Abstract:
A mobile platform lift increasing system includes at least one wing-shaped structure having a leading edge, a trailing edge and a chord length perpendicularly measurable between the leading and trailing edges. A rotatable control surface is located near a trailing edge undersurface. The control surface length is approximately one to five percent of the chord length. A deployment device is positioned between the wing shaped structure and the control surface. The deployment device operably rotates the control surface through a plurality of positions ranging between an initial position and a fully deployed position. Wing lift is increased at speeds up to approximately transonic speed by continuously rotating the control surface to accommodate variables including mobile platform weight change from fuel usage.

Description:
FIELD OF THE INVENTION 
   The present invention relates generally to lift producing aerodynamic surfaces and more specifically to the trailing edge geometry of lift producing aerodynamic surfaces. 
   BACKGROUND OF THE INVENTION 
   The lift producing structures such as wings, winglets, horizontal tails, canards etc. (hereinafter referred to as “wings”) for an aircraft or any mobile platform, commonly have an airfoil shape which includes a rounded nose, a relatively thick forward cross section, a tapering section, and a relatively thin trailing edge cross section. Aircraft wings commonly include ailerons and/or flaps to modify airflow over the wing to change the aircraft attitude or to increase lift for take-off and landing procedures, respectively. Ailerons and flaps are typically a significant percentage (i.e., approximately 15% and 35%, respectively), of an aircraft wing chord (the forward to aft length of a wing), and limited in spanwise extent so are therefore not efficient for optimizing wing span load distributions during flight to maximize aircraft performance. 
   It is known that the area adjacent to the trailing edge can be modified to include fixed wedge-shape devices or fixed extended flaps to improve lift and reduce the coefficient of drag for the wing. These fixed devices commonly have a length of approximately 5% of the wing chord. The addition of these devices can increase fuel efficiency at normal operating speeds of the mobile platform. The use of these devices, however, results in increased drag when operating outside the normal operating speed, because the fixed angle that the device makes from the plane of the trailing edge of the wing is optimized for the normal cruise speed, and therefore provides a less than optimum angle for operation at other than normal cruise speeds. 
   One known solution to the fixed flap design is to interlock a set of rotatable ribs to define the chord of an aircraft wing. The plurality of ribs are each rotatable such that the overall geometry of the wing can be modified during flight. In operation, either the entire wing deflects or a portion of the wing having one or more ribs deflects. The disadvantage of this design is the tradeoff between the additional weight required for the additional mechanical devices to modify the wing shape with the increased efficiency of the wing. 
   It is therefore desirable to overcome the disadvantages and drawbacks of the known airfoil designs having fixed trailing edge geometries or multiple articulated wing sections. 
   SUMMARY OF THE INVENTION 
   According to a preferred embodiment of the present invention, a lift producing system for a mobile platform includes at least one wing-shaped structure having a leading edge, a trailing edge and a chord length measurable between the leading and trailing edges. At least one control surface is rotatably disposed approximate the trailing edge. The control surface has a length approximately one to five percent of the chord length. A deployment device is disposed between the wing-shaped structure and the control surface. The deployment device is operable to rotate the control surface through a plurality of positions ranging between an initial position approximately parallel to the wing-shaped structure and a fully deployed position. 
   According to another preferred embodiment, the control surface includes a forward facing edge forming an axis of rotation for the control surface, and a distally extending edge. A mechanical deployment device is disposed between the wing shaped structure and the control surface which is operable to declinate the control surface about the axis of rotation from an initial position having the control surface approximately parallel to the wing, to a deployed position, and returning the control surface to the initial position. 
   In still another preferred embodiment, the deployment device includes a fluid actuator having flexible walls. A pressurized fluid is pumped or input into the fluid actuator, expanding the fluid actuator to declinate a control surface over a variable operating range. Removing fluid from the fluid actuator returns the control surface to the initial position. 
   In yet another preferred embodiment of the present invention, the control surface is provided of a flexible, elastic material. This design provides a curved surface shape as the control surface is deployed. 
