Abstract: An air vehicle is provided including: a main lift generating wing arrangement having a port wing and a starboard wing, empennage and main propulsion system. The air vehicle further includes a distributed electrical propulsion (DEP) system having secondary electrical propulsion units coupled to each one of the port wing and the starboard wing. The main propulsion system is configured for providing sufficient thrust such as to enable powered aerodynamic flight of the air vehicle including at least: powered aerodynamic take off absent operation of the DEP system; and powered aerodynamic landing absent operation of the DEP system. The DEP system is configured for selectively providing at least augmented lift to the main lift generating wing arrangement in at least landing. A method for landing an air vehicle on a moving platform under separated wake conditions is also provided.

Abstract: There is provided a composite air vehicle system including: a first air vehicle capable of independent aerodynamic flight; a second air vehicle capable of independent aerodynamic flight; and at least one connector element configured for reversibly interconnecting the first air vehicle and the second air vehicle in tandem arrangement to provide a composite air vehicle capable of aerodynamic flight. The composite air vehicle system is configured for enabling at least in-flight separation of composite air vehicle into the first air vehicle and second air vehicle, and for enabling each one of the first air vehicle and said second air vehicle to operate independently of one another.

Abstract: A wing system is provided for an air vehicle, the air vehicle having a fuselage including a fuselage longitudinal axis. The wing system includes a set of wings, configured for transitioning between a stowed configuration and a deployed configuration. The set of wings includes a first said wing having a first wing tip, a first wing longitudinal axis, and a first pivot axis; and a second said wing having a second wing tip, a second wing longitudinal axis, and a second pivot axis. The first pivot axis and the second pivot axis are non-coaxial. In the stowed configuration, the first wing and the second wing are in overlying relationship such that at least a majority of a pressure surface of one wing is facing a suction surface of the other wing, and the first wing tip is spaced from the second wing tip by a first lateral spacing.

Abstract: A wing system is provided for an air vehicle, the wing system having a stowed configuration, a pre-deployed configuration, and a deployed configuration. The wing system includes two wings, each wing having aerofoil profiles and being pivotably deployable about a respective pivot axis between the pre-deployed configuration and the deployed configuration. In the stowed configuration the two wings are in first general superposed spatial relationship with respect to one another and are capable of being accommodated within an envelope having an envelope cross-sectional profile and a corresponding envelope cross-sectional area. In the pre-deployed configuration, the two wings are in second general superposed spatial relationship with respect to one another and capable of deploying to the deployed configuration. In the deployed configuration the wings are each capable of generating aerodynamic lift in an airstream.

Abstract: There is provided a composite air vehicle system including: a first air vehicle capable of independent aerodynamic flight; a second air vehicle capable of independent aerodynamic flight; and at least one connector element configured for reversibly interconnecting the first air vehicle and the second air vehicle in tandem arrangement to provide a composite air vehicle capable of aerodynamic flight. The composite air vehicle system is configured for enabling at least in-flight separation of composite air vehicle into the first air vehicle and second air vehicle, and for enabling each one of the first air vehicle and said second air vehicle to operate independently of one another.

Abstract: An air vehicle is provided including: a main lift generating wing arrangement having a port wing and a starboard wing, empennage and main propulsion system. The air vehicle further includes a distributed electrical propulsion (DEP) system having secondary electrical propulsion units coupled to each one of the port wing and the starboard wing. The main propulsion system is configured for providing sufficient thrust such as to enable powered aerodynamic flight of the air vehicle including at least: powered aerodynamic take off absent operation of the DEP system; and powered aerodynamic landing absent operation of the DEP system. The DEP system is configured for selectively providing at least augmented lift to the main lift generating wing arrangement in at least landing. A method for landing an air vehicle on a moving platform under separated wake conditions is also provided.

Abstract: Methods are provided for operating an air vehicle, the air vehicle including fixed wings configured to provide mild stall characteristics including a post-stall regime, and a propulsion system capable of generating a controllable thrust, the thrust being variable at least between an idle thrust and a maximum thrust. During a landing maneuver, the air vehicle is caused to attain an angle of attack corresponding to said post-stall regime, and during the landing maneuver, there is concurrently generated a thrust level of said thrust greater than said idle thrust to provide a thrust vector having a thrust lift force component at landing. Corresponding control systems are also provided, and air vehicles including such control systems are also provided.

Abstract: Methods are provided for operating an air vehicle having fixed wings. Such methods include the step of providing an operating map of angle of attack associated with the fixed wings with Reynolds number, including conditions of separated flow over the fixed wings and conditions of attached flow over the fixed wings. Such methods also include the step of using the operating map for guidance, causing the air vehicle to operate at least within a low Reynolds numbers range corresponding to the operating map, such as to avoid or minimize risk of causing the air vehicle to operate at conditions of separated flow over the fixed wings.

Abstract: Two element aerofoils are provided, having an aerofoil chord, a primary element having a first leading edge and a first trailing edge, a secondary element having a second leading edge and a second trailing edge, a gap between the primary element and the secondary element, and an axial overlap between the first trailing edge and the second leading edge. The secondary element is deflectable with respect to the primary element about a fixed hinge point by a flap deflection angle. The secondary element is configured to operate in airbrake mode when deflected by a respective the flap deflection angle corresponding to a design airbrake deflection angle wherein to generate an airbrake drag. In at least some examples, the axial overlap is numerically greater than ?0.5% of the aerofoil chord, at least for the design airbrake deflection angle. Also disclosed are methods for operating air vehicles, and methods for designing two-element aerofoils.

