Link mechanisms, including Stephenson II link mechanisms for multi-position flaps and associated systems and methods

Link mechanisms, including Stephenson II link mechanisms for multi-position flaps and associated systems and methods are disclosed. A system in accordance with a particular embodiment includes an airfoil having an external flow surface with an upper portion and a lower portion, and with the airfoil forming a base link. The system further includes a six-bar linkage coupled to the airfoil and having a Stephenson II configuration, including a binary second link pivotably connected to the airfoil, a ternary third link pivotably connected to the second link, a binary fourth link pivotably connected to the third link, a ternary fifth link pivotably connected to the airfoil and the fourth link, and a binary sixth link pivotably connected to the third link and the fifth link. The system can further include a deployable leading edge panel carried by the linkage, with the leading edge panel being movable via the linkage between a stowed position and at least one deployed position.

TECHNICAL FIELD

The present disclosure is directed generally to link mechanisms, including Stephenson II link mechanisms for multi-position flaps and associated systems and methods.

BACKGROUND

Modern aircraft often use a variety of high-lift leading and trailing edge devices to improve high angle of attack performance during various phases of flight, including take-off and landing. Existing leading edge devices include leading edge slats and Krueger flaps. Leading edge slats generally have a stowed position in which the slat forms a portion of the leading edge of the wing, and one or more deployed positions in which the slat extends forward and down to increase the camber and/or planform area of the wing. Krueger flaps have generally the same function as leading edge slats, but rather than retracting aft to form the leading edge of the wing, Krueger flaps typically fold into the lower surface of the wing when stowed. One drawback with some current leading edge devices is that they may interfere with achieving laminar flow during cruise. Accordingly, there is a need to provide a leading edge device that improves upon current devices and makes laminar flow easier to achieve and sustain during cruise. Another drawback with existing leading edge devices is that they are in some cases difficult to integrate with other structures in the wing leading edge. This drawback can be particularly significant for thin wings, and/or for the thin outboard portions of otherwise thicker wings.

SUMMARY

The following summary is provided for the benefit of the reader only and is not intended to limit the disclosure in any way. The present disclosure is directed generally to link mechanisms for multi-position flaps, and associated systems and methods. A system in accordance with a particular embodiment includes an airfoil having an external flow surface, with the external flow surface comprising an upper portion and a lower portion, and the airfoil forming a base link. The system can further include a six-bar linkage coupled to the airfoil and having a Stephenson II configuration. The linkage can include a binary second link pivotably connected to the airfoil, a ternary third link pivotably connected to the second link, a binary fourth link pivotably connected to the third link, a ternary fifth link pivotably connected to the airfoil and the fourth link, and a binary sixth link pivotably connected to the third link and the fifth link. The system can further include a deployable leading edge panel carried by the linkage, with the leading edge panel being moveable via the linkage between a stowed position and at least one deployed position.

In a particular embodiment, the leading edge panel is fixedly carried by the fourth link. In another embodiment, the leading edge panel is pivotable relative to the fourth link. In still another embodiment, the second link is pivotably connected to the airfoil at a first location, the fifth link is pivotably connected to the airfoil at a second location forward of the first location, and the system further comprises an ice protection airflow duct positioned between the first and second locations. In yet a further embodiment, the system can further include a bullnose pivotably coupled to the leading edge panel, and a support panel pivotably coupled to the leading edge panel, the bullnose and the third link. A seventh link can be pivotably connected between the support panel and the fifth link. The at least one deployed position can include a landing position and a take-off position, and the leading edge panel can form a part of the lower portion of the airfoil when in the stowed position, can have a trailing edge that is spaced apart from the upper portion of the airfoil to form a gap when in the landing position, and can seal the gap when in the take-off position. The leading edge panel can be flexible and can change shape as the leading edge panel moves from the stowed position to at least one of the landing position and the take-off position.

Still further aspects of the disclosure are directed to methods for operating an aircraft wing system. One such method includes deploying a leading edge panel relative to an airfoil having an external flow surface, and shielding the airfoil with the leading edge panel during take-off to at least restrict debris from attaching to the external flow surface. The method can further include stowing the leading edge panel after take-off, promoting laminar flow over an upper portion of the external flow surface during cruise, and deploying the leading edge panel to be spaced apart from a leading edge of the wing during at least one of approach and landing. In a particular aspect of this method, deploying the leading edge panel can include deploying a six-bar linkage coupled to the airfoil and having a Stephenson II configuration that includes a binary second link pivotably connected to the airfoil, a ternary third link pivotably connected to the second link, a binary fourth link pivotably connected to the third link, a ternary fifth link pivotably connected to the airfoil and the fourth link, and a binary sixth link pivotably connected to the third link and the fifth link, with the leading edge panel carried by the linkage.

