FIELD OF THE INVENTION  
       [0001]     The present invention relates to aircraft with an extendable leading edge, and more particularly relates to a combined fuselage and wing leading edge which can be moved from a retracted position against the fuselage and wings to an extended position which provides increased lift for the aircraft at low speeds.  
       BACKGROUND INFORMATION  
       [0002]     Aircraft often utilize devices on leading wing edges in order to increase lift at low speeds. For example, aircraft with high leading edge wing sweep may use devices on the leading edges of the wings to increase lift during takeoff and landing and thus reduce runway length. Such leading edge devices typically have gaps that are visible from the front when the devices are stowed. However, some aircraft have survivability requirements that do not allow leading edge gaps when the devices are stowed. It would be desirable to provide a leading edge device which avoids such problems.  
       SUMMARY OF THE INVENTION  
       [0003]     The present invention provides an extendable leading edge for the fuselage and wings of an aircraft. The leading edge may be moved from a retracted position adjacent to the fuselage and wings to an extended position away from the fuselage and wings which increases lift of the aircraft, particularly during takeoff, landing and other low speed operations. When the leading edge is retracted during flight, unwanted gaps are avoided.  
         [0004]     An aspect of the present invention is to provide an aircraft comprising a fuselage, wings connected to the fuselage, and a leading edge forwardly extendable from a retracted position against the fuselage and wings to an extended position from the fuselage and wings.  
         [0005]     Another aspect of the present invention is to provide an aircraft comprising a fuselage and a leading edge forwardly extendable from a retracted position against the fuselage to an extended position from the fuselage.  
         [0006]     These and other aspects of the present invention will be more apparent from the following description.  
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0007]      FIG. 1  is a partially schematic top view of an aircraft including an extendable leading edge adjacent to the fuselage and wings of the aircraft in accordance with an embodiment of the present invention.  
         [0008]      FIG. 2  is a partially schematic cross sectional view taken through section  2 - 2  of  FIG. 1 , illustrating a wing of the aircraft and a portion of the leading edge in a retracted position in accordance with an embodiment of the present invention.  
         [0009]      FIG. 3  is a partially schematic top view of the aircraft of  FIG. 1 , with the extendable leading edge in an extended position.  
         [0010]      FIG. 4  is a partially schematic cross sectional view taken through section  4 - 4  of  FIG. 3 , illustrating the extended position of the leading edge with respect to the wing.  
         [0011]      FIG. 5  is a partially schematic side view of an aircraft including an extendable leading edge of the fuselage and wings in a retracted position in accordance with an embodiment of the present invention.  
         [0012]      FIG. 6  is a partially schematic side view of the aircraft of  FIG. 5 , with the extendable leading edge in an extended position.  
         [0013]      FIG. 7  is a partially schematic front view of an aircraft including an extendable leading edge of the fuselage and wings in a retracted position in accordance with an embodiment of the present invention.  
         [0014]      FIG. 8  is a partially schematic front view of the aircraft of  FIG. 7 , with the extendable leading edge in an extended position.  
         [0015]      FIG. 9  is a partially schematic cross sectional view of an extendable leading edge having a concave rear contact surface in accordance with an embodiment of the present invention.  
         [0016]      FIG. 10  is a partially schematic cross sectional view of an extendable leading edge having a angled rear contact surface in accordance with an embodiment of the present invention.  
         [0017]      FIG. 11  is a partially schematic cross sectional view of an extendable leading edge having a generally parabolic contact surface in accordance with an embodiment of the present invention.  
         [0018]      FIGS. 12-14  are partially schematic cross sectional views of an aircraft wing including a Krueger flap and an extendable leading edge in accordance with an embodiment of the present invention. In  FIG. 12 , the Krueger flap is stowed and the leading edge is retracted. In  FIG. 13 , the Krueger flap remains stowed, but the leading edge is in an extended position. In  FIG. 14 , the Krueger flap is deployed and the leading edge is in the extended position. 
     
    
     DETAILED DESCRIPTION  
       [0019]      FIG. 1  is a partially schematic top view of an aircraft  10  including a fuselage  12  and wings  14 . The aircraft  10  has a nose section  16  and a tail section  18 . As used herein, the term “fuselage” includes the body of an aircraft as well as any structural features integrally formed with the body, such as strakes, leading edge extensions and the like which have leading edges. As shown in  FIG. 1 , an extendable leading edge in accordance with an embodiment of the present invention includes a portion  20   a  adjacent to the fuselage  12 , and portions  20   b  adjacent to the wings  14 . The leading edge  20   a ,  20   b  is extendable in a generally longitudinal direction of the aircraft.  
         [0020]      FIG. 2  is a cross sectional view of the wing  14  and leading edge  20   b , taken through section  2 - 2  of  FIG. 1 . In  FIGS. 1 and 2 , the leading edge  20   a ,  20   b  is in a retracted position. In the retracted position, the fuselage portion  20   a  of the leading edge is seated against the fuselage, and the wing portion  20   b  of the leading edge is seated against and contacts the wing  14 .  
