Patent Publication Number: US-2023150668-A1

Title: Airborne recovery of unmanned aerial vehicles

Description:
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
     The invention(s) herein may have been made with government support under Contract Number NEID-SC-0215-09 awarded by the U.S. Army Research Lab. The government may have certain rights in the invention(s). 
    
    
     BACKGROUND 
     Field 
     This disclosure relates generally to unmanned aerial vehicles (UAV&#39;s), in particular to systems and methods for recovery of an airborne UAV or other target aircraft by an airborne host aircraft. 
     Related Art 
     Unmanned aerial vehicles (UAV&#39;s) are aircraft that are piloted without a human pilot onboard. UAV&#39;s may be used for transport, surveillance, communications, weapons, and other uses. UAV&#39;s typically take off from the ground and return to the ground, which limits their versatility and usefulness. Recovery of UAV&#39;s or other aircraft in-flight may simplify missions and improve outcomes. Existing approaches to in-flight recovery are complex and unreliable. Improvements to these and other drawbacks are desirable. 
     SUMMARY 
     The embodiments disclosed herein each have several aspects no single one of which is solely responsible for the disclosure&#39;s desirable attributes. Without limiting the scope of this disclosure, its more prominent features will now be briefly discussed. After considering this discussion, and particularly after reading the section entitled “Detailed Description,” one will understand how the features of the embodiments described herein provide advantages over existing systems, devices and methods for recovering unmanned aerial vehicles (UAV&#39;s) or other aircraft in flight. 
     The following disclosure describes non-limiting examples of some embodiments. Other embodiments of the disclosed systems and methods may or may not include the features described herein. Moreover, disclosed advantages and benefits may apply only to certain embodiments of the invention and should not be used to limit the disclosure. 
     Features for airborne recovery of an unmanned aerial vehicle (UAV). A towline may be deployed by a host aircraft in-flight in order to recover a target UAV that is also in-flight. The towline or a portion thereof may be oriented nearly vertical. The towline may have a fitting thereon. A capture mechanism on the target UAV may have one or more moveable portions such as deployable flaps that deploy and engage with the fitting on the near vertical towline. The flaps may stow to secure the target aircraft to the towline and fitting. The host aircraft may then retract the towline to pull in the target UAV to the host aircraft using a hoist system having a winch. A latching system located in a pylon of the host aircraft, which may be under a wing, may have a latch housing that secures with a towline connector coupled with the towline end fitting and that engages with and secures the target UAV. The host aircraft may have multiple hoist systems for deployment and/or recovery of multiple target UAV&#39;s. 
     Disclosed herein are embodiments of a system for recovery of a target aircraft by a host aircraft during forward flight that can include a towline including a proximal section configured to be coupled with the host aircraft and a distal section configured to be paid out from the host aircraft, a fitting coupled with the distal section of the towline, and a capture mechanism including a first movable portion and a second movable portion configured to be coupled with a fuselage of the target aircraft. 
     Any embodiments of the devices, systems, and methods disclosed herein can include, in additional embodiments, one or more of the following features, components, and/or details, in any combination with any of the other features, components, and/or details of any other embodiments of the devices, systems, and methods disclosed herein: wherein the first movable portion of the capture mechanism can be configured to move from a first position to a second position in which the first movable portion extends away from the fuselage of the target aircraft; wherein the second movable portion of the capture mechanism can be configured to move from a first position to a second position in which the second movable portion extends at an angle away from the fuselage of the target aircraft; wherein the capture mechanism can be configured to receive the towline in an opening defined by the first and second movable portions in the second positions and to permit vertical movement of the towline through the opening; wherein the capture mechanism can be configured to prevent the fitting attached to the towline from moving vertically through the opening; wherein, in the first position, the first and second movable portions can be positioned near the fuselage, in line with the fuselage, or against the fuselage of the target aircraft; wherein the first and second movable portions can be configured to move to a capture position, or return to respective first positions, to secure the target aircraft to the towline; wherein the opening can be smaller than a maximum cross-sectional size of the fitting; wherein the first movable portion and the second movable portion can be configured to rotate between the respective first and second positions; wherein the first movable portion of the capture mechanism can be configured to move independent of the position of the second movable portion; wherein the first movable portion can be integral with or rigidly attached to the second movable portion such that the first and second movable portions move together as one unit between the first and second positions; wherein the capture mechanism can be configured to receive the towline in the opening with the distal section of the towline oriented less than 30 degrees off a vertical direction; and/or wherein the host aircraft includes a system for securing a target aircraft to a host aircraft, the system including a winch configured to be supported by a wing of the host aircraft and to have a deployable towline carried by the winch, one or more fleet pulleys, the towline configured to extend from the winch through the one or more fleet pulleys, an upper sheave, the towline configured to extend from the fleet pulley to the upper sheave, and a towline connector, the towline configured to extend below the aircraft and be reeled in by the winch to secure the target aircraft with the host aircraft. 
     Also disclosed herein are embodiments of a system for recovery of a target aircraft by a host aircraft during forward flight, wherein the system can include a wing root region defined by an intersection of a wing and a fuselage of the target aircraft, the wing root region configured to receive from the host aircraft a towline having a fitting, one or more flaps configured to be moveably coupled with the fuselage, and one or more actuators configured to deploy the one or more flaps to a deployed position away from the fuselage. In some embodiments, the one or more flaps can define an opening configured to receive the towline therein, such that the fitting contacts the one or more flaps in response to relative vertical movement between the towline and the one or more flaps in the deployed position, and the one or more actuators can be further configured to stow the one or more flaps to a stowed position to secure the fitting and towline with the target aircraft. 
     Any embodiments of the devices, systems, and methods disclosed herein can include, in additional embodiments, one or more of the following features, components, and/or details, in any combination with any of the other features, components, and/or details of any other embodiments of the devices, systems, and methods disclosed herein: wherein, in the stowed position, the one or more flaps form an outer surface of the fuselage; wherein the one or more flaps include a first flap and a second flap; wherein the first and second flaps can be independently movable; wherein the fitting has a width greater than a width of the opening defined by the one or more flaps; wherein the one or more flaps can be configured to prevent the fitting from moving in an upward direction relative to the one or more flaps when the fitting has been moved into contact with the one or more flaps; and/or wherein the one or more flaps can be configured to receive the towline in the opening with at least part of the towline adjacent the fitting oriented less than 30 degrees off the vertical direction. 
