The anti-torque mechanism of a NOTAR helicopter is a complex system including vertical tail and pressurized tail boom which provides air ejection used for both circulation control around the boom and creating directed jet air at the end of the boom. This thesis targets the modeling of this mechanism and integrating it to a helicopter simulation model. Flight tests are performed on the MD 600N helicopter to verify the results. Finally, the simulation is compared with flight test data.

As the UH-1 aircraft continue to age, there is growing concern for their structural integrity. With corrosion damage becoming a bigger part of the sustainment picture with increasing maintenance burden and cost, it is becoming increasingly important for corrosion management to be updated with more advanced techniques. The current find-and-fix technique for handling corrosion has many shortfalls, spurring the recent interest in early detection through structural health monitoring. This condition based technique is becoming more prevalent and is recognized for the potential to greatly reduce maintenance cost. Through corrosion monitoring, structural and environmental conditions can be closely observed, preventing excessive maintenance action and saving cost. Searches for corrosion monitoring system designs revealed several commercial companies with prototype systems installed on commercial aircraft, however, details on system design and data analysis were scarce. This study attempted to bridge the gap in literature by providing insight into the development of a corrosion damage prediction model and the design of a corrosion monitoring system. This study attempted to use aircraft maintenance data to make prediction models for determining what corrosion damage an aircraft can expect, given varying operating conditions. Although a reliable prediction model could not be created, trends observed in the data were still valuable for identifying problematic areas of the aircraft. In order to create reliable models, more accurate corrosion data is needed. This can be accomplished through the implementation of a corrosion monitoring system. A custom corrosion monitoring system was designed for the UH-1 aircraft. Commercial off-the-shelf products were fit to the design and a benefits-to-cost analysis was performed for the monitoring system, evaluating the system based on criteria developed from user requirements. The system proved to meet and exceed expectation, making it an ideal choice for the UH-1 aircraft.

Arbetet har utförts i syfte att belysa möjligheten för Sjöfartsverket att använda helikopter istället för att allokera lotsar med lotsbåttransport till fartyg. Detta har gjorts i ett ekonomiskt perspektiv genom att använda Payback-metoden. Metoden har använts explorativt där det ekonomiska underlaget från nuvarande verksamhet vid allokering med lotsbåt jämförts med de beräknade kostnaderna för Sjöfartsverkets SAR-helikoptrar om de utför samma transporter. Ingen vikt har lagts vid vilka eventuella processförbättringar detta skulle kunna leda till, utan enbart vad kostnaderna för samma transporter skulle bli med det nya transportsättet. Resultatet har tagits fram utifrån tre aspekter: Hur det ses från lotsningens sida, hur det ses från helikopterfunktionens sida och slutligen vad det kommer att innebära för Sjöfartsverket som helhet. De slutsatser som framkommit är att lotsningsfunktionen får högre kostnader för sina transporter, helikopterverksamheten får mindre möjlighet till övning med samma ekonomiska ramar men att Sjöfartsverket totalt kan spara 17 miljoner SEK per år genom att skära ned i lotsbåtsverksamheten. / This work has been carried out to investigate the potential of the Swedish Maritime Administration to use helicopters instead of pilot launches (boats) to assign pilots to ships. The aim has been to estimate this process from an economic perspective with use of the Payback method. The method has been utilized in an exploratory way. Financial data was requested from current operations in allocating the pilot to vessels and these were compared with the estimated costs of the Maritime Administration SAR helicopters operating over the same transport. No attention has been paid to the possible process improvements that this could lead to, simply what the cost of the same transport would be with the new mode of transport (helicopter). The result is illuminated from three horizons. How it is seen from the piloting side, how it is seen from the helicopter function's side and ultimately what it will mean for the Swedish Maritime Administration as a whole. The conclusion reached is that the piloting function will have higher costs for transport, helicopter operations may be less able to exercise within the same economic framework and that the Swedish Maritime Administration could potentially save 17 million SEK per annum by cutting back on pilot launch costs.

