LIGHT TWIN ENGINE AIRCRAFT

Abstract

An aircraft includes a fuselage having a nose end and a tail end and a center of gravity. A primary wing is coupled to the fuselage aft of the center of gravity. A secondary wing is coupled to the fuselage forward of the center of gravity. A v-tail is coupled to the fuselage between the primary wing and the tail end of the fuselage, the v-tail comprising first and second angled stabilizers, each of the first and second stabilizers including a first end fixed to the fuselage and a second free end, distal to the fuselage.

Claims

1. An aircraft comprising: a fuselage having a nose end and a tail end and a center of gravity; a primary wing coupled to the fuselage aft of the center of gravity; a secondary wing coupled to the fuselage forward of the center of gravity; and a v-tail coupled to the fuselage between the primary wing and the tail end of the fuselage, the v-tail comprising first and second angled stabilizers, each of the first and second stabilizers including a first end fixed to the fuselage and a second free end, distal to the fuselage.

2. The aircraft of claim 1, further comprising a first engine coupled to the second end of the first stabilizer and a second engine coupled to the second end of the second stabilizer.

3. The aircraft of claim 2, wherein the first engine includes a first propeller and the second engine includes a second propeller, the first and second propellers being oriented in puller configuration.

4. The aircraft of claim 1, further comprising a first ruddervator coupled to the first stabilizer and a second ruddervator coupled to the second stabilizer.

5. The aircraft of claim 4, further comprising a flight control mixer that is operatively connected to each of the first and second ruddervators.

6. The aircraft of claim 5, wherein the mixer comprises a base; a trunk rotatably coupled to the base; an actuator pivotably coupled to the trunk, the actuator including a body, the body including a first leg and a second leg extending outward from the body proximate the trunk, and a first arm and a second arm extending outward from the body distal to the trunk. a roll input connection located on the body; and a pitch input connection located on the body.

7. The aircraft of claim 1, further comprising a landing gear having a main strut; a wheel link connected to the main strut, the wheel link having a wheel connection that is configured to accept a wheel; a stabilizer bar connected to the main strut and to the wheel connection; and a ski, the ski having a front portion that is substantially planar and a rear portion that is substantially planar, the front portion and the rear portion being angled relative to one another, wherein the front portion and the rear portion form an angle greater than 0 degrees but less than 45 degrees.

8. The aircraft of claim 1, wherein the aircraft is amphibious, the fuselage comprising channels on each side of a lower portion of the fuselage, beginning aft of the secondary wing and merging aft of the primary wing to form a single channel.

9. The aircraft of claim 8, further comprising a water rudder coupled to an underside of the fuselage, aft of the primary wing.

10. A flight control input mixer for a twin engine v-tail aircraft, the flight control input mixer comprising: a base; a trunk rotatably coupled to the base; an actuator pivotably coupled to the trunk, the actuator including a body, the body including a first leg and a second leg extending outward from the body proximate the trunk, and a first arm and a second arm extending outward from the body distal to the trunk. a roll input connection located on the body; and a pitch input connection located on the body.

11. The mixer of claim 10, wherein a first yaw input is operatively connected to the first leg and a second yaw input is operatively connected to the second leg.

12. The mixer of claim 10, wherein a first ruddervator output is connected to the first arm and a second ruddervator output is connected to the second arm.

13. The mixer of claim 10, wherein the roll input comprises a socket.

14. The mixer of claim 13, further comprising a bell crank connected to the socket.

15. The mixer of claim 14, wherein the body distal to the roll input is pivotable about the roll input.

16. A landing gear for an amphibious aircraft, the landing gear comprising: a main strut; a wheel link connected to the main strut, the wheel link having a wheel connection that is configured to accept a wheel; a stabilizer bar connected to the main strut and to the wheel connection; and a ski, the ski having a front portion that is substantially planar and a rear portion that is substantially planar, the front portion and the rear portion being angled relative to one another, wherein the front portion and the rear portion form an angle greater than 0 degrees but less than 45 degrees.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0035] FIG. 1 is a perspective view of a light twin-engine aircraft that is constructed in accordance with the teachings of the disclosure.

