Tri-Rotor Aircraft Capable of Vertical Takeoff and Landing and Transitioning to Forward Flight

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(12) (io) Patent No.:

United States Patent US 10,071,801 B2

North et al. (45) 11,2018

Date of Patent: Sep.

(54) TRI-ROTOR AIRCRAFT CAPABLE OF (52) U.S. Cl.

CPC ............ B64C 29/0033 (2013.01); B64C 5/02 VERTICAL TAKEOFF AND LANDING AND (2013.01); B64C 25/52 (2013.01); TRANSITIONING TO FORWARD FLIGHT (Continued) (71) Applicant: The United States of America as (58) Field of Classification Search represented by the Administrator of CPC ............ B64C 29/0033; B64C 29/0075; B64C the National Aeronautics and Space 29/0083; B64C 2201/088; B64C 1/28; Administration, Washington, DC(US) (Continued) (72) Inventors: David D. North, Williamsburg, VA (56) References Cited (US); Mark J. Aull, Cincinatti, OH (US); William J. Fredericks, U.S. PATENT DOCUMENTS Williamsburg, VA (US); Mark D.

2,462,201 A 2/1949 Kilgore et al.

Moore, Williamsburg, VA (US); Paul 2,783,956 A 3/1957 Harriss M. Rothhaar, Newport News, VA (Continued) (US); William T. Hodges, Yorktown, VA (US); Zachary R. Johns, Virginia FOREIGN PATENT DOCUMENTS Beach, VA (US) DE 102005003608 Al 8/2006 (73) Assignee: THE UNITED STATES OF DE 102007012875 Al 9/2008 AMERICA AS REPRESENTED BY (Continued) THE ADMINISTRATOR OF NASA, Washington, DC (US) OTHER PUBLICATIONS (*) Notice: Subject to any disclaimer, the term ofthis Fredericks, W. J., "Conceptual Design of a Vertical Takeoff and patent is extended or adjusted under 35 Landing Unmanned Aerial Vehicle with 24-hr Endurance," AUVSI U.S.C. 154(b) by 0 days. Unmanned Systems Conference, Aug. 23-26, 2010, pp. 1-17, Den- ver, CO.

(21) Appl. No.: 15/080,167 (Continued) (22) Filed: Mar. 24, 2016 Primary Examiner Richard R Green (74) Attorney, Agent, or Firm Rubin W. Edwards; (65) Prior Publication Data Mark P. Dvorscak US 2016/0200436 Al Jul. 14, 2016 (57) ABSTRACT Related U.S. Application Data Systems, methods, and devices provide a vehicle, such as an (63) Continuation-in-part of application No. 14/121,001, aircraft, with rotors configured to function as a tri-copter for filed on Aug. 13, 2014.

vertical takeoff and landing ("VTOL") and a fixed-wing vehicle for forward flight. One rotor may be mounted at a (Continued) front ofthe vehicle fuselage on a hinged structure controlled (51) Int. Cl. by an actuator to tilt from horizontal to vertical positions.

B64C 29/00 (2006.01) Two additional rotors may be mounted on the horizontal B64C 5/02 (2006.01) surface of the vehicle tail structure with rotor axes oriented (Continued) (Continued)

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Page 2 2010/0286884 Al 11/2010 Bunn vertically to the fuselage. For forward flight of the vehicle, 2010/0301168 Al * 12/2010 Raposo ................... B64C 27/20 the front rotor may be rotated down such that the front rotor 244/171.2 axis may be oriented horizontally along the fuselage and the 2011/0001020 Al 1/2011 Forgac front rotor may act as a propeller. For vertical flight, the front 2011/0066338 Al 3/2011 Andrasko et al.

rotor may be rotated up such that the front rotor axis may be 2011/0315809 Al* 12/2011 Oliver ................. B64C 29/0033 oriented vertically to the fuselage, while the tail rotors may 244/12.4 2012/0012692 Al 1/2012 Kroo be activated.

2012/0046841 Al 2/2012 Wurthner et al.

2013/0094963 Al 4/2013 Rolt 15 Claims, 20 Drawing Sheets FOREIGN PATENT DOCUMENTS DE 102009028242 Al 2/2011 Related U.S. Application Data DE 102009045091 Al 3/2011 DE 102010003673 Al 10/2011 EP 2570345 Al * 3/2013 ......... B64C 29/0033 (60) Provisional application No. 61/865,347, filed onAug.

EP 2581308 A2 4/2013 13, 2013, provisional application No. 62/137,634, GB 2497136 A 6/2013 WO 2009060241 Al 5/2009 filed on Mar. 24, 2015.

WO 2010121861 Al 10/2010 WO 2010128898 Al 11/2010 (51) Int. Cl.

B64C 25/52 (2006.01) OTHER PUBLICATIONS B64D 27/24 (2006.01) B64C 39/02 (2006.01) Fredericks, W. J., "Aircraft Conceptual Design Using Vehicle Sketch B64D 27102 (2006.01) Pad," 48th AIAA Aerospace Sciences Meeting, Jan. 4-7, 2010, pp.

(52) U.S. Cl.

1-17, Orlando, Florida.

CPC ........ B64C 29/0025 (2013.01); B64C 39/024 Project Page for xflr5, Accessed on Mar. 22, 2016,http://www.xflr5.

(2013.01); B64D 27/24 (2013.01); B64C com/xflr5.htm, Jan. 2016, pp. 1-4.

22011042 (2013.01); B64C 22011044 Moore, Mark D., "Concept of Operations for Highly Autonomous (2013.01); B64D 20271026 (2013.01); Y02T Electric Zip Aviation", 12th Aviation Technology, Integration and 50144 (2013.01); Y02T 50/64 (2013.01) Operations (ATIO) Conference, Sep. 17-19, 2012, pp. 2012-5472, (58) Field of Classification Search pp. 1-15, Indianapolis, Indiana.

CPC ....... B64C 1/30; B64C 39/003; B64C 39/005; Patterson, Michael D. and German, Brian J.,"Performance Analysis B64C 39/08; B64C 3/385; B64D 27/02; and Design of On-Demand Electric Aircraft Concepts", 12th Avia- B64D 27/04; B64D 2027/026 tion Technology, Integration and Operations (ATIO) Conference, See application file for complete search history. Sep. 17-19, 2012, 2012-5474, pp. 1-28, Indianapolis, Indiana.

Smith, Jeremy C. and Viken, Jeffrey K., "Projected Demand and (56) References Cited Potential Impacts to the National Airspace System of Autonomous, Electric, On-Demand Small Aircrac", Sep. 17-19, 2012, pp. 1-21, U.S. PATENT DOCUMENTS Indianapolis, Indiana.

Miranda, Luis and Brennan, James E., "Aerodynamic Effects of 2,793,827 A * 5/1957 Ries ........................ B64C 35/00 Wingtip-Mounted Propellers and Turbines", AIAA 4th Applied 244/102 R Aerodynamics Conference, Jun. 9-11, 1986, AIAA Paper No. A86- 2,980,368 A 4/1961 Jakimiuk et al.

37826, pp. 221-228, San Diego, California.

2,994,492 A * 8/1961 Dobson ............... B64C 29/0033 Goldschmied, F.R., "Jet Propulsion of Subsonic Bodies with Jet 244/66 Total-Head Equal to Free Stream's", AIAA Applied Aerodynamics 3,582,021 A * 6/1971 Pender .................... B64C 29/02 244/17.19 Conference, Jul. 13-15, 1983, AIAA Paper No. 83-1790, pp. 1-7, 4,149,688 A 4/1979 Miller, Jr. Danvers, Massachusetts.

4,436,261 A * 3/1984 Koleff ................. B64C 29/0033 Paulson, John W.,"Wind Tunnel Investigation of a Fowler Flap and 244/1 R Spoiler for an Advanced General Aviation Wing", NASA Technical 4,605,185 A 8/1986 Reyes Note TN D-8236, Jun. 1976.

4,900,226 A 2/1990 De Vries U.S. Appl. No. 14/121,001, filed Aug. 13, 2014, entitled "Vertical 4,936,526 A * 6/1990 Gries ...................... B64C 11/28 Take-Off and Landing Vehicle with Increased Cruise Efficiency".