DETAILED DESCRIPTION

The present disclosure describes link mechanisms for multi-position flaps and associated systems and methods. Certain specific details are set forth in the following description andFIGS. 1-11to provide a thorough understanding of the various embodiments of the disclosure. Well-known structures, systems, and methods often associated with such systems have not been shown or described in detail to avoid unnecessarily obscuring the description of various embodiments of the disclosure. In addition, those of ordinary skill in the relevant art will understand that additional embodiments of the disclosure may be practiced without several of the details described below.

FIGS. 1-5illustrate an embodiment of the disclosure that includes a rigid Krueger flap, andFIGS. 6-10illustrate an embodiment that includes a variable camber Krueger flap.FIG. 1is a partially schematic illustration of an aircraft system300having a leading edge assembly303and an associated linkage or link mechanism302configured in accordance with an embodiment of the disclosure. In one example, the leading edge assembly303is positioned to provide enhanced airflow characteristics for an airfoil301on which it is installed. General attributes of the airfoil301and more detailed attributes of the leading edge assembly303and the link mechanism302are described below.

The airfoil301may be configured for operation at any of a variety of flight conditions. In one embodiment, the airfoil301can be a wing, and in other embodiments, the airfoil301can include other surfaces designed to produce lift from the movement of air. The particular airfoil301shown inFIGS. 1-10, for example, is configured for cruise at high subsonic Mach numbers representative of typical commercial transport airliners. Accordingly, the airfoil301can include an external flow surface310having a rounded leading edge. The external flow surface310includes an upper portion311and a lower portion312. In some configurations, the lower portion312may include an opening313. When the leading edge assembly303is deployed to a landing position, as shown inFIG. 1, the opening313is exposed. When the leading edge assembly303is stowed, it closes the opening313as described further below with reference toFIG. 3.

The leading edge assembly303can include a bullnose390that is pivotably connected to a leading edge panel350. In some embodiments the bullnose390has a thickness-to-length (T/L) ratio of approximately 0.5. In other embodiments, the bullnose390can have other generally blunt shapes, including shapes with T/L ratios greater than 0.5. In general, it is expected that blunt bullnoses will improve aerodynamic performance at certain flight conditions, e.g., low speed conditions. It is also expected that link mechanisms in accordance with at least some of the embodiments disclosed herein can facilitate stowing and deploying such bullnoses.

The leading edge panel350can include a streamlined flow surface314. When the leading edge panel350is configured as a rigid Krueger flap, the streamlined flow surface314has a generally fixed shape. Accordingly, the streamlined flow surface314in the rigid Krueger flap embodiments may undergo small deflections due to aerodynamic loading, but has generally the same shape as shown inFIG. 1when in its deployed positions and when in its stowed position. When the leading edge panel350is configured as a variable camber Krueger flap, the streamlined flow surface314changes shape as the leading edge panel350is moved or rotated so as to further change the camber of the airfoil301. In either arrangement, a panel support member360can be positioned to support the streamlined flow surface314.

The leading edge assembly303is shown in a representative deployed position (e.g., a landing position) inFIG. 1. In this position, the leading edge panel350has a trailing edge351that is spaced apart from the upper portion311of the airfoil301to form a gap304. In this configuration, the leading edge assembly303effectively forms a much blunter (though reasonably aerodynamically efficient) leading edge for the airfoil301, which allows the airfoil301to operate efficiently at high angles of attack, which are typically encountered during approach, landing, and take-off. The link mechanism302moves the leading edge assembly303to and from the landing position.

The link mechanism302can include links that are connected to the airfoil301and the panel support member360via a series of pivot points P1through P8. The links can be arranged in a six-bar Stephenson II configuration. This configuration includes a base or first link, formed by the airfoil301and five additional links that include binary links (having two pivot connections) and ternary links (having three pivot connections). For purposes of illustration, the base or first link is indicated as “ground,” and the remaining links are shown both in outline form (with solid lines) and in a simplified “stick” form (in dashed lines), to more clearly identify the relationships among the links. In an embodiment shown inFIG. 1, the link mechanism302can include a binary second link322pivotably connected to the airfoil301at a first pivot point P1, and pivotably connected to a ternary third link323at a second pivot point P2. The third link323can be pivotably connected to a binary fourth link324at a third pivot point P3, and can be pivotably connected to a binary sixth link326at a fourth pivot point P4. The binary fourth link324can in turn be pivotably connected to a ternary fifth link325at a sixth pivot point P6, and the fifth link325can be pivotably connected to the sixth link326at a fifth pivot point P5. The fifth link325is also pivotably connected to the airfoil301at a seventh pivot point P7.

