IL303322A

IL303322A - Air vehicle

Info

Publication number: IL303322A
Application number: IL303322A
Authority: IL
Inventors: Meir Mergi; Ronen Barsky; Yogev Kat
Original assignee: Israel Aerospace Ind Ltd; Meir Mergi; Ronen Barsky; Yogev Kat
Priority date: 2023-05-30
Filing date: 2023-05-30
Publication date: 2025-01-01
Also published as: WO2024246895A1

Description

AIR VEHICLE TECHNOLOGICAL FIELD The presently disclosed subject matter relates to air vehicles, in particular to air vehicles capable of vectored thrust flight as well as aerodynamic flight.

BACKGROUND There are a variety of air vehicles capable of vectored thrust flight as well as aerodynamic flight.

By way of non-limiting example, CN 112407270 discloses a tail stock type vertical take-off and landing aircraft without control surface control. The tail stock type vertical take-off and landing aircraft comprises a fuselage, and a nose, wings, wing tips, a power assembly and empennages which are mounted at the front part of the fuselage, wherein the nose is connected with the fuselage, the wings are connected to the middle section of the fuselage, the wing tips are installed at the ends of the wings and are conical, the power assembly comprises propellers connected with the wing tips and a driving device, and the empennages are located at the tail of the fuselage and distributed in a cross shape. The aircraft disclosed by the invention has two flight modes, namely a multi-rotor flight mode and a fixed-wing flight mode, has the characteristics of a multi-rotor aircraft, can realize vertical take-off and landing and hovering, also has the characteristics of a fixed-wing aircraft, and can realize high-speed flight and economic cruise.

Also by way of non-limiting example, US 2005/178879 discloses a power- operated tail-sitting type mixed layout vertical take-off and landing aircraft. The power- operated tail-sitting type mixed layout vertical take-off and landing aircraft is composed of a fuselage, airfoils, motors, propellers and landing gears; the fuselage axis coincides with the OX axis of a body axial system, the projections of the fuselage axis and the OX 029295874-06 axis in an XOY plane of the body axial system are distributed in an X shape; each airfoil on the fuselage is divided into several sections, sweepback angles and dihedral angles of all the sections are different from one another, and excellent pneumatic performance and maneuvering performance are achieved through positively-curved airfoil profiles and negatively-curved airfoil profiles. Four sets of propeller-motor power systems are installed on the four airfoils correspondingly, and the distances between the positions where the propeller-motor power systems are located and the OX axis of the body axial system are the same; and four power devices take off in an X-shaped quad-rotor mode in the vertical take-off and landing processes and complete conversion operation to enter a cruising state through different tensile forces of the motors or by being matched with maneuvering surfaces, and required maneuvering is completed through tensile force changing of the motors in the whole process.

Also by way of non-limiting example, CN 106927040 discloses a tailstock type quad-rotor tailless configuration aircraft capable of taking off and landing perpendicularly. The tailstock type quad-rotor tailless configuration aircraft capable of taking off and landing perpendicularly is composed of a fuselage, airfoils, vertical tails and power devices, wherein the airfoils are arranged on the two sides of the fuselage, the vertical tails are arranged on and below the tail portion of the fuselage correspondingly, and the center lines of the vertical tails on the upper portion and the lower portion and the axis of the fuselage are located in the same vertical plane. The wingtip portions of the airfoils and the wingtip portions of the vertical tails are provided with the power devices, and a rotary shaft of each power device is parallel to the axis of the fuselage. An auxiliary lifting wing is installed at the rear edge of each airfoil. A rudder is installed at the rear edge of each vertical tail. The wingtips of the airfoils and the wingtips of the vertical tails form four supporting points jointly, and by means of the four supporting points, the aircraft is docked on the ground in a vertically upward mode before the aircraft takes off and after the aircraft lands.

Also by way of non-limiting example, CN 108284950 discloses a four-ducted propeller powered fixed-wing unmanned aerial vehicle capable of achieving vertical takeoff and landing, and belongs to the field of unmanned aerial vehicles. The four-ducted propeller powered fixed-wing unmanned aerial vehicle capable of achieving vertical takeoff and landing comprises a structural unit, power units and a flight control and avionic 029295874-06 unit, wherein the structural unit comprises a fuselage, wings, control planes and tail supporting rods. The fuselage is positioned at a central position of the whole unmanned aerial vehicle Four wings are fixed to the fuselage. The adjacent wings of the four wings form included angles of 90 degrees. The power units are arranged on the tips of the four wings; the control planes are arranged on the four wings. The tail supporting rod is arranged on each wing. Each power unit comprises four sets of ducted propellers. A set of ducted propeller is arranged on each wing. The flight control and avionic unit is mounted inside the inner cavity of the fuselage.

Also by way of non-limiting example, US 11,420,737 is directed to a high speed vertical takeoff and landing (VTOL) aircraft that includes fixed wing flight capabilities. The high speed VTOL aircraft may include at least two thrust producing rotors located equidistant from a longitudinal axis of the aircraft on a main wing, and at least two thrust producing rotors located equidistant from a longitudinal axis of the aircraft on a vertical wing. By adjusting the speed and/or the pitch of the rotors, the aircraft can transition from a vertical flight configuration to a horizontal flight configuration and back.

Also by way of non-limiting example, US 9,567,075 discloses a multi-engine aircraft which is convertible from horizontal flight mode to a vertical flight mode. The aircraft comprises an aircraft fuselage defining a fuselage longitudinal axis, and the first and second wing attached to the fuselage. Each wing defines first and second wing segments. The first segments are translatable about the fuselage longitudinal axis, from a horizontal mode position adjacent the second wing segments to vertical fight mode wherein the first wing segment are substantially offset from the second wing segments. An aircraft propulsion unit is attached to each of the first and second wing segments. The propulsion units attached to a common wing being disposed in substantial axial alignment when the aircraft operates in a horizontal flight mode, and being substantially offset when the aircraft operates in a vertical flight mode.

Also by way of non-limiting example, US 2020/0031458 discloses an aerial vehicle, such as an unmanned aerial vehicle, that includes a fuselage having a forward end, an aft end, and a duct extending between said forward end and said aft end, the duct being oriented along a longitudinal axis of said fuselage; a primary propulsion unit mounted within said duct and generating lift for upward and downward motion while said 029295874-06 fuselage is in a substantially vertical orientation and thrust for forward motion while said fuselage is in a substantially horizontal orientation; a plurality of airfoils each having a proximal end attached at opposite sides of the fuselage, said airfoils providing lift during forward motion of said fuselage; and a plurality of secondary propulsion units generating thrust to tilt the fuselage between said substantially vertical orientation and said substantially horizontal orientation.

Also by way of non-limiting example, CN 106184738 discloses a detachable tailstock type vertical take-off and landing unmanned aerial vehicle. Wings and a fuselage can be detachably assembled. The wings and the fuselage can form two overall arrangement forms. According to the X-shaped overall arrangement form, two pairs of wings are mounted on the fuselage and are bilaterally symmetrical, and each pair of wings is of a longitudinal symmetry structure; and the included angle between the wings in each pair is 120 degrees, and the four wings form an X shape. According to the Y-shaped overall arrangement form, three wings are mounted on the fuselage, the included angel between every two adjacent wings is 120 degrees, and the three wings form a Y shape. The unmanned aerial vehicle of the X-shaped overall arrangement form is suitable for long-distance flight under a wind-free condition.

Also by way of non-limiting example, CN 108639328 discloses a tailstock type axisymmetric multi-propeller vertical take-off and landing unmanned aerial vehicle. According to the scheme, the tailstock type axisymmetric multi-propeller vertical takeoff and landing unmanned aerial vehicle comprises an unmanned aerial vehicle body assembly, a head cover assembly, a tail cover assembly, power propeller assemblies and a symmetric wing assembly. The tailstock type axisymmetric multi-propeller vertical take-off and landing unmanned aerial vehicle is characterized in that four wings are symmetrically arranged relative to an unmanned aerial vehicle body in a crossed shape; the power propeller assemblies are correspondingly contained on the four wings; landing gears with shock absorbing devices are used at the lower parts of the wings; in addition, the head cover assembly and the tail cover assembly are positioned at the two ends of the unmanned aerial vehicle body to reduce the air resistance in the cruise level flight process. According to the novel tailstock type axisymmetric multi-propeller vertical take-off and landing unmanned aerial vehicle, through differential control of thrust forces of the four propellers in the vertical taking-off and landing or hovering stage, the attitude 029295874-06 stabilization of the unmanned aerial vehicle is guaranteed; maneuvering actions, such as rolling and yawing, of the unmanned aerial vehicle are controlled by using trailing edge flaps and ailerons during horizontal flight.

Also by way of non-limiting example, CN 106240814 discloses a power-operated tail-sitting type mixed layout vertical take-off and landing aircraft. The power-operated tail-sitting type mixed layout vertical take-off and landing aircraft is composed of a fuselage, airfoils, motors, propellers and landing gears; the fuselage axis coincides with the OX axis of a body axial system, the projections of the fuselage axis and the OX axis in an XOY plane of the body axial system are distributed in an X shape; each airfoil on the fuselage is divided into several sections, sweepback angles and dihedral angles of all the sections are different from one another, and excellent pneumatic performance and maneuvering performance are achieved through positively-curved airfoil profiles and negatively-curved airfoil profiles; four sets of propeller-motor power systems are installed on the four airfoils correspondingly, and the distances between the positions where the propeller-motor power systems are located and the OX axis of the body axial system are the same; and four power devices take off in an X-shaped quad-rotor mode in the vertical take-off and landing processes and complete conversion operation to enter a cruising state through different tensile forces of the motors or by being matched with maneuvering surfaces, and required maneuvering is completed through tensile force changing of the motors in the whole process.

GENERAL DESCRIPTION According to a first aspect of the presently disclosed subject matter there is provided an air vehicle comprising:a fuselage defining a roll axis of the air vehicle;a fixed wing arrangement in fixed spatial disposition with respect to the fuselage;a propulsion system comprising at least four propulsion units, each one of said at least four propulsion units being mounted with respect to the wing system in lateral spaced relationship with respect to the roll axis, and wherein adjacent propulsion units are spaced circumferentially from one another about the roll axis;029295874-06 each said propulsion unit configured for generating a respective thrust along a respective thrust vector axis;wherein each respective thrust vector axis being in fixed inclined spatial orientation with respect to the roll axis such that the respective thrust has a nonzero thrust component defined on a plane orthogonal to the roll axis; and wherein the respective non-zero thrust component has a respective non-zero moment arm with respect to the roll axis such as to provide a respective roll moment about the roll axis.

For example, respective said non-zero thrust component of each pair of circumferentially adjacent said propulsion units are in mutually opposed rotational directions about the roll axis.

Additionally or alternatively, for example, respective said non-zero thrust component of each pair of diametrically opposed said propulsion units with respect to the roll axis are in the same rotational direction about the roll axis.

Additionally or alternatively, for example, respective said non-zero thrust component of one pair of diametrically opposed said propulsion units with respect to the roll axis are in a first rotational direction about the roll axis, and wherein respective said non-zero thrust component of another pair of diametrically opposed said propulsion units with respect to the roll axis are in a second rotational direction about the roll axis, wherein said first rotational direction is an opposite rotational direction with respect to the second rotational direction.

Additionally or alternatively, for example, the thrust vectors of the propulsion units are non-parallel with respect to one another.

Additionally or alternatively, for example, said propulsion system includes a port pair and a starboard pair of said propulsion units, and wherein for each one of said port pair and said starboard pair, the respective thrust vectors are converging in a forward direction towards a forward converging point when the air vehicle is viewed in side view. For example, said propulsion system includes a top pair and a bottom pair of said propulsion units, and wherein for each one of said top pair and said bottom pair, the respective thrust 029295874-06 vectors are diverging in a forward direction away from an aft diverging point when the air vehicle is viewed in top view.

Additionally or alternatively, for example, said propulsion system includes a top pair and a bottom pair of said propulsion units, and wherein for each one of said top pair and said bottom pair, the respective thrust vectors are converging in a forward direction towards a forward converging point when the air vehicle is viewed in top view. For example, said propulsion system includes a port pair and a starboard pair of said propulsion units, and wherein for each one of said port pair and said starboard pair, the respective thrust vectors are diverging in a forward direction away from an aft diverging point when the air vehicle is viewed in side view.

Additionally or alternatively, for example, for each propulsion unit, for a given magnitude of respective thrust along the respective thrust vector, the respective moment arm from the non-zero thrust component to the roll axis is maximized.

Additionally or alternatively, for example, each propulsion unit has a rotor axis. For example, the rotor axes of the propulsion units are non-parallel with respect to one another. Additionally or alternatively, for example, for each said propulsion unit, the respective rotor axis is co-axial with the respective thrust vector. Additionally or alternatively, for example, said propulsion system includes a port pair and a starboard pair of said propulsion units, and wherein for each one of said port pair and said starboard pair, the respective rotor axes are converging in a forward direction towards a forward converging point when the air vehicle is viewed in side view. For example, said propulsion system includes a top pair and a bottom pair of said propulsion units, and wherein for each one of said top pair and said bottom pair, the respective rotor axes are diverging in a forward direction away from an aft diverging point when the air vehicle is viewed in top view. Additionally or alternatively, for example, said propulsion system includes a top pair and a bottom pair of said propulsion units, and wherein for each one of said top pair and said bottom pair, the respective rotor axes are converging in a forward direction towards a forward converging point when the air vehicle is viewed in top view. For example, said propulsion system includes a port pair and a starboard pair of said propulsion units, and wherein for each one of said port pair and said starboard pair, the 029295874-06 respective rotor axes are diverging in a forward direction away from an aft diverging point when the air vehicle is viewed in side view.

Additionally or alternatively, for example, said propulsion system includes a first pair of diametrically opposed said propulsion units with respect to the roll axis, and a second pair of diametrically opposed said propulsion units with respect to the roll axis, wherein said propulsion units of the first pair are each configured to provide a roll control moment in a counter-clockwise direction, and wherein said propulsion units of the second pair are each configured to provide a roll control moment in a clockwise direction.

Additionally or alternatively, for example, a starboard top said propulsion unit and a port bottom said propulsion unit are each configured to provide a roll control moment in a counter-clockwise direction, and wherein a starboard bottom said propulsion unit and a port top said propulsion unit are each configured to provide a roll control moment in a clockwise direction.

Additionally or alternatively, for example, a starboard top said propulsion unit and a port bottom said propulsion unit are each configured to provide a roll control moment in a clockwise direction, and wherein a starboard bottom said propulsion unit and a port top said propulsion unit are each configured to provide a roll control moment in a counterclockwise direction.

Additionally or alternatively, for example, said wing system comprises a plurality of wings laterally projecting from the fuselage. For example, said wing system comprises four wings in X-arrangement. Additionally or alternatively, for example, the wings are devoid of control surfaces for providing aerodynamically generated control moments in one or more of pitch roll and yaw. Additionally or alternatively, for example, the air vehicle comprises an empennage axially spaced by an axial spacing with respect to said wings. For example, said axial spacing is at least the size of a width of a human hand.

Additionally or alternatively, for example, at least part of the fuselage has a diameter is such as to enable circumferentially to grasp the air vehicle via a human hand. For example, said human hand is of a 50th percentile male.

According to this aspect of the presently disclosed subject matter there is also provided an air vehicle comprising:029295874-06 a fuselage defining a roll axis of the air vehicle;four wings in X-arrangement with respect to the fuselage;four propulsion units, one propulsion unit being mounted with respect to each said wing in lateral spaced relationship with respect to the roll axis;each said propulsion unit configured for generating a respective thrust along a respective thrust vector axis;wherein each respective thrust vector axis being in fixed inclined spatial orientation with respect to the roll axis such that the respective thrust has a nonzero thrust component defined on a plane orthogonal to the roll axis; and wherein the respective non-zero thrust component has a respective non-zero moment arm with respect to the roll axis such as to provide a respective roll moment about the roll axis.

According to a second aspect of the presently disclosed subject matter, there is provided a control system to control operation of an air vehicle, wherein the air vehicle comprises a fuselage defining a roll axis, a fixed wing arrangement and a propulsion system including a plurality of propulsion units each mounted to the wing system in fixed spatial relationship to the wing system with respect to the roll axis, the control system comprising a processing unit and associated memory configured to generate one or more commands comprising:at least one first command operable to control an aggregate thrust generated by the propulsion system for enabling the air vehicle to operate in vectored thrust flight mode, aerodynamic flight mode, and transition mode,at least one second command operable to separately control individual thrusts of the individual propulsion units to provide control moments in at least roll during each one of said vectored thrust flight mode, aerodynamic flight mode, and transition mode.

According to the second aspect of the presently disclosed subject matter, there is also provided an air vehicle comprising a fuselage defining a roll axis, a fixed wing arrangement and a propulsion system including a plurality of propulsion units each mounted to the wing system in fixed spatial relationship to the wing system with respect 029295874-06 to the roll axis, and the control system as defined herein according to the second aspect of the presently disclosed subject matter.

According to the second aspect of the presently disclosed subject matter, there is also provided a method of controlling an air vehicle, wherein the air vehicle comprises a fuselage defining a roll axis, a fixed wing arrangement and a propulsion system including a plurality of propulsion units each mounted to the wing system in fixed spatial relationship to the wing system with respect to the roll axis, the method comprising, by a processing unit and associated memory operatively coupled to the air vehicle:generating at least one first command operable to control an aggregate thrust generated by the propulsion system for enabling the air vehicle to operate in vectored thrust flight mode, aerodynamic flight mode, and transition mode,generating at least one second command operable to separately control individual thrusts of the individual propulsion units to provide control moments in at least roll during each one of said vectored thrust flight mode, aerodynamic flight mode, and transition mode.

