# US 4,398,688 A · Leading edge flap for an airfoil > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 4,398,688 A - Document ID: US4398688A - Status: Granted - Kind: A - Application number: 06/274,851 - Filed: 1981-06-18 - Granted: 1983-08-16 - Earliest claimed: 1979-12-26 - Assignees: Lockheed Corporation - Inventors: Arthur L. Williams - Web page: https://patentgrep.com/patent/US4398688A ## CPC - B64C 9/24: by single flap - B64C 3/50: by leading or trailing edge flaps - B64C 21/025: {for simultaneous blowing and sucking} - B64C 21/04: for blowing - B64D 15/04: Hot gas application - B64C 2230/04: by actively generating fluid flow - B64C 2230/06: by explicitly adjusting fluid flow, e.g. by using valves, variable aperture or slot areas, variable pump action or variable fluid pressure - B64C 2230/20: by passively inducing fluid flow, e.g. by means of a pressure difference between both ends of a slot or duct - Y02T 50/10: Drag reduction - Y02T 50/40: Weight reduction - B64C: AEROPLANES; HELICOPTERS - B64D: EQUIPMENT FOR FITTING IN OR TO AIRCRAFT; FLIGHT SUITS; PARACHUTES; ARRANGEMENT OR MOUNTING OF POWER PLANTS OR PROPULSION TRANSMISSIONS IN AIRCRAFT - Y02T: CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION ## Abstract The invention is a leading edge flap for an airfoil. The leading edge (24) is rotatably mounted to the airfoil (14). A first flap segment is (48) attached to the leading edge (24) and has an external aerodynamic surface (50a) adapted to form a portion of the bottom aerodynamic surface of the airfoil (14), when the flap (20) is in the retracted position. A second flap segment (60) is pivotally attached to the first flap segment (48) and is adapted to be retracted within a recess (80) within the airfoil (14). A link (70) is pivotally connected to both the second flap segment (60) and the airfoil rib structure (22) such that rotation of the leading edge (24) extends the first and second flap segments (48 and 60) from their retracted positions downwardly and forwardly of the leading edge (24), forming an aerodynamic extension of the airfoil (14). In an additional embodiment, the rotatable leading edge is coupled to a source of heated and/or pressurized air, and contains a spanwise duct (26') which is adapted to distribute the air along the airfoil (14) heating the leading edge (24') surface so as to remove or prevent ice forming thereon. A plurality of nozzles in the first flap segment (48') are coupled to the duct (26) and/or the bottom surface (142) and adapted to distribute pressurized air over the top surface of the airfoil (14), providing boundary layer control. ## Claims ### Claim 1 An extendable and retractable leading edge flap for an airfoil comprising: a leading edge of the airfoil permanently located and rotatably mounted thereupon; a first flap segment attached to said leading edge for rotation therewith and defining a portion of a lower surface of the airfoil when said flap is in a retracted position; a second flap segment pivotally attached to said first flap segment and adapted to be stored within said airfoil when said second flap is in the retracted position; and linkage means pivotally connecting said second flap segment and said airfoil; whereby the rotation of said leading edge actuates said linkage means and extends said first and second flap segments form their retracted positions downwardly and forwardly of said leading edge, defining an aerodynamic extension of the upper surface of said airfoil and increasing its lift capacity. ### Claim 2 (depends on 1) The leading edge flap of claim 1 wherein said leading edge comprises: torque means extending spanwise along the airfoil for moving with and causing the extension and retraction of said first and second flap segments. ### Claim 3 (depends on 1) The leading edge flap of claim 1 wherein said rotatable leading edge comprises: a torque tube, including a spanwise duct coupled to a source of heated air, said duct adapted to conduct said heated air spanwise along said leading edge for anti-icing said airfoil. ### Claim 4 (depends on 3) The leading edge flap of claim 3 wherein said torque tube comprises: a plurality of tube segments interconnected for coextensive rotation and having ends, at least a portion of which ends are juxtaposed to define a substantially continuous surface over the length of said leading edge irrespective of the interposition of structural rib sections within the airfoil. ### Claim 5 (depends on 1) The leading edge flap of claim 1 wherein said first flap segment comprises: aerodynamic surface means pivotally connected to