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US-12623776-B2 - Free wing multirotor transitional S/VTOL aircraft

US12623776B2US 12623776 B2US12623776 B2US 12623776B2US-12623776-B2

Abstract

An improved aircraft design to harness advantages of vertical or short-takeoff and landings (V/STOL) and efficient horizontal flight is disclosed. The aircraft design includes multiple thrust sources and wings which are free to rotate on a spanwise axis, and have their center of gravity aft of the axis of rotation. Wing rotation is decoupled from both the fuselage and the thrust sources. Wings are coupled to each other such that rotation induced in one wing affects rotation in all wings. Thrust sources are directed vertically during hover and some degree forward of vertical for horizontal flight. The disclosed configuration improves aircraft flight stability and efficiency in all flight profiles: vertical flight, transition to/from horizontal flight, and horizontal flight. The aircraft has the possibility of a controlled emergency landing using autorotation of the propellers, wings or a combination of the two.

Inventors

  • Edward Dolejsi
  • Daniel Heim

Assignees

  • Autonomous Flight Systems Inc.

Dates

Publication Date
20260512
Application Date
20220331

Claims (19)

  1. 1 . An aircraft comprising: free wings having control surfaces; a fuselage; a vertical stabilizer; spars positioned both fore and aft, and on both left and right sides of the fuselage; and multiple rotatably thrust producing rotors producing both vertical and horizontal thrust vectors, wherein the free wings are mounted on each one of the spars such that they each are free to rotate about the spar on a span wise spar-centered axis without physical or mechanical coupling to the thrust producing rotors and the fuselage, the free wings are coupled front-to-back and side-to-side with each other such that a rotation induced in one free wing affects all free wings, and a center of mass of each free wing is located at a distance behind the spar-centered axis of rotation; the rotatably thrust producing rotors are configured with propellers, are mounted on ends of each one of the spars, and are rotatable from a horizontal to a vertical orientation.
  2. 2 . The aircraft of claim 1 wherein the propellers are variable pitch.
  3. 3 . The aircraft of claim 1 wherein a relative angle of attack of the fore and the aft wings can be adjusted.
  4. 4 . The aircraft of claim 1 wherein a relative angle of attack of the left and the right wings can be adjusted.
  5. 5 . An aircraft comprising: an airframe comprising two or more spars positioned fore and aft on the airframe and extending laterally; free wings having control surfaces are positioned on the spars such that they rotate about the spar on a spar-centered axis of rotation; at least three rotatably from horizontal to vertical thrust producing rotors located at outermost ends of each one of the spars; wherein the free wings are mechanically coupled front-to-back and side-to-side with each other such that a rotation induced in one free wing affects all free wings, and a center of mass of each free wing is located at a distance aft of the spar-centered axis of rotation, and the free wings rotate about their respective spar without physical or mechanical coupling to a fuselage and the rotatably thrust producing rotors.
  6. 6 . The aircraft according to claim 5 , wherein each of the rotatably thrust producing rotors rotate about the respective spar without physical or mechanical coupling to the free wing.
  7. 7 . The aircraft according to claim 5 , wherein a relative angle of attack of the fore and the aft wings can be adjusted.
  8. 8 . The aircraft according to claim 5 , wherein a relative angle of attack of a left wing and a right wing can be adjusted.
  9. 9 . The aircraft according to claim 5 , wherein during horizontal flight, the free wings are positioned horizontally with the airframe and induce lift.
  10. 10 . The aircraft according to claim 5 , wherein during vertical flight, the free wings are positioned in a chord vertical attitude.
  11. 11 . The aircraft according to claim 5 , wherein the airframe is maintained in a generally horizontal attitude throughout vertical, transitional and horizontal flight modes.
  12. 12 . The aircraft according to claim 5 , wherein the at least three thrust producing rotors are configured to provide stability to the aircraft in vertical, transitional, and horizontal flight modes.
  13. 13 . An aircraft comprising: a fuselage comprising a vertical stabilizer, two sides, a floor, and at least two spars coupled thereto and extending laterally therefrom; four rotatably from horizontal to vertical thrust producing rotors with one positioned on each spar; free wings having control surfaces positioned on each spar having a spar-centered center of rotation, coupled front-to-back and side-to-side with one another and without physical or mechanical coupling to and between the fuselage and the rotatably thrust producing rotors; wherein a center of mass of each free wing is located aft of the spar-centered center of rotation of the free wing, and each of the four rotatably thrust producing rotors is located outside of each free wing.
  14. 14 . The aircraft according to claim 13 , wherein the thrust producing rotors rotate about the spar without physical or mechanical coupling to the free wing.
  15. 15 . The aircraft according to claim 13 , wherein each thrust producing rotor comprises a propeller, and configured to tilt through a range of motion for vertical, transitional, and horizontal flight modes.
  16. 16 . The aircraft according to claim 13 , wherein during vertical flight, the free wings are positioned in a chord vertical attitude.
  17. 17 . The aircraft according to claim 13 , wherein the four rotatably thrust producing rotors are configured to provide stability to the aircraft in vertical, transitional, and horizontal flight modes.
  18. 18 . The aircraft according to claim 9 , wherein the free wings are positioned horizontally aerodynamically.
  19. 19 . The aircraft according to claim 10 , wherein during vertical flight, the free wings are positioned gravitationally in the chord vertical attitude.