In a particular aspect of this embodiment, the fourth link324is formed at least in part by the panel support member360, which in turn supports the leading edge panel350. Accordingly, as the fourth link324rotates and translates, it articulates the leading edge panel350as well. In particular embodiments, the link mechanism302can include auxiliary links, for example, a seventh link327that is pivotably connected to the third link323at the fourth pivot point P4, and is pivotably connected to the bullnose390at an eighth pivot point P8to provide articulated motion for the bullnose390.

The link mechanism302is driven by an actuator A. In an embodiment shown inFIG. 1, the actuator A drives the second link322, and in other embodiments, the actuator A can drive other links. The actuator A can be coupled to a controller395. The controller395is coupled to a selector394that has one or more selectable positions (396,397,398,399). In the embodiment shown inFIG. 1, position396corresponds to a take-off position, position397corresponds to a landing position, position398corresponds to a stowed position, and position399is a brake position. The selector394can also include other positions or controls depending on aircraft characteristics and specifications. The positions can be selected manually by an operator or automatically via a control system, e.g., via computer-implemented instructions resident on computer-readable media of the controller395and/or other computer-based systems or subsystems. Once a position is selected, the controller395directs the actuator A to move the leading edge panel350to the selected position.

As indicated above, the actuator A can be coupled to the second link322. The second link322is rotatable about the first pivot point P1as indicated by arrow C. In a particular embodiment, the second link322can be rotated by approximately 100 degrees, and in other embodiments it can rotate by other amounts depending on particular aircraft features and requirements. In particular embodiments, the actuator A includes a rotary actuator or a linear type actuator, but other types of actuators may be used in other embodiments. To move the leading edge assembly303from the landing position shown inFIG. 1to the take-off position shown inFIG. 2, the second link322may be rotated clockwise, as shown by arrow C, to move the leading edge panel350and the bullnose390away from the opening313.

The link mechanism302can be arranged to efficiently transmit aerodynamic loads to the airfoil301, conserve weight, and allow for integration of other airfoil components. For example, the second link322may have a generally straight shape. In some embodiments, the fifth link325may have a gooseneck or otherwise bent shape. The third link323may have a generally straight shape or may include a small bend. These components can have other shapes in other embodiments, depending on factors that may include the manner in which the links are integrated with the airfoil301.

The leading edge of the airfoil301can house components in addition to the link mechanism302. For example, the airfoil can include an ice protection airflow duct380positioned at or near the airfoil leading edge. The airflow duct380transmits heated air to the leading edge of the airfoil301to prevent and/or inhibit the formation of ice at the leading edge, and/or to remove accumulated ice. As will be described in further detail later, the arrangement of the illustrated link mechanism302can allow it to be more readily integrated with components of the wing leading edge, including the airflow duct380.

FIG. 2illustrates the system ofFIG. 1with the leading edge assembly303in a take-off position. In this position, the leading edge panel350is rotated further away from the opening313. To achieve this position, the second link322is rotated about the first pivot point P1by the actuator A, and as a result, the leading edge panel350is rotated into engagement with the airfoil301. The gap304shown inFIG. 1between the leading edge panel350and the upper portion311can be sealed as a result of this motion. Sealing the gap304during take-off is expected to help maintain a generally smooth surface over the airfoil301. This can aid in preserving airflow characteristics for achieving laminar flow during cruise. In some embodiments, laminar flow will not be achieved while the leading edge assembly303is in the take-off position; however, sealing the gap304during take-off can help prevent insects, particles, or other debris encountered during take-off from attaching to the airfoil301. Shielding the airfoil301in this way is expected to increase the likelihood and/or extent of laminar flow achieved during cruise operation.

FIG. 3illustrates the system ofFIG. 1with the leading edge assembly303in a fully stowed position. When the leading edge assembly303is in its stowed position, it covers the opening313shown inFIG. 2to provide for a generally continuous aerodynamically smooth lower portion312. To achieve this position, the second link322is rotated in a counterclockwise direction as shown by arrow S inFIG. 3. In this configuration the leading edge panel350has been folded toward the airfoil301so as to be flush with the leading edge and the lower surface312, with the bullnose390and the link mechanism302housed completely within the airfoil301. In this configuration, the airfoil301is typically flown at conditions not requiring enhanced lift performance, for example, a sustained cruise condition. As discussed above, in at least some embodiments, laminar flow may be easier to achieve and sustain in this configuration because the airfoil301has been kept clean during take-off.

