NASA/TP—2015–218714 The Cierva Autodynamic Rotor Jean-Pierre Harrison Ames Research Center Moffett Field, California March 2015 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, information (STI) program plays a key part in seminars, or other meetings sponsored helping NASA maintain this important role. or co-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. 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NASA/TP—2015–218714 The Cierva Autodynamic Rotor Jean-Pierre Harrison Ames Research Center Moffett Field, California National Aeronautics and Space Administration Ames Research Center Moffett Field, CA 94035-1000 March 2015 Acknowledgments Thanks to the following individuals for their assistance with, review, and critique of this paper: Roger Connor, Franklin Harris, Mike Hirschberg, Wayne Johnson, Charles Mac Kay, and Robert Ormiston. The author grants in perpetuity the U.S. Government a cost-free license to publish and distribute without restriction this paper. Copyright © 2014, 2015 Jean-Pierre Harrison Available from: NASA Center for AeroSpace Information National Technical Information Service 7115 Standard Drive 5301 Shawnee Road Hanover, MD 21076-1320 Alexandria, VA 22312 443-757-5802 703-605-6000 This report is also available in electronic form at http:/ntrs.nasa.gov TABLE OF CONTENTS The Cierva Autodynamic Rotor .......................................................................................................1 Conclusion .....................................................................................................................................33 Appendix A: C.40 Rotor Hub Details ............................................................................................35 Appendix B: Autogiros Used for Autodynamic Rotor Tests ..........................................................37 Appendix C: Autodynamic Rotor Patents ......................................................................................39 Appendix D: Autodynamic Rotor Patent Illustrations ...................................................................45 References ......................................................................................................................................57 Bibliography ..................................................................................................................................59 LIST OF FIGURES Figure 1: Juan de la Cierva. ...........................................................................................................1 Figure 2: Tilting hub, swashplate, and spider rotor control systems. ............................................2 Figure 3: The Cierva C-4 Autogiro with lateral control bellcrank below rotor hub. .....................3 Figure 4: Rotor blade hinge axes. ..................................................................................................4 Figure 5: F.L. Hodgess, J.A.J. Bennett, Maurice Brennan, R.F. Bowyer, G.E. Walker, and R. Pullin with the Weir W-5 helicopter in 1938. ............................................................6 Figure 6: The C.30 Autogiro G-ACFI with standard fixed-pitch rotor before tests with autodynamic hub. ...........................................................................................................6 Figure 7: Autodynamic rotor with positive drag-feather coupling and single central drag damper. Tested on the C.30 G-ACFI (U.S. Patent 2,380,583). ......................................7 Figure 8: Autodynamic rotor with negative drag-feather alpha-1 coupling and individual drag dampers Tested on the C.30 Mk.II. .......................................................................9 Figure 9: Harold F. Pitcairn (photo from author’s collection). ......................................................9 Figure 10: The Cierva C.8R, 1927. ...............................................................................................10 Figure 11: The Weir W-3 rotor hub. ..............................................................................................12 Figure 12: The Weir W-3 with engine cowl removed. ..................................................................12 Figure 13: The Weir W.3 two-blade autodynamic rotor hub with high-ratio negative drag-feather alpha-1 coupling and low-ratio flap-drag delta-2 coupling. No drag dampers (U.S. Patent 2,216,768). ........................................................................12 Figure 14: The C.30 Mk.III two-blade autodynamic rotor hub with low-ratio negative drag-feather alpha-1 coupling and positive delta-3 coupling. No drag dampers (U.S. Patent 2,216,768). ...............................................................................................13 Figure 15: Autodynamic rotor test pilot Alan Marsh (photo courtesy of John T. Bent). ..............15 Figure 16: Autodynamic rotor hub fitted with camera to record coupled negative alpha-2 drag-flap blade motion, G-ACWF (clockwise-turning rotor), 1936 (photo courtesy of John T. Bent). .................................................................................16 Figure 17: Autodynamic hubs of the type tested on G-ACWF (U.S. Patent 2,197,677). .............17 Figure 18: The C.30 Mk.III executing jump-takeoff at Hounslow Heath, 17 July 1936. .............19 Figure 19: The Weir W-3 executing jump-takeoff at Hanworth Aerodrome. ................................19 iii LIST OF FIGURES (cont.) Figure 20: The C.30 Mk.III autodynamic hub with alpha hinge torsion bearing replaced by stranded cable (U.S. Patent 2,173,153). ..................................................................21 Figure 21: The Pitcairn PA-22 with two-blade autodynamic rotor (photo courtesy of the National Air and Space Museum) ................................................................................23 Figure 22: The Weir W-4 with adjustable direct-takeoff rotor hub (photo courtesy of the Weir Group) .................................................................................................................26 Figure 23: The Cierva C.40 ...........................................................................................................27 Figure 24: The Pitcairn PA-36 hub (photo courtesy of the National Air and Space Museum) .....29 Figure 25: The Pitcairn PA-36 (photo courtesy of the U.S. Army Signal Corps) .........................29 Figure 26: The Pitcairn PA-39 .......................................................................................................31 Figure 27: The Fairey Gyrodyne rotor hub ...................................................................................31 Figure 28: The Fairey Gyrodyne ...................................................................................................32 Figure A-1: The C.40 rotor hub, side view (U.S. Patent 2,252,544) .............................................36 Figure A-2: The C.40 rotor hub, top view (U.S. Patent 2,252,544) ...............................................36 Figure D-1: U.S. Patent 2,105,682. ................................................................................................45 Figure D-2: U.S. Patent 2,121,536. ................................................................................................46