Stability and Control Issues Associated with Lightly

Total Page:16

File Type:pdf, Size:1020Kb

Stability and Control Issues Associated with Lightly STABILITY AND CONTROL ISSUES ASSOCIATED WITH LIGHTLY LOADED ROTORS AUTOROTATING IN HIGH ADVANCE RATIO FLIGHT A Dissertation Presented to The Academic Faculty by James Michael Rigsby In Partial Fulfillment Of the Requirements for the Degree Doctor of Philosophy in the School of Aerospace Engineering Georgia Institute of Technology December 2008 STABILITY AND CONTROL ISSUES ASSOCIATED WITH LIGHTLY LOADED ROTORS AUTOROTATING IN HIGH ADVANCE RATIO FLIGHT Approved by: Professor J.V.R. Prasad, Advisor Professor Dewey H. Hodges School of Aerospace School of Aerospace Engineering Engineering Georgia Institute of Technology Georgia Institute of Technology Professor Daniel P. Schrage Professor L.N. Sankar School of Aerospace School of Aerospace Engineering Engineering Georgia Institute of Technology Georgia Institute of Technology Professor David A. Peters Date Approved: October 14, 2008 Department of Mechanical, Aerospace and Structural Engineering Washington University, St. Louis ACKNOWLEDGEMENTS I would like to acknowledge my sincerest appreciation to Professor J.V.R. Prasad for his mentorship, incredible patience, and guidance during my time at the Georgia Institute of Technology. I would also like to thank Professor Daniel Schrage and Professor Lakshmi Sankar as well. It was within this circle of influence that I developed my appreciation for rotorcraft engineering, undoubtedly one of the most interesting, challenging, and multidisciplinary fields in all of aerospace engineering. In addition, I thank Professor Dewey Hodges and Professor David Peters for their guidance and participation in the review and evaluation of this work. I also thank the students who were finishing as I was just beginning: Chen Chang, Geoffrey Jeram, Suraj Unnikrishnan, Illkay Yavrucuk, and many others. Special thanks to Manuj Dhingra, whose friendship, assistance, and patience opened my eyes to the wider world of computing and who was always there to resolve my major computing crises with a few magical lines of code. I thank all of my friends at Georgia Tech for their help and support. Those friends include, but are not limited to: Mandy Goltsch, B.Y. Min, Alex Moodie, Kyle Collins, Troy Schank, and Jongki Moon, Ersel Olcer, and Suresh Kannon. Also, I offer a special thanks to Dr. Hong Xin, for friendship and fantastic software support. Finally, I thank my family, without whose love and support, none of this would have been possible. My wife Xiaohong, my parents, my sister and brother-in-law, all encouraged me and provided steadfast support. I dedicate this work to them. iii TABLE OF CONTENTS ACKNOWLEDGEMENTS ............................................................................................. iii LIST OF TABLES ..........................................................................................................vi LIST OF FIGURES........................................................................................................vii LIST OF SYMBOLS AND ABBREVIATIONS .............................................................. xii SUMMARY....................................................................................................................xv CHAPTER 1: INTRODUCTION...................................................................................... 1 1.1 Overview .............................................................................................................. 1 1.2 Literature Review.................................................................................................. 2 1.2.1 The Fairey Rotodyne.................................................................................... 3 1.2.2 The McDonnell Aircraft XV-1 Convertiplane ................................................. 5 1.2.3 High Advance Ratio Wind-Tunnel Experiments ............................................ 6 1.2.4 Analytical Investigations ............................................................................... 9 1.2.5 Autogyros....................................................................................................11 1.2.6 Compound Helicopters................................................................................12 1.2.7 Additional Works .........................................................................................14 1.3 Present Work.......................................................................................................14 1.4 Organization of Dissertation.................................................................................18 CHAPTER 2: MODELING AND SIMULATION ENVIRONMENT ..................................21 2.1 Rotor Model Formulation .....................................................................................21 2.2 Rotor Speed Degree of Freedom Model ..............................................................29 2.3 Airframe Model ....................................................................................................31 2.4 Operational Envelope and Test Conditions..........................................................32 2.5 Analysis Selection and Methodology Overview....................................................33 iv CHAPTER 3: ISOLATED ROTOR ANALYSIS .............................................................37 3.1 Autorotating Rotor Trim and Performance Trends................................................37 3.2 Rotor Stability ......................................................................................................50 3.3 Steady-State Control Hub Moments and