Vertical Takeoff and Landing Vehicle with Increased Cruise Efficiency

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(12) United States Patent (io) Patent No.:

US 9,896,200 B2

(45) Date of Patent:

Fredericks et al. *Feb. 20,2018

(54) VERTICAL TAKEOFF AND LANDING (51) Int. Cl.

B64C 29/00 (2006.01) VEHICLE WITH INCREASED CRUISE B64C 39/00 (2006.01) EFFICIENCY (Continued) (71) Applicant: The United States of America as (52) U.S. Cl.

represented by the Administrator of CPC .......... B64C 29/0033 (2013.01); B64C 3/385 the National Aeronautics and Space (2013.01); B64C 3/40 (2013.01); Administration, Washington, DC(US) (Continued) (72) Inventors: William J. Fredericks, Williamsburg, (58) Field of Classification Search VA (US); Mark D. Moore, CPC ............ B64C 29/0033; B64C 29/0075; B64C Williamsburg, VA (US); Ronald C.

29/0083; B64C 39/003; B64C 39/005; Busan, Newport News, VA (US); Paul (Continued) M. Rothhaar, Yorktown, VA (US); (56) References Cited David D. North, Williamsburg, VA (US); William M. Langford, Hampton, U.S. PATENT DOCUMENTS VA (US); Christopher T. Laws, Yorktown, VA (US); William T.

7,131,613 132 * 11/2006 Kelly ........................ B64B 1/20 Hodges, Yorktown, VA (US); Zachary 244/127 8,733,690 132 * 5/2014 Bevirt ................. B64C 29/0033 R. Johns, Virginia Beach, VA (US); 244/12.4 Sandy R. Webb, Hampton, VA (US) * cited by examiner (73) Assignee: THE UNITED STATES OF Primary Examiner Richard R Green AMERICA AS REPRESENTED BY (74) Attorney, Agent, or Firm Andrea Z. Warmbier; THE ADMINISTRATOR OF NASA, Robin W. Edwards; Mark P. Dvorscak Washington, DC (US) (57) ABSTRACT (*) Notice: Subject to any disclaimer, the term ofthis Systems, methods, and devices are provided that combine an patent is extended or adjusted under 35 advance vehicle configuration, such as an advanced aircraft U.S.C. 154(b) by 0 days.

configuration, with the infusion of electric propulsion, This patent is subject to a terminal dis- thereby enabling a four times increase in range and endur- claimer.

ance while maintaining a full vertical takeoff and landing ("VTOL") and hover capability for the vehicle. Embodi- (21) Appl. No.: 15/332,391 ments may provide vehicles with both VTOL and cruise (22) Filed: Oct. 24, 2016 efficient capabilities without the use of ground infrastruc- (65) Prior Publication Data ture. An embodiment vehicle may comprise a wing config- ured to tilt through a range of motion, a first series ofelectric US 2017/0057631 Al Mar. 2, 2017 motors coupled to the wing and each configured to drive an associated wing propeller, a tail configured to tilt through the Related U.S. Application Data range of motion, a second series of electric motors coupled to the tail and each configured to drive an associated tail (63) Continuation of application No. 14/121,001, filed on propeller, and an electric propulsion system connected to the Aug. 13, 2014, now Pat. No. 9,475,579.

first series ofelectric motors and the second series ofelectric motors.

(60) Provisional application No. 61/865,347,filed on Aug.

13, 2013. 20 Claims, 7 Drawing Sheets

US 9,896,200 B2

Page 2 (51) Int. Cl.

B64C 11/28 (2006.01) B64C 25/52 (2006.01) B64D 27/24 (2006.01) B64C 3/40 (2006.01) B64C 9/14 (2006.01) B64D 27/26 (2006.01) B64C 11/50 (2006.01) B64C 25/32 (2006.01) B64C 3/38 (2006.01) B64C 39/02 (2006.01) B64C 5/02 (2006.01) B64D 27102 (2006.01) (52) U.S. Cl.

CPC .................. B64C 5/02 (2013.01); B64C 9/14 (2013.01); B64C 11/28 (2013.01); B64C 11/50 (2013.01); B64C 25/32 (2013.01); B64C 25/52 (2013.01); B64C 39/024 (2013.01); B64D 27/24 (2013.01); B64D 27/26 (2013.01); B64C 22011021 (2013.01); B64C 22011042 (2013.01); B64C 22011044 (2013.01); B64C 22011088 (2013.01); B64C 22011104 (2013.01); B64C 22011108 (2013.01); B64C 22011165 (2013.01); B64D 20271026 (2013.01); Y02T 50/44 (2013.01); Y02T 50/64 (2013.01); YIOS 9031903 (2013.01) (58) Field of Classification Search CPC ......... B64C 39/08; B64C 3/385; B64C 11/28; B64C 25/52; B64C 2201/042; B64C 2201/088; B64D 27/24 See application file for complete search history.

