Patent Document

RELATED APPLICATIONS 
       [0001]    This application is a continuation application of U.S. patent application Ser. No. 11/047,194, filed 31 Jan. 2005, and entitled “High Lift Longitudinal Axis Control System,” which is incorporated herein by reference. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    This invention relates generally to the aviation industry and more specifically to a combination flap and aileron arrangement for improving flight performance at low air speeds. 
         [0003]    The desire to land at an airspeed as slow as possible while still maintaining adequate directional control is of ongoing concern in the aviation industry. The ability to maintain adequate airflow over flight control surfaces, such as the ailerons, during slow flight such as landing, increases the number of airports that can be used, but most importantly increases safety of operations. The development of efficient slow flight has included the use of highly cambered airfoils, hinged flaps, slots, spoilers, stall fences, and boundary layer controls devices such as vortex generators. The addition of one of these devices adds to the initial cost and ongoing maintenance cost of the aircraft, the addition of multiple of these devices geometrically increasing costs. The cost to benefit ratio limits the inclusion of these modalities on aircraft. 
         [0004]    It is well known that trailing edge flaps on aircraft wings improve performance of the aircraft, particularly in reducing landing speed when the flaps are adjusted to a position which increases wing camber. The highest flap utility is obtained when flaps are coextensive with the wing span. However, since ailerons are necessary to provide lateral control of the aircraft, the flap portion is typically shortened on each wing the amount necessary to accommodate the aileron. Various combinations have been devised endeavoring to maximize both flap and aileron efficiency, however none has been completely satisfactory. 
         [0005]    The present invention offers a solution to this problem. The device of the present invention endeavors to lower the stall speed while increasing aileron authority in a cost effective manner. The invention combines the additional lift and laminar flow provided by known Fowler-style flaps with the increased efficiency of known Frise-type ailerons. The unique combination of the present device enables the Frise type aileron component to create lift just as the wing does, and produces greater lateral effect with less deflection of the control. The present invention is further designed to decrease the wing tip vortices at slower speeds, allowing the control to be placed closer to the wing tip where it can also augment its effect through a longer moment arm with less deflection. 
       SUMMARY OF THE INVENTION 
       [0006]    The present invention relates to aircraft having one or more airfoils or wings including extensible flaps. A wing structure according to the invention includes a novel flap assembly that serves in several respects to improve the performance of an aircraft so fitted. The flap assembly of the present invention consists of a combination of interrelated airfoil elements, including flaps, which are arranged with respect to one another in various flight attitudes so as to give improved flight characteristics over known airfoils having flaps. 
         [0007]    In general, the shape of a typical subsonic airfoil is designed to produce a differential in air pressure between the upper and lower surfaces, with the upper surface being subjected to a pressure lower than that on the lower surface. This differential produces a net effect of the wing rising toward the area of lower pressure. The reduced pressure experienced by the upper surface is dependent upon laminar flow over the surface. If the airfoil angle of attack is increased or the airfoil curvature is increased, the flow of air near the airfoil trailing edge begins to separate and become turbulent. As the angle of attack and/or the curvature is increased, the point at which separation occurs moves forward on the airfoil, increasing the area of turbulence, until there is no differential in pressure between the upper and lower surfaces of the airfoil, and no lift. The present invention seeks to decrease the total area of turbulent air by augmenting laminar flow over the trailing edge of the airfoil during increased angles of attack and increased curvature by way of a combination of slotted flap and an integrated aileron assembly. 
         [0008]    The flap elements of the present invention are of the type which are generally movable rearwardly and downwardly to thereby form a gap or slot between the trailing edge of the main airfoil and the leading edge of the flap. The various elements of the present flap assembly are generally coextensive with main airfoil length and include an inboard flap portion and an outboard flap portion, the outboard portion being further fitted with an integrated aileron. 
         [0009]    The present invention provides an airfoil construction which includes the use of substantially full span flaps to thereby reduce the stalling, landing and take off speeds. The airfoil of the present invention further allows a more efficient aileron arrangement that permits maximum lateral control especially during slow airspeeds. 
         [0010]    More specifically, the present invention provides an airfoil equipped with a bipartite flap mechanism extending substantially the entire length of the main airfoil. A flap mechanism according to the present invention includes an inboard flap portion and an outboard flap portion whereby substantially the full length of the airfoil trailing edge may be utilized. The invention further integrates the aileron within the outboard flap portion. 
         [0011]    One aspect of the invention provides an airfoil comprising a trailing part and a full span, bipartite flap. The bipartite flap has a range of positions including an extreme retracted position and an extreme extended position, and the bipartite flap includes an inboard flap portion and an outboard flap portion. Each of the inboard flap portion and the outboard flap portion include a leading part and a trailing part. 
         [0012]    The outboard flap portion includes a flap member and an aileron member, the flap member having a flap member leading part and a flap member trailing part having a fixed distance therebetween. 