     Also disclosed herein are embodiments of a method of recovering a target aircraft with a host aircraft during forward flight, wherein the method can include extending from the host aircraft a towline having a fitting, positioning the towline within a wing root region of the target aircraft with at least part of the towline oriented less than 30 degrees off a vertical direction, deploying one or more flaps from a fuselage of the target aircraft, positioning the towline within an opening defined by the one or more flaps in the deployed position, causing relative vertical movement between the one or more flaps and the towline to move the fitting near the one or more flaps, and stowing the one or more flaps with the fuselage to secure the target aircraft to the towline. 
     Any embodiments of the devices, systems, and methods disclosed herein can include, in additional embodiments, one or more of the following features, components, and/or details, in any combination with any of the other features, components, and/or details of any other embodiments of the devices, systems, and methods disclosed herein: further including retracting the towline into the host aircraft to move the target aircraft toward the host aircraft; wherein deploying the one or more flaps includes deploying a first flap and a second flap; and/or wherein the first and second flaps can be deployed independently of each other. 
     Also disclosed herein are embodiments of a system for securing a target aircraft to a host aircraft that can include a pylon attached to an underside of a wing of the host aircraft, a motorized winch supported within the pylon and having a towline carried by the winch, the winch configured to pay out and reel in the towline, a plurality of fleet pulleys supported within the pylon, the towline extending from the winch through the plurality of fleet pulleys, an upper sheave supported within the pylon, the towline extending from the fleet pulleys and around the upper sheave, and a towline connector on the towline. In some embodiments, the towline can be configured to extend from the upper sheave and exit the aircraft. An end fitting can be positioned on a distal end of the towline near the towline connector. The distal end of the towline can be configured to orient less than thirty degrees off a vertical direction for attachment of the end fitting with a target aircraft. The motorized winch can be configured to reel in the towline and target aircraft to secure the towline connector with the host aircraft. 
     Any embodiments of the devices, systems, and methods disclosed herein can include, in additional embodiments, one or more of the following features, components, and/or details, in any combination with any of the other features, components, and/or details of any other embodiments of the devices, systems, and methods disclosed herein: wherein the plurality of fleet pulleys include two pulleys oriented approximately horizontally; wherein the upper sheave can be oriented vertically; further including a latch housing configured to secure the towline connector; wherein the winch includes a cartridge through which the towline extends, the cartridge movable along an axle, such that a portion of the towline between the winch and the plurality of fleet pulleys may sweep a total angle of at least thirty degrees; further including one or more sway bars attached to an underside of the pylon and configured to laterally stabilize the secured target aircraft; wherein the one or more sway bars each extend laterally outward and downward from the pylon; further including a bottom sheave configured to guide vertical movement of the towline connector; and/or wherein the target aircraft includes one or more flaps configured to deploy and stow, wherein the flaps deploy to define an opening through which the towline is received, and wherein the flaps stow to guide the end fitting into a recess of the target aircraft. 
     Also disclosed herein are embodiments of a system for securing a target aircraft to a host aircraft that can include a winch configured to be supported by a wing of the host aircraft and to have a deployable towline carried by the winch, one or more fleet pulleys, the towline configured to extend from the winch through the one or more fleet pulleys, an upper sheave, the towline configured to extend from the fleet pulley to the upper sheave, and a towline connector on the towline configured to secure with the host aircraft, the towline configured to extend below the host aircraft and be reeled in by the winch to secure the target aircraft with the host aircraft. 
     Any embodiments of the devices, systems, and methods disclosed herein can include, in additional embodiments, one or more of the following features, components, and/or details, in any combination with any of the other features, components, and/or details of any other embodiments of the devices, systems, and methods disclosed herein: wherein the towline is configured to have a fitting on the towline to attach to the target aircraft; wherein a portion of the towline can be configured to be oriented less than thirty degrees off a vertical direction; further including a pylon attached to a wing of the host aircraft, the pylon supporting the winch; wherein the one or more fleet pulleys include first and second fleet pulleys oriented horizontally; wherein the upper sheave can be oriented vertically; further including a latch housing, wherein the towline connector can be configured to move up and down between a plurality of vertical positions, and wherein the latch housing can be configured to secure the towline connector at one or more of the plurality of vertical positions; and/or wherein the target aircraft includes one or more flaps configured to deploy and stow, wherein the flaps deploy to define an opening through which the towline can be received, and wherein the flaps stow to guide the end fitting into a recess of the target aircraft. 
     Also disclosed herein are embodiments of a method of securing a target aircraft to a host aircraft that can include deploying a towline from a winch, stabilizing the towline as it exits the winch, guiding the towline downward to cause the towline to exit the host aircraft, reeling in the towline using the winch after the towline has secured with the target aircraft, stabilizing the target aircraft under a wing of the host aircraft, and operating a latching system to secure the target aircraft with the host aircraft. In some embodiments, operating the latching system can include securing a towline connector of the towline to prevent the towline connector from movement vertically downward. In some embodiments, stabilizing the towline can include guiding the towline through a fleet pulley assembly. 
     In another aspect, a system for in-flight recovery of a target aircraft by a host aircraft during forward flight is described. The system may include a hoist or reel, a towline, and a capture mechanism. The reel is configured to attach with the host aircraft. The towline comprises an aft section with a fitting attached to the aft section, where the reel is configured to pay out the towline from the reel to extend the fitting away from the host aircraft during forward flight. The capture mechanism is configured to attach with the target aircraft and to transition from a first configuration to a second configuration. The capture mechanism is configured to capture the towline and/or a fitting thereof with the towline in a near-vertical orientation, e.g. less than 30 degrees relative to a vertical direction. In some embodiments, the capture mechanism can be configured to capture the towline and/or a fitting thereof with the towline at less than 45 degrees relative to a vertical direction. The towline may initially be greater than 30 degrees but the re-orient to be less than 45 or 30 degrees, etc. 
