Patent Publication Number: US-9889922-B2

Title: Flap support

Description:
RELATED APPLICATIONS 
     The present application is a continuation of U.S. application Ser. No. 13/633,976, filed Oct. 3, 2012, which is based on, and claims priority from, British Application Number 1117340.8, filed Oct. 7, 2011, the disclosures of which are hereby incorporated by reference herein in their entirety. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates to a flap support structure for an aircraft wing having a trailing edge flap. 
     BACKGROUND OF THE INVENTION 
     Aircraft typically include flaps attached to the wing fixed trailing edge which are movable between extended and retracted positions with respect to the fixed wing. Extension of the flaps increases the lift coefficient of the wing for the high lift, low speed flight phases (e.g. take-off and landing). 
     There are a wide variety of flap designs (e.g. single and multiple flap elements, slotted, unslotted etc.) and flap actuation mechanisms (e.g. drop hinge, flap track etc.) to achieve a similarly wide variety of extended flap configurations and motion paths. Generally, the flap extension path includes at least some aft movement and/or downward rotation of the flap element(s). The aft movement increases the wing chord, whilst the downward rotation increases the wing camber. 
     The flaps may be movable between a retracted position and one or more extended positions for low speed flight. During high speed flight phases it is also known to adjust the position of the flaps by small angles (+/−10 degrees, approx.) to vary the wing camber according to the cruising speed; so-called adaptive camber wings. 
     Depending on the flap geometry and desired motion path it is sometimes possible to house the flap actuation mechanism and the flap hinge wholly within the wing profile. However, it is common, particularly with more complex flap deployment geometry, to support the flap from the wing using a flap support structure. The flap support structure generally includes a flap support beam which houses at least a portion of the flap deployment mechanism for moving the flap, and has an outer aerodynamic fairing to reduce drag. 
     Existing flap support structures tend to be relatively complex and heavy, leading to an increase in manufacturing cost and assembly time, increased maintenance cost and time, and in-service fuel costs due to the weight penalty. They also tend to have a relatively large sectional area which impacts upon drag and hence in-service fuel costs. 
     SUMMARY OF THE INVENTION 
     A first aspect of the invention provides a flap support structure for an aircraft wing having a trailing edge flap, the flap support structure comprising: a flap support beam including an aerodynamic fairing; and a drive unit including a universal support structure which rotatably receives a drive shaft connected to a drive arm for moving the trailing edge flap, wherein the universal support structure also forms part of the flap support beam and supports the aerodynamic fairing. 
     A further aspect of the invention provides an aircraft wing having a trailing edge flap supported from the aircraft wing by a flap support structure according to the invention. 
     The invention is advantageous in that the universal support structure forms part of both the drive unit and the support beam. This reduces parts count for the flap support structure, enables a modular assembly which reduces installation time, provides more efficient power transfer for moving the flap and easier adjustment of flap kinematic components. 
     The drive unit may further comprise an actuator mounted to the universal support structure and coupled to the drive shaft. The actuator may be removable from the drive shaft. 
     The drive unit may be mounted to an upper portion of the universal support structure which projects beyond the aerodynamic fairing, for positioning within a trailing edge region of the aircraft wing. In this way it becomes possible to house the drive unit partially within the fairing and partially within the wing trailing edge region. Positioning the actuator of the drive unit within the wing trailing edge region may beneficially be used to achieve a narrow flap support fairing with low drag. 
     The flap support beam may be configured to be supported by the aircraft wing by mounting means provided on the universal support structure. The mounting means may be provided on an upper portion of the universal support structure which projects beyond the aerodynamic fairing. These mounting means may include bearings for receiving a pin, and in particular may include spherical bearings for ease of alignment during fitting of the flap support beam to the aircraft. 
     The drive arm may be curved so as to avoid clashing with the pin of the mounting means. Alternatively, the drive arm may be substantially straight. 
     The drive arm may be fixed in rotation with respect to the drive shaft to provide a direct drive. 
     Preferably, the drive arm is a failsafe drive arm. The failsafe drive arm may include a primary arm and a secondary arm. 
