Thesis (M.S. in Defense Analysis)--Naval Postgraduate School, December 2008. / Thesis Advisor(s): O'Connell, Robert. "December 2008." Description based on title screen as viewed on February 2, 2009. Includes bibliographical references (p. 43-45). Also available in print.

Thesis (M.S. in Program Management)--Naval Postgraduate School, December 2002. / Thesis advisor(s): Michael W. Boudreau, Richard G. Rhoades. Includes bibliographical references (p. 63-65). Also available online.

Thesis (M. S.)--Aerospace Engineering, Georgia Institute of Technology, 2009. / Committee Chair: Smith, Marilyn; Committee Member: Bauchau, Olivier; Committee Member: Costello, Mark; Committee Member: Moulton, Marvin; Committee Member: Ruffin, Stephen.

Thesis (M.A.)--Carleton University, 2001. / Includes bibliographical references (p. 68-69). Also available in electronic format on the Internet.

Thesis (Ph. D.)--Aerospace Engineering, Georgia Institute of Technology, 2007. / Samual V. Shelton, Committee Member ; P.K. Yeung, Committee Member ; Lakshmi N. Sankar, Committee Chair ; Stephen Ruffin, Committee Member ; Marilyn Smith, Committee Member.

Thesis (Ph.D.) - University of Queensland, 2006. / Includes bibliography.

Στην παρούσα διπλωματική παρουσιάζεται το μαθηματικό μοντέλο ενός ελικοπτέρου με την ελάχιστη δυνατή πολυπλοκότητα για σκοπούς εξομοίωσης και αναλύονται τα συστήματα ελέγχου και αύξησης ευστάθειας. Οι λόγοι για την χρήση ενός απλοποιημένου μοντέλου είναι το κόστος, η ευελιξία, η εύκολη προσαρμογή σε διαφορετικούς τύπους ελικοπτέρου, καθώς και η καλύτερη κατανόηση των χαρακτηριστικών ελέγχου από την πλευρά του μηχανικού αλλά και από την πλευρά του πιλότου εξομοίωσης. Η προσέγγιση ξεκινά με μια γενική περιγραφή των χαρακτηριστικών ενός ελικοπτέρου και του τρόπου χειρισμού του. Συνεχίζεται με τον καθορισμό των τμημάτων του ελικοπτέρου και ακολουθεί η επεξήγηση των εξισώσεων. Παρουσιάζεται η γενική μέθοδος εφαρμογής του μοντέλου σε διάφορους τύπους ελικοπτέρων με αλλαγή των βασικών δεδομένων. Αναφέρονται πιθανές επεκτάσεις και βελτιώσεις καθώς και συστήματα αυτομάτου ελέγχου που συναντώνται στα πραγματικά ελικόπτερα και μπορούν να ενσωματωθούν στο μοντέλο. Για την καλύτερη κατανόηση των συστημάτων ελέγχου, παρουσιάζονται αναλυτικά, τα συστήματα αύξησης ευστάθειας και αυτόματου ελέγχου πτήσης του ελικοπτέρου UH-60 στους τρεις άξονες κίνησης. / Mathematical model for development of helicopter simulation program. Automatic control systems of helicopter Black Hawk.