     In another aspect, a system for in-flight recovery of a target aircraft by a host aircraft during forward flight is described. In some embodiments, the system may include a towline that may include a proximal section configured to be coupled with a host aircraft and a distal section configured to be paid out from the host aircraft, a fitting coupled with the towline, and a capture mechanism that may include a first movable portion and a second movable portion configured to be coupled with or integral to a fuselage of the target aircraft. In any embodiments disclosed herein, the first movable portion of the capture mechanism may be configured to move between a first position in which the first movable portion is positioned in line with or against the fuselage of the target aircraft and a second position in which the first movable portion extends at an angle away from the fuselage of the target aircraft. Further, in any embodiments disclosed herein, the second movable portion of the capture mechanism may be configured to move between a first position in which the second movable portion is positioned in line with or against the fuselage of the target aircraft and a second position in which the second movable portion extends at an angle away from the fuselage of the target aircraft and the capture mechanism may be configured to receive the towline in an opening in the capture mechanism at least when the first and second movable portions are in the second position and to permit a movement of the towline through the opening in the capture mechanism until the fitting attached to the towline has moved into engagement with the capture mechanism. In any embodiments disclosed herein, the first and second movable portions may be configured to move to the first position to further restrain the fitting attached to the towline after the fitting has been moved into engagement with the first and second movable portions. 
     Further, any aspects or embodiments of the methods, devices and systems for in-flight recovery of a target aircraft by a host aircraft or the embodiments of the capture mechanisms disclosed herein may include, in additional embodiments, one or more of the following steps, features, components, and/or details, in any combination with any of the other steps, features, components, and/or details of any other embodiments disclosed herein: wherein the capture mechanism may be configured such that the towline cannot continue to be withdrawn through the opening in the capture mechanism when the fitting is in contact with an underside surface of the first and second movable portions; wherein the opening is smaller than a maximum cross-sectional size of the fitting; wherein the first and second movable portions may be configured to prevent the fitting from moving in an upward direction relative to the capture mechanism when the target aircraft is in an operable state and when the fitting has been moved into contact with an underside surface of the first movable portion and an underside surface of the second movable portion; wherein the first movable portion and the second movable portion may be configured to rotate between the first and second positions; wherein the opening is a space between the first and second movable portions; wherein the first movable portion of the capture mechanism may be configured to move between the first and second positions independent of the position of the second movable portion; wherein the fitting has body portion having a conical shape; and/or wherein the system may include a hoist configured to be integrated into or attached to the host aircraft and configured to draw out or withdraw the towline. 
     In another aspect, a capture mechanism for an unmanned aircraft is described. In some embodiments, the capture mechanism may include a first movable portion and a second movable portion configured to be coupled with or integral to a fuselage of the target aircraft and configured to capture and secure a towline to the target aircraft. In any embodiments, the first movable portion of the capture mechanism may be configured to move between a first position in which the first movable portion is configured to be positioned in line with or against the fuselage of the target aircraft and a second position in which the first movable portion is configured to extend at an angle away from the fuselage of the target aircraft. In any embodiments, the second movable portion of the capture mechanism may be configured to move between a first position in which the second movable portion is configured to be positioned in line with or against the fuselage of the target aircraft and a second position in which the second movable portion configured to extend at an angle away from the fuselage of the target aircraft. Some embodiments of the capture mechanism may be configured to receive a towline in an opening in the capture mechanism at least when the first and second movable portions are in the second position and configured to permit a movement of the towline through the opening in the capture mechanism until a fitting attached to the towline has moved into contact with the capture mechanism. In some embodiments, the first and second movable portions may be configured to move to the first position to further restrain the fitting attached to the towline after the fitting has been moved into engagement with the first and second movable portions. 
     Any embodiments of the methods, devices and systems for in-flight recovery of a target aircraft by a host aircraft or the embodiments of the capture mechanisms disclosed herein may include, in additional embodiments, one or more of the following steps, features, components, and/or details, in any combination with any of the other steps, features, components, and/or details of any other embodiments disclosed herein: wherein the capture mechanism may be configured such that a towline cannot continue to be withdrawn through the opening in the capture mechanism when a fitting attached to the towline is in contact with an underside surface of the first and second movable portions; wherein the opening is smaller than a maximum cross-sectional size of the fitting; wherein the first and second movable portions may be configured to prevent the fitting from moving in an upward direction relative to the capture mechanism when the fitting has been moved into contact with an underside surface of the first and second movable portions; wherein the first movable portion and the second movable portion may be configured to rotate between the first and second positions; wherein the opening is a space between the first and second movable portions; and/or wherein the first movable portion of the capture mechanism may be configured to move between the first and second positions independent of the position of the second movable portion. 
     In another aspect, a method of capturing a target aircraft in flight is described. In any embodiments disclosed herein, the method of capture a target aircraft may include maneuvering a target aircraft having a capture mechanism may include a first movable portion and a second movable portion toward a towline from a host aircraft so that the towline is directed to a wing root on the target aircraft, positioning at least a leading edge of the second movable portion aft of the towline by moving the second movable portion to a second position in which the second movable portion extends away from the fuselage of the target aircraft and is positioned aft of the towline, positioning at least a trailing edge of the first movable portion forward of the towline by moving the first movable portion to a second position in which the first movable portion extends away from the fuselage of the target aircraft and is positioned forward of the towline, causing upward vertical movement of the towline relative to the target aircraft to move a fitting on the towline in contact with the first and second movable portions, moving the first and second movable portions to a first position of the first and second movable portions to prevent the fitting from moving away from the first and second movable portions, and/or withdrawing the towline to move the target aircraft toward the host aircraft. 
     Any embodiments of the methods, devices and systems for in-flight recovery of a target aircraft by a host aircraft or the embodiments of the capture mechanisms disclosed herein may include, in additional embodiments, one or more of the following steps, features, components, and/or details, in any combination with any of the other steps, features, components, and/or details of any other embodiments disclosed herein: wherein the first or second movable portions are approximately in line with or adjacent to a fuselage of the target aircraft in the first position of the first and second movable portions; may include moving the second movable portion to the second position before moving the first movable portion to the second position, wherein the second movable portion is aft of the first movable portion; may include moving the first and second movable portions to the second position simultaneously; wherein the first movable portion is integral with the second movable portion; and/or wherein the method may further include securing the target aircraft to the host aircraft. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The foregoing and other features of the present disclosure will become more fully apparent from the following description and appended claims, taken in conjunction with the accompanying drawings. Understanding that these drawings depict only several embodiments in accordance with the disclosure and are not to be considered limiting of its scope, the disclosure will be described with additional specificity and detail through use of the accompanying drawings. In the following detailed description, reference is made to the accompanying drawings, which form a part hereof. In the drawings, similar symbols typically identify similar components, unless context dictates otherwise. The illustrative embodiments described in the detailed description, drawings, and claims are not meant to be limiting. Other embodiments may be utilized, and other changes may be made, without departing from the spirit or scope of the subject matter presented here. It will be readily understood that the aspects of the present disclosure, as generally described herein, and illustrated in the drawing, may be arranged, substituted, combined, and designed in a wide variety of different configurations, all of which are explicitly contemplated and make part of this disclosure. 