The deployment of unmanned aerial vehicles (UAV) in military applications increased the research about them and the importance of them. The unmanned helicopters are the most agile and maneuverable vehicles among the unmanned aerial vehicles (UAV). The ability of hovering and low speed cruise makes them even more attractive. Such abilities supply more areas to deploy the usage of the unmanned helicopters like search &amp / rescue, mapping, surveillance. Autonomy is the key property for these vehicles. In order to provide autonomy to an unmanned vehicle, the guidance and the autopilot units are designed in the first step. Waypoints are used to track the desired trajectories. The line of sight guidance is used to reach an active waypoint. In order to realize the guidance commands controllers are designed by using LQR. In addition, position and heading controllers are designed by root-locus method. The trimming and linearization are implemented in order to extract linear models used for controller design. Keywords: Helicopter, control, guidance

Master of Engineering (Research) / This thesis, by developing a Miniature Aerial Vehicle (MAV) hovering platform, presents a practical solution to allow researchers and students to implement their theoretical methods for guidance and navigation in the real world. The thesis is not concerned with the development of guidance and navigation algorithms, nor is it concerned with the development of external sensors. There have been some recent advances in guidance and navigation towards developing algorithms and simple sensors for MAVs. The task of developing a platform to test such advancements is the subject of this thesis. It is considered a difficult and time consuming process due to the complexities of autonomous flight control and the strict size, weight and computational requirements of this type of system. It would be highly beneficial to be able to buy a platform specifically designed for this task that already possesses autonomous hovering capability and the expansion connectivity for interfacing your own custom developed sensors and algorithms. Many biological and computer scientists would jump at the opportunity to maximize their research by real world implementation. The development of such a system is not a trivial task. It requires a great deal of understanding in a broad range of fields including; Aeronautical, Microelectronic, Mechanical, Computer and Embedded Software Engineering in order to create a successful prototype. The challenge of this thesis was to design a research platform to enable easy implementation of external sensors and guidance algorithms, in a real world environment for research and education. The system is designed so it could be used for a broad range of testing experiments. After extensive research in current MAV and avionics design it became obvious in several areas the best available products were not sufficient to meet the needs of the proposed platform. Therefore it was necessary to custom design and build; sensors, a data acquisition system and a servo controller. The latter two products are available for sale by Jimonics (www.jimonics.com). It was then necessary to develop a complete flight control system with integrated sensors, processor and wireless communications network which is called ‘The MicroBrain’. ‘The MicroBrain’ board measures only 45mm x 35mm x 11mm and weighs ~11 grams. The coaxial contra-rotating MAV platform design provides a high level of mechanical stability to help minimise the control system complexity. The platform was highly modified from a commercially available remotely controlled helicopter. The system incorporates a novel collision protection system that was designed to also double as a mounting place for external sensors around its perimeter. The platform equipped with ‘The MicroBrain’ is capable of fully autonomous hover. This provides a great base for testing guidance and navigational sensors and algorithms by decoupling the difficult task of platform design and low-level stability control. By developing a platform with these capabilities the researcher can now focus on the guidance and navigation task, as the difficulties in developing a custom platform have been taken care of. This therefore promotes a faster evolution of guidance and navigational control algorithms for MAVs.

Thesis (M.S. in Information Technology Management)--Naval Postgraduate School, June 2005. / Thesis Advisor(s): Joseph A. Sullivan, Rudolph Darken. Includes bibliographical references (p. 113-115). Also available online.