244/53 R Bradley, M. et al., "NASA N+3 Subsonic Ultra Green Aircraft 5,082,204 A 1/1992 Croston Research SUGAR Final Review,"Apr. 20,2010,http://aviationweek.

5,823,468 A 10/1998 Bothe 6,095,945 A 8/2000 Graf typepad.com/files/boeing sugar_phase_i_final_review_v5.pdf.

6,293,491 BI* 9/2001 Wobben .................. B64C 27/00 Moore, Mark D. et al., "High-Speed Mobility Through On-Demand 244/17.23 Aviation," AIAA Aviation Technology, Integration, and Operations 7,131,613 B2 11/2006 Kelly Conference, Aug. 12-14, 2013, pp. 1-27, Los Angeles, CA.

8,066,219 B2 * 11/2011 Part ..................... B64C 29/0033 Fredericks, William J. et al., "Benefits of Hybrid-Electric Propul- 244/12.4 sion to Achieve 4x Increase in Cruise Efficiency for a VTOL 8,469,306 B2 6/2013 Kuhn, Jr.

Aircraft," AIAA Aviation Technology, Integration, Operations Con- 8,733,690 B2 5/2014 Bevirt et al.

ference, Aug. 12-14, 2013, pp. 1-21, Los Angeles, CA.

8,800,912 B2 8/2014 Oliver Rothhaar, Paul M. et al., "NASA Langley Distributed Propulsion 9,085,355 B2 * 7/2015 DeLorean ........... B64C 29/0033 VTOL Tilt-Wing Aircraft Testing, Modeling, Simulation, Control, 9,096,312 B2 8/2015 Moxon and Flight Test Development," 14th AIAA Aviation Technology, 2004/0118969 Al 6/2004 MacCready et al.

Integration, and Operations Conference, Jun. 16-20, 2014, pp. 1-14, 2005/0014605 Al 1/2005 Ries-Mueller Atlanta, Georgia.

2006/0254255 Al 11/2006 Okai et al.

Busan, Ronald C. et al.,"Enabling Advanced Wind-Tunnel Research 2007/0124037 Al 5/2007 Moran 2008/0184906 Al 8/2008 Kejha Methods Using the NASA Langley 12-Foot Low Speed Tunnel,"

US 10,071,801 B2

Page 3 (56) References Cited OTHER PUBLICATIONS 14th AIAA Aviation Technology, Integration, and Operations Con- ference, Jun. 16-20, 2014, pp. 1-22, Atlanta, Georgia.

Moore, Mark D., "High Speed Mobility Through On-Demand Aviation," Presentation Slides, AIAA Aviation Technology, Integra- tion, and Operations Conference, Aug. 12-14, 2013, pp. 1-34, Los Angeles, CA.

Fredericks, William, J. et al., "Project Reimar III Greased Lightning Overview," NASA Aeronautics Presentation Slides, Jan. 28, 2013, pp. 1-17.

* cited by examiner

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TRI-ROTOR AIRCRAFT CAPABLE OF BRIEF SUMMARY OF THE INVENTION VERTICAL TAKEOFF AND LANDING AND TRANSITIONING TO FORWARD FLIGHT The systems, methods, and devices of the present inven- tion combine an advanced vehicle configuration, such as an CROSS-REFERENCE TO RELATED PATENT 5 advanced aircraft configuration, with the infusion of electric APPLICATIONS propulsion, thereby enabling a four times increase in range and endurance while maintaining a full vertical takeoff and This patent application is a continuation-in-part of, and landing ("VTOL") and hover capability for the vehicle. In claims the benefit of priority to, co-pending U.S. non- this manner, various embodiments may provide vehicles, to provisional patent application Ser. No. 14/121,001 entitled such as aircraft, with both VTOL and cruise efficient capa- "Vertical Take-Off and Landing Vehicle with Increased bilities that may meet VTOL and cruise efficiency require- Cruise Efficiency" filed Aug. 13, 2014, which claims the ments without the use of ground infrastructure. The various benefit of and priority to U.S. provisional patent application embodiments may provide a VTOL and cruise efficient No. 61/865,347 entitled "Benefits of Hybrid-Electric Pro- 15 vehicle, such as an aircraft, comprising a wing configured to pulsion To Achieve 4x Increase In Cruise Efficiency for a tilt through a range of motion, a first series ofelectric motors VTOL Aircraft' filed on Aug. 13, 2013. This patent appli- coupled to the wing and each configured to drive an asso- cation also claims the benefit of priority to U.S. provisional ciated wing propeller, a tail configured to tilt through the patent application No. 62/137,634 entitled "Tri-Rotor Air- range of motion, a second series of electric motors coupled craft Capable of Vertical Takeoff and Landing and Transi- to the tail and each configured to drive an associated tail tioning to Forward Flight" filed Mar. 24, 2015. The entire propeller, and an electric propulsion system connected to the contents of all three applications are hereby incorporated by first series ofelectric motors and the second series ofelectric reference in their entirety. motors. In a further embodiment, the electric propulsion system may be a battery augmented series hybrid electric STATEMENT REGARDING FEDERALLY 25 propulsion system comprising one or more internal com- SPONSORED RESEARCH OR DEVELOPMENT bustion engines, one or more generators coupled to the one or more internal combustion engines and connected to the The invention described herein was made in part by first series ofelectric motors and the second series ofelectric employees of the United States Government and may be motors, and one or more batteries connected to the first manufactured and used by or for the Government of the series of electric motors and the second series of electric United States ofAmerica for governmental purposes without motors.

the payment of any royalties thereon or therefore.

The systems, methods, and devices of the present inven- tion provide a vehicle, such as an aircraft, with rotors BACKGROUND OF THE INVENTION configured to function as a tri-copter for VTOL and a fixed-wing vehicle for forward flight.In an embodiment, one Vertical takeoff and landing ("VTOL") and cruise effi- rotor may be mounted at a front of the vehicle fuselage on ciency are diametrically opposed requirements for aircraft.

a hinged structure controlled by an actuator to tilt from There are system solutions today that require ground infra- horizontal to vertical positions. In an additional embodi- structure, namely catapults and arresting equipment, to ment, two additional rotors may be mounted on the hori- launch and recover cruise efficient aircraft, thereby impart- 40 zontal surface of the vehicle tail structure with rotor axes ing these aircraft with VTOL like capabilities. These current oriented vertically (e.g., perpendicular)to the fuselage. In an multi-part systems remove the need for the actual aircraft to perform VTOL,but the system as a whole (i.e., aircraft plus embodiment,for forward flight ofthe vehicle, the front rotor ground infrastructure) becomes a VTOL system. With these may be rotated down such that the front rotor axis may be current systems it is not possible to meet both VTOL and 45 oriented horizontally (e.g., parallel) along the fuselage and cruise efficiency requirements without the use of ground the front rotor may act as a propeller, while the tail rotors infrastructure.

may be deactivated. In an embodiment, for vertical flight, Fixed wing aircraft are faster and more fuel efficient than the front rotor may be rotated up such that the front rotor axis rotary winged aircraft, while rotary winged aircraft can may be oriented vertically (e.g., perpendicular) to the fuse- hover and do not require long runways for takeoff and 50 lage, while the tail rotors may be activated.

landing. Many potential missions make aircraft combining These and other features, advantages, and objects of the these features desirable, but current aircraft configurations present invention will be further understood and appreciated that are capable of vertical takeoff and transitioning to by those skilled in the art by reference to the following horizontal flight, including tilt-rotors, tilt-wings, and tail- specification, claims, and appended drawings.

sitters usually result in significant compromises in the per- 55 formance of the aircraft in both the VTOL and horizontal BRIEF DESCRIPTION OF THE SEVERAL flight modes because of the competing requirements of VIEWS OF THE DRAWINGS VTOL and efficient forward flight capabilities. For example, tail-sitters have relatively poor stability at landing because The accompanying drawings, which are incorporated the center of gravity is relatively high, and tail-sitters are 60 herein and constitute part of this specification, illustrate limited to small aircraft because the tail structure must exemplary embodiments of the invention, and together with support the weight of the aircraft. Additionally, the fuselage the general description given above and the detailed descrip- of tail-sitters is vertical on the runway limiting the types of tion given below, serve to explain the features of the cargo that may be carried. Tilt-rotors and tilt-wings provide invention.

vertical takeoff and transition, but are complex designs that 65 FIG. 1 is a component block diagram illustrating a front/ present challenges with packaging the mechanisms for tilt- left upper perspective view of an embodiment VTOL and ing inside the aircraft wing. cruise efficient aircraft.