         FIG.  1    shows a side view of an embodiment of a system for recovery of a target aircraft by a host aircraft. 
         FIGS.  2 A- 2 K  show sequential side views of a host and target aircraft in-flight illustrating an embodiment of a method of recovering the target aircraft using the recovery system shown in  FIG.  1   . 
         FIG.  3    is a perspective view of another embodiment of a target aircraft having a capture mechanism with a towline extending downward from a host aircraft. 
         FIGS.  4 A- 4 D  are partial sequential perspective views of another embodiment of a capture mechanism on a target aircraft capturing a towline extending downward from a host aircraft. 
         FIGS.  5 A- 5 F  are partial sequential perspective views of another embodiment of a capture mechanism on a target aircraft capturing a towline extending downward from a host aircraft. 
         FIGS.  6 A- 6 F  are sequential side views of another embodiment of a target aircraft having a capture mechanism with a towline extending downward from a host aircraft and located rearward of the target aircraft wing. 
         FIGS.  7 A- 7 H  are various views of various embodiments of end fittings that may be attached to a towline for any of the recovery systems described herein. 
         FIGS.  8 A- 8 C  are front, perspective and top views respectively of a host aircraft in flight having multiple target aircrafts secured to the host aircraft wings via hoist systems. 
         FIGS.  9 A- 9 D  are various views of the target aircraft of  FIGS.  8 A- 8 C  showing the target aircraft wings in deployed and stowed positions. 
         FIG.  10    is a perspective view of the host and target aircrafts of  FIGS.  8 A- 8 C  showing the host aircraft recovering the target aircraft in flight via a towline extending from one of the hoist systems. 
         FIGS.  11 A- 11 C  are perspective, side and front views, respectively, of the target aircraft secured to the hoist system of  FIGS.  8 A- 8 C . 
         FIGS.  12 A- 12 D  are various views of a pylon of the hoist systems of  FIGS.  8 A- 8 C . 
         FIGS.  13 A and  13 B  are perspective and cross-section views, respectively, of a motorized winch and pulley/sheave system of the hoist systems of  FIGS.  8 A- 8 C . 
         FIG.  14 A  is a side view of a schematic of an embodiment of a latching system that may be used with the hoist systems of  FIGS.  8 A- 8 C . 
         FIG.  14 B  is a side view of a portion of the embodiment of the towline, towline connector, and end fitting as shown in  FIG.  14 A . 
         FIG.  14 C  is a top view of the embodiment of the latch assembly shown in  FIG.  14 A . 
     
    
    
     DETAILED DESCRIPTION 
     The following detailed description is directed to certain specific embodiments of the development. In this description, reference is made to the drawings wherein like parts or steps may be designated with like numerals throughout for clarity. Reference in this specification to “one embodiment,” “an embodiment,” or “in some embodiments” means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the invention. The appearances of the phrases “one embodiment,” “an embodiment,” or “in some embodiments” in various places in the specification are not necessarily all referring to the same embodiment, nor are separate or alternative embodiments necessarily mutually exclusive of other embodiments. Moreover, various features are described which may be exhibited by some embodiments and not by others. Similarly, various requirements are described which may be requirements for some embodiments but may not be requirements for other embodiments. 
       FIG.  1    depicts an embodiment of a system  90  for airborne or in-flight recovery of a target aircraft T having a capture mechanism  100 , using a towline from a host aircraft H. Some embodiments disclosed herein include an improved capture mechanism and system for unmanned aerial vehicles (UAV&#39;s) or other target aerial vehicles (collectively, target aerial vehicle or vehicles or target aircraft) for capturing a towline tethered to a host aircraft. For clarity, in  FIG.  1    the host aircraft H, towline  102 , and the target aircraft T are not necessarily to scale. The host aircraft H may be any type of manned or unmanned aircraft. The host aircraft H may be a conventional aircraft such as a jet or prop-driven aircraft, UAV, or other aircraft type. The target aircraft T may be any type of UAV, although the target aircraft T may also be a manned or piloted aircraft in any embodiments disclosed herein. The host and/or target aircraft H, T in any embodiments disclosed herein may be forward flying aircraft. In some embodiments, one or both of the host and target aircraft H, T may be in vertical flight, such as a vertical takeoff and landing (VTOL) aircraft, helicopter, or other types of aircraft. 
     UAV&#39;s are aircraft without a human pilot onboard. UAV&#39;s may be piloted manually by a remote operator and/or through autonomous or semi-autonomous controls. The remote operator may pilot the UAV based on the UAV&#39;s flight cameras, gauges, and other control sensors. The target aircraft T may be a UAV with a fuselage F, one or more flight surfaces, such as wings W, extending outwardly from the fuselage, and a propulsion system, such as a combustion or electric engine. UAV&#39;s may be used in a number of roles, such as aerial reconnaissance and ground surveillance, monitoring terrestrial objects and people, scientific experiments, geological surveys, military or non-military contexts, weapon delivery, and others. 
     Larger aircraft may generally have greater operable ranges than smaller or lighter UAV&#39;s. Thus, carrying a UAV on the host aircraft H and launching therefrom may expand the useful range of the UAV. However, safely landing the UAV for terrestrial recovery may be difficult or impossible in certain circumstances. For example, the geography may lack sufficient landing space, or the landing spaces may be in undesirable locations (e.g., under enemy control). Moreover, existing methods of aerial recovery of UAV&#39;s are impractical and unreliable. Accordingly, a need exists for the reliable recovery of a UAV in-flight. 