La conception aérodynamique des pales du rotor principal d’un hélicoptère doitsimultanément prendre en compte plusieurs objectifs relatifs aux critères du vol stationnaire etvol d’avancement. Cette thèse vise à développer une boucle d’optimisation automatiséecombinant des algorithmes d’optimisation avancés et des outils de simulation. Deux outils desimulation sont employés pour la prédiction des performances rotor : le code de mécanique devol HOST, ainsi que le code de Mécanique des Fluides Numérique (MFN) elsA. Une analyse deces outils est effectuée pour des cas test bien documentés afin d’estimer leur capacité à prédiredes tendances de performances rotor en fonction de la géométrie de pale. L’influence desparamètres numériques est également caractérisée. Aussi, une stratégie d’optimisation estdéveloppée, permettant la prise en compte de plusieurs objectifs et de contraintes complexes,ainsi que la détermination d’optima globaux pour ce problème multimodale. Suivant cescritères, un algorithme génétique (AG) est sélectionné. Afin de réduire le nombre d’évaluationsnécessaires, une stratégie d’optimisation multi-fidélité est proposée : une optimisationpréliminaire utilisant l’AG et HOST est utilisée pour la réduction de l’espace des paramètres ensélectionnant la zone de haute performance. Ensuite, une surface de réponse est construiteavec des calculs haute-fidélité des pales de haute performance comme vu par l’étapepréliminaire. L’optimisation est finalement effectuée sur cette surface de réponse haute-fidélité.L’approche proposée résulte en une augmentation significative des performances rotor, tout enrespectant le critère industriel relatif au nombre de calculs coûteux comme MFN. L’approcheproposée se révèle être un outil efficace pour la conception de pales du rotor principald’hélicoptère. / The aerodynamic design of helicopter rotor blades requires taking into accountedmultiple objectives simultaneously, to provide a compromise solution for the conflictingrequirements associated to hover and forward flight conditions. The present work aims atdeveloping an automated optimization based on the combination of advanced optimizationalgorithms and simulation tools. As a preliminary step, candidate simulation methods andoptimization algorithms are assessed in detail. Two simulation methods are employed for thecomputation of rotor performance: the in-house Helicopter Overall Simulation Tool (HOST),based on the blade element method, and ONERA’s Computation Fluid Dynamics (CFD) codeelsA. An in-detail analysis of both simulation tools for well documented test cases is carried out,with focus on their capability of predicting trends of the global rotor performance as a function ofblade geometry. The impact of computation settings is also characterized. Then, an optimizationstrategy is developed, allowing the incorporation of multiple objectives and complex constraints,and the detection of global optima for multi-modal problems. Based on these criteria, a geneticalgorithm (GA) is selected. To reduce the number of simulations required to find optimalsolutions, a Multi-Fidelity Optimization (MFO) strategy is proposed: a preliminary low-fidelity GAoptimization stage based on HOST simulations is used to reduce the design space by selectinga high-performance subspace. Then, a CFD-based surrogate model is constructed on thereduced design space by using a sample of high-performance blade from the low-fidelity step.The final optimization step is run on the high-fidelity surrogate. The proposed MFO approachresults in significant rotor performance improvements while using a far lower number of costlyCFD evaluations of the objective functions with respect to a full GA optimization. The proposedapproach is shown to represent an efficient design tool for industrial helicopter rotor blade

Lorsqu’un hélicoptère opère dans des conditions givrantes extrêmes, l’accumulation de glace sur les pales peut considérablement impacter les performances de l’appareil. De nombreuses recherches portant sur le développement d’un système de dégivrage à faible consommation et moindre coût ont été initiées ces dernières années. Dans cette thèse, une technique ondulatoire de protection contre la formation de glace sur les surfaces des pales d’hélicoptères est étudiée. La stratégie proposée repose sur l’utilisation d’ondes guidées d’ordre élevé spécifiques pour créer des cisaillements dépassant la force d’adhésion surfacique d’un profil de glace. Des essais ont d’abord été menés pour réaliser le modèle E.F. d’un tronçon de pale, puis une stratégie de réduction de modèle est développée pour la Méthode des Éléments Finis Ondulatoires. Cette formulation s’appuie sur la projection des vecteurs d’état sur une base réduite, constituée des formes d’ondes progressives. Elle permet de réaliser des analyses ondulatoires large-bande dans les structures complexes, 1D ou 2D périodiques. Les ondes guidées sont d’abord examinées dans la pale d’hélicoptère, puis les effets de localisation et de conversion des ondes sont interprétés dans divers guides d’ondes 1D et 2D. Les interactions de ces ondes d’ordre élevé avec les profils d’accrétion de glace, ainsi qu’avec plusieurs types de singularités structurelles, sont analysées au moyen d’une Méthode des Matrices de Diffusion. Une formulation ondulatoire temporelle est ensuite proposée pour l’analyse rapide de la propagation d’un train d’ondes dans les guides d’ondes couplés. Enfin, un réseau d’actionneurs est conçu pour la génération de trains d’ondes d’ordre élevé, et des validations temporelles sont réalisées dans une plaque composite ainsi que dans une pale de Super Puma. / When helicopters fly through extreme conditions, ice can aggregate on their blades and seriously affect the aircraft performances. Recently, an increasing research effort was devoted to the development of affordable low power de-icing solutions. In this thesis, a wave-based approach is adopted to prevent and/or remove ice aggregates from the surfaces of helicopter rotor blades. The de-icing strategy uses specific high-order guided waves to exceed the shear adhesion strength of ice accretion profiles. Experiments are conducted in order to update the FE model of a realistic rotor blade, then a Model Order Reduction strategy is developed for the Wave Finite Element Method. It involves a projection of the state vectors on a reduced basis of propagating waves shapes, and enables broadband wave analysis in structurally advanced 1D and 2D periodic structures. Guided wave propagation is studied within a helicopter rotor blade, and wave localization and conversion effects are discussed in various 1D and 2D composite waveguides. The interactions of high-order waves with ice aggregates and other types of structural singularities are also examined by means of a Diffusion Matrix Method. Then, time-domain propagation in coupled waveguides subjected to a wave pulse is analysed through a computationally efficient wave-based formulation. Finally, a smart actuator network is designed for the generation of high-order wave pulses and validations are conducted in a composite plate and a Super Puma rotor blade using time simulation.