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FIG. 2 is a component block diagram illustrating a front/ embodiments disclosed herein are not to be considered as right lower perspective view of the embodiment VTOL and limiting, unless the claims expressly state otherwise.

The word "exemplary"is used herein to mean "serving as cruise efficient aircraft.

an example, instance, or illustration." Any implementation FIG. 3 is a top view of an embodiment of a pylon for the s described herein as "exemplary" is not necessarily to be present invention.

construed as preferred or advantageous over other imple- FIG. 4 is a component block diagram illustrating a front mentations.

view of the embodiment VTOL and cruise efficient aircraft.

The various embodiments will be described in detail with FIG. 5 is a component block diagram illustrating a left reference to the accompanying drawings. Wherever pos- side view of the embodiment VTOL and cruise efficient io sible, the same reference numbers will be used throughout aircraft in a VTOL flight phase.

the drawings to refer to the same or like parts. References FIG. 6 is a component block diagram illustrating a left made to particular examples and implementations are for side view of the embodiment VTOL and cruise efficient illustrative purposes, and are not intended to limit the scope aircraft transitioning between the VTOL flight phase and a of the invention or the claims.

wing born flight phase.

15 Electric propulsion may enable radical new vehicle con- FIG. 7 is a component block diagram illustrating a left cepts and configurations, particularly for vertical takeoff and side view of the embodiment VTOL and cruise efficient landing ("VTOL") aircraft because electric propulsion may aircraft in the wing born flight phase.

address the significant mismatch between takeoff and cruise FIG. 8 is a component block diagram illustrating a top power conditions experienced by VTOL aircraft. The ability view of an embodiment tri-rotor vehicle.

20 to distribute the thrust across the airframe, without mechani- FIG. 9A is a component block diagram illustrating a cal complexity and with a scale free propulsion system, may front/left upper perspective view ofthe embodiment tri-rotor provide a new degree of freedom for aircraft designers.

vehicle.

The various embodiment vehicle configurations may FIG. 9B is a component block diagram illustrating a combine an advanced vehicle configuration, such as an front/left upper perspective view ofthe embodiment tri-rotor 25 advanced aircraft configuration, with the infusion of electric vehicle in a VTOL flight phase.

propulsion, thereby enabling a four times increase in range FIG. 10 is a component block diagram illustrating a front and endurance while maintaining a full VTOL and hover view of the embodiment tri-rotor vehicle.

capability (similar to the VTOL and hover capabilities of a FIG. 11 is a component block diagram illustrating a helicopter) for the vehicle. In this manner, various embodi- rear/left upper perspective view of the embodiment tri-rotor 30 ments may provide vehicles, such as aircraft, with both vehicle.

VTOL and cruise efficient capabilities that may meet VTOL FIG. 12 is a component block diagram illustrating a left and cruise efficiency requirements without the use of ground side view of the embodiment tri-rotor vehicle in a VTOL infrastructure. Cruise efficient vehicles, such as cruise effi- flight phase.

cient aircraft, may provide various efficiencies based on the FIG. 13 is a component block diagram illustrating a left 35 vehicle mission, such as reduced energy consumption during side view of the embodiment tri-rotor vehicle transitioning flight, long range, and/or long endurance. The various between the VTOL flight phase and a wing born flight phase.

embodiments may also provide the ability to achieve low FIG. 14 is a component block diagram illustrating a left disc-loading for low ground impingement velocities, low side view of the embodiment tri-rotor vehicle in the wing noise, and/or hover power reduction/minimization which born flight phase.

40 may reduce energy consumption in a VTOL phase of flight.

FIG. 15 is a component block diagram illustrating a The systems, methods, and devices ofthe various embodi- front/left upper perspective view of a second embodiment ments may provide a VTOL and cruise efficient vehicle, tri-rotor vehicle in a wing born flight phase.

such as an aircraft, comprising a wing configured to tilt FIG. 16 is a component block diagram illustrating a through a range of motion, a first series of electric motors front/left upper perspective view of the second embodiment 45 coupled to the wing and each configured to drive an asso- tri-rotor vehicle in a VTOL flight phase.

ciated wing propeller, a tail configured to tilt through the FIG. 17 is a component block diagram illustrating a left range of motion, a second series of electric motors coupled side view of the second embodiment tri-rotor vehicle in a to the tail and each configured to drive an associated tail VTOL flight phase.

propeller, and an electric propulsion system connected to the FIG. 18 is a component block diagram illustrating a 50 first series ofelectric motors and the second series ofelectric front/left upper perspective view of a third embodiment motors. In a further embodiment, the electric propulsion tri-rotor vehicle in a VTOL flight phase.

FIG. 19 is a component block diagram illustrating a system may be a battery augmented series hybrid electric propulsion system comprising one or more internal com- front/left upper perspective view of the third embodiment bustion engines, one or more generators coupled to the one tri-rotor vehicle in a wing born flight phase.

FIG. 20 is a component block diagram illustrating a top 55 or more internal combustion engines and connected to the first series ofelectric motors and the second series ofelectric view ofthe third embodiment tri-rotor vehicle in a wing born motors, and one or more batteries connected to the first flight phase.

series of electric motors and the second series of electric DETAILED DESCRIPTION OF THE motors.

INVENTION 60 Electric propulsion may be scale-free in terms of being able to achieve highly similar levels of motor power to For purposes of description herein, it is to be understood weight and efficiency across a dramatic scaling range. Using that the specific devices and processes illustrated in the distributed electric propulsion may enable the various attached drawings, and described in the following specifi- embodiment advanced aircraft configurations to achieve cation, are simply exemplary embodiments of the inventive 65 improvements in aerodynamic efficiency that may be concepts defined in the appended claims. Hence, specific approximately four times that of conventional helicopter dimensions and other physical characteristics relating to the configurations. Helicopters typically achieve a Lift to Drag

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ratio (L/D) of between 4 and 5, while the various embodi- that may be required to be carried on the tail. The embodi- ment VTOL aircraft may achieve an L/D of 15 to 20, such ment semi-tandem wing configuration with a lifting tail may as 15, approximately 15, 15-17, 17-20, approximately 15 to be statically stable in the wing born flight phase (i.e., approximately 20, approximately 20, etc. The various forward flight). In an embodiment, the aircraft may be embodiments provide the ability to eliminate the problem of 5 designed such that the lift coefficient, tail loading, and lift advancing and retreating rotor blades by converting into curve slope of the tail may be less than the lift coefficient, wing born flight without the mechanical complexity of wing loading, and lift curve slope of the wing. In an previous VTOL aircraft. embodiment, the aircraft may include a swept wing to shift The various embodiments may utilize hybrid electric the aerodynamic center of the wing aft in forward flight and propulsion to normalize the power across the mission phases io still keep the center ofthrustforward in hovering flight when and to enable the combustion engine to be sized for wing the wing is rotate up 90 degrees. In an embodiment, the born flight and batteries may be used to supplement the sweep of the wing may enable a reduction in the induced power required in hover. This may yield an overall lighter drag ofthe aircraft. During a hover, propeller thrust needs to propulsion system, which may make for a smaller aircraft, be distributed about the center of gravity of the aircraft.

which may lead to lower cost. 15 Without a swept wing, in forward flight the wing stays in In an embodiment, an aircraft may have one or more front of the center of gravity resulting in only about eighty propellers, such as one, two, three, four, five, six, seven, percent ofthe lift on the wing and twenty percent on the tail.

eight, nine, ten, or more propellers, and one or more electric However, in an embodiment with a swept wing, in a hover, motors may distribute thrust across the propellers. For the propellers are forward of the wing, but in forward flight example, the electric motors may distribute thrust across ten 20 the wing center is farther aft enabling ninety two percent of propellers. In an embodiment,propellers may be mounted to the lift to be on the wing and eight percent to be on the tail.