[0036] FIG. 2 is a front elevational view of the aircraft of FIG. 1.

[0037] FIG. 3 is a rear elevational view of the aircraft of FIG. 1.

[0038] FIG. 4 is a top plan view of the aircraft of FIG. 1.

[0039] FIG. 5 is a bottom plan view of the aircraft of FIG. 1.

[0040] FIG. 6 is a left side view of the aircraft of FIG. 1.

[0041] FIG. 7 is a front view of a control input mixer that is implemented in the aircraft of FIG. 1.

[0042] FIG. 8 is a side view of the control input mixer of FIG. 7.

[0043] FIGS. 9A-9C are schematic representations of the control input mixer of FIG. 7 and the operation of left and right ruddervators in level flight (e.g., zero degrees of roll).

[0044] FIGS. 10A-10C are schematic representations of the control input mixer of FIG. 7 reacting to a roll input and the operation of the left and right ruddervators in banked flight (e.g., greater than zero degrees of roll).

[0045] FIG. 11 is a side view of a main landing gear of the aircraft of FIG. 1 in a fully extended, fully loaded configuration.

[0046] FIG. 12 is a side view of the main landing gear of FIG. 12 in a fully extended, unloaded configuration, illustrating an angle of ski travel.

[0047] FIG. 13 is a front view of the landing gear of FIG. 11.

[0048] FIG. 14 is a front view of the landing gear of FIG. 12 in a fully retracted configuration, illustrating main gear tire rotation of 90 degrees when fully stowed in a wheel well.

DETAILED DESCRIPTION

[0049] Generally, a multi-engine aircraft that is constructed in accordance with the teachings of the disclosure includes at least one fuselage of modified tadpole longitudinal cross section with a center of gravity (CG), a forward end, an aft end, left and right undersides formed into fluid flow directing channels, a main wing mounted low on the aft of the CG on the fuselage, a forward wing mounted on the fuselage at or near the vertical midpoint ahead of the CG, and a V-tail empennage mounted on the fuselage aft the main wing, which merges the fluid directing channels. Two tractor propeller power plants are coupled to the distal ends of the empennage, and a retractable tricycle landing gear system is coupled to the fuselage. In various embodiments the aircraft is operable on land, water, snow, or soft terrain. The disclosed aircraft fuselage provides payload volume as well as the attachment structure for the forward wing, main wing, empennage, and forward landing gear. Avionics and accommodations for crew and passengers are also contained therein.

[0050] Turning now to FIGS. 1-6, an aircraft 10 comprises a fuselage 12 having a nose end 14 and a tail end 16 and a center of gravity 18. A primary wing 20 is coupled to the fuselage 12 aft of the center of gravity 18. In the illustrated embodiment, the primary wing 20 includes two airfoils 20a, 20b, each attached to one side of the fuselage 12. A wing box (not shown) may extend through the fuselage 12 to connect the two airfoils 20a, 20b to the fuselage 12, for structural rigidity. In other embodiments, the two airfoils 20a, 20b may be separately mounted to the fuselage in a cantilever configuration. A secondary wing 22 is coupled to the fuselage 12 forward of the center of gravity 18. Like the primary wing 20, the secondary wing 22 may include two airfoils 22a, 22b. A v-tail 24 is coupled to the fuselage 12 between the primary wing 20 and the tail end 16 of the fuselage 12. The v-tail 24 includes a first angled stabilizer 26 and a second angled stabilizer 28. Each of the first and second stabilizers 26, 28 includes a first end 30a, 30b fixed to the fuselage 12 and a second free end 32a, 32b, distal to the fuselage 12.

[0051] A first engine 40 is coupled to the second end 32a of the first stabilizer 26 and a second engine 42 coupled to the second end 32b of the second stabilizer 28. The first engine 40 includes a first propeller 44 and the second engine 42 includes a second propeller 46, the first and second propellers 44, 46 being oriented in puller configuration. In other words, the first and second propellers 44, 46 are located forward of the respective engine 40, 42 (e.g., towards the nose end 14 of the fuselage 12).

