Abstract:
A multi-wing, multi-engine, multi-hull amphibious aircraft is disclosed. In the illustrative embodiment, the aircraft has an open frame structure without a fuselage.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This case claims priority of U.S. Provisional Patent Application 60/803905, filed on Jun. 5, 2006 and incorporated by reference herein. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates to seaplanes. 
     BACKGROUND OF THE INVENTION 
     Water take-off and landing of amphibious aircraft depends on the planing performance of support floats (for a float plane) or the main fuselage (for a flying boat). 
     By definition, planing situates the aircraft atop the sea-way. In this position, the aircraft is subject to the motions of either following atop or “skipping” over the undulating wave surface. This often results in an unstable surface dynamic response, such as “porpoising” motion and even premature ballistic launch off of wave crests. These behaviors can result in near-surface stalls and crashes. 
     As a consequence, active pilot control and a calm sea-surface environment is required for water take-off and landing. And even with pilot control, take-off and landing is limited to sea states of no more than a few feet (i.e., SS1 or SS2) with conventional present day amphibious aircraft. Autonomous take-off and landing, such as would be required for an unmanned amphibious vehicle, is, for all practical purposes, impossible with present technology. 
     SUMMARY OF THE INVENTION 
     The present invention provides a way to remotely launch and recover unmanned amphibious vehicles, even in high sea states. 
     The illustrative embodiment of the present invention is a multi-wing, multi-engine, multi-hull amphibious aircraft. In the illustrative embodiment, the aircraft has an open frame structure; that is, there is no fuselage. Embodiments of the aircraft include some or all of the following features:
         a canard wing;   high thrust-to-weight ratio power-plants with optional vectoring “free wing” sections;   segmented wing having separately positionable outer and inner segments, thereby providing morphing/moveable wing forms;   semi-submersible wave piercing semi-planing hull forms (catamaran or trimaran style amas);   semi-submersible hulls that pivot independently of the wings and engines;   hydrofoil struts (akas);   UUV transport cradles/structures;   a personnel pod; and   a folding structure for stowage.       

     As described further below, these features provide an amphibious aircraft that has excellent heavy-lift capability (i.e., pounds carried per horsepower), extreme sea state sea-keeping abilities, aeronautic handling stability (i.e., stall resistance), and extensive payload handling space due to the open frame structure (i.e., no fuselage). 
     A canard wing craft is inherently stall resistant. The stall resistance is due to the fact that the canard (forward) wing is designed to stall before the main (aft) wing. This causes the aircraft to pitch down gently, thereby enabling the craft to recover speed, preventing the main wing from stalling. 
     In the illustrative embodiment, the longitudinal spacing of nearly equal wing loads creates a very pitch-stable aircraft, which is a significant stabilizing feature for robotic/autonomous flight control. Also, the longitudinal spacing of nearly equal wing loads provides a craft that has a large tolerance to shifts in payload center-of-gravity of the payload, which is another stabilizing feature. 
     The wing plan of the illustrative embodiment accommodates and, in fact, forms part of the aircraft&#39;s “frame,” which is a box-kite-like structure defined by the multiple hulls, support struts (and the wings). This advantageously connects the multiple hulls with the wings in a geometry that is conducive to rotating mid-wing/engine sections that can produce vectored thrust. In some embodiments, the outboard wing sections have morphing ability to span from STOL (i.e., “short take off and landing”) to cruise-camber cross sections. 
     The strut-supported structural airframe accommodates the morphing wing forms. Further, modular interfaces between wings and airframe facilitate fold, swing and morphing modalities. It is the ‘swing wing’ mode that is particularly well suited to daunting high sea-state amphibious take-offs and landings. In some embodiments, the independent pitch orientation of the wing preserves unbroken streamlines (i.e., ‘non-stalled lifting performance’) through any and all pitch angles of the multi-hull sea-frame hulls below, so long as air velocity is maintained over the wings. 
     The use of tandem engines enables simplified pitch control during vector thrust maneuvers as well as redundant flight power during conventional forward flight. 