said leading edge, oriented tangentially with respect to a surface of said leading edge and providing a substantially aerodynamically clean and tangential transition between said structure and said leading edge, said surface of said structure also defining an extended portion of and blending with an under surface of the airfoil when said flap is retracted; and a support structure affixed to, structurally supporting said aerodynamic surface means and sustaining its surface shape, and attaching the same fixedly to said leading edge. ### Claim 6 (depends on 1, 5) The leading edge flap of claim 1 or 5 wherein said second flap segment comprises: a structural member pivotally connected to an extremity of said first flap segment and having an outer aerodynamic surface, extendable from said first aerodynamic surface to define therewith a substantially smooth and continuous aerodynamic surface with said leading edge when said first and second segments are extended. ### Claim 7 (depends on 6) The leading edge flap of claim 6 wherein: said airfoil incorporates a plurality of reinforcing ribs in spaced relation along its leading edge, and said linkage means comprises at least one double ended link member pivotally connected at its respective ends to said second flap segment and to a said reinforcing rib, and actuating means is actuatably connected to said leading edge to rotate the same and to cause said flap to be extended and retracted through the action of said linkage means. ### Claim 8 (depends on 3) The leading edge flap of claim 3 wherein: a plurality of said leading edge segments, a plurality of said first flap segments, and a plurality of said second flap segments are provided along the length of the airfoil to define a plurality of flap portions adapted for simultaneous operation within the assembly. ### Claim 9 (depends on 8) The leading edge flap of claim 8 wherein: said leading edge segments are axially aligned and are interconnected at their adjacent ends by additional tubular means to transmit heated air from one segment to the next along the entire leading edge. ### Claim 10 (depends on 1) The leading edge flap of claim 1 wherein said leading edge comprises: a spanwise torque-transmitting duct coupled to a source of pressurized air, said duct adapted to conduct said air spanwise along said leading edge, and nozzle means coupled to said duct adapted to eject said air from said duct spanwise over an upper surface of said airfoil for boundary layer control when said leading edge is in the extended position. ### Claim 11 (depends on 10) The leading edge flap of claim 10 wherein: said slots are defined in a portion of said first segment adjacent said leading edge. ### Claim 12 (depends on 9) The leading edge flap of claim 9, wherein: said nozzle means includes, a plurality of slots located spanwise along said leading edge and terminating in nozzles adapted to direct said pressurized air over the upper surface of the airfoil when said leading edge flap is in said extended position, and said rotating leading edge includes ports connecting said duct to said slots. ### Claim 13 (depends on 1, 3) The leading edge flap of claim 1 or 3 wherein: said first flap segment includes a plurality of passageways, located spanwise along the airfoil, connecting said bottom surface with said upper surface of said airfoil such that, during flight, relatively higher pressure in the vicinity of said lower surface is ejected over said upper surface for boundary layer control during flight when said leading edge flap is in the extended position. ### Claim 14 (depends on 1, 3) The leading edge flap of claim 1 or 3 wherein: said first flap segment includes a plurality of passageways terminating as nozzles, located spanwise along the airfoil and connecting said bottom surface with said upper surface of said airfoil such that, during flight, relatively higher pressure in the vicinity of said lower surface is ejected over said upper surface for boundary layer control during flight when said leading edge flap is in the extended position, and said leading edge is a torque tube containing a continuous spanwise passage therethrough, said torque tube containing a plurality of ports connecting said continuous passage to said plurality of passageways to direct pressurized air thereinto and augment the amount of relatively higher pressure air available for boundary layer control purposes. ### Claim 15 (depends on 14) The leading edge flap of claim 14, wherein baffle means if provided adjacent each of said ports to direct air flowing therethrough toward said nozzles.