According to the second aspect of the presently disclosed subject matter, there is also provided a non-transitory storage device readable by a machine, tangibly embodying a program of instructions executable by the machine to perform operations of controlling operation of an air vehicle, wherein the air vehicle comprises a fuselage defining a roll axis, a fixed wing arrangement and a propulsion system including a plurality of propulsion units each mounted to the wing system in fixed spatial relationship to the wing system with respect to the roll axis, the operations comprising, by the machine:generating at least one first command operable to control an aggregate thrust generated by the propulsion system for enabling the air vehicle to operate in vectored thrust flight mode, aerodynamic flight mode, and transition mode,generating at least one second command operable to separately control individual thrusts of the individual propulsion units to provide control moments in at least roll during each one of said vectored thrust flight mode, aerodynamic flight mode, and transition mode. 029295874-06 According to a third aspect of the presently disclosed subject matter, there is provided a control system to control operation of an air vehicle, wherein the air vehicle comprises a fuselage, a fixed wing arrangement and a propulsion system including a plurality of propulsion units each mounted to the wing system in fixed spatial relationship to the wing system with respect to the roll axis, the control system comprising a processing unit and associated memory configured to generate one or more commands comprising:at least one first command operable to control an aggregate thrust generated by the propulsion system for enabling the air vehicle to operate in vectored thrust flight mode, aerodynamic flight mode, and transition mode,at least one second command operable to separately control individual thrusts of the individual propulsion units to provide control moments in at least pitch during transition mode from vectored thrust flight mode to aerodynamic flight mode;at least one modified first command operable to increase said aggregate thrust generated by the propulsion system to cause a vertical component of said aggregate thrust to match a weight of the air vehicle at a desired level of matching.

For example, said one or more commands further comprises at least one further modified first command operable to reduce said aggregate thrust generated by the propulsion system to cause summation of the vertical component of said aggregate thrust and an aerodynamic lift generated by the wings to match a weight of the air vehicle at said desired level of matching.

Additionally or alternatively, for example, said level of matching is one of the following: - 100%, wherein the air vehicle is correspondingly maintained at nominallyconstant altitude during the transition mode;- greater than 100%, wherein the air vehicle is correspondingly caused to climb altitude during the transition mode;- less than 100%, wherein the air vehicle is correspondingly caused to decrease altitude during the transition mode. 029295874-06 According to the third aspect of the presently disclosed subject matter, there is also provided an air vehicle comprising a fuselage defining a roll axis, a fixed wing arrangement and a propulsion system including a plurality of propulsion units each mounted to the wing system in fixed spatial relationship to the wing system with respect to the roll axis, and the control system as defined herein according to the third aspect of the presently disclosed subject matter.

According to the third aspect of the presently disclosed subject matter, there is also provided a method of controlling operation of an air vehicle, wherein the air vehicle comprises a fuselage, a fixed wing arrangement and a propulsion system including a plurality of propulsion units each mounted to the wing system in fixed spatial relationship to the wing system with respect to the roll axis, the method comprising, by a processing unit and associated memory operatively coupled to the air vehicle:generating at least one first command operable to control an aggregate thrust generated by the propulsion system for enabling the air vehicle to operate in vectored thrust flight mode, aerodynamic flight mode, and transition mode,generating at least one second command operable to separately control individual thrusts of the individual propulsion units to provide control moments in at least pitch during transition mode from vectored thrust flight mode to aerodynamic flight mode;generating at least one modified first command operable to increase said aggregate thrust generated by the propulsion system to cause a vertical component of said aggregate thrust to match a weight of the air vehicle at a desired level of matching.

For example, the method further comprises generating at least one further modified first command operable to reduce said aggregate thrust generated by the propulsion system to cause summation of the vertical component of said aggregate thrust and an aerodynamic lift generated by the wings to match a weight of the air vehicle at said desired level of matching.

Additionally or alternatively, for example, said level of matching is one of the following: 029295874-06 - 100%, wherein the air vehicle is correspondingly maintained at nominallyconstant altitude during the transition mode;- greater than 100%, wherein the air vehicle is correspondingly caused to climb altitude during the transition mode;- less than 100%, wherein the air vehicle is correspondingly caused to decrease altitude during the transition mode.

According to the third aspect of the presently disclosed subject matter, there is also provided a non-transitory storage device readable by a machine, tangibly embodying a program of instructions executable by the machine to perform operations of controlling operation of an air vehicle, wherein the air vehicle comprises a fuselage, a fixed wing arrangement and a propulsion system including a plurality of propulsion units each mounted to the wing system in fixed spatial relationship to the wing system with respect to the roll axis, the operations comprising, by the machine:generating at least one first command operable to control an aggregate thrust generated by the propulsion system for enabling the air vehicle to operate in vectored thrust flight mode, aerodynamic flight mode, and transition mode,generating at least one second command operable to separately control individual thrusts of the individual propulsion units to provide control moments in at least pitch during transition mode from vectored thrust flight mode to aerodynamic flight mode;generating at least one modified first command operable to increase said aggregate thrust generated by the propulsion system to cause a vertical component of said aggregate thrust to match a weight of the air vehicle at a desired level of matching.According to a fourth aspect of the presently disclosed subject matter, there is provided a control system to control operation of an air vehicle, wherein the air vehicle comprises a fuselage, a fixed wing arrangement and a propulsion system including a plurality of propulsion units each mounted to the wing system in fixed spatial relationship to the wing system with respect to the roll axis, the control system comprising a processing unit and associated memory configured to generate one or more commands comprising: 029295874-06 at least one first command operable to control an aggregate thrust generated by the propulsion system much higher than a weight of the air vehicle for enabling rapid vertical acceleration of the air vehicle while operating in vectored thrust flight mode,at least one modified first command operable to decrease said aggregate thrust generated by the propulsion system to cause a vertical component of said aggregate thrust to match a weight of the air vehicle at a desired level of matching,at least one second command operable to separately control individual thrusts of the individual propulsion units to provide control moments in at least pitch during transition mode from vectored thrust flight mode to aerodynamic flight mode.

Additionally or alternatively, for example, said level of matching is one of the following: - 100%, wherein the air vehicle is correspondingly maintained at nominallyconstant altitude during the transition mode;- greater than 100%, wherein the air vehicle is correspondingly caused to climb altitude during the transition mode;- less than 100%, wherein the air vehicle is correspondingly caused to decrease altitude during the transition mode.

According to the fourth aspect of the presently disclosed subject matter, there is also provided an air vehicle comprising a fuselage defining a roll axis, a fixed wing arrangement and a propulsion system including a plurality of propulsion units each mounted to the wing system in fixed spatial relationship to the wing system with respect to the roll axis, and the control system as defined herein according to the fourth aspect of the presently disclosed subject matter. 029295874-06 According to the fourth aspect of the presently disclosed subject matter, there is also provided a method of controlling operation of an air vehicle, wherein the air vehicle comprises a fuselage, a fixed wing arrangement and a propulsion system including a plurality of propulsion units each mounted to the wing system in fixed spatial relationship to the wing system with respect to the roll axis, the method comprising, by a processing unit and associated memory operatively coupled to the air vehicle:generating at least one first command operable to control an aggregate thrust generated by the propulsion system much higher than a weight of the air vehicle for enabling rapid vertical acceleration of the air vehicle while operating in vectored thrust flight mode,generating at least one modified first command operable to decrease said aggregate thrust generated by the propulsion system to cause a vertical component of said aggregate thrust to match a weight of the air vehicle at a desired level of matching,generating at least one second command operable to separately control individual thrusts of the individual propulsion units to provide control moments in at least pitch during transition mode from vectored thrust flight mode to aerodynamic flight mode.

For example, said one or more commands further comprises generating at least one further modified first command operable to reduce said aggregate thrust generated by the propulsion system to cause summation of the vertical component of said aggregate thrust and an aerodynamic lift generated by the wings to match a weight of the air vehicle at said desired level of matching.

Additionally or alternatively, for example, said level of matching is one of the following: - 100%, wherein the air vehicle is correspondingly maintained at nominallyconstant altitude during the transition mode;- greater than 100%, wherein the air vehicle is correspondingly caused to climb altitude during the transition mode;- less than 100%, wherein the air vehicle is correspondingly caused to decrease altitude during the transition mode.029295874-06 According to the fourth aspect of the presently disclosed subject matter, there is also provided a non-transitory storage device readable by a machine, tangibly embodying a program of instructions executable by the machine to perform operations of controlling operation of an air vehicle, wherein the air vehicle comprises a fuselage, a fixed wing arrangement and a propulsion system including a plurality of propulsion units each mounted to the wing system in fixed spatial relationship to the wing system with respect to the roll axis, the operations comprising, by the machine: generating at least one first command operable to control an aggregate thrust generated by the propulsion system much higher than a weight of the air vehicle for enabling rapid vertical acceleration of the air vehicle while operating in vectored thrust flight mode,generating at least one modified first command operable to decrease said aggregate thrust generated by the propulsion system to cause a vertical component of said aggregate thrust to match a weight of the air vehicle at a desired level of matching,generating at least one second command operable to separately control individual thrusts of the individual propulsion units to provide control moments in at least pitch during transition mode from vectored thrust flight mode to aerodynamic flight mode.

According to a fifth aspect of the presently disclosed subject matter, there is provided a method for landing an air vehicle, wherein the air vehicle comprises a fuselage, a fixed wing arrangement and a propulsion system including a plurality of propulsion units each mounted to the wing system in fixed spatial relationship to the wing system with respect to the roll axis, wherein the air vehicle is configured for operating in vectored thrust flight mode, aerodynamic flight mode, and transition mode, and wherein the air vehicle comprises a fuselage portion aft of the wing arrangement, the method comprising: (a) causing the air vehicle to operate in vectored thrust mode to reach an altitude corresponding to a height of an extended arm of a human operator and at a range proximal to the human operator;(b) causing the air vehicle to hover at said altitude; 029295874-06 (c) allowing the air vehicle to be grasped at said fuselage portion by the arm of the human operator.

For example, the method further comprises the step (d) of reducing a thrust generated by propulsion system to zero.

A feature of at least one example of the presently disclosed subject matter is that an air vehicle is provided capable of being operated in aerodynamic flight mode, vectored flight mode, and transition mode between the aerodynamic flight mode and the vectored flight mode, while having a relatively simple construction.

Another feature of at least one example of the presently disclosed subject matter is that an air vehicle is provided with no moving parts other than the rotors of the propulsion units.

Another feature of at least one example of the presently disclosed subject matter is that an air vehicle is provided with roll control that is essentially uncoupled with respect to pitch and/or yaw.

Another feature of at least one example of the presently disclosed subject matter is that an air vehicle is provided which is graspable by one hand of a user.

Another feature of at least one example of the presently disclosed subject matter is that an air vehicle is provided which is can be effectively landed by being grasped by one hand of a user.

Another feature of at least one example of the presently disclosed subject matter is that an air vehicle is provided configured for transitioning between the aerodynamic flight mode and the vectored flight mode at nominally constant altitude.

Another feature of at least one example of the presently disclosed subject matter is that an air vehicle is provided configured for transitioning the aerodynamic flight mode and the vectored flight mode after a period of rapid vertical acceleration and during subsequent gravitational deceleration within a nominally constant altitude. 029295874-06 BRIEF DESCRIPTION OF THE DRAWINGS In order to better understand the subject matter that is disclosed herein and to exemplify how it can be carried out in practice, examples will now be described, by way of non-limiting example only, with reference to the accompanying drawings, in which: Fig. 1 is a top-front-side isometric view of an air vehicle according to an example of the presently disclosed subject matter.

Fig. 2 is a front view of the example of Fig. 1.

Fig. 3 is a top view of the example of Fig. 1; Fig. 3Ais a lateral view of the example of Fig. 3 taken along a direction DD of Fig. 2 parallel to a root-to-tip direction of one wing of the air vehicle.

Fig. 4 is a side view of the example of Fig. 1.

Fig. 5 is a top-front-side isometric view of the example of Fig. 1 aft of plane PL of Fig. 4.

Fig. 6 is a detail of part of the example of Fig. 5 in top-front-side isometric view.

Fig. 7 is a detail of part of the example of Fig. 5 in front view.

Fig. 8 is a detail of part of the example of Fig. 5 in side view.

Fig. 9 is a detail of part of the example of Fig. 5 in top view.

Fig. 10A schematically illustrates in side view an alternative variation of the example of propulsion unit of the example of Fig. 1; Fig. 10Bschematically illustrates in top view the example of Fig. 10A Fig. 11 is an isometric exploded view of the example of Fig. 1.

Fig. 12Aschematically illustrates in front view an alternative variation of the example of Fig. 1; Fig. 12Bschematically illustrates in front view another alternative variation of the example of Fig. 1; Fig. 12Cschematically illustrates in front view another alternative variation of the example of Fig. 1. 029295874-06 Fig. 13 schematically illustrates in front view another alternative variation of the example of Fig. 1, Fig. 14 is a schematic representation of a control system of an air vehicle according to an example of the presently disclosed subject matter.

Fig. 15 is a flow chart of a method of controlling the air vehicle using a control system of an air vehicle according to an example of the presently disclosed subject matter.

Fig. 16Ais a flow chart of a method of controlling hover in vectored thrust mode of an air vehicle using a control system of the air vehicle according to an example of the presently disclosed subject matter; Fig. 16Bis a flow chart of a method of controlling climb of an air vehicle in vectored thrust mode using a control system of the air vehicle according to an example of the presently disclosed subject matter; Fig. 16Cis a flow chart of a method of controlling descent of an air vehicle in vectored thrust mode using a control system of the air vehicle according to an example of the presently disclosed subject matter.

Fig. 17Ais a side view of the example of Fig. 1 providing hover control in vectored thrust flight mode; Fig. 17Bis a side view of the example of Fig. 1 providing climb control in vectored thrust flight mode; Fig. 17Cis a side view of the example of Fig. 1 providing descent control in vectored thrust flight mode.

Fig. 18Ais a side view of the example of Fig. 1 providing pitch control in vectored thrust flight mode; Fig. 18Bis a top view of the example of Fig. 1 providing yaw control in vectored thrust flight mode; Fig. 18Cis a side view of the example of Fig. 1 providing roll control in vectored thrust flight mode.

Fig. 19Ais a flow chart of a method of controlling pitch in vectored thrust mode of an air vehicle using a control system of the air vehicle according to an example of the presently disclosed subject matter; Fig. 19Bis a flow chart of a method of controlling yaw of an air vehicle in vectored thrust mode using a control system of the air vehicle according to an example of the presently disclosed subject matter; Fig. 19Cis a flow chart of a method of controlling roll of an air vehicle in vectored thrust mode using a control system of the air vehicle according to an example of the presently disclosed subject matter.029295874-06 Fig. 20Ais a side view of the example of Fig. 1 providing constant forward speed control in aerodynamic flight mode; Fig. 20Bis a side view of the example of Fig. providing forward acceleration control in aerodynamic thrust flight mode; Fig. 20Cis a side view of the example of Fig. 1 providing forward deceleration control in aerodynamic flight mode.

Fig. 21Ais a flow chart of a method of controlling constant forward speed in aerodynamic mode of an air vehicle using a control system of the air vehicle according to an example of the presently disclosed subject matter; Fig. 21Bis a flow chart of a method of controlling forward acceleration of an air vehicle in aerodynamic flight mode using a control system of the air vehicle according to an example of the presently disclosed subject matter; Fig. 21Cis a flow chart of a method of controlling forward deceleration of an air vehicle in aerodynamic flight mode using a control system of the air vehicle according to an example of the presently disclosed subject matter.

Fig. 22Ais a side view of the example of Fig. 1 providing pitch control in aerodynamic flight mode; Fig. 22Bis a top view of the example of Fig. 1 providing yaw control in aerodynamic flight mode; Fig. 22Cis a side view of the example of Fig. providing roll control in aerodynamic flight mode.

Fig. 23Ais a flow chart of a method of controlling pitch in aerodynamic flight mode of an air vehicle using a control system of the air vehicle according to an example of the presently disclosed subject matter; Fig. 23Bis a flow chart of a method of controlling yaw of an air vehicle in aerodynamic flight mode using a control system of the air vehicle according to an example of the presently disclosed subject matter; Fig. 23Cis a flow chart of a method of controlling roll of an air vehicle in aerodynamic flight mode using a control system of the air vehicle according to an example of the presently disclosed subject matter.

Fig. 24Aschematically illustrates a side view of the example of Fig. 1 at one stage of a transition mode from vectored thrust flight mode to aerodynamic flight mode, according to a first example of the presently disclosed subject matter, in which the air vehicle is in vectored thrust mode; Fig. 24Bschematically illustrates the example of Fig. 24A at a subsequent stage of the transition mode including pitching; Fig. 24C schematically illustrates the example of Fig. 24B at a subsequent stage of the transition 029295874-06 mode including further pitching; Fig. 24Dschematically illustrates the example of Fig. 24C at a subsequent stage of the transition mode including further pitching and generation of significant aerodynamic lift; Fig. 24Eschematically illustrates the example of Fig. 24D wherein the air vehicle is in aerodynamic flight mode.

Fig. 25 is a flow chart of a method of controlling transition of an air vehicle from vectored thrust mode to in aerodynamic flight mode using a control system of the air vehicle according to a first example of the presently disclosed subject matter.

Fig. 26Aschematically illustrates a side view of the example of Fig. 1 at one stage of a transition mode from vectored thrust flight mode to aerodynamic flight mode, according to a second example of the presently disclosed subject matter, in which the air vehicle is in vectored thrust mode; Fig. 26Bschematically illustrates the example of Fig. 26A at a subsequent stage of the transition mode including pitching; Fig. 26C schematically illustrates the example of Fig. 26B at a subsequent stage of the transition mode including further pitching; Fig. 26Dschematically illustrates the example of Fig. 26C at a subsequent stage of the transition mode including further pitching; Fig. 26E schematically illustrates the example of Fig. 26D wherein the air vehicle is in aerodynamic flight mode.

Fig. 27 is a flow chart of a method of controlling transition of an air vehicle from vectored thrust mode to in aerodynamic flight mode using a control system of the air vehicle according to a second example of the presently disclosed subject matter.

Fig. 28 schematically illustrates an altitude vs range trajectory for an air vehicle using the method of the example of Fig. 25.

Fig. 29 schematically illustrates an altitude vs range trajectory for an air vehicle using the method of the example of Fig. 27. 029295874-06 DETAILED DESCRIPTION Referring to Fig. 1, a first example of an air vehicle according to a first aspect of the presently disclosed subject matter, is generally designated 100,and comprises a fuselage 200,wing system 300and propulsion system 500.

An orthogonal Cartesian axis system, including a roll axis R , a pitch axis P , and a yaw axis Y , can be defined with respect to the air vehicle 100.In at least this example, the roll axis Ris co-axial with the longitudinal axis LAof the air vehicle 100,which is coextensive with the fuselage 200.The pitch axis Pand the yaw axis Yare orthogonal to one another, and also orthogonal with respect to the roll axis R .

A yaw-pitch plane YPcan be defined along the yaw axis Yand the pitch axis P , and orthogonal to the roll axis R .

A yaw-roll plane YRcan be defined along the yaw axis Yand the roll axis R , and orthogonal to the pitch axis P .

A roll-pitch plane RPcan be defined along the roll axis Rand the pitch axis P , and orthogonal to the yaw axis Y .