L’industrie hélicoptériste est une industrie de haute technologie caractérisée essentiellement par la taille réduite de son marché, le faible nombre de concurrents, la fréquence des situations monopolistiques établies par les fournisseurs, une réglementation exigeante et des contraintes technologiques spécifiques de conception. Ses projets ont souvent connu ces dernières années des dérives temporelles et budgétaires. Le développement des nouvelles technologies d’informations, les avancées des connaissances aérodynamiques et les nouveaux matériaux la propulse actuellement à un carrefour industriel de son histoire. Cette thèse a pour objectif de soutenir les efforts de développement d’un des leaders mondiaux de l’industrie hélicoptériste, dans un contexte de compétition orientée vers l’innovation. Les retours d’expérience de projets ont mis en lumière des situations récurrentes contrariant leur aboutissement. Les solutions conséquentes proposées pour favoriser l’innovation sont basées sur la valorisation d’un état d’esprit plutôt que sur une optimisation structurelle ou la recherche de méthode de créativité. / The helicopter industry is a high tech industry characterised in essence by the small size of its market, the low number of competitors, the high frequency of monopolistic situations set up by suppliers, demanding regulations and specific technological design constraints. In the last few years, projects have been affected by time and budgetary limitations. The development of new information technologies, the advances in the knowledge of aerodynamics and new materials are, in fact, thrusting the industry towards an seminal point. The aim of this thesis is to support the developmental efforts of one of the world leaders in the helicopter industry, in a context of competition geared to innovation. Feedback from projects has highlighted recurring situations, which have frustrated (positive) outcomes. Therefore, recommended solutions to promote innovation are based on the value of the industry’s ethos or frame of mind rather than structural improvement or even creative research methods.

Les hélicoptères génèrent un flux d'air important en service, qui semble générer des envols de particules. Ces dernières finissent parfois leur course sur les pare-brise, créant des endommagements et susceptibles d'être liés à des fissurations macroscopiques desdits pare-brise. Une analyse de l'existant est tout d'abord menée, dans la littérature académique comme dans le contexte industriel de ces travaux. Une série d'endommagements est prélevée sur des pare-brise rebutés afin d'en analyser les motifs et les dimensions caractéristiques, et des pare-brise rompus sont analysés. Des facteurs d'influence liés au projectile, aux conditions d'impact et aux conditions environnementales sont isolés, et testés dans le cadre d'une campagne d'essais sur éprouvette. L'étude de l'influence des conditions environnementales indique que l'atmosphère du laboratoire est représentative des conditions moyennes pouvant se produire en service. Un projectile de type gravier standardisé est ensuite mis au point afin de gagner en reproductibilité des essais sans perdre de représentativité des résultats. Une série d'essais est alors menée sous des conditions d'impact variables (vitesse, incidence), et validée par des essais à plus grande échelle sur plaque de verre. Les altérations générées par le gravillonnage sont alors mesurées et quantifiées, de même que leur évolution avec la vitesse d'impact. Le lien entre ces altérations et la géométrie des endommagements est analysé, et confirmé par des modélisations analytiques et numériques. Une étude des activités complémentaires est finalement menée, dans l'optique de définir une spécification de la performance des futurs pare-brise au gravillonnage. / Helicopters can move by generating an airflow that seems powerful enough to make ground particles take off; some of them end up crashing on the windshields, creating damage called gravelling. These impacts may be linked to macroscopic windshield failure, i.e. cracks. A state-of-the-art analysis is performed, in both academic literature and corporate data. A batch of damaged spots is selected on used windshields in order to analyze characteristics dimensions and patterns featured by gravelling impacts, whereas cracked windshield fractographic analysis are performed. Influence factors, linked to the impact conditions as well as the projectile and the environment, are isolated and tested through a sample impact test campaign. After converging towards representative environmental conditions and projectile, the influence of the impact conditions are quantified on test sample, then validated with further windshield-scaled samples. The alterations created by gravelling impacts, as well as their evolution with impact velocity, can consequently be measured and quantified. The links between these alterations and the damage geometries are looked after and confirmed by analytical and numerical models. Finally, an analysis of further activities is proposed so as to be able to define gravelling performance specifications for future windshields.