Cross-Coupling ....................................60 3.4 Rotor Steady-State Gust Sensitivity.....................................................................75 3.5 Rotor Transient Response and Slowed-Rotor Dynamics .....................................78 3.6 Rotor Speed Response to Swashplate Controls ..................................................87 3.7 Cruise Condition Rotor Performance and Multiple Trim Solutions........................91 3.8 Source of Rotor Speed Non-linear Response to Control Inputs ...........................96 3.9 Preferred Rotor Operating Point Selection Criteria.............................................103 3.10 Effect of Blade Twist at the Cruise Condition ...................................................107 3.11 Rotor Performance Out of Moment Trim ..........................................................110 3.12 Chapter Summary............................................................................................112 CHAPTER 4: COUPLED ROTOR-AIRFRAME ANALYSIS ........................................114 4.1 Rotor Control in Quasi-Steady Maneuvers.........................................................115 4.1.1 Commanded Rotor Speed Transition Maneuver........................................115 4.1.2 Flight Path Transition Maneuver................................................................123 4.3 Coupled Rotor and Airframe Flight Dynamics Characteristics............................125 4.4 Rotor Speed and Longitudinal Mode Coupling...................................................133 4.5 Chapter Summary..............................................................................................135 CHAPTER 5: CONCLUSIONS AND RECOMMENDATIONS .....................................136 5.1 Conclusions.......................................................................................................136 5.2 Recommendations for Future Work ...................................................................142 APPENDIX..................................................................................................................145 REFERENCES............................................................................................................146 v LIST OF TABLES Page Table 1: Fixed Baseline Rotor Parameters ....................................................................26 Table 2: Rotor Mass Properties for Parametric Analysis................................................26 Table 3: Parametric Baseline Rotor Properties ..............................................................29 Table 4: Airframe Model Properties ...............................................................................31 Table 5: Eigenvalues from 13-State Linear Model – Longitudinal Modes.....................126 Table 6: System ID and Linear Analysis Results – Coupled Pitch Motion ....................129 Table 7: Eigenvalues from 13-State Linear Model – Lateral / Directional Modes .........131 Table 8: System ID and Linear Analysis Results – Coupled Roll Motion......................132 vi LIST OF FIGURES Page Figure 1: The Fairey Rotodyne, from ref [4] ................................................................... 4 Figure 2: The McDonnell Aircraft XV-1 Convertiplane, from reference [5]....................... 5 Figure 3: Center Spring Approximation Rotor Model from Ref. [52] ...............................24 Figure 4: Articulated Rotor Model Hinge Sequence from Ref. [54].................................25 Figure 5: Fan Plots for Parametric Rotor Models ...........................................................28 Figure 6: Flap Frequencies at Reduced Rotor Speed....................................................28 Figure 7: Rotor Drivetrain Response at Sea Level Hover...............................................30 Figure 8: Test Conditions Envelope...............................................................................32 Figure 9: Baseline Rotor Thrust Coefficient vs. Advance Ratio......................................38
Recommended publications
  • Jay Carter, Founder &
    CARTER AVIATION TECHNOLOGIES An Aerospace Research & Development Company Jay Carter, Founder & CEO CAFE Electric Aircraft Symposium www.CarterCopters.com July 23rd, 2017 Wichita©2015 CARTER AVIATIONFalls, TECHNOLOGIES,Texas LLC SR/C is a trademark of Carter Aviation Technologies, LLC1 A History of Innovation Built first gyros while still in college with father’s guidance Led to job with Bell Research & Development Steam car built by Jay and his father First car to meet original 1977 emission standards Could make a cold startup & then drive away in less than 30 seconds Founded Carter Wind Energy in 1976 Installed wind turbines from Hawaii to United Kingdom to 300 miles north of the Arctic Circle One of only two U.S. manufacturers to survive the mid ‘80s industry decline ©2015 CARTER AVIATION TECHNOLOGIES, LLC 2 SR/C™ Technology Progression 2013-2014 DARPA TERN Won contract over 5 majors 2009 License Agreement with AAI, Multiple Military Concepts 2011 2017 2nd Gen First Flight Find a Manufacturing Later Demonstrated Partner and Begin 2005 L/D of 12+ Commercial Development 1998 1 st Gen 1st Gen L/D of 7.0 First flight 1994 - 1997 Analysis & Component Testing 22 years, 22 patents + 5 pending 1994 Company 11 key technical challenges overcome founded Proven technology with real flight test ©2015 CARTER AVIATION TECHNOLOGIES, LLC 3 SR/C™ Technology Progression Quiet Jump Takeoff & Flyover at 600 ft agl Video also available on YouTube: https://www.youtube.com/watch?v=_VxOC7xtfRM ©2015 CARTER AVIATION TECHNOLOGIES, LLC 4 SR/C vs. Fixed Wing • SR/C rotor very low drag by being slowed Profile HP vs.