The fuselage 200is, in at least this example, generally elongate, having a nose 210 and tail 290.Furthermore, while in at least this example, has a circular transverse crosssection, in at least some alternative variations of this example the fuselage 200can have any suitable cross-sectional shape, for example oval, elliptical, polygonal, and so on.

In at least this example, the fuselage 200is hollow, and accommodates a power pack 220(for example battery pack), communications module 230,guidance control, cables and so on.

Optionally, the fuselage 200can accommodate ordinance, for example explosives. Such ordinance can be configured for detonating on impact of the air vehicle 100,or for detonating responsive to receiving an appropriate signal from an external source via the communication module 230,or for detonating via a preset timer, for example.

In at least this example, the nose 210comprises a forward-looking camera 205, operatively coupled to the communications module, enabling video and/or still images captured by the camera 205to be transmitted externally via the communication module 230. 029295874-06 In at least some alternative variations of this example, the camera can be omitted, and/or, other cameras can be installed in other parts of the air vehicle 100.

In at least this example, the fuselage 200also accommodates a control system 250, operatively coupled to the communication module 230,as well as to the propulsion system 500.

The control system 250is configured for operating the propulsion system 500to enable the air vehicle 100to operate in vectored thrust mode VTM , in aerodynamic flight mode AFM , and in transition mode TRM , wherein the air vehicle 100transitions between the vectored thrust mode VTMand the aerodynamic flight mode AFM . Furthermore, the control system 250is configured for operating the propulsion system 500to generate control moments to the air vehicle 100in any one of or combination of pitch, yaw, and roll, in all modes of operation, including vectored thrust mode VTM , aerodynamic flight mode AFM , and in transition mode TRM . Furthermore, the control system 250is configured for operating the propulsion system 500to cause the air vehicle to: accelerate, or decelerate, or maintain a constant forward speed in aerodynamic mode; or to: accelerate, or decelerate, or climb, or descend, or maintain hover in vectored thrust mode.

In at least this example, the air vehicle 100includes a sensor package including a position sensor 253(e.g., GPS, etc.), a velocity sensor 256,altimeter 254,attitude sensor 255 (configured to provide data informative of at least one of a pitch, yaw and roll of the air vehicle 100) .

In at least this example, the fuselage 200comprises an empennage 270.In at least this example the empennage comprises port and starboard horizontal stabilizers 272,and upper and lower vertical stabilizers 274,arranged in cruciform "+" arrangement in proximity to the tail 290.However, in at least some alternative variations of this example, the respective air vehicle can omit an empennage, or, the respective air vehicle can have a different arrangement for the respective empennage.

In at least this example, the air vehicle 100is configured for enabling the air vehicle to be graspable by a hand of a user, for example when the air vehicle 100is in a hovering condition, or when it is desired for the air vehicle to take off from a ground location. Thus, in at least this example, the empennage 270is axially spaced from the 029295874-06 wing system 300along the longitudinal axis LAby a spacing ARX(Fig. 3). Such a spacing ARXis at least the size of a width of a hand, for example the width of a hand of a 50th percentile male. For example, such a spacing is not less than about 5cm. furthermore, the diameter of the fuselage in this section is also such as to enable circumferentially to grasp the air vehicle 100via a human hand, for example of a 50th percentile human male; for example, the diameter is about 10cm. Thus, according to an aspect of the presently disclosed subject matter, the air vehicle 100can be hand-held by a user, by grasping with one hand the aft end of the fuselage between the empennage 270 is and the wing system 300.This can be useful when it is desired to cause the air vehicle to take off in vectored thrust mode, without the need for a stand or other structures to hold the air vehicle until it is able to fly.

In at least this example, and referring also to Fig. 2, the wing system 300comprises four wings 320.The four wings include a pair of port wings 320P T, 320P B, and a pair of starboard wings 320S T, 320S B.

The four wings 320are in X-arrangement with respect to the fuselage 200.By X- arrangement is meant that the four wings 320when viewed in a direction along the longitudinal axis LAof the air vehicle 100,form a general "X" shape. Thus, in the X- arrangement, the top port wing 320PTis angled (along a plane parallel to the yaw-pitch plane YP ) with respect to the bottom port wing 320PB , by a port wing angle 0P , and, the top starboard wing 320STis angled (along a plane parallel to the yaw-pitch plane YP ) with respect to the bottom starboard wing 320SB , by a starboard wing angle 0S .

In at least this example, port wing angle 0Pand the starboard wing angle 0Sare each about 40º. However, in at least some alternative variations of this example, the respective port wing angle 0Pand the starboard wing angle 0Scan be any desired angle within the range 30º to 60º or 90º±5º.

Referring to Fig. 2, the top port wing 320PTand the top starboard wing 320ST intersect at a first point PT1that is vertically spaced from the longitudinal axis LA ; the bottom port wing 320PBand the bottom starboard wing 320SBintersect at a second point PT2that is vertically spaced from the longitudinal axis LA . An imaginary rectilinear line joining the first point PT1and the second point PT2intersects the longitudinal axis LA and/or roll axis R .029295874-06 In at least this example, the top port wing 320PTis overlying the bottom port wing 320PBalong a direction parallel to the yaw axis Y , and the top starboard wing 320STis overlying the bottom starboard wing 320SBalong a direction parallel to the yaw axis Y .

In at least this example, and referring also to Fig. 3, the wings 320have zero sweep, and have a rectangular planform, with a uniform chord distribution from the respective root 321to the respective tip 329.However, in at least some alternative variations of this example, the respective wing can have a non-zero sweep angle, and/or can have a non- rectangular planform, for example trapezoidal.

In at least this example the wings 320have a camber and the respective chords are inclined with respect to the longitudinal axis LAat a non-zero incidence angle of about 3.5º such that when the air vehicle 100is traveling at zero angle of attack α in straight horizontal flight, the aerodynamic lift Lgenerated by the wings 320balances the weight Wof the air vehicle.

In at least this example, the wings 320are devoid of any movable control surfaces, and of any actuators that would otherwise be required for operating such control surfaces. Thus, the wings have a fixed geometry during all stages (of aerodynamic flight mode, during transition mode and during vectored flight mode, including while performing one or more of yaw, pitch and roll maneuvers during any one of aerodynamic flight mode, transition mode and vectored flight mode.

Furthermore, the wings 320are affixed to the fuselage 200in fixed spatial relationship, and thus the wings are not movable or pivotable with respect to the fuselage 200,at least when the air vehicle 100is assembled and ready for flight.

In at least this example, the propulsion system 500comprises four propulsion units 550.Where necessary herein to distinguish the propulsion units 550from one another, the propulsion units 550are individually designated herein also with reference numerals 550PT , 550PB , 550ST , 550SBwhich respectively refer to the port top propulsion unit, the port bottom propulsion unit, the starboard top propulsion unit, and the starboard bottom propulsion unit. In at least some alternative variations of this example, the propulsion system can comprise more than four propulsion units. For example, one or more additional propulsion units can be provided in which each respective thrust vector is parallel with the 029295874-06 roll axis Rof the air vehicle. Additionally or alternatively, two or more propulsion units can be provided for each wing, wherein for example the respective thrust vectors are parallel to one another for each set of propulsion units on a respective wing.

In at least this example, each propulsion unit 550comprises a ducted fan arrangement, including a respective fan (not shown), rotatably mounted about a respective rotational axis RAin a generally cylindrical duct 554,having a respective duct inlet 553and a respective duct outlet 555.

In at least this example, the propulsion units 550are electrically powered, and an electric motor (not shown) is accommodated within the respective duct 554,the motor shaft being co-axial with the respective rotational axis RA . The respective fan (not shown) is mounted to the respective motor shaft to turn therewith when the electric motor is operating and turning the shaft. The respective fan and motor are concentrically mounted within the respective duct 554via a plurality of struts 558.

In at least this example the duct inlet 553is dimensioned such as to prevent or minimize the risk of a human hand and fingers being inserted into the ducted fan arrangement, at least such that otherwise could allow the fingers to come into contact with the internal fan, and thus potentially cause injury to the user and/or damage the propulsion unit 550.For example, the circumferential spacing between adjacent struts 558can be smaller than for example the width of a hand of a 50th percentile male, i.e., of an adult human male. For example, such a spacing is not greater than about 5cm. Additionally or alternatively, the fan is axially displaced from the forward edge of the respective inlet duct inlet 553by a spacing greater than the length between the outermost fingertip and the base of the thumb of a hand of a 50th percentile male, i.e., of an adult human male. For example, such a spacing is not less than about 5cm.

In at least this example, a ratio of the diameter of the forward edge of the respective inlet duct inlet 553to an axial length of the duct 554along the respective rotor axis RAis about 1. However, in at least some alternative variations of this example, the ratio of the diameter of the forward edge of the respective inlet duct inlet to an axial length of the respective duct along the respective rotor axis can be different from about 1. 029295874-06 In at least some alternative variations of this example, each propulsion unit can be instead configured as a propeller-based propulsion unit, or as a turbojet-based propulsion unit or as a propfan-based propulsion unit; additionally or alternatively, each respective propulsion unit can be powered by electrically power or liquid fuel where suitable, or can include a hybrid power source including both electrical power and liquid fuel.

Each propulsion unit 550thus generates a respective thrust Talong a respective thrust vector TV . In at least this example, the thrust vector TVis co-axial with the respective rotational axis RA .

According to this aspect of the presently disclosed subject matter, the thrust vector direction for each propulsion units 550is fixed with respect to air vehicle 100,and the air vehicle 100is not capable of changing spatial orientation of the thrust vectors with respect to air vehicle 100,particular during aerial operation thereof.

For each propulsion unit 550,the respective thrust Tcan be considered as acting on a point PTon the respective rotational axis RA . In at least this example, the axial location of the respective duct outlet 555along the respective rotational axis RAdefines the respective point PT .

In at least this example, the respective points PTof the four propulsion units 550lie on a thrust plane TPparallel to the yaw-pitch plane YP .

In at least this example, the thrust plane TPintersects the roll axis Rat or close to the longitudinal location of the center of gravity CGof the air vehicle 100.For example, the thrust plane TPintersects the roll axis Rat a longitudinal location aft of the center of gravity CGof the air vehicle 100,by a spacing which is about 20 % of the wing chord. Alternatively, the thrust plane TPcan instead intersect the roll axis Rat any other suitable longitudinal location fore or aft of the center of gravity CGof the air vehicle 100.

In at least this example, the air vehicle is aerodynamically stable, and has a static margin of about 12% of the wing chord.

Each propulsion unit 550is fixedly mounted with respect to the fuselage 200in laterally spaced relationship with respect to the roll axis R , via the wing arrangement 300. 029295874-06 In particular, in at least this example, each propulsion unit 550is fixedly mounted to a respective wing 320in the aforesaid laterally spaced relationship with respect to the roll axis R . The lateral spacing between each propulsion unit 550and the roll axis Rprovides a moment arm MAfor roll, as will become clearer herein.

In at least this example, each propulsion unit 550is fixedly mounted to the respective wing tip 329of the respective wing 320.

In at least this example, and referring in particular to Fig. 3A, Fig. 5 and Fig. 6, in the aforesaid laterally spaced relationship with respect to the roll axis R , each propulsion units 550is fixedly mounted to the respective wing 320such as to ensure that respective thrust vector TVis inclined with respect to the roll axis Rin a manner such that the respective thrust Thas a non-zero thrust component TCdefined on a reference plane PL orthogonal to the roll axis R . In addition, the respective thrust Thas a non-zero thrust component TRparallel to the roll axis R .

Furthermore, in at least this example, and referring also to Fig. 7, in the aforesaid laterally spaced relationship with respect to the roll axis R , the non-zero thrust component TCalong the reference plane PLhas a non-zero moment arm MA(magnitude MA0)with respect to the roll axis R , the moment arm MAalso being defined along the reference plane PL .

The reference plane PLis at least parallel to the yaw-pitch plane YP , and can be located at any suitable location along the roll axis R .

For example, the reference plane PLcan intersect the roll axis Rat or close to the longitudinal location of the center of gravity CGof the air vehicle 100.Thus, in at least this example, the thrust plane TPand the reference plane RPare co-planar. However, in at least some alternative variations of this example, the thrust plane TPand the reference plane RP are axially spaced from one another along the roll axis via a desired spacing.

In at least this example, while the non-zero thrust component TCis defined on the reference plane PL , the non-zero thrust component TCis inclined with respect to the pitch axis Pand with respect to the yaw axis Y . The non-zero thrust component TCcan thus be resolved into a first thrust component TCYparallel to the yaw axis Y , and a second thrust component TCPparallel to the pitch axis P .029295874-06 In at least this example, and referring also to Fig. 8 and Fig. 9, for each propulsion unit 550,the respective first thrust component TCYis directed towards the roll axis R(in side view), while the respective second thrust component TCPis directed away from the roll axis R(in top view).

Thus, in at least this example, the aforesaid laterally spaced relationship with respect to the roll axis Ris achieved by orienting the propulsion units 550such that the respective thrust vectors TVare non-parallel to one another.

Referring to Fig. 2 and Fig. 4 in particular, the port pair of adjacent propulsion units 550PT , 550PB , and the starboard pair of adjacent propulsion units 550ST , 550SB , are oriented with respect to the roll axis Rsuch that in each such pair the respective thrust vectors TVare non-parallel to one another. Furthermore, in each such pair, the respective thrust vectors TVare converging in a forward direction (in a plane parallel to the yaw-roll plane YR , i.e., in the side view illustrated in Fig. 4) towards a forward converging point FCP . It is to be noted that the forward converging point FCPis not on the longitudinal axis LA , but rather laterally displaced therefrom.

Referring to Fig. 2 and Fig. 3 in particular, the top pair of adjacent propulsion units 550PT , 550ST , and the bottom pair of adjacent propulsion units 550PB , 550SB , are oriented with respect to the roll axis Rsuch that in each such pair the respective thrust vectors TV are non-parallel to one another. Furthermore, in each such pair, the respective thrust vectors TVare diverging in a forward direction (in a plane parallel to the roll-pitch plane RP , i.e., in the top view illustrated in Fig. 3) by a respective first vector angle XHwith respect to the roll axis R , away from an aft diverging point ADP . It is to be noted that the aft converging point ACPis not on the longitudinal axis LA , but rather vertically displaced therefrom.

It is to be noted that in at least some alternative variations of this example, the port pair of adjacent propulsion units 550PT , 550PB , and the starboard pair of adjacent propulsion units 550ST , 550SB , are oriented with respect to the roll axis Rsuch that in each such pair the respective thrust vectors TVare diverging in a forward direction (in a plane parallel to the yaw-roll plane YR ) away from an aft diverging point. Concurrently the top pair of adjacent propulsion units 550P T, 550S T, and the bottom pair of adjacent propulsion units 550P B, 550S B, are oriented with respect to the roll axis Rsuch that in each such pair 029295874-06 the respective thrust vectors TVare converging in a forward direction (in a plane parallel to the roll-pitch plane RP ) towards a forward converging point.

Referring again to Fig. 7, the non-zero thrust component TCis inclined to the yaw axis Y(along the reference plane PL ) by an inclination angle e0,which is related to the relative magnitudes of the first thrust component TCYand second thrust component TCPas follows: e0= arctan ( TCP/ TCY ) The moment arm MAis orthogonal to the non-zero thrust component TC , thereby generating a roll control moment MRabout the roll axis R . Furthermore, in at least this example, the respective point PTis located at the extremity of the moment arm MA . Accordingly, for a given magnitude of respective thrust Talong the respective thrust vector TV , the magnitude MA0of the respective moment arm MAfrom the non-zero thrust component TCto the roll axis Ris maximized.

According to an aspect of the presently disclosed subject matter, the moment arm MAfor any particular magnitude of port wing angle ePand the starboard wing angle e Sfor the respective wing system, can be maximized by matching the inclination angle e 0to half the magnitude of the port wing angle ePor of the starboard wing angle e Ssuch that an imaginary line ILconnecting the respective point PTto the roll axis R(along the reference plane PL ) is also at the inclination angle e0with respect to the pitch axis P , as illustrated in Fig. 7. Thus, in at least this example, such an imaginary line ILand the moment arm MA coincide with one another, i.e., are co-axial.

In at least some alternative variations of this example, the respective moment arm MAdoes not pass through the respective point PT . In such cases the respective roll moment that can be generated about the roll axis Ris correspondingly less than when the respective moment arm passes through the respective point PT . Thus, for example, in at least some such cases, the port pair of adjacent propulsion units 550P T, 550P B, and the starboard pair of adjacent propulsion units 550S T, 550S B, can be oriented with respect to the roll axis R such that in each such pair the respective thrust vectors TVare diverging or converging in a forward direction (in a plane parallel to the yaw-roll plane YR ) away from an aft diverging point; while concurrently the top pair of adjacent propulsion units 550P T, 550S T, and the 029295874-06 bottom pair of adjacent propulsion units 550P B, 550S B, are oriented with respect to the roll axis Rsuch that in each such pair the respective thrust vectors TVare parallel to one another (in a plane parallel to the roll-pitch plane RP ). In other such cases, the port pair of adjacent propulsion units 550PT , 550PB , and the starboard pair of adjacent propulsion units 550ST , 550SB , are oriented with respect to the roll axis Rsuch that in each such pair the respective thrust vectors TVare parallel with one another (in a plane parallel to the yaw-roll plane YR ); while concurrently the top pair of adjacent propulsion units 550PT , 550ST , and the bottom pair of adjacent propulsion units 550PB , 550SB , are oriented with respect to the roll axis R such that in each such pair the respective thrust vectors TVare converging or diverging in a forward direction (in a plane parallel to the roll-pitch plane RP ) towards a forward converging point.

Referring again to Fig. 2, the aforementioned spatial relationship is such that the starboard top propulsion unit 550STand the port bottom propulsion unit 550PBeach provide a roll control moment MRin a counter-clockwise direction in the view seen in this figure, while the starboard bottom propulsion unit 550SBand the port top propulsion unit 550PTeach provide a roll control moment MRin a clockwise direction in the view seen in this figure.

Thus, when the thrust Tgenerated by each of the propulsion units 550is the same with respect to one another, the net clockwise roll control moment MRand the net counterclockwise roll control moment MRcancel each other and there is no net roll control moment MRabout the roll axis R .