         [0021]      FIGS. 3 and 4  are similar views as shown in  FIGS. 1 and 2 , respectively, except the leading edge  20   a ,  20   b  has been moved forward in the longitudinal direction of the aircraft to an extended position. The extended position of the wing portion of the leading edge  20   b  is shown in  FIG. 4 , which is a cross sectional view of the wing  14  taken through line  4 - 4  of  FIG. 3 . As shown in  FIG. 4 , the leading edge  20   b  is in a forwardly extended position a distance D away from the wing  14 . The fuselage portion  20   a  of the leading edge may also be forwardly extended a similar distance from the fuselage  12 .  
         [0022]     As can be seen most clearly in  FIGS. 1 and 3 , the wings  14  of the aircraft  10  have a sweep angle S W  measured from a transverse direction of the aircraft. As can also be seen in  FIGS. 1 and 3 , the fuselage  12 , including strakes and other structures having leading edges, may also have a sweep angle S F  measured from the transverse direction of the aircraft  10 . In the embodiment illustrated in  FIGS. 1 and 3 , the wing sweep angle S W  is different from the fuselage sweep angle S F , i.e., the wing sweep angle S W  is less than the fuselage sweep angle S F .  
         [0023]     In the embodiments shown in  FIGS. 1 and 3 , the wing sweep angle S W  remains constant along the wing  14 , and the fuselage sweep angle S F  remains constant along the fuselage  12 . However, the wing sweep angle S W  and/or the fuselage sweep angle S F  may vary. Accordingly, although constant wing and fuselage sweep angles S W  and S F  are shown in the present figures, any other desired wing and fuselage configuration may be used in accordance with the present invention.  
         [0024]      FIGS. 5 and 6  are partially schematic side views of an aircraft similar to that shown in  FIGS. 1 and 3 . In  FIG. 5 , the leading edge  20   a ,  20   b  is in the retracted position. In  FIG. 6 , the leading edge  20   a ,  20   b  is in the extended position.  
         [0025]      FIGS. 7 and 8  are partially schematic front views of an aircraft similar to that shown in  FIGS. 1 and 3 . In  FIG. 7 , the leading edge  20   a ,  20   b  is in the retracted position. In  FIG. 8 , the leading edge  20   a ,  20   b  is in the extended position.  
         [0026]     The leading edge  20   a ,  20   b  may be made of any suitable material. For example, the leading edge may comprise a substantially rigid material such as aluminum or conventional composite materials. The leading edge  20   a ,  20   b  preferably has no gaps detectable in the electromagnetic spectrum.  
         [0027]     The mechanism used to extend and retract the leading edge  20   a ,  20   b  may be any suitable linkage  28 , such as a conventional flap screwjack with extending rails to guide the extension. Any suitable controller for actuating the mechanism may be used, such as conventional manually operated controls or automatic controls for extending and retracting the leading edge based on airspeed.  
         [0028]      FIG. 9  is a partially schematic cross sectional view of the leading edge  20   b , which includes a front edge  21  and a rear contact surface  22 . In the embodiment shown in  FIG. 9 , the rear contact surface  22  has a concave shape which conforms with the front edge  15  of the wing  14 . Thus, the rear contact surface  22  and the front edge  15  are tightly seated against each other when the leading edge  20   b  is in the retracted position. This conforming arrangement of the rear contact surface  22  of the leading edge  20   b  and front edge  15  of the wing  14  can be seen in  FIGS. 2 and 4 .  
         [0029]     As shown in  FIGS. 2, 4  and  9 , the front edge  21  of the leading edge  20   b  may have a relatively pointed shape, while the rear contact surface  22  and front edge  15  of the wing  14  may have a relatively rounded shape. Thus, the front edge  21  of the leading edge  20   b  has a smaller radius of curvature than the front edge  15  of the wing  14 . This may be desirable in some aircraft because the rounder front edge  15  of the wing  14  may delay wing stall.  
         [0030]      FIGS. 10 and 11  illustrate alternative rear contact surface shapes of leading edges in accordance with embodiments of the present invention. In  FIG. 10 , the leading edge  23  has an angled contact surface  24 . In  FIG. 11 , the leading edge  25  has a generally parabolic contact surface  26 .  
         [0031]      FIGS. 12-14  illustrate an embodiment of the present invention in which a conventional Krueger flap  30  is rotatably mounted on the wing  14 . In  FIG. 12 , the leading edge  20   b  is in the retracted position, and the Krueger flap  30  is in the stowed position. In  FIG. 13 , the leading edge  20   b  is extended from the wing, while the Krueger flap  30  remains stowed. In  FIG. 14 , the leading edge  20   b  is extended and the Krueger flap  30  is rotated into a deployed position. Any known Krueger flap design and deployment mechanism may be used in accordance with this embodiment of the invention.  
         [0032]     Whereas particular embodiments of this invention have been described above for purposes of illustration, it will be evident to those skilled in the art that numerous variations of the details of the present invention may be made without departing from the invention as defined in the appended claims.
An extendable leading edge for the fuselage and wings of an aircraft is disclosed. The leading edge may be extended from a retracted position adjacent to the fuselage and wings to an extended position. In the extended position, the leading edge increases lift of the aircraft at low speeds. In the retracted position, gaps associated with the leading edge are avoided.