     The aerodynamic fairing is preferably a structural fairing, and the flap support beam may further comprise a plurality of diaphragms for supporting the aerodynamic fairing. The flap support beam may be constructed as a modular component. 
     The universal support structure may be disposed approximately centrally along the length of the flap support beam. The flap support beam may have its maximum width substantially adjacent the universal component. 
     The aerodynamic fairing preferably has a generally U-shaped section. The flap support beam may further comprise one or more structural covers spanning between free edges of the U-shaped fairing. The covers may feature weight saving cut-outs. 
     The flap support structure may further comprise a linkage arrangement for coupling the trailing edge flap to the flap support beam. The linkage arrangement is preferably a four-bar linkage. 
     The four-bar linkage may include: a ground link comprising the flap support beam; a first grounded link comprising the drive arm which is pivotally connected at one end to the flap; a second grounded link comprising a rear link which is pivotally connected at one end to the flap and is pivotally connected at its other end to the aft end of the flap support beam; and a floating link comprising the flap. 
     The flap support beam may be mounted to the aircraft wing by a forward fitting and an aft fitting. Additional fittings may be provided as required. However, the provision of two fittings, fore and aft, has advantages for ease of assembly and removal of the flap support. 
     In one example, the aft fitting may include an aft pin coupling the universal support structure of the flap support structure to one or more aft brackets mounted on the wing. The aft brackets may be mounted on the wing fixed trailing edge on either side of the universal support structure. The aft pin preferably extends through the universal support structure and projects from either side thereof. 
     The forward fitting may include a forward pin coupling the flap support structure to one or more forward brackets mounted on the wing. The forward brackets may be mounted on the underside of the wing. The forward pin may be provided as a spigot projecting forwardly from the flap support beam. 
     The forward and/or aft fittings are preferably failsafe fittings. Each of the failsafe fittings may include a plurality of brackets and/or a failsafe pin. 
     The flap support beam may be accompanied by a forward non-structural aerodynamic fairing forward of the flap support structure, and an aft non-structural aerodynamic fairing aft of the flap support structure, wherein outer surfaces of the forward and aft non-structural fairings blend smoothly with an outer surface of the structural fairing of the flap support structure. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Embodiments of the invention will now be described with reference to the accompanying drawings, in which: 
         FIG. 1  illustrates a side view of a commercial passenger jet aircraft; 
         FIG. 2  illustrates a plan view of the aircraft of  FIG. 1 ; 
         FIG. 3  illustrates a partially cut away view of the aircraft wing trailing edge showing the flap support structure with the flap in an extended position; 
         FIG. 4  illustrates a partial side section view of the wing trailing edge with the flap retracted; 
         FIG. 5  illustrates a wire frame view of the wing trailing edge with the flap a) retracted, b) partially extended, and c) fully extended; 
         FIG. 6  illustrates a three dimensional view of part of the flap support structure showing the flap support beam, drive unit and forward and aft aircraft fittings; 
         FIG. 7  illustrates an exploded three dimensional view of the flap support beam; 
         FIG. 8  illustrates a partially cut away view of the wing fixed trailing edge showing the forward and aft aircraft fittings; 
         FIG. 9  illustrates the drive unit pinned to the aft aircraft fitting; 
         FIG. 10  illustrates a partially cut away view of the flap support beam forward spigot for attachment to the forward aircraft fitting; and 
         FIG. 11  illustrates assembly of the flap and its support structure to the aircraft wing. 
     
    
    
     DETAILED DESCRIPTION OF EMBODIMENT(S) 
       FIGS. 1 and 2  illustrate side and plan views, respectively, of an aircraft  1  having a fuselage  2 , wings  3  and under-wing mounted engines  4 . The wing  3  has moveable trailing edge flaps  5  mounted to the wing fixed trailing edge. The flaps  5  are supported by and moveable with respect to the fixed portion of the wing  3  by flap support structures  6 . Whilst the aircraft shown in  FIG. 1  is a commercial transport aircraft, the invention is applicable to a wide variety of aircraft types. It is also applicable to aircraft with engines mounted other than under the wing, e.g. aft mounted engines. 
