FIELD OF THE INVENTION

The presently disclosed subject matter relates to the field of unmanned vehicles. BACKGROUND OF THE INVENTION

Unmanned vehicles (abbreviated herein "UVs") are becoming today increasingly popular in various applications, including for example traffic monitoring, remote sensing and reconnaissance, search and rescue, domestic policing, electronic warfare, and more.

GENERAL DESCRIPTION According to one aspect of the presently disclosed subject matter there is provided an in-flight UAV retrieval system mountable on an aircraft and configured to execute a UAV retrieval process for retrieving one or more in-flight UAVs into the aircraft, the system comprising: a computer device operatively connected to a retrieval device comprising a retriever head, the retrieval head comprising an engagement mechanism configured to connect to an in-flight UAV; the retrieval device is responsive to instructions provided by the computer device to extend the retrieval head outside the aircraft towards an engagement location where a UAV is expected to be located; the retriever head is configured to engage with the UAV at the engagement location; responsive to successful engagement between the retriever head and the UAV, the retrieval device is configured to retract and pull the UAV towards the aircraft.

In addition to the above features, the system according to this aspect of the presently disclosed subject matter can optionally comprise one or more of features (i) to (xi) below, in any technically possible combination or permutation: I. The system further comprising a communication unit, wherein the computer device is configured to generate and transmit information, via the communication unit, to one or more in-flight UAVs; the information includes data indicative of the engagement location for causing the one or more in-flight UAVs to fly to the vicinity of the engagement location. II. The system is configured for retrieving two or more in-flight UAVs; wherein the computer device is configured to determine, based on computer logic, a retrieval order of the two or more in-flight UAVs and generate instructions, based on the retrieval order, directed to each one of the two or more in-flight UAVs for causing each one of the two or more in-flight UAVs to fly to the vicinity of the engagement location and engage with the retrieval head in a prescribed order of engagement. III. The system is configured to initiate a UAV retrieval process for retrieving a given in-flight UAV, responsive to information received from the inflight UAV indicating a request for retrieval.

IV. wherein the information received from the in-flight UAV is indicative of a depletion of a resource or a completion of a mission.

V. wherein the retrieval device comprises an extendable member connected at one end to the retrieval head and configured to extend toward the outside of the aircraft and be retracted back into the inside of the aircraft.

VI. wherein the extendable member is any one of: a telescopic rod, an extendable robotic arm, or a cable, suction tube.

VII. wherein the engagement mechanism is any one of: a magnetic device, a mechanical grip, a hook; a basket, or a suction nozzle.

VIII. wherein the retrieval head is a controllable flying retrieval head comprising one or more aerodynamic control surfaces operatively connected to a control unit configured to control flight of the retrieval head for directing the retrieval head during engagement with an in-flight UAV.

IX. The system further comprising a pick-and-place mechanism configured to pick a retrieved UAV and place the UAV at a designated storage place. X. The system is configured to operate partially or completely autonomously. XI. The system further comprising a UAV deployment sub-system configured for deploying a UAV from the aircraft to the air.

According to another aspect of the presently disclosed subject matter there is provided a method of retrieving one or more in-flight UAVs into an in-flight aircraft, the method comprising: responsive to instructions provided by a computer device, extending a retrieval device outside the aircraft towards an engagement location where a UAV is expected to be located; engaging between the retrieval device and the UAV at the engagement location; responsive to successful engagement between the retriever head and the UAV, retracting the retrieval device and pulling the UAV towards the aircraft.

In addition to the above features, the method according to this aspect of the presently disclosed subject matter can optionally comprise one or more of features (i) to (xi) above, mutatis mutandis, in any technically possible combination or permutation. The presently disclosed subject matter further contemplates a carries aircraft comprising an in-flight UAV retrieval system as disclosed herein.

