Thesis (M.S.)--Ohio University, August, 2004. / Title from PDF t.p. Includes bibliographical references (p. 84-87)

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Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 1979. / MICROFICHE COPY AVAILABLE IN ARCHIVES AND AERONAUTICS. / Includes bibliographical references. / by Christopher Graham McMuldroch. / M.S.

Airdrop systems provide a unique capability of delivering large payloads to undeveloped and inaccessible locations. Traditionally, these systems have been unguided, requiring large landing zones and drops from low altitude. The invention of the steerable, gliding, ram-air parafoil enabled the possibility of precision aerial payload delivery. In practice, the gliding ability of the ram-air parafoil can actually create major problems for airdrop systems by making them more susceptible to winds and allowing them to achieve far greater miss distances than were previously possible. Research and development work on guided airdrop systems has focused primarily on evolutionary improvements to the guidance algorithm, while the navigation and control algorithms have changed little since the initial autnomous systems were developed. Furthermore, the control mechanisms have not changed since the invention of the ram-air canopy in the 1960's. The primary contributions of this dissertation are: 1) the development of a reliable and robust method to identify a flight dynamic model for a parafoil and payload aircraft using minimal sensor data; 2) the first demonstration in flight test of the ability to achieve large changes in glide slope over ground using coupled incidence angle variation and trailing edge brake deflection; 3) the first development of a control law to implement glide slope control on an autonomous system; 4) the first flight tests of autonomous landing with a glide slope control mechanism demonstrating an improvement in landing accuracy by a factor of 2 or more in especially windy conditions, and 5) the first demonstrations in both simulation and flight test of the ability to perform in-flight system identification to adapt the internal control mappings to flight data and provide dramatic improvements in landing accuracy when there is a significant discrepancy between the assumed and actual flight characteristics.

Michael S. Triantafyllou, Marc Bodson, Michael Athans. / Caption title. / Bibliography: p. 19-20. / Ames Research Center Grant NGL-22-009-124

In the event of an onboard emergency, air transport pilots are remarkably adept at safely landing their aircraft. However, the tasks of selecting an alternate landing site and developing a safe path to land are very difficult in the high workload, high stress environment of a cockpit during an emergency. The purpose of this research was to develop an automated path planning aid which would assist the pilot in the completion of these tasks. A prototype was developed to test this concept experimentally. The experiment was also intended to gather further information about how pilots think about and accomplish this task as well as the best ways to assist them. In order to better understand the priorities and processes pilots use when dealing with emergency planning, a survey of airline pilots was conducted. The results of this survey highlighted the fact that each emergency is unique and has its own set of factors which are critically important. One factor which is important in many emergencies is the need to land quickly. The survey responses indicated that one of the most important characteristics of a useful tool is that it should provide pertinent information in an easy to use manner, and should not divert too much attention from their other tasks. A number of design goals drove the development of the prototype aid. First, the aid was to work within current aircraft, without requiring substantial redesign on the cockpit. Second, the aid was to help improve pilots' performance without increasing their workload. Finally, the aid was designed to assist pilots in obtaining and processing critical information which influences the site selection and path development tasks. One variation of the aid included a filter dial which allowed pilots to quickly reduce the number of options considered, another variation of the aid did not include such a dial. These two variations of the aid were tested in order to assess the impact of the addition of the filter dial to the system. Though many of the results did not prove to be statistically significant, they suggest that the addition of a filter dial improved the quality of the selected landing site; however, it also increased the time required for the selection. The results were obtained in both familiar and unfamiliar emergencies. The dial was shown to improve the time to complete the task in the case of unfamiliar emergencies. The experiment also compared an optimal ranking system to a non-optimal system, for which results showed no significant difference between the two. This may imply that while pilots did not tend to over rely on the ranking system, under-reliance may need to be addressed by training and a better understanding of the factors which impact the rankings. The participants found that the aid facilitates quick and easy access to critical information. The aid was also useful for processing this information by filtering out options which were inappropriate for a given scenario through the use of the filter dial. The participants also made recommendations about possible improvements which could be made to the system such as better filter settings which are more similar to the way that pilots think about their options.

This thesis addresses the challenges in the efficient and robust generation and optimization of three-dimensional landing trajectories for fixed-wing aircraft subject to prescribed boundary conditions and constraints on maneuverability and collision avoidance. In particular, this thesis focuses on the airliner emergency landing scenario and the minimization of landing time. The main contribution of the thesis is two-fold. First, it provides a hierarchical scheme for integrating the complementary strength of a variety of methods in path planning and trajectory optimization for the improvement in efficiency and robustness of the overall landing trajectory optimization algorithm. The second contribution is the development of new techniques and results in mesh refinement for numerical optimal control, optimal path tracking, and smooth path generation, which are all integrated in a hierarchical scheme and applied to the landing trajectory optimization problem. A density function based grid generation method is developed for the mesh refinement process during numerical optimal control. A numerical algorithm is developed based on this technique for solving general optimal control problems, and is used for optimizing aircraft landing trajectories. A path smoothing technique is proposed for recovering feasibility of the path and improving the tracking performance by modifying the path geometry. The optimal aircraft path tracking problem is studied and analytical results are presented for both the minimum-time, and minimum-energy tracking with fixed time of arrival. The path smoothing and optimal path tracking methods work together with the geometric path planner to provide a set of feasible initial guess to the numerical optimal control algorithm. The trajectory optimization algorithm in this thesis was tested by simulation experiments using flight data from two previous airliner accidents under emergency landing scenarios.The real-time application of the landing trajectory optimization algorithm as part of the aircraft on-board automation avionics system has the potential to provide effective guidelines to the pilots for improving the fuel consumption during normal landing process, and help enhancing flight safety under emergency landing scenarios. The proposed algorithms can also help design optimal take-off and landing trajectories and procedures for airports.