       FIG. 3  illustrates a partially cut away view of the trailing edge of the wing  3  showing the flap support structure  6  with the flap  5  in an extended position. The wing  3  includes an upper wing cover  7 , a lower wing cover  8  and a rear spar  9  which form part of a wing box structure for supporting the wing. 
     The flap support structure  6  generally includes a flap support beam  10 , a fixed forward fairing  11  and a moveable aft fairing  12 . The forward fairing  11  is fixed with respect to the fixed portion of the wing  3 . The aft fairing  12  is fixed with respect to the flap  5  and moves with the flap  5  between a retracted position adjacent the wing fixed trailing edge and one or more extended positions. 
     A drive unit  13  for moving the flap is disposed adjacent the rear spar  9  and is partially housed within the flap support beam  10  with the remainder being housed within the wing trailing edge region. A linkage mechanism  14  is coupled between the flap  5 , the flap support beam  10 , and the drive unit  13  such that the drive unit  13  moves the flap  5  between its extended and retracted positions. 
       FIG. 4  illustrates the aircraft wing trailing edge with the flap  5  in its retracted position in which the flap  5  is nested within the aerofoil profile of the wing  3 . 
       FIG. 5  illustrate wire frame images of the flap  5  and the flap support structure  6  with the flap a) retracted, b) partially extended, and c) fully extended. From the wire frame images the linkage arrangement  14  can more easily be seen. The linkage arrangement  14  is a so-called “four-bar linkage”, or simply “four-bar”, which includes the following main linkage elements: “ground link”, first and second “grounded links”, and “floating link”. The basic features of a generic four bar linkage are very well known in the art, and so will not be described in detail here. 
     The “ground link” comprises the flap support beam  10 . The “first grounded link” comprises a drive arm  14   a  which is coupled and fixed at one end in rotation with respect to a drive shaft of the drive unit  13 . The other end of the drive arm  14   a  is pivotally connected to the flap  5  by a fixed flap linkage  14   b  extending from the underside of the flap aerofoil element. The “second grounded link” comprises a rear link  14   c , which is pivotally connected at one end to the flap  5  by a bracket extending from the underside of the flap aerofoil element adjacent its trailing edge, and is pivotally connected at its other end to the aft end of the flap support beam  10 . Finally, the “floating link” comprises the flap  5  itself. 
     As can be seen form  FIG. 5 , the drive arm  14   a  is moveable between a first position and a second position corresponding to retracted and fully extended positions of the flap  5 , and passes “over centre” where the pivotal connection between the drive arm  14   a  and the fixed flap linkage  14   b  reaches its lowest point within the flap support beam  10 . The aft link  14   c  is moveable between a first position where its longitudinal axis is aligned generally vertically (substantially perpendicular to the aircraft fore-aft direction) to a second position where it is aligned generally horizontally (substantially parallel with the aircraft fore-aft direction). The first and second positions of the aft link  14   c  corresponding to retracted and fully extended positions of the flap  5 . 
       FIG. 6  illustrates a three-dimensional view of part of the flap support structure  6  showing the flap support beam  10 , the drive unit  13 , a forward aircraft fitting  15  and an aft aircraft fitting  16 . The flap support beam  10  has a modular structure so as to reduce assembly and disassembly time for attaching the flap  5  and flap support structure  6  to the aircraft wing  3 . 
     With reference to the exploded three-dimensional view shown in  FIG. 7 , the flap support beam  10  includes a generally U-shaped structural aerodynamic fairing  17 , a universal support structure  18  and a plurality of diaphragms  19   a - d  spaced along the length of the fairing  17 . The universal support structure  18  is disposed substantially centrally along the length of the fairing  17  and is fixed to the interior surface of the fairing  17 . Diaphragms  19   a  and  19   b  are positioned forward of the universal support structure  18  and diaphragms  19   c  and  19   d  are positioned aft of the universal support structure  18 . 