     Some embodiments disclosed herein include a capture mechanism to enable airborne recovery of a wide range of small, unmanned air vehicles or other target aircraft T in flight using the towline  102  with a simple, passive end feature or fitting deployed from the host aircraft H. Some embodiments of the capture mechanism on the target aircraft may be scalable and/or tunable to conform to a wide range of airframe shapes and sizes. In some embodiments, the components and methods of capture employ existing airframe features (e.g. leading or trailing edge of wing, left or right hand side of fuselage) to funnel or bias the towline  102  to the capture mechanism. Using these relatively large airframe features as a towline funnel or guide increases reliability and leads to very high probability of recovery, even for a small UAV with poor or moderate flight control. 
     Once the target aircraft T captures the towline fitting, some embodiments of the target aircraft T may be transitioned to a passively stable towed body by retracting or rotating its wings and reducing or stopping thrust. In some embodiments, the host aircraft H may use a hoist system in a pod on or in the host aircraft H to reel-in the target aircraft T (e.g. as shown in  FIGS.  8 A- 14   ). The target aircraft T may be refueled or recharged by the host aircraft H and sent on a subsequent sortie, have maintenance performed on the target aircraft T, be transported to a mission point via captive carriage on the host aircraft H where the target aircraft T may be launched, or other actions taken. In some embodiments, the target aircraft T may conduct its mission and then be recovered by the host aircraft H. The host aircraft H may then transport the target aircraft T back to base for service (e.g. refuel, rearm, maintenance, etc.). Or, such maintenance, refueling, rearming, etc., may be provided to the target aircraft T while attached to the host aircraft H so that the target aircraft T may be launched or re-launched from the host aircraft H for another mission without having to return to base. Some embodiments of the capture mechanisms disclosed herein use a simple towline and hoist and may be used for capturing a very broad array of small UAV&#39;s (e.g. different airframe shapes, propulsion types, propulsion locations, etc.). Some embodiments of the capture mechanisms disclosed herein may be integrated into the fuselage during manufacturing of the UAV&#39;s and/or may be retrofit to existing fuselages of UAV&#39;s. 
     Existing solutions for in-flight recovery of aircraft are complex and unreliable. Today, some small UAV&#39;s may be very limited in their range and utility. Recovery of UAV&#39;s using conventional methods (e.g. skid landing or net arrest) risks significant damage. This precludes them from carrying expensive, advanced sensors and other equipment. The recovery systems according to the present disclosure provide reliable airborne approaches that may overcome these drawbacks. The host aircraft H may transport a small UAV or other target aircraft T long distances to a mission point. With little risk of damage to the target aircraft T upon recovery, small UAV&#39;s may carry expensive, advanced sensors with less risk of damage to such sensors. Therefore, providing reliable, robust systems for recovering UAV&#39;s has significant benefits. The capture mechanism  100  with deployable flaps and using the wing root as a guide for the near-vertical towline  102 , among other features of the present disclosure described herein, provide such enhanced reliability and robustness and in a simpler recovery process. 
     As further shown in  FIG.  1   , the capture mechanism  100  may be coupled with or integrally formed with a portion of the target aircraft T, such as the fuselage F as shown. The target aircraft T may be traveling in a horizontal direction. The direction of travel is indicated by arrow A T . The capture mechanism  100  may be configured to capture the towline  102  tethered to the host aircraft H while traveling in a horizontal direction, indicated by arrow A H , which may be the same or similar direction as the direction A T  of the target aircraft T. “Horizontal” as used herein has its usual and customary meaning and includes, without limitation, directions perpendicular to the direction of gravity, and directions that are approximately perpendicular to the direction of gravity, for example within +/−5 degrees, +/−10 degrees, +/−20 degrees, or +/−30 degrees of horizontal. The host and target aircraft H, T may be in horizontal or forward flight, and includes any aircraft or flying machine intended to fly horizontal. In some embodiments, the host aircraft H and/or target aircraft T may be flying only vertically, both horizontally and vertically, or they may be stationary in-flight without horizontal or vertical movement. 
     The target aircraft T in any of the embodiments disclosed herein may be any suitable or desired aerial vehicle. For example and without limitation, the target aircraft T shown in  FIGS.  1  and  2 A- 2 K  may be a Sparrowhawk Small Unmanned Aircraft System (SUAS), by General Atomics Aeronautical Systems, Inc. In other embodiments disclosed herein, the target aircraft T may be any suitable or desired vertical lift aircraft, or any other suitable or desired manned or unmanned aircraft. The host aircraft H may be an MQ-9 or other aircraft. The target aircraft T may have a deployed-wing wingspan of between 2 to 75 feet (ft), between 3 and 50 ft, between 4 and 25 ft, or between 5 and 15 ft. The target aircraft T may have a length of between 3 and 50 ft, between 3 and 25 ft, between 3 and 15 ft, or between 3 and 10 ft. The target aircraft T may have a weight of between 
     In some embodiments, the host aircraft H may be include a hoist  110 . The hoist  110  may include a winch. The hoist  110  may have some or all of the same or similar features and/or functions as the hoist system  1300  described with respect to  FIGS.  8 A- 14   , and vice versa. The hoist  110  may be configured to pay out or release the towline  102  and may be configured to reel in the towline  102 , which may be done after the towline  102  has been captured by the target aircraft T. In this manner, the host aircraft H may tether the target aircraft T and move the target aircraft toward the host aircraft H. The hoist  110  may be attached to the fuselage and/or to the wing of the host aircraft H. In some embodiments, the hoist  110  may be an electric hoist. The host aircraft H may have some or all of the same or similar features and/or functions as the host aircraft  1100  described with respect to  FIGS.  8 A- 14   , and vice versa. 
     With reference to  FIG.  1   , the capture mechanism  100  may include a first movable portion  120  and second movable portion  122 , such as arms or flaps. The first and second movable portions  120 ,  122  may be configured to rotate or move between a first stowed position in which the movable portion is in a closed or stowed state, and a second deployed position in which the movable portion is in an open or extended position. In  FIG.  1   , the movable portions  120 ,  122  are shown in deployed positions. 
     The towline  102  is shown extended downward with a portion  142  of the towline  102  located between a space  140  defined by the movable portions  120 ,  122 . The towline  102  further extends through a wing root WR in front of the wing W and adjacent the fuselage F, which may be a region adjacent the aircraft, as further described. A fitting  103  is located on a distal end of the towline  102 , which may be at the end of the towline  102  as shown. In some embodiments, there may be some length of the towline  102  extending beyond, e.g. through and beyond, the fitting  102 . The wing root WR and movable portions  120 ,  122  may guide the towline into the space  140  to then stow the movable portions  120 ,  122  and thereby capture the fitting  103 , as further described. The fitting  103  may be spherical as shown, or other shapes, as further described herein for example with respect to  FIGS.  7 A- 7 H . 