Sheet 1 of 7 U.S. Patent Feb. 20,2018 US 9,896,200 B2

Sheet 2 of 7 U.S. Patent Feb. 20,2018 US 9,896,200 B2 I1 5, t

Sheet 3 of 7 U.S. Patent Feb. 20,2018 US 9,896,200 B2

Sheet 4 of 7 B2 U.S. Patent Feb. 20,2018 US 9,896,200

Sheet 5 of 7 B2 U.S. Patent Feb. 20,2018 US 9,896,200 c~z

Sheet 6 of 7 U.S. Patent Feb. 20,2018 US 9,896,200 B2

Sheet 7 of 7 U.S. Patent Feb. 20,2018 US 9,896,200 B2

US 9,896,200 B2

VERTICAL TAKEOFF AND LANDING motors, and one or more batteries connected to the first VEHICLE WITH INCREASED CRUISE series of electric motors and the second series of electric EFFICIENCY motors.

These and other features, advantages, and objects of the CROSS-REFERENCE TO RELATED PATENT 5 present invention will be further understood and appreciated APPLICATIONS by those skilled in the art by reference to the following specification, claims, and appended drawings.

This patent application is a continuation of U.S. patent BRIEF DESCRIPTION OF THE SEVERAL application Ser. No. 14/121,001, filed Aug. 13, 2014, which io VIEWS OF THE DRAWINGS claims the benefit of and priority to U.S. Provisional Patent Application No. 61/865,347, filed on Aug. 13, 2013. The The accompanying drawings, which are incorporated contents of each of the foregoing applications are hereby herein and constitute part of this specification, illustrate incorporated by reference in their entireties.

exemplary embodiments of the invention, and together with the general description given above and the detailed descrip- STATEMENT REGARDING FEDERALLY tion given below, serve to explain the features of the SPONSORED RESEARCH OR DEVELOPMENT invention.

FIG.1 is a front/left upper perspective view ofan embodi- The invention described herein was made in part by ment VTOL and cruise efficient aircraft.

employees of the United States Government and may be FIG. 2 is a front/right lower perspective view of the manufactured and used by or for the Government of the embodiment VTOL and cruise efficient aircraft.

United States ofAmerica for governmental purposes without FIG. 3 is a top view of an embodiment of a pylon for the the payment of any royalties thereon or therefore.

present invention.

FIG. 4 is a front view of the embodiment VTOL and BACKGROUND OF THE INVENTION 25 cruise efficient aircraft.

FIG. 5 is a left side view of the embodiment VTOL and Vertical takeoff and landing ("VTOL") and cruise effi- cruise efficient aircraft in a VTOL flight phase.

ciency are diametrically opposed requirements for aircraft.

FIG. 6 is a left side view of the embodiment VTOL and There are system solutions today that require ground infra- cruise efficient aircraft transitioning between the VTOL structure, namely catapults and arresting equipment, to flight phase and a wing born flight phase.

launch and recover cruise efficient aircraft, thereby impart- FIG. 7 is a left side view of the embodiment VTOL and cruise efficient aircraft in the wing born flight phase.

ing these aircraft with VTOL like capabilities. These current multi-part systems remove the need for the actual aircraft to DETAILED DESCRIPTION OF THE perform VTOL,but the system as a whole (i.e., aircraft plus 35 INVENTION ground infrastructure) becomes a VTOL system. With these current systems it is not possible to meet both VTOL and For purposes of description herein, it is to be understood cruise efficiency requirements without the use of ground that the specific devices and processes illustrated in the infrastructure.

attached drawings, and described in the following specifi- 40 cation, are simply exemplary embodiments of the inventive BRIEF SUMMARY OF THE INVENTION concepts defined in the appended claims. Hence, specific dimensions and other physical characteristics relating to the The systems, methods, and devices of the present inven- embodiments disclosed herein are not to be considered as tion combine an advanced vehicle configuration, such as an limiting, unless the claims expressly state otherwise.

advanced aircraft configuration, with the infusion of electric 45 The word "exemplary"is used herein to mean "serving as propulsion, thereby enabling a four times increase in range an example, instance, or illustration." Any implementation and endurance while maintaining a full vertical takeoff and described herein as "exemplary" is not necessarily to be landing ("VTOL") and hover capability for the vehicle. In construed as preferred or advantageous over other imple- this manner, various embodiments may provide vehicles, mentations.