    [Show full text]
  • Effectiveness of the Compound Helicopter Configuration in Rotorcraft Performance Increase
    transactions on aerospace research 4(261) 2020, pp.81-106 DOI: 10.2478/tar-2020-0023 eISSN 2545-2835 effectiveness of the compound helicopter configuration in rotorcraft performance increase Jarosław stanisławski Retired doctor of technical sciences [email protected] • ORCID: 0000-0003-1629-4632 abstract The article presents the results of calculations applied to compare flight envelopes of varying helicopter configurations. Performance of conventional helicopter with the main and tail rotors, in the case of compound helicopter, can be improved by applying wings and pusher propellers which generate an additional lift and horizontal thrust. The simplified model of a helicopter structure, consisting of a stiff fuselage and the main rotor treated as a stiff disk, is applied for evaluation of the rotorcraft performance and the required range of control system deflections. The more detailed model of deformable main rotor blades, applying the Galerkin method, is used to calculate rotor loads and blade deformations in defined flight states. The calculations of simulated flight states are performed considering data of a hypothetical medium class helicopter with the take-off mass of 6,000kg. In the case of both of the helicopter configurations, the articulated main rotor hub is taken under consideration. According to the Galerkin method, the elastic blade model allows to compute blade deformations as a combination of the blade bending and torsional eigen modes. Introduction of additional wing and pusher propellers allows to increase the range of operational speed over 300 km/h. Results of the simulation are presented as time- runs of rotor loads and blade deformations and in a form of disk distribution plots of rotor parameters.
    [Show full text]
  • NASA Mars Helicopter Team Striving for a “Kitty Hawk” Moment
    NASA Mars Helicopter Team Striving for a “Kitty Hawk” Moment NASA’s next Mars exploration ground vehicle, Mars 2020 Rover, will carry along what could become the first aircraft to fly on another planet. By Richard Whittle he world altitude record for a helicopter was set on June 12, 1972, when Aérospatiale chief test pilot Jean Boulet coaxed T his company’s first SA 315 Lama to a hair-raising 12,442 m (40,820 ft) above sea level at Aérodrome d’Istres, northwest of Marseille, France. Roughly a year from now, NASA hopes to fly an electric helicopter at altitudes equivalent to two and a half times Boulet’s enduring record. But NASA’s small, unmanned machine actually will fly only about five meters above the surface where it is to take off and land — the planet Mars. Members of NASA’s Mars Helicopter team prepare the flight model (the actual vehicle going to Mars) for a test in the JPL The NASA Mars Helicopter is to make a seven-month trip to its Space Simulator on Jan. 18, 2019. (NASA photo) destination folded up and attached to the underbelly of the Mars 2020 Rover, “Perseverance,” a 10-foot-long (3 m), 9-foot-wide (2.7 The atmosphere of Mars — 95% carbon dioxide — is about one m), 7-foot-tall (2.13 m), 2,260-lb (1,025-kg) ground exploration percent as dense as the atmosphere of Earth. That makes flying at vehicle. The Rover is scheduled for launch from Cape Canaveral five meters on Mars “equal to about 100,000 feet [30,480 m] above this July on a United Launch Alliance Atlas V rocket and targeted sea level here on Earth,” noted Balaram.