     The diaphragms  19   a - d  are each fixed to the interior surface of the fairing  17 . It is to be noted that all components of the flap support structure  6  are housed either within the wing trailing edge region or the flap fairing surface, such that there is no requirement for any additional satellite fairings. The fairing  19   a  defines a forward end of the flap support beam  10  and the diaphragm  19   d  defines a rear end of the flap support beam  10 . The diaphragm  19   d  forms part of an aft fitting which further includes an aft bracket  20  having attaching lugs  21  for pivotal connection to the rear link  14   c  of the four bar linkage arrangement  14 . The diaphragms  19   a  and  19   b  support a forward pin  32  (described in detail later), and the diaphragm  19   c  is a stiffener for supporting the aft section of the support beam  10 . 
     The fairing  17  may be formed of composite materials, e.g. carbon fibre reinforced plastic (CFRP), or any other suitable lightweight, high strength material. In a departure from known flap support structures, the fairing  17  forms an integral structural component of the flap support beam  10 . It is not merely an aerodynamic cladding of a framework, as in the prior art, but is fixedly attached, or integrally formed with, the internal structures  18  and  19   a - d . The modular flap support beam  10  may have a lower weight than a comparable framework supporting a non-structural aerodynamic fairing. 
     However, designs incorporating either structural or non-structural aerodynamic fairings are both intended. In the case where the flap support beam has a framework and non-structural fairing construction, the universal support structure will form part of the framework. The drive unit, linkage arrangement, flap and attachment of the flap support beam to the aircraft will remain substantially unchanged. 
     Returning to  FIG. 6 , the flap support beam  10  further comprises a forward upper cover  22  extending between the upper free edges of the fairing  17  forward of the universal support structure  18 , and a rear cover  23  extending between the upper free edges of the fairing  17  aft of the universal support structure  18 . The covers  22 ,  23  are fixed to the diaphragms  19   a - d . As can be seen, the flap support beam  10  has a monocoque instruction in which the fairing  17  plays a predominant structural role. The structural fairing  17  together with the covers  22 ,  23 , universal support structure  18  and diaphragms  19   a - d  form an enclosed, internally supported structure. The rear cover  23  includes a cut-out  24  to allow unimpeded movement of the drive link  14   a  and the fixed flap linkage  14   b.    
     The universal support structure  18  not only forms a key component of the flap support beam  10  but also forms a key component of the drive unit  13 . The universal support structure  18  has a complex shape including a generally U-shaped lower portion  18   a  leading to an upper dog leg portion  18   b  and supported by a forward web  18   c . This shape of the universal support structure  18  provides a simple but stiff solution. The upper dog leg portion  18   b  is canted rearwardly with respect to the lower U-shaped portion  18   a . The upper portion  18   b  includes lateral flanges with the web  18   c  providing a forward bridge between the flanges. Whereas the lower portion  18   a  forms part of the primary structure of the flap support beam  10 , the upper portion  18   b  of the universal support structure  18  provide the dual function of being part of the drive unit  13  and also providing means for attaching the flap support beam  10  to the wing fixed trailing edge. 
     As best shown with reference to  FIGS. 6, 7 and 9  the drive unit  13  includes a drive shaft  25  rotatably supported by the upper portion  18   b  of the universal support structure  18 . The drive shaft  25  is received within bearings  26 ,  27  in the respective flanges of the upper portion  18   b  of the universal support structure. The drive shaft  25  is coupled in rotation to a geared rotary actuator  28  fixedly mounted externally on one flange of the upper portion  18   b  of the universal support structure. The drive arm  14   a  is fixed in rotation with respect to the drive shaft  25 . For example, the drive shaft  25  may be splined onto one end of drive arm  14   a.    
     The upper portion  18   b  of the universal support structure extends above the fairing  17 . Since the actuator  28  and drive shaft  25  are mounted to the upper portion  18   b  of the universal support structure, the actuator  28  is disposed adjacent the rear spar  9  and the actuator  28  is disposed outside of the fairing  17 . Positioning the actuator  28  in this way, combined with the four-bar linkage arrangement  14 , makes it possible to provide a particularly narrow width for the flap support beam  10 . 