such as aircraft, with both VTOL and cruise efficient capa- 50 The various embodiments will be described in detail with bilities that may meet VTOL and cruise efficiency require- reference to the accompanying drawings. Wherever pos- ments without the use of ground infrastructure. The various sible, the same reference numbers will be used throughout embodiments may provide a VTOL and cruise efficient the drawings to refer to the same or like parts. References vehicle, such as an aircraft, comprising a wing configured to made to particular examples and implementations are for tilt through a range of motion, a first series ofelectric motors 55 illustrative purposes, and are not intended to limit the scope coupled to the wing and each configured to drive an asso- of the invention or the claims.

ciated wing propeller, a tail configured to tilt through the Electric propulsion may enable radical new vehicle con- range of motion, a second series of electric motors coupled cepts and configurations, particularly for vertical takeoff and to the tail and each configured to drive an associated tail landing ("VTOL") aircraft because electric propulsion may propeller, and an electric propulsion system connected to the 6o address the significant mismatch between takeoff and cruise first series of electric motors and the second series ofelectric power conditions experienced by VTOL aircraft. The ability motors. In a further embodiment, the electric propulsion to distribute the thrust across the airframe, without mechani- system may be a battery augmented series hybrid electric cal complexity and with a scale free propulsion system, may propulsion system comprising one or more internal com- provide a new degree of freedom for aircraft designers.

bustion engines, one or more generators coupled to the one 65 The various embodiment vehicle configurations may or more internal combustion engines and connected to the combine an advanced vehicle configuration, such as an first series of electric motors and the second series ofelectric advanced aircraft configuration, with the infusion of electric

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propulsion, thereby enabling a four times increase in range wing of the aircraft and the leading edge of the tail of the and endurance while maintaining a full VTOL and hover aircraft may vary. For example, in an embodiment in which capability (similar to the VTOL and hover capabilities of a the aircraft may have ten propellers, eight propellers may be helicopter)for the vehicle. A "full VTOL" may be defined as mounted to the leading edge of the wing and two propellers taking off or landing the vehicle vertically without requiring 5 may be mounted to the leading edge ofthe tail ofthe aircraft.

a rolling takeoff or landing, or any horizontal movement. In In an embodiment, at least a portion of the wing of the this manner, various embodiments may provide vehicles, aircraft and at least a portion of the tail of the aircraft may such as aircraft, with both VTOL and cruise efficient capa- both tilt to transition the aircraft between hovering flight and bilities that may meet VTOL and cruise efficiency require- wing born flight. In an embodiment, the wing of the aircraft ments without the use of ground infrastructure. Cruise 10 and the tail of the aircraft may both rotate around the lateral efficient vehicles, such as cruise efficient aircraft, may axis ofthe wing and tail, respectively, to tilt the wing and tail provide various efficiencies based on the vehicle mission, through a range of motion,thereby pitching the wing and tail such as reduced energy consumption during flight, long up and/or down relative to the longitudinal axis of the range, and/or long endurance. The various embodiments 15 aircraft to transition the aircraft between hovering flight(i.e., may also provide the ability to achieve low disc-loading for the VTOL phase) and wing born flight (i.e., the wing born low ground impingement velocities, low noise, and/or hover flight phase). The range of motion may be any range of power reduction/minimization which may reduce energy motion, such as less than 90 degrees, 90 degrees, approxi- consumption in a VTOL phase of flight.

mately 90 degrees, greater than 90 degrees, etc. The tilting The systems, methods, and devices ofthe various embodi- 20 portions of the wing ofthe aircraft and the tail of the aircraft ments may provide a VTOL and cruise efficient vehicle, such as an aircraft, comprising a wing configured to tilt may tilt together or independently and may tilt to the same through a range of motion, a first series of electric motors or different orientations in their respective ranges of motion.

coupled to the wing and each configured to drive an asso- In an embodiment, an aircraft may include a semi-tandem ciated wing propeller, a tail configured to tilt through the wing configuration. The semi-tandem wing configuration range of motion, a second series of electric motors coupled 25 may provide a compromise between a tandem wing con- to the tail and each configured to drive an associated tail figuration, which carries half the lift on the tail, and a propeller, and an electric propulsion system connected to the conventional wing configuration, which carries no lift on the first series of electric motors and the second series ofelectric tail. The center of gravity of the embodiment aircraft with motors. In a further embodiment, the electric propulsion the semi-tandem wing configuration may be located aft of system may be a battery augmented series hybrid electric 30 the wing. The embodiment semi-tandem wing configuration propulsion system comprising one or more internal com- may cause some lift to be carried on the tail of the aircraft, bustion engines, one or more generators coupled to the one which may allow the propellers on the tail to carry some the or more internal combustion engines and connected to the aircraft's weight during a hover in the VTOL flight phase.