     The movable portions  120 ,  122  may be elongated arms or flaps. The movable portions  120 ,  122  may be made of metal, composite, other suitable materials, or combinations thereof. The movable portions  120 ,  122  may each have a thickness that is less than a width or average width. The length of each movable portion  120 ,  122  may be greater than the width and/or thickness. The movable portions  120 ,  122  may have a variety of shapes, sizes, and configurations, such as prongs, poles, bars, members, or any other structure that may operate to secure the fitting  103  to the target aircraft T as described herein. 
     In some embodiments, the first and/or second movable portions  120 ,  122  may have a contour that is rounded. The contour of the movable portions  120 ,  122  may match a contour of the fuselage of the target aircraft T, for example to optimize the aerodynamics of the capture mechanism  100  and the target aircraft T when the first and second movable portions  120 ,  122  are in the closed position. The movable portions  120 ,  122  may be configured to reduce the aerodynamic drag of the capture mechanism  200  when the first and second movable portions  220 ,  222  are in the first and second positions. For example, the movable portions  120 ,  122  may be made from a thin sheet metal or other rigid material. 
     The movable portions  120 ,  122  may move between various positions. For example, as shown in  FIG.  2 F , the first movable portion  120  is shown in a first position where it is closed or stowed in line with the fuselage, and the second movable portion  122  is shown in the second position where it is open or deployed. In some embodiments, the first and second movable portions  120 ,  122  may be configured to move independently of one another—e.g., the first movable portion  120  may be moved independently of the second movable portion  122  and the second movable portion  122  may be moved independently of the first movable portion  120 . In some embodiments, first and second movable portions  120 ,  122  may be connected and/or configured to move simultaneously and/or equal amounts. In some embodiments, there may be three, four, or more movable portions. Further, the movable portions  120 ,  122  may move to any positions that are between the deployed and stowed positions, such as partially deployed positions, half-deployed positions, etc. 
     The capture mechanism  100  may have a first recess  130  (see  FIGS.  1 ,  2 F and  2 G ) configured to receive the first movable portion  120  therein when the first movable portion  120  is in the closed position. The capture mechanism  100  may have a second recess  132  (see  FIGS.  1 ,  2 F and  2 G ) configured to receive the second movable portion  122  therein when the second movable portion  122  is in the closed position. The recesses  130 ,  132  may be different portions of one single, larger recess. The recesses  130 ,  132  may be openings or spaces in the fuselage F. 
     The capture mechanism  100  may have or define a cavity  131 , as shown for example in  FIG.  2 G . The cavity  131  may be located underneath the stowed movable portions  120 ,  122 . The cavity may be an open or empty space which receives the fitting  103  and part of the towline  102 . The movable portions  120 ,  122  in the stowed positions close over the cavity  131  with the fitting  103  and part of the towline  102  therein to secure to the towline  102  to the target aircraft T. The recesses  130 ,  132  may form an outer portion of the cavity  131 . 
     As shown in  FIG.  2 F , the first movable portion  120  may have a straight leading or forward edge  120   a  and an opposite aft or trailing edge  120   b . The first movable portion  120  may have a lower or outer edge  120   d  at a distal end of the first movable portion  120 . The first movable portion  120  may have a rearward edge  120   c , which may be angled as shown. The rearward edge  120   c  may be adjacent to the aft or trailing edge  120   b . The rearward edge  120   c  may extend from the outer edge  120   d  to the aft edge  120   b . The rearward edge  120   c  may be configured to guide or bias the towline  102  to a space  140  (also referred to as an opening or a gap) between the first and second movable portions  120 ,  122 . The second movable portion  122  may have a leading edge  122   a  and an opposite, straight aft or trailing edge  122   b . An angled forward edge  122   c  may extend from the leading edge  122   a  to a lower or outer edge  122   d . The angled rearward edge  120   c  of the first movable portion and the angled forward edge  122   c  of the second movable portion  122  may face each other and partially define an outer receiving portion of the opening  140 . The opening  140  may thus decrease in width in the direction of the target aircraft T. The straight aft edge  120   b  of the first movable portion  120  and the straight leading edge  122   a  of the second movable portion  122  may face each other and partially define an inward securing portion of the opening  140 . The opening  140  may thus have a constant width between the straight aft edge  120   b  and the straight leading edge  122   a . The towline  102  may be guided into the decreasing width portion of the opening  140  and then into the constant width portion of the opening  140 , as further described. 
     With reference to  FIGS.  2 A- 2 K , sequential views of an embodiment of the recovery system  90  are shown illustrating a method of capturing the target aircraft T having the capture mechanism  100  with the host aircraft H. As further described, in some embodiments, a method for in-flight recovery of the target aircraft T by the host aircraft H during forward flight may include, for example, deploying the towline  102  downward and away from the host aircraft H, receiving a vertically-oriented portion of the towline  102  into the wing root WR of the target aircraft T, deploying first and second movable portions  120 ,  122  of the target aircraft T to deployed positions to define the opening  140 , maneuvering the target aircraft T to move the capture mechanism  100  toward the towline  102 , guiding the towline  102  into the opening  140 , guiding the fitting  103  toward undersides of the deployed movable portions  120 ,  122 , stowing the movable portions  120 ,  122  to capture the fitting  103 , retracting the towline  102  toward the host aircraft H to direct the target aircraft T toward the host aircraft H, and/or securing the target aircraft T with the host aircraft H. 
     As shown in  FIG.  2 A , the target aircraft T may be maneuvered into an optimal position relative to the host aircraft H, and/or vice versa. The target aircraft T may be below and behind the host aircraft H. The target aircraft T may be laterally in line with the host aircraft H (with respect to directions into and out of the plane of the figure as oriented), or the target aircraft T may be laterally offset from the host aircraft H. The towline  102  may be deployed from the host aircraft H either prior to or after relative positioning of the aircraft H, T. 