[0052] A first ruddervator 50 is coupled to the first stabilizer 26 and a second ruddervator 52 is coupled to the second stabilizer 28. The first and second ruddervators 50, 52 react to pilot control inputs to generate pitch and yaw forces to control the aircraft 10 during flight and ground operations. A flight control mixer 100 (FIGS. 7-10) is operatively connected to each of the first and second ruddervators 50, 52, which translates both control yoke/stick movements and rudder pedal movements into the appropriate first and second ruddervator 50, 52 movement to produce desired control forces.

[0053] In the aircraft 10 in the illustrated embodiment, the fuselage 12 includes steps or channels 54a, 54b on each side of a lower portion of the fuselage 12. The channels 54a, 54b begin aft of the secondary wing 22, run longitudinally along the fuselage 12, and merge together aft of the primary wing 20 to form a single empennage channel 56. A rudder 58 is coupled to an underside of the fuselage 12, aft of the primary wing 20. The rudder 58 is movable through connections to rudder pedals. The rudder 58 is reinforced to aid in steering the aircraft 10 during water operations, much like a ship or boat rudder in amphibious embodiments.

[0054] Turning now to FIGS. 7-10, the flight control input mixer 100 includes a base 102, a body 104 rotatably coupled to the base 102, an actuator 106 including a trunk 108 pivotably coupled to the base 104, a roll input 110 connection located on the trunk 108; and a pitch input 112 connection located on the trunk 108.

[0055] The body 104 includes a first leg 114 and a second leg 116 extending outward from the body 104 proximate the trunk 104, and a first arm 118 and a second arm 120 extending outward from the body 104 distal to the trunk 104. A first yaw input 122 is operatively connected to the first leg 114 and a second yaw input 124 is operatively connected to the second leg 116. A first ruddervator output 126 is connected to the first arm 118 and a second ruddervator output 128 is connected to the second arm 122. A saddle 109 pivotably connects the trunk 108 to the body 104.

[0056] In some embodiments, the roll input 110 may comprise a socket 130. The body 108 distal to the roll input 110 is pivotable about the roll input 110.

[0057] As a typical V-tail aircraft rolls about a longitudinal axis, the ruddervator located in the direction of the roll gets closer to the plane of the horizon, and begins to project the nose more directly toward the ground or skyward. As the V-tail aircraft rolls, the forces produced by the ruddervators begin to adversely affect controllability because a given input no longer acts in the original plane. For example a ruddervator input to the more horizontally oriented ruddervator in a tight turn would tends pitch the nose of the aircraft downward, thereby inducing a spin attitude. Similarly a rudder input in a slip maneuver tends to pitch the nose skyward in what is already a very high drag maneuver. Pilots need to be trained for these adverse effects and learn to compensate with elevator inputs.

[0058] The disclosed flight control mixer advantageously automatically compensates for the problem described above because the net deflection realized through the ruddervator mixer is to decrease the travel of the ruddervator at or nearer to horizontal, thereby decreasing the adverse forces produced by the horizontal ruddervator.

[0059] The disclosed flight control mixer 100 decreases adverse forces by adding the roll-input 110. The body 108 of the flight control mixer 100 pivots about a point that is located above the plane of rotation of the trunk 104 such that the body 108 rolls in a direction opposite of the aircraft roll. For example, if the aircraft rolls left for a standard left turn then both the left wing and the left ruddervator descend but the left side of the flight control mixer 100 rises. The motion of the flight control mixer 100 puts its elevated end closer to or directly over the point of rotation (i.e., the point of rotation between the trunk 104 and the base 102). As the elevated side of the body 108 approaches the center of rotation a travel arc in response to rudder input is reduced (see FIGS. 10A-10C). Shorter travel means less response by the ruddervator. Since the elevated side of the flight control mixer 100 controls the ruddervator that is lower as the angle of roll increases the ruddervator closer to horizontal begins to reduce rudder input and behave more as strictly as a conventional elevator. The net result is an aircraft with a V tail that behaves like a traditional cruciform tail aircraft in roll attitudes approaching 45 degrees.

