Abstract:
An attachable wing for an aircraft is disclosed. The attachable wing is configured to mount to the underside of the fuselage of an aircraft, such as a rotary wing aircraft (e.g., a helicopter) or a fixed wing aircraft. The attachable wing produces additional lift, which results in an increase in speed, and consequently, an increase in fuel efficiency and payload capacity. In some embodiments, the attachable wing is retractable to facilitate takeoffs and landings. Additionally, the apparatus may be made of a bulletproof or anti-ballistic material to protect the aircraft from incoming fire or crash damage. The airfoil apparatus provides additional lift, allowing for greater fuel efficiency and range of the aircraft on which it is installed.

Description:
FIELD OF THE INVENTION 
       [0001]    The present invention relates to aircraft. More specifically, the present invention relates to airfoils mounted on aircraft. 
       BACKGROUND 
       [0002]    Rotary wing aircraft (e.g. helicopters, gyroplanes, and the like, hereinafter, referred to generally as “helicopters”) are useful in a wide variety of applications. In civilian roles, helicopters are used for transport, rescue missions, firefighting, ambulance missions, traffic reporting, and sightseeing excursions, to name a few. In military applications, helicopters play a vital role in battlefield support and other military operations. These include delivering supplies and troops into areas of military conflict. As helicopters play a vital role in both civilian and military applications, it is therefore desirable to have a helicopter that has improved fuel economy, performance, and safety. Similarly, fixed wing aircraft also have a wide variety of uses, and it is equally desirable to have fixed wing aircraft with improved fuel economy, performance, and safety. 
       SUMMARY OF THE INVENTION 
       [0003]    Embodiments of the present invention provide an apparatus for attachment to the underside of the fuselage of an aircraft, such as a rotary wing aircraft (e.g., a helicopter) or a fixed wing aircraft, comprising an airfoil mounted to the underside of the fuselage in order to produce some laminar flow through the device and limit turbulence as much as possible. 
         [0004]    In theoretical operation, fluid flow through the airfoil apparatus causes a pressure drop to develop across the length of the device, thus exploiting basic fluid dynamic phenomena and thermodynamic principles to force the fluid (here, air) from the side of high pressure to the side of low pressure. This flow causes an upward force (i.e., lift) to develop on the underside of the aircraft, which results in an increase in speed, and consequently, an increase in fuel efficiency and payload capacity. In accordance with further embodiments of the present invention, the airfoil apparatus are retractable via a retraction system, and may be activated via hydraulic, cable, or other means. Additionally, the apparatus may be made of a bulletproof or anti-ballistic material to protect the aircraft from incoming fire or crash damage. 
         [0005]    The airfoil apparatus may be comprised of a lightweight metal, such as aluminum or titanium. A composite material may also be used, such as fiberglass, or carbon fiber. Furthermore, an anti-ballistic material, such as Kevlar, or DYNEEMA UD, (produced by DSM DYNEEMA of the Netherlands) may be used to line the airfoil, or even form the airfoil, to provide additional protection from ground fire. This is particularly useful in the case of helicopters, which may be flying slower and lower over a hostile battle zone. The airfoil apparatus may also serve as additional protection in the event of a crash landing, in which case the airfoil apparatus may act as a crumple-zone, and absorb a portion of the impact, providing additional protection for the occupants. 
         [0006]    Embodiments of the present invention provide an airfoil apparatus that can be designed into new aircraft, or developed as a kit for existing aircraft. The airfoil apparatus provides additional lift, allowing for greater fuel efficiency and range of the aircraft on which it is installed. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0007]      FIG. 1  is a cutaway view of the airfoil apparatus in accordance with an embodiment of the present invention. 
           [0008]      FIG. 1A  shows a prior art airfoil for the purposes of establishing definitions. 
           [0009]      FIG. 2  is a side view of the airfoil apparatus. 
           [0010]      FIG. 3  is a front view of the airfoil apparatus. 
           [0011]      FIG. 4  is a perspective view of the airfoil apparatus. 
           [0012]      FIG. 5  is a view of a helicopter with an airfoil apparatus in accordance with an embodiment of the present invention. 
           [0013]      FIGS. 6A-6C  illustrate a retractable airfoil apparatus. 
           [0014]      FIG. 7  is a perspective view of a retractable airfoil apparatus. 