In order to exercise a pure pitch maneuver (i.e., excluding concurrent roll and/or yaw) in the nose-down direction, the propulsion system 500is controlled (for example via the control system 250)by causing the starboard top propulsion unit 550STand the port top propulsion unit 550PTto each generate an increased thrust (equal to one another), as compared with the thrust generated by the starboard bottom propulsion unit 550SBand the port bottom propulsion unit 550PB(also equal to one another). The resulting nose-down pitch moment is greater than the resulting nose-up pitch moment, thereby generating a net nose-down pitch moment about the pitch axis P .

Conversely, in order to exercise a pure pitch maneuver (i.e., excluding concurrent roll and/or yaw) in the nose-up direction, the propulsion system 500is controlled (for 029295874-06 example via the control system 250)by causing the starboard bottom propulsion unit 550SB and the port bottom propulsion unit 550PBto each generate an increased thrust (equal to one another), as compared with the thrust generated by the starboard top propulsion unit 550TBand the port top propulsion unit 550PT(also equal to one another). The resulting nose-up pitch moment is greater than the resulting nose-down pitch moment, thereby generating a net nose-up pitch moment about the pitch axis P .

Each one of the aforesaid net nose-up moment about the pitch axis Pand the aforesaid net nose-down moment about the pitch axis Pcan be generated during vectored thrust flight mode, during transition mode, and during aerodynamic flight mode.

In order to exercise a pure yaw maneuver (i.e., excluding concurrent roll and/or pitch) in the port direction, the propulsion system 500is controlled (for example via the control system 250)by causing the starboard top propulsion unit 550STand the starboard bottom propulsion unit 550SBto each generate an increased thrust (equal to one another), as compared with the thrust generated by the port top propulsion unit 550PBand the port bottom propulsion unit 550PB(also equal to one another). The resulting yaw moment to port is greater than the resulting yaw moment to starboard, thereby generating a net port yaw moment about the yaw axis Y .

Conversely, in order to exercise a pure yaw maneuver (i.e., excluding concurrent roll and/or pitch) in the starboard direction, the propulsion system 500is controlled (for example via the control system 250)by causing the port top propulsion unit 550PBand the port bottom propulsion unit 550PBto each generate an increased thrust (equal to one another), as compared with the thrust generated by the starboard top propulsion unit 550STand the starboard bottom propulsion unit 550SB(also equal to one another). The resulting yaw moment to starboard is greater than the resulting yaw moment to port, thereby generating a net starboard yaw moment about the yaw axis Y .

Each one of the aforesaid net port moment about the yaw axis Yand the aforesaid net starboard moment about the yaw axis Ycan be generated during vectored thrust flight mode, during transition mode, and during aerodynamic flight mode.

Referring again to Fig. 2, in at least this example, the starboard top propulsion unit 550STand the port bottom propulsion unit 550PBeach generate a respective roll moment 029295874-06 MRin a counter clockwise direction (in the front view of Fig. 2), while the starboard bottom propulsion unit 550SBand the port top propulsion unit 550PTeach generate a respective roll moment MRin a clockwise direction (in the front view of Fig. 2). Since the respective moment arms MAare the same for the four propulsion units 550,when the four propulsion units 550generate equal thrust Tone to the other, the clockwise roll moments and the counter clockwise roll moments cancel each other out and there is no net roll moment generated.

To exercise a pure roll maneuver (i.e., excluding concurrent pitch and/or yaw) in the counter clockwise direction, the propulsion system 500is controlled (for example via the control system 250)by causing the starboard top propulsion unit 550STand the port bottom propulsion unit 550PBto each generate an increased thrust (equal to one another), as compared with the thrust generated by the starboard bottom propulsion unit 550S B and the port top propulsion unit 550PT(also equal to one another). The resulting counter clockwise roll moment is greater than the resulting clockwise roll moment, to thereby generate a net counter clockwise roll moment about the roll axis R .

Conversely, to exercise a pure roll maneuver (i.e., excluding concurrent pitch and/or yaw) in the clockwise direction, the propulsion system 500is controlled (for example via the control system 250)by causing the starboard bottom propulsion unit 550SBand the port top propulsion unit 550PTto each generate an increased thrust (equal to one another), as compared with the thrust generated by the starboard top propulsion unit 550STand the port bottom propulsion unit 550PB(also equal to one another). The resulting clockwise roll moment is greater than the resulting counter clockwise roll moment, thereby generating a net clockwise moment about the roll axis R .

Each one of the aforesaid net counter clockwise moment about the roll axis Rand the aforesaid net clockwise moment about the roll axis Rcan be generated during vectored thrust flight mode, during transition mode, and during aerodynamic flight mode.

It is to be noted that in the aforesaid counter clockwise pure roll maneuver (in which a net counter clockwise moment about the roll axis R ) or the aforesaid clockwise pure roll maneuver (in which a net clockwise moment about the roll axis R ) are generated, the starboard bottom propulsion unit 550SBand the port top propulsion unit 550PTgenerate equal thrust one to the other, and while the starboard top propulsion unit 550STand the port 029295874-06 bottom propulsion unit 550PBgenerate equal thrust one to the other. However, in such cases, the propulsion system 500does not concurrently generate any concurrent net pitching moment or any concurrent yaw moment, and thus there is no respective coupling, since: - the total forward thrust generated by the top pair of propulsion units 550ST , 550PT is equal to the total forward thrust generated by the bottom pair of propulsion units 550SB , 550PB , and thus no net pitch moment is generated; - the total forward thrust generated by the starboard pair of propulsion units 550ST , 550SBis equal to the total forward thrust generated by the port pair of propulsion units 550PT , 550PB , and thus no net yaw moment is generated.

It is readily evident from the above that the propulsion system 500can be operated (via the control system 250)to provide any desired maneuver in pitch and/or roll and/or yaw by suitably controlling the relative levels of thrust generated by each one of the four propulsion units 550to provide the desired concurrent combination of any two or more of pitch moments, roll moments, and yaw moments.

It is to be noted that the propulsion system 500generates sufficient total thrust via the four propulsion units 550to maintain the air vehicle in each one of aerodynamic flight mode, transition mode, and vectored flight mode. Thus, when there is a need for generating control moments in one or more of roll, pitch and yaw, the control system 250controls the thrust generated by each one of the propulsion units 550to, on the one hand together generate the total thrust required for maintaining the air vehicle in aerodynamic flight mode, transition mode, or vectored flight mode, while concurrently providing different relative levels of thrust to enable the desired roll, pitch and/or yaw moments to be generated.

As disclosed above, in at least this example, the thrust vector TVis co-axial with the respective rotational axis RA . However, in at least some alternative variations of this example, the thrust vector TVis parallel with, and laterally displaced with respect to, the respective rotational axis RA . In at least some other alternative variations of this example, and referring to Fig. 10A and Fig. 10B for example, each respective propulsion units 550' can be configured such that the respective thrust vector TVcan be, instead, non co-axial with the respective rotational axis RA . For example, the thrust vector TVis at a first angle ^ Hwith respect to the respective rotational axis RAalong a plane parallel to the roll-pitch 029295874-06 plane RP(i.e., in top view), and at a second angle ^ Vwith respect to the respective rotational axis RAalong a plane parallel to the yaw-roll plane YR(i.e., in side view). The first angle ^ Hand the second angle ^ V , taken together with the orientation of the respective rotor axis RA' , are such as to orient the respective thrust vector TVwith respect to the roll axis Rat the respective first vector angle XHand the respective second vector angle XV , respectively. For example, in at least one such example, the respective rotational axis RA'can be parallel to the roll axis R , and thus the first angle (^ Hand the second angle (^ Vrespectively correspond to the respective first vector angle XHand the respective second vector angle XV .

For example, in at least this example, since the port wing angle 0Pand the starboard wing angle 0Sare each less than 90º, the respective second vector angle XVhas a greater absolute magnitude than the first vector angle XH . For example, in at least this example the respective second vector angle XVhas a greater absolute magnitude of about 7.5º, and in at least some alternative variations of this example can be in the range from about 2º to about 10º, for example. For example, in at least this example the respective first vector angle XH has a greater absolute magnitude of about 5º, and in at least some alternative variations of this example can be in the range from about 1º to about 8º, for example.

According to another aspect of the presently disclosed subject matter, the air vehicle 100can be constructed in a modular manner, to enable quick and easy assembly, even in the field. According to this aspect of the presently disclosed subject matter, the air vehicle 100 can be provided in a disassembled manner, which enables compact packing of the air vehicle 100into a small volume, and the various air vehicle parts can be assembled together to provide the air vehicle.

Referring to Fig. 11, a first example of an air vehicle according to this aspect of the presently disclosed subject matter corresponds to the air vehicle 100disclosed herein and with reference to Figs. 1 to 10, mutatis mutandis, in the disassembled configuration, and the air vehicle 100is assembled from a plurality of parts including: a fuselage part 1200 , a top wing part 250,a bottom wing 1320 , and a battery pack 1400 .

The fuselage part 1200essentially corresponds to the fuselage 200mutatis mutandis, wherein a top section 1210and a bottom section 1220of the fuselage 200are essentially cutout to allow access into the fuselage. 029295874-06 The top wing part 250comprises the starboard top wing 320S T, the starboard top propulsion unit 550ST , the port top wing 320PTand the port top propulsion unit 550PT , and a top wing interconnector 1305 . The top wing interconnector 1305interconnects the starboard top wing 320STand the port top wing 320PT . The top wing interconnector 1305 comprises a bottom zone 1306configured for being affixed with respect to the top section 1210 . The bottom zone 1306and the top section 1210are configured for enabling quick assembly between the fuselage section 1200and the top wing part 250.For example, one or both of the bottom zone 1306and the top section 1210comprises a suitable fixing arrangement for enabling such fixation. For example, such fixation can be carried out using fasteners, for example screws or bolts; alternatively, the bottom zone 1306and the top section 1210can be shaped or include suitable elements that enable the bottom zone 1306 and the top section 1210to engage together without the need for fasteners.

The bottom wing part 1320comprises the starboard bottom wing 320SB , the starboard bottom propulsion unit 550SB , the port bottom wing 320PBand the port bottom propulsion unit 550PB , and a bottom wing interconnector 1325 . The bottom wing interconnector 1325interconnects the starboard bottom wing 320SBand the port bottom wing 320PB . The bottom wing interconnector 1325comprises a top zone 1326configured for being affixed with respect to the bottom section 1220 . The top zone 1326and the bottom section 1220are configured for enabling quick assembly between the fuselage section 1200 and the bottom wing part 1320 . For example, one or both of the top zone 1326and the bottom section 1220comprises a suitable fixing arrangement for enabling such fixation. For example, such fixation can be carried out using fasteners, for example screws or bolts; alternatively, the top zone 1326and the bottom section 1220can be shaped or include suitable elements that enable the top zone 1326and the bottom section 1220to engage together without the need for fasteners.

While in the above examples, the respective wing system 300is in the form of an X- wing arrangement, in at least some alternative variations of these examples, the respective wing system can include different wing arrangements.

For example, referring to Fig. 12A, in one such example, the respective air vehicle 100Acomprises a respective fuselage 200A , a respective wing system 300A , and a propulsion system 500A , similar to the air vehicle 100,fuselage 200,wing system 300and 029295874-06 propulsion system 500,as described herein mutatis mutandis, with some differences as disclosed herein. In the example of Fig. 12A, the wing system 300Acomprises a single port wing 320Pand a single starboard wing 320S , each having a pair of wing tip extensions 330A . In each one of the port wing 320Pand the starboard wing 320S , the two respective wing extensions 330Aproject vertically in opposite directions. The propulsion system 500A includes at least four propulsion units 550A , similar to the propulsion units 550,mutatis mutandis. Each propulsion unit 550Ais affixed to a free end of a respective wing extension 330Aat a suitable orientation with respect thereto such that the respective fixed thrust vector is at a respective laterally spaced relationship with respect to the roll axis R . The respective thrust generated along the thrust vector for each propulsion unit 550Ahas a respective nonzero thrust component along a respective reference plane orthogonal to the roll axis R , and this non-zero thrust component has a non-zero moment arm (defined along the reference plane) with respect to the roll axis R , in a similar manner to the example disclosed herein and illustrated in Figs. 1 to 11, mutatis mutandis.

In another example, and referring to Fig. 12B, the respective air vehicle 100B comprises a respective fuselage 200B , a respective wing system 300B , and a propulsion system 500B , similar to the air vehicle 100,fuselage 200,wing system 300and propulsion system 500,as described herein mutatis mutandis, with some differences as disclosed herein. In the example of Fig. 12B, the wing system 300Bcomprises an upper wing 320T(having port and starboard wing portions) and a bottom wing 320B(having port and starboard wing portions), the two wings 320Tand 320Bbeing joined together at the respective port wing tips and at the respective starboard wing tips via wing tip extensions 330B . The propulsion system 500Bincludes at least four propulsion units 550B , similar to the propulsion units 550,mutatis mutandis. Each propulsion unit 550Bis affixed to the wing tips of the upper wing 320Tand the lower wing 320Bat a suitable orientation with respect thereto such that the respective fixed thrust vector is at a respective laterally spaced relationship with respect to the roll axis R . The respective thrust generated along the thrust vector for each propulsion unit 550Bhas a respective non-zero thrust component along a respective reference plane orthogonal to the roll axis R , and this non-zero thrust component has a non-zero moment arm (defined along the reference plane) with respect to the roll axis R , in a similar manner to the example disclosed herein and illustrated in Figs. 1 to 11, mutatis mutandis. 029295874-06 In yet another example, and referring to Fig. 12C, the respective air vehicle 100C comprises a respective fuselage 200C , a respective wing system 300C , and a propulsion system 500C , similar to the air vehicle 100,fuselage 200,wing system 300and propulsion system 500,as described herein mutatis mutandis, with some differences as disclosed herein. In the example of Fig. 12C, the wing system 300Ccomprises an annular wing (also referred to as a cylindrical wing or as a ring wing) having an upper wing segment 320UCand a lower wing segment 320LC , the two wing segments being joined together at the respective port wing tips and at the respective starboard wing tips. The wing segments 320UCand 320LC are connected to the fuselage 200Cvia struts 270C . The propulsion system 500Cincludes at least four propulsion units 550C , similar to the propulsion units 550,mutatis mutandis. A pair of propulsion unit 550Care fixed to each one of the upper wing 320U C and the lower wing 320B(for example at 45° to the vertical as seen in the view shown in Fig. 12C) at a suitable orientation with respect thereto such that the respective fixed thrust vector is at a respective laterally spaced relationship with respect to the roll axis R . The respective thrust generated along the thrust vector for each propulsion unit 550Chas a respective non-zero thrust component along a respective reference plane orthogonal to the roll axis R , and this non-zero thrust component has a non-zero moment arm (defined along the reference plane) with respect to the roll axis R , in a similar manner to the example disclosed herein and illustrated in Figs. 1 to 11, mutatis mutandis.

While in the above examples, the respective air vehicle comprises a single fuselage, in at least some alternative variations of these examples, the respective air vehicle can include more than one fuselage. For example, the single fuselage of the examples shown in any one of Figs. 1 to 11, 12A, 12B, 12C can be replaced with two or more fuselages and connected to the respective wing system in a similar manner as disclosed herein mutatis mutandis. Other arrangements are also possible.

For example, referring to Fig. 13, in another such example, the respective air vehicle 100Dcomprises a respective wing system 300C , and a propulsion system 500C , similar to the air vehicle 100,wing system 300and propulsion system 500,as described herein mutatis mutandis, and the air vehicle 100Dcomprises two fuselages 200D , each fuselage 200D being similar to the fuselage 200as described herein mutatis mutandis, with some differences as disclosed herein. The two fuselages 200Dare laterally spaced from one another, on either side of the roll axis R . In the example of Fig. 11D, the wing system 300D 029295874-06 comprises an upper wing 320TDand a bottom wing 320BD . The two wings are connected to each fuselage 200Dat the respective port wing tips and at the respective starboard wing tips via wing tip extensions 330D . The propulsion system 500Dincludes at least four propulsion units 550D , similar to the propulsion units 550,mutatis mutandis. Each propulsion unit 550Dis affixed to the wings tips of the upper wing 320TDand the lower wing 320BDat a suitable orientation with respect thereto such that the respective fixed thrust vector is at a respective laterally spaced relationship with respect to the roll axis R . The respective thrust generated along the thrust vector for each propulsion unit 550Dhas a respective non-zero thrust component along a respective reference plane orthogonal to the roll axis R , and this non-zero thrust component has a non-zero moment arm (defined along the reference plane) with respect to the roll axis R , in a similar manner to the example disclosed herein and illustrated in Figs. 1 to 11, mutatis mutandis.

As disclosed above, the air vehicle 100is configured to operate in vectored thrust mode VTM , in aerodynamic flight mode AFM , and in transition mode TRM . While the following disclosure is based on the example illustrated in Figs. 1 to 11, it applies, mutatis mutandis, to the other examples disclosed herein, including the examples illustrated in Fig. 12A, Fig. 12B, Fig. 12C and Fig. 13.

According to another aspect of the presently disclosed subject matter there is provided a method for operating an air vehicle.

Attention is drawn to Fig. 14 which includes a schematic representation of an example of a control system 250of the air vehicle 100.

Control system 250includes a processing unit 251and an associated memory 252. Various modules depicted in the control system 250can be implemented using the processing unit 251and the associated memory 252.

The control system 250is operable to receive data from various sensors, such as for example position sensor 253(e.g., GPS, etc.), velocity sensor 256,altimeter 254, attitude sensor 255(configured to provide data informative of at least one of a pitch, yaw and roll of the air vehicle 100) . This list is not limitative and optionally other sensors can communicate with control system 250. 029295874-06 Control system 250includes a controller 260configured to control operation of each of the propulsion units 550.The controller 260can generate a command which is common for all propulsion units 550,and/or can generate a command specific to each of the propulsion units 550.

The commands generated by the controller 260can include a command for controlling a magnitude of a thrust of each of the propulsion units 550.For example, this can include controlling a rpm of the respective rotor arrangement of each propulsion unit 550.

Control system 250can include, and/or communicate with, a flight controller 260, which is responsible inter alia of computing desired navigation parameters (such as position, velocity, trajectory, altitude, etc.) of the air vehicle 100over time. The navigation parameters can be compliant with a flight plan stored in a database (not represented). In other examples, navigation parameters can be controlled by an external central control 269(e.g., controlled at least partially by a human operator) operatively and remotely coupled with the control system 250.For example, the central control 269 can be located on the ground, at sea or in the air, and can be static or mobile. In some examples, the air vehicle 100can be controlled using autonomous navigation managed by the control system 250,and/or navigation commands can be transmitted from the central control 269to the control system 250(e.g., to correct autonomous navigation of the air vehicle 100,or, to navigate the air vehicle 100to the final destination without autonomous navigation).