The presently disclosed subject matter further contemplates a non-transitory computer readable program storage device configured with instructions for executing operations for performing the method of in-flight UAV retrieval as disclosed herein. BRIEF DESCRIPTION OF THE DRAWINGS

In order to understand the presently disclosed subject matter and to see how it may be carried out in practice, the subject matter will now be described, by way of non- limiting examples only, with reference to the accompanying drawings, in which:

Fig. 1 is a schematic illustration of UAV deployment from a carrier aircraft, in accordance with some examples of the presently disclosed subject matter;

Fig. 2 is a schematic illustration of UAV retrieval to a carrier aircraft, in accordance with some examples of the presently disclosed subject matter; Fig. 3 is a block diagram schematically showing retrieval system 120, in accordance with some examples of the presently disclosed subject matter;

Fig. 4 is a schematic illustration of a carrier aircraft carrying a UAV retrieval system in side view, in accordance with some examples of the presently disclosed subject matter;

Fig. 5 is a schematic illustration of a carrier aircraft carrying a UAV retrieval system in back view, in accordance with some examples of the presently disclosed subject matter; and

Fig. 6 is a flowchart illustrating operations performed in accordance with some examples of the presently disclosed subject matter.

DETAILED DESCRIPTION OF THE PRESENTLY DISCLOSED SUBJECT MATTER

Unless specifically stated otherwise, as apparent from the following discussions, it is appreciated that throughout the specification discussions utilizing terms such as "determining", "transmitting", "receiving", "generating", or the like, include actions and/or processes of a computer that manipulate and/or transform data into other data, said data represented as physical quantities, e.g. such as electronic quantities, and/or said data representing physical objects.

The terms "computer", "computer device", "system", "sub-system" mentioned below with respect to the drawings or variations thereof should be expansively construed to include any kind of hardware electronic device comprising data processing circuitry capable of executing and generating instructions and including a processor possibly operatively connected to a computer memory (e.g. digital signal processor (DSP), a microcontroller, a field programmable gate array (FPGA), an application specific integrated circuit (ASIC), etc.), or any other device with data processing circuitry, and/or any combination thereof.

As used herein, phrases such as "for example," "such as", "for instance" and variants thereof may be used to describe non-limiting embodiments of the presently disclosed subject matter. Reference in the specification to "one case", "some cases", "other cases" or variants thereof means that a particular feature, structure or characteristic described in connection with the embodiment(s) is included in at least one embodiment of the presently disclosed subject matter. Thus the appearance of the phrase "one case", "some cases", "other cases" or variants thereof does not necessarily refer to the same embodiment(s). It is appreciated that certain features of the presently disclosed subject matter, which are, for clarity, described in the context of separate embodiments, may also be provided in combination in a single embodiment. Conversely, various features of the presently disclosed subject matter, which are, for brevity, described in the context of a single embodiment, may also be provided separately or in any suitable sub-combination. In embodiments of the presently disclosed subject matter, fewer, more and/or different stages than those shown in Fig. 6 may be executed. In embodiments of the presently disclosed subject matter, one or more stages illustrated in Fig. 6 may be executed in a different order and/or one or more groups of stages may be executed simultaneously. Elements in Figs. 3 to 5 can be made up of a combination of software and hardware and/or firmware that performs the functions as defined and explained herein. Elements in Figs. 3 to 5 which are drawn as a single unit may be divided, in practice, into several units, and elements in Figs. 3 to 5 which are drawn as separate units, may be consolidated, in practice, into a single unit.

The term "comprising" (A comprising B) or its variations as used herein should be broadly interpreted to mean "including" (A including B) as well as "operatively connected to" (A is operatively connected to B).

The term UAV as used herein includes both UAVs capable of vertical takeoff and landing (VTOL), as well as UAVs capable of conventional (horizontal) takeoff and landing and UAVs equipped with any type of combination of takeoff and landing capabilities. The disclosed subject matter can be similarly implemented in any one of these types of UAVs.

Bearing the above in mind, attention is now drawn to Fig. 1 showing a schematic illustration of an example of UAVs 110 deployment from a carrier aircraft 100. According to this example, one or more UAVs are released into the air from a flying aircraft through a door or some other opening. The door or opening can be located at the rear of the aircraft as illustrated, or at any other location, such as the side of the aircraft, or the aircraft's floor. Essentially, the UAVs can have any size, provided that the size allows the UAVs to be carried by the carrier aircraft.