     By comparison with existing state of the art flap support beams for moving similarly sized trailing edge flaps, the flap support beam  10  is approximately 50% narrower in cross-sectional width. Whilst there is a slight trade-off in that the four-bar linkage arrangement  14  requires a relatively long drive arm  14   a , which in turn requires a slightly deeper fairing  17 , the overall maximum cross-sectional area of the flap support beam  10  is significantly reduced as compared with the state of the art flap support beams. Not only does this smaller fairing  17  contribute less drag, but it is also significantly more lightweight as the smaller fairing  17  requires less reinforcement to achieve the required stiffness. The lower weight, lower drag solution provides improvements in reduced fuel consumption and therefore contributes to lower operating costs for the aircraft and reduced emissions. 
     The drive arm  14   a  is a failsafe drive arm and includes a primary arm  14   a   1  and a secondary arm  14   a   2  sandwiching the primary arm  14   a   1 . Use of a failsafe drive arm  14   a  helps to ensure that a partial failure of the drive arm  14   a  does not lead to catastrophic failure and loss of the flap  5 . The drive arm  14   a  need not be splined on to the drive shaft  25  and instead the drive arm may be keyed or otherwise fixed in rotation with respect to the driveshaft  25 . The drive arm  14   a  is curved so as to avoid clash with the forward pin, but this may not be necessary in all embodiments. The driveshaft  25  may be a failsafe driveshaft and include an inner driveshaft surrounded by an outer driveshaft. These and other alternatives for ensuring safe operation of the drive unit  13  will be appreciated by those skilled in the art. 
     Whilst in the above described embodiment the actuator  28  is a geared rotary actuator, it will be appreciated that other types of actuators may similarly be used. For example, a variety of linear and rotary actuators are known in the art for driving aircraft flaps. It is preferable that the actuator  28  is mounted directly on the side of the universal support structure  18  in order to provide a modular flap support structure  6 . 
     However, it will be appreciated that the actuator may alternatively be mounted elsewhere within the wing trailing edge region and coupled to the drive shaft. For example, the actuator may be mounted directly on the rear spar of the aircraft wing. In either case, it is preferable that the actuator is a plug-in component for ease of installation and removal for maintenance or repair. 
     Attachment of the flap support structure  6  to the aircraft wing  3  will now be described in detail with reference to  FIGS. 8 to 10 .  FIG. 8  illustrates a partially cut-away view of the aircraft wing  3  showing the upper wing cover  7 , the lower wing cover  8  and the rear spar  9 . In this particular embodiment, the rear spar  9  is integrally formed with the lower wing cover  8  (which in turn is integrally formed with the front spar—now shown) in a so-called “U-box” wing box construction. The upper wing cover  7  is fastened to the upper flange of the rear spar  9  (and similarly to the front spar—not shown). However, the flap support structure  6  is equally applicable to aircraft wings having different wing box constructions, and in particular is applicable to more traditional wing box constructions having discrete front and rear spars and upper and lower wing covers. As can be seen from  FIG. 8 , the aft aircraft fitting  16  is mounted to the rear spar  9  and the forward aircraft fitting  15  is mounted to the lower wing cover  8 . 
     The aft aircraft fitting  16  comprises first and second failsafe brackets  16   a ,  16   b  spaced apart along the rear spar  9  in the spanwise direction so as to receive the upper portion  18   b  of the universal support structure  18  of the flap support structure  6  between the failsafe brackets  16   a ,  16   b . The brackets  16   a ,  16   b  includes pairs of bracket components arranged back-to-back to provide a failsafe fitting. Each of the failsafe brackets  16   a ,  16   b  include a high misalignment spherical bearing  16   c  for receiving an aft pin  29 . As can be seen from  FIG. 9 , the aft pin  29  passes through the upper portion  18   b  of the universal support structure  18 , which also includes high misalignment spherical bearings  30  mounted within each of the side flanges of the universal support structure  18 . The high misalignment spherical bearings  30  are used because the longitudinal axis of the flap support beam  6  is offset from the normal to the rear spar  9  longitudinal axis. The flap support structure  6  is aligned with the wing chordwise direction but due to the swept trailing edge of the wing  3 , the rear spar  9  is oriented at an angle to the wing spanwise direction. 