Depending on the flight plan or mission of the air vehicle 100,the controller 260 can generate appropriate commands to control the air vehicle 100according to a desired flight mode complying with the flight plan, as explained hereinafter.

According to at least some examples, the air vehicle 100comprises communications module 230for emitting and/or receiving data towards and from, respectively, the central control 269.

According to at least some examples, if the air vehicle 100is at least partly controlled remotely from the central control 269,at least part of the steps performed by the control system 250can be performed by a remote controller (which also operates on 029295874-06 a processing unit) located at the central control 269.The remote controller can communicate with the air vehicle 100via the communications module 230,in order to perform the required steps. The remote controller can receive data from the air vehicle 100,such as data measured by at least a subset of the air vehicle sensors.

The control system 250accommodated in the air vehicle 100can then communicate the orders (signals) received from the remote controller e.g., to the propulsion system 500of the air vehicle 100.

For example, control of magnitude of the thrust of the propulsion units 550can be performed by the remote controller which communicates with the air vehicle 100.

According to some examples, control system 250is split into a first control subsystem embedded in the air vehicle 100and a second control sub-system located in the remote central control 269.

According to some examples, data computed in the air vehicle 100(such as by its sensors and/or by its control system 250)can be displayed at the remote central control 269,for example for a human operator who can send remote commands to the air vehicle 100.

Attention is now drawn to Figs. 15, 16A, 16B, 16C, 19A, 19B, 19C, 21A, 21B, 21C, 23A, 23B, 23C, which schematically illustrates various examples of possible method of operation of the control system 250.

According to some examples, each such method can include e.g., obtaining data informative of a desired flight mode of the air vehicle. Examples of flight modes include e.g., vectored thrust mode VTM(including vertical take-off, vertical landing, hovering), aerodynamic flight mode AFM(including aerodynamic forward flight), transition mode TRM(including transitioning from vectored thrust mode VTMto aerodynamic flight mode AFM , and transitioning from aerodynamic flight mode AFMto vectored thrust mode VTM ), climb, descent, acceleration and deceleration (in either vectored thrust mode VTM , aerodynamic flight mode AFMor transition mode TRM ), manoeuvring in pone or more of pitch, yaw and roll (in either vectored thrust mode VTM , aerodynamic flight mode AFMor transition mode TRM ), and so on. 029295874-06 It is to be noted that while the following methods of operation are disclosed herein (for example with reference to Figs. 14 to 29) in relation to the air vehicle of Fig. 1, the respective methods can also be carried out in a similar manner, mutatis mutandis, by any other suitable air vehicle configuration that comprises a fuselage defining a roll axis, a fixed wing arrangement and a propulsion system including a plurality of propulsion units each mounted to the wing system in fixed spatial relationship to the wing system with respect to the roll axis, and in which the air vehicle is configured for enabling the air vehicle to operate in vectored thrust flight mode, aerodynamic flight mode, and transition mode.

In any case, the desired flight mode can be computed, for example by the flight controller 265.Data informative of the desired flight mode can include desired parameters characterizing the desired flight mode (e.g., desired trajectory, position, velocity, or other parameters over time).

Referring to Fig. 15, an example of a method 2000according to this aspect of the presently disclosed subject matter includes generating (operation 2010 ) a first command for controlling the aggregate forward thrust TTgenerated by propulsion system 500,and in particular, a magnitude of the aggregate forward thrust TT . As disclosed above, in at least some examples, the first command can include a desired rpm level for each of the respective rotors of the propulsion units 550.

The method includes generating (operation 2020 ) a second command for separately controlling the individual thrusts TUof the propulsion units 550to selectively provide differential thrusts, one from the other, while the propulsion system 500 concurrently provides the aforementioned desired level of aggregate forward thrust TT , to thereby enable generating control moments in one or more of pitch, yaw and roll. The second command can include a desired change in rpm for the respective rotors of the propulsion units 550.

It should be noted that operations 2010to 2020can be performed concurrently, or can be performed in the order illustrated in Fig. 15 or in a different order from the order depicted in Fig. 15. 029295874-06 In at least this example, the first command 2010and the second command 2020 can be generated and/or transmitted as a unified command.

In some examples, the aggregate forward thrust TTand/or differential thrusts of the propulsion units 550under control is/are already compliant with the desired flight mode and is therefore not changed. In such cases, an explicit command to maintain current state of aggregate forward thrust TTand/or differential thrusts can be generated and/or it is prevented from generating a new command for varying aggregate forward thrust TTand/or differential thrusts.

The first command and second commands are calibrated to provide a coordinated control of the propulsion units 550,ensuring operation of the air vehicle 100according to the desired flight mode. Various examples are provided hereinafter.

According to some examples, a magnitude of a thrust of the propulsion units 550 is controlled to generate the aggregate forward thrust TTin a vertical direction required for enabling vectored thrust flight to the air vehicle 100,i.e., to enable the air vehicle 100 to operate in vectored thrust mode VTM . In other words, the propulsion units 550can provide sufficient vertical thrust to at least balance the weight Wof the air vehicle 100.

The propulsion units 550can also be concurrently controlled to generate control moments in one or more of pitch, roll and yaw to the air vehicle 100to thereby control attitude of the air vehicle 100in pitch, roll and/or yaw, in order to reach a desired attitude of the air vehicle 100.

According to at least some examples, it is possible to use the propulsion units 550 for controlling variation of the altitude of the air vehicle 100,controlling attitude of the air vehicle 100(along at least one of pitch axis, roll axis, yaw axis), ensuring forward flight, and so on, as disclosed herein.

According to at least some examples, vertical thrust generated by the propulsion units 550is controlled to be sufficient to balance weight of the air vehicle 100,in particular when the air vehicle 100is operated in vectored thrust mode VTM , and during some portions of operation in transition mode TRM . This can be obtained, for example, by selecting a sufficient rpm for the rotors of the propulsion units 550. 029295874-06 According to at least some examples, it is desired to induce a climb of the air vehicle 100,for example to cause the air vehicle 100to climb to an altitude in vectored thrust mode VTM , from a previous flight condition in which the air vehicle 100was not climbing (for example a flight condition in which the air vehicle 100is hovering or descending) or in which the air vehicle 100was climbing at a different rate to the climb rate currently being desired (for example, in order to increase climbing rate with respect to the previous climbing rate).

In at least some examples, the method can include increasing the aggregate forward thrust TTof the propulsion units 550when the air vehicle 100is operated in vectored thrust mode VTM , or during some portions of operation in transition mode TRM , to maintain the aggregate forward thrust TTabove a predefined threshold. For example, such a threshold can correspond to the weight Wof the air vehicle 100.

Accordingly, according to at least one aspect of the presently disclosed subject matter, the air vehicle 100has a maximum thrust to weight ratio TWR , i.e., maximum available aggregate forward thrust TTmaxto weight Wratio significantly greater than 1 . For example, the thrust to weight ratio TWRis greater than 2, for example 3. For example each motor generates 5kg, and weight is 10 kg. During aerodynamic flight mode AFM the TWRcan be less than 1.

Vectored Thrust Mode In vectored thrust mode VTM , the propulsion system 500is operated to generate sufficient aggregate forward thrust TTfrom the propulsion units 550to maintain the air vehicle 100airborne, i.e., to at least balance the weight Wof the air vehicle 100during hover, to allow the air vehicle 100to accelerate and/or climb, or to decelerate and/or reduce altitude, while the wing system 300is concurrently not generating any lift, or generating very little lift . In vectored thrust mode VTM , the roll axis Ris nominally vertical, or angularly inclined to the vertical such that the vertical component of the aggregate forward thrust TTis still sufficient to maintain the air vehicle 100airborne without aerodynamic lift assistance from the wing system 300,i.e., to enable balancing the weight Wof the air vehicle 100during hover, or to allow the air vehicle 100to accelerate and/or climb, or to decelerate 029295874-06 and/or reduce altitude, while the wing system 300is concurrently not generating any lift, or generating very little lift. In addition, while in vectored thrust mode VTM , the air vehicle 100is able to maneuver in one or more of pitch, roll or yaw, by suitably and differentially controlling the magnitude of the respective thrust Tgenerated by each of the propulsion units 550,as disclosed herein.

Thus, referring to Fig. 16A and Fig. 17A, in pure hover vectored thrust mode, in an example of a method 3000Aaccording to this aspect of the presently disclosed subject matter an altitude of the air vehicle 100is maintained substantially constant over time. In some examples, this can include maintaining the air vehicle 100hovering over a fixed area. According to this method, a respective first command 3010Ais generated and sent to the propulsion system 500such as to generate an aggregate forward thrust TThaving a magnitude nominally equal to the weight Wof the air vehicle 100.Concurrently, no control moments are to be generated, and thus, this example of the method excludes generating a respective second command (corresponding to second command 2020 ) to provide differential thrusts between the propulsion units 550.

Changes in altitude are provided by selectively increasing or decreasing the aggregate forward thrust TTuntil the desired rate of climb is achieved, after which the aggregate forward thrust TTis balanced with the air vehicle weight W , followed by deceleration to eliminate climb at the desired altitude.

Referring to Fig. 16B and Fig. 17B, in pure climb/acceleration vectored thrust mode, in an example of a method 3000Baccording to this aspect of the presently disclosed subject matter a respective first command 3010Bis generated and sent to the propulsion system 500such as to generate an aggregate forward thrust TThaving a magnitude greater than the weight Wof the air vehicle 100.Concurrently, no control moments are to be generated, and thus, this example of the method excludes generating a respective second command (corresponding to second command 2020 ) to provide differential thrusts between the propulsion units 550.

It is to be noted that the climb/acceleration vectored thrust mode can also be used for vertical lift-off of the air vehicle 100from a launch site. In at least one example, the air vehicle 100can be held in a nominally vertical position (i.e., with the roll axis R nominally vertical), either manually or using a suitable cradle.029295874-06 Referring to Fig. 16C and Fig. 17C, in pure descent/deceleration vectored thrust mode, in an example of a method according to this aspect of the presently disclosed subject matter a respective first command 3010Bis generated and sent to the propulsion system 500such as to generate an aggregate forward thrust TThaving a magnitude less than the weight Wof the air vehicle 100.Concurrently, no control moments are to be generated, and thus, this example of the method excludes generating a respective second command.

It is to be noted that the descent/deceleration vectored thrust mode can also be used for vertical landing of the air vehicle 100at a landing site.

Referring to Fig. 18A, Fig. 18B, Fig. 18C, Fig. 19A, Fig. 19B and Fig. 19C, in hover vectored thrust mode including a change in the special attitude of the air vehicle 100,in examples of a method 4000 A, 4000 B, 4000 C according to this aspect of the presently disclosed subject matter a respective first command 4010is generated and sent to the propulsion system 500such as to generate an aggregate forward thrust TThaving a magnitude nominally equal to the weight Wof the air vehicle 100.Thus, responsive to the first command 4010 , each propulsion unit 550generates a respective basic propulsion unit thrust TUthat is nominally a quarter of the aggregate forward thrust TT . i.e.: TU= 0.25* TT Concurrently, and depending on what control moments are to be generated, this example of the method includes generating a respective second command and sending the second command to the propulsion units 550to execute the desired turning moment while still maintain the same level of aggregate forward thrust TT .

Referring in particular to Fig. 18A and Fig. 19A, when it is desired to provide a turning moment in pitch a second command 4020Ais generated for causing the set of top propulsion units to generate different thrust from the thrust generated by the set of bottom propulsion units.

For example, when it is desired to provide a turning moment in pitch, nose down (with respect to the air vehicle 100) , during hover and while generating an aggregate forward thrust TT , the second command 4020Acauses the starboard top propulsion unit 550S T and the port top propulsion unit 550PTto each generate an increased thrust +AT 029295874-06 (equal to one another) over the respective basic propulsion unit thrust TU . Thus, the total thrust TAgenerated by each one of the starboard top propulsion unit 550STand the port top propulsion unit 550PTis determined as follows: TA= TU+ AT Concurrently, the second command 4020Acauses the starboard bottom propulsion unit 550SBand the port bottom propulsion unit 550PBto each generate a decreased thrust -AT(equal to one another) over the respective basic propulsion unit thrust TU . Thus, the total thrust TBgenerated by each one of starboard bottom propulsion unit 550SBand the port bottom propulsion unit 550PBis determined as follows: TB= TU- AT The differential thrust between the two top propulsion units 550and the two bottom propulsion units generates a nose down pitch turning moment MP , in view of the respective moment arms about the center of gravity CG , while the aggregate thrust TT remains unchanged, since the total thrust is: 2*TA+ 2*TB= 2* TU+ 2*AT+ 2* TU– 2*AT= 4*TU= TT The magnitude of the increase/decrease in thrust I AT I will depend on how fast the turning moment is desired to be.

A reverse turning moment in pitch can then be applied when the desired pitch angle has been attained in order to maintain the desired pitch angle. Such a reverse turning moment in pitch can be provided by generating an appropriate second command 4020A in which the thrust is increased in the two bottom propulsion units, and concurrently decreased in the two top propulsion units.

It is to be noted that as a non-zero pitch angle is attained, and the roll axis rotates away from vertical, the thrust vector of the aggregate forward thrust TTis also rotated away from vertical. Thus, to maintain hover, the aggregate forward thrust TTneeds to be increased (via the first command 4010 ) such that the vertical component of the aggregate forward thrust TTnominally equals the weight W . This maneuver will also result in the air vehicle moving in a lateral direction in view of the horizonal component of the aggregate forward thrust TT . 029295874-06 Providing a turning moment in pitch, nose up (with respect to the air vehicle 100) , during hover and while generating an aggregate forward thrust TT , is essentially the reverse of providing a nose-up pitch moment, and starts with the second command 4020A causing the starboard bottom propulsion unit 550S B and the port bottom propulsion unit 550P B to each generate an increased thrust +AT(equal to one another) over the respective basic propulsion unit thrust TU , and concurrently the second command 4020Acausing the starboard top propulsion unit 550S T and the port top propulsion unit 550P T to each generate a decreased thrust -AT(equal to one another) over the respective basic propulsion unit thrust TU .

Providing a turning moment in pitch, nose up or nose down, during acceleration/climb, is similar to that as disclosed herein regarding hover, mutatis mutandis, the main difference being that the respective aggregate forward thrust TTis maintained greater than the weight Wof the air vehicle 100.

Providing a turning moment in pitch, nose up or nose down, during deceleration/descent, is similar to that as disclosed herein regarding hover, mutatis mutandis, the main difference being that the respective aggregate forward thrust TTis maintained less than the weight Wof the air vehicle 100.

Referring in particular to Fig. 18B and Fig. 19B, when it is desired to provide a turning moment in yaw, a second command 4020Bis generated for causing the set of starboard propulsion units 550to generate different thrust from the thrust generated by the set of port propulsion units 550.

For example, when it is desired to provide a turning moment in yaw, in the port direction (with respect to the air vehicle 100) , during hover and while generating an aggregate forward thrust TT , the second command 4020Bcauses the starboard top propulsion unit 550STand the starboard bottom propulsion unit 550SBto each generate an increased thrust +AT(equal to one another) over the respective basic propulsion unit thrust TU . Thus, the total thrust TCgenerated by each one of the starboard top propulsion unit 550S T and the starboard bottom propulsion unit 550SBis determined as follows: TC= TU+ AT 029295874-06 Concurrently, the second command 4020Bcauses the port top propulsion unit 550P B and the port bottom propulsion unit 550PBto each generate a decreased thrust - AT(equal to one another) over the respective basic propulsion unit thrust TU . Thus, the total thrust TDgenerated by each one of port top propulsion unit 550PBand the port bottom propulsion unit 550PBis determined as follows: TD= TU- AT The differential thrust between the two starboard propulsion units 550and the two port propulsion units generates a yaw turning moment MYin the port direction, in view of the respective moment arms about the center of gravity CG , while the aggregate thrust TTremains unchanged, since the total thrust is: 2*TC+ 2*TD= 2* TU+ 2*AT+ 2* TU– 2*AT= 4*TU= TT The magnitude of the increase/decrease in thrust I AT I will depend on how fast the turning moment is desired to be.

A reverse turning moment in yaw can then be applied when the desired yaw angle has been attained in order to maintain the desired yaw angle. Such a reverse turning moment in yaw can be provided by generating an appropriate second command 4020Bin which the thrust is increased in the two port propulsion units, and concurrently decreased in the two starboard propulsion units.

It is to be noted that as a non-zero yaw angle is attained, and the roll axis rotates away from vertical to one side, the thrust vector of the aggregate forward thrust TTis also rotated away from vertical. Thus, to maintain hover, the aggregate forward thrust TTis caused to be increased (via the first command 4010 ) such that the vertical component of the aggregate forward thrust TTnominally equals the weight W . This maneuver will also result in the air vehicle moving in a transverse direction in view of the horizonal component of the aggregate forward thrust TT .

Providing a turning moment in yaw in the starboard direction (with respect to the air vehicle 100) , during hover and while generating an aggregate forward thrust TT , is essentially the reverse of providing a yaw moment in the port direction, and starts with the second command 4020Bcausing port top propulsion unit 550PBand the port bottom 029295874-06 propulsion unit 550PBto each generate an increased thrust +AT(equal to one another) over the respective basic propulsion unit thrust TU , and concurrently the second command 4020Bcausing the starboard top propulsion unit 550S T and the starboard bottom propulsion unit 550SBto each generate a decreased thrust -AT(equal to one another) over the respective basic propulsion unit thrust TU .

Providing a turning moment in yaw, in the port direction or in the starboard direction, during acceleration/climb, is similar to that as disclosed herein regarding hover, mutatis mutandis, the main difference being that the respective aggregate forward thrust TTis maintained greater than the weight Wof the air vehicle 100.

Providing a turning moment in in the port direction or in the starboard direction, during deceleration/descent, is similar to that as disclosed herein regarding hover, mutatis mutandis, the main difference being that the respective aggregate forward thrust TTis maintained less than the weight Wof the air vehicle 100.

Referring in particular to Fig. 18C and Fig. 19C, when it is desired to provide a turning moment in roll, a second command 4020Cis generated for causing one diagonally disposed set of propulsion units 550to generate different thrust from the thrust generated by the other set of diagonally disposed propulsion units 550.