     Wave-piercing multi-hull “amas” provide semi-submersible hulls that drastically reduce the tendency for ballistic launch of the air craft off the crest of a wave since they are not fully planing devices. Rather, they gradually rise through the air/ocean interface as more lift is shared with the wings/thrust system. In other words, the aircraft achieves take-off velocity without the hulls coming onto full plane atop the sea surface. This enables safe take-off and landing with relatively greater independence from sea surface state than prior-art amphibious craft. 
     The use of hydrofoil “akas” fore and aft on the amas provides lift when the amas are submerged. 
     Applications for the amphibious aircraft disclosed herein include, without limitation:
         portable over-the-horizon connectivity of UUV/SOF missions in the littoral regions, including versions of scale comparable to and larger than the C-130 Hercules heavy lift aircraft;   portable long duration, geo-stationary deployment for line-of-sight communications and ISR (intelligence/surveillance/reconnaissance) relay in scale modified sizes down to man carry and hand launchable;   portable over-the-horizon connectivity for inter-active re-supply to real-time missions in progress; and   portable over-the-horizon medical evacuation.       

    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  depicts a perspective view of an amphibious aircraft in accordance with the illustrative embodiment of the invention. 
         FIG. 2  depicts a side view of an amphibious aircraft in accordance with the illustrative embodiment of the invention. 
         FIG. 3  depicts a top view of an amphibious aircraft in accordance with the illustrative embodiment of the invention. 
         FIG. 4  depicts a front view of an amphibious aircraft in accordance with the illustrative embodiment of the invention. 
         FIGS. 5A and 5B  depict respective side and cross-sectional views of a wave-piercing semi-submersible hull for use in conjunction with the amphibious aircraft. 
         FIG. 6  depicts a side view of a wave-piercing semi-submersible hull that incorporates hydrofoil wing sections to provide dynamic lift below the waterline. 
         FIG. 7  depicts a personal pod for use in conjunction with the amphibious aircraft disclosed herein. 
         FIGS. 8A-8C  depict several thrust/lift configurations for the engines/wings of the amphibious aircraft disclosed herein. 
         FIGS. 9A and 9B  depict segmented wings for use in conjunction with the amphibious aircraft disclosed herein. 
         FIG. 10  depicts a vectored thrust capability for use in conjunction with the amphibious aircraft disclosed herein. 
         FIGS. 11A-11C  depict a manner in which a vectored thrust capability is used to accommodate changes in air flow over the wings as a function of wave motion. 
         FIGS. 12A-12C  depict pivoting semi-submersible hulls that are movable independently of the wings as a function of wave motion to maintain a desired air flow over the wings. 
     
    
    
     DETAILED DESCRIPTION 
       FIGS. 1-4  depict various views of amphibious aircraft  100  in accordance with the illustrative embodiment of the invention. In particular,  FIG. 1  depicts a perspective view,  FIG. 2  depicts a side view,  FIG. 3  depicts front view, and  FIG. 4  depicts a top view. 
     Referring now to  FIGS. 1-4 , amphibious aircraft  100  comprises hulls  102 , canard wing support struts  106 , canard wing  108 , canard wing prop  110 , canard wing engine  111 , main wing support struts  112 , main wing  114 , main wing prop  116 , main wing engine  117 , and tail  118 , interrelated as shown. 
     In the illustrative embodiment, hulls  102  are semi-submersible, wave-piercing, catamaran “amas.” Referring to  FIGS. 5A  (side view) and  5 B (cross section thru s-s), hulls  102  have ledges or “strakes”  576  that provide lifting/planing regions below the waterline. 
     In the embodiment that is depicted in  FIGS. 2 and 4 , hydrofoil “akas”  230  and  232  depend from respective fore and aft regions of the top of each hull  102 . In an alternative embodiment depicted in  FIG. 6 , hydrofoils akas  630  and  632  depend from respective fore and aft regions on the bottom of each hull  102 . 
     With continued reference to  FIGS. 1-4 , in  FIG. 1 , props  110  and  116  are both disposed in front of the associated wing.  FIGS. 2 and 4  show an alternative embodiment of aircraft  100 , wherein prop  110  is disposed aft of canard wing  108  and prop  116  is disposed forward of main wing  116 . In other words, props  110  and  116  face each other. Thrust configurations are described further later in this specification in conjunction with  FIGS. 8A-8C  and  10 . 