    [Show full text]
  • 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27
    A B C D E F 1 A012 A03009 125 DOMINIE 1.72 AIRCRAFT 2 A009 A05871 1804 STEAM LOCO 1.32 STEAM ENGINE 3 A013 A02447 1905 ROLLS ROYCE 1.32 CAR 4 A002 A02444 1911 ROLLS ROYCE 1.32 CAR 5 A002 A02443 1912 MODEL T FORD 1.32 CAR 6 A002 A02450 1926 MORRIS COWLEY 1.32 CAR 7 A002 A02446 1930 BENTLEY 1.32 CAR 8 ROB A20440 1930 BENTLEY 1.12 CAR 9 A028 A08440 1932 CHRYSLER IMPERIAL 1.25 CAR 10 A002 A02441 1933 ALFA ROMEO 1.32 CAR 11 A002 A01305 25PDR FIELD GUN & MORRIS QUAD 1.76 VEHICLE 12 ROB A02552 2ND DRAGOON 1815 54MM FIGURE 13 ROB 50 YEARS OF THE GREATEST PLASTIC KITS BOOK 14 A013 A02303 88MM GUN & TRACTOR 1.76 VEHICLE 15 ROB A02303 88MM GUN & TRACTOR (D-DAY) 1.76 VEHICLE 16 A026 A06012 A-10 THUNDERBOLT II 1.72 AIRCRAFT 17 ROB ITALERI 097 A-10 WARTHOG 1.72 AIRCRAFT 18 A026 REVELL 04206 A300-600 ST BELUGA 1144 AIRCRAFT 19 A008 A01028 A6M2 ZERO (VJ DAY) 1.72 AIRCRAFT 20 ROB A50127 A6M2B -21 (2011) 1.72 AIRCRAFT PAINTS IN BOX 21 ROB A01005 A6M2B ZERO 1.72 AIRCRAFT 22 A031 REVELL 4366 A-7A CORSAIR 1.72 AIRCRAFT 23 A007 A04211 ADMIRAL GRAF SPEE 1600 SHIP 24 ROB A01314 AEC MATADOR (D-DAY) 1.76 VEHICLE 25 A026 A04046 AH-1 T SEA COBRA 1.72 HELICOPTER 26 A005 A03077 AH-64 APACHE LONGBOW 1.72 HELICOPTER 27 A014 A07101 AH-64 APACHE LONGBOW 1.48 HELICOPTER 28 A026 A04044 AH-64 APACHE LONGBOW 1.72 HELICOPTER 29 A008 A02014 AICHI D3AI VAL (VJ DAY) 1.72 AIRCRAFT 30 ROB AIRFIX 1972 CATALOUGE BOOK 31 ROB AIRFIX 1974 CATALOUGE BOOK 32 ROB AIRFIX 1983 CATALOUGE BOOK 33 ROB A78183 AIRFIX 2007 CATALOUGE BOOK 34 ROB A78184 AIRFIX 2008 CATALOUGE BOOK 35 ROB AIRFIX CLUB
    [Show full text]
  • Design, Modelling and Control of a Space UAV for Mars Exploration
    Design, Modelling and Control of a Space UAV for Mars Exploration Akash Patel Space Engineering, master's level (120 credits) 2021 Luleå University of Technology Department of Computer Science, Electrical and Space Engineering Design, Modelling and Control of a Space UAV for Mars Exploration Akash Patel Department of Computer Science, Electrical and Space Engineering Faculty of Space Science and Technology Luleå University of Technology Submitted in partial satisfaction of the requirements for the Degree of Masters in Space Science and Technology Supervisor Dr George Nikolakopoulos January 2021 Acknowledgements I would like to take this opportunity to thank my thesis supervisor Dr. George Nikolakopoulos who has laid a concrete foundation for me to learn and apply the concepts of robotics and automation for this project. I would be forever grateful to George Nikolakopoulos for believing in me and for supporting me in making this master thesis a success through tough times. I am thankful to him for putting me in loop with different personnel from the robotics group of LTU to get guidance on various topics. I would like to thank Christoforos Kanellakis for guiding me in the control part of this thesis. I would also like to thank Björn Lindquist for providing me with additional research material and for explaining low level and high level controllers for UAV. I am grateful to have been a part of the robotics group at Luleå University of Technology and I thank the members of the robotics group for their time, support and considerations for my master thesis. I would also like to thank Professor Lars-Göran Westerberg from LTU for his guidance in develop- ment of fluid simulations for this master thesis project.
