# US 11,046,413 B2 · Finlets for aircraft aft-body drag reduction > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 11,046,413 B2 - Document ID: US11046413B2 - Status: Granted - Kind: B2 - Application number: 16/052,193 - Filed: 2018-08-01 - Published: 2019-11-14 - Granted: 2021-06-29 - Earliest claimed: 2018-05-10 - Assignees: Vortex Control Technologies, LLC - Applicants: Vortex Control Technologies, LLC - Inventors: John Rick Hooker - Web page: https://patentgrep.com/patent/US11046413B2 ## CPC - B64C 1/0009: {Aerodynamic aspects} - B64C 23/06: by generating vortices - F15D 1/003: {comprising surface features, e.g. indentations or protrusions (F15D1/0055, F15D1/006 take precedence)} - F15D 1/009: {by means of vortex rings} - F15D 1/12: by influencing the boundary layer - Y02T 50/10: Drag reduction - B64C: AEROPLANES; HELICOPTERS - F15D: FLUID DYNAMICS, i.e. METHODS OR MEANS FOR INFLUENCING THE FLOW OF GASES OR LIQUIDS - Y02T: CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION ## Abstract A system and a method for reducing drag on the aft-fuselage of an aircraft are provided, which system and method utilize at least one finlet provided on each side of the aft-fuselage of an aircraft for reducing drag—on the aft-fuselage, which finlets are (i) positioned at the rear half of an upswept portion of the aft-fuselage starting at a breakline, (ii) positioned in the path of the vortices generated by the aft-fuselage, and (iii) oriented at 1 to 9 degrees angle relative to the local airflow about the aft-fuselage of the aircraft to straighten the airflow about the aft-fuselage. In addition, the finlets generate an induced secondary vortex having an opposite rotation direction relative to the rotation direction of the vortices generated by the aft-fuselage, thereby counteracting the vortices generated by the aft-fuselage. ## Claims ### Claim 1 A drag reducing system for an aircraft, comprising: at least one finlet attached to a rear half of an upswept portion of an aft-fuselage of the aircraft on each side of the aft-fuselage, wherein the upswept portion extends rearward starting at a breakline; wherein each finlet has a leading edge and a tail edge, each finlet being positioned nose-up relative to the direction of airflow about the aft-fuselage, and wherein each finlet is configured to reduce drag on the aircraft by providing a direct flow turning to move a vortex generated at the aft-fuselage by the airflow about the aft-fuselage, thereby straightening the vortex and reducing upsweep of the vortex, and wherein each finlet is configured to additionally reduce drag on the aircraft through generation of a secondary vortex oriented to induce downwash added to the vortex generated at the aft-fuselage, thereby further straightening the vortex generated at the aft-fuselage and reducing the upsweep of the vortex. ### Claim 2 (depends on 1) The system according to claim 1, wherein: at least one finlet is attached to a first side of the rear half of the upswept portion of the aft-fuselage of the aircraft; and at least two finlets are attached to a second side of the rear half of the upswept portion of the aft-fuselage of the aircraft. ### Claim 3 (depends on 2) The system according to claim 2, wherein: each finlet is positioned nose-up relative to the direction of airflow about the aft-fuselage at an angle in the range between 1 and 9 degrees. ### Claim 4 (depends on 2) The system according to claim 2, wherein: each finlet is at least approximately 25 inches in length. ### Claim 5 (depends on 2) The system according to claim 2, wherein: each finlet is at least approximately 2 inches in height. ### Claim 6 (depends on 2) The system according to claim 2, wherein: a leading-edge sweep for each finlet is in the range between 15 and 40 degrees, the leading-edge sweep being defined as an angle formed between a leading edge of a finlet and the height axis of the finlet. ### Claim 7 (depends on 2) The system according to claim 2, wherein: a spacing between respective centers of the at least two adjacent finlets on the second side of the aft-fuselage is in the range of 0.5 to 4 times the length of one of the at least two adjacent finlets. ### Claim 8 (depends on 2) The system according to claim 2, wherein: a distance between respective leading edges of at least two adjacent finlets on the second side of the aft-fuselage is in the range of 0.5 to 2 times the length of one of the at least two adjacent finlets. ### Claim 9 (depends on 1) The system according to claim 1, wherein: each finlet is at least approximately 25 inches in length. ### Claim 10 (depends on 1) The system according to claim 1, wherein: each finlet is at least approximately 2 inches in height. ### Claim 11 (depends on 1) The system according to claim 1, wherein: each finlet is positioned nose-up relative to the direction of airflow about the aft-fuselage at an angle in the range between 1 and 9 degrees. ### Claim 12 (depends on 1) The system according to claim 1, wherein: a leading edge sweep for each finlet is in the range between 15 and 40 degrees, the leading edge sweep being defined as an angle formed between a leading edge of a finlet and the height axis of the finlet. ### Claim 13 (depends on 1) The system according to claim 1, wherein: two adjacent finlets are provided on at least one side of the aft-fuselage, and a spacing between respective centers of the two adjacent finlets is in the range of 0.5 to 4 times the length of one of the two adjacent finlets. ### Claim 14 (depends on 1) The system according to claim 1, wherein: two adjacent finlets are provided on at least one side of the aft-fuselage, and a distance between respective leading edges of the two adjacent finlets is in the range of 0.5 to 2 times the length of one of the two adjacent finlets. ### Claim 15 (depends on 1) The system according to claim 1, wherein: a maximum of ten finlets are attached to the rear half of the upswept aft-fuselage portion of the aircraft on each side of the aft-fuselage.