first series of electric motors and the second series ofelectric For example, the tail may carry less than fifty percent of the motors, and one or more batteries connected to the first 35 lift. However, the wing may carry most ofthe lift of aircraft.

series of electric motors and the second series of electric The embodiment semi-tandem wing configuration may motors. enable the wing to be proportionally larger than the tail and Electric propulsion may be scale-free in terms of being achieve a greater span in order to reduce induced drag. In an able to achieve highly similar levels of motor power to embodiment, the aircraft may be designed such that the weight and efficiency across a dramatic scaling range. Using 40 center of gravity location is selected to have the propellers distributed electric propulsion may enable the various on the wing carry a higher percent of the aircraft's weight embodiment advanced aircraft configurations to achieve than the propellers on the tail. In this manner, the propellers improvements in aerodynamic efficiency that may be on the tail may provide greater pitch control authority and approximately four times that of conventional helicopter reduce induced drag ofthe tail by reducing the amount oflift configurations. Helicopters typically achieve a lift to drag 45 that may be required to be carried on the tail. The embodi- ratio (L/D) of between 4 and 5, while the various embodi- ment semi-tandem wing configuration with a lifting tail may ment VTOL aircraft may achieve an L/D of approximately be statically stable in the wing born flight phase (i.e., 20. The various embodiments provide the ability to elimi- forward flight). In an embodiment, the aircraft may be nate the problem of advancing and retreating rotor blades by designed such that the lift coefficient, tail loading, and lift converting into wing born flight without the mechanical 50 curve slope of the tail may be less than the lift coefficient, complexity of previous VTOL aircraft. wing loading, and lift curve slope of the wing. In an The various embodiments may utilize hybrid electric embodiment, the aircraft may include a swept wing to shift propulsion to normalize the power across the mission phases the aerodynamic center of the wing aft in forward flight and and to enable the combustion engine to be sized for wing still keep the center ofthrustforward in hovering flight when born flight and batteries may be used to supplement the 55 the wing is rotated up 90 degrees. In an embodiment, the power required in hover. This may yield an overall lighter sweep of the wing may enable a reduction in the induced propulsion system, which may make for a smaller aircraft, drag ofthe aircraft. During a hover, propeller thrust needs to which may lead to lower cost. be distributed about the center of gravity of the aircraft.

In an embodiment, an aircraft may have one or more Without a swept wing, in forward flight the wing stays in propellers, such as one, two, three, four, five, six, seven, 60 front of the center of gravity resulting in only about eighty eight, nine, or ten or more propellers, and one or more percent ofthe lift on the wing and twenty percent on the tail.

electric motors may distribute thrust across the propellers. However, in an embodiment with a swept wing, in a hover, For example, the electric motors may distribute thrust across the propellers are forward of the wing, but in forward flight ten propellers. In an embodiment, propellers may be the wing center is farther aft enabling ninety two percent of mounted to the leading edge of the wing of the aircraft and 65 the lift to be on the wing and eight percent to be on the tail.