[0060] In some embodiments, the disclosed aircraft is sized to accommodate a single pilot and up to 7 passengers and personal cargo. In such embodiments the length of the aircraft from nose to its aft-most surface may be approximately 18 feet and a projected wingspan may be approximately 38.5 feet. In alternative embodiments these dimensions and personage can change. For example, the aircraft may be scaled up or down proportionally. In other embodiments, the aircraft may be longer or shorter, wider or narrower, require a larger crew or operate totally unmanned, carry fewer or greater numbers of passengers.

[0061] The engines include counter-rotating output shafts. In other words, the propellers attached to the engines rotate in opposite directions. Propeller rotation for the left (port) side is counterclockwise when viewed from the front, and clockwise on the right (starboard) side. Such counter rotating propellers locate a descending propeller blade inboard, nearer the aircraft center line to reduce the effect of P factor.

[0062] Returning now to FIGS. 1-6, the aircraft 10 includes the secondary or forward wing 22, the primary or main wing 20, and the V-tail 24. The forward wing 22 and main wing 20 are trimmed to generate lifting force when air is flowing over the aircraft 10. The forward wing 22 is trimmed and shaped to react more quickly to changes in airspeed relative to the main wing 20 to provide stall resistance and increased leaver arm to correct control issues due to the relatively close coupling of the main wing 20 and V-tail 24.

[0063] When the ruddervators 50, 52 are at the neutral position, the angled stabilizers 26, 28 are trimmed to generate a net downforce in level flight.

[0064] The main wing 20 includes a steady dihedral along its span (see e.g., FIGS. 2 and 3. The main wing 20 is divided into three main spanwise sections, an inner section 60a, an outer section 60b, and a tip 60c. The inner section 60a is swept at the root to improve aerodynamics at the fuselage joint and fluid flow when in motion and provides buoyancy in amphibious operation. The trailing edge 64 of the inner section 60a is fairly straight and includes a short, sharply-raked water deflection and fuselage trim section 66 inboard that also serves as a bridge between the fuselage 12 and empennage flow directing channels (i.e., the channels 54a, 54b, and 56).

[0065] The trailing edge 64 of the inner section 60a and a trailing edge 68 of the outer section 60b meet flush, but a leading edge 70 of the outer section 60b extends forward of a leading edge 72 of the inner section 60a to form a cuff 74. The cuff 74 compensates for adverse lateral flow from the inner section 60a to the outer section 60b, which can contribute to dutch roll, as well as forward wingtip vortices.

[0066] The span of the outer section 60b has the unswept leading edge 70 and the raked trailing edge 68 to increase the aspect ratio and improve efficiency and glide characteristics. The tip section 60c is designed for simplicity; however, other embodiments may feature different shapes or features including but not limited to winglets, up or down turned ends, or fuel tanks.

[0067] Turning now to FIGS. 12-15, the main wing 20 houses the left and right main landing gear and associated retraction systems. These systems may be electric in nature and may include a motor 260 with swing arm 262, a torque tube 264, and a pair of A-arms 266 arranged to operate in a scissor motion when torque is applied. The A-arms 266 overextend when the gear is deployed to lock the gear in the down position. The main landing gear uses conventional retract system in land-only capable units. The gear retract laterally inward; i.e. toward the fuselage, somewhat parallel to the main wing spar. A main strut 202 rotates 90 degrees such that a lower main gear leg 204 and wheels 208 are in line with a longitudinal axis of the aircraft when deployed and in line with a lateral axis of the aircraft when fully retracted.

[0068] Embodiments adapted for amphibious operation use a ski/hydrofoil system that allows the aircraft to operate from water without requiring a change in landing configuration for the gear and high lift devices.

[0069] The amphibious landing gear configuration itself includes the main strut 202 having a support strut upper 202a, a main support strut lower 202b, a trailing arm with suspension strut and one or more wheels 208, a hydrofoil ski/door 212, and three secondary support arms 240, 242, 244 arranged to support the hydrofoil ski/door 212. A lower main support leg 204 accommodates rotation of the hydrofoil ski/door 212 from deployed to retracted and vice versa such that the hydrofoil ski/door 212 forms the lower wing skin and main gear door when retracted. A second gear door completes the retracted gear housing. The secondary support arms 240, 242, 244 join each other at a point 250 forward of the main strut 202 between the wing underside (not shown in FIGS. 12-15) and the hydrofoil ski/door 212 when deployed, and below it when retracted. An opposite end of the upper secondary arm 240 is mounted to the wing structure. An opposite end of the central secondary arm 242 is mounted to the lower main gear leg 204. An opposite end of the lower secondary arm 244 is mounted to the hydrofoil ski/door 212. The three secondary arms 240, 242, 244 operate in a scissor-fold action to support the hydrofoil ski/door 212 as it moves with a trailing arm. It is a load-bearing structure.

