# US 8,540,187 B2 · Muscle-powered aircraft with flapping wings > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 8,540,187 B2 - Document ID: US8540187B2 - Status: Granted - Kind: B2 - Application number: 12/746,903 - Filed: 2008-12-15 - Published: 2011-05-26 - Granted: 2013-09-24 - Earliest claimed: 2007-12-13 - Applicants: Nikolaus Pietrek - Inventors: Nikolaus Pietrek - Web page: https://patentgrep.com/patent/US8540187B2 ## CPC - B64C 33/00: Ornithopters - B64C: AEROPLANES; HELICOPTERS ## Abstract The invention relates to a muscle-powered ornithopter comprising a fuselage, a pair of flapping wings which have an alterable profile or a rudder in an outer wing region located at a distance from the fuselage, said alterable profile or rudder allowing the uplift to be modified in a predefined flow, and an elevator unit in which the deflection of the elevator can be modified. The pair of flapping wings and the fuselage are made of an elastic material, the elasticity of which allows the pair of flapping wings to be flapped. The flapping wings are curved downward in a resting position. The elasticity is calculated such that the flapping wings are urged into a neutral position during a flight because of the pilot's weight. The fuselage is designed to accommodate the pilot in an upright position relative to a longitudinal axis of the fuselage such that the pilot can apply stress to and relieve stress from the aircraft in phases by stretching and bending his or her legs. The ornithopter further comprises mechanisms which allow the alterable outer wing regions and the modifiable deflection of the elevator to be actuated in phase with the movement of the flapping wings. ## Claims ### Claim 1 A muscle-powered aircraft that comprises the following: a fuselage having an inner flexible frame that is elastically deformable transversely to the aircraft's longitudinal axis, a pair of flapping wings having an alterable profile or rudder in an outer wing region (II) at a distance from the fuselage enabling alteration of the uplift in a predetermined flow, and an elevator unit with alterable pitch elevator deflection, wherein the pair of flapping wings and the fuselage are shaped from an elastic material having an elasticity that makes possible a flapping motion of the pair of flapping wings in a rigid connection with the fuselage, wherein said rigid connection is rigid in all directions, wherein the flapping wings when in a resting position are curved downwards and wherein said elasticity is such that when in flight the flapping wings are forced into a neutral position by the weight of a pilot, wherein the fuselage is configured to accommodate the pilot in an upright position with respect to a longitudinal axis of the fuselage so that the pilot can apply stress to and relieve stress from the aircraft in phases by stretching and drawing in the legs, wherein the flexible inner frame surrounds the pilot on at least two sides and the flapping wings are mounted on said at least two sides, the aircraft with flapping wings further having mechanical devices which facilitate an actuation of the alterable profile or rudder in the outer wing regions and of the alterable pitch elevator deflection in phase with the movement of the flapping wings. ### Claim 2 (depends on 1) The aircraft with flapping wings according to claim 1, wherein the fuselage and the wings at least in part are shaped from a flexible monocoque structure. ### Claim 3 (depends on 1) The aircraft with flapping wings according to claim 1, wherein the alterable outer wing regions (II) are constituted by at least one rudder in the region of the trailing edge of the wing. ### Claim 4 (depends on 1) The aircraft with flapping wings according to claim 1, wherein the flapping wings have one or more parallel spars which are connected with the fuselage and which extend at least to the outer regions of the wings. ### Claim 5 (depends on 1) The aircraft with flapping wings according to claim 1, wherein the alterable outer wing regions and/or the pitch elevator deflection can be operated manually by the pilot via control rods and/or cable pulls. ### Claim 6 (depends on 1) The aircraft with flapping wings according to claim 1, wherein a shape of a covering of the flapping wings alters on moving the outer wing regions (II). ### Claim 7 (depends on 1) The aircraft with flapping wings according to claim 1, wherein a dampening element dampens the fuselage vibration. ### Claim 8 (depends on 7) The aircraft with flapping wings according to claim 7, wherein the dampening element for the fuselage is controllable. ### Claim 9 (depends on 1) The aircraft according to claim 1, wherein the elasticity of the flapping wings changes along one or more spars of the wing. ### Claim 10 (depends on 9) The aircraft according to claim 9, wherein the elasticity of the flapping wing increases across a portion of the area from a location (a) closer to the fuselage to a location (b) further away from the fuselage and/or the elasticity decreases across a further portion from a location (b) closer to the fuselage to a location (c) further away from the fuselage. ### Claim 11 A method of operating a muscle-powered aircraft that comprises the following: a fuselage having an inner flexible frame that is elastically deformable transversely to the aircraft's longitudinal axis, a pair of flapping wings having an alterable profile or rudder in an outer wing region (II) at a distance from the fuselage enabling alteration of the uplift in a predetermined flow, and an elevator unit with alterable pitch elevator deflection, wherein the pair of flapping wings and the fuselage are shaped from an elastic material having an elasticity that makes possible a flapping motion of the pair of flapping wings in a rigid connection with the fuselage, wherein the flapping wings when in a resting position are curved downwards and wherein said elasticity is such that when in flight the flapping wings are forced into a neutral position by the weight of a pilot, wherein the fuselage is configured to accommodate the pilot in an upright position with respect to a longitudinal axis of the fuselage so that the pilot can apply stress to and relieve stress from the aircraft in phases by stretching and drawing in the legs, wherein the flexible inner frame surrounds the pilot on at least two sides and the flapping wings are mounted on said at least two sides, the aircraft with flapping wings further having mechanical devices which facilitate an actuation of the alterable profile or rudder in the outer wing regions and of the alterable pitch elevator deflection in phase with the movement of the flapping wings, wherein the pilot applies stress to and relieves stress from the aircraft in phases by a leg movement. ### Claim 12 (depends on 11) The method according to claim 11, wherein the pilot operates the outer wing region (II) in phase with applying and relieving the stress. ### Claim 13 (depends on 11) The method according to claim 11, wherein the pilot completely relieves the stress from the aircraft in phases. ### Claim 14 (depends on 11) The method according to claim 11, wherein the pilot steers the aircraft by horizontal displacement of his body weight about a longitudinal and a lateral axis.