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

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In an embodiment, forward flight propellers may be primary electrical source comprised of generators driven by located at the wing tips of the aircraft. The wing tip forward internal combustion engines. A second electrical source may flight propellers may provide a destructive interference be battery packs. In an embodiment, the internal combustion between the propeller swirl and the wing tip vortex. The engines may be sized to meet the power requirements during resulting interference may be viewed as an induced drag 5 the wing born flight phase, but the power required in the reduction or a propulsive efficiency increase. In an embodi- VTOL flight phase and during transition may be greater than ment, the forward flight propellers may run for the entire the power required in the wing born flight phase. The battery mission (i.e., both during the VTOL flight phase and the packs may be sized to make up for the difference between wing born flight phase). In an embodiment, the forward the power required in the VTOL flight phase and during flight propellers may run only during the wing born flight io transition and the power the internal combustion engines phase. In an embodiment, the forward flight propellers may may provided by turning the alternators. This embodiment be variable speed (e.g., variable revolutions per minute configuration may support the minimum propulsion system ("RPM")) and/or variable pitch propellers. The use of vari- weight(as opposed to sizing the internal combustion engines able speed and/or pitch propellers may maximize propulsive for power required for VTOL flight) for missions where the efficiency. 15 time spent in hover may be a small percent of the time spent In an embodiment, vertical flight propellers may fold in wing born flight. The embodiment series hybrid propul- down during the wing born flight phase. In an embodiment, sion system may effectively act as an "electric driveshaft" the vertical flight propellers may fold into conformal and an "electric gearbox" eliminating the driveshafts and recesses of the motor pylons. The folding of the vertical gear boxes necessary to distribute power to each propeller in flight propellers, especially into conformal recesses, may 20 reduce drag in the wing born flight phase when compared to previous aircraft by filling the same function. In an embodi- leaving the vertical flight propellers deployed.In an embodi- ment, in hovering flight the internal combustion engines ment, the vertical flight props may extend aft of the leading may turn generators, and the electrical power from the edge ofthe wing and/or tail when folded. In an embodiment, generators may be feed to a controller that outputs uniform to prevent the vertical flight propellers from contacting the 25 direct current ("DC") power. The DC power may be dis- leading edge of the wing as the vertical flight propellers are tributed via wires throughout the aircraft. The DC power started, the vertical flight propeller blades may ride along a may be provided to a motor controller associated with each sinusoidal cam to push the blades forward enough to avoid motor which may convert the DC power to alternating contact with the leading edge of the wing and/or tail. current ("AC") power to drive the AC motors turning the In an embodiment, the propellers may be synchronized 30 propellers. The advantage of converting the AC output ofthe electronically to hold a specific phase angle to provide generators to DC power and the converting the DC power to destructive interference of each propeller's noise. This may AC power at each motor may be that the motor controller for result in a quieter aircraft as a whole relative to the sound each motor may independently drive its associated motor generated by each propeller in isolation. In an embodiment, allowing the RPM to be varied on a per motor basis. The use each successive propeller may rotate in an alternate direction 35 of two controllers may result in some power loss due to the to prevent the wake of one propeller blade impacting the inefficiency of the controllers. In an embodiment, in wing wake of the adjoining propeller blade. In this manner, the born flight the internal combustion engines may turn the wakes of the propellers may pass in the same direction as generators and the AC power output by the generators may opposed to colliding head-on. be provided via wires directly to the motors without using In an embodiment, the aircraft may include reflexed 40 intermediate controllers, thereby operating the generators flaperons. The use ofreflexed flaperons may delay the onset and motors in a synchronous mode. This may avoid con- of stall on the wing during transition between the VTOL troller loss. The RPM of the generator may need to be equal flight phase and the wing born flight phase. As discussed to the RPM of the motor being driven or if the pole count of herein,"flaperons" refers to any control surface used as both the generator is different than the pole count ofthe motor,the ailerons and flaps. By having reflexed (i.e., trailing edge up) 45 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.

around the airfoil allowing the airfoil to go to a higher angle In an embodiment, the use of electric motors to drive the of attack before airflow separates. propellers may provide an aircraft with a propulsion system In an embodiment, when the tail is tilted vertically in the that has no single point of failure. The use of multiple VTOL flight phase, the vertical tail may serve a second role 50 electric motors may enable the failure of one motor to occur as a rear landing skid. In an embodiment, the wing tip motor and the aircraft to still fly. Because electric motors may put pylons may serve as outboard landing skids, thereby giving out more power by turning at a higher RPM,in the event of the aircraft a wide stance on the ground to reduce tip over a motor failure, other propellers, as required, may be turned risk at landing. at a higher RPM by their respective motors ensuring the In an embodiment, the outboard portion of the horizontal 55 aircraft may still be flyable. The increase of RPM may put tail may be configured in a dihedral angle to provide out more thrust per remaining propeller (meaning also more directional stability during the slow speed portion of the noise), but the aircraft may remain flyable.

transition corridor between the VTOL flight phase and the In an embodiment, the propellers of the aircraft may turn wing born flight phase. at a low tip speed, enabling the aircraft to achieve a very low In an embodiment, an aircraft may utilize a battery 60 noise profile.

augmented series hybrid electric propulsion system. This Unique wind tunnel testing that combines a nested face- use of a battery augmented series hybrid electric propulsion centered design of experiments ("DOE") with optimal system may reduce propulsion system weight and enable design points to achieve testing efficiency and statistically unconventional configurations. In an embodiment, all pro- sound mathematical models were developed. This method- pellers may be turned by electric motors. In an embodiment, 65 ology required new tools and specialized tunnel software to electrical power to operate each motor may be provided execute the experiment, such as allowing randomized set from one or both of two sources. A first source may be a points, as well as substantial automation of both the wind