[0070] More specifically, the landing gear 200 for amphibious adaptation of the aircraft includes the main strut 202 and the lower main support leg 204, which is connected to the main strut 202, the lower main support leg 204 having a wheel connection 206 that is configured to accept the wheel 208. An oleo strut 210 is connected to the main strut 202 and to the wheel connection 206. The hydrofoil ski/door 212 has a front portion 212a that is substantially planar and a rear portion 212b that is substantially planar. For example, in one embodiment, the front portion 212a and the rear portion 212b form an angle greater than 0 degrees but less than 45 degrees.

[0071] In some embodiments, main wings 20 incorporate extended range fuel tanks internally. In other embodiments, the main wings 20 may have joints where each wing can fold, thereby reducing the size of the aircraft so that it can fit in a constrained space, for example while docked or for transport overland. A wing fold that allows the wing to rotate vertically may be positioned at a location where the loads are small, outboard of 50% of the span, to allow the wing to fold without interrupting the maximum propeller travel arc or propeller disc. In other embodiments the wing fold is set to allow the upturned ends of the wings to frame the propeller disc. In still others the fold joint allows the main wing to fold to a span matching that of the forward wing. In other embodiments the wings may fold in a compound motion to the vertical and fore or aft simultaneously leaving the folded sections parallel the longitudinal axis.

[0072] In one embodiment, control surfaces may be included on all three main flight surfaces. For example, in one embodiment, the forward wing 22 may include high-lift devices in the form of trailing edge flaps 90a, 90b. The flaps 90a, 90b may alternately have 2, 3 or more position settings which can include but are not limited to a range of 15 degrees of upward (negative) travel to 40 degrees downward (positive) travel. Negative travel would allow the forward wing 22 to be trimmed to neutral lift during high speed flight at altitude reducing drag and increasing efficiency. Positive travel increases both lift and drag to reduce take-off and landing distances. In other embodiments the forward wing 22 may include an elevator 92a, 92b, which may act as the primary pitch control.

[0073] In alternative embodiments, the V-tail 24 may alternately include ruddervators or rudders. Ruddervators may include a more neutral dihedral to allow effective control in both pitch and yaw although the extended lever arm provided by the forward wing 22, thus increasing effectiveness in pitch control.

[0074] The main wing 20 outer section 60b trailing edge 68 may include ailerons or alternatively flaperons 94a, 94b. In either case these surfaces move opposite one another to provide the pilot roll control. As flaperons 94a, 94b they move collectively to increase lift and would be deployed in take-off and landing as deemed appropriate and necessary by the pilot. The flaperons 94a, 94b may augment the trailing edge flaps 90a, 90b, or in other embodiments, the flaperons 94a, 94b may provide sufficient low speed lift to replace the trailing edge flaps 90a, 90b. The main wing 20 outer section 60b leading edge 70 may include fixed or retractable slats (not shown). Slats reduce wing stall speed, thereby allowing greater control in slow flight.

[0075] In some embodiments the fuselage channels 54a, 54b and the empennage channel 56 are concave forms, in other embodiments, they may be formed by a single centerline keel. Sister keelsons may or may not be affixed in-line with the channels and may or may not replace the concave forms or keel.

[0076] In some embodiments a traditional stepped flying boat hull includes left and right edges of the step that begin flush with a filleted edge of the fuselage underside and gradually move aft, increasing in pitch to the centerpoint of the step located ahead of the main wing leading edge at the unloaded CG. The step may or may not be retractable; and, when the step is retractable, the step may optionally deploy simultaneously with the landing gear.

