Improving aircraft conceptual design with methods for wing loads, aeroelasticity and mass estimation

Kurzfassung

This thesis presents the development, validation, and application of methods for the estimation of wing loads, aeroelasticity and mass properties in conceptual design. In advanced design studies, designers rely typically on handbook methods and simple physics-based approaches. Such methods are common due to their flexibility, simplicity, and low computational costs. Nevertheless, when facing new configurations or technologies with expected significant aeroelastic effects, not many simple conceptual design methods are available. This work closes this gap by providing the conceptual aircraft designer with three novel methods: 1) a simple physics-based wing weight estimation approach, 2) a set of accurate wing Weight Estimating Relationships (WERs), and 3) a semi-empirical wing flutter speed estimation method. All methods are validated extensively with actual aircraft data and higher-fidelity results. The physics-based wing weight estimation method is semi-analytical making use of simple numerical extensions. The complexity is kept as low as possible while still capturing most effects of interest. Static aeroelastic effects on the lift distribution, gust response, aeroelastic divergence, and aileron reversal are accounted for. The novel wing Weight Estimating Relationships (WERs) developed are of the typical form found in conceptual design handbooks. Nevertheless, instead of using sparse historical data, the WERs are developed from space filling design of experiments performed with the physics-based method. Validation with more than 25 conventional aircraft shows a standard deviation about 50% lower than comparable methods. Both the physics-based method and the WERs developed are also applicable to advanced concepts such as: forward swept wing, high aspect ratio, strut-braced wing, tailless, and twin fuselage. The semi-empirical wing flutter estimation approach proposed consists of simple analytical equations developed from first principles and dimensional analysis of the flutter equations. Empirical regressions of several higher-fidelity results are applied. The method is useful in quickly estimating the wing flutter speed of new concepts. All methods developed are applied in the conceptual design study of a nextgeneration short-range aircraft with entry into service in 2045. Several concepts are evaluated including: conventional tube and wing, advanced tube and wing with high aspect ratio and laminar flow, forward swept wing, strut-braced wing, forward swept strut-braced wing, tailless, and twin-fuselage. The developed methods allow the fast initial sizing and comparison of several advanced concepts and technologies. Detailed concept development and documentation is presented showing important characteristics of the advanced concepts and technologies.