For example, when it is desired to provide a turning moment in roll, in the counter clockwise direction (in the view seen in Fig. 2 with respect to the air vehicle 100) , during hover and while generating an aggregate forward thrust TT , the second command 4020C causes the starboard top propulsion unit 550S T and the port bottom propulsion unit 550P B to each generate an increased thrust +AT(equal to one another) over the respective basic propulsion unit thrust TU . Thus, the total thrust TEgenerated by each one of the starboard top propulsion unit 550S T and the port top propulsion unit 550P T is determined as follows: TE= TU+ AT Concurrently, the second command 4020Ccauses the starboard bottom propulsion unit 550S B and the port top propulsion unit 550P T to each generate a decreased thrust -AT(equal to one another) over the respective basic propulsion unit 029295874-06 thrust TU . Thus, the total thrust TFgenerated by each one of the starboard bottom propulsion unit 550S B and the port top propulsion unit 550P T is determined as follows: TF= TU- AT The differential thrust between the two groups of diagonally opposed propulsion units (the starboard top propulsion unit 550S T and the port bottom propulsion unit 550P B, versus, the starboard bottom propulsion unit 550S B and the port top propulsion unit 550P T) generates a counter-clockwise roll turning moment MP , in view of the respective moment arms about the center of gravity CG , while the aggregate thrust TTremains unchanged, since the total thrust is: 2*TE+ 2*TF= 2* TU+ 2*AT+ 2* TU– 2*AT= 4*TU= TT The magnitude of the increase/decrease in thrust I AT I will depend on how fast the turning moment is desired to be.

A reverse turning moment in roll can then be applied when the desired roll angle has been attained in order to maintain the desired roll angle. Such a reverse turning moment in roll can be provided by generating an appropriate second command 4020Cin which the thrust is increased in the starboard bottom propulsion unit 550S B and the port top propulsion unit 550P T, and concurrently decreased in the starboard top propulsion unit 550S T and the port bottom propulsion unit 550P B.

Providing a turning moment in roll in the clockwise direction (in the view seen in Fig. 2 with respect to the air vehicle 100) , during hover and while generating an aggregate forward thrust TT , is essentially the reverse of providing a nose-up pitch moment, and starts with the second command 4020 C causing the starboard bottom propulsion unit 550S B and the port top propulsion unit 550P T to each generate an increased thrust +AT (equal to one another) over the respective basic propulsion unit thrust TU , and concurrently the second command 4020 C causing the starboard top propulsion unit 550S T and the port bottom propulsion unit 550P B to each generate a decreased thrust - AT(equal to one another) over the respective basic propulsion unit thrust TU .

Providing a turning moment in roll, counter clockwise or clockwise, during acceleration/climb, is similar to that as disclosed herein regarding hover, mutatis 029295874-06 mutandis, the main difference being that the respective aggregate forward thrust TTis maintained greater than the weight Wof the air vehicle 100.

Providing a turning moment in roll, counter clockwise or clockwise, during deceleration/descent, is similar to that as disclosed herein regarding hover, mutatis mutandis, the main difference being that the respective aggregate forward thrust TTis maintained less than the weight Wof the air vehicle 100.

Aerodynamic Flight Mode In aerodynamic flight mode AFM , the wing system 300aerodynamically generates sufficient lift Lto maintain the air vehicle 100airborne, i.e., to balance the weight Wof the air vehicle 100during forward flight, to allow the air vehicle 100to accelerate and/or climb, or to decelerate and/or reduce altitude, while the propulsion system 500is concurrently not generating any vertical thrust, or generating very little vertical thrust. In aerodynamic flight mode AFM , the roll axis Ris generally horizontal, or angularly inclined to the horizontal by an angle of attack α such that the aerodynamic lift Lgenerated by the wing system 300 is still sufficient to maintain the air vehicle 100airborne without requiring assistance from any vertical component of the aggregate forward thrust TTgenerated by the propulsion system 500,and the wings are not stalled. That is, at such angles of attack α the aerodynamic lift Lgenerated by the wing system 300enables balancing the weight Wof the air vehicle 100during forward flight, or allows the air vehicle 100to accelerate and/or climb, or allows the air vehicle 100to decelerate and/or reduce altitude, while the propulsion system 500is concurrently not generating any significant vertical thrust. The aggregate forward thrust TT balances the drag Dgenerated by the air vehicle 100during straight and level flight at constant velocity. In addition, while in aerodynamic flight mode AFM , the air vehicle 100 is able to maneuver in one or more of pitch, roll or yaw, by suitably and differentially controlling the magnitude of the respective thrust Tgenerated by each of the propulsion units 550,as disclosed herein.

Thus, referring to Fig. 20A and Fig. 21A, in pure straight and level aerodynamic flight mode, and with the air vehicle 100maintaining a constant angle of attack α , in an example of a method according to this aspect of the presently disclosed subject matter a 029295874-06 respective first command 5010Ais generated and sent to the propulsion system 500such as to generate an aggregate forward thrust TThaving a magnitude nominally equal to the drag Dgenerated by the air vehicle 100.Concurrently, no control moments are to be generated, and thus, this example of the method excludes generating a respective second command 2020 .

Referring to Fig. 20B and Fig. 21B, in pure climb/acceleration aerodynamic flight mode, and with the air vehicle 100maintaining a constant angle of attack α , in an example of a method according to this aspect of the presently disclosed subject matter a respective first command 5010Bis generated and sent to the propulsion system 500such as to generate an aggregate forward thrust TThaving a magnitude greater than the drag D generated by the air vehicle 100.Concurrently, no control moments are to be generated, and thus, this example of the method excludes generating a respective second command 2020 .

Referring to Fig. 20C and Fig. 21C, in pure descent/deceleration aerodynamic flight mode, and with the air vehicle 100maintaining a constant angle of attack α , in an example of a method according to this aspect of the presently disclosed subject matter a respective first command 5010Cis generated and sent to the propulsion system 500such as to generate an aggregate forward thrust TThaving a magnitude less than the drag D generated by the air vehicle 100.Concurrently, no control moments are to be generated, and thus, this example of the method excludes generating a respective second command 2020 .

Referring to Fig. 22A, Fig. 22B, Fig. 22C, Fig. 23A, Fig. 23B and Fig. 23C, in straight and level aerodynamic flight mode, (at a particular angle of attack α ) including a change in the special attitude of the air vehicle 100,in examples of a method 6000A, 6000B, 6000Caccording to this aspect of the presently disclosed subject matter a respective first command 6010is generated and sent to the propulsion system 500such as to generate an aggregate forward thrust TThaving a magnitude nominally equal to the drag Dgenerated by the air vehicle 100.Thus, responsive to the first command 6010 , each propulsion unit 550generates a respective basic propulsion unit thrust TUthat is nominally a quarter of the aggregate forward thrust TT . i.e.: TU= 0.25* TT 029295874-06 Concurrently, and depending on what control moments are to be generated, this example of the method includes generating a respective second command and sending the second command to the propulsion units 550to execute the desired turning moment while still maintain the same level of aggregate forward thrust TT .

Referring in particular to Fig. 22A and Fig. 23A, when it is desired to provide a turning moment in pitch a second command 6020Ais generated for causing the set of top propulsion units to generate different thrust from the thrust generated by the set of bottom propulsion units.

For example, when it is desired to provide a turning moment in pitch, nose down (with respect to the air vehicle 100) , during straight and level aerodynamic flight mode, (at a particular angle of attack α ) and while generating an aggregate forward thrust TT , the second command 6020Acauses the starboard top propulsion unit 550S T and the port top propulsion unit 550P T to each generate an increased thrust +AT(equal to one another) over the respective basic propulsion unit thrust TU . Thus, the total thrust TAgenerated by each one of the starboard top propulsion unit 550S T and the port top propulsion unit 550P T is determined as follows: TA= TU+ AT Concurrently, the second command 2020causes the starboard bottom propulsion unit 550S B and the port bottom propulsion unit 550PBto each generate a decreased thrust -AT(equal to one another) over the respective basic propulsion unit thrust TU . Thus, the total thrust TBgenerated by each one of starboard bottom propulsion unit 550SBand the port bottom propulsion unit 550PBis determined as follows: TB= TU- AT The differential thrust between the two top propulsion units 550and the two bottom propulsion units generates a nose down pitch turning moment MP , in view of the respective moment arms about the center of gravity CG , while the aggregate thrust TT remains unchanged, since the total thrust is: 2*TA+ 2*TB= 2* TU+ 2*AT+ 2* TU– 2*AT= 4*TU= TT 029295874-06 The magnitude of the increase/decrease in thrust I AT I will depend on how fast the turning moment is desired to be.

A reverse turning moment in pitch can then be applied when the desired pitch angle has been attained in order to maintain the desired pitch angle. Such a reverse turning moment in pitch can be provided by generating an appropriate second command 6020A in which the thrust is increased in the two bottom propulsion units, and concurrently decreased in the two top propulsion units.

It is to be noted that as a non-zero pitch angle is attained, and the roll axis rotates away from the previous position (e.g., generally horizontal), the thrust vector of the aggregate forward thrust TTis also rotated away from horizontal, and the angle of attack αof the air vehicle 100also changes, which can change the lift Lgenerated by the wings.

Providing a turning moment in pitch, nose up (with respect to the air vehicle 100) , during straight and level aerodynamic flight mode, (at a particular angle of attack α ) and while generating an aggregate forward thrust TT , is essentially the reverse of providing a nose-up pitch moment, and starts with the second command 6020Acausing the starboard bottom propulsion unit 550SBand the port bottom propulsion unit 550PBto each generate an increased thrust +AT(equal to one another) over the respective basic propulsion unit thrust TU , and concurrently the second command 6020Acausing the starboard top propulsion unit 550STand the port top propulsion unit 550PTto each generate a decreased thrust -AT(equal to one another) over the respective basic propulsion unit thrust TU .

Providing a turning moment in pitch, nose up or nose down, during acceleration/climb, is similar to that as disclosed herein regarding straight and level aerodynamic flight mode, (at a particular angle of attack α ), mutatis mutandis, the main difference being that the respective aggregate forward thrust TTis maintained greater than the drag Dgenerated by the air vehicle 100.

Providing a turning moment in pitch, nose up or nose down, during deceleration/descent, is similar to that as disclosed herein regarding straight and level aerodynamic flight mode, (at a particular angle of attack α ), mutatis mutandis, the main 029295874-06 difference being that the respective aggregate forward thrust TTis maintained less than the drag Dgenerated by the air vehicle 100.

Referring in particular to Fig. 22B and Fig. 23B, when it is desired to provide a turning moment in yaw, a second command 6020Bis generated for causing the set of starboard propulsion units 550to generate different thrust from the thrust generated by the set of port propulsion units 550.

For example, when it is desired to provide a turning moment in yaw, in the port direction (with respect to the air vehicle 100) , during straight and level aerodynamic flight mode, (at a particular angle of attack α ) and while generating an aggregate forward thrust TT , the second command 6020Bcauses the starboard top propulsion unit 550S T and the starboard bottom propulsion unit 550SBto each generate an increased thrust +AT(equal to one another) over the respective basic propulsion unit thrust TU . Thus, the total thrust TCgenerated by each one of the starboard top propulsion unit 550STand the starboard bottom propulsion unit 550SBis determined as follows: TC= TU+ AT Concurrently, the second command 6020Bcauses the port top propulsion unit 550PBand the port bottom propulsion unit 550PBto each generate a decreased thrust - AT(equal to one another) over the respective basic propulsion unit thrust TU . Thus, the total thrust TDgenerated by each one of port top propulsion unit 550PBand the port bottom propulsion unit 550PBis determined as follows: TD= TU- AT The differential thrust between the two starboard propulsion units 550and the two port propulsion units generates a yaw turning moment MYin the port direction, in view of the respective moment arms about the center of gravity CG , while the aggregate thrust TTremains unchanged, since the total thrust is: 2*TC+ 2*TD= 2* TU+ 2*AT+ 2* TU– 2*AT= 4*TU= TT The magnitude of the increase/decrease in thrust I AT I will depend on how fast the turning moment is desired to be. 029295874-06 A reverse turning moment in yaw can then be applied when the desired yaw angle has been attained in order to maintain the desired yaw angle. Such a reverse turning moment in yaw can be provided by generating an appropriate second command 2020in which the thrust is increased in the two port propulsion units, and concurrently decreased in the two starboard propulsion units.

Providing a turning moment in yaw in the starboard direction (with respect to the air vehicle 100) , during straight and level aerodynamic flight mode, (at a particular angle of attack α ) and while generating an aggregate forward thrust TT , is essentially the reverse of providing a yaw moment in the port direction, and starts with the second command 6020Bcausing port top propulsion unit 550PBand the port bottom propulsion unit 550PB to each generate an increased thrust +AT(equal to one another) over the respective basic propulsion unit thrust TU , and concurrently the second command 6020Bcausing the starboard top propulsion unit 550STand the starboard bottom propulsion unit 550SBto each generate a decreased thrust -AT(equal to one another) over the respective basic propulsion unit thrust TU .

Providing a turning moment in yaw, in the port direction or in the starboard direction, during acceleration/climb, is similar to that as disclosed herein regarding straight and level aerodynamic flight mode, (at a particular angle of attack α ), mutatis mutandis, the main difference being that the respective aggregate forward thrust TTis maintained greater than the drag Dgenerated by the air vehicle 100.

Providing a turning moment in in the port direction or in the starboard direction, during deceleration/descent, is similar to that as disclosed herein regarding straight and level aerodynamic flight mode, (at a particular angle of attack α ), mutatis mutandis, the main difference being that the respective aggregate forward thrust TTis maintained less than the drag Dgenerated by the air vehicle 100.

Referring in particular to Fig. 22C and Fig. 23C, when it is desired to provide a turning moment in roll, a second command 6020Cis generated for causing one diagonally disposed set of propulsion units 550to generate different thrust from the thrust generated by the other set of diagonally disposed propulsion units 550. 029295874-06 For example, when it is desired to provide a turning moment in roll, in the counter clockwise direction (in the view seen in Fig. 2 with respect to the air vehicle 100) , during straight and level aerodynamic flight mode, (at a particular angle of attack α ) and while generating an aggregate forward thrust TT , the second command 6020Ccauses the starboard top propulsion unit 550STand the port bottom propulsion unit 550PBto each generate an increased thrust +AT(equal to one another) over the respective basic propulsion unit thrust TU . Thus, the total thrust TEgenerated by each one of the starboard top propulsion unit 550STand the port top propulsion unit 550PTis determined as follows: TE= TU+ AT Concurrently, the second command 6020Ccauses the starboard bottom propulsion unit 550SBand the port top propulsion unit 550PTto each generate a decreased thrust -AT(equal to one another) over the respective basic propulsion unit thrust TU . Thus, the total thrust TFgenerated by each one of the starboard bottom propulsion unit 550S B and the port top propulsion unit 550PTis determined as follows: TF= TU- AT The differential thrust between the two groups of diagonally opposed propulsion units (the starboard top propulsion unit 550STand the port bottom propulsion unit 550PB , versus, the starboard bottom propulsion unit 550SBand the port top propulsion unit 550PT ) generates a counter-clockwise roll turning moment MP , in view of the respective moment arms about the center of gravity CG , while the aggregate thrust TT remains unchanged, since the total thrust is: 2*TE+ 2*TF= 2* TU+ 2*AT+ 2* TU– 2*AT= 4*TU= TT The magnitude of the increase/decrease in thrust I AT I will depend on how fast the turning moment is desired to be.

A reverse turning moment in roll can then be applied when the desired roll angle has been attained in order to maintain the desired roll angle. Such a reverse turning moment in roll can be provided by generating an appropriate second command 6020Cin which the thrust is increased in the starboard bottom propulsion unit 550SBand the port 029295874-06 top propulsion unit 550PT , and concurrently decreased in the starboard top propulsion unit 550STand the port bottom propulsion unit 550PB .

Providing a turning moment in roll in the clockwise direction (in the view seen in Fig. 2 with respect to the air vehicle 100) , during straight and level aerodynamic flight mode, (at a particular angle of attack α ) and while generating an aggregate forward thrust TT , is essentially the reverse of providing a nose-up pitch moment, and starts with the second command 6020Ccausing the starboard bottom propulsion unit 550SBand the port top propulsion unit 550PTto each generate an increased thrust +AT(equal to one another) over the respective basic propulsion unit thrust TU , and concurrently the second command 6020Ccausing the starboard top propulsion unit 550STand the port bottom propulsion unit 550PBto each generate a decreased thrust -AT(equal to one another) over the respective basic propulsion unit thrust TU .

Providing a turning moment in roll, counter clockwise or clockwise, during acceleration/climb, is similar to that as disclosed herein regarding straight and level aerodynamic flight mode, (at a particular angle of attack α ), mutatis mutandis, the main difference being that the respective aggregate forward thrust TTis maintained greater than the drag Dgenerated by the air vehicle 100.

Providing a turning moment in roll, counter clockwise or clockwise, during deceleration/descent, is similar to that as disclosed herein regarding hover, mutatis mutandis, the main difference being that the respective aggregate forward thrust TTis maintained less than the drag Dgenerated by the air vehicle 100.

Transition Mode In transition mode TRM , the air vehicle 100transitions between the vectored thrust mode VTMand the aerodynamic flight mode AFM .

Depending on whether the air vehicle 100is currently in vectored thrust mode VTM or in aerodynamic flight mode AFM , during transition mode TRMthe air vehicle 100can transition from the vectored thrust mode VTMto the aerodynamic flight mode AFM , or from the aerodynamic flight mode AFMto the vectored thrust mode VTM , respectively. 029295874-06 According to an aspect of the present disclosed subject matter, in at least some examples the transition mode TRMis carried out from the vectored thrust mode VTMto the aerodynamic flight mode AFMwhile concurrently increasing the aggregate forward thrust TTgenerated by the propulsion system of the air vehicle, from a baseline thrust level TT0to any desired aggregate forward thrust level TTinot exceed a maximum aggregate forward thrust level TTmaxcapable of being generated by the propulsion system of the air vehicle.

The baseline thrust level TT0corresponds to the level of aggregate forward thrust TT required to maintain hover, i.e., equal to the weight Wof the air vehicle 500.

The maximum aggregate forward thrust level TTmaxcorresponds to the maximum level of aggregate forward thrust TTthat can be generated by the propulsion system 500.