   Further areas of applicability of the present invention will become apparent from the detailed description provided hereinafter. It should be understood that the detailed description and specific examples are intended for purposes of illustration only and are not intended to limit the scope of the invention. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The present invention will become more fully understood from the detailed description and the accompanying drawings, wherein: 
       FIG. 1  is a plan view of a common two engine commercial aircraft having the main flight wings modified to incorporate the variable trailing edge geometry of the present invention; 
       FIG. 2  is a partial cross section view taken at Section  2  of  FIG. 1  showing a potential range of motion for a control surface of the present invention; 
       FIG. 3  is a modification of the plan view of  FIG. 1  showing a canard wing installed on an aircraft, and includes an arrangement of four control surfaces of the present invention deployed on each main wing; 
       FIG. 4  is a sectioned elevation view taken at Section  4  of  FIG. 3  showing a control surface in an initial position fully upright against the trailing edge of the wing; 
       FIG. 5  is a sectioned elevation view taken at Section  5  of  FIG. 3  showing a control surface in a partially declinated position; 
       FIG. 6  is sectioned elevation view taken at Section  6  of  FIG. 3  showing a control surface in an intermediate position; 
       FIG. 7  is a sectioned view taken at Section  7  of  FIG. 3  showing a control surface in a normal deployed position for maximum load increase on the wing surface; 
       FIG. 8  is the sectioned elevation view of  FIG. 4  modified to show the control surface in the normal deployed position; 
       FIG. 9  is the sectioned elevation view of  FIG. 5  modified to show the control surface in an intermediate declinated position; 
       FIG. 10  is the sectioned elevation view of  FIG. 6  modified to show the control surface in a partially declinated position; 
       FIG. 11  is the sectioned elevation view of  FIG. 7  modified to show the control surface in the initial or fully upright position adjacent to the wing structure; 
       FIG. 12  is a sectioned view similar to  FIG. 2  showing an alternate embodiment actuator of the present invention; 
       FIG. 13  is a partial cross section view of an aircraft wing identifying an alternate embodiment of a flexible control surface of the present invention; and 
       FIG. 14  is a diagrammatic presentation of the method steps to vary an airfoil trailing edge geometry according to the present invention. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   The following description of the preferred embodiment(s) is merely exemplary in nature and is in no way intended to limit the invention, its application, or uses. Reference to use on an aircraft wing is generally made herein, however, the invention is not limited to aircraft or wing use. 
   Referring to  FIG. 1 , a variable trailing edge system  10  in accordance with a preferred embodiment of the present invention is shown. An aircraft  12  includes a starboard wing  14  and a port wing  16 . Each of the wings include a leading edge  18  and a trailing edge  20 . A chord length  22  is identified for the port wing  16 , but is common to either wing. A plurality of chord lengths  22  can exist for a given wing because the chord length  22  is determined at a cross section taken through the wing, and the tapering wing design of many commercial aircraft (such as the 2-engine design shown in  FIG. 1 ) provides a changing cross section as the wing tapers down in length from the inboard end to the outboard end. Common aircraft wings also include at least one aileron  24  and at least one flap  26 . 
   Each of the starboard wing  14  and the port wing  16  are connected to the aircraft  12  at a side-of-body  28 . In the configuration shown in  FIG. 1 , the wings taper from the side-of-body  28  to a wing tip  30 . A control surface area  32  is shown for the starboard wing  14 . The control surface area  32  represents the location on the starboard wing  14  adjacent to the trailing edge  20  having at least one individual control surface  34  of the present invention disposed thereon at an undersurface of the trailing edge  20 . In a preferred embodiment, a plurality of individual control surfaces  34 , i.e, those shown at an aft facing edge of the port wing  16  and having a length “L”, are disposed on an aircraft wing. Each of the individual control surfaces  34  can be operated in tandem or can be operated individually as will be described further herein. One or more individual control surfaces  34  are disposed within each of the variable trailing edge regions “A” and “B”. In a preferred embodiment, the control surfaces are disposed from the wing tip  30  to a position spaced outboard from the side-of-body  28  for each of the starboard wing  14  and the port wing  16 . The control surfaces can also be positioned adjacent to the side-of-body  28 , depending on wing structure and amount of wing load desired. 
   The aircraft  12  also includes a horizontal stabilizer  36  attached to an aft end of a fuselage  36 . Control surfaces of the present invention can also be disposed on the horizontal stabilizer  36  in similar positions adjacent to the trailing edge of the horizontal stabilizer. The greatest wing load benefit using control surfaces of the present invention, however, is achieved when the control surfaces are disposed at the positions shown on the starboard wing  14  and the port wing  16 , respectively. 
   Operational control of the individual control surfaces  34  of the present invention is preferably performed using a computer  39 . The computer  39  collects platform data including the remaining on-board fuel, passenger weight, air speed, altitude, and baggage weight, etc. The computer  39  is pre-programmed to vary the declination angle of each individual control surface  34  to adjust an overall wing aerodynamic load distribution for both wings based on flight conditions, current aircraft weight and structural limits. The computer  39  directs the operation of hydraulic or air systems (not shown) to position each individual control surface  34 . Hydraulic and air systems are commonly known and are therefore not further discussed herein. It is preferable to operate the individual control surfaces “automatically” using the computer  39 , wherein continuous or intermittent calculations of the computer  39  signal either continuous or intermittent position changes to the actuators (discussed in reference to  FIG. 2 ) of the individual control surfaces  34 . In the event of a power failure or computer failure, it is also desirable for the actuators to return the control surfaces  34  to a safe (low wing bending moment) position. 
