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NAVAL POSTGRADUATE SCHOOL Monterey, California THESIS FLIGHT OPERATIONS FOR HIGHER HARMONIC CONTROL RESEARCH by James Joseph McGovern March, 1991 Thesis Advisor: E. Roberts Wood Approved for public release; distribution is unlimited. CO T253650 Jnclassified ZURITY CLASSIFICATION OF THIS PAGE REPORT DOCUMENTATION PAGE FormApproved OMBNo 0704 0188 REPORT SECURITY CLASSIFICATION 1b RESTRICTIVE MARKINGS UNCLASSIFIED i. SECURITY CLASSIFICATION AUTHORITY 3ADpIpSrTRoIvBUeTdIONf/AoVrAILpAuBIbLlIiTYcOFreRlEPeOaRsTe; distribution ). DECLASSIFICATION/DOWNGRADING SCHEDULE is unlimited. PERFORMING ORGANIZATION REPORT NUMBER(S) 5 MONITORING ORGANIZATION REPORT NUMBER(S) I. NAME OF PERFORMING ORGANIZATION 6b OFFICE SYMBOL 7a NAME OF MONITORING ORGANIZATION (If applicable) Naval Postgraduate School AA Naval Postgraduate School :. ADDRESS {City, State, and ZIPCode) 7b ADDRESS(C/fy, State, and ZIPCode) Monterey, CA 93943-5000 Monterey, CA 93943-5000 ». NAME OF FUNDING/SPONSORING 8b OFFICE SYMBOL 9 PROCUREMENT INSTRUMENT IDENTIFICATION NUMBER ORGANIZATION (If applicable) . ADDRESS(City, State,and ZIPCode) 10 SOURCE OF FUNDING NUMBERS PROGRAM PROJECT TASK WORK UNIT ELEMENT NO NO NO ACCESSION NO 1. TITLE (Include Security Classification) FLIGHT OPERATIONS FOR HIGHER HARMONIC CONTROL RESEARCH (U) PERSONAL AUTHOR(S) !McGovern, James J. la. TYPE OF REPORT 13b TIME COVERED 14 DATE OF REPORT {Year,Month, Day) IS PAGE COUNT Master's Thesis FROM TO March 1991 63 SUPPLEMENTARY NOTATION > The views expressed in this thesis are those of the author and do not reflect the official policy or position of the Defense Department or the U.S. Government. COSATI CODES 18 SUBJECT TERMS {Continue on reverse if necessary and identify by block number) FIELD GROUP SUB-GROUP HHC, RPH, Flight Operations, Vibrations, Flight Test ) ABSTRACT {Continue on reverse if necessary and identify by block number) The Department ofAeronautics and Astronautics at the Naval Postgraduate School (NFS) is interested in extending the useful life of Naval helicopters. Recognizing the need to reduce vibrations caused by aerodynamic loads on the rotor system, a Higher Harmonic Control (HHC) research effort has begun. The test HHC vehicle of the system is a Remotely Piloted Helicopter (RPH). This thesis contains an overview of the NPS HHC research effort includingbasic helicopter dynamics, HHC theory, and establishes research milestones. An RPH flight operations program was developed that included the first flights oftwo out ofthree RPH's being used in the research effort, identification of data and data acquisition requirements, and initial hover vibration tests. The vibration tests produced data oflimited value. The two bladcd RPH tested appears to produce peak accelerations at roughly twice the main rotor speed. This indicates that like a full scale helicopter, the largest vibrations do enter the airframe through the rotor system and are not a result of engine vibrations. Hence, RPH's are suitable for HHC research. This effort completed one portion of the long term HHC research and HHC can lead to the practical and safe testing of a fully functioning system. DISTRIBUTION/AVAILABILITY OF ABSTRACT 21 ABSTRACT SECURITY CLASSIFICATION SUNCLASSIFIED/UNLIMITED D SAME AS RPT DTIC USERS Unclassified ?a NAME OF RESPONSIBLE INDIVIDUAL 22b TELEPHONE (Include AreaCode) 22c OFFICE SYMBOL Professor E.R. Wood (408) 646-2311 AA/Wd 3Form 1473. JUN 86 Previouseditionsareobsolete SECURITY CLASSIFICATION OF THIS PAGE Unclassified S/N 0102-LF-014-6603 Approved for public release; distribution is unlimited. Flight Operations For Higher Harmonic Control Research by James Joseph McGovern Lieutenant, United States Navy B.S., United States Naval Academy, 1983 Submitted in partial fulfillment of the requirements for the degree of MASTER OF SCIENCE IN AERONAUTICAL ENGINEERING from the NAVAL POSTGRADUATE SCHOOL March 1991 ABSTRACT The Department of Aeronautics and Astronautics at the Naval Postgraduate School (NPS) is interested in extending the useful life of Naval helicopters. Recognizing the need to reduce vibrations caused by aerodynamic loads on the rotor system, a Higher Harmonic Control (HHC) research effort has begun. The test HHC vehicle of the system is a Remotely Piloted Helicopter (RPH). This thesis contains an overview of the NPS HHC research effort including basic helicopter dynamics, HHC theory, and establishes research milestones. An RPH flight operations program was developed that included the first flights of two out of three RPH's being used in the research effort, identification of data and data acquisition requirements, and initial hover vibration tests. The vibration tests produced data of limited value. The two bladed RPH tested appears to produce peak accelerations at roughly twice the main rotor speed. This indicates that like a full scale helicopter, the largest vibrations do enter the airframe through the rotor system and are not a HHC result of engine vibrations. Hence, RPH's are suitable for research. This HHC effort completed one portion of the long term research and can lead to the HHC practical and safe testing of a fully functioning system. in TABLE OF CONTENTS BACKGROUND I. 1 A. HELICOPTER VIBRATION 1 VIBRATION REDUCTION B. 3 1. Passive Techniques 3 2. Active Techniques 5 SCOPE II. 7 HIGHER HARMONIC CONTROL III. 8 HELICOPTER DYNAMICS A. 8 HHC THEORY B. 11 HHC RESEARCH EFFORT C. 13 1. Goals 13 HHC 2. Flight Testing 15 3. Remotely Piloted Helicopters 15 RPH 4. Support Facilities 15 5. Data Gathering 17 IV