The UAV deployment mechanism can be implemented in various ways. According to one example, deployment of UAVs can be executed manually by an operator onboard the carrier aircraft who pushes or throws or otherwise causes one or more UAVs to be released outside the aircraft.

According to another example, UAVs can be automatically (and possibly autonomously) deployed by various types of deployment mechanisms. A number of examples of automatic deployment mechanisms are described below:

One or more UAVs can be placed on a surface above a trap-door and be deployed by opening the door and causing the UAV to fall or slide outside the aircraft. In some examples, the trap-door can be open autonomously e.g. when the carrier aircraft reaches a certain destination. - One or more UAVs can be placed on a moving platform (e.g. conveyer belt) extending towards the aircraft's door or other opening, possibly the ending (edge) of the moving platform extending outside of the aircraft. Once the platform is activated, the UAVs are moved on top of the platform until they reach the end of the platform where they are released into the air. A robotic arm can be used for holding a UAV, carrying it from its storage location and releasing/pushing/throwing the UAV outside the aircraft. For example, UAVs can be stored inside the aircraft on shelves and one or more robotic arms can be located between the storage area and the aircraft door. The robotic arm can be configured and operable to pick up a UAV, turn towards the door, and release the UAV outside the aircraft. Alternatively, the robotic arm can pick a UAV and place it on a platform (e.g. a conveyer belt or a trapdoor) from which it can be released.

UAVs can be deployed from a location other than the carrier aircraft. For example, UAVs can take off from a marine vessel or a ground base. In such cases the carrier aircraft is used only for UAV retrieval. Notably, some of the examples mentioned above can be either operated manually by a human, or by autonomous means.

Once released in the air, the UAVs become airborne and can execute their designated missions. According to some examples, UAVs systems are activated (e.g. including the engine to enable flying as well as other UAV onboard systems) before they are deployed into the air. Alternatively, according to other examples, UAVs are configured and operable to be automatically activated and/or to initiate autonomous flight capabilities (e.g. start an engine to enable flying) once (or immediately before) the UAV is deployed into the air. In some cases, it is desired to retrieve one or more deployed UAVs. For instance, this may be so when a UAV is deployed over a certain area and is incapable of flying back and landing at a safe location (e.g. a UAV deployed over unfriendly territory, or over the sea at a distance from land greater than the flying range of the UAV). In such cases it is desired to collect the UAVs back into the carrier aircraft upon completion or stoppage of their mission. Such capability would enable to reduce the risk of losing the UAVs in various missions and would help to increase the UAVs operational range.

The presently disclosed subject matter therefore includes an in-flight (during flight) UAV retrieval system, mountable on an aircraft, configured and operable to engage with one or more deployed UAVs while in the air, and collect the UAV back into the carrier aircraft. Fig. 2 is a schematic illustration of UAV retrieval into a carrier aircraft, according to some examples of the presently disclosed subject matter. According to some examples, UAV deployment and retrieval system 120 comprises a retrieval device 307 that can be extended away from the aircraft towards a UAV, connects to the UAV, and then pulls it back into the aircraft. Engaging with the UAV at a safe distance from the aircraft helps to reduce the risk of accidental collision between the UAV and the carrier aircraft.

As mentioned above, according to some examples, UAV deployment and retrieval system 120 can comprise a robotic arm or a similar device, which can be further configured and operable to place a retrieved UAV back at a storage location (e.g. a dedicated shelf of platform). In some examples of an autonomous UAV retrieval system, the UAV is pulled by the retrieval device and released inside the aircraft over a designated platform. Once in the aircraft, the robotic arm can pick up the UAV from the platform and place the UAV at a designated storage location.