FIG. 4illustrates a snapshot of the system ofFIG. 1with the leading edge panel350in transition from the stowed position shown inFIG. 3to the take-off position and/or the landing position. To achieve this position, the second link322is rotated in a clockwise direction as indicated by arrow C. The leading edge panel350and the bullnose390move accordingly and the opening313is exposed.

FIG. 5illustrates another view of the system ofFIG. 1with the leading edge panel350moving to a generally vertical position. The position shown inFIG. 5is commonly referred to as a “barn door” configuration. In this position, the leading edge assembly303can form a very blunt shape that slows the aircraft down, for example, during landing rollout.

FIGS. 4 and 5illustrate the operation of the leading edge assembly303during deployment. The leading edge assembly303moves away from the opening313as the second link322rotates about the first point P1. The third link323transfers the motion to the sixth link326and the panel support member360, and the seventh link327extends the bullnose390forward and outward. The fifth link325rotates as the leading edge panel350moves up and the trailing edge351begins to close the gap304.

FIGS. 6-10illustrate an embodiment of the disclosure that includes a leading edge assembly303having a variable camber Krueger arrangement. Accordingly, the leading edge assembly303includes a flexible leading edge panel450, e.g., a leading edge panel450that changes shape as it is deployed and retracted. In general, the positions of the leading edge panel450shown inFIGS. 6-10correspond to the positions of the leading edge panel350described above with reference toFIGS. 1-5, respectively. Beginning withFIG. 6, the leading edge assembly303is shown in a landing position similar to the position shown inFIG. 1. In this position, the leading edge panel450flexes to a curved shape and has a trailing edge451that is spaced apart from the upper portion311of the airfoil301to form a gap304. As inFIG. 1, the link mechanism302moves the leading edge panel450to and from the landing position.

The link mechanism302can include links that are arranged in a six-bar, Stephenson II configuration similar at least in part to the arrangement described above with respect toFIGS. 1-5. Accordingly, in an embodiment shown inFIG. 6, the link mechanism302can include a binary second link422pivotably connected to the airfoil301at a first pivot point P1, and pivotably connected to a ternary third link423at a second pivot point P2. The third link423can be pivotably connected to a fourth link424at a third pivot point P3, and can be pivotably connected to a binary sixth link426at a fourth pivot point P4. The binary fourth link424can in turn be pivotably connected to a ternary fifth link425at a sixth pivot point P6, and the fifth link425can be pivotably connected to the sixth link426at a fifth pivot point P5. The fifth link425is also pivotably connected to the airfoil301at a seventh pivot point P7.

Unlike the arrangement described above with reference toFIGS. 1-5, the arrangement shown inFIG. 6includes a panel support member460that does not form one of the links of the six-bar linkage. Instead, the panel support member460is pivotably coupled to the third link423at an eleventh pivot point P11, and is pivotably coupled to the leading edge panel450at a ninth pivot point P9and to a bullnose490at a tenth pivot point P10. This arrangement allows the panel support member460to both flex the leading edge panel450and articulate the bullnose490. A seventh link427is pivotably coupled between the fifth link425and the panel support member460to guide this motion.

The second link422is rotatable about the first pivot point P1as indicated by arrow C inFIG. 6, and can be driven by an actuator A, generally as described above. To move the leading edge assembly303beyond the landing position shown inFIG. 6to the take-off position shown inFIG. 7, the actuator A rotates the second link422clockwise, as shown by arrow C, to move the leading edge panel450and the bullnose490away from the opening313.

FIG. 7illustrates the system ofFIG. 6with the leading edge assembly303in a take-off position. In this position, the leading edge panel450is rotated further away from the opening313. To achieve this position, the second link422is rotated about the first pivot point P1by the actuator A, which moves the leading edge panel450into engagement or near engagement with the airfoil301. The gap304shown inFIG. 6between the leading edge panel450and the upper portion311can be sealed, partially sealed, or at least partially closed as a result of this motion.

