USOO899.174.4B1 (12) United States Patent (10) Patent No.: US 8,991,744 B1 Khan (45) Date of Patent: Mar. 31, 2015 (54) ROTOR-MAST-TILTINGAPPARATUS AND 4,099,671 A 7, 1978 Leibach METHOD FOR OPTIMIZED CROSSING OF 35856 A : 3. Wi NATURAL FREQUENCIES 5,850,6154. W-1 A 12/1998 OSderSO ea. 6,099.254. A * 8/2000 Blaas et al. ................... 416,114 (75) Inventor: Jehan Zeb Khan, Savoy, IL (US) 6,231,005 B1* 5/2001 Costes ....................... 244f1725 6,280,141 B1 8/2001 Rampal et al. (73) Assignee: Groen Brothers Aviation, Inc., Salt 6,352,220 B1 3/2002 Banks et al. Lake City, UT (US) 6,885,917 B2 4/2005 Osder et al. s 7,137,591 B2 11/2006 Carter et al. (*) Notice: Subject to any disclaimer, the term of this 16. R 1239 sign patent is extended or adjusted under 35 2004/0232280 A1* 11/2004 Carter et al. ............... 244f1725 U.S.C. 154(b) by 494 days. OTHER PUBLICATIONS (21) Appl. No.: 13/373,412 John Ballard etal. An Investigation of a Stoppable Helicopter Rotor (22) Filed: Nov. 14, 2011 with Circulation Control NASA, Aug. 1980. Related U.S. Application Data (Continued) (60) Provisional application No. 61/575,196, filed on Aug. hR". application No. 61/575,204, Primary Examiner — Joseph W. Sanderson • Y-s (74) Attorney, Agent, or Firm — Pate Baird, PLLC (51) Int. Cl. B64C 27/52 (2006.01) B64C 27/02 (2006.01) (57) ABSTRACT ;Sp 1% 3:08: A method and apparatus for optimized crossing of natural (52) U.S. Cl frequencies of a rotorcraft rotor are disclosed. The method CPC B64C 27/52 (2013.01); G05D 19/00 may include flying a rotorcraft comprising an airframe, a - - - - - - - - - - -(2013 01); B64C 2702 (2013 01); B64C rotor, a mast extending to connect the rotor to the airframe, a s 27/001 (201 3.01) tilt mechanism, and a computer system. The computer system USPC ...... 244/17.13: 244/8: 244/1711; 244/1725, may identify during the flying, an impending crossing of a 701/3 natural frequency of the rotor. In preparation for the crossing, (58) Field of Classification Search the computer system may issue at least one command to the USPC ........... 244/6, 7 R, 7 C, 8, 12.4, 17.11, 17.25, tilt mechanism. In response to the command, the tilt mecha 244/17.13: 701/3 nism may reorient the mast with respect to the airframe. That See application file for complete search history. reorientation quickly results in a change to the rotational speed of the rotor, moving it quickly across the natural fre (56) References Cited quency. The reorientation may also prevent the rotor from experiencing any significantly deleterious flapping loads dur U.S. PATENT DOCUMENTS ing the crossing of the natural frequency. 2,601.463 A 6/1952 Stanley 3,649,132 A 3, 1972 Arcidiacono ................... 416, 18 3,957,226 A 5/1976 Daggett, Jr. et al. 20 Claims, 11 Drawing Sheets US 8,991.744 B1 Page 2 (56) References Cited D.M. Martin et al. Experimental Investigation of Advance Hub and Pylon Fairing Configurations to Reduce Helicopter Drag, NASA OTHER PUBLICATIONS Technical Memorandum 4540, Sep.1993. Franklin D. Harris et al. An Overview of Autogyros and the McDon Fairey Aviation Company, The Fairey Rotodyne 40-44 Passenger nell XV-1 Convertiplane, NASA/CR, Oct. 2003. Helicopter, England, May 1954. A. Stepan, Journal of the Helicopter Association of Great Britain— Arthur W. Linden and James C. Biggers, X-Wing Potential for Navy vol. 13, No. 6, Dec. 1949. Applications, estimated 1959. A. Stepan, Journal of the Royal Aeronautical Society, London, Feb. Robert Sopher and James Duh, Prediction of Aeroelastic Response of 1958. a model X-Wing Rotor Sikorsky Aircraft Division, United Technolo Fairey Rotodyne Type 20Z 10W and Performance, Technical Pub gies, Feb. 19-21, 1986. lications, Project 79, Issue 2, Feb. 1959. J.R. Ewans et al., Further Model Wind Tunnel Tests of a Reverse Fairey Aviation Company, Fairey Rotodyne, Weights and perfor Velocity Rotor System. Fairchild Republic Company, Jul. 1975. Fairey Aviation Limited, Fairey Rotodyne Design Z. Mar. 23, 1960. mance Index, estimated 1959. Fairey Rotodyne Description and Drawings, estimated 1959. Fairey Aviation Company, The Fairey Rotodyne 40-48 Passenger Fairey Rotodyne Description Specifications, estimated 1959. Helicopter, England, estimated 1959. E. Wilde et al., The Flapping Behavior of a Helicopter Rotor at High Fairey Aviation Company, The Fairey Rotodyne Design Certificate, Tip-Speed Rations, Ministry of Aviation, London, 1966. estimated 1959. Michael G. Gilbert et al., The Effects of