     The towline  102  or portion or thereof, such as a distal end containing the fitting  103 , may be oriented vertically or near vertical. “Vertical” as used herein has its usual and customary meaning and includes without limitation a direction aligned with the direction of gravity. In some embodiments, “vertical” may refer to a direction perpendicular to a horizontal component of travel of the host and/or target aircraft H, T. The towline  102  may form an angle B with the vertical direction V, as shown in  FIG.  1   . In some embodiments, the portion of the towline  102  adjacent to or otherwise near the fitting  103 , such as any portions that would interact with the capture mechanism  100 , may form the angle B. The angle B may be less than 5 degrees, less than 10 degrees, less than 15 degrees, less than 20 degrees, less than 25 degrees, less than 30 degrees, less than 35 degrees, less than 40 degrees, or less than 45 degrees off the vertical direction V. In some embodiments, the towline  102  in free space (e.g. prior to contact with the target aircraft T) may be angled more than 30 degrees, or more than 45 degrees, and then form the angle B in response to contacting the wing and/or fuselage of the target aircraft. The towline  102  may thus form the angle B immediately prior to the towline  102  entering the space defined between the moveable portions. 
     As shown in  FIG.  2 B , the towline  102  extends through the wing root WR of the target aircraft T. As the target aircraft T is maneuvered, the towline  102  may be directed along the fuselage F and/or the wing W of the target aircraft T toward the wing root WR. As used herein, the “wing root WR” may include a region of the target aircraft T where the leading or trailing edge of the wing W intersects the fuselage F. This region is not limited to the surfaces of the wing W and fuselage F, and includes space adjacent to these surfaces extending forward from the wing W and laterally outward away from the fuselage F. The wing root WR may include a triangular region, defined between the nose of the aircraft, the outer tip of the wing, and the intersection of the fuselage and leading edge of the wing. The target aircraft T may be maneuvered relative to the towline  102  so that the towline  102  makes contact directly at the wing root WR of the target aircraft T without contacting the wing W or the fuselage F of the target aircraft T. 
     As shown in  FIG.  2 C , the target aircraft T may be maneuvered toward the towline  102  to cause the towline  102  to contact the target aircraft T along the wing W of the target aircraft T and/or the fuselage F of the target aircraft T. The towline T may make some contact with the wing W and/or fuselage F of the target aircraft T before the towline  102  is captured by the capture mechanism  100  of the target aircraft. In some embodiments, the target aircraft T may be maneuvered toward the towline  102  to bring the towline  102  in proximity with the wing W or the fuselage F of the target aircraft T, without necessarily having the towline  102  make contact with the fuselage F or the wing W of the target aircraft T. For instance, the recovery system  90  may use a natural funneling effect to cause the towline  102  to move toward the wing root WR of the target aircraft T, which may be due to contact with the wing W and/or fuselage F, and/or due to aerodynamic forces acting on the towline  102  and/or fitting  103 . The leading edge of wing W and side of fuselage F may create and/or enhance an airflow funnel and/or reduced pressure zone that may guide or bias the towline  102  toward the wing root WR and/or toward the fuselage F. 
     With reference to  FIGS.  2 C- 2 E , in some embodiments, the target aircraft T may be maneuvered such that, once the towline  102  reaches the wing root WR and/or with the towline  102  located within the opening  140  as further described, the flight path of the target aircraft T may be altered. For example and without limitation, the target aircraft T may be maneuvered to roll toward the towline  102 , yaw toward the towline  102 , and/or decrease altitude so that the fitting  103  is brought into proximity with the capture mechanism  100 . In some embodiments, at a certain proximity from the towline  102 , the target aircraft T may roll, maneuver laterally toward the towline  102 , and/or maneuver vertically up or down to bring the towline  102  and/or fitting  103  into proximity with the capture mechanism  100 . The first and second movable portions  120 ,  122  may be in a stowed position during these maneuvers. In some embodiments, the target aircraft T may maneuver laterally toward the towline  102  a distance of five feet or less, ten feet or less, fifteen feet or less, twenty feet or less, twenty-five feet or less, or thirty feet or less. The target aircraft T may lower relative to the towline  102 , e.g. decrease the target aircraft T&#39;s altitude if the towline  102  is vertically stationary, by one foot or less, two feet or less, three feet or less, four feet or less, five feet or less, six feet or less, seven feet or less, eight feet or less, nine feet or less, ten feet or less, fifteen feet or less, or twenty feet or less. The target aircraft T may roll, i.e. rotate along its longitudinal axis, toward the towline  102  an angular amount, which may be five degrees or less, ten degrees or less, fifteen degrees or less, or twenty degrees or less. This rotation may be relative to a current roll orientation of the target aircraft T, or relative to the horizon. 
     In any embodiments of the recovery systems disclosed herein, the target aircraft T may approach aft of and to the lateral side of the towline  102 , such as from the right of the towline  102  as shown. For capture mechanisms that open to the right side of the target aircraft T, the target aircraft T may approach from the aft and left side of the towline  102 . Looking down at the target aircraft T, for instance as shown in  FIG.  2 D , the target aircraft T may be moved at an angle toward the towline  102 , such as at a forty-five degree angle or an approximately a forty-five degree angle relative to the towline  102 . In some embodiments, the target aircraft T may be maneuvered toward the towline  102  at a vertical distance of approximately ten to one hundred feet, twenty to eighty feet, thirty to fifty feet, or forty feet below the host aircraft H.  FIG.  2 B  shows the target aircraft T nearing contact with the towline  102 . In some embodiments, visual navigation by the remote controller or autonomous flight system of the target aircraft T may be used to assist in the navigation and/or maneuvering of the target aircraft T relative to the towline  102  once the target aircraft T is in close proximity with the towline  102 , for example and without limitation, when the target aircraft T is within ten feet or approximately ten feet of the towline  102 , or within five feet or approximately five feet of the towline, or within five to twenty feet of the towline  102 . 
