Low density flexible edge transition

Details Low density flexible edge transition Low density flexible edge transition

1999-06-15

2001-01-16

Barefoot, Galen L. (Department: 3644)

Aeronautics and astronautics

Aircraft sustentation

Sustaining airfoils

C244S219000, C244S09000B

Reexamination Certificate

active

06173924

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates generally to aircraft aerodynamic control surfaces, and more particularly to a structural transition system for use between an aerodynamic lifting member and a rotatable control device attached thereto.
BACKGROUND OF THE INVENTION
Conventional fixed winged aircraft are provided with a variety of aerodynamic control devices which include, for example, flaps, elevators, ailerons, trim tabs, and rudders. These control devices cooperatively operate to increase or decrease lift over a given localized aerodynamic control surface for achieving pitch, yaw and roll control of the aircraft. Such control devices are used in both traditional winged and modern stealthy aircraft designs. These control devices are typically rigid structures which are integrated into the edges of the wings or body (i.e., aerodynamic lifting surfaces) of the aircraft. The control devices are configured to deflect or rotate about an axis of rotation in a hinge-like fashion with respect to the attached aerodynamic lifting surfaces. Typically, such a control device is characterized as having at least one end which is perpendicularly or at least angularly disposed with respect to the axis of rotation. Operation of the control devices typically forms gaps and/or abrupt changes in surface contours at or about the control device ends.
It is contemplated that gaps, abrupt changes, or contour discontinuities occurring between the aerodynamic lifting surface and the attached control device are especially undesirable because they tend to increase aerodynamic drag and lessen the aerodynamic effectiveness of the control surface due to “leakage” at the end portions of the control device.
Prior art attempts to mitigate the formation of such surface discontinuities include U.S. Pat. No. 5,794,893 to Diller et al. and U.S. Pat. No. 5,222,699 to Albach et al. which contemplate use of surface skins which span across the lifting surface/control device gap to smooth the surface transition thereat. These surface skins are formed of an elastomeric material which have rods integrated therein for structural support. It is contemplated that such structural support is required as such surface skin are exposed to various air loads which can undesirably deform the elastomeric surface skins. These reinforcing rods are typically disposed in a spanwise direction and are mounted in large end ribs with either “fixed” or “guided” end conditions. As the control device rotates, these rods are deflected into an “S” shape. In any deflected position, these spanwise rods are required to beam a combination of air load and induced bending load to the end ribs. In the undeflected position, the rods must beam only the air load to the end ribs. Regardless, due to the “fixed” and/or “guided” end conditions, each spanwise rod produced a resultant shear load and bending moment at the end ribs. Due to the plurality of spanwise rods, these shear loads and bending moments must be summed and become the driving design requirement for the end ribs. The resultant rib becomes large and heavy, typically requiring the use of a dense, high strength metallic material, in order to prevent large deflections (vertical and twist) of the end rib and adjacent fixed wing structure.
Such a design results in several complications. First, it is desirable for aircraft structures to be relatively light weight. The weight impact due to the addition of large end ribs tend to lessen the overall performance enhancement provided by the use of the rod reinforced transitions. Second, the hinge moment for driving the control device tends to be severely increased. This results in reduced control device deflection rates, increased actuation size and power requirements, or a combination thereof. Third, such large and heavy end ribs are not typically compatible with advanced military airframe edge designs. Contemporary edge designs call for relatively low density edge members, typically of a composite, thin skinned, honeycomb construction. Heavy metallic ribs are not compatible with this design construction. Finally, the reinforcing rods may tend to suffer from having a limited useful life due to large cyclic defections of the control device.
It is therefore evident that there exists a need in the art for an improved system which mitigates the formation of gaps and abrupt surface contour changes occurring between an aerodynamic lifting surface and an attached control device. In addition, there exists a need for such improved system which mitigates high shear loads and bending moments at the attachment points of the lifting surface and the control device.
SUMMARY OF THE INVENTION
In accordance with the present invention, there is provided a structural transition system for use between an aerodynamic lifting member and an aerodynamic control device attached thereto. The aerodynamic lifting member has an indenture formed therein which is defined by a first shoulder portion. The control device has a first end and is disposed within the indenture with the first end adjacent the first shoulder portion. The control device is sized and configured to rotate about a control device axis of rotation for deflecting the control device relative to the lifting member. The structural transition system is provided with a torque transfer element disposable between and in mechanical communication with the first shoulder portion and the first end. The torque transfer element is sized and configured to deform in response to deflection of the control device. The structural transition system is further provided with at least two of support elements distributed between the first shoulder portion and the first end. The support elements are in mechanical communication with the torque transfer element. The support elements are sized and configured to incrementally rotate generally about the control device axis of rotation in response to deformation of the torque transfer element.
In the preferred embodiment of the present invention, the lifting member and the control device define an aerodynamic surface contour which deforms in response to deflection of the control device. The support elements each have an outer edge which further defines the surface contour. The outer edges are sized and configured to transition the aerodynamic surface contour between the lifting member and the control device adjacent first shoulder portion of the indenture. More particularly, the lifting member may have upper and lower lifting member surfaces and the control device may have upper and lower control device surfaces. The upper and lower lifting member surfaces and the upper and lower control device surfaces define the aerodynamic surface contour. The support elements each may have upper and lower outer edges which further define the surface contour. The upper outer edges are sized and configured to transition the aerodynamic surface contour between the upper lifting member surface and the upper control device surface. Similarly, the lower outer edges are sized and configured to transition the aerodynamic surface contour between the lower lifting member surface and the lower control device surface.
Preferably, the structural transition system is further provided with a flexible outer skin attached to the lifting member and the control device. The outer skin is in mechanical communication with the outer edges of the support elements and deforms in response to rotation of the support elements. The flexible outer skin may be provided with spanwise rods which are integrated therein for assisting in beaming air loads between the outer edges of the support elements. The rods are preferably disposed in slidable engagement with the outer skin so as to allow the outer skin the expand/contract with deflection.
In addition, the structural transition system may be further provided with at least one flexible core section interposed between the support elements. Each core section has upper and lower core surfaces. The upper core surface is aligned with the upper outer edges of the adjacent support el

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