or incomplete. The first configuration leverages structured filtration of Monte Carlo simulation results. The allocation of design and technology risk is then identified on the Pareto Frontier. The second configuration identifies the direction of robust risk mitigation based on the available data and limited simulation ability. It leverages a linearized approximation of the cashflow metrics and identifies the direction of allocation using the Jacobian matrix and its inversion.