the leading edge of the wing of the aircraft and mounted to Since the swept wing has higher span (i.e., lower span the leading edge of the tail of the aircraft. The number of loading), it is more efficient to carry lift on the wing.

propellers mounted to the leading edge of the wing of the In an embodiment, forward flight propellers may be aircraft and the leading edge of the tail of the aircraft may 25 located at the wing tips of the aircraft. The wing tip forward vary. For example, in an embodiment in which the aircraft flight propellers may provide a destructive interference may have ten propellers, eight propellers may be mounted to between the propeller swirl and the wing tip vortex. The the leading edge of the wing and two propellers may be resulting interference may be viewed as an induced drag mounted to the leading edge of the tail of the aircraft. In an reduction or a propulsive efficiency increase. In an embodi- embodiment, at least a portion ofthe wing ofthe aircraft and 30 ment, the forward flight propellers may run for the entire at least a portion of the tail of the aircraft may both tilt to mission (i.e., both during the VTOL flight phase and the transition the aircraft between hovering flight and wing born wing born flight phase). In an embodiment, the forward flight. In an embodiment, the wing ofthe aircraft and the tail flight propellers may run only during the wing born flight of the aircraft may both rotate around the lateral axis of the phase. In an embodiment, the forward flight propellers may wing and tail, respectively, to tilt the wing and tail through 35 be variable speed (e.g., variable revolutions per minute a range of motion, thereby pitching the wing and tail up ("RPM")) and/or variable pitch propellers. The use of vari- and/or down relative to the longitudinal axis of the aircraft able speed and/or pitch propellers may maximize propulsive to transition the aircraft between hovering flight (i.e., the efficiency.

VTOL phase) and wing born flight (i.e., the wing born flight In an embodiment, vertical flight propellers may fold phase). The range of motion may be any range of motion, 4o down during the wing born flight phase. In an embodiment, such as less than 90 degrees, 90 degrees, approximately 90 the vertical flight propellers may fold into conformal degrees, greater than 90 degrees, etc. The tilting portions of recesses of the motor pylons. The folding of the vertical the wing of the aircraft and the tail of the aircraft may tilt flight propellers, especially into conformal recesses, may together or independently and may tilt to the same or reduce drag in the wing born flight phase when compared to different orientations in their respective ranges of motion. 45 leaving the vertical flight propellers deployed.In an embodi- In an embodiment, an aircraft may include a semi-tandem ment, the vertical flight props may extend aft of the leading wing configuration. The semi-tandem wing configuration edge ofthe wing and/or tail when folded. In an embodiment, may provide a compromise between a tandem wing con- to prevent the vertical flight propellers from contacting the figuration, which carries half the lift on the tail, and a leading edge of the wing as the vertical flight propellers are conventional wing configuration, which carries no lift on the 50 started, the vertical flight propeller blades may ride along a tail. The center of gravity of the embodiment aircraft with sinusoidal cam to push the blades forward enough to avoid the semi-tandem wing configuration may be located aft of contact with the leading edge of the wing and/or tail.

the wing. The embodiment semi-tandem wing configuration In an embodiment, the propellers may be synchronized may cause some lift to be carried on the tail of the aircraft, electronically to hold a specific phase angle to provide which may allow the propellers on the tail to carry some the 55 destructive interference of each propeller's noise. This may aircraft's weight during a hover in the VTOL flight phase. result in a quieter aircraft as a whole relative to the sound For example, the tail may carry less than fifty percent of the generated by each propeller in isolation. In an embodiment, lift. However,the wing may carry most ofthe lift of aircraft. each successive propeller may rotate in an alternate direction The embodiment semi-tandem wing configuration may to prevent the wake of one propeller blade impacting the enable the wing to be proportionally larger than the tail and 60 wake of the adjoining propeller blade. In this manner, the achieve a greater span in order to reduce induced drag. In an wakes of the propellers may pass in the same direction as embodiment, the aircraft may be designed such that the opposed to colliding head on.

center of gravity location is selected to have the propellers In an embodiment, the aircraft may include reflexed on the wing carry a higher percent of the aircraft's weight flaperons. The use ofreflexed flaperons may delay the onset than the propellers on the tail. In this manner, the propellers 65 of stall on the wing during transition between the VTOL on the tail may provide greater pitch control authority and flight phase and the wing born flight phase. As discussed reduce induced drag ofthe tail by reducing the amount oflift herein,"flaperons" refers to any control surface used as both

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ailerons and flaps. By having reflexed (i.e., trailing edge up) ration ofthe motor to generator RPM may be the ratio ofthe flap deflections, the reflexed flaperons reduce the circulation motor to the generator pole count.

In an embodiment, the use of electric motors to drive the around the airfoil allowing the airfoil to go to a higher angle propellers may provide an aircraft with a propulsion system of attack before airflow separates.

5 that has no single point of failure. The use of multiple In an embodiment, when the tail is tilted vertically in the electric motors may enable the failure of one motor to occur VTOL flight phase, the vertical tail may serve a second role and the aircraft to still fly. Because electric motors may put as a rear landing skid. In an embodiment, the wing tip motor out more power by turning at a higher RPM,in the event of pylons may serve as outboard landing skids, thereby giving a motor failure, other propellers, as required, may be turned the aircraft a wide stance on the ground to reduce tip over io at a higher RPM by their respective motors ensuring the risk at landing.

aircraft may still be flyable. The increase of RPM may put In an embodiment, a dihedral may be configured in the out more thrust per remaining propeller (meaning also more outboard portion of the horizontal tail to provide directional noise), but the aircraft may remain flyable.

stability during the slow speed portion of the transition In an embodiment, the propellers of the aircraft may turn corridor between the VTOL flight phase and the wing born 15 at a low tip speed, enabling the aircraft to achieve a very low flight phase.

noise profile.

In an embodiment, an aircraft may utilize a battery The various embodiments may provide a vehicle, such as augmented series hybrid electric propulsion system. This an aircraft, with rotors configured to function as a tri-copter use of a battery augmented series hybrid electric propulsion for VTOL and a fixed-wing vehicle for forward flight. In an system may reduce propulsion system weight and enable 20 embodiment, one rotor may be mounted at a front of the unconventional configurations. In an embodiment, all pro- vehicle fuselage on a hinged structure controlled by an pellers may be turned by electric motors. In an embodiment, actuator to tilt from horizontal to vertical positions. In an electrical power to operate each motor may be provided additional embodiment, two additional rotors may be from one or both of two sources. A first source may be a mounted on the horizontal surface of the vehicle tail struc- primary electrical source comprised of generators driven by 25 ture with rotor axes oriented vertically (e.g., perpendicular) internal combustion engines. A second electrical source may to the fuselage.

be battery packs. In an embodiment, the internal combustion In an embodiment, for forward flight of the vehicle, the engines may be sized to meet the power requirements during front rotor may be rotated down such that the front rotor axis the wing born flight phase, but the power required in the may be oriented horizontally (e.g., parallel) along the fuse- VTOL flight phase and during transition may be greater than 30 lage and the front rotor may act as a propeller, while the tail the power required in the wing born flight phase. The battery rotors may be deactivated. For example, when the tail rotors packs may be sized to make up for the difference between are deactivated the tail rotors may be stowed in pods, the power required in the VTOL flight phase and during allowed to weathervane, oriented such that the long axis is transition and the power the internal combustion engines aligned with the air flow (e.g., via the use of the motor may provided by turning the alternators. This embodiment 35 magnets, external magnets, or other fixtures), or otherwise configuration may support the minimum propulsion system operate in an unpowered mode. During forward flight con- weight(as opposed to sizing the internal combustion engines trol surfaces, such as ailerons, rudders, elevators, etc., may for power required for VTOL flight) for missions where the control the vehicle movement and/or orientation.

