A thesis submitted to the Faculty of Engineering, University of the Witwatersrand, Johannesburg, in fulfillment of the requirements for the degree of Master of Science in Engineering. / The use of advanced composite materials in helicopter rotor systems offers opportunities for improvements in aerodynamic geometry, performance, weight, damage tolerarice, maintenance and operating costs. Technical aspects of the design and analysis and the-practical aspects of the manufacture of a composite rotor system are discussed herein. The rotor system was compared to an existing conventional teetering rotor system, in order to establish the viability of the new composite rotor system, This rotor system reduced the number of components by 55% and the manufacturing time by half, due to the simplicity of the design and lay up procedure, thus making the system economically more viable. The mass was predicted to within 1% of that achieved in practice and gave a mass advantage of 50.5% over the conventional rotor. Static tests identified the failure modes and stress concentration points, while. the comparative hover tests showed the system to have ±20% less drag. [Abbreviated Abstract. Open document to view full version] / AC2017

This study presents a discrete adjoint-based aerodynamic optimization algorithm for helicopter rotor blades in hover and forward flight using a Non-Linear Frequency Domain approach. The goal is to introduce a Mach number variation into the Non-Linear Frequency Domain (NLFD) method and implement a novel approach to present a time-varying cost function through a multi-objective adjoint boundary condition. The research presents the complete formulation of the time dependent optimal design problem. The approach is firstly demonstrated for the redesign of a NACA 0007 and a NACA 23012 helicopter rotor blade section in forward flight. A three-dimensional inviscid Aerodynamic Shape Optimization (ASO) algorithm is then employed to validate and redesign the Caradonna and Tung experimental blade. The results in determining the optimum aerodynamic configurations require an objective function which minimizes the inviscid torque coefficient and maintains the desired thrust level at transonic conditions.

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The purpose of this research was to develop parametric Design-to-Cost models for selected major subsystems of certain helicopters. This was accomplished by analyzing the relationships between historical production costs and certain design parameters which are available during the preliminary design phase of the life cycle. Several potential contributions are identified in the areas of academia, government, and industry. Application of the cost models will provide estimates beneficial to the government and DoD by allowing derivation of realistic Design-to-Cost estimates. In addition, companies in the helicopter industry will benefit by using the models for two key purposes: (1) optimizing helicopter design through cost-effective tradeoffs, and (2) justifying a proposal estimate.

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With the advent of variable geometric wing surfaces providing noticeable performance improvements in fixed wing aircraft, a theoretical study of the performance advantages of variable geometry designs for rotary wing aircraft is presented. The analysis is developed in three sections, namely: 1) Theoretical justification of variable geometry through application of simple blade element equations; 2) A simplified design proposal to implement variable geometry in rotor systems; and 3) A numerical comparison of fixed and variable geometry performance statistics applied to specifications of an actual helicopter. / Master of Engineering

The atmospheric boundary layer (ABL) is the layer of air directly influenced by the Earth’s surface and is the layer of the atmosphere most important to humans as this is the air we live in. Methods for measuring the properties of the ABL include three general approaches: satellite-based, ground- based and airborne. A major research challenge is that many contemporary methods provide a restricted spatial resolution or coverage of variations of ABL properties such as how wind speed varies across a landscape with complex topography. To enhance our capacity to measure the properties of the ABL, this thesis presents a new technique that involves a small unmanned aircraft system (sUAS) equipped with a customized payload for measuring wind speed and particulate matter. The research presented herein outlines two key phases in establishing the proof-of-concept of the payload and its integration on the sUAS: (1) design and testing and (2) field demonstration. The first project focuses on measuring wind speed, which has been measured with fixed wing sUASs in previous research, but not with a helicopter sUAS. The second project focuses on the measurement of particulate matter, which is a major air pollutant typically measured with ground- based sensors. Results from both proof-of-concept projects suggest that ABL research could benefit from the proposed techniques.