           [0015]      FIG. 8  is a view of a helicopter with a retractable airfoil apparatus in accordance with an embodiment of the present invention. 
           [0016]      FIG. 9  sis a view of a large fixed wing aircraft with an airfoil apparatus in accordance with an embodiment of the present invention. 
           [0017]      FIG. 10  is a view of a small fixed wing aircraft with an airfoil apparatus in accordance with an embodiment of the present invention. 
           [0018]      FIGS. 11-12  show an alternative embodiment of an airfoil apparatus in accordance with the present invention. 
       
    
    
     DETAILED DESCRIPTION 
       [0019]      FIG. 1  is a cutaway view of a portion of an airframe  100  having the airfoil apparatus  105  mounted on the airframe. The airfoil  105  has lower panel  113  which is comprised of a relatively flat bottom surface  116 , and an airfoil shaped upper surface  117 . Side panel  111  has front edge  107 , and rear edge  109 . As the airframe  100  moved forward (the direction indicated by arrow V), air is forced over airfoil shaped upper surface  117  at a faster rate than air traveling along lower surface  116 , thereby creating lift (indicated by arrow L). This takes advantage of space previously not utilized, for the purposes of generating lift. The generated lift can improve fuel efficiency and therefore, the range of the aircraft. In one embodiment, airfoil apparatus  105  is fastened to the lower sides of airframe  100  via a plurality of fasteners  121 . In one embodiment, fasteners  121  are rivets or screws. Alternatively, the airfoil apparatus  105  may be welded in place. Airfoil apparatus  105  may also be mounted directly to the underside of airframe  100  instead of on the lower sides. 
         [0020]      FIG. 1A  shows a prior art airfoil for the purposes of establishing definitions. For the purposes of this disclosure, an airfoil is the shape shown generally as  101  in  FIG. 1A . Airfoil  101  has chord line C which is a straight line connecting the leading and trailing edges of the airfoil. Upper camber U is the distance between chord line C, and the upper surface A, and lower camber L is the distance between chord line C, and the lower surface F, where the upper camber U is greater than or equal to the lower camber L. For the purposes of this disclosure, the lower surface F is referred to as the “flat side” of the airfoil, and the upper surface A is referred to as the “airfoil side” of the airfoil  101 . 
         [0021]      FIG. 2  is a side view of the airfoil apparatus  105 , showing front edge  107 , rear edge  109 , side panel  111 , and lower panel  113 . 
         [0022]      FIG. 3  is a front view of the airfoil apparatus  105 . Side panels  111  join to lower panel  113  at angle A. In one embodiment, angle A ranges from about 90 degrees to about 130 degrees. The lower panel  113  has a width W that is approximately equal to or less than the width of the fuselage of the aircraft it is mounted to. 
         [0023]      FIG. 4  is a perspective view of an airfoil apparatus  405 . In this embodiment, the side panels  111  are of an airfoil shape, where outer surface  121  is the flat side, inner surface  123  is the airfoil side (refer to  FIG. 1A  for explanation about the “flat side” and the “airfoil side”), thereby creating additional lift. 
         [0024]      FIG. 5  is a view of a helicopter  200  with an airfoil apparatus  405  in accordance with an embodiment of the present invention. If landing skids  416  provide sufficient ground clearance, then the airfoil apparatus  405  is suitable. For aircraft with low ground clearance, an embodiment with a retractable airfoil apparatus will now be described. 
         [0025]      FIGS. 6A-6C  illustrate a retractable airfoil apparatus  605  mounted to the lower sides of airframe  600 . In this embodiment, the side panels  611  are comprised of an upper portion  633 , and lower portion  635 . Upper portions  633  and corresponding lower portions  635  are joined via hinges. Lower panels  635  are also attached to lower panel  613  via a hinge or other suitable pivot mechanism  FIG. 6A  shows the airfoil  605  in a fully extended position. Actuators, such as hydraulic pistons, or threaded shafts are used to raise and lower the airfoil  605 .  FIG. 6B  shows the airfoil  605  in a partially retracted position, where the side panels  611  are partially folded, thereby raising lower panel  613  so that it is closer to airframe  600 . In the partially retracted position of  FIG. 6B , hydraulic pistons  641  are visible. Note that in the fully extended position of  FIG. 6A , the pistons are not visible, since they are hidden by the side panels  611 . Pistons  641  are affixed to airframe  600  at one end, and affixed to lower panel  613  at the other end. The pistons hold the airfoil in the extended position ( FIG. 6A ) during flight, and retract the airfoil for landing.  FIG. 6C  shows the airfoil  605  in a fully retracted position. In this position, the pistons  641  are contracted to their minimum length, thereby raising lower panel  613  to allow safe landing. In one embodiment, the retraction of airfoil  605  is synchronized to the extending of landing gear  616 . Landing gear  616  is in a retracted position in  FIGS. 6A and 6B , and hence, not shown in those figures. The retractable airfoil embodiment is useful in cases where the ground clearance of the aircraft is not sufficient for a fixed-position airfoil apparatus, such as that shown as  105  in  FIG. 1 . 