Abstract: Aerofoil accessories are provided, configured for selective attachment to a wing element, the wing element having an outer facing aerofoil surface and being based on at least one datum aerofoil section. Each accessory provides a modified geometric profile to a datum profile of the at least one aerofoil section when attached to the wing element. The accessories are each configured for having a substantially fixed geometric profile with respect to the at least one datum aerofoil section at least whenever said wing element is airborne with the respective accessory attached to the wing element. The modified geometric profile is such as to provide said wing element with the accessory attached thereto with a desired change in performance relative to a datum performance provided by the wing element absent the accessory. A kit is also provided for enhancing performance of a wing element in off-design conditions. A method is also provided for enhancing performance of a wing element in adverse conditions.

Abstract: A method for providing a controllable side force to an air vehicle having a vertical stabilizer arrangement includes (a) selectively causing the vertical stabilizer arrangement to generate a first side force in a first side direction to provide the controllable side force, the first side force inducing a corresponding first yaw moment in a first yaw direction; and (b) selectively providing to the air vehicle a second yaw moment in a second yaw direction, the second yaw moment being induced by a force component of an auxiliary force applied to the air vehicle, the force component being in a force direction that is non-parallel with respect to the first side direction and the force component being spaced from a center of gravity of the air vehicle; wherein the second yaw direction is opposed to the first yaw direction. Also disclosed is a corresponding auxiliary yaw generating system.

Abstract: Methods are provided for operating an air vehicle having fixed wings. Such methods include the step of providing an operating map of angle of attack associated with the fixed wings with Reynolds number, including conditions of separated flow over the fixed wings and conditions of attached flow over the fixed wings. Such methods also include the step of using the operating map for guidance, causing the air vehicle to operate at least within a low Reynolds numbers range corresponding to the operating map, such as to avoid or minimize risk of causing the air vehicle to operate at conditions of separated flow over the fixed wings.

Abstract: Methods are provided for operating an air vehicle, the air vehicle including fixed wings configured to provide mild stall characteristics including a post-stall regime, and a propulsion system capable of generating a controllable thrust, the thrust being variable at least between an idle thrust and a maximum thrust. During a landing maneuver, the air vehicle is caused to attain an angle of attack corresponding to said post-stall regime, and during the landing maneuver, there is concurrently generated a thrust level of said thrust greater than said idle thrust to provide a thrust vector having a thrust lift force component at landing. Corresponding control systems are also provided, and air vehicles including such control systems are also provided.

Abstract: Two element aerofoils are provided, having an aerofoil chord, a primary element having a first leading edge and a first trailing edge, a secondary element having a second leading edge and a second trailing edge, a gap between the primary element and the secondary element, and an axial overlap between the first trailing edge and the second leading edge. The secondary element is deflectable with respect to the primary element about a fixed hinge point by a flap deflection angle. The secondary element is configured to operate in airbrake mode when deflected by a respective the flap deflection angle corresponding to a design airbrake deflection angle wherein to generate an airbrake drag. In at least some examples, the axial overlap is numerically greater than ?0.5% of the aerofoil chord, at least for the design airbrake deflection angle. Also disclosed are methods for operating air vehicles, and methods for designing two-element aerofoils.

Abstract: A two element aerofoil, and wing element based thereon, is provided, including a primary aerofoil element including a leading edge of the aerofoil and a secondary aerofoil element including a trailing edge of the aerofoil. A gap is provided between the primary aerofoil element and the secondary aerofoil element. The primary aerofoil element has at least one of a profile, orientation and location with respect to a respective at least one of a profile, orientation and location of the secondary aerofoil element that is configured for minimizing or avoiding accretion of contaminant on the secondary aerofoil element when subjected to an airflow that includes the contaminant, at least at one design set of conditions. A method for designing a two element aerofoil is also provided.

Abstract: A method for providing a controllable side force to an air vehicle having a vertical stabilizer arrangement includes (a) selectively causing the vertical stabilizer arrangement to generate a first side force in a first side direction to provide the controllable side force, the first side force inducing a corresponding first yaw moment in a first yaw direction; and (b) selectively providing to the air vehicle a second yaw moment in a second yaw direction, the second yaw moment being induced by a force component of an auxiliary force applied to the air vehicle, the force component being in a force direction that is non-parallel with respect to the first side direction and the force component being spaced from a center of gravity of the air vehicle; wherein the second yaw direction is opposed to the first yaw direction. Also disclosed is a corresponding auxiliary yaw generating system.

Abstract: A two element aerofoil, and wing element based thereon, is provided, including a primary aerofoil element including a leading edge of the aerofoil and a secondary aerofoil element including a trailing edge of the aerofoil. A gap is provided between the primary aerofoil element and the secondary aerofoil element. The primary aerofoil element has at least one of a profile, orientation and location with respect to a respective at least one of a profile, orientation and location of the secondary aerofoil element that is configured for minimizing or avoiding accretion of contaminant on the secondary aerofoil element when subjected to an airflow that includes the contaminant, at least at one design set of conditions. A method for designing a two element aerofoil is also provided.

Abstract: Aerofoil accessories are provided, configured for selective attachment to a wing element, the wing element having an outer facing aerofoil surface and being based on at least one datum aerofoil section. Each accessory provides a modified geometric profile to a datum profile of the at least one aerofoil section when attached to the wing element. The accessories are each configured for having a substantially fixed geometric profile with respect to the at least one datum aerofoil section at least whenever said wing element is airborne with the respective accessory attached to the wing element. The modified geometric profile is such as to provide said wing element with the accessory attached thereto with a desired change in performance relative to a datum performance provided by the wing element absent the accessory. A kit is also provided for enhancing performance of a wing element in off-design conditions. A method is also provided for enhancing performance of a wing element in adverse conditions.