In recent years, forestry programmes in British Columbia have increasingly used helicopters to expedite operations, particularly in the areas of fire suppression and prescribed burning. Between 1970 and 1977 the population of Canadian helicopters doubled, reflecting the increased usage resulting from new, more efficient designs. The number of accidents per year decreased in the 8 years, but the percentage of fatal accidents increased In British Columbia, the accident rate per 10,000 hours in the years 1975 and 1976, was 3.6, the third highest in Canada. After an extensive period of field work in this province, by the author, it is clear that the people working in and around helicopters do not generally receive enough training in the safety precautions necessary. This lack of training was evident at both the worker level and the supervisory level. In fire suppression operations, the inadequate training is aggravated by haste, which greatly increases the chances of unnecessary accidents. This report identifies areas of training that need greater-attention, and it offers some guidelines for future training programmes. The report discusses the fundamentals of helicopter flight, in order that the layman may gain some appreciation of what problems the pilot has to tolerate. Several types of operations are then detailed with safety prescriptions for each one. Some causative factors in each operation are also discussed. The report then analyses the use of helicopters in aerial ignition systems. Of the several systems currently in use, it is clear that the helicopter drip torch is potentially the most hazardous, but to date there have been no serious helicopter drip torch accidents. Finally the report looks at crew deployment techniques, in particular, helicopter rappelling and helitack. The level of training and hazard awareness in these two operations is higher than was generally seen elsewhere, and provides a good example of how helicopters can be used safely and efficiently. Throughout the report, reference is made to past accidents. These accidents show a fundamental lack of safe practice; a situation that would be improved with better training programmes. They also illustrate some of the diverse and disastrous results of poor training. The report recommends that the Workers' Compensation Board of British Columbia should seriously consider setting up a series of training films, which, along with posters and leaflets, could be distributed to the various companies and organisations who use helicopters in the course of their operations. Transport Canada is now preparing a series of general training aids, and these will be made available to interested parties. / Forestry, Faculty of / Graduate

M.Ing. (Electrical and Electronic Engineering) / This treatise presents an investigation into the application of multivariable frequency domain techniques in the modelling and control of a helicopter aircraft in forward flight. The presentation is structured in the following sectioned format: I Hypotheses are stated which deal with the use of linear, multivariable, frequency domain theory in the modelling and control of helicopter aircraft. II The stated hypotheses are investigated by the application of relevant theories and techniques to a reference case plant - a single rotor helicopter in forward flight. III Conclusions drawn from the results are used to assess the validity of the hypotheses. The subject matter of the presentation may be summarized as follows: The hypotheses are initially placed in perspective by a discussion of the incentives for their formulation. In essence, the hypotheses state that helicopter dynamics, in a multivariable systems characterization, can be modelled and an appropriate flight control system designed by the use of linear frequency domain theory. The plant in reference to which the hypotheses are investigated is a single rotor utility helicopter - the Aerospatiale Alouette III. A single flight condition - a typical cruising condition - is considered. A comprehensive, nonlinear digital computer simulation of the aircraft is used as a substitute for the actual plant in the execution of the modelling and control design processes. The plant is modelled in terms of a linear model structure, in the form of the frequency response function, by linearization of its highly nonlinear dynamics about an operating point (datum flight condition). The frequency response function model parameters are identified by power spectral density analysis procedures. This method, based on random signal excitation of the plant, provides a valuable quantitative measure of the accuracy of the linearization performed in the identification. The measure, the coherence function, is used as a criterion for the robustness required of a control system of which the design is based on a linear model of a nonlinear plant.

The results of this research indicate that continuous, variable rotor speed control is a viable solution to increased helicopter maneuverability and agility. Of the rotor speed control laws investigated, the RCDR and T (RC) types seem the most promising. In particular, these control laws demonstrated a 31% improvement in time-to-turn 180 degrees, a 38% improvement in turn penetration distance, a 42% improvement in turn cross track distance, and a pointing margin advantage of nearly 94 degrees. In addition, the rotor speed control law parameters could be optimized such that the helicopter exited a maximum performance decelerating turn at or above its power bucket speed, affording the helicopter a distinct maneuvering advantage. It was also shown that different rotor speed control laws would most likely be required for the air combat and ground attack mission scenarios. The author feels that successful variable rotor speed control can be achieved through an appropriate marriage of FADEC engine control and high performance flight control systems. But numerous questions remain relative to the successful integration of this technology to existing and/or future helicopter designs, (addressed in the Recommendations for Future Research section). Nevertheless, this technology shows considerable promise and it is hoped that this study will be a stepping stone to future investigations in this area. / Master of Engineering