    [Show full text]
  • Real-Time Helicopter Flight Control: Modelling and Control by Linearization and Neural Networks
    Purdue University Purdue e-Pubs Department of Electrical and Computer Department of Electrical and Computer Engineering Technical Reports Engineering August 1991 Real-Time Helicopter Flight Control: Modelling and Control by Linearization and Neural Networks Tobias J. Pallett Purdue University School of Electrical Engineering Shaheen Ahmad Purdue University School of Electrical Engineering Follow this and additional works at: https://docs.lib.purdue.edu/ecetr Pallett, Tobias J. and Ahmad, Shaheen, "Real-Time Helicopter Flight Control: Modelling and Control by Linearization and Neural Networks" (1991). Department of Electrical and Computer Engineering Technical Reports. Paper 317. https://docs.lib.purdue.edu/ecetr/317 This document has been made available through Purdue e-Pubs, a service of the Purdue University Libraries. Please contact [email protected] for additional information. Real-Time Helicopter Flight Control: Modelling and Control by Linearization and Neural Networks Tobias J. Pallett Shaheen Ahmad TR-EE 91-35 August 1991 Real-Time Helicopter Flight Control: Modelling and Control by Lineal-ization and Neural Networks Tobias J. Pallett and Shaheen Ahmad Real-Time Robot Control Laboratory, School of Electrical Engineering, Purdue University West Lafayette, IN 47907 USA ABSTRACT In this report we determine the dynamic model of a miniature helicopter in hovering flight. Identification procedures for the nonlinear terms are also described. The model is then used to design several linearized control laws and a neural network controller. The controllers were then flight tested on a miniature helicopter flight control test bed the details of which are also presented in this report. Experimental performance of the linearized and neural network controllers are discussed.
    [Show full text]
  • Assessment of Navy Heavy-Lift Aircraft Options
    THE ARTS This PDF document was made available from www.rand.org as a public CHILD POLICY service of the RAND Corporation. CIVIL JUSTICE EDUCATION Jump down to document ENERGY AND ENVIRONMENT 6 HEALTH AND HEALTH CARE INTERNATIONAL AFFAIRS The RAND Corporation is a nonprofit research NATIONAL SECURITY POPULATION AND AGING organization providing objective analysis and effective PUBLIC SAFETY solutions that address the challenges facing the public SCIENCE AND TECHNOLOGY and private sectors around the world. SUBSTANCE ABUSE TERRORISM AND HOMELAND SECURITY TRANSPORTATION AND INFRASTRUCTURE Support RAND WORKFORCE AND WORKPLACE Purchase this document Browse Books & Publications Make a charitable contribution For More Information Visit RAND at www.rand.org Explore RAND National Defense Research Institute View document details Limited Electronic Distribution Rights This document and trademark(s) contained herein are protected by law as indicated in a notice appearing later in this work. This electronic representation of RAND intellectual property is provided for non- commercial use only. Permission is required from RAND to reproduce, or reuse in another form, any of our research documents for commercial use. This product is part of the RAND Corporation documented briefing series. RAND documented briefings are based on research briefed to a client, sponsor, or targeted au- dience and provide additional information on a specific topic. Although documented briefings have been peer reviewed, they are not expected to be comprehensive and may present preliminary findings. Assessment of Navy Heavy-Lift Aircraft Options John Gordon IV, Peter A. Wilson, Jon Grossman, Dan Deamon, Mark Edwards, Darryl Lenhardt, Dan Norton, William Sollfrey Prepared for the United States Navy Approved for public release; unlimited distribution The research described in this report was prepared for the United States Navy.