Aeroelastic Deformation on Fairey Aviation Company, Tactical Mobility, Fairey Rotodyne for the the Unaugmented Stopped-Rotor Dynamics of an X-Wing Aircraft, Services, estimated 1959. NASA, Jun. 1987. William Willshire, Rye Canyon X-Wing Noise Test: One-Third D. N. Goldstein et al., Rotorcraft convertible Engine Study, Final Octave Band Data, NASA Technical Memorandum, Jan. 1983. Report, NASA Lewis Research Center, Aug. 1983. Bruce D. Charles et al., Wind Tunnel Investigation of Semi rigid G. Warren Hall et al., Flight Testing the Fixed-Wing Configuration of Full-Scale Rotors Operating a High Advance Ratios, U.S. Army the Rotor Systems Research Aircraft, NASA, Jun. 1985. Aviation Material Laboratories, Fort Eustis, Virginia, Jan. 1969. Gerald J. Healy, X-Wing Noise Data Acquisition Program, NASA, Jessica Woods et al., Results of a Parametric Aeroelastic Stability Feb. 1983. Analysis of a Generic X-Wing Aircraft, NASATechnical Memoran G. S. Hislop, The Fairey Rotodyne. A paper to be presented to a Joint dum 101572, Apr. 1989. Meeting of the Helicopter Association of Great Britain, Nov. 7, 1958. Franlkin D. Harris et al. The XV-1's Rotor System. AHS Interna S.L. Smith, Jet Research Report, Evaluation of Rotor Power and a tional, Jan. 21-24, 2004. Comparison With Predicted Performance, May 1, 1958. S. Coham et al., XV-9A Hot Cycle Research Aircraft Program Sum K. T. Mckenzie, The Journal of the Helicopter Association of Great Britain, Aerodynamic Aspects of the Fairey Rotodyne, Dec. 1959. mary Report, U.S. Army Aviation Material Laboratories, Fort Eustis, M. Mosher, Acoustic Measurements of the X-Wing Rotor, NASA Virginia, Jun. 1966. Technical Memorandum 94292, Ames Research Center, Moffett G.S. Hislop, The Fairey Rotodyne. A paper to be presented to a Joint Field, CA, 1983. Meeting of the Helicopter Association of Great Britain, Nov. 7, 1958. David H. Hickey, NACA Research Memorandum, Full-Scale Wind Franklin D. Harris et al. The XV-1's Rotor System. AHS Interna Tunnel Tests, National Advisory Committee for Aeronautics, May tional, Jan. 21-24, 2004. 17, 1956. Fairey Rotodyne-Type 20Z 10W and Performance, Technical Publi Watson H. Tanner, Charts for Estimating Rotary Wing Performance cations, Project 79, Issue 2, Feb. 1959. in Hover and at High Forward Speeds, NASA Contractor Report, Nov. 1964. * cited by examiner U.S. Patent Mar. 31, 2015 Sheet 1 of 11 US 8,991,744 B1 U.S. Patent Mar. 31, 2015 Sheet 2 of 11 US 8,991,744 B1 FIG. 2 U.S. Patent Mar. 31, 2015 Sheet 3 of 11 US 8,991,744 B1 42 42 42 78 42 8O FIG. 3C U.S. Patent Mar. 31, 2015 Sheet 4 of 11 US 8,991,744 B1 FIG. 5 U.S. Patent Mar. 31, 2015 Sheet 5 of 11 US 8,991,744 B1 -92 Flight-Control Computer Components System 96 82 Computer System 100 Flight-Control Component (e.g., Mast) 98 One or More Actuators FIG. 7 U.S. Patent Mar. 31, 2015 Sheet 6 of 11 US 8,991,744 B1 102 N Rotor Speed Range 106 10 - TOT?. 9 3rd Flapping Frequency 1st Torsion Frequency 8 Normalized 7 2nd Flapping Frequency 5th Order Frequency 6 1st Lag Frequency (Elastic Blade No Root Lag Flex) 1st Lag Frequency 2nd Order As 5 1st Flapping Frequency 3rd Order p P s O 5.0 10.0 15.0 2O.O 25.0 30.0 35.0 Rotor Speed (rad/sec) FIG. 8 U.S. Patent Mar. 31, 2015 Sheet 7 of 11 US 8,991,744 B1 Nelf s FIG. 9 U.S. Patent Sheet 8 of 11 US 8,991,744 B1 YZZZZZ2 32 24% 2 3. 25 60 2 Salaza 4444 2 O aar azg 122 120- es 98-N- 82 FIG 10 U.S. Patent Mar. 31, 2015 Sheet 9 of 11 US 8,991,744 B1 re U.S. Patent Mar. 31, 2015 Sheet 10 of 11 US 8,991,744 B1 U.S. Patent Mar. 31, 2015 Sheet 11 of 11 US 8,991,744 B1 122a 120a 122b EAHO) - 124a- SNiZ, 1 ; 112a 130 126b 132b 124b 124b. FIG. 13 US 8,991,744 B1 1. 2 ROTOR-MAST TILTINGAPPARATUS AND 61/506,572, filed on Jul. 11, 2011, U.S. Provisional Patent METHOD FOR OPTIMIZED CROSSING OF Application Ser. No. 61/519,075, filed on May 16, 2011, U.S. NATURAL FREQUENCIES Provisional Patent Application Ser. No. 61/519,055, filed on May 16, 2011, U.S. Provisional Patent Application Ser. No. RIGHTS OF U.S. GOVERNMENT 61/460,573, filed on Jan. 4, 2011, U.S. Provisional Patent Application Ser. No. 61/461223, filed on Jan. 13, 2011, U.S. This invention was made with Government support under Provisional Patent Application Ser. No. 61/429,282, filed on Agreement No. HR0011-06-9-0002 awarded by DARPA. Jan. 3, 2011, U.S. Provisional Patent Application Ser. No. The Government has certain rights in the invention. 61/429,289, filed on Jan. 3, 2011, U.S. Provisional Patent 10 Application Ser.