         [0026]      FIG. 7  shows a retractable airfoil apparatus  605 . In this embodiment, side panel  611  is comprised of three upper portions  633 A,  633 B, and  633 C, and three corresponding lower portions,  635 A,  635 B, and  635 C, respectively. Each upper portion is connected to its corresponding lower position via a hinge  637 A,  637 B, and  637 C, respectively. Lower panels  635 A,  635 B, and  635 C, are also attached to lower panel  613  via a hinge or other suitable pivot mechanism (observable in  FIG. 6B  and  FIG. 6C ). The lower end of each piston  641  is attached to lower panel  613 . As pistons  641  extend, the side panel  611  extends, to configure the airfoil apparatus  605  for normal flight (see  FIG. 6A ). As pistons  641  retract, the side panel  611  folds, and lower panel  613  is raised, to configure the airfoil apparatus  605  for landing (see  FIG. 6C ). Upper portion  633 A comprises thin portion  647 A which shields piston  641 A. Similarly, upper portion  633 B comprises thin portion  647 B which shields piston  641 B. In this embodiment, the side panel  611  has an airfoil shape, with the airfoil surface (indicated by reference  651 ) facing the interior of the airfoil apparatus. By using side panels  611  which have an airfoil shape, additional lift can be generated. 
         [0027]      FIGS. 8-10  show various aircrafts utilizing an airfoil apparatus in accordance with embodiments of the present invention.  FIG. 8  is a view of a helicopter  900  with a retractable airfoil apparatus  605  in accordance with an embodiment of the present invention.  FIG. 9  is a view of a large, jet powered, fixed wing aircraft  1000  with an airfoil apparatus  405  in accordance with an embodiment of the present invention.  FIG. 10  is a view of a smaller, propeller driven, fixed wing aircraft  1100  with an airfoil apparatus  405  in accordance with an embodiment of the present invention. For both helicopters and fixed wing aircraft, it is preferable to mount the airfoil apparatus (e.g.  405  or  605 ) near the center of gravity of the aircraft, providing increased lift, while also maintaining stability of the aircraft. 
         [0028]      FIGS. 11-12  show an alternative embodiment of an airfoil apparatus  1205  in accordance with the present invention.  FIG. 11  shows airfoil  1205  in a normal flight configuration. Lower panel  1213  comprises pivot mechanism  1215  at the front end of lower panel  1213  which is affixed to side panels  1211  and which allows adjustment of the angle of lower panel  1213  with respect to airframe  100 . A lifting mechanism  1220 , such as hydraulically actuated pistons, or a threaded shaft raises and lowers the rear of lower panel  1213 .  FIG. 12  shows the airfoil apparatus  1205  in a landing configuration, with landing gear  1216  extended, and lifting mechanism  1220  contracted to raise the rear end of lower panel  1213 . After an aircraft touches down on a runway, the airfoil apparatus  1205  is then put into the configuration shown in  FIG. 12 . This configuration causes the airfoil apparatus  1205  to stop generating lift, and serves to slow the aircraft upon landing, thereby helping to reduce landing distance required for the aircraft. 
         [0029]    Although the description above contains many specific details, these should not be construed as limiting the scope of the invention, but merely as providing illustrations of some of the presently preferred embodiments of the present invention. The present invention may have various other embodiments. Furthermore, while the form of the invention herein shown and described constitutes a preferred embodiment of the invention, it is not intended to illustrate all possible forms thereof. It will also be understood that the words used are words of description rather than limitation, and that various changes may be made without departing from the spirit and scope of the invention disclosed. Thus, the scope of the invention should be determined by the appended claims and their legal equivalents, rather than solely by the examples given.