time spent in hover may be a small percent ofthe time spent In an embodiment, for vertical flight, the front rotor may in wing born flight. The embodiment series hybrid propul- 4o be rotated up such that the front rotor axis may be oriented sion system may effectively act as an "electric driveshaft" vertically (e.g., perpendicular) to the fuselage, while the tail and an "electric gearbox" eliminating the driveshafts and rotors may be activated. The elevators on the tail may be gear boxes necessary to distribute power to each propeller in rotated down, such as close to vertical, to reduce or prevent previous aircraft by filling the same function. In an embodi- obstruction of the air flow from the tail rotors. The elevators ment, in hovering flight the internal combustion engines 45 on the tail may be independently deflecting elevators. Dif- may turn generators, and the electrical power from the ferential thrust may be produced by varying the speed or generators may be fed to a controller that outputs uniform blade pitch (e.g., collectively and/or independently) of the direct current ("DC") power. The DC power may be dis- three rotors (i.e., the front rotor and two tail rotors), and the tributed via wires throughout the aircraft. The DC power thrust produced by the three rotors may enable vertical may be provided to a motor controller associated with each 50 motion ofthe vehicle, as well as pitch, roll, and/or horizontal motor which may convert the DC power to alternating motion. Yaw may be controlled by differentially actuating current ("AC") power to drive the AC motors turning the the left and right elevators to move them toward or away propellers. The advantage ofconverting the AC output ofthe from the vertical position, by actively tilting the tail rotors generators to DC power and the converting the DC power to side to side, and/or actively tilting the tail rotors forward and AC power at each motor may be that the motor controller for 55 aft to provide yaw torque. Yaw torque may also be achieved each motor may independently drive its associated motor by mounting the tail rotors with an outward cant angle.

allowing the RPM to be varied on a per motor basis. The use In an embodiment, during transition from vertical flight to of two controllers may result in some power loss due to the forward flight, the front rotor angle may be changed as the inefficiency of the controllers. In an embodiment, in wing front rotor is rotated from a position the where the front rotor born flight the internal combustion engines may turn the 6o axis may be oriented vertically (e.g., perpendicular) to the generators and the AC power output by the generators may fuselage down to a position where the front rotor axis may be provided via wires directly to the motors without using be oriented horizontally (e.g., parallel) along the fuselage, intermediate controllers, thereby operating the generators and the front rotor speed, tail rotor speeds, and/or elevator and motors in a synchronous mode. This may avoid con- collective angles may be adjusted to maintain altitude and troller loss. The RPM of the generator may need to be equal 65 pitch stability while the vehicle accelerates forward.

to the RPM ofthe motor being driven or if the pole count of The various embodiment tri-rotor design vehicles may the generator is different than the pole count ofthe motor,the enable a larger front rotor than may be used on conventional

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fixed front propeller aircraft because the front rotor may section 102a and 102b and one engine nacelle on each tail rotate parallel to the ground during take-off and landing. In horizontal tail section 102a and 102b. The engine nacelles this manner, the larger diameter rotor may provide an may be comprised of pairings of pylons 103, 104, 105, 106, advantage of noise reduction for the various embodiment 107,108, 109,124, 132, and 133 and respective fairings 111, tri-rotor design vehicles compared to conventional fixed 5 114, 113, 112, 115, 110, 117, 116, 130, and 131. In an front propeller aircraft. embodiment, each of the pylons 103, 104, 105, 106, 107, Cyclic pitch control may not be required on any of the 108, 109, 124, 132, and 133 may have the same outside mold rotors, but may be added to/used with any of the rotors to line("OML") while each of the fairings 110, 111, 112, 113, provide control torques. The various embodiment tri-rotor 114, 115, 116, 117, 130, and 131 may have its own OML.

design vehicles may provide simpler hovering and transi- io Electric motors may be coupled to each pylon 103,104, 105, tioning vehicle designs by providing only a single mecha- 106, 107, 108, 109, 124, 132, and 133 to drive a propeller nism for tilting a propeller,requiring fewer mechanisms than associated with each nacelle. Pylons 108, 106, 104, 124, tilt-rotor or tilt-wing designs. Additionally, cyclic pitch 132, 103, 105, 107, 109, and 133 are illustrated with their control may not be required. The various embodiment respective electric motors 138, 140, 146, 150, 136, 171, 172, tri-rotor design vehicles may keep the vehicle fuselage 15 173, 174, and 180 as well as their respective propellers 152, horizontal during forward flight and vertical flight, thereby 142, 144, 148, 134, 175, 176, 177, 178, and 179. In an allowing an unobstructed field ofview for cameras and other embodiment, propellers 152, 134, 178, and 179 may be sensors, as well as a constant orientation for a communica- variable pitch propellers and propellers 142, 144, 148, 175, tions antenna. As compared to a tail-sitter design, the various 176, and 177 may be fixed pitch propellers. In an embodi- embodiment tri-rotor design vehicles with horizontal fuse- 20 ment, propellers 142, 144, 148, 175, 176, and 177 may fold lage during VTOL mode may enable better vehicle stability down when not in use, such as during wing born flight.

at landing due to the lower center of gravity, vertical g-load Propellers 152, 134, 142, 144, 148, 178, 179, 175, 176, and on the payload at all time which may be advantageous for 177 may have any number of blades, such as two blades, human pilots and passengers, closer payload position to the three blades, etc. In an embodiment, the aircraft 100 may ground after landing, and/or better scalability resulting from 25 include flaperons 118, 119, 120, 121, 122, and 123 on the lower tail structural loads. Additionally, the VTOL configu- wing and flaperons 126 and 127 on the tail. The flaperons ration may reduce ground support requirements, for 118, 119, 120, 121, 122, and 123 may be disposed on the example, by eliminating the need for catapult launchers, trailing edge of the wing between successive nacelles. The reducing runway length, and/or eliminating the need for a flaperons 126 and 127 may be disposed on the trailing edge landing recovery system. so of the tail inboard of the tail mounted nacelles. The aircraft The various embodiment tri-rotor design vehicles may be 100 may also include a vertical control surface on the suitable for use in missions requiring hover capabilities, vertical tail section 102c, such as a rudder 125. The aircraft such as photography ofa remote site, which may also benefit 100 may include a camera 154 extending from the fuselage from added range, as well as missions involving taking off 160. In an embodiment, the aircraft 100 may include landing without an airport or runway, including private or roadable 35 gear, such as retractable nose skids 156 and 158.

aircraft application, bush aircraft, etc. Additionally, the FIG. 2 is a component block diagram illustrating a front/ various embodiment tri-rotor design vehicles may be suit- right lower perspective view of the embodiment VTOL and able for autonomous(unmanned)missions to place payloads cruise efficient aircraft 100 shown with a cutaway view of at extreme distances from a launch and recover site. the fuselage 160. In FIG. 2 the aircraft 100 may be config- Unique wind tunnel testing that combines a nested face- 40 ured for the wing born flight phase with propellers 142, 144, centered design of experiments ("DOE") with optimal 148, 176, 177, 134, and 179 folded back against their design points to achieve testing efficiency and statistically respective pylons. In an embodiment, two primary power sound mathematical models was developed. This method- sources 210 and 212 may be comprised ofinternal combus- ology required new tools and specialized tunnel software to tion engines, such as two eight horse power diesel engines, execute the experiment, such as allowing randomized set 45 coupled to two generators. The fuselage 160 may include a points, as well as substantial automation of both the wind fuel tank 206 storing fuel for the primary power sources 210 tunnel model and test facility. The new methodology and 212. The primary power sources 210 and 212 may be reduced testing time by over sixty years. connected via wires and various controllers (not shown) to The applications for the various embodiment aircraft that each of the electric motors and may provide power to drive may take off and land vertically and yet fly for a long 50 the propellers. In an embodiment, batteries may be housed duration and range are numerous. Applications may range in each nacelle, such as batteries 214,216,218,220, and 222 from military reconnaissance missions, to police and fire and their mirrored counterparts on the opposite side wing department surveillance roles, to civilian automated door to section 101b and horizontal tail section 102b. These batter- door package delivery (e.g., mail, prescription drugs, food, ies may also be connected to the electric motors via wires etc.), to air taxi services. 55 and various controllers (not shown)and may provide power FIGS. 1-7 illustrate various views of an embodiment to drive the propellers. Together the primary power sources VTOL and cruise efficient vehicle, such as aircraft 100. FIG. 210 and 212 and various batteries may comprise a battery 1 is a component block diagram illustrating the front/left augmented series hybrid electric propulsion system for the upper perspective view of the embodiment aircraft 100 with aircraft 100. The aircraft 100 may include a satellite com- the wing (comprised of wing sections 101a and 101b) and bo munication system comprised of various modules 204 and horizontal tail sections 102a and 102b (comprising the 208, and the aircraft may carry a payload 202. As illustrated tilting portions of the overall tail comprised of tiltable in FIG. 2, the skids 156 and 158 may retract up to the horizontal tail sections 102a and 102b and vertical tail fuselage 160 during wing born flight.