    [Show full text]
  • Helicopter Dynamics Concerning Retreating Blade Stall on a Coaxial Helicopter
    Helicopter Dynamics Concerning Retreating Blade Stall on a Coaxial Helicopter A project presented to The Faculty of the Department of Aerospace Engineering San José State University In partial fulfillment of the requirements for the degree Master of Science in Aerospace Engineering by Aaron Ford May 2019 approved by Prof. Jeanine Hunter Faculty Advisor © 2019 Aaron Ford ALL RIGHTS RESERVED ABSTRACT Helicopter Dynamics Concerning Retreating Blade Stall on a Coaxial Helicopter by Aaron Ford A model of helicopter blade flapping dynamics is created to determine the occurrence of retreating blade stall on a coaxial helicopter with pusher-propeller in straight and level flight. Equations of motion are developed, and blade element theory is utilized to evaluate the appropriate aerodynamics. Modelling of the blade flapping behavior is verified against benchmark data and then used to determine the angle of attack distribution about the rotor disk for standard helicopter configurations utilizing both hinged and hingeless rotor blades. Modelling of the coaxial configuration with the pusher-prop in straight and level flight is then considered. An approach was taken that minimizes the angle of attack and generation of lift on the advancing side while minimizing them on the retreating side of the rotor disk. The resulting asymmetric lift distribution is compensated for by using both counter-rotating rotor disks to maximize lift on their respective advancing sides and reduce drag on their respective retreating sides. The result is an elimination of retreating blade stall in the coaxial and pusher-propeller configuration. Finally, an assessment of the lift capability of the configuration at both sea level and at “high and hot” conditions were made.
    [Show full text]
  • Adventures in Low Disk Loading VTOL Design
    NASA/TP—2018–219981 Adventures in Low Disk Loading VTOL Design Mike Scully Ames Research Center Moffett Field, California Click here: Press F1 key (Windows) or Help key (Mac) for help September 2018 This page is required and contains approved text that cannot be changed. NASA STI Program ... in Profile Since its founding, NASA has been dedicated • CONFERENCE PUBLICATION. to the advancement of aeronautics and space Collected papers from scientific and science. The NASA scientific and technical technical conferences, symposia, seminars, information (STI) program plays a key part in or other meetings sponsored or co- helping NASA maintain this important role. sponsored by NASA. The NASA STI program operates under the • SPECIAL PUBLICATION. Scientific, auspices of the Agency Chief Information technical, or historical information from Officer. It collects, organizes, provides for NASA programs, projects, and missions, archiving, and disseminates NASA’s STI. The often concerned with subjects having NASA STI program provides access to the NTRS substantial public interest. Registered and its public interface, the NASA Technical Reports Server, thus providing one of • TECHNICAL TRANSLATION. the largest collections of aeronautical and space English-language translations of foreign science STI in the world. Results are published in scientific and technical material pertinent to both non-NASA channels and by NASA in the NASA’s mission. NASA STI Report Series, which includes the following report types: Specialized services also include organizing and publishing research results, distributing • TECHNICAL PUBLICATION. Reports of specialized research announcements and feeds, completed research or a major significant providing information desk and personal search phase of research that present the results of support, and enabling data exchange services.