     Canard wing  108  is supported by two struts  106  that, in the illustrative embodiment, depend from a forward region of the upper surface of hulls  102 . In some embodiments, canard wing  108  is movably coupled to struts  106  so that wing  108  is free to rotate about axis A-A. In the embodiment that is depicted in  FIG. 1 , axis A-A is depicted as falling along the centerline of wing  108 . The actual location of this axis of rotation is a function of aerodynamic considerations and desired capabilities. In conjunction with this disclosure, it is within the capabilities of those skilled in the art to determine the position of this rotational axis. 
     Main wing  114  is supported by two struts  112  that, in the illustrative embodiment, depend from an aft region of the upper surface of hulls  102 . In some embodiments, main wing  114  is movably coupled to struts  112  so that wing  114  is free to rotate about axis B-B. As indicated with respect to canard wing  108 , the depicted location of axis A-A is merely for illustrative purposes; its actual position is determined as a function of aerodynamic considerations and craft capabilities. The term “pitchable” is used herein to refer to the aforedescribed movement of wings  108  and  114 . 
     In some embodiments, such as the embodiment depicted in  FIG. 1 , canard wing  108  and/or main wing  114  are segmented. For example, canard wing  106  comprises outer segments  120  and inner segment  122 . Likewise, main wing  114  has outer segments  124  and inner segment  126 . The segmented structure facilitates independent movement of the inner and outer segments of each wing. In other words, inner segment  122  of canard wing  108  is movable independently of outer segments  120 . In various embodiments:
         The inner segment is independently movable and the outer segments are fixed;   The inner segment is independently movable and the outer segments are collectively movable;   The inner segment is independently movable and the outer segments are movable independently of each other;   The inner segment is fixed and the outer segments are collectively movable; and   The inner segment is fixed and the outer segments are movable independently of each other.
 
This capability is described in further detail later in this specification in conjunction with  FIGS. 9A-9B .  11 A- 11 C,  12 A- 12 C.
       

     Any of a variety of mechanical arrangements can be used to provide the requisite degree of freedom to wings  108  and/or  114  and to the various wing segments. In conjunction with the present disclosure, those skilled in the art will be able to couple the wings to the struts in such a way that the wings are movable relative to the struts, or, as appropriate wing segments are independently movable. 
     The embodiment of aircraft  102  that is depicted in  FIG. 2  includes a number of auxiliary sub-systems, many of which are intended for use in military and/or rescue applications. These include: station-keeping thruster  240 , sonobuoys  242 , winch, reel &amp; cable  244 , sonar &amp; chute  246 , flight computer  248 , avionics  250 , MMW radar  252 , EO/IR electronics  254 , chaff dispenser  256 , flare dispenser  258 , and antenna  260 . The design and use of these devices and systems are known to those skilled in the art. 
       FIGS. 3 and 4  depict aircraft  100  carrying UUVs  370  (unmanned underwater vehicles). These UUVs are coupled to crossbeams  372 . Aircraft  100  provides a means for launching UUVs  370  directly into a desired theater of operation. This is advantageous because, due to size and weight limitations, UUVs typically carry relatively few batteries on board. Since these batteries must power the UUV drive system, UUVs typically have a relatively limited range. Aircraft  100 , with its ability to take-off and land in high sea states, can sortie from a ship, fly to a remote location, land in high sea states, launch UUVs  370 , then take-off and return to its mother ship. This can significantly extend the period of time that the UUV can operate, since battery power is not used to transport the UUV to its theater of operation. 
     The open frame structure of aircraft  100  enables it to accommodate various payloads. In some embodiments, such as the embodiment depicted in  FIG. 7 , aircraft  100  includes personnel pod  780 . In this embodiment, the pod is suspended from canard wing  108  between struts  106 . 
       FIGS. 8A through 8C  provide several thrust configurations for aircraft  100 . The thrust configuration depicted in  FIG. 8A  includes two engines  11  and  117  driving respective propellers  110  and  116  that are situated forward of the associated wing and disposed one behind the other along the centerline of aircraft  100 . This thrust configuration is also illustrated in  FIG. 1 . 
