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Technical Paper

Method for the Exploration of Cause and Effect Links and Derivation of Causal Trees from Accident Reports

The ultimate goal of knowledge-based aircraft design, pilot training and flight operations is to make flight safety an inherent, built-in feature of the flight vehicle, such as its aerodynamics, strength, economics and comfort are. Individual flight accidents and incidents may vary in terms of quantitative characteristics, circumstances, and other external details. However, their cause-and-effect patterns often reveal invariant structure or essential causal chains which may re-occur in the future for the same or other vehicle types. The identification of invariant logical patterns from flight accident reports, time-histories and other data sources is very important for enhancing flight safety at the level of the ‘pilot - vehicle -operational conditions’ system. The objective of this research project was to develop and assess a method for ‘mining’ knowledge of typical cause-and-effect patterns from flight accidents and incidents.
Technical Paper

Implementation of a Physics-Based Decision-Making Framework for Evaluation of the Multidisciplinary Aircraft Uncertainty

In today's business climate, aerospace companies are more than ever in need of rational methods and techniques that provide insights as to the best strategies which may be pursued for increased profitability and risk mitigation. However, the use of subjective, anecdotal decision-making remains prevalent due to the absence of analytical methods capable of capturing and forecasting future needs. Negotiations between airframe and engine manufacturers could benefit greatly from a structured environment that facilitates efficient, rational, decision-making. Creation of such an environment can be developed through a parametric physics-based, stochastic formulation that uses Response Surface Equations as meta-models to expedite the process.
Technical Paper

Implementation of Parametric Anaylsis to the Aerodynamic Design of a Hypersonic Strike Fighter

A Hypersonic Strike Fighter (HSF) would provide many benefits over current fighters, including increased effectiveness and survivability. However, there are many design challenges to developing such a vehicle. Therefore the conceptual design of an HSF requires the development of new tools and methods to analyze and select vehicle concepts. A parametric method was developed to determine aerodynamic characteristics of hypersonic vehicles in a rapid, automated way. This parametric method and other tools were then used to select a baseline design and optimize this baseline for the notional mission.
Technical Paper

Formulation, Realization, and Demonstration of a Process to Generate Aerodynamic Metamodels for Hypersonic Cruise Vehicle Design

The desire to facilitate the conceptual and preliminary design of hypersonic cruise vehicles has created the need for simple, fast, versatile, and trusted aerodynamic analysis tools. Metamodels representing physics-based engineering codes provide instantaneous access to calibrated tools. Nonlinear transformations extend the capability of metamodels to accurately represent a large design space. Independence, superposition, and scaling properties of the hypersonic engineering method afford an expansive design space without traditional compounding penalties. This one-time investment results in aerodynamic and volumetric metamodels of superior quality and versatility which may be used in many forms throughout early design. As a module, they can be an integral component within a multidisciplinary analysis and optimization package. Aerodynamic polars they produce may provide performance information for mission analysis.
Technical Paper

Development of Wing Structural Weight Equation for Active Aeroelastic Wing Technology

A multidisciplinary design study considering the impact of Active Aeroelastic Wing (AAW) technology on the structural wing weight of a lightweight fighter concept is presented. The study incorporates multidisciplinary design optimization (MDO) and response surface methods to characterize wing weight as a function of wing geometry. The study involves the sizing of the wing box skins of several fighter configurations to minimum weight subject to static aeroelastic requirements. In addition, the MDO problem makes use of a new capability, trim optimization for redundant control surfaces, to accurately model AAW technology. The response surface methodology incorporates design of experiments, least squares regression, and makes use of the parametric definition of a structural finite element model and aerodynamic model to build response surface equations of wing weight as a function of wing geometric parameters for both AAW technology and conventional control technology.
Technical Paper

Development of Response Surface Equations for High-Speed Civil Transport Takeoff and Landing Noise

As an element of a design optimization study of high speed civil transport (HSCT), response surface equations (RSEs) were developed with the goal of accurately predicting the sideline, takeoff, and approach noise levels for any combination of selected design variables. These RSEs were needed during vehicle synthesis to constrain the aircraft design to meet FAR 36, Stage 3 noise levels. Development of the RSEs was useful as an application of response surface methodology to a previously untested discipline. Noise levels were predicted using the Aircraft Noise Prediction Program (ANOPP), with additional corrections to account for inlet and exhaust duct lining, mixer-ejector nozzles, multiple fan stages, and wing reflection. The fan, jet, and airframe contributions were considered in the aircraft source noise prediction.
Technical Paper

An Improved Process for the Generation of Drag Polars for use in Conceptual/Preliminary Design

One of the most essential contributors in the aircraft sizing and synthesis process is the creation and utilization of accurate drag polars. An improved general procedure to generate drag polars for conceptual and preliminary design purposes in the form of Response Surface Equations is outlined and discussed in this paper. This approach facilitates and supports aerospace system design studies as well as Multi-disciplinary Analysis and Optimization. The analytically created Response Surface Equations replace the empirical aerodynamic relations or historical data found in sizing and synthesis codes, such as the Flight Optimization System (FLOPS). These equations are commonly incorporated into system level studies when a configuration falls beyond the conventional realm. The approach described here is a statistics-based methodology, which combines the use of Design of Experiments and Response Surface Method (RSM).
Technical Paper

An Improved Procedure for Prediction of Drag Polars of a Joined Wing Concept Using Physics-Based Response Surface Methodology

Creation and utilization of accurate drag polars is essential in the aircraft sizing and synthesis process. Existing sizing and synthesis codes are based on historical data and cannot capture the aerodynamics of a non-conventional aircraft at the conceptual design phase. The fidelity of the aerodynamic analysis should be enhanced to increase the designer’s confidence in the results. Hence, there is need for a physics-based approach to generate the drag polars of an aircraft lying outside the conventional realm. The deficiencies of the legacy codes should be removed and replaced with higher fidelity meta-model representations. This is facilitated with response surface methodology (RSM), which is a mathematical and statistical technique that is suited for the modeling and analysis of problems in which the responses, the drag coefficients in this case, are influenced by several variables. The geometric input variables are chosen so that they represent a multitude of configurations.
Technical Paper

An Automated Robust Process for Physics Based Aerodynamic Prediction

By Combining the Response Surface Methodology with a classical Design of Experiments formulation, a robust method was developed to facilitate the aerodynamic analysis of conceptual designs. These aerodynamic predictions, presented in a parametric form, can then be furnished to a sizing and synthesis code for further evaluation of the concept at the system level. The computational basis of this methodology is a set of numerical codes that work in unison to both optimize the geometry for minimal drag and evaluate key aerodynamic parameters such as lift, friction, wave and induced drag coefficients. Code fidelity and sensitivity to a wide variety of input parameters such as aircraft geometry, panel layout, number of panels used, flow theory used within the numerical code, etc. was investigated. The numerical results were compared with experimental data for different configurations, and the code input parameters required for the best correlation were grouped according to aircraft type.