Thus, the propulsion system is capable of provide an excess thrust ratio (with respect to weight W of the air vehicle 100 In at least one example of transition mode TRMthe air vehicle 100is operated such as to at least match the summation of lift Land/or the respective vertical component TTVof the aggregate thrust TTto the weight Wof the air vehicle 100during the transition. In at least some alternative variations of such examples, in which it is desired to concurrently reduce altitude with execution of the transition mode TRM , the summation of lift Land/or the respective vertical component TTVof the aggregate thrust TTcan be correspondingly less than the weight Wof the air vehicle 100.In at least some alternative variations of such examples, in which it is desired to concurrently increase altitude with execution of the transition mode TRM , the summation of lift Land/or the respective vertical component TTV of the aggregate thrust TTcan be correspondingly more than the weight Wof the air vehicle 100.

Thus, and referring to Fig. 28, in a first example of a method 7000Aaccording to this aspect of the presently disclosed subject matter the air vehicle 100is operated in transition mode TRMto transit from the vectored thrust mode VTMto the aerodynamic flight mode AFM , at a nominally constant desired altitude DALT, and the air vehicle 100is operated during transition mode TRMsuch as to nominally match the summation of lift L and the respective vertical component TTVof the aggregate thrust TTto the weight Wof the 029295874-06 air vehicle 100during the transition. Such matching can be 100% matching, in which the aggregate thrust TTnominally equals the weight Wof the air vehicle 100. / Alternatively, such matching can be within ±N% of 100% matching, for example N can be +20% corresponding to 80% matching for example, in which the aggregate thrust TTis less the weight Wof the air vehicle 100by a corresponding proportion, for example 20%; for example N can be -20% corresponding to 120% matching for example, in which the aggregate thrust TTis greater the weight Wof the air vehicle 100by a corresponding proportion, for example 20%.

For example, according to the method 7000 A, the air vehicle 100can commence flight by being held by a user or on a stand at a take-off site, with the roll axis Rin a general vertical orientation, in which the nose 210is facing in an upward direction.

Referring to Fig. 24A, prior to carrying out the transition mode TRM , the air vehicle 100is first operated in vectored thrust mode VTM , and the propulsion system 500is operated to provide sufficient aggregate forward thrust TTto enable the air vehicle 100to first hover at the take off site, and thus can be disengaged from the user or the stand. Then the aggregate forward thrust TTcan be increased to enable the air vehicle 100to climb to a desired altitude, for example as disclosed herein regarding vectored thrust mode VTM . At the desired altitude the propulsion units 550are operated to reduce the aggregate forward thrust TTto match the weight Wof the air vehicle 100,which can then hover in vectored thrust mode VTM . The air vehicle 100can then be operated in transition mode TRMto thereby transition to aerodynamic flight mode AFMat nominally constant altitude.

Thus, referring to Fig. 24B, and Fig. 25, in method 7000A , the air vehicle 100 transitions from the vectored thrust mode VTMto the aerodynamic flight mode AFM , while concurrently the altitude of the air vehicle 100is maintained nominally constant over time at least during such transition. According to this example of the method, just prior to transition, and when such matching is 100%, hover is maintained or alternatively another desired level of matching is maintained between the aggregate forward thrust TT and the weight Wof the air vehicle 100.A respective first command 7010Ais generated and sent to the propulsion system 500such as to generate an aggregate forward thrust TT (thus, initially, in a general vertical direction) having a magnitude nominally matches the weight Wof the air vehicle 100at the desired level of matching, and at the desired 029295874-06 altitude. For example the level of matching is 100%, and aggregate forward thrust TTis equal to the weight Wof the air vehicle 100.Thus, responsive to the first command 7010A , each propulsion unit 550generates a respective basic propulsion unit thrust TU that is nominally a quarter of the aggregate forward thrust TT . i.e.: TU= 0.25* TT Furthermore, the aggregate forward thrust TThas nominally zero horizontal component, and vertical component TTVis nominally equal to the aggregate forward thrust TT .

The next step of this example of the method 7000 A, and referring in particular to Fig. 24B and Fig. 25, a second command 7020 A is generated for causing the set of top propulsion units to generate greater thrust than the thrust generated by the set of bottom propulsion units 550,to thereby execute a desired nose-down turning moment in pitch while hovering. Concurrently, a modified first command 7010 A' is generated to cause the propulsion system 500to incrementally increase the aggregate forward thrust TTsuch as to maintain the same level of vertical component TTVof the aggregate forward thrust TT as in hover, and thus maintain altitude, when said matching is 100%.

The second command 7020 A causes the starboard top propulsion unit 550S T and the port top propulsion unit 550P T to each generate an increased thrust +AT(equal to one another) over the respective basic propulsion unit thrust TU . Concurrently, the second command 7020 A also causes the starboard bottom propulsion unit 550S B and the port bottom propulsion unit 550P B to each generate a decreased thrust -AT(equal to one another) over the respective basic propulsion unit thrust TU .

As the air vehicle 100begins to pitch in a nose-down direction to provide an increasing pitch angle 0 (with respect to a vertical axis), the thrust vector of the aggregate forward thrust TTcorrespondingly tilts away from vertical, and if the magnitude of the aggregate forward thrust TTis maintained, the resulting vertical component TTVof the aggregate forward thrust TTwould begin to decrease while the horizontal component TTH of the aggregate forward thrust TTwould begin to increase. Such a decrease in the magnitude of vertical component TTVof the aggregate forward thrust TTwould result in 029295874-06 a loss of altitude since the weight Wis no longer balanced by the vertical component TTV of the aggregate forward thrust TT .

Thus, correspondingly, the modified first command 7010 A' compensates for the effect of the pitch angle 0 on the vertical component TTV , by causing the aggregate forward thrust TTgenerated by the propulsion units 550to be correspondingly increased to compensate for the inclination of the thrust vector from the vertical due to the increasing pitching angle 0.

Thus, concurrently, and as the air vehicle 100pitches nose down by an increasing pitch angle 0, the aggregate forward thrust TTincreases to maintain the vertical component TTVof the aggregate forward thrust TTconstant and equal to the weight Wof the air vehicle 100,such that: TTV= TT* cos0= W Thus, the modified first command 7010 A' is directed to causing each propulsion unit 550to generate a respective unit thrust TU , determined as follows: TU= 0.25* TT* cos0 The method 7000 A thus also includes determining the pitch angle 0 . For this purpose, the air vehicle 100can include an attitude sensor, for example as is known in the art, for example, that is operatively coupled to the controller 260thereby providing direct input data on pitch angle.

Concurrently, an increasing corresponding horizontal component TTHof the increasing aggregate forward thrust TT(concurrent with increasing pitch angle 0 ) provides an increasing horizonal forward velocity to the air vehicle 100.

This step, including generating a modified first command 7010A'and concurrently generating second command 7020Ain this manner, is continued so long as the pitch angle 0 from vertical is still not sufficient to provide an angle of attack α for the air vehicle 100and/or a sufficient forward horizontal velocity for the air vehicle 100,such as to thereby enable the wing system 300to generate any significant lift L . For example, at low values of pitch angle 0 from vertical, the corresponding angles of attack α can be 029295874-06 too high to enable significant aerodynamic lift to be generated, and/or, the forward velocity can be too low to enable significant aerodynamic lift to be generated.

Thus, during this step, the total thrust TAgenerated by each one of the starboard top propulsion unit 550STand the port top propulsion unit 550PTis determined as follows: TA= 0.25* TT* cose+ AT Concurrently, the total thrust TBgenerated by each one of starboard bottom propulsion unit 550SBand the port bottom propulsion unit 550PBis determined as follows: TB= 0.25* TT* cose- AT Thus, the differential thrust between the two top propulsion units 550and the two bottom propulsion units generates a nose down pitch turning moment MP , in view of the respective moment arms about the center of gravity CG , while the aggregate thrust TT progressively increases as the pitch angle e increases, to maintain the vertical component TTVnominally constant and matching the weight W .

In the next step, as the pitch angle e continues to increase, the angle of attack α of the air vehicle 100and concurrently the horizontal velocity of the air vehicle 100also continue to increase, thereby enabling aerodynamic lift Lto be generated by the wing system 300.

Once aerodynamic lift Lbegins to be generated, a further modified first command 7010 A" is generated to cause the propulsion system 500to reduce the level of vertical component TTVof the aggregate forward thrust TT , such that the summation of the vertical component TTVof the aggregate forward thrust TTand the aerodynamic lift L , at each corresponding pitch angle e , remains constant and balances the weight W , and thus maintain altitude. For example, the air vehicle 100can include suitable accelerometers, for example as is known in the art, operatively connected to the controller 260that operate to provide indications to the controller 260whether the air vehicle 100is beginning to descend (in which case the vertical component TTVof the aggregate forward thrust TTis 029295874-06 increased) or ascend (in which case the vertical component TTVof the aggregate forward thrust TTis decreased).

Thus, as angle of attack α and horizontal velocity increase for the air vehicle 100, resulting in an increasing level of aerodynamic lift L , the further modified first command 7010 A" causes the propulsion units 550to provide a correspondingly decreasing level of aggregate forward thrust TT .

Concurrently, the further modified first command 7010 A" is maintained at a level such that the the horizontal component TTHof the aggregate forward thrust TTprovides the desired velocity and/or acceleration in the horizontal direction.

The method 7000Afurther includes the step of terminating the second command 7020when a desired pitch angle 0 has been reached. For example, such a pitch angle can correspond to providing an angle of attack α for the air vehicle sufficient to enable the air vehicle to generate sufficient lift Lsuch as to at least balance the weight W . for example, such a pitch angle 0 can be about 90º, and the air vehicle roll axis Ris nominally horizontal, and the corresponding angle of attack α for the air vehicle can be zero.

At this stage the air vehicle 100is capable of generating sufficient aerodynamic lift L , sufficient to balance the weight W , and thus the air vehicle 100can operate in aerodynamic flight mode AFM .

Transition from aerodynamic flight mode AFMto the vectored thrust mode VTM essentially corresponds to the reverse of the vectored thrust mode VTMto the aerodynamic flight mode AFM .

Referring to Figs. 26A to 26E, Fig. 27 and Fig. 29, in a second example of a method 7000Baccording to this aspect of the presently disclosed subject matter the air vehicle 100 is operated in transition mode TRMto transit from the vectored thrust mode VTMto the aerodynamic flight mode AFM , at nominally constant altitude, and the air vehicle 100is operated during transition mode TRMsuch as to utilize its inertia and/or gravitational deceleration or acceleration to effectively support the weight Wof the air vehicle 100during the transition. In other words, the air vehicle inertia and/or gravitational deceleration essentially prevent the air vehicle from losing height or descending below a predetermined altitude PALTduring transition. 029295874-06 For example, according to the method 7000B , the air vehicle 100can commence flight by being held by a user or on a stand at a take-off site, with the roll axis Rin a general vertical orientation, in which the nose 210is facing in an upward direction.

Referring to Fig. 26A, prior to carrying out the transition mode TRM , the air vehicle 100is first operated in vectored thrust mode VTM , and the propulsion system 500is operated to provide sufficient aggregate forward thrust TTto enable the air vehicle 100to first hover at the take off site, and thus can be disengaged from the user or the stand. Then the aggregate forward thrust TTcan be increased quickly to a maximum thrust TM , greater than the weight W , to enable the air vehicle 100to accelerate and climb quickly towards a desired altitude DALT , for example as disclosed herein regarding vectored thrust mode VTM . The hovering step can optionally be omitted, in which case the air vehicle 100 accelerates rapidly and climbs as soon as disengaged from the user or the stand.

As the desired altitude DALTis approached, for example at a predetermined altitude PALTwhich is at a predetermined vertical spacing VSbelow the desired altitude DALT , the propulsion units 550are operated to quickly reduce the aggregate forward thrust TTto match the weight Wof the air vehicle 100,and allow the air vehicle to decelerate under gravity within this vertical spacing VS . During such deceleration, the inertia of the air vehicle 100allows the air vehicle 100to continue climbing to the desired altitude DALT while decelerating.

During this deceleration, the air vehicle 100can then be operated in transition mode TRMto thereby transition to aerodynamic flight mode AFMat nominally constant altitude, which can be defined as being a range of altitude corresponding to or falling within this vertical spacing VS .

Thus, referring to Fig. 26B, and Fig. 27, in method 7000B , the air vehicle 100 transitions from the vectored thrust mode VTMto the aerodynamic flight mode AFM , while concurrently the altitude of the air vehicle 100is maintained within the vertical spacing VSat least during such transition. According to this example of the method, during transition the upwards inertia of the air vehicle is sufficient to at least balance the weight Wof the air vehicle 100,such as to prevent the air vehicle from losing height below the predetermined altitude PALT, regardless of the attitude of the air vehicle 100 in pitch.029295874-06 Thus, responsive to a first command 7010B , each propulsion unit 550generates a respective basic propulsion unit thrust TUthat is nominally a quarter of the aggregate forward thrust TT . i.e.: TU= 0.25* TT Furthermore, the aggregate forward thrust TThas nominally zero horizontal component, and the aggregate forward thrust TT , and the aggregate forward thrust TT corresponds to maximum thrust TMwhich is sufficient to provide the air vehicle with fast acceleration rate. For example, the aggregate forward thrust TTcan be the maximum thrust that can be generated by the propulsion system 500.

At the predetermined altitude PALT , a modified first command 7010B'is generated in which each propulsion unit 550generates a respective basic propulsion unit thrust TUthat is nominally a quarter of the aggregate forward thrust TT , and in which the aggregate forward thrust TTis reduced to equal the weight Wof the air vehicle 100(or to any other desired level of matching).

At this point, and with reduced vertical thrust the air vehicle begins to decelerate in a predictable manner towards the desired altitude DALT .

During this deceleration, and responsive to a second command 7020B , the propulsion system 500further generates a turning moment in pitch, nose down, to transit the orientation of the air vehicle 100from vertical to horizontal.

Thus, in this next step of this example of the method 7000 B, and referring in particular to Fig. 26C and Fig. 27, a second command 7020Bis generated for causing the set of top propulsion units to generate greater thrust than the thrust generated by the set of bottom propulsion units 550,to thereby execute a desired nose-down turning moment in pitch while hovering.

The second command 7020Bcauses the starboard top propulsion unit 550STand the port top propulsion unit 550PTto each generate an increased thrust +AT(equal to one another) over the respective basic propulsion unit thrust TU . Concurrently, the second command 7020Balso causes the starboard bottom propulsion unit 550SBand the port 029295874-06 bottom propulsion unit 550PBto each generate a decreased thrust -AT(equal to one another) over the respective basic propulsion unit thrust TU .

The level of increased thrust +ATand of decreased thrust -ATis maximized such that the air vehicle can complete the pitch maneuver while the air vehicle is still within the vertical spacing VS .

As the air vehicle 100begins to pitch in a nose-down direction to provide an increasing pitch angle 0 , the thrust vector of the aggregate forward thrust TT correspondingly tilts away from vertical, and if the magnitude of the aggregate forward thrust TTis maintained, the resulting vertical component TTVof the aggregate forward thrust TTwould begin to decrease while the horizontal component TTHof the aggregate forward thrust TTwould begin to increase. Such a decrease in the magnitude of vertical component TTVof the aggregate forward thrust TTwould eventually result in a loss of altitude since the weight Wis no longer balanced by the vertical component TTVof the aggregate forward thrust TT .

However, in this method, the upward momentum of the air vehicle maintains the air vehicle within the vertical spacing VSduring the turning maneuver.

Concurrently, and as the air vehicle 100pitches nose down by an increasing pitch angle 0 , the angle of attack α of the air vehicle 100and concurrently the horizontal velocity of the air vehicle 100also continue to increase, thereby enabling aerodynamic lift Lto be generated by the wing system 300 .

As the air vehicle pitches down and once aerodynamic lift Lbegins to be generated, a further modified first command 7010B"is generated to cause the propulsion system 500to generate forward thrust such that the the horizontal component TTHof the aggregate forward thrust TTprovides the desired velocity and/or acceleration in the horizontal direction.

The method 7000Bfurther includes the step of terminating the second command 7020Bwhen a desired pitch angle 0 has been reached. For example, such a pitch angle can correspond to providing an angle of attack α for the air vehicle sufficient to enable the air vehicle to generate sufficient lift Lsuch as to at least balance the weight W . for 029295874-06 example, such a pitch angle 0 can be about 90º, and the air vehicle roll axis Ris nominally horizontal, and the corresponding angle of attack α for the air vehicle can be zero.

At this stage the air vehicle 100is capable of generating sufficient aerodynamic lift L , sufficient to balance the weight W,and thus the air vehicle 100 can operate in aerodynamic flight mode AFM .

In an alternative variation of the example of Figs. 26A to 26E and to Fig. 27, rather than commencing the transition mode when reaching the predetermined altitude, the air vehicle can be allowed to reach the apogee and as the air vehicle then begins to accelerate downwardly under gravity, and within the vertical space VS , the transition mode is implemented.

According to another aspect of the presently disclosed subject matter there is provided a method for landing an air vehicle, wherein the air vehicle comprises a fuselage, a fixed wing arrangement and a propulsion system including a plurality of propulsion units each mounted to the wing system in fixed spatial relationship to the wing system with respect to the roll axis, wherein the air vehicle is configured for operating in vectored thrust flight mode, aerodynamic flight mode, and transition mode, and wherein the air vehicle comprises a fuselage portion aft of the wing arrangement. For example, such an air vehicle can be the air vehicle 100disclosed herein with reference to Fig. 1. Such a method can include the following steps: (a) causing the air vehicle to operate in vectored thrust mode to reach an altitude corresponding to a height of an extended arm of a human operator and at a range proximal to the human operator;(b) causing the air vehicle to hover at said altitude;(c) allowing the air vehicle to be grasped at said fuselage portion by the arm of the human operator.

Thus, in step (a) and step (b), the air vehicle is operated in vectored thrust mode to hover in close proximity to the human operator, so that the fuselage portion is reachable 029295874-06 by the arm of the human operator. Thereafter, in step (c), the air vehicle can be grasped at the fuselage portion by the hand of the operator, which effectively corresponds to landing the air vehicle.

Thereafter, the thrust generated by propulsion system is reduced to zero, and the weight of the air vehicle is supported by the operator. The air vehicle can then be shut down operationally, and can be lowered onto the ground or any suitable surface.

In the method claims that follow, alphanumeric characters and Roman numerals used to designate claim steps are provided for convenience only and do not imply any particular order of performing the steps.

Finally, it should be noted that the word "comprising" as used throughout the appended claims is to be interpreted to mean "including but not limited to".

