Control surface for an aircraft

[0002] This application is a continuation of U.S. application Ser. No. 09/517,838, filed Mar. 2, 2000, now U.S. Pat. No. 6,209,824, which is in turn a continuation of U.S. application Ser. No. 08/932,947, filed Sep. 17, 1997, and presently abandoned.

[0003] The present invention relates generally to the field of aircraft and more particularly to a control surface for an aircraft.

[0004] Aircraft incorporate control surfaces to provide roll, pitch and yaw control, as well as high lift devices such as flaps. Present control surfaces are rigid panels that are pivoted out of the surrounding moldline of the aircraft to create the control moment. These control surfaces have gaps that result in aerodynamic spillage, that reduce the effectiveness of the control surface. Present control surfaces are particularly ineffective in tailless aircraft designs. Tailless designs provide increased aerodynamic efficiency and agility. However, to provide adequate yaw control thrust-vectoring engine nozzles are required. Thrust-vectoring nozzles are expensive and heavy.

[0005] Thus there exists a need for a control surface that does not have aerodynamic spillage and can replace heavy, expensive thrust-vectoring nozzles on tailless aircraft designs.

[0006] A control surface for an aircraft that overcomes these and other problems has a reinforced elastomer surface on a surface of the aircraft and has a perimeter attached to the aircraft. An actuation mechanism moves the reinforced elastomer surface from a first position, substantially conforming to a moldline of the aircraft, to a second position, protruding from the moldline of the aircraft.

[0007] FIG. 1 is a perspective view of a wing of an aircraft with a prior art control surface;

[0008] FIG. 2 is a perspective view of a reinforced elastomer panel;

[0009] FIG. 3 is a perspective view of an embodiment of a control surface for an aircraft according to the invention;

[0010] FIG. 4 is a cross sectional view of the control surface of FIG. 3 taken along the A—A line;

[0011] FIG. 5 is a cross sectional view of the control surface of FIG. 3 taken along the A—A line, in an actuated position;

[0012] FIG. 6 is a cross sectional view of the control surface of FIG. 3 taken along the B—B line;

[0013] FIG. 7 is a cross sectional view of the control surface of FIG. 3 taken along the B—B line, in an actuated position;

[0014] FIG. 8 is a cross section view of an embodiment of a flexible spine used in the control surface of FIG. 3;

[0015] FIG. 9 is a cross section view of another embodiment of a flexible spine used in the control surface of FIG. 3;

[0016] FIG. 10 is perspective view of a tailless aircraft having an embodiment of a control surface according to the invention;

[0017] FIG. 11 is a perspective view of an embodiment of a control surface according to the invention;

[0018] FIG. 12 is a cross sectional view of an embodiment of the control surface of FIG. 11;

[0019] FIG. 13 is a cross sectional view of an embodiment of the control surface of FIG. 11;

[0020] FIG. 14 is a cross sectional view of an embodiment of the control surface of FIG. 11;

[0021] FIG. 15 is a perspective view of the control surface of FIG. 14;

[0022] FIG. 16 is a perspective view of an aircraft having an embodiment of a control surface according to the invention;

[0023] FIG. 17 is a top view of the control surface of FIG. 16;

[0024] FIG. 18 is a cross sectional view of the control surface of FIG. 16; taken along the C—C line;

[0025] FIG. 19 is a perspective view of a rotor blade for a helicopter; and

[0026] FIG. 20 is a perspective view of an embodiment of a control surface for a rotor.

[0027] FIG. 1 is a perspective view of a wing 50 of an aircraft with a prior art control surface 52. The prior art control surface 52 allows aerodynamic spillage through the gaps 54 between the wing and the control surface 52. This significantly limits the aerodynamic effectiveness of the control surface.

[0028] The key to building an improved control surface for an aircraft is to design a control surface that takes advantage of the elastomer panel 60 as shown FIG. 2 in the design. The elastomer panel 60 has a rod block 62 attached along one edge to an elastomer skin 64. The elastomer skin 64 is capable of stretching to 100% of its unstressed length. In addition, the elastomer skin 64 is capable of twisting. A plurality of rods 66 are attached to the rod block 62 and are allowed to slide freely inside the elastomer skin 64. The rods 66 are made from quartz, epoxy or composites and flex without breaking. The stiffness of these reinforcements is designed to yield a specific expanded shape. The rods 66 provide the elastomer skin 64 with a curvilinear shape when the elastomer panel 60 is elongated, deflected or twisted. This curvilinear shape provides a good aerodynamic shape without any discontinuities that cause turbulence and drag.

