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Tiltrotor Conceptual Design NASA/CR—2017–219474 Tiltrotor Conceptual Design Franklin D. Harris F. D. Harris & Associates Ames Research Center, Moffett Field, California Prepared for Monterey Technologies, Inc. Subcontract No. REMS.201303 Task Order No. NNA15BB93T Click here: Press F1 key (Windows) or Help key (Mac) for help March 2017 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. NASA Programs and include extensive data or theoretical analysis. Includes compilations For more information about the NASA STI of significant scientific and technical data program, see the following: and information deemed to be of continuing reference value. NASA counterpart of peer- • Access the NASA STI program home page reviewed formal professional papers but has at http://www.sti.nasa.gov less stringent limitations on manuscript length and extent of graphic presentations. • E-mail your question to [email protected] • TECHNICAL MEMORANDUM. • Phone the NASA STI Information Desk at Scientific and technical findings that are 757-864-9658 preliminary or of specialized interest, e.g., quick release reports, working • Write to: papers, and bibliographies that contain NASA STI Information Desk minimal annotation. Does not contain Mail Stop 148 extensive analysis. NASA Langley Research Center Hampton, VA 23681-2199 • CONTRACTOR REPORT. Scientific and technical findings by NASA-sponsored contractors and grantees. NASA/CR—2017–219474 Tiltrotor Conceptual Design Franklin D. Harris F. D. Harris & Associates Ames Research Center, Moffett Field, California Prepared for Monterey Technologies, Inc. Subcontract No. REMS.201303 Task Order No. NNA15BB93T National Aeronautics and Space Administration Ames Research Center Moffett Field, CA 94035-1000 March 2017 Available from: NASA STI Support Services National Technical Information Service Mail Stop 148 5301 Shawnee Road NASA Langley Research Center Alexandria, VA 22312 Hampton, VA 23681-2199 [email protected] 757-864-9658 703-605-6000 This report is also available in electronic form at http://ntrs.nasa.gov TABLE OF CONTENTS List of Figures................................................................................................................................ iv List of Tables ................................................................................................................................. vi Introduction......................................................................................................................................1 Preliminary Performance Trend Studies ..........................................................................................2 Performance Fundamentals .........................................................................................................2 The Primary Design Space..........................................................................................................6 Proprotor Design ............................................................................................................................10 Design Fundamentals ................................................................................................................11 Proprotor Conceptual Design Results to Date ...............................................................................17 Airframe Design .............................................................................................................................28 Conclusions....................................................................................................................................34 References......................................................................................................................................35 Appendix A—F. D. Harris’ Presentation at the AHS Technical Meeting on Aeromechanics Design for Vertical Lift ...........................................................................................37 Appendix B—C81Gen/ARC2D Airfoil Tables for Cruise ............................................................63 Appendix C—C81Gen/ARC2D Airfoil Tables and Graphs for Hover .........................................69 Appendix D—C81Gen/ARC2D Evaluation Using NACA 0012 Airfoil Data ..............................77 iii LIST OF FIGURES Figure 1. V/STOL performance goals. .......................................................................................1 Figure 2. Fundamental aircraft performance equations. .............................................................2 Figure 3. Typical turboshaft maximum continuous power lapse rates on a standard day. .........3 Figure 4. Typical turboshaft maximum rated power lapse rates on a standard day with 95oF outside air temperature. ......................................................................................4 Figure 5. Cruise altitude is a very important parameter when choosing an engine’s rated power (this is because of typical turboshaft engine lapse rates). ................................5 Figure 6. The smallest installed engine comes with a low cruise altitude. ................................6 Figure 7. Cruise altitude is more influential than cruise speed for a given aircraft lift-to-drag ratio. For a given rotor diameter, the higher the FM the better. ................................7 Figure 8. Maximizing aircraft lift-to-drag ratio is a key design objective. ................................8 Figure 9. Designing for STOL may be better than designing for VTOL. ..................................9 Figure 10a. LCTR-2005 blade geometry. ....................................................................................10 Figure 10b. LCTR-2005 blade airfoil thickness ratio distribution. ..............................................10 Figure 11. Kenneth Hall’s optimum loading distributions. ........................................................12 Figure 12. Kenneth Hall’s induced velocities computed with optimum loading distributions...............................................................................................................12 Figure 13. Airfoil L/D is the driving factor for a given design thrust. .......................................13 Figure 14. Thrust loss due to airfoil drag is not to be ignored. ..................................................14 Figure 15. Design 1’s twist and chord blade geometry is well suited for cruise. .......................17 Figure 16. Design 1’s airfoil thickness ratio and spar thickness blade geometry is well suited for cruise. ................................................................................................18 Figure 17. Design 1 blade element operating at Mach and Reynolds number conditions. ........19 Figure 18. NASA SC(2)-0012 aerodynamic characteristics (fully turbulent model). ................19 Figure 19. NASA SC(2)-0010 aerodynamic characteristics (fully turbulent model). ................20 Figure 20. NASA SC(2)-0008 aerodynamic characteristics (fully turbulent model). ................20 Figure 21. NASA SC(2)-0006 aerodynamic characteristics (fully turbulent model). ................21 Figure 22. Optimum airfoil aerodynamic characteristics to shoot for (fully turbulent model). .............................................................................................21 Figure 23. Proprotor performance trends. ..................................................................................23 Figure 24. Maximum installed power trends. .............................................................................23 iv LIST OF FIGURES (cont.) Figure 25. LCTR-2016 proprotor design 1—blade element lift coefficient and Mach number in cruise at 425 kts at 25,000 ft, a tip speed of 300 fps, and a thrust of 3,787 lb per proprotor. Hover data at 5,000 ft, 95oF, a tip speed of 800 fps, and a thrust of 72,000 lb per proprotor. This configuration has four blades. ..............................24 Figure 26. LCTR-2016 proprotor design 1—blade element thrust loading.
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