Fig. 3 is block diagram of UAV deployment and retrieval system 120, according to some examples of the presently disclosed subject matter. Notably, although the name "deployment and retrieval system", as well as certain examples in the description herein, imply the existence of deployment capabilities in system 120, in some cases system 120 may be designed for UAV retrieval only and include a retrieval sub-system 310 alone. In such cases, UAV deployment can be executed by other ways such as by a human operator or from a deployment platform other than carrier aircraft 100, etc. Also, in some examples, UAV deployment sub-system 330 and UAV retrieval sub-system can be implemented as two physically separated units.

According to some examples, system 120 includes platform (e.g. UAV) storage 301 designated for storing the platforms after retrieval and possibly also before deployment. Storage 301 can be located at a designated area in the aircraft where the platforms are stored. According to some examples (as illustrated in Fig. 4) storage 301 can comprise one or more shelves suitable for placing one or more platforms. As explained above, by way of non-limiting example, system 120 can optionally include a pick and place device 305, such as a robotic arm configured and operable to pick a platform from its storage location in storage 301 and place it at deployment platform 320 from which it can be deployed. Likewise, retrieval device 307 can be configured and operable to place a retrieved UAV on deployment platform 320 from which pick and place device 304 can pick the retrieved UAV and place it back at a designated storage location. Fig. 4 is a schematic illustration, in side view, of one non-limiting example of system 120 comprising storage 301 implemented as a shelf (or shelves) situated within the carrier aircraft fuselage and configured to store a plurality of UAVs 110. Fig. 4 further shows pick and place device 305. Fig. 5 is a is a schematic illustration, in front view, of one non-limiting example of system 120 showing a pick and place device 305 implemented as a robotic arm located between shelves carrying UAVs on both sides of the fuselage. Notably, in some examples system 120 can be carried in a container separate from the aircraft (e.g. a designated aerodynamic shaped container) which can be externally fixed to the aircraft.

Reverting back to Fig. 3, system 120 shows optional deployment sub-system 330 as described above and retrieval sub-system 310. Retrieval sub-system 310 comprises a retrieval device 307 and retrieval device control unit 309 operatively connected to the retrieval device and configured and operable to control the operation of retrieval device 307. As mentioned above, retrieval device 307 is configured and operable to be extended away from the carrier aircraft, connect with a UAV, and pull the UAV back into the aircraft.

To facilitate retrieval of the UAV, the retrieval device 307 can comprise an extendable member 130. In general, the extendable member can be designed so it can be extended from the aircraft to the exterior of the aircraft in order to reach a nearby UAV, and then be retracted, and pull (or in some cases push) the UAV back into the aircraft. The retrieval device can include any type of suitable extendable member, including for example any one of: a cable, a boom, a telescopic rod, an air suction tube (connected to a suction device), an electromagnetic cable, a chain and the like. According to one non-limiting example, retrieval device 307 comprises a winch configured and operable to unwind and release a cable or strap or chain, etc. (having a desired firmness) outside the aircraft. According to another example, retrieval device 307 comprises a telescopic rod, which is configured and operable to be extended outside the aircraft. According to yet another example, retrieval device 307 comprises an air suction tube connected to a suction device and extendable towards the UAV. According to another example, retrieval device 307 comprises a robotic arm, which is configured and operable to be extended outside the aircraft. It is noted that the above list of examples is not meant to be exhaustive and other types of retrieval device 307 suitable for being extended towards the UAV are also contemplated to be within the scope of the presently disclosed subject matter.

Retrieval device control unit 309 is configured and operable to provide operational instructions to the retrieval device including, for example, instructions to extend the extendable member towards the outside the aircraft and instructions to retract the extendable member towards the inside of the aircraft (e.g. once a UAV has been attached to the extendable member).