       FIG. 8B  shows an alternative thrust configuration that includes two engines  111  and  117  driving respective propellers  110  and  116  that are disposed one behind the other along the centerline of aircraft  100 . In this embodiment, prop  110  is disposed aft of the canard wing and prop  116  is disposed forward of the main wing. This thrust configuration is also illustrated in  FIGS. 2 and 4 . 
       FIG. 8C  shows a further alternative thrust configuration wherein the two props  110 A and  110 B are associated with canard wing  108 , wherein prop  110 A is forward of that wing and prop  110 B is aft. Engines  111  and  117  are connected by common longitudinal propeller shaft  882 , permitting both of the engines to drive both propellers. 
       FIGS. 9A and 9B  provide further illustration of the use of a segmented wing. These figures depict main wing  114 , which is segregated into outer segments  124  and inner segment  126 . In  FIG. 9A , segments  124  and  126  are co-planar and horizontal.  FIG. 9B  depicts wing  114  when outer segments  124  are rotated so that the leading edge of the wing is raised, while the inner segment remains horizontal. 
       FIG. 10  depicts an embodiment wherein at least the inner segments  122  and  126  of respective wings  108  and  114  are pitchable to provide vectored thrust. In other words, props  110  and/or  114  are pitchable. Among any other benefits, this provides aircraft  100  with a vertical takeoff and landing capability. 
       FIGS. 11A-11C  provide further disclosure concerning the ability and benefits of being able to pitch at least canard wing  108 . In these figures, only the wings and hulls are depicted for clarity. In the depictions that follow, those skilled in the art will recognize that moving the canard wing in the manner described will aid in stall prevention. 
       FIG. 11A  depicts aircraft  100  in calm water, with short-wavelength swells. Semi-submersible hulls  102  maintain aircraft  100  in a relatively level attitude, such that horizontal incidental air streamlines are preserved. 
       FIG. 11B  depicts aircraft  100  in rough water, with relatively longer-wavelength swells. This figure depicts aircraft  100  riding down a lowering sea swell, and depicts rising air streamlines. The leading edge of canard wing  108  is pitched “downward” to accommodate for the angle of these streamlines to maintain a “horizontal” or flat-planar relationship between the streamlines and canard wing  108   
       FIG. 11C  depicts aircraft  100  in rough water, with relatively longer-wavelength swells. This figure depicts aircraft  100  riding up the rising sea swell, and depicts descending air streamlines. The leading edge of canard wing  108  is pitched “upward” to accommodate for the angle of these streamlines to maintain a “horizontal” or flat-planar relationship between the streamlines and canard wing  108 . 
     In some embodiments, hulls  102  are independently movable (i.e., pitchable) relative to wings  108  and  114 . This can serve some of the same purposes as enabling the wings to pitch. In particular, it can maintain a desirable relationship between air streamlines and the wings for stall prevention. 
       FIGS. 12A-12C  depict aircraft  100  (again illustrated as simply a hull and wings) with pitchable hulls  102 . 
       FIG. 12A  depicts aircraft  100  in calm water, with short-wavelength swells. Semi-submersible hulls  102  maintain aircraft  100  in a relatively level attitude, such that horizontal incidental air streamlines are preserved. 
       FIG. 12B  depicts aircraft  100  in rough water, with relatively longer-wavelength swells. This figure depicts aircraft  100  riding down a lowering sea swell. Hulls  102  are free to rotate downward relative to wings  108  and  114  so that the wings remain level. 
       FIG. 12C  depicts aircraft  100  in rough water, with relatively longer-wavelength swells. This figure depicts aircraft  100  riding up a rising sea swell. Hulls  102  are free to rotate upward relative to wings  108  and  114  so that the wings remain level. 
     Any of a variety of mechanical arrangements can be used to provide the requisite degree of freedom to hulls  102 . For example, in some embodiments, struts  106  and/or  112  can be appropriately hinged to hulls  102 . In conjunction with the present disclosure, those skilled in the art will be able to couple the hulls and struts such that hulls are movable independently of the struts/wings. The term “pitchable” is used herein to refer to the aforedescribed movement of hulls  102 , as well as to describe the movement of wings  108  and  114 . 
     It is to be understood that the disclosure teaches only several alternatives of the illustrative embodiments and that many variations of the invention can easily be devised by those skilled in the art after reading this disclosure and that the scope of the present invention is to be determined by the following claims.