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tunnel model and test facility. The new methodology sources 210 and 212 may be connected via wires and various reduced testing time by over sixty years. controllers (not shown) to each of the electric motors and The applications for the various embodiment aircraft that may provide power to drive the propellers. In an embodi- may take off and land vertically and yet fly for a long ment, batteries may be housed in each nacelle, such as duration and range are numerous. Applications may range 5 batteries 214, 216, 218, 220, and 222 and their mirrored from military reconnaissance missions, to police and fire counterparts on the opposite side wing section 101b and department surveillance roles, to civilian automated door to horizontal tail section 102b. These batteries may also be door package delivery (e.g., mail, prescription drugs, food, connected to the electric motors via wires and various etc.), to air taxi services. controllers (not shown)and may provide power to drive the FIGS. 1-6 illustrate various views of an embodiment io propellers. Together the primary power sources 210 and 212 VTOL and cruise efficient vehicle, such as aircraft 100. FIG. and various batteries may comprise a battery augmented 1 illustrates the front/left upper perspective view of the series hybrid electric propulsion system for the aircraft 100.

embodiment aircraft 100 with the wing (comprised of wing The aircraft 100 may include a satellite communication sections 101a and 101b) and horizontal tail sections 102a system comprised of various modules 204 and 208, and the and 102b (comprising the tilting portions of the overall tail 15 aircraft may carrier a payload 202. As illustrated in FIG. 2, comprised of tiltable horizontal tail sections 102a and 102b the skids 156 and 158 may retract up to the fuselage 160 and vertical tail section 102c which remains fixed) in the during wing born flight.

wing born flight phase configuration (i.e., tilted down par- In an embodiment, the airfoil may be a custom designed allel to the longitudinal axis of the fuselage 160). In an shape to be a tradeoff between low drag at high lift coeffi- embodiment, the aircraft 100 may include four engine 20 cients, ease of wing fabrication, and gradual stall character- nacelles on each wing section 102a and 102b and one engine istics. In an embodiment, motor pylons may be shaped to nacelle on each tail horizontal tail section 102a and 102b. minimize drag at high lift coeflicients. Normally, when The engine nacelles may be comprised of pairings of pylons mounting pylons or nacelles at the leading edges of the 103, 104, 105, 106, 107, 108, 109, 124, 132, and 133 and wings, the pylons or nacelles mature the boundary layer and respective fairings 110, 111, 112, 113, 114, 115, 116, 117, 25 cause the airflow over the wing to separate early leading to 130, and 131. In an embodiment, each of the pylons 103, a loss of lift and an increase in drag. In an embodiment, the 104, 105, 106, 107, 108, 109, 124, 132, and 133 may have area of the cross section of the pylons may vary from the same outside mold line ("OML") while each of the forward to aft. As an example shown in FIG. 3, the pylons fairings 110, 111, 112, 113, 114, 115, 116, 117, 130, and 131 of the various embodiments may have a bottle-type con- may have its own OML. Electric motors may be coupled to 30 figuration (or shape) where the cross sectional area may be each pylon 103, 104, 105, 106, 107, 108, 109, 124, 132, and comparatively less in a middle portion A of the pylon than 133 to drive a propeller associated with each nacelle. Pylons in a forward or aft sections ofthe pylon which may minimize 108, 106, 104, 124, 132, 103, 105, 107, 109, and 133 are the super velocity around the pylon. As shown in FIG. 3, in illustrated with their respective electric motors 138, 140, one embodiment, the middle portion A is substantially 146, 150, 136, 171, 172, 173, 174, and 180 as well as their 35 hour-glass shaped, thus reducing the drag between the wing respective propellers 152,142, 144,148, 134, 175,176, 177, and the pylon. The bottle configuration (or shape) of the 178, and 179. In an embodiment, propellers 152, 134, 178, pylons may reduce the drag due to interaction with the wing.

and 179 may be variable pitch propellers and propellers 142, The airflow must accelerate to move around the thick 144, 148, 175, 176, and 177 may be fixed pitch propellers. regions, and it may be desirable to not have the thick region In an embodiment, propellers 142, 144, 148, 175, 176, and 40 of the wing in the same place as the thick region of the 177 may fold down when not in use, such as during wing pylons. The bottle configuration (or shape) may enable the born flight. Propellers 152, 134, 142, 144, 148, 178, 179, thick regions of the pylon to be moved away from the thick 175, 176, and 177 may have any number of blades, such as region ofthe wing. When the wing has its proverse pressure two blades, three blades, etc. In an embodiment, the aircraft gradient, the pylons may be shaped to have an adverse 100 may include flaperons 118, 119, 120, 121, 122, and 123 45 pressure gradient and when the wing has its adverse pressure on the wing and flaperons 126 and 127 on the tail. The gradient, the pylons may be shaped to have a proverse flaperons 118, 119, 120, 121, 122, and 123 may be disposed pressure gradient.