While there has been shown and disclosed examples in accordance with the presently disclosed subject matter, it will be appreciated that many changes may be made therein without departing from the scope of the presently disclosed subject matter as set out in the claims. 029295874-06

Claims

- 71 - CLAIMS:

1. An air vehicle comprising:a fuselage defining a roll axis of the air vehicle;a fixed wing arrangement in fixed spatial disposition with respect to the fuselage;a propulsion system comprising at least four propulsion units, each one of said at least four propulsion units being mounted with respect to the wing system in lateral spaced relationship with respect to the roll axis, and wherein adjacent propulsion units are spaced circumferentially from one another about the roll axis;each said propulsion unit configured for generating a respective thrust along a respective thrust vector axis;wherein each respective thrust vector axis being in fixed inclined spatial orientation with respect to the roll axis such that the respective thrust has a nonzero thrust component defined on a plane orthogonal to the roll axis; and wherein the respective non-zero thrust component has a respective non-zero moment arm with respect to the roll axis such as to provide a respective roll moment about the roll axis.

2. The air vehicle according to claim 1, wherein respective said non-zero thrustcomponent of each pair of circumferentially adjacent said propulsion units are in mutually opposed rotational directions about the roll axis.

3. The air vehicle according to any one of claims 1 to 2, wherein respective said nonzero thrust component of each pair of diametrically opposed said propulsion units with respect to the roll axis are in the same rotational direction about the roll axis.

4. The air vehicle according to any one of claims 1 to 3, wherein respective said nonzero thrust component of one pair of diametrically opposed said propulsion units with respect to the roll axis are in a first rotational direction about the roll axis, and wherein respective said non-zero thrust component of another pair of diametrically opposed said propulsion units with respect to the roll axis are in a second rotational direction about the roll axis, wherein said first rotational direction is an opposite rotational direction with respect to the second rotational direction. 029295874-06 - 72 -

5. The air vehicle according to any one of claims 1 to 4, wherein the thrust vectorsof the propulsion units are non-parallel with respect to one another.

6. The air vehicle according to any one of claims 1 to 5, wherein said propulsion systemincludes a port pair and a starboard pair of said propulsion units, and wherein for each one of said port pair and said starboard pair, the respective thrust vectors are converging in a forward direction towards a forward converging point when the air vehicle is viewed in side view.

7. The air vehicle according to claim 6, wherein said propulsion system includes a toppair and a bottom pair of said propulsion units, and wherein for each one of said top pair and said bottom pair, the respective thrust vectors are diverging in a forward direction away from an aft diverging point when the air vehicle is viewed in top view.

8. The air vehicle according to any one of claims 1 to 5, wherein said propulsion systemincludes a top pair and a bottom pair of said propulsion units, and wherein for each one of said top pair and said bottom pair, the respective thrust vectors are converging in a forward direction towards a forward converging point when the air vehicle is viewed in top view.

9. The air vehicle according to claim 6, wherein said propulsion system includes a portpair and a starboard pair of said propulsion units, and wherein for each one of said port pair and said starboard pair, the respective thrust vectors are diverging in a forward direction away from an aft diverging point when the air vehicle is viewed in side view.

10. The air vehicle according to any one of claims 1 to 9, wherein for each propulsion unit, for a given magnitude of respective thrust along the respective thrust vector, the respective moment arm from the non-zero thrust component to the roll axis is maximized.

11. The air vehicle according to any one of claims 1 to 10, wherein each propulsion unit has a rotor axis.

12. The air vehicle according to claim 11, wherein the rotor axes of the propulsion units are non-parallel with respect to one another.

13. The air vehicle according to any one of claims 11 to 12, wherein for each said propulsion unit, the respective rotor axis is co-axial with the respective thrust vector. 029295874-06 - 73 -

14. The air vehicle according to any one of claims 11 to 13, wherein said propulsion system includes a port pair and a starboard pair of said propulsion units, and wherein for each one of said port pair and said starboard pair, the respective rotor axes are converging in a forward direction towards a forward converging point when the air vehicle is viewed in side view.

15. The air vehicle according to claim 14, wherein said propulsion system includes a top pair and a bottom pair of said propulsion units, and wherein for each one of said top pair and said bottom pair, the respective rotor axes are diverging in a forward direction away from an aft diverging point when the air vehicle is viewed in top view.

16. The air vehicle according to any one of claims 11 to 13, wherein said propulsion system includes a top pair and a bottom pair of said propulsion units, and wherein for each one of said top pair and said bottom pair, the respective rotor axes are converging in a forward direction towards a forward converging point when the air vehicle is viewed in top view.

17. The air vehicle according to claim 16, wherein said propulsion system includes a port pair and a starboard pair of said propulsion units, and wherein for each one of said port pair and said starboard pair, the respective rotor axes are diverging in a forward direction away from an aft diverging point when the air vehicle is viewed in side view.

18. The air vehicle according to any one of claims 1 to 17, wherein said propulsion system includes a first pair of diametrically opposed said propulsion units with respect to the roll axis, and a second pair of diametrically opposed said propulsion units with respect to the roll axis, wherein said propulsion units of the first pair are each configured to provide a roll control moment in a counter-clockwise direction, and wherein said propulsion units of the second pair are each configured to provide a roll control moment in a clockwise direction.

19. The air vehicle according to any one of claims 1 to 18, wherein a starboard top said propulsion unit and a port bottom said propulsion unit are each configured to provide a roll control moment in a counter-clockwise direction, and wherein a starboard bottom said propulsion unit and a port top said propulsion unit are each configured to provide a roll control moment in a clockwise direction. 029295874-06 - 74 -

20. The air vehicle according to any one of claims 1 to 18, wherein a starboard top said propulsion unit and a port bottom said propulsion unit are each configured to provide a roll control moment in a clockwise direction, and wherein a starboard bottom said propulsion unit and a port top said propulsion unit are each configured to provide a roll control moment in a counter-clockwise direction.

21. The air vehicle according to any one of claims 1 to 20, wherein said wing system comprises a plurality of wings laterally projecting from the fuselage.

22. The air vehicle according to claim 21, wherein said wing system comprises four wings in X-arrangement.

23. The wing system according to any one of claims 21 to 22, wherein the wings are devoid of control surfaces for providing aerodynamically generated control moments in one or more of pitch roll and yaw.

24. The wing system according to any one of claims 21 to 23, comprising an empennage axially spaced by an axial spacing with respect to said wings.

25. The wing system according to claim 24, wherein said axial spacing is at least the size of a width of a human hand.

26. The wing system according to any one of claims 1 to 25, wherein at least part of the fuselage has a diameter is such as to enable circumferentially to grasp the air vehicle via a human hand.

27. The wing system according to claim 26, wherein said human hand is of a 50th percentile male.

28. An air vehicle comprising:a fuselage defining a roll axis of the air vehicle;four wings in X-arrangement with respect to the fuselage;four propulsion units, one propulsion unit being mounted with respect to each said wing in lateral spaced relationship with respect to the roll axis;each said propulsion unit configured for generating a respective thrust along a respective thrust vector axis;wherein each respective thrust vector axis being in fixed inclined spatial orientation with respect to the roll axis such that the respective thrust has a nonzero thrust component defined on a plane orthogonal to the roll axis; and wherein the respective non-zero thrust component has a respective non-zero 029295874-06 - 75 - moment arm with respect to the roll axis such as to provide a respective roll moment about the roll axis.

29. A control system to control operation of an air vehicle, wherein the air vehicle comprises a fuselage defining a roll axis, a fixed wing arrangement and a propulsion system including a plurality of propulsion units each mounted to the wing system in fixed spatial relationship to the wing system with respect to the roll axis, the control system comprising a processing unit and associated memory configured to generate one or more commands comprising:at least one first command operable to control an aggregate thrust generated by the propulsion system for enabling the air vehicle to operate in vectored thrust flight mode, aerodynamic flight mode, and transition mode,at least one second command operable to separately control individual thrusts of the individual propulsion units to provide control moments in at least roll during each one of said vectored thrust flight mode, aerodynamic flight mode, and transition mode.

30. An air vehicle comprising a fuselage defining a roll axis, a fixed wing arrangement and a propulsion system including a plurality of propulsion units each mounted to the wing system in fixed spatial relationship to the wing system with respect to the roll axis, and the control system as defined in claim 29.

31. A method of controlling an air vehicle, wherein the air vehicle comprises a fuselage defining a roll axis, a fixed wing arrangement and a propulsion system including a plurality of propulsion units each mounted to the wing system in fixed spatial relationship to the wing system with respect to the roll axis, the method comprising, by a processing unit and associated memory operatively coupled to the air vehicle:generating at least one first command operable to control an aggregate thrust generated by the propulsion system for enabling the air vehicle to operate in vectored thrust flight mode, aerodynamic flight mode, and transition mode,generating at least one second command operable to separately control individual thrusts of the individual propulsion units to provide control moments in at 029295874-06 - 76 - least roll during each one of said vectored thrust flight mode, aerodynamic flight mode, and transition mode.

32. A non-transitory storage device readable by a machine, tangibly embodying a program of instructions executable by the machine to perform operations of controlling operation of an air vehicle, wherein the air vehicle comprises a fuselage defining a roll axis, a fixed wing arrangement and a propulsion system including a plurality of propulsion units each mounted to the wing system in fixed spatial relationship to the wing system with respect to the roll axis, the operations comprising, by the machine:generating at least one first command operable to control an aggregate thrust generated by the propulsion system for enabling the air vehicle to operate in vectored thrust flight mode, aerodynamic flight mode, and transition mode,generating at least one second command operable to separately control individual thrusts of the individual propulsion units to provide control moments in at least roll during each one of said vectored thrust flight mode, aerodynamic flight mode, and transition mode.

33. A control system to control operation of an air vehicle, wherein the air vehicle comprises a fuselage, a fixed wing arrangement and a propulsion system including a plurality of propulsion units each mounted to the wing system in fixed spatial relationship to the wing system with respect to the roll axis, the control system comprising a processing unit and associated memory configured to generate one or more commands comprising:at least one first command operable to control an aggregate thrust generated by the propulsion system for enabling the air vehicle to operate in vectored thrust flight mode, aerodynamic flight mode, and transition mode,at least one second command operable to separately control individual thrusts of the individual propulsion units to provide control moments in at least pitch during transition mode from vectored thrust flight mode to aerodynamic flight mode;at least one modified first command operable to increase said aggregate thrust generated by the propulsion system to cause a vertical component of said aggregate thrust to match a weight of the air vehicle at a desired level of matching. 029295874-06 - 77 -

34. The control system according to claim 33, wherein said one or more commands further comprises: at least one further modified first command operable to reduce said aggregate thrust generated by the propulsion system to cause summation of the vertical component of said aggregate thrust and an aerodynamic lift generated by the wings to match a weight of the air vehicle at said desired level of matching.

35. The control system according to any one of claims 33 to 34, wherein said level of matching is one of the following: - 100%, wherein the air vehicle is correspondingly maintained at nominallyconstant altitude during the transition mode;- greater than 100%, wherein the air vehicle is correspondingly caused to climb altitude during the transition mode;- less than 100%, wherein the air vehicle is correspondingly caused to decrease altitude during the transition mode.

36. An air vehicle comprising a fuselage defining a roll axis, a fixed wing arrangement and a propulsion system including a plurality of propulsion units each mounted to the wing system in fixed spatial relationship to the wing system with respect to the roll axis, and the control system as defined in any one of claims 33 to 35.

37. A method of controlling operation of an air vehicle, wherein the air vehicle comprises a fuselage, a fixed wing arrangement and a propulsion system including a plurality of propulsion units each mounted to the wing system in fixed spatial relationship to the wing system with respect to the roll axis, the method comprising, by a processing unit and associated memory operatively coupled to the air vehicle:generating at least one first command operable to control an aggregate thrust generated by the propulsion system for enabling the air vehicle to operate in vectored thrust flight mode, aerodynamic flight mode, and transition mode,generating at least one second command operable to separately control individual thrusts of the individual propulsion units to provide control moments in at least pitch during transition mode from vectored thrust flight mode to aerodynamic flight mode;029295874-06 - 78 - generating at least one modified first command operable to increase said aggregate thrust generated by the propulsion system to cause a vertical component of said aggregate thrust to match a weight of the air vehicle at a desired level of matching.

38. The method according to claim 38, further comprising: generating at least one further modified first command operable to reduce said aggregate thrust generated by the propulsion system to cause summation of the vertical component of said aggregate thrust and an aerodynamic lift generated by the wings to match a weight of the air vehicle at said desired level of matching.

39. The method according to any one of claims 37 to 38, wherein said level of matching is one of the following: - 100%, wherein the air vehicle is correspondingly maintained at nominallyconstant altitude during the transition mode;- greater than 100%, wherein the air vehicle is correspondingly caused to climb altitude during the transition mode;- less than 100%, wherein the air vehicle is correspondingly caused to decrease altitude during the transition mode.

40. A non-transitory storage device readable by a machine, tangibly embodying a program of instructions executable by the machine to perform operations of controlling operation of an air vehicle, wherein the air vehicle comprises a fuselage, a fixed wing arrangement and a propulsion system including a plurality of propulsion units each mounted to the wing system in fixed spatial relationship to the wing system with respect to the roll axis, the operations comprising, by the machine:generating at least one first command operable to control an aggregate thrust generated by the propulsion system for enabling the air vehicle to operate in vectored thrust flight mode, aerodynamic flight mode, and transition mode,generating at least one second command operable to separately control individual thrusts of the individual propulsion units to provide control moments in at least pitch during transition mode from vectored thrust flight mode to aerodynamic flight mode;029295874-06 - 79 - generating at least one modified first command operable to increase said aggregate thrust generated by the propulsion system to cause a vertical component of said aggregate thrust to match a weight of the air vehicle at a desired level of matching.

41. A control system to control operation of an air vehicle, wherein the air vehicle comprises a fuselage, a fixed wing arrangement and a propulsion system including a plurality of propulsion units each mounted to the wing system in fixed spatial relationship to the wing system with respect to the roll axis, the control system comprising a processing unit and associated memory configured to generate one or more commands comprising:at least one first command operable to control an aggregate thrust generated by the propulsion system much higher than a weight of the air vehicle for enabling rapid vertical acceleration of the air vehicle while operating in vectored thrust flight mode,at least one modified first command operable to decrease said aggregate thrust generated by the propulsion system to cause a vertical component of said aggregate thrust to match a weight of the air vehicle at a desired level of matching,at least one second command operable to separately control individual thrusts of the individual propulsion units to provide control moments in at least pitch during transition mode from vectored thrust flight mode to aerodynamic flight mode.

42. The control system according to claim 41, wherein said one or more commands further comprises: at least one further modified first command operable to reduce said aggregate thrust generated by the propulsion system to cause summation of the vertical component of said aggregate thrust and an aerodynamic lift generated by the wings to match a weight of the air vehicle at said desired level of matching.

43. The control system according to any one of claims 41 to 42, wherein said level of matching is one of the following: - 100%, wherein the air vehicle is correspondingly maintained at nominallyconstant altitude during the transition mode; 029295874-06 - 80 - - greater than 100%, wherein the air vehicle is correspondingly caused to climb altitude during the transition mode;- less than 100%, wherein the air vehicle is correspondingly caused to decrease altitude during the transition mode.

44. An air vehicle comprising a fuselage defining a roll axis, a fixed wing arrangement and a propulsion system including a plurality of propulsion units each mounted to the wing system in fixed spatial relationship to the wing system with respect to the roll axis, and the control system as defined in any one of claims 41 to 43.

45. A method of controlling operation of an air vehicle, wherein the air vehicle comprises a fuselage, a fixed wing arrangement and a propulsion system including a plurality of propulsion units each mounted to the wing system in fixed spatial relationship to the wing system with respect to the roll axis, the method comprising, by a processing unit and associated memory operatively coupled to the air vehicle:generating at least one first command operable to control an aggregate thrust generated by the propulsion system much higher than a weight of the air vehicle for enabling rapid vertical acceleration of the air vehicle while operating in vectored thrust flight mode,generating at least one modified first command operable to decrease said aggregate thrust generated by the propulsion system to cause a vertical component of said aggregate thrust to match a weight of the air vehicle at a desired level of matching,generating at least one second command operable to separately control individual thrusts of the individual propulsion units to provide control moments in at least pitch during transition mode from vectored thrust flight mode to aerodynamic flight mode.

46. The method according to claim 45, wherein said one or more commands further comprises: generating at least one further modified first command operable to reduce said aggregate thrust generated by the propulsion system to cause summation of the vertical component 029295874-06 - 81 - of said aggregate thrust and an aerodynamic lift generated by the wings to match a weight of the air vehicle at said desired level of matching.

47. The method according to any one of claims 45 to 46, wherein said level of matching is one of the following:- 100%, wherein the air vehicle is correspondingly maintained at nominallyconstant altitude during the transition mode;- greater than 100%, wherein the air vehicle is correspondingly caused to climb altitude during the transition mode;- less than 100%, wherein the air vehicle is correspondingly caused to decrease altitude during the transition mode.

48. A non-transitory storage device readable by a machine, tangibly embodying a program of instructions executable by the machine to perform operations of controlling operation of an air vehicle, wherein the air vehicle comprises a fuselage, a fixed wing arrangement and a propulsion system including a plurality of propulsion units each mounted to the wing system in fixed spatial relationship to the wing system with respect to the roll axis, the operations comprising, by the machine: generating at least one first command operable to control an aggregate thrust generated by the propulsion system much higher than a weight of the air vehicle for enabling rapid vertical acceleration of the air vehicle while operating in vectored thrust flight mode,generating at least one modified first command operable to decrease said aggregate thrust generated by the propulsion system to cause a vertical component of said aggregate thrust to match a weight of the air vehicle at a desired level of matching,generating at least one second command operable to separately control individual thrusts of the individual propulsion units to provide control moments in at least pitch during transition mode from vectored thrust flight mode to aerodynamic flight mode.

49. Method for landing an air vehicle, wherein the air vehicle comprises a fuselage, a fixed wing arrangement and a propulsion system including a plurality of propulsion units 029295874-06 - 82 - each mounted to the wing system in fixed spatial relationship to the wing system with respect to the roll axis, wherein the air vehicle is configured for operating in vectored thrust flight mode, aerodynamic flight mode, and transition mode, and wherein the air vehicle comprises a fuselage portion aft of the wing arrangement, the method comprising:(a) causing the air vehicle to operate in vectored thrust mode to reach an altitude corresponding to a height of an extended arm of a human operator and at a range proximal to the human operator;(b) causing the air vehicle to hover at said altitude;(c) allowing the air vehicle to be grasped at said fuselage portion by the arm of the human operator.

50. The method according to claim 49, further comprising the step: (d) reducing a thrust generated by propulsion system to zero. For the Applicants, REINHOLD COHN AND PARTNERS By: 029295874-06