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No description available.

No description available.

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.

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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.

The MMT Observatory, a joint venture of the Smithsonian Institution and the University of Arizona, operates the 6.5-m MMT telescope on the summit of Mount Hopkins approximately 45 miles south of Tucson, AZ. The upgraded telescope has been in routine operation for nearly fifteen years and, as such, is a very reliable and productive general purpose astronomical instrument. The telescope can be configured with one of three secondary mirrors that feed more than ten instruments at the Cassegrain focus. In this paper we provide an overview of the telescope, its current capabilities, and its performance. We will review the existing suite of instruments and their different modes of operation. We will describe some of the general operations challenges and strategies for the Observatory. Finally, we will discuss plans for the near-term future including technical upgrades, new instrumentation and routine queue operation of MMIRS and Binospec.

Approved for public release; distribution is unlimited / The thesis addresses the problem of optimally re-assigning strike aircraft to targets in response to the emergence of "pop-ups" or time-sensitive targets. The first part of thesis develops an automated decision aid to rapidly revise the current air tasking order (ATO), so as to: maximize achievement of target destruction goals (weighted by target priorities), minimize attrition risk to employed assets, and disrupt the current ATO as little as possible. The second part of the thesis develops a detailed test and evaluation plan to conduct a comparison of two competing automated decision aids and the current manual reassignment methods. Critical operational issues, measures of effectiveness and measures of performance were developed to fully evaluate operational performance. The time-sensitive-targeting decision aid was tested and validated during major air strike live exercises at Marine Aviation Weapons and Tactics Squadron One. Careful measurements comparing the re-taskings recommended by the decision aid against actual decisions demonstrated that in every case the model's solutions were of better or equal quality, maximized combat asset utilization, and were achieved significantly faster. / Major, United States Marine Corps

Many military Intelligence Surveillance and Reconnaissance (ISR) operations would benefit greatly from a fleet of disparate sensor-bearing UAVs that are tightly integrated via a communications network, work cooperatively for a common operational objective, enhance situation awareness of the areas of operation, and increase persistence of sensor dwell time on strategic targets. This would enable continuity in the entire target acquisition cycle, from detection to classification to identification and finally localization of targets, in a diverse and dynamic environment. The integration of sensors and development of tactics in a cooperative sensing environment is one of the current focuses among the military intelligence community, and hence motivates this thesis effort. By building models with an existing agent-based simulation platform and using an extremely efficient experimental design methodology, numerous factors which could potentially affect the effectiveness of a cooperative sensing network against two arrays of targets are explored. The factors considered include UAV airspeed, reliability, detection/classification coverage and probability, network latency and degradation, UAV configurations and responsiveness, as well as air space separation. The two arrays of targets are mobile armor concentrations and time critical targets / these vary in their deployment profiles, vulnerability constraints and ease of detectability. Factors characterizing these targets, such as the shoot-and-scoot behavior of time critical targets, are also investigated. The study provides operational insights pertaining to the design and effective use of cooperative sensing for ISR purposes. These include the importance of having good UAV sensor capabilities, the need for a suite of sensors to aid in locating well-camouflaged time-critical targets, and the need for "intelligent" application of UAV cooperation tactics based on the characteristics of recently-classified targets.