Retrieval sub-system 310 can further comprise retriever head 311 located near one end of the extendable member 130 of retrieval device 307. The retriever head 311 is configured and operable to connect to the UAV and pull the UAV once the extendable member is retracted back towards the carrier aircraft. Engagement between the retriever head 311 and the UAV can be facilitated in various ways. According to one example, engagement is obtained by magnetic power. In such a case, retriever head 311 can comprise a magnet (e.g. electromagnet) suitable for firmly connecting to the UAV. According to another example, engagement is obtained by mechanical power. In such a case, the retriever head 311 can comprise for instance a clasp (e.g. in the form of a robotic mechanical clasp or hand) configured and operable to grip onto the UAV. Alternatively, the retriever head 311 can comprise a hook for hooking onto the UAV. Further alternatively, the retriever head 311 can comprise a basket or net for catching the UAV. Yet further, the retrieval head can comprise a suction nozzle (connected to a suction tube) configured to apply suction force to engage with the UAV. It is noted that the above list of examples is not meant to be exhaustive and other techniques suitable for engaging with the UAV are also contemplated to be within the scope of the presently disclosed subject matter.

Retrieval device 307 can comprise (e.g. as part of the retriever head 311) retriever head control unit 313 configured and operable to control the operations of the retriever head. For example, this may include generating instructions to activate the retriever head when in close proximity of the UAV (e.g. activate an electromagnet, open or close a clasp, extend and/or maneuver a hook or basket, and the like). Furthermore, the retriever head 311 can be attached to the extendable member such that it can be moved around one or more axes, providing one or more (e.g. two, four, five, six) degrees of freedom with respect to the extendable member. For example retriever head 311 can be gimbaled to the extendable member 130. Optionally, the extendable member can be gimbaled at the other end to provide further degrees of freedom to the extending element. This can help to achieve more accurate control over the extending element and/or the retriever head during engagement with a UAV. Retriever head control unit 313 can be further configured and operable to generate instructions for controlling movement of retriever head e.g. relative to the extendable member or relative to the UAV. According to some examples, retriever head 311 can comprise various sensors for providing sensing data during engagement to the UAV. The sensors can include for example, proximity sensors indicating proximity to the UAV, image sensors for capturing images of the UAV and the surrounding environment during engagement, RADAR, other RF sensors, etc. Retriever head 311 can also comprise a positioning device for determining the position of the retriever head, e.g. relative to the carrier aircraft and UAV in order to enable accurate engagement with the UAV. Positioning device can be an absolute positioning device (e.g. GPS based) or relative (e.g. sensors indicative of a position relative to the known position of the carrier aircraft determined by a positioning device onboard the carrier aircraft). According to some examples retriever head 311 can comprise a communication unit configured and operable to communicate with the UAV. Communication with the UAV can be used for example for identifying the UAV. Communication with the UAV can be used during the engagement phase (process) in order to facilitate smooth and accurate engagement between the retriever head and the UAV. For example, communication with the UAV can be used for transmitting to the UAV positioning data of the retriever head 311 and receiving from the UAV, the UAV position, in order to enable accurate engagement between the two. Exchange of positioning data between the retriever head and the UAV can occur repeatedly throughout the engagement process in order to maintain updated information of their relative position. According to an example, where a basket or net is used for the retriever head, communication between the UAV and the carrier aircraft can be used for positioning the UAV above the basket and, once in position, generating instructions for turning off the UAV rotors so it falls into the basket without or with little damage to the rotors.

PCT Patent Application having international publication number WO2013/102903, entitled "DEVICES, SYSTEMS AND METHODS FOR REFUELING AIR VEHICLES" for the Applicant (incorporated herein by reference in its entirety) discloses an in-flight refueling system which includes a selectively steerable body which can be steered in the air during refueling to an engagement enabling position between refueling unit and the receiver aircraft being refueled. The in-flight refueling system includes aerodynamic control surfaces such as wings for enabling stabilization and control over the system while in the air. The application also includes methods of controlling the refueling unit. For example, Figs. 3 to 17 in Application WO2013/102903 describe various aspects of the refueling device. It is suggested to use similar principles and designs for providing a UAV retrieval device for retrieving deployed UAVs as described above (named here "controllable flying retrieval head"). According to the presently disclosed subject matter, various parts of the refueling device as described in Application WO2013/102903 are adapted for the purpose of UAV retrieval. For example, a cable can replace the refueling hose and a retriever head 311 configured and operable to engage with the UAV, as explained above, can replace a boom, including a fuel transfer nozzle. The retrieval sub-system disclosed herein can further include (e.g. within main computer 315 or otherwise operatively connected thereto) a flight control unit for generating instructions to the flight control devices (e.g. rudder, ailerons, throttle, etc.) in order to direct the retrieval head, much like a small aircraft, to engage with an inflight UAV. System 120 can further comprise a computer device (e.g. main computer 315) operatively connected to other components of the system and configured and operable to generate instructions for controlling their operations. System 120 can further include a user interface including a display screen and one or more user interaction devices (e.g. keyboard and mouse; e.g. operatively connected to main computer) for enabling monitoring and control of the system by a human operator.

