Semi-Analytical Composite Oval Fuselage Mass Estimation

A semi-analytical weight estimation method is proposed for composite, oval fuselages, but is also applicable to conventional fuselages and to metallic materials. Loads applied to the fuselage include pressurization, steady-state maneuver loads and inertial loads. The primary structure around the passenger cabin is sized, based on first-ply failure using the Tsai-Wu failure criterion, global and local buckling. Moreover, maximum deflection due to transverse pressure is constrained for skin panels and sandwich panels. Sandwich panels are also sized for crippling and wrinkling. Empirical factors are used to calculate secondary structure and non-structural mass. In order to reduce in-the-loop calculation time, surrogate models of the sizing procedures are used, by means of neural networks. Verification of the sizing optimization was done by comparing the sized members with a genetic algorithm and validation of the failure calculations was done by finite-element analysis. It was found that the proposed method is capable of predicting metal, conventional fuselage mass satisfactorily, with acceptable breakdown of weights and estimated thicknesses. Additionally, the method can be used for unconventional aircraft configurations and composite material. Using composite material, a weight saving of around 15% is observed as compared to aluminum.Aerospace EngineeringAerodynamics, Wind Energy & Propulsio

A Graph-based, Probabilistic Framework for Novel Aerospace Technology Evaluation and Selection

Technology selection is ubiquitous in all manners of complex systems engineering, design and everyday business operations. Technologies are often complex entities shrouded in uncertainty, assumptions and interpretation. Therefore, quantifying their effect (i.e. outcome) becomes challenging for several reasons. First, as simulations may not be available for novel technologies, experts have to estimate their impacts. Secondly, as the technologies may not be well-defined, different experts have different interpretations and will assign different outcomes. Thirdly, even if analysis methods are available, there is epistemic and model uncertainty in the outcome. Finally, available analysis frameworks are typically application-specific, non-extensible and inflexible. It is the objective of this thesis to pave the way towards a technology selection methodology that offers a structured, repeatable and traceable way to represent technologies and consecutively quantify their impacts on an engineering system. Such a methodology is implemented as a decision support system, i.e. a computer program that assists a decision maker throughout the decision-making process. Three components of said methodology can be identified: technology representation and portfolio generation, technology (portfolio) evaluation and technology (portfolio) selection...Flight Performance and Propulsio

Technology evaluation and uncertainty-based design optimization: A review

Evaluation and assessment of novel technologies for aerospace applications is essential for business strategy and decision making regarding development efforts. Since technology is evaluated in the conceptual design phase and little is known about the technology, large uncertainty is present. This uncertainty needs to be accurately assessed and managed. To investigate the research efforts that have been performed to perform technology evaluation under uncertainty, a literature review was conducted, focusing on methods and modeling approaches to assign and quantify these uncertainties. It is found that probability theory is still the most popular theory for representing uncertainty. Polynomial Chaos Expansions and Stochastic Collocation methods are gaining popularity for propagating uncertainty through a modeling environment, but Monte Carlo Simulations are still widely used. Commonly, surrogate models are used to reduce computational effort. Other efforts focus on the use of multifidelity approaches to reduce computational effort when high-fidelity methods are required. Four issues that may need to be addressed in future research were identified.Flight Performance and Propulsio

Formalizing Technology Descriptions for Selection During Conceptual Design

Evaluation and assessment of novel technologies for aerospace applications is essential for business strategy and decision making regarding development efforts. However, technology evaluation and assessment are challenging to perform objectively using a structured approach. As a first step towards a more objective and structured approach a graph-based description of engineering systems is described herein. Analyses can be applied to such a description through pattern matching, after which the quantities of interest can be computed by an automated algorithm using a dependency graph. The approach is applied to a simplified aircraft model, to perform a mission analysis and compute fuel burn. It is shown the method successfully computes the required parameter and is easily adapted to analyze an electric aircraft as well.Accepted Author Manuscript “New title: Formalizing Technology Descriptions for Selection During Conceptual Design”Flight Performance and Propulsio

Automatically inferring technology compatibility with an ontology and graph rewriting rules

In conceptual design of any engineering system, decisions are made regarding which technologies to include and where. One of the first stages of that process is constructing the technology compatibility matrix (TCM), which indicates the compatibility of each pair in a technology set. Rather than constructing a TCM with expert judgment, this study develops a method based on graph transformation rules, allowing for a formal description of technologies. The TCM is then automatically derived. An ontology based on the Basic Formal Ontology is developed to describe systems and technologies, and provides axioms to derive statements about these descriptions. The method is demonstrated with four inference examples, showing how the inferences are made. An industry case study demonstrates the method's ability to mimic human expert reasoning. Although the approach is labour-intensive during setup, it enables knowledge capturing, automated reasoning and can be extended to provide quantitative analysis, to save time and effort.Flight Performance and Propulsio

Selecting technologies in aircraft conceptual design using probabilistic inversion

Technology forecasting is an essential starting point for conceptual design of any complex engineering system. In fact, many research projects are focused on developing a small set of promising technologies to a suitable readiness level. However, selecting a set of technologies from a larger pool is a nontrivial task, opposed by uncertainty and subjective tradeoffs. This paper proposes a probabilistic method to represent technologies and quantify their effects, while accounting for uncertainty. Using probabilistic inversion, technologies can be selected from a larger set to meet a certain combination of requirements. Several test cases illustrate the method and how it may be used in conceptual design projects. It is concluded that probabilistic inversion enables answering technology development and selection queries, which would be challenging to answer with traditional deterministic approaches, or purely forward uncertainty propagation approaches.Flight Performance and PropulsionApplied Probabilit

The Effect of Maneuver Load Alleviation Strategies on Aircraft Performance Indicators

The need to reduce the pollutant impact of aircraft emission drives the research on aircraft design progress through off-design performance improvement. This report proposes to investigate the effect of maneuver load alleviation technology via wing control surfaces for this purpose. A methodology is presented to model the MLA technology in aircraft conceptual design and to evaluate its impact on both existing and clean-sheet design. In addition, the possibility to consider flexible wings when under the influence of 2.5-g maneuver loads is addressed, to assess the impact of aeroelasticity in on wing weight in the conceptual design phase. The aeroelastic analysis method is validated against a higher-order analysis method with excellent correlation between the results from the two methods. Subsequently, the method is applied to the redesign of medium-range, single-aisle aircraft. It is shown that applying MLA using both the flaps and the ailerons can result in a fuel burn reduction and maximum take-off mass reduction of 2.1% and 2.2%, respectively.Flight Performance and Propulsio