   Referring now to  FIG. 2 , one of the individual control surfaces  34  of the port wing  16  is further detailed. The individual control surface  34  is disposed adjacent to the trailing edge  20  such that the individual control surface  34  is positioned below a wing upper surface  40  and generally parallel with a wing lower surface  42 . The individual control surface  34  is rotatably hinged to the wing lower surface  42  at a control surface connection end  44 . A control surface distal end  46  is positioned immediately adjacent to the trailing edge  20  in a fully upright position of the individual control surface  34 . An exemplary actuator  48  having a worm drive gear  50  is connectably disposed to the individual control surface  34  and fixedly disposed at the wing upper surface  40 . The actuator  48  rotates and guides the worm drive gear  50  such that the individual control surface  34  rotates about the control surface connection end  44  between a control surface initial position  52  through a varying degree of declination positions. 
   From the control surface initial position  52 , several exemplary positions are illustrated. A control surface intermediate position  54  having an angle θ is shown. A control surface deployed position  56  having an angle φ is also shown. The control surface deployed position  56  represents a normal operating declination position for the control surface  34 . The deployed position  56  is predetermined for an individual aircraft depending upon the wing load desired and the normal operating speed of the aircraft  12 . A control surface maximum deployed position  58  having an angle β is also shown. The control surface maximum deployed position  58  can be as high as approximately 90 degrees measured from the control surface initial position  52 . The control surface maximum deployed position  58  generates a maximum lift from any one of the individual control surfaces  34 . During normal operation of the aircraft, the control surface deployed position  56 , or normal operating range for the individual control surface  34 , has an angle φ of approximately 15-25 degrees measured from the control surface initial position  52 . The spanwise distribution of angle φ represents the optimum operating angle positions to reduce an aircraft fuel consumption rate without exceeding structural limits. This optimum distribution varies over the course of the flight as fuel is consumed. 
   As best shown in  FIG. 3 , the variable trailing edge system of the present invention can also be disposed on a canard wing  60 . The canard wing  60  includes a starboard control surface  62  and a port control surface  64 . Each of the starboard control surface  62  and the port control surface  64  can include one or more individual control surfaces (e.g., individual surfaces  34  as noted previously in reference to FIG.  1 ). 
   As best described with reference to  FIGS. 4-11 , individual chord lengths taken through the port wing  16  demonstrate exemplary operating ranges for individual control surfaces of the present invention.  FIG. 4  typifies a chord  22  measurable between the leading edge  18  and the trailing edge  20 . The wing upper surface  40  and the wing lower surface  42  are also shown representing the typical airfoil shape of an aircraft&#39;s wing. 
     FIGS. 4-7  demonstrate several exemplary positions for control surfaces for an aircraft during an in-flight condition wherein the weight of the aircraft decreases from its maximum takeoff weight and a modified induced wing load is desirable. To optimize wing load distribution during in-flight conditions, a first control surface  66  closest to the side-of-body  28  is in a fully upright or initial position  68 . A second control surface  70  adjacent to the control surface  66  is in a deployment position  72 . A third control surface  74  is in a deployment position  76 . A fourth control position  78  is in a normal deployment position  80  corresponding to the control surface deployed position  56  identified in FIG.  2 .  FIGS. 4-7  provide an exemplary configuration of control surfaces during an in-flight condition. The wing load distribution is optimized by deployment of individual control surfaces  66 ,  70 ,  74  and  78  as shown having the control surfaces adjacent to the wing tip  30  at the maximum deployed (i.e., declinated) position and each control surface from the wing tip  50  inboard positioned at a decreasing angle of deployment. 
   Referring now to  FIGS. 8-11 , an exemplary takeoff condition for an aircraft wing is shown. In the takeoff condition, the aircraft is at its maximum weight due to maximum passenger, baggage, and fuel volumes. For the takeoff condition, the individual control surfaces are positioned opposite to the control surface positions for the aircraft wing during in-flight conditions. Therefore, in  FIG. 8 , the first control surface  66  is deployed in a normal deployment position  80  corresponding to the control surface deployed position  56  of FIG.  2 . Each further outboard control surface has a decreasing declination angle, until, at the fourth control surface  78 , the deployment position equates to the initial position  68 . The second control surface  70  (shown in  FIG. 9 ) is therefore positioned in the deployment position  76  and the third control surface  74  (shown in  FIG. 10 ) is positioned in the deployment position  72 . In the exemplary condition shown in  FIGS. 8-11 , outboard wing loading is reduced and lift generated by the inboard control surfaces is increased, reducing the wing root-bending moment when the aircraft is at its maximum weight. 
