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Controlling the position and attitude of a helicopter hovering in the presence of atmospheric turbulence is a difficult task which demands considerable pilot work-load which becomes even more difficult'when a load is suspended from the helicopter, because the oscillations of the load aggravate the situation. Tasks that require a suspended load to be kept fixed relative to a point in space, while the helicopter remains at hover, are extremely difficult to achieve. Several load-positioning systems exist but provide inadequate solutions to the problem. A brief account of such systems and their limitations is given before describing the automatic hovering control system proposed in this thesis. It causes appropriate motion of the helicopter to achieve the desired stationarity of the load. The techniques of modern control theory were employed to design this optimal controller. Digital simulation was used for testing the response of the resulting optimal system. The mathematical model of two connected rigid bodies moving in space (representing the helicopter and suspended load) is described in detail. Several combinations of cable length-load weight were chosen and in each case the response of the closed-loop system was investigated. It was found that considerable reduction of the oscillations of the load can be achieved when suitable cable arrangements are used. The use of winch control of lateral displacement of the load also improves the lateral response of the entire system. An augmented mathematical model was used which included both the dynamics of the control actuators and the models representing atmospheric turbulence and sensor noise. Since many of the state variables of the system cannot be physically measured, it is obvious that only limited information on the state of the system would be available for processing by such a controller. Therefore two solutions to the problem were considered: (i) the use of a state estimator to provide to the controller the lost feedback information; , and (ii) the use of an output regulator which takes into account the fact that limited feedback information is available. The responses of the closed-loop systems using each of these solutions were investigated and compared. The numerical problems encountered in this design are analysed and some means .of overcoming them are suggested. Finally, the best combination of cable arrangement and controller is described with reference to several important factors such as system simplicity and performance.

A methodology has been developed for predicting aircraft safety and reliability incorporating both C.C.F.s(Common-Cause Failures), and phased missions. Failure behaviour of an aircraft, or its systems due to both independent failures and C.C.F.s are modelled by the Markov process, and simulated using Monte Carlo method with the robust variance reduction techniques. Prediction of safety and reliability is made through discrete-event simulation of aircraft operations. Validation was made by comparing the predicted safety and reliability results of B767 ETOPS aircraft propulsion system, using the developed methodology, to those obtained from the analysis of real operation data. The credibility and the accuracy of the developed methodology are shown through the comparison of results. A case study was conducted for investigating the safety and reliability of the propulsion system of two-, three- and four-engined aircraft using the developed methodology. The case study produced valuable results concerning the safety of ETOPS flight, which were not previously known. These results were able to be used for further trade studies of aircraft design to decide the number of engines, and also for establishing new regulations for ETOPS flights.

Airlines are not able to conduct their businesses in the same way as other global transnational industries. They are inhibited by the foreign ownership restrictions in Air Services Agreements and national laws. Since the United Kingdom and the United States signed the first Bermuda agreement in 1946, the nationality clauses contained in virtually all bilaterals have limited the companies designated to provide services to those airlines owned and managed by nationals of the respective countries. A key reason why foreign ownership rules remain in place is that they protect national airlines. In doing so, they also limit the strategies available to governments whose carriers are in difficulties. The 57 years old bilateral system restricts the development of international air services, adversely affecting airlines and their users- travellers and the tourism and air freight industries. As time goes on, the rapidly changing air transport environment of privatisation, liberalisation and globalisation is forcing airlines to seek structural adjustments in order to survive in the new millennium. Airlines are asking to have more freedom for their strategies, in order to enhance their profitability. Pressures have been growing to ease the ownership rules contained in bilateral agreements to allow airlines greater commercial freedom. As there is no comprehensive research on the topic, this study aims to provide a detailed analysis of the impact of airline ownership rules. It will provide a point of reference for organisations like ICAO and nations to review the ownership issue in the future. This research starts with a review of the historical background, the current limitations in different countries and the pros and cons of ownership rules. It analyses how aviation markets have been influenced to date around the world and how governments and carriers have responded to these influences. It goes on to identify the main benefits and risks of foreign investment, and the motives for foreign investment in the EU and Asia- Pacific. It assesses the prospects for change in ownership rules under multilateral and plurilateral proposals, and develops a strategy for changing the current ownership rules. It concludes by predicting how airlines will react to such changes and makes suggestions for European Airlines in the Asia-Pacific region.

Approved for public release, distribution is unlimited / The purpose of this research was to examine the effects of frequency, and polarization on radio wave propagation in urbanized areas for unmanned aerial vehicle (UAV) data links, and command and control. The transmission from a UAV operating over a small city was simulated using the Urbana Wireless Toolset. Parameters that were varied include frequency, antenna polarization, UAV altitude, and building materials. Multiple reflections and diffractions were included in the simulation. In each case signal contours were generated at discrete frequencies over a 50 MHz bandwidth. It was observed that the signal levels varied up to over the bands at a fixed observation point due to frequency-dependent reflection and diffraction. / 1st Lieutenant, Turkish Air Force

Approved for public release; distribution is unlimited. / The Marine Corps has recently embarked on the development of a Vertical Takeoff and Landing Unmanned Aerial Vehicle (VTUAV) to replace the aging Pioneer system. This thesis examines the critical elements this platform must possess in order to effectively support small units operating in urban environments. We address this issue by creating and exploring an agentbased simulation of a platoon conducting an urban patrol in a setting similar to those currently being encountered in Iraq. The platoon utilizes the VTUAV as an intelligence-gathering asset. We use an efficient designed experiment to generate data from the simulation scenario, and then use multiple regression and regression trees to relate the UAV capabilities to the patrol's operational effectiveness. Our results suggest that the effectiveness of a VTUAV is greatly influenced by noise in the urban warfare environment. We use a loss function, along with the regression models, to identify UAV configurations that improve operational effectiveness yet are robust to uncertainties about civilian and insurgent behavior. The VTUAV must have high communication capability, as well as accurate sensing, in order to perform well across a range of environmental conditions. / Captain, United States Marine Corps

Underwater acoustic networks provide an interface between UUVs and surface or land-based control systems. By exploiting range data measured incidental to communications on these networks it is possible to perform underwater positioning similar to that of the satellite-based GPS program. In this thesis, several algorithms for generating position fixes from these range data are implemented, tested, and evaluated with synthetic data. The algorithms are then applied to data obtained during operations at sea. / US Nany (USN) author.

In 1994 the U.S. Navy resurrected a base in Everett, Washington and commissioned it as Naval Station Everett (NS Everett), the new homeport for six Naval vessels. Prior to 1994 the base had seen primary use as the homeport for a number of vessels during World War II. In the early 1940s Piers Delta and Echo were constructed to berth aircraft carriers and other warships. Piers Delta and Echo are 560 feet and 578 feet, respectively, and 46 feet wide. They are constructed out of pier decking and pile caps on timber piles. Naval vessels currently assigned to NS Everett berth at new piers on the base, while Piers Delta and Echo berth the small craft that support the larger vessels. The small craft mission includes tugboat services, base security and environmental response functions, and vessel boarding and search training for local units. / Contract number: N62271-97-G-0075 / US Navy (USN) author.