section 102c which remains fixed) in the wing born flight In an embodiment, the airfoil may be a custom designed phase configuration (i.e., tilted down parallel to the longi- 65 shape to be a tradeoff between low drag at high lift coefli- tudinal axis of the fuselage 160). In an embodiment, the cients, ease of wing fabrication, and gradual stall character- aircraft 100 may include four engine nacelles on each wing istics. In an embodiment, motor pylons may be shaped to

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minimize drag at high lift coefficients. Normally, when aircraft 100 in the wing born flight phase. The wing and mounting pylons or nacelles at the leading edges of the horizontal tail sections may be tilted down and the propellers wings, the pylons or nacelles mature the boundary layer and 175, 176, 177, and 179 (and their right side counterparts) cause the airflow over the wing to separate early leading to may be stopped and folded back wing born flight phase, a loss of lift and an increase in drag. In an embodiment, the 5 while propeller 178 (and its right side counterpart) may be area of the cross section of the pylons may vary from driven by their respective motors to provide the necessary forward to aft. As an example shown in FIG. 3, the pylons propulsion for wing born flight. During wing born flight, of the various embodiments may have a bottle-type con- pitch may be controlled by elevators for quick changes figuration (or shape) where the cross sectional area may be and/or by tail rotation for slow rotation, roll may be con- comparatively less in the middle portion A of the pylon than io trolled by the flaperons, and yaw may be controlled by the in a forward or aft section ofthe pylon which may minimize rudder.

the super velocity around the pylon, thus reducing the drag In an embodiment, the aircraft 100 may be an unmanned between the wing and the pylon. The bottle configuration (or aerial vehicle, sized to for ease of vehicular roadway trans- shape) of the pylons may reduce the drag due to interaction portation. For example, the aircraft 100 may have a tow with the wing. The airflow must accelerate to move around 15 weight ofless than or equal to two hundred and fifty pounds the thick regions, and it may be desirable to not have the and may break down into no more than three storage boxes.

thick region ofthe wing in the same place as the thick region Aircraft 100 may have a set up and launch time ofless than of the pylons. The bottle configuration (or shape) may sixty minutes by two trained operators, including off load, enable the thick regions ofthe pylon to be moved away from assembly, fueling, system checks, and start up. The opera- the thick region ofthe wing. When the wing has its proverse 20 tors may locally direct takeoff of the aircraft 100 then pressure gradient, the pylons may be shaped to have an transfer control to a remote location via satellite data link.

adverse pressure gradient and when the wing has its adverse During recovery the operators may receive control locally to pressure gradient, the pylons may be shaped to have a direct the landing, and landing and vehicle breakdown may proverse pressure gradient. take less than thirty minutes for two trained operators, FIG. 4 is a component block diagram illustrating a front 25 including shut down, drainage of fuel, disassemble, and view of the embodiment VTOL and cruise efficient aircraft loading of the aircraft 100.

100 in the wing born flight phase. In an embodiment, during In an embodiment, a payload of the aircraft 100 may be wing born flight, the propellers 142, 144, 146, 134, 177, 176, a science payload of twenty-five pounds, requiring five 175, and 179 may fold down and only the propellers 152 and hundred watts of power, and having a volume of 2500 cubic 178 may operate. 30 inches. The aircraft 100 may also carry a communications FIG. 5 is a component block diagram illustrating a left payload ofthirty five pounds and requiring two hundred and side view of the embodiment VTOL and cruise efficient seventy watts of power. In an embodiment, the aircraft 100 aircraft 100 in a VTOL flight phase. In the VTOL flight may have a small launch/recovery footprint defined by a phase the wing and horizontal tail sections may be tilted up, twenty foot by twenty foot box. The aircraft 100 may such as to 90 degrees. In an embodiment,the propellers 175, 35 provide landing accuracy and sensor placement within 1.5 176, 177, 178, and 179 (and their right side counterparts), meters of an intended location. The aircraft 100 may provide may all be driven by their respective motors in the VTOL for loiter missions and/or sensor placement missions. In an flight phase. In another embodiment, the propellers 175, embodiment, the aircraft 100 may be able to fly only on the 176, 177, and 179(and their right side counterparts) may be secondary power source of the electricity from the batteries driven by their respective motors in the VTOL flight phase, 40 during wing born flight for short periods of time in order to while propeller 178 (and its right side counterpart) may not fly quietly. In an embodiment, the aircraft may be able to be driven by their respective motors. In an embodiment, the climb to 100 feet before transitioning to wing born flight.

skids 156 and 158 and vertical tail surface 102c may be FIGS. 8-14 illustrate various views of an embodiment configured to support the aircraft 100 on the ground and the tri-rotor vehicle, such as tri-rotor aircraft 800. FIG. 8 is a outboard wing nacelles may be configured to act as outboard 45 component block diagram illustrating a top view of an landing skids. During VTOL flight, pitch may be controlled embodiment tri-rotor aircraft 800 including a front rotor 802 by the fore and/or aft propeller thrust modulation, roll may and two tail rotors 812. The tri-rotor aircraft 800 may be controlled by left and/or right propeller thrust modula- include a fixed wing 806, fuselage 807, and tail 810. The tion, and yaw may be controlled by counter clock wise and fixed wing 806 may include ailerons for controlling roll. The clock wise rotation of the various propellers and the flap- 50 front rotor 802 may be mounted at the front of the fuselage erons. In an embodiment, yaw may also be controlled by 807 on a hinged portion of the fuselage 807 that may house differential deflection of the flaperons. the motor 804 driving the front rotor 802. The motor 804 FIG. 6 is a component block diagram illustrating a left may be a fuel burning motor, such as a Cosworth engine, or side view of the embodiment VTOL and cruise efficient an electric engine. The two tail rotors 812 may be mounted aircraft 100 transitioning between the VTOL flight phase 55 on the tail 810. In addition to the engine 804, the fuselage and a wing born flight phase. During the transition between 807 of the tri-rotor aircraft 800 may house may include a VTOL flight and wing born flight the wing and horizontal payload 805, satellite communication system 808, fuel tank tail surfaces may tilt (for example tilt down to transition 813 for the engine 804, and camera turret 814 (shown in from VTOL flight to wing born flight and tilt up to transition FIG. 9A).

from wing born flight to VTOL flight). In an embodiment, 60 FIG. 9A is a component block diagram illustrating a the propellers 175, 176, 177, 178, and 179 (and their right front/left upper perspective view of the tri-rotor aircraft 800 side counterparts), may all be driven by their respective in the wing born flight configuration phase, and FIG. 9B is motors in the transition phase. In another embodiment, less a front/left upper perspective view of the tri-rotor aircraft than all the propellers may be driven during the transition. 800 in a VTOL flight configuration or phase. As illustrated Additionally, the landing skids 156 and 158 may retract. 65 in FIG.9A, during the wing born flight phase the front rotor FIG. 7 is a component block diagram illustrating a left 802 may be tilted down,and as illustrated in FIG.913, during side view of the embodiment VTOL and cruise efficient the VTOL flight phase the front rotor 802 may be tilted up.

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FIG. 10 is a component block diagram illustrating a front the front rotor 802 and engine 804 may tilt (for example tilt view of the tri-rotor aircraft 800. As illustrated in FIG. 10, down to transition from VTOL flight to wing born flight and the tail 810 may be a v-tail structure with a vertical tail tilt up to transition from wing born flight to VTOL flight). In extending down from the v-tail surfaces. The vertical section an embodiment, the front rotor 802 and tail rotors 812, may of the tail extending down from the v-tail surfaces may 5 all be driven by their respective motors in the transition include a rudder for controlling yaw. phase. In another embodiment, less than all the rotors may FIG. 11 is a component block diagram illustrating a be driven during the transition. Additionally, the landing rear/left upper perspective view of the tri-rotor aircraft 800. skids or other type landing gear may retract or extend.