   Referring to both  FIGS. 1 and 4 , in one preferred embodiment of the present invention, the individual control surfaces  34  have the length “L” for each application. The length “L” varies depending upon the wing load desired, between approximately 1% to approximately 5% of the chord  22  length. In a further preferred embodiment of the present invention, the length “L” can also vary for each individual control surface  34  for a given wing. The length “L” can also vary based on the projected platform operating speed. 
   As shown in  FIG. 12 , another preferred embodiment for actuating a control surface of the present invention is shown. A fluid actuator  82  is disposed between the wing upper surface  40  and the individual control surface  34 . The fluid actuator  82  includes a flexible wall  84  containing a fluid such as air or hydraulic fluid (not shown) which is pumped or otherwise input into the fluid actuator  82  to expand the fluid actuator in the deployment direction “C”. This fluid is removed from the fluid actuator  82  through one or more bleed devices (not shown) to retract the individual control surface  34  from the normal deployment position  36  to the control surface initial position  88 . Similar to the actuator  48  shown in  FIG. 2 , the fluid actuator  82  causes the individual control surface  34  to rotate about a rotation axis  90 . The rotation axis  90  is provided by a hinge or similar device disposed in the wing. 
   Referring next to  FIG. 13 , yet another preferred embodiment of the present invention having a flexible control surface  100  is detailed. The flexible control surface  100  includes a fixed end  102  and a distal end  104 . The flexible control surface  100  is made from an elastic material such that after the deflection force is removed, the control surface  100  returns to its normal non-deflected position. In operation, the flexible control surface  100  is positioned in a similar manner to the individual control surfaces  34  with actuators (not shown) similar to the actuator  48  or the fluid actuator  82 . 
   From an initial position  106 , the flexible control surface  100  deflects about a range of bend radii “D” to various operating positions. In a first rotation position  108 , the flexible control surface  100  includes a bend radius D′. In a second rotation position  110 , the flexible control surface  100  includes a bend radius D″. In third rotation position  112 , the flexible control surface  100  includes a bend radius D′″. Finally, in the deployed position  114 , the flexible control surface  100  has a bend radius D″″. It will be evident to a skilled practitioner that the flexible control surface  100  can have a plurality of rotation positions and bend radii. The flexible control surface  100  provides a smoother transition surface area for airflow compared to the rigid plate surface of the individual control surface  34  (shown in FIG.  2 ). The fixed end  102  of the flexible control surface  100  is preferably provided as a fixed attachment to the wing structure. The fixed end  102  of the flexible control surface  100  can also be hinged similar to the individual control surface  34 . 
   Referring to  FIG. 14 , the method steps to operate a wing trailing edge control surface of one preferred embodiment the present invention are described. In a step  120 , a wing control surface adjacent to a trailing edge of a wing is rotatably disposed to the wing. At a step  122 , a wing control surface rotation path is defined varying from an initial position to a deployed position. In a following step  124 , one or more mobile platform operating conditions define a declination angle of the wing control surface. In a first parallel step  126 , a mobile platform fuel usage rate is calculated using a computer. In a following step  128 , a wing aerodynamic load distribution is optimized to increase aerodynamic efficiency by taking advantage of increased structural margins which correspond to a decreasing fuel weight. In a second parallel step  130 , the wing control surface is adjusted in one of a failure mode and an automatic optimization mode. In a third parallel step  132 , the wing control surface is adjusted to a structurally safe position during a failure mode. 
   The variable trailing edge system of the present invention offers several advantages. The individual control surfaces of the present invention can be individually actuated or group actuated to adjust the structural load of an aircraft wing. A plurality of actuator designs can be used to actuate the control surfaces. The control surfaces of the present invention can vary in length between approximately 1% to approximately 5% of the chord length of the wing. The control surfaces can also vary along the span of each wing. By controlling the declination angle of the control surfaces of the present invention, aircraft flight conditions such as decreasing weight due to fuel usage can be compensated for. As the aircraft weight decreases in flight, the outboard wing load can be increased using the control surfaces of the present invention and an overall fuel consumption for the aircraft can be reduced. 
   The description of the invention is merely exemplary in nature and, thus, variations that do not depart from the gist of the invention are intended to be within the scope of the invention. Such variations are not to be regarded as a departure from the spirit and scope of the invention.