Fig. 6 is a flowchart demonstrating operations executed during UAV retrieval, according to some examples of the presently disclosed subject matter. Operations described with reference to Fig. 6 can be executed for example by system 120 described above. However, the specifics of system 120 should not be construed as limiting the scope of the method, and the operations can be performed by other systems having an alternative design. At block 601 instructions to retrieve one or more UAVs are received. The instructions can be received for example at main computer 315. Retrieval can be executed as a manual process controlled by a human operator or as a partially or fully autonomous process controlled by a computer (e.g. main computer 315). In case of manual operation, a human operator can interact with system 120 (e.g. via user interface operatively connected to main computer 315) and generate instructions to initiate the UAV retrieval process. The operator can continue to control the UAV retrieval device throughout the UAV retrieval process. For example, the operator can manually control extension of the retrieval device toward the UAV, and manually operate the retrieval device head in order to engage with the UAV. Once engaged, the operator can use retrieval device controls for retracting the retrieval device back into the aircraft together with the UAV. This can be executed, for example, with the help of real-time information (e.g. real-time imaging generated and transmitted from an image sensor located for example on the extendable member) which is displayed on a display device operatively connected to main computer 315.

Alternatively, the operator can merely generate instructions to initiate the retrieval process, which is then executed autonomously. Further alternatively, the initiation, as well as execution of the UAV retrieval process, can be performed autonomously, e.g. by instructions received from a remote device. In some examples, the remote device can be one or more UAVs 110 which can be configured and operable to communicate with system 120 and request retrieval based on certain predefined logic. For example, a UAV can request retrieval once its fuel level is lower than a certain threshold, or once a mission assigned to the UAV is completed.

At block 603 the position of one or more UAVs is determined. To this end, main computer 315 can communicate (e.g. using communication unit 317) with the deployed UAVs to determine their location. According to one example, each UAV can determine its position using an on-board positioning device (e.g. GPS) and send this information to main computer 315. Additionally or alternatively, the positioning device onboard the carrier aircraft determines the position of the UAVs e.g. based on signal transmissions between the carrier aircraft and UAVs (e.g. by an interferometer), one or more image sensors, radar or the like. According to some examples, in case there are more than one UAV which needs to be retrieved, a retrieval priority scheme dictating an order of retrieval of the UAVs is determined. The order of retrieval can be determined either by an operator or by a computer (e.g. main computer 315). Computer logic (stored for example in data-storage device 319 (including for example transitory and non-transitory computer memory) operatively connected to main computer 315) for determining the order of retrieval, can take into consideration various parameters including by way of example:

Distance from carrier aircraft;

Urgency of retrieval - for example resource (e.g. fuel) depletion level, where a UAV with greater depletion, which is therefore at a greater risk, is retrieved first.

Type of UAV or UAV payload - for example more costly UAVs are retrieved before less costly ones, or UAVs carrying more costly (or more classified/sensitive) payloads are retrieved before UAVs carrying less costly (or unclassified) payloads.