The tail rotors 812 may be mounted on pylons extending FIG. 14 is a component block diagram illustrating a left from the v-tail surfaces of the tail 810. The pylons may io side view of the embodiment tri-rotor aircraft 800 in the house the motors driving the tail rotors 812, such as electric wing born flight phase. In the wing born flight phase, the motors or fuel burning engines. The tail rotors 812 may be hinged portion of the fuselage 807 with the front rotor 802 Samara type VTOL rotors which may be left exposed during and engine 804 may be tilted down such that the front rotor cruise (i.e., not stowed). The tail rotors 812 may, or may not, 802 axis may be oriented horizontally (e.g., parallel) along be pitch and/or RPM controllable rotors. The motors driving 15 the fuselage 807 and the front rotor 802 may act as a the tails rotors 812 and front rotor 802 can be a combination propeller, while the tail rotors 812 may be deactivated.

of electric motors and fuel burning engines. In various During wing born flight, pitch may be controlled by eleva- embodiments, the tail rotors 812 may tilt, for example, tors on the tail 810, roll may be controlled by the ailerons, forward, aft, starboard, port, and/or combinations of direc- and yaw may be controlled by the rudder on the tail 810.

tions. Tilting ofthe tail rotors 812 and/or the front rotor 802, 20 FIGS. 15-17 illustrate various views of another embodi- may change the orientation of the total sum force vector for ment tri-rotor vehicle, such as tri-rotor aircraft 1500. FIG.15 the aircraft 800. For example, the two tail rotors 812 may is a component block diagram illustrating a front/left upper vector in both the forward and aft direction and the starboard perspective view of aircraft 1500 in a wing born flight phase.

and port direction which may provide yaw control. This may Aircraft 1500 may include a front rotor 1502 and two tail enable a variety ofpotential flight configurations for forward 25 rotors 1506. The tri-rotor aircraft 1500 may include a fixed flight (i.e., wing born flight), including: 1) a forward flight wing 1503, fuselage 1504, and tail 1505. Similar to aircraft configuration in which the front rotor 802 is turned off, and 800 described above, in aircraft 1500 the front rotor 1502 not rotated down while the two aft rotors 812 are kept on and may be mounted at the front ofthe fuselage 1504 on a hinged rotated to a forward thrust position; 2) a forward flight portion of the fuselage 1504 that may house the motor configuration in which the front rotor 802 is rotated down 30 driving the front rotor 1502. The two tail rotors 1506 may be and kept on while the two aft rotors 812 are not rotated and mounted on the tail 1505. The aircraft 1500 may also include shut down; and 3)a forward flight configuration in which all landing gear 1507.

three rotors 802 and 812 are rotated into a forward facing In the wing born flight phase, the hinged portion of the position and kept on for forward flight (i.e., wing born fuselage 1504 with the front rotor 1502 and engine may be flight). 35 tilted down such that the front rotor 1502 axis may be FIG. 12 is a component block diagram illustrating a left oriented horizontally (e.g., parallel) along the fuselage 1504 side view ofthe tri-rotor aircraft 800 in a VTOL flight phase. and the front rotor 1502 may act as a propeller, while the tail In the VTOL flight phase, front rotor 802 and engine 804 rotors 1506 may be deactivated (e.g., allowed to weather- may be tilted up through a range of motion. The range of vane, oriented such that the long axis is aligned with the air motion may be any range of motion, such as less than 90 40 flow (e.g., via the use of the motor magnets, external degrees, 90 degrees, approximately 90 degrees, greater than magnets, or other fixtures), etc.). FIG. 16 is a component 90 degrees, etc. The range of motion of the front rotor 802 block diagram illustrating a front/left upper perspective view may be less than 90 degrees in various embodiments in of the tri-rotor aircraft 1500 in a VTOL flight phase. In the which the two tail rotors 812 may tilt forward and aft to VTOL flight phase,front rotor 1502 and engine may be tilted provide a total sum force vector in the vertical direction. In 45 up, such as to 90 degrees. In an embodiment, the front rotor an embodiment, the front rotor 802 and engine 804 may be 1502 and engine may be tilted up in a portion ofthe fuselage tilted up in a portion of the fuselage 807 on a hinged 1504 on a hinged structure controlled by an actuator 1508, structure controlled by an actuator 815, such as an extension such as an extension arm, etc., to tilt from horizontal to arm, etc., to tilt from horizontal to vertical positions such vertical positions such that the front rotor 1502 axis may be that the front rotor 802 axis may be oriented vertically (e.g., 50 oriented vertically (e.g., perpendicular)to the fuselage 1504.

perpendicular) to the fuselage 807. In an embodiment, the In an embodiment, the front rotor 1502 and tail rotors 1506 front rotor 802 and tail rotors 812 may all be driven by their may all be driven by their respective motors in the VTOL respective motors in the VTOL flight phase. In the VTOL flight phase. FIG. 17 is a component block diagram illus- flight phase, the tail rotors 812 may be activated. Roll trating a left side view of the tri-rotor aircraft 1500 in a control and/or pitch control in the VTOL phase may be 55 VTOL flight phase. In FIG. 17, the engine 1509 mounted in provided by speed control on the tail rotors 812.Yaw control a pylon of the tail 1505 to drive the left tail rotor 1506 is in the VTOL phase may be provided by speed control on the illustrated.

tail rotors 812, as well as the physical mounting of the tail FIGS. 18-20 illustrate various views of another embodi- rotors 812, for example with a 20 degree cant. In an ment tri-rotor vehicle, such as tri-rotor aircraft 1800. FIG.18 embodiment, the skids or other landing gear and the vertical 60 is a component block diagram illustrating a front/left upper surface of the tail 810 may be configured to support the perspective view of the tri-rotor aircraft 1800 in a VTOL aircraft 800 on the ground. flight phase, FIG. 19 is a component block diagram illus- FIG. 13 is a component block diagram illustrating a left trating a front/left upper perspective view oft the tri-rotor side view of the embodiment tri-rotor aircraft 800 transi- aircraft 1800 in a wing born flight phase, and FIG. 20 is a tioning between the VTOL flight phase and a wing born 65 component block diagram illustrating a top view of the flight phase. During the transition between VTOL flight and tri-rotor aircraft 1800 in a wing born flight phase. Aircraft wing born flight the hinged portion of the fuselage 807 with 1800 may include a front rotor 1802 and two tail rotors 1807.

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The tri-rotor aircraft 1800 may include a fixed wing 1801, rudder may move +/-10 degs. The same templates may be fuselage 1806, and tail 1808.In an embodiment,the wing of used for the horizontal and vertical tails. In order to make the aircraft 1800 may be a forward swept wing. In an embodi- vehicle easier to fly, elevator and rudder extensions may be ment, the tail rotors 1807 may be Samara type VTOL rotors. used. These extensions may be analogous to training wheels Similar to aircrafts 800 and 1500 described above,in aircraft 5 on a bike. These extensions may increase the elevator and 1800 the front rotor 1802 may be mounted at the front of the rudder chord by 0.25 ft. These extensions may be attached fuselage 1806 on a hinged portion 1803 ofthe fuselage 1806 to the elevators and rudders in a removable way or may be that may house the motor driving the front rotor 1802. The new elevators and rudders that may be swapped out with the two tail rotors 1807 may be mounted on the tail 1808. The proper size elevators and rudders. For hover flights, the aircraft 1800 may also include landing skids 1804 that may io bottom of the vertical tail may be one of the three landing be extended in the VTOL phase and retracted in the wing points along with the two front skids 1804. The bottom of born flight phase. In the VTOL flight phase,front rotor 1802 the vertical tail may be reinforced in order to protect the and engine may be tilted up, such as to 90 degrees. In an rudder when it is resting on the ground. These skids 1804 embodiment, the front rotor 1802 and engine may be tilted may retract inward and aft into slots in the fuselage 1806.