Description

RELATED US APPLICATION DATA Provisional Patent No. 63/170,540, filed Apr. 4, 2021 FIELD OF SEARCH B64C29/0025, B64C27/52 244/7R, 244/17.25, 244/6. US PATENT DOCUMENTS CITED 2,708,081May 1955Dobson3,029,043April 1962Churchill3,430,894March 1969Strand, et al3,934,843January 1976Black4,967,984November 1990Allen5,086,993February 1992Wainfan5,280,863January 1994Schmittle5,395,073March 1997Rutan, et alRE 36,487January 2000Wainfan6,863,241March 2005Sash8,505,846August 2013Sanders, II8,567,709October 2013Dudley et al10,589,838March 2020Supes11,242,142February 2022Sanders II11,254,430February 2022Regev OTHER PUBLICATIONS CITED “Wind Tunnel Tests of a Free-Wing Tilt-Propeller V/STOL Airplane Model”. T. Strand, E. S. Levinsky, Technical Report AFFDL-69-80, October 1969“Investigation of the Applicability of the Free-wing Principle to Light, General Aviation Aircraft”. Richard F. Porter et al., NASA CR-246 June 1972“Experimental Investigation of Stability and Stall Flutter of a Free-floating Wing V/Stol Model”. Robert A. Ormiston; NASA TN D-6831 June 1972“Flight Tests of a Radio-controlled Airplane Model with a Free-wing, Free-canard Configuration”. Shu W. Gee, Samuel R. Brown, NASA TM-72853, March 1978“Extended Analytical Study of the Free-wing/Free-trimmer Concept”. Richard F. Porter, et al., NASA Contractor Report 3135, 1979 TECHNICAL FIELD The present invention relates generally to short field and vertical take-off and landing (STOL/VTOL) aircraft and, more particularly, to a STOL/VTOL aircraft, capable of transitioning to efficient horizontal flight. BACKGROUND Heavier than air flight is an industry with a century long history of innovation. The commercial success of aircraft attests to the usefulness of air transport. The majority of aircraft in production today fall into one of two types: (1.) airplanes with fixed wings and rotors aligned horizontally to provide efficient long-range flight and, (2.) rotorcraft with rotor aligned vertically providing efficient vertical flight and hover capability. A third type of aircraft design is pursued by inventors, corporate and government entities since the mid twentieth century; aircraft capable of vertical take-off and transitioning to horizontal flight on wing. This type of aircraft is given many names: convertiplane, transitional aircraft or, VTOL. The great number of widely varying designs is a testament to the ingenuity of the inventors working in this field. Designs include: twin tilt rotors and tilt wings; tandem or multiple wings and/or tilt rotors and tilt wings; aircraft with separate lift and thrust rotors. Some of these aircraft have found niche markets; the V22 Osprey—a twin tilt rotor with single wing—is currently in use by a number of military organizations. However, transitional aircraft have yet to be fully embraced by the flying public or found wide commercial success. Stability through the transition from vertical flight to horizontal flight is a main issue for transitional aircraft. Aerodynamic instability in these aircraft arise in part as a result of wings that are coupled with rotors and fuselage. Any disturbance to the attitude/pitch affects both the wing lift, and airspeed of the aircraft. A wind gust, or pilot input, pitching the aircraft nose up momentarily increases lift and drag on the wing. Subsequently, the aircraft slows, loses lift and pitches down. In this attitude drag is reduced, velocity increases. An oscillation results until longitudinal stability is re-established, or control becomes unrecoverable. If a disturbance occurs at low airspeeds, close to ground—during take-off or landing, for example—the initiation of such an oscillation can have undesirable consequences; a bounce, hard landing or even crash. Recent advances in technologies such as, electronic stabilization and auto pilot control are able to somewhat overcome the lack of stability these aircraft exhibit during the transition flight envelop. However, without inherent aerodynamic stability, transitional aircraft are likely to continue to find resistance to acceptance and, lack a broader commercial market as well as, difficulty in achieving regulatory approval. SUMMARY OF INVENTION The current invention discloses an improved aircraft design. The aircraft is of the VTOL/STOL (Vertical Take-Off and Landing/Short-field Take-Off and Landing) type. The aircraft is capable of vertical take-off; transitioning to, and back, from efficient horizontal flight on wings. The most important attribute of the aircraft is stability throughout all regimes of flight: hover, transition, slow flight and, horizontal flight. Through a combination of gliding on wings and autorotation of the rotors, the design also makes possible safe, unpowered, emergency landings. The current specification discloses an improved aircraft design to harness advantages of vertical or short-takeoff and landings (V/STOL) and efficient horizontal flight. The disclosed configuration improves aircraft flight stability and ef