         [0013]    The aileron member is independently operable and pivotally mounted on the flap member trailing part, the aileron member including an aileron member leading part and an aileron member trailing part. 
         [0014]    The airfoil includes linkage extending from airfoil support structure to the outboard flap portion to translate the outboard flap portion between at least a first and a second position to create a functional slot between a bottom surface of the flap member leading part and a bottom surface of the airfoil trailing part to draw a portion of higher pressure air from the bottom surface of the airfoil through the functional slot to distribute the higher pressure air over a top surface of the outboard flap portion. 
         [0015]    The flap member trailing part of the outboard flap portion and all of the aileron member are adapted to be located aft of the airfoil trailing part when the bipartite flap is in an extreme retracted position. 
         [0016]    It is an object of the present invention to provide an airfoil for an airplane which will increase controllability and maneuverability of the airplane particularly in slow speed situations, without significantly increasing the complexity of design or execution of control. 
         [0017]    It is a further object to provide such an airfoil to new airplanes or to modify existing airplanes to improve their characteristics, as discussed above, without significantly increasing the weight or cost of the airplane. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0018]      FIG. 1  is a top plan view of an airplane with wings fitted with the flap combination of the present invention. 
           [0019]      FIG. 2  is a perspective view of an airplane wing fitted with the combination of the present invention and showing the flaps and aileron in retracted and neutral positions, with the airplane shown in phantom. 
           [0020]      FIG. 3A  is a cross section of the wing shown in  FIG. 2  and taken along lines  3 A- 3 A thereof, and showing the outboard flap portion. 
           [0021]      FIG. 3B  is a cross section of the wing shown in  FIG. 2  and taken along lines  3 B- 3 B thereof, and showing the inboard flap portion. 
           [0022]      FIG. 4A  is a perspective view of an airplane wing fitted with the combination of the present invention, similar to that of  FIG. 2 , but showing the inboard flap extended approximately 30°, the outboard flap extended approximately 22° and the aileron in neutral position. 
           [0023]      FIG. 4B  is a cross section of the wing shown in  FIG. 4A  and taken along lines  4 B- 4 B thereof. 
           [0024]      FIG. 5A  is a perspective view of an airplane wing fitted with the combination of the present invention, similar to that of  FIGS. 2 and 4A , but showing the inboard flap extended approximately 30°, the outboard flap extended approximately 22° and the aileron reflexed approximately 10°. 
           [0025]      FIG. 5B  is a cross section of the wing shown in  FIG. 5A  and taken along lines  5 B- 5 B thereof. 
           [0026]      FIG. 6A  is a perspective view of an airplane wing fitted with the combination of the present invention, similar to that of  FIGS. 2 ,  4 A, and  5 A but showing the inboard flap extended approximately 30°, the outboard flap extended approximately 22° and the aileron deflected downward approximately −10°. 
           [0027]      FIG. 6B  is a cross section of the wing shown in  FIG. 6A  and taken along lines  6 B- 6 B thereof. 
           [0028]      FIG. 7A  is a diagrammatic view of a typical wing/control structure and illustrating the separation point of laminar flow and resultant turbulent flow which replaces it adjacent the wing and flap. 
           [0029]      FIG. 7B  is a diagrammatic view illustrating the airflow adjacent the outboard flap and aileron combination of the present invention, with the position of adjustment as shown in  FIGS. 4A and 4B . 
           [0030]      FIG. 8  is a partially cut away view of an airplane wing fitted with the combination of the invention and showing a preferred activating system. 
           [0031]      FIG. 9  is a partially cut away view of an airplane wing fitted with the combination of the invention and showing an alternative activating system. 
       
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0032]    Although the disclosure hereof is detailed and exact to enable those skilled in the art to practice the invention, the physical embodiments herein disclosed merely exemplify the invention which may be embodied in other specific structures. While the preferred embodiment has been described, the details may be changed without departing from the invention, which is defined by the claims. 
         [0033]      FIG. 1  of the drawings illustrates an airplane  10  having a fuselage  12  and wing structure comprising a right wing structure  14 A and a left wing structure  14 B. The main airfoil of each wing structure  14 A,  14 B is designated by the numeral  16 . 
         [0034]    Each of the main airfoils  16  includes a leading edge  18  and a trailing edge  20 . Each wing structure  14 A,  14 B further preferably includes an inboard flap portion  22  and an outboard flap portion  24 , each of the flap portions  22 ,  24  having a flap leading edge  26 A,  26 B, respectively, and a flap trailing edge  28 , with the respective flap leading edges  26 A,  26 B each being located adjacent the airfoil trailing edge  20 . Each flap leading edge  26 A,  26 B is preferably capable of movement with respect to its respective flap trailing edge  28 . As seen, the outboard flap portion  24 , is preferably comprised of a flap member  29  having an aileron  30  pivotally mounted on its flap member trailing edge  27 . 