     The aft pin  30  is a failsafe pin comprising two concentric failsafe cylinders (e.g. of stainless steel) acting together as multiple load paths to tolerate ultimate load, and individually to tolerate the limit load. The aft pin  30  is secured in position by a locking nut at one of the pin  30 . Sleeves  31  are disposed between the spherical bearings  30  of the universal support structure  18  and the spherical bearings  16   c  of the failsafe aft brackets  16   a ,  16   b . The failsafe brackets  16   a ,  16   b  together act as multiple load paths to tolerate ultimate load, and act individually to tolerate the limit load. The brackets  16   a ,  16   b  may be in aluminium, for example. Any gap between the inner and outer cylinders of the failsafe pin  30  may be filled with a non-setting sealant to prevent corrosion. The four spherical bearings  16   c  and  30  (×2) act to eliminate induced bending on the fairing  17  and the brackets  16   a ,  16   b  of the aircraft fitting  16 . The spherical bearings  16   c ,  30  are of the self-aligning type with a self-lubricating liner. 
     Returning to  FIG. 8 , the forward aircraft fitting  15  includes a failsafe bracket  15   a  having a spherical bearing  15   c . The failsafe bracket  15   a  comprises back-to-back brackets (e.g. in aluminium) clamped together to tolerate ultimate load, and acting individually to the limit load. The spherical bearing  15   c  receives a forward pin  32  shown in detail in  FIG. 10 . The pin  32  is mounted to the forward diaphragms  19   a ,  19   b  of the flap support beam  6 . The pin  32  extends between the diaphragms  19   a ,  19   b  and projects forwardly from the front diaphragm  19   a  as a spigot. The forwardly projecting portion of the pin  32  is received in the spherical bearing  15   c  and is free to slide within the spherical bearing  15   c  in the fore-aft aircraft direction to provide tolerance. The pin  32  is also a failsafe pin comprising inner and outer cylinders (e.g. of stainless steel) acting together as multiple load paths to tolerate ultimate load and individually to the limit load. Any gap between the inner and outer cylinders of the pin  32  is filled with a non-setting sealant to prevent corrosion. The pin  32  is secured to each of the diaphragms  19   a ,  19   b.    
     A method of installing the flap  5  and the flap support structure  6  to the aircraft wing  3  will now be described with reference to  FIG. 11 . The flap support beam  6  is brought towards the lower wing cover  8  adjacent the rear spar  9 . The fairing  17  has a clearance/gap with the lower wing cover  8  which is filled with aerodynamic sealant, e.g. of rubber. The forward pin  32 , projecting forwardly from the front of the flap support beam  6 , is slid forward through the spherical bearing  15   c  of the forward aircraft fitting  15  until the two spherical bearings  30  of the universal support structure  18  are brought into alignment with the two spherical bearings  16   c  of the aft aircraft fitting  16 . The aft pin is then passed through the four spherical bearings  16   c ,  30  (×2) and secured in position by the pin locking nut after all gaps between the flap support beam  6  and the brackets  16   a ,  16   b  of the aft aircraft fitting  16  have been measured and suitable bushes selected. 
     With the flap support beam  6  secured in position with respect to the aircraft wing  3 , the forward flap attachment  14   b  is connected to the other end of the drive arm  14   a . The rear link  14   c  is then coupled to the rear bracket  20  of the flap support beam  6 , and then to the rear flap attachment. Eccentric bearings may be provided at the flap interfaces to wash out tolerance. Vertical tolerance may also be washed out by adjustment of spoilers  33  (see  FIG. 2 ). Finally, the forward and aft non-structural fairings  11  and  12  are attached to the wing  3  and the flap  5 , respectively. 
     Although the invention has been described above with reference to one or more preferred embodiments, it will be appreciated that various changes or modifications may be made without departing from the scope of the invention as defined in the appended claims.