on the trailing edge ofthe wing between successive nacelles. FIG. 4 illustrates a front view of the embodiment VTOL The flaperons 126 and 127 may be disposed on the trailing and cruise efficient aircraft 100 in the wing born flight phase.

edge of the tail inboard of the tail mounted nacelles. The 50 In an embodiment, during wing born flight, the propellers aircraft 100 may also include a vertical control surface on 142, 144, 146, 134, 236, 302, 234, and 230 may fold down the vertical tail section 102c, such as a rudder 125. The and only the propellers 152 and 224 may operate.

aircraft 100 may include a camera 154 extending from the FIG. 5 illustrates a left side view of the embodiment fuselage 160. In an embodiment, the aircraft 100 may VTOL and cruise efficient aircraft 100 in a VTOL flight include landing gear, such as retractable nose skids 156 and 55 phase. In the VTOL flight phase the wing and horizontal tail 158. sections may be tilted up, such as to 90 degrees. In an FIG. 2 illustrates a front/right lower perspective view of embodiment,the propellers 175, 176, 177, 178, and 179(and the embodiment VTOL and cruise efficient aircraft 100 their right side counterparts), may all be driven by their shown with a cutaway view of the fuselage 160. In FIG. 2 respective motors in the VTOL flight phase. In another the aircraft 100 may be configured for the wing born flight 60 embodiment, the propellers 175, 176, 177, and 179 (and phase with propellers 142,144,148, 176, 177, 134, and 179 their right side counterparts) may be driven by their respec- folded back against their respective pylons. In an embodi- tive motors in the VTOL flight phase, while propeller 178 ment, two primary power sources 210 and 212 may be (and its right side counterpart) may not be driven by their comprised ofinternal combustion engines, such as two eight respective motors. In an embodiment, the skids 156 and 158 horse power diesel engines, coupled to two generators. The 65 and vertical tail surface 102c may be configured to support fuselage 160 may include a fuel tank 106 storing fuel for the the aircraft 100 on the ground and the outboard wing primary power sources 210 and 212. The primary power nacelles may be configured to act as outboard landing skids.

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During VTOL flight, pitch may be controlled by the fore embodiments will be readily apparent to those skilled in the and/or aft propeller thrust modulation, roll may be con- art, and the generic principles defined herein may be applied trolled by left and/or right propeller thrust modulation, and to other embodiments without departing from the spirit or yaw may be controlled by counter clock wise and clock wise scope of the invention. Thus, the present invention is not rotation of the various propellers and the flaperons. In an 5 intended to be limited to the embodiments shown herein but embodiment, yaw may also be controlled by differential is to be accorded the widest scope consistent with the deflection of the flaperons. following claims and the principles and novel features FIG. 6 illustrates a left side view of the embodiment disclosed herein.

VTOL and cruise effcient aircraft 100 transitioning between the VTOL flight phase and a wing born flight phase. During 10 What is claimed is: the transition between VTOL flight and wing born flight the 1. A vehicle, comprising: wing and horizontal tail surfaces may tilt (for example tilt a wing configured to tilt through a range of motion; down to transition from VTOL flight to wing born flight and a plurality of wing electric motors coupled to the wing, tilt up to transition from wing born flight to VTOL flight). In wherein each wing electric motor is configured to drive an embodiment, the propellers 175, 176, 177, 178, and 179 15 an associated wing propeller; (and their right side counterparts), may all be driven by their a tail comprising at least one tail electric motor, wherein respective motors in the transition phase.In another embodi- each tail electric motor is configured to drive an asso- ment, less than all the propellers may be driven during the ciated tail propeller, wherein the tail is configured to tilt transition. Additionally, the landing skids 156 and 158 may through a range of motion; retract. 20 an electric propulsion system connected to the wing FIG. 7 illustrates a left side view of the embodiment electric motors and the tail electric motors; and VTOL and cruise efficient aircraft 100 in the wing born flight wherein the associated wing propellers comprise at least phase. The wing and horizontal tail sections may be tilted one variable pitch propeller and at least one fixed pitch down and the propellers 175, 176, 177, and 179 (and their propeller.

right side counterparts) may be stopped and folded back 25 2. The vehicle ofclaim 1, wherein the at least one variable wing born flight phase, while propeller 224 (and its right pitch propeller is located at a wing tip of the wing.

side counterpart) may be driven by their respective motors 3. The vehicle of claim 1, wherein each associated tail to provide the necessary propulsion for wing born flight. propeller comprises a variable pitch tail propeller.