         [0035]    As may be seen particularly in the views of  FIGS. 2 ,  3 A, and  3 B, the inboard flap portion  22  is preferably comprised of a fowler-style flap and is so mounted on each respective main airfoil  16  such that it is rotatable over a limited arcuate range on a spanwise axis, and may be projected fully rearwardly to an extended position as shown in  FIGS. 4A and 6A . As may be seen in  FIG. 4A , when the inboard flap  22  is projected rearwardly and downwardly a slot  32  is provided between the trailing edge  20  of the main airfoil  16  and the flap leading edge  26 A. The outboard flap portion  24  is preferably comprised of a flap member  29  and an inset aileron member  30 , such as the Frise-style aileron shown. It is to be understood that while Frise-style ailerons are preferred to thereby minimize adverse yaw and the need for differential deflection of ailerons, other known aileron types may be used. The present arrangement provides maximum lift coefficient while maintaining aileron control at lower speeds. 
         [0036]    As may be seen particularly in the views of  FIGS. 4B ,  5 B, and  6 B, during outboard flap  24  extension a secondary slot  34  is formed between the flap leading edge  26 B and the trailing edge  20  of the main airfoil  16 . As illustrated particularly in the view of  7 B, and as discussed above, the secondary slot  34  functions, similarly to that of slot  32 , to draw a portion of higher pressure air from the bottom surface  36  of the airfoil  16 , through the secondary slot  34  and distribute it in laminar flow over the top surface  38  of the outboard flap portion  24 , consisting of flap member  29  with its integrated aileron  30 . This action thereby augments the laminar air flow of the total wing structure  14 A,  14 B and increases the net lift of the wing structure  14 A,  14 B through the contribution of lift exerted by the outboard flap portion  24  including the flap member  29  and its integrated aileron  30 . This effect is contrasted with the conventional wing  40  illustrated in  FIG. 7A . As may be seen, lift is generated forward of the separation point  42 , with the trailing edge  44  of the wing structure  40  and the aileron  46  unable to contribute to the overall lift of the wing structure  40  due to the area of turbulence  48  located adjacent those structures. It is to be noted that in addition to the benefits previously discussed, the present arrangement minimizes aileron  30  deflection and size, since laminar airflow is maintained over a substantial area of the aileron  30  surface, allowing it to produce a net moment by means of both displacement and lift. Additionally, general control efficiency is enhanced, since the adverse effect of wing tip vortices at high angles of attack is reduced. 
         [0037]    Illustrated in  FIG. 8  is a preferred manner in which the flap system of the present invention is mounted on the wing structure  14 A,  14 B and operated. As seen, a linear actuator  50 , including a jackscrew  52  motivated by a prime mover, such as the electric motor  54  shown, is ultimately activated by conventional pilot control means. The actuator  50  is connected to a cable  56 , movement of which ultimately moves both inboard flaps  22  and outboard flap members  29 , respectively. The cable  56  is supported by idler pulleys  58  and a drive pulley  60 . The drive pulley  60  is further attached to a bellcrank  62  having arms  64 A,  64 B. Rotation of the drive pulley  60  moves the bellcrank arms  64 A,  64 B and their pivot pins  66 A,  66 B. Attached to each bellcrank arm  64 A and its respective pivot pin  66 A is the first end  68  of linkage arm  70 . The second ends  72  of each linkage arm  70  are conventionally pivotally attached to a respective leading edge  26 A,  26 B of the outboard flap member  29  or inboard flap  22 . The bellcrank arms  64 B are each pivotally attached to an axially reciprocating moveable rod  74 , which extends substantially spanwise of the wing structure  14 A,  14 B. Outboard flap member  29  and inboard flap  22  move in accordance with the contour of cammed internal flap tracks  76 , shown. It is to be understood that although conventional internal flap tracks  76  are shown in this view, in some applications, the invention contemplates the use of external linkage operated flaps tracks (not shown). The aileron member  30  of the present invention is conventionally moved independently by push pull tubes  78  and is operated by the pulley system A, shown in  FIG. 8 , or other known means. 
         [0038]      FIG. 9  illustrates an alternative operational system for the present invention, in which the bellcrank  62  and pulley  58 ,  60  flap drive mechanism shown in  FIG. 8  has been replaced by a torque tube drive system B. The torque tube drive system B preferably utilizes a prime mover, such as the motor  54  shown in phantom. 
         [0039]    It is to be understood that the right wing structure  14 A on the right side of the plane has similar and similarly mounted and related parts. 
         [0040]    The foregoing is considered as illustrative only of the principles of the invention. Furthermore, since numerous modifications and changes will readily occur to those skilled in the art, it is not desired to limit the invention to the exact construction and operation shown and described. While the preferred embodiment has been described, the details may be changed without departing from the invention, which is defined by the claims.

Technology Category: 7