[0029] A second rod block 68 is attached to an opposite edge of the elastomer skin 64. The second rod block 68 has a plurality of holes through which the plurality of rods 66 are allowed to slide freely. Both the rod block 62 and the second rod block 68 have attachment provisions 70, for attaching the elastomer panel 60 to the surface of an aircraft.

[0030] FIG. 3 is a perspective view of an embodiment of a control surface 80 for an aircraft according to the invention. The control surface includes a rigid structural panel 82 pivotally attached to the aircraft. The rigid structural panel 82 has a long edge 84 and a pair of short edges 86. A pair of flexible struts 88, 90 extend from each of the pair of short edges 86 to the aircraft. The flexible struts 88, 90 in one embodiment are formed from a high durometer rubber. A long elastomer panel 92 is attached between the aircraft and the long edge 84 of the rigid structural panel 82. The long elastomer panel 92 is a reinforced elastomer panel as shown in FIG. 2. The reinforcing rods 66 are shown as the lines running perpendicular to the long edge 84. A pair of short elastomer panels 94, 96 are connected between the aircraft and the rigid structural panel 82. In addition, the short elastomer panels 94, 96 are connected to the struts 88, 90. The elastomer panels 94, 96 differ from the elastomer panel of FIG. 2, in that they contain a flexible spine 98. The flexible spine 98 will be described in greater detail in connection with FIGS. 8 and 9.

[0031] FIGS. 4 & 5 are cross sectional views of the control surface of FIG. 3 taken along the A—A line. The long elastomer panel 92 consists of two elastomer panels one on the top and one on the bottom. The rigid structural panel 82 pivots along an axis 100 between the elastomer panels. One of the elastomer panels expands to cover the gap in FIG. 5 and the other elastomer panel contracts to cover the gap on the other side.

[0032] FIGS. 6 and 7 are cross sectional views of the control surface of FIG. 3 taken along the B—B line. The elastomer panels 96 consist of a top and a bottom elastomer panel. A flexible spine 98 runs through the center of the elastomer panels. The reinforcing rods attach to the rod blocks 102 and then slide within a plurality of bushings in the spine 98. FIGS. 8 and 9 are two embodiments of the flexible spine 98. The reinforcing rods 120 are shown embedded in the elastomer sheet 122. The rods 120 terminate in a bushing 124. The bushing 124, in one embodiment, is made of a high durometer rubber. The rods 120 are allowed to slide freely within the cavity of the bushing 124. The spines 98 of FIGS. 8 and 9 differ in how the support brace 126 is designed. In FIG. 8 the support brace is a “C” shaped flexible member 128 with a reinforcing rod 130 embedded in the perpendicular side of the member 128. The parallel members are bonded to the bushing 124. In one embodiment, the “C” shaped flexible member 128 is made of a high durometer rubber.

[0033] The spine 98 in FIG. 9 has a composite plate 132 bonded to a pair of flexible footers 134, 136. The flexible footers 134, 136 are bonded to the bushings 124 and the elastomer sheets 122. In one embodiment the flexible footers 134, 136 are made of elastomer.

[0034] FIG. 10 is perspective view of a tailless aircraft 150 having an embodiment of a control surface 152 according to the invention. The control surface 152 is mounted on the surface of the aircraft 150. FIG. 11 is a perspective view of an embodiment of the control surface 152. The control surface 152 has a reinforced elastomer surface 154. A perimeter 156 of the reinforced elastomer surface 154 is formed of rigid material and is attached to the aircraft. The reinforced elastomer surface 154 has a spine 158 extending along its center. The spine 158 in one embodiment is made of a high durometer rubber and has a plurality of cavities (bushings) into which the reinforcing rods slide.

[0035] FIG. 12 is a cross sectional view of an embodiment of the control surface of FIG. 11. In this embodiment, a pneumatic pump (actuation mechanism) 160 is connected to a bladder 164 between the elastomer surface 154 and aircraft. By inflating the bladder 164 the control surface is moved from a first position, conforming to the moldline of the aircraft, to a second position, where the control surface is outside the moldline of the aircraft.

[0036] FIG. 13 is a cross sectional view of another embodiment of the control surface 152 of FIG. 11. In this case the actuation mechanism 170 uses a plunger (rigid surface) 172 to move the control surface, by pushing on the spine 158. The actuation mechanism 170 can be mechanical, electro-mechanical or hydraulic. In another embodiment, shape memory alloy wires (slats) are embedded into the elastomer sheet 154. The shape memory alloy wires actuate the control surface by applying a current to change the state of the wires.