[0077] The disclosed aircraft is operable on land, water, snow, or soft terrain.

[0078] The disclosed aircraft may land on water by decelerating to the design landing speed and configuring the flaps and the aircraft otherwise for landing. This includes deploying the landing gear which, being equipped with water skis, contacts the water surface first and simulates landing behavior on prepared dry fields. The aircraft first contacts the water at the main landing gear skis while the pilot maintains a nose-high attitude to slow the craft and prevent prematurely making surface contact with the nose ski (this operation is similar to typical dry field landings). After the pilot allows the nose ski to contact the water and allows the aircraft to drop below hydroplaning speed and come to rest on the fuselage reinforced underside. As the aircraft slows, it transitions to hull displacement.

[0079] On landing the forward wing 22 aerodynamically mitigates excessive nose-high attitude but, should the aircraft come to rest on the main gear skis and tail or tail-first, the shaped hull advantageously forms below the empennage a contact surface and resists swamping. In this attitude the shaped aft fuselage also increases the nose-down moment on the main gear to raise the minimum hydroplaning speed. If the pilot persists the nose-high approach these features facilitate bringing the aircraft to rest on the water surface without suffering catastrophic damage. Similarly in a nose-down approach the nose ski will contact the surface first and absorb the impact energy allowing the pilot to correct and go-around.

[0080] Once in hull displacement mode on water the gear can be retracted for waterborne navigation taxi and docking; however, the landing gear would remain deployed for beaching.

[0081] The aircraft may operate on water by surface taxiing. Stability and efficiency are achieved through a combination of aft CG, the aforementioned hull and empennage shape(s), and the wetted main wing. With the ski-equipped landing gear retracted and absent the optional step, or if the step is present and equipped to be retracted, the craft is configured to remain rooted to the surface in navigation taxi to resist upsetting the waterborne balance and reduce pilot workload.

[0082] The aircraft my take-off from water. In an embodiment without a step the landing gear must be deployed. In embodiments with a step it is recommended to deploy the gear but a safe take-off can be accomplished with the gear retracted.

[0083] In a gear down water take-off, nose-high trim is achieved through a combination of lifting forces generated by the hull, nose gear ski, and forward wing. Once surface speed exceeds taxiing speed the aircraft transitions to a planing regime. The aircraft then completes the take-off as if it were a land-based take-off. Similar to water landings excessive attitudes are mitigated by the design's forward wing and hydrodynamic shapes.

[0084] The aircraft may operate with either of the powerplants inoperative with neither engine more critical to safe operation than the other. The aircraft's forward wing design allows for operation in these adverse conditions with minimized stall-spin risk because the forward wing stall speed is above the Vmc minimum safe single engine maneuver speed.

[0085] Vmc is further reduced by a paradoxical and unexpected, but favorable effect of mounting the engine on the tail surface. The tail is trimmed to produce downforce to supplement the forward wing and balance the CG forward of the main wing and create dynamic stability. In single engine operationemergency or otherwisethis downforce is increased asymmetrically, similar to, but opposite of, current piston twin aircraft. The favorable affect is a tendency to roll the aircraft into the operating engine creating horizontal lift components from the forward and main wing that are opposite the adverse yaw generated by the asymmetric thrust.

[0086] The described embodiments provide an aircraft with a configuration that is safe, versatile, and efficient, as well as easy to control, highly capable, and which is able to operate from almost anywhere.

[0087] Although this description has been provided in the context of specific embodiments, those of skill in the art will appreciate that many alternative embodiments may be inferred from the teaching provided. Furthermore, within this written description, the particular naming of the components, capitalization of terms, etc., is not mandatory or significant unless otherwise noted, and the mechanisms that implement the described invention or its features may have different names, formats, or protocols.

[0088] Finally, it should be noted that the language used in the specification has been principally selected for readability and instructional purposes, and may not have been selected to delineate or circumscribe the inventive subject matter. Accordingly, the disclosure is intended to be illustrative, but not limiting, of the scope of the invention.

[0089] While various embodiments have been described above, this disclosure is not intended to be limited thereto. Variations can be made to the disclosed embodiments that are still within the scope of the appended claims.