During wing born flight, pitch may be controlled by eleva- 4. The vehicle ofclaim 1, wherein the at least one variable tors for quick changes and/or by tail rotation for slow 30 pitch propeller is configured to fold back during a wing born rotation, roll may be controlled by the flaperons, and yaw flight phase.

may be controlled by the rudder. 5. The vehicle of claim 1, wherein the wing and the tail In one embodiment, the aircraft 100 may be an unmanned are arranged in a semi-tandem configuration.

aerial vehicle sized for ease of vehicular roadway transpor- 6. The vehicle of claim 1, further comprising reflexed tation. For example, the aircraft 100 may have a tow weight 35 flaperons on the wing and tail.

of less than or equal to about two hundred and fifty pounds 7. The vehicle of claim 1, wherein each tail and wing and may break down into no more than three storage boxes. electric motor are mounted on a motor pylon which is In one embodiment, aircraft 100 may have a set up and shaped to reduce drag at high lift coefficients.

launch time of less than sixty minutes by two trained 8. The vehicle of claim 7, wherein each motor pylon has operators, including off load, assembly, fueling, system 4o a cross sectional area that is less in a middle portion than in checks, and start up. The operators may locally direct takeoff a forward section or an aft section.

of the aircraft 100 than transfer control to a remote location 9. The vehicle of claim 1, wherein the vehicle is an via satellite data link. During recovery the operators may unmanned aerial vehicle.

receive control locally to direct the landing, and landing and 10. The vehicle of claim 1, further comprising retractable vehicle breakdown may take less than thirty minutes for two 45 landing skids and wherein the tail is configured to act as a trained operators, including shut down, drainage of fuel, rear landing skid.

disassemble, and loading of the aircraft 100. 11. The vehicle of claim 1, wherein the range of motion In an embodiment, a payload of the aircraft 100 may be is ninety degrees and the wing and tail are configured to a science payload of twenty five pounds, requiring five transition between a wing born flight phase and a vertical hundred watts of power, and having a volume of about 2500 50 takeoff and landing flight phase by tilting through the range cubic inches. The aircraft 100 may also carry a communi- of motion.

cations payload of about thirty five pounds and requiring 12. The vehicle of claim 11, wherein the wing is swept.

two hundred and seventy watts of power. In an embodiment, 13. The vehicle of claim 1, wherein the wing propellers the aircraft 100 may have a small launch/recovery footprint and the tail propellers are synchronized to each hold specific defined by a twenty foot by twenty foot box. The aircraft 100 55 phase angles to provide destructive interference of propeller may provide landing accuracy and sensor placement within noise.

about 1.5 meters of an intended location. The aircraft 100 14. The vehicle of claim 1, wherein the wing propellers may provide for loiter missions and/or sensor placement and the tail propellers alternate rotation directions and turn missions. In an embodiment, the aircraft 100 may be able to at a low tip speed.

fly only on the secondary power source of the electricity 60 15. The vehicle of claim 1, wherein tail is configured in from the batteries during wing born flight for short periods a dihedral angle.

oftime in order to fly quietly. In an embodiment, the aircraft 16. A vehicle, comprising: may be able to climb to 100 feet before transitioning to wing a wing configured to tilt through a range of motion of 90 born flight. degrees; The preceding description of the disclosed embodiments 65 a plurality of wing electric motors coupled to the wing, is provided to enable any person skilled in the art to make wherein each wing electric motor is configured to drive or use the present invention. Various modifications to these an associated wing propeller;

US 9,896,200 B2

11 12

a tail comprising at least one tail electric motor, wherein each tail electric motor is configured to drive an asso- ciated tail propeller, wherein the tail is configured to tilt through a range of motion; an electric propulsion system connected to the wing 5 electric motors and the tail electric motors; wherein each tail and wing electric motor are mounted on a motor pylon which has a cross sectional area that is less in a middle portion than in a forward section or an aft section; and 10 wherein the associated wing propellers comprise at least one variable pitch propeller and at least one fixed pitch propeller.

17. The vehicle of claim 16, wherein the vehicle is an unmanned aerial vehicle. 15 18. The vehicle of claim 17, wherein the at least one variable pitch propeller is configured to fold back during a wing born flight phase.

19. The vehicle of claim 16, wherein each associated tail propeller comprises a variable pitch tail propeller. 20 20. The vehicle of claim 19, wherein the at least one variable pitch propeller is located at a wing tip of the wing.