    [Show full text]
  • National Advisory Committee for Aeronautics
    NATIONAL ADVISORY COMMITTEE FOR AERONAUTICS TECHNICAL NOTE 2154 AN ANALYSIS OF TIlE AUTOROTATIVE PERFORMANCE OF A BELICOPTER POWERED BY ROTOR-TIP JET UN[TS By Alfred Gessow Langley Aeronautical Laboratory Langley Air Force Base, Va. Washington July 1950 NATIONAL ADVISORY COMMITTEE FOR AERONAUTICS TECHNICAL NOTE 2l AN ANALYSIS OF THE AUTOROTATIVE PERFORMANCE OF A HELICOPTER POWERED BY ROTOR-TIP JET UNITS By Alfred Gessow SUMMARY The autorotative performance of an assumed helicopter was studied to determine the effect of inoperative jet units located at the rotor- blade tip on the helicopter rate of descent. For a representative ram- jet design, the effect of the jet drag is to increase the minimum rate of descent of the helicopter from about l,OO feet per minute to 3,700 feet per minute when the rotor is operating at a tip speed of approximately 600 feet per second. The effect is less if the rotor operates at lower tip speeds, but the rotor kinetic energy and the stall margin available for the landing maneuver are then reduced. Power-off rates of descent of pulse-jet helicopters would be expected to be less than those of ram- jet.helicopters because pulse jets of current design appear to have greater ratios of net power-on thrust to power-off, drag than currently designed rain jets. Iii order to obtain greater accuracy in studies of autorotative per- forimance, calculations in'volving high power-off rates of descent should include the weight-supporting effect of the fuselage parasite-drag force and the fact that the rotor thrust does not equal the weight of the helicopter.
    [Show full text]
  • Micro Coaxial Helicopter Controller Design
    Micro Coaxial Helicopter Controller Design A Thesis Submitted to the Faculty of Drexel University by Zelimir Husnic in partial fulfillment of the requirements for the degree of Doctor of Philosophy December 2014 c Copyright 2014 Zelimir Husnic. All Rights Reserved. ii Dedications To my parents and family. iii Acknowledgments There are many people who need to be acknowledged for their involvement in this research and their support for many years. I would like to dedicate my thankfulness to Dr. Bor-Chin Chang, without whom this work would not have started. As an excellent academic advisor, he has always been a helpful and inspiring mentor. Dr. B. C. Chang provided me with guidance and direction. Special thanks goes to Dr. Mishah Salman and Dr. Humayun Kabir for their mentorship and help. I would like to convey thanks to my entire thesis committee: Dr. Chang, Dr. Kwatny, Dr. Yousuff, Dr. Zhou and Dr. Kabir. Above all, I express my sincere thanks to my family for their unconditional love and support. iv v Table of Contents List of Tables ........................................... viii List of Figures .......................................... ix Abstract .............................................. xiii 1. Introduction .......................................... 1 1.1 Vehicles to be Discussed................................... 1 1.2 Coaxial Benefits ....................................... 2 1.3 Motivation .......................................... 3 2. Helicopter Flight Dynamics ................................ 4 2.1 Introduction ........................................
    [Show full text]
  • Open Walsh Thesis.Pdf
    The Pennsylvania State University The Graduate School College of Engineering A PRELIMINARY ACOUSTIC INVESTIGATION OF A COAXIAL HELICOPTER IN HIGH-SPEED FLIGHT A Thesis in Aerospace Engineering by Gregory Walsh c 2016 Gregory Walsh Submitted in Partial Fulfillment of the Requirements for the Degree of Master of Science August 2016 The thesis of Gregory Walsh was reviewed and approved∗ by the following: Kenneth S. Brentner Professor of Aerospace Engineering Thesis Advisor Jacob W. Langelaan Associate Professor of Aerospace Engineering George A. Lesieutre Professor of Aerospace Engineering Head of the Department of Aerospace Engineering ∗Signatures are on file in the Graduate School. Abstract The desire for a vertical takeoff and landing (VTOL) aircraft capable of high forward flight speeds is very strong. Compound lift-offset coaxial helicopter designs have been proposed and have demonstrated the ability to fulfill this desire. However, with high forward speeds, noise is an important concern that has yet to be thoroughly addressed with this rotorcraft configuration. This work utilizes a coupling between the Rotorcraft Comprehensive Analysis System (RCAS) and PSU-WOPWOP, to computationally explore the acoustics of a lift-offset coaxial rotor sys- tem. Specifically, unique characteristics of lift-offset coaxial rotor system noise are identified, and design features and trim settings specific to a compound lift-offset coaxial helicopter are considered for noise reduction. At some observer locations, there is constructive interference of the coaxial acoustic pressure pulses, such that the two signals add completely. The locations of these constructive interferences can be altered by modifying the upper-lower rotor blade phasing, providing an overall acoustic benefit.
    [Show full text]