Different parameters can be considered together to determine a more accurate picture of a real-time scenario. For example, fuel depletion and distance of UAV from aircraft can be considered together to determine the order of retrieval based on the anticipated risk. In different scenarios, each one of the parameters can be given a certain weight and an overall score can be calculated (e.g. by main computer 315) for each UAV where the order of retrieval is in accordance with the score given to each UAV (e.g. UAVs with a greater score are retrieved before UAVs with a lesser score). Information relevant for executing this calculation can be obtained in real-time from each UAV. Additionally, in some cases, main data-storage device 319 can be used for storing information with respect to each deployed UAV (e.g. the importance/price of each UAV or respective onboard payload; the more costly a UAV and/or its payload, the higher the assigned score). Main computer 315 can be configured and operable to retrieve this information from the data-storage and calculate respective scores based on the parameter values and its assigned weight. Information can also be received from an external source such as from another computer device (e.g. on another aircraft or on a ground base station), or from an operator. Computer 315 can be further configured to calculate a score for each UAV and determine a derived retrieval order based on the score. In some examples, a score can be calculated for each parameter based on a parameter value multiplied by parameter weight, and the scores of different parameters can be combined to obtain a final score.

In some examples, instructions can be sent to the UAVs indicating a respective engagement location, and instructing the UAV to travel to that location. According to some examples, the engagement location is set to be in the vicinity (within some predefined distance) of the extension vector of the extendable member of the retrieval device, such that the retrieval device can engage with the UAV somewhere along this vector. The instructions can be generated while taking into consideration the current, and possibly future, positioning of the carrier aircraft (e.g. including the carrier aircraft's speed, direction and altitude). The instructions can be generated while also taking into consideration the positioning data as well as other operational data of the UAV (e.g. including current and maximal speed, current and maximal altitude, direction, hovering ability, etc.). Instructions to travel to an engagement location can be given to each UAV based on the previously determined retrieval order. According to some examples, responsive to instructions, the UAV travels to the engagement location. Alternatively or additionally, the carrier aircraft can travel towards the engagement location. In some examples, the UAV stays in place (assuming it has hover capabilities), or stays in its course and only the carrier aircraft is maneuvered towards the UAV to enable engagement. In other examples, both the UAV and the carrier aircraft travel towards a certain engagement location. During retrieval of each UAV, the retrieval device is controlled to be extended away from the carrier aircraft and towards the UAV (e.g. near the engagement location) where the UAV is expected to be (block 607).

Upon arrival to the engagement location, when in a certain proximity to the UAV, the retriever head is activated in order to engage with (e.g. grab) the UAV (block 609). Once the retriever head is engaged with the UAV, the extended member of the retrieval device is retracted back and pulls the UAV into the aircraft (block 611). According to some examples, various sensors attached to the retrieval device head can be used for monitoring and determining complete engagement. For example, a micro- switch (electronic or mechanical) or an ultrasonic sensor can be used for determining that the UAV is successfully engaged.

As explained above, in some examples, the retrieved UAV can be stored (e.g. by an autonomous pick and place device, or by a human operator) in a designated storage location (block 613). The retrieval device and retrieval device head can be repeatedly operated until all UAVs are retrieved.

According to some examples, during engagement, instructions are provided to the UAV from system 120 in order to control the UAV during the process. The instructions can include commands for controlling the UAV flight, essentially taking over the UAV flight control, in order to control the UAV to more accurately reach the retrieval head and enable smooth engagement. In some examples, the instructions can also include commands for switching off the rotors and/or engine of the UAV during or immediately after engagement.

It is to be understood that the presently disclosed subject matter is not limited in its application to the details set forth in the description contained herein or illustrated in the drawings. The presently disclosed subject matter is capable of other embodiments and of being practiced and carried out in various ways. Hence, it is to be understood that the phraseology and terminology employed herein are for the purpose of description and should not be regarded as limiting. As such, those skilled in the art will appreciate that the conception upon which this disclosure is based may readily be utilized as a basis for designing other structures, methods, and systems for carrying out the several purposes of the presently disclosed subject matter.

The present invention has been described with a certain degree of particularity, but those versed in the art will readily appreciate that various alterations and modifications may be carried out without departing from the scope of the following claims.