up in the hinged portion 1803 by an actuator, such as an 15 The aircraft 1800 may be at rest on the skids 1804 with extension arm, etc., to tilt from horizontal to vertical posi- waterline 0 of the fuselage 1806 parallel to the ground. The tions such that the front rotor 1802 axis may be oriented leading edge of the horizontal tail may be 4.22 ft aft of the vertically (e.g., perpendicular) to the fuselage 1806. In an front motor rotation point. The leading edge of the vertical embodiment, the front rotor 1802 and tail rotors 1807 may tail may be 4.02 ft aft of the front motor rotation point. This all be driven by their respective motors in the VTOL flight 20 aircraft 1800's configuration may be prone to have a center phase. of gravity too far aft. Removing excess weight from the tail In an embodiment, the center of gravity (CG) of the may adjust the center of gravity.

aircraft 1800 may be 1.53 ft aft of the front motor 1802 The preceding description of the disclosed embodiments rotation point. The CG range may be +/-0.05 ft. The weight is provided to enable any person skilled in the art to make ofthe aircraft 1800 may be 31 lbs. The wing loading may be 25 or use the present invention. Various modifications to these 4.7 lbs/ft2 and the disk loading may be 2.0 lbs/ft2. The stall embodiments will be readily apparent to those skilled in the speed may be approximately 60 ft/sec (35 kts), and the art, and the generic principles defined herein may be applied aircraft 1800 may cruise at approximately 75 ft/sec (44 kts). to other embodiments without departing from the spirit or The lift to drag ratio (L/D)should approximately be 16. The scope of the invention. Thus, the present invention is not fuselage 1806 may be constructed to two primary segments. 30 intended to be limited to the embodiments shown herein but The forward fuselage may be the hinged portion 1803 that is to be accorded the widest scope consistent with the rotates with the front rotor 1802, while the main portion of following claims and the principles and novel features the fuselage 1806 remains stationary. Fuselage 1802 length, disclosed herein.

from tip of spinner to tip of tail cone, may be 5.59 ft. The main fuselage 1802 may have a cutout for the wing carry 35 What is claimed is: through. The cutout may be shaped to hold the wing at a 6 1. A tri-rotor vehicle, comprising: degree incidence angle. The construct ofthe wing 1801 may a wing having no rotors coupled thereto; be with a 3 degree twist (i.e. the wing tips are at a 3 degree a tail comprising two horizontal tail sections; trailing edge up than the wing root). There may also be 0 a fuselage; degrees of dihedral in the wing 1801. There may be -5 deg 40 two tail rotors coupled to the tail, wherein the two of sweep at the 25% chord location (leading edge of tip horizontal tail sections extend horizontally relative to airfoil may be 0.3005 feet forward of leading edge of root the fuselage and from opposite sides of the fuselage, airfoil). Thus, the reference area may equal 6.54 ft2 ,the half wherein each of the two tail rotors has a single corre- span may be 4.955 ft, the wing carry over span may be 0.35 sponding respective horizontal tail section, and wherein ft, the flap span may be 2.3025 ft, the aileron span may be 45 each of the two tail rotors is coupled only to its own 2.3025 ft, the root chord may be 0.85 ft, the tip chord may respective one of the two horizontal tail sections and is be 0.4406 ft, and the wing carry through chord may be 0.55 configured to tilt through a range of motion; and ft. The wing carry over may use the same root airfoil, but cut a front rotor coupled to the fuselage, wherein the front away 0.3 ftfrom the trailing edge. Flaps and ailerons may be rotor is configured to tilt through a range of motion and incorporated into the wing 1801. The flaps and ailerons may 50 the vehicle is configured to transition between a wing be 15% of the local chord length. In order to prevent the born flight phase and a VTOL flight phase by the front need for custom high torque servos, the flap may be installed rotor tilting through the range of motion, and wherein separate from the aileron with independent servos. This may during the wing born flight phase the front rotor is tilted also give the ability to program differential flaperons (e.g., up and is deactivated while the two tail rotors are use 4 channels (1 for left aileron, 1 for left flap, 1 for right 55 activated and tilted forward.

flap and 1 for right aileron). The leading edge of the wing 2. The tri-rotor vehicle of claim 1, root may be 1.47 ft aft of the front motor rotation point. wherein the front rotor is coupled to a front hinged portion The tail 1808 may be constructed with 0 twist, 0 dihedral, of the fuselage controlled by an actuator to tilt through and un-tapered. The chord length of both the horizontal and the range of motion.

vertical portions ofthe tail 1808 may be 0.55 ft. The span of 60 3. The tri-rotor vehicle of claim 1, wherein the two tail the horizontal tail may be 2.1 ft. Note this span does not rotors are coupled to the tail such that rotor axes of each of include the pods that fair over the rear lift motors. The span the two tail rotors are configured to orient vertically relative of the vertical tail may be 1.85 ft. The elevators and rudders to the fuselage during the VTOL flight phase.

may be 50% of the chord length. The Elevator may need to 4. The tri-rotor vehicle of claim 3, wherein the front rotor move through +10 to -90 degrees. Note + is trailing edge up. 65 and two tail rotors are not pitch controlled rotors.

For hover the elevator may need to be -90 degs. For forward 5. The tri-rotor vehicle of claim 4, wherein the two tail flight the elevator may need to move to +/-10 degs. The rotors are coupled to the tail at a canted angle.

US 10,071,801 B2

17 18

6. The tri-rotor vehicle of claim 3, wherein the tail is a 15. A tri-rotor vehicle, comprising: v-tail.

a wing having no rotors coupled thereto; 7. The tri-rotor vehicle of claim 3, wherein the wing is a tail comprising two horizontal tail sections; swept.

5 a fuselage; 8. The tri-rotor vehicle of claim 3, wherein the vehicle is an unmanned aerial vehicle. two tail rotors coupled to the tail, wherein the two 9. The tri-rotor vehicle of claim 3, further comprising horizontal tail sections extend horizontally relative to retractable landing skids, wherein the tail is configured to act the fuselage and from opposite sides of the fuselage, as a rear landing skid. wherein each of the two tail rotors has a single corre- 10. The tri-rotor vehicle of claim 1, wherein the two tail lo sponding respective horizontal tail section, and wherein rotors are Samara VTOL rotors. each of the two tail rotors is coupled only to its own 11. The tri-rotor vehicle ofclaim 1, wherein the front rotor respective one of the two horizontal tail sections; and and two tail rotors are cyclic and collective controlled rotors.

a front rotor coupled to a front hinged portion of the 12. The tri-rotor vehicle of claim 11, further comprising a fuselage controlled by an actuator, wherein the front front rotor motor configured to directly drive the front rotor 15 rotor is configured to tilt through a range of motion by and two tail rotor motors, each tail rotor motor configured to control of the actuator and wherein the vehicle is drive a respective one of the tail rotors, wherein the front configured to transition between a wing born flight rotor motor is a fuel burning engine and each of the two tail phase and a VTOL flight phase by the front rotor tilting rotor motors is selected from the group consisting of a fuel through the range of motion; and burning engine and an electric motor. 20 a front rotor motor configured to drive the front rotor and 13. The tri-rotor vehicle of claim 1, wherein two tail rotor motors, each tail rotor motor configured the two tail rotors are coupled to the tail such that the two to drive a respective one of the tail rotors, wherein the tail rotors are configured to tilt forward, aft, starboard, front rotor motor is selected from the group consisting and port.

of a fuel burning engine and an electric motor and each 14. A tri-rotor vehicle, comprising: 25 of the two tail rotor motors is selected from the group a wing having no rotors coupled thereto; consisting of a fuel burning engine and an electric a tail comprising two horizontal tail sections; motor, a fuselage; wherein: two tail rotors coupled to the tail, wherein the two horizontal tail sections extend horizontally relative to 30 the two tail rotors are coupled to the tail such that rotor the fuselage and from opposite sides ofthe fuselage and axes of each of the two tail rotors are activated and wherein each ofthe two tail rotors is coupled to its own configured to orient horizontally relative to the fuse- respective one of the two horizontal tail sections; and lage during the wing born flight phase; a front rotor coupled to the fuselage, wherein the front the front rotor is deactivated and configured to orient rotor is configured to tilt through a range of motion; and 35 vertically relative to the fuselage during the wing wherein the two tail rotors are configured to be stowed in born flight phase; and pods on the tail during a wing born flight phase and are the front rotor and two tail rotors are cyclic and held in place by one or more magnets such that a long collective controlled rotors.

axis ofeach ofthe two tail rotors is aligned with airflow over the vehicle.