FIG. 8illustrates the system ofFIG. 6with the leading edge assembly303in a fully stowed position. When the leading edge assembly303is in its stowed position, it covers the opening313shown inFIG. 7to provide for a generally aerodynamically smooth lower portion312. To achieve this position, the second link422is rotated in a counterclockwise direction as shown by arrow S inFIG. 8. In this configuration the leading edge panel450has been folded toward the airfoil301so as to be flush with the leading edge and the lower surface312, with the bullnose490and the link mechanism302housed completely within the airfoil301.

FIG. 9illustrates the system ofFIG. 6with the leading edge panel450moving from the stowed position shown inFIG. 8to the take-off position and/or the landing position. To achieve either position, the second link422is rotated in a clockwise direction as indicated by arrow C. The leading edge panel450and the bullnose490move away from the opening313.FIG. 10illustrates another view of the system ofFIG. 6with the leading edge panel450moving to a generally vertical position or “barn door” configuration.

One feature of embodiments of the systems described above with reference toFIGS. 1 through 10is that the link mechanism302can have six elements arranged in a six-bar, Stephenson II configuration. One expected advantage of this arrangement is that it can be simpler to manufacture, install, and/or maintain than an arrangement having a more complex set of links. At the same time, this arrangement is expected to be more compact (in the stowed position) than arrangements having fewer links. A corresponding advantage of this feature is that the link mechanism can more readily be installed on thin airfoil sections, e.g., airfoil sections at the outboard regions of a wing. Another corresponding advantage of at least some embodiments having these features is that they can allow a relatively thick bullnose (e.g., having a T/L ratio of 0.5 or greater) to be stowed in a thin airfoil section.

Another feature of at least some of the foregoing embodiments is that the link mechanism can readily accommodate other components located at the airfoil leading edge. For example, the arrangement described above with reference toFIGS. 1-5accommodates the ice protection airflow duct380at a position between the two pivot points P1, P7connecting the link mechanism306with the airfoil301. Other link arrangements can interfere with such a positioning when the corresponding leading edge panel is stowed. In the arrangement shown inFIGS. 6-10, the ice protection airflow duct380is positioned forward at the forward pivot point P7, while still allowing the link mechanism302to assume a compact stowed configuration that integrates with the thin airfoil301.

Still another feature of some embodiments of the system described above with reference toFIGS. 1 through 10is that the system provides either a rigid Krueger flap or a variable camber Krueger flap moveable between at least three positions (e.g., the stowed position, the sealed take-off position, and the gapped landing position). Notably, in some embodiments, the gap304between the trailing edge351and the upper portion311may be sealed or at least partially sealed when the system is in the take-off position. Sealing or at least partially sealing the gap304during take-off is expected to preserve conditions for subsequently achieving and maintaining laminar flow during cruise, and/or otherwise reducing drag, for example, by restricting or preventing particles, debris, or other foreign objects from attaching to the surface of the wing at or upstream of a laminar flow region. In addition, because this mechanism is suitable for installation in thin wing sections, a greater spanwise extent of the leading edge is protected from debris, and accordingly this arrangement can achieve and/or promote laminar flow over a greater spanwise region of the airfoil.

FIG. 11is a partially schematic, isometric illustration of an aircraft500that includes a fuselage502, wings501, and an empennage503. The empennage503can include horizontal stabilizers504and a vertical stabilizer505. The aircraft500further includes a propulsion system506having two wing-mounted nacelles507, each carrying a turbofan engine508. Each of the wings501can include one or more leading edge panels550configured in any of the foregoing embodiments. In a particular embodiment, the link mechanisms driving the leading edge panels550can be geometrically similar for inboard leading edge panels (e.g., located near the nacelles507) and outboard leading edge panels, (e.g., located near the wing tip). Accordingly, a geometrically similar link mechanism can be scaled up for inboard locations and scaled down for outboard locations. This arrangement can simplify the design, installation and maintenance procedures associated with the leading edge panels.

From the foregoing it will be appreciated that specific embodiments of the disclosure have been described herein for purposes of illustration but that various modifications may be made without deviating from the disclosure. For example, the elements of the link mechanisms may have different shapes than are shown in the Figures. In other embodiments, the actuator may be coupled to different links than are shown in the Figures. In particular embodiments, the flaps may have configurations other than a Krueger configuration. Aspects of the disclosure described in the context of particular embodiments may be combined or eliminated in other embodiments. Further, while advantages associated with certain embodiments of the disclosure may have been described in the context of those embodiments, other embodiments may also exhibit such advantages, and not all embodiments need necessarily exhibit such advantages to fall within the scope of the disclosure. Accordingly, the disclosure can include other embodiments not expressly shown or described above.