[0037] FIG. 14 is a cross sectional view of another embodiment of the control surface 152 of FIG. 11. In this embodiment a rigid panel 180 is pivotally attached to the aircraft along the perimeter 156. An actuation mechanism 182 is attached to the rigid panel 180. In one embodiment the rigid panel 180 is formed out of a composite. An elastomer sheet 183 (not reinforced in one embodiment) connects a perimeter edge 184 of the rigid panel 180 to the aircraft. Another elastomer sheet 186 (not reinforced) is connected to the traveling edge 188 of the rigid panel 180.

[0038] A collar 190 is attached to the elastomer sheet 186. The collar 190 in one embodiment is made of a high durometer rubber. The reinforcing rods 192 of the reinforced elastomer panel 194 connect to the collar 190. The other ends of the rods 192 of the reinforced elastomer panel 194 slide in a rod block along the perimeter 156.

[0039] FIG. 15 is a perspective view of an embodiment of the control surface of FIG. 14. In this embodiment two rigid panels 180 are adjacent to each other. An elastomer panel 200 connects the two elastomer panels 180. The elastomer panel 200 has a spine 202 running through the center of the elastomer panel 200. The spine 202 is similar to the spine and the reinforcing rods of the elastomer panel 200 slide within bushings in the spine 202. The other end of the reinforcing rods are connected to the rigid panels 180. The design provides a control surface with a variable control area.

[0040] FIG. 16 is a perspective view of an aircraft 220 having an embodiment of a control surface 222 according to the invention. In this embodiment, the control surface is on a nose 224 of the aircraft 220. This control surface 222 provides yaw control for the aircraft 220 at high angles of attack, where conventional control surfaces are less effective. Generally, the control surface 222 would be placed on both sides of the aircraft. FIG. 17 is a top view of the control surface 222. A rigid panel 226 is surrounded by elastomer panels. A perimeter 228 of the control surface is attached to the aircraft 224. A portion of the elastomer sheet 230 without reinforcing rods is connected between the rigid panels 226 and the perimeter 228. A pair of side reinforced elastomer panels 232 connect the sides of the rigid panel 226 to the perimeter 228. A pair of struts 234 are connected between the top edge of the rigid panel 226 and the perimeter 228. A top reinforced elastomer panel 236 connects between the struts 234 and the perimeter 228. A floating strut 238 defines an elastomer panel 240 without reinforcing rods. The elastomer panel 240 allows the control surface to have a sharply sloping back surface 242 (see FIG. 18). FIG. 18 shows a cross section of the control surface taken along the C—C line. A pivot mechanism 244 attaches the rigid panel 226 to the aircraft. An actuation mechanism 246 is pivotally attached to the rigid panel 226 and moves the rigid panel from a first position (conformable surface) to a second position (protruding position). The control surface 222 is light weight and provides control without any gaps that reduce the effectiveness of conventional control surfaces. In addition, the control surface 222 is a novel control surface that has not been used on aircraft to date and provides yaw control at high angles of attack.

[0041] FIG. 19 is a perspective view of a rotor blade 300 for a helicopter (aircraft). A static tab 302 is used to balance the blade 300 from rotational instability. An active flap 304 is used to provide active rotational stability. Active stability can improve rotor efficiency and increase the rotor blade's life. By using the reinforced elastomer panels in a tab design, gaps around the tabs can be eliminated. The gaps reduce efficiency and create vortices that the trailing blade hits. This reduces the lifetime of the rotor blades. FIG. 20 is a perspective view of an embodiment of a control surface 304 for a rotor blade 300. A rigid panel 306 is connected to an actuator 308. In one embodiment the actuator 308 is a shape memory alloy (SMA) actuation system. A SMA actuation system can be made small enough to fit within the confines of the rotor blade 300. The rigid panel 306 has a pair of side reinforced elastomer panels 310 and a back reinforced elastomer panel 312 that encases the rigid panel 306. Another embodiment of the control surface 304 includes struts and spines similar to those shown in FIG. 3.

[0042] Thus there has been described a control surface that eliminates gaps, weighs less than vectored nozzles and provides control surfaces that do not exist in the art. While the invention has been described in conjunction with specific embodiments thereof, it is evident that many alterations, modifications, and variations will be apparent to those skilled in the art in light of the foregoing description. Accordingly, it is intended to embrace all such alterations, modifications, and variations in the appended claims.