     As shown in  FIG.  2 F , in some embodiments, with the towline  102  either moving along the leading edge of the wing W toward the wing root WR, and/or along the fuselage F toward the wing root WR, and/or in contact with or in proximity of the wing root WR, the second movable portion  122  may be moved to or toward the open or deployed position. The second movable portion  122  may be deployed prior to the towline  102  being deployed and/or being near the target aircraft T. The second movable portion  122  may be located aft of the first movable portion  120 . The second movable portion  122  may be positioned on the target aircraft T and configured so that a leading or forward edge  122   a  of the second movable portion  122  will be aft of the towline  102  during the capture operation, e.g., when the towline  102  is in contact with or proximal to the wing root WR, or as the towline  102  is moving along the leading edge of the wing W of the target aircraft T. In this configuration, the towline  102  may be captured forward of the second movable portion  122  so that the capture mechanism  100  may capture the towline  102  between the first and second movable portions  120 ,  122 . 
     The towline  102  may be guided into the opening  140 , such as a gap or space, defined by and located between the first and second movable portions  120 ,  122 , as the first movable portion  120  is moved to or toward the open position, as shown in  FIG.  2 E . In some embodiments, the first movable portion  120  may already be deployed prior to movement of the towline toward the opening  140 . The opening  140  may have a decreasing width from an outer edge of the movable portions  120 ,  122  in the inward direction toward the aircraft T between the angled portion  120   c  of the first movable portion  120  and the outward part of the leading edge  122   a  of the second movable portion  122 . This may create a funnel-shape between the movable portions  120 ,  122 . The opening  140  may then have a constant width section between the trailing edge  120   b  of the first movable portion  120  and the inward part of the leading edge  122   a  of the second movable portion. The towline  102  may be received into the decreasing width portion of the opening  140  and then into the constant width portion of the opening  140 . 
     The opening  140  may have an inner-most endpoint  141 , which may be a region of the opening  140 , that limits further lateral travel of the towline  102 . The endpoint  141  may be aligned with a longitudinal axis of the aircraft T, for example located directly over such axis, such that this endpoint  141  is near the middle of the fuselage F as viewed from the top. In some embodiments, this endpoint  141  may be aligned with the center of gravity of the target aircraft T. In some embodiments, the opening  140  may be forward or aft of the center of gravity of the target aircraft T. In some embodiments, the opening  140  may be slightly forward of the center of gravity of the target aircraft T to create a passively stable towed body once the wings are folded or moved to a collapsed state (if the wings are folded or moved to a collapsed state) and/or the engine of the target aircraft is shut down. In some embodiments, the opening  140  may be forward or aft of the center of gravity of the target aircraft T by a particular percentage of the overall longitudinal length of the aircraft, for example by from 2% or less, less than 5%, less than 10%, less than 15% or less than 20% of the length of the aircraft. The opening  140  may have other configurations, such as a uniform width, a changing width, a decreasing width, an increasing width, or combinations thereof. 
     As shown in  FIG.  2 G , once the target aircraft T and/or towline  102  have been maneuvered so that the towline  102  is positioned forward of and adjacent to the forward edge  122   a  of the second movable portion  122 , the first movable portion  120  may be deployed to or toward the open position so that the towline  102  is positioned between the aft edge  120   b  of the first movable portion  120  and the forward edge  122   a  of the second movable portion  122 . With the towline  102  positioned between the aft edge  120   b  of the first movable portion  120  and the forward edge  122   a  of the second movable portion  122 , the towline  102  and/or target aircraft T may move such that the towline  102  moves vertically upward relative to the target aircraft T, which movement may be toward the host aircraft H, and is drawn upward through the opening  140  of the capture mechanism  100 . The fitting  103  or other limiting object fixed to the towline  102  at a particular position on the towline  102  may thus be moved into contact with the capture mechanism  100 , for example and without limitation, moved into contact with a lower surface of the first and second movable portions  120 ,  122 . 
     In some embodiments, the capture mechanism  100  and the fitting  103  may be configured such that the fitting  103  has a width that is larger than a width of an inner section of the opening  140 . This inner section may be a portion of the opening  140  that has a constant width, or that otherwise has a width smaller than the width of the fitting  103 . The width of the fitting  103  may be larger than a perpendicular distance between the aft edge of the first movable portion  120  and the forward edge of the second movable portion  122 . This inner section of the opening  140  may be at or near a base of the first and second movable portions  120 ,  122 . The inner section may be configured such that the fitting  103  cannot vertically pass through the opening  140  between the first and second movable portions  120 ,  122  as the towline  102  is moved upwardly through the inner section of the opening  140  between the first and second movable portions  120 ,  122  when the first and second movable portions  120 ,  122  are in the stowed or deployed positions. In this manner, the capture mechanism  100  may be used to capture or secure the towline  102  to the target aircraft T. 
     In some embodiments, the target aircraft T may maneuver to locate the towline  102  within the opening  140 , into the inner section of the opening  140 , and/or into the endpoint  141  of the opening  140 . The target aircraft T may roll, yaw, pitch, etc. as previously described. 
     As shown in  FIG.  2 H , with the fitting  103  located in the inner section and/or at the endpoint  141  of the opening  140 , the first and second movable portions  120 ,  122  may be moved, e.g. simultaneously, toward their respective stowed positions to prevent the towline  102  and/or the fitting  103  from escaping the fuselage F of the target aircraft T or otherwise moving out of engagement with the capture mechanism  100 . The towline  102  may extend from the endpoint  141  of the opening  140 , or from the inner section of the opening  140 . 
     As shown in  FIGS.  21  and  2 J , some embodiments of the target aircraft T may be configured to take a passive towed body configuration. For example, the wings W may move or rotate to a stowed position. In this example, the wings W move in line with the fuselage F of the target aircraft T. Further details of towed body configurations of the target aircraft are shown in and described with respect to  FIGS.  9 A- 9 D . 
     As shown in  FIG.  2 K , the towline  102  may be reeled in by a hoist system having a winch to pull the target aircraft T toward the host aircraft H. Once the towline  102  is retracted, the target aircraft T may be securely attached to or secured by the host aircraft H. For example, the target aircraft T may attach to a pylon of the host aircraft H. Further details of various embodiments of hoist systems and securement features are shown in and described with respect to  FIGS.  8 A- 14   . Optionally, the target aircraft T may also be deployable from the host aircraft H before and/or after recovery. The recovery or deployment may occur during any phase of flight. The recovery may occur during forward flight, ascending or descending flight, takeoff, landing, or other phases. 
       FIG.  3    depicts another embodiment of a system  190  for recovery of a target aircraft T having a capture mechanism  200 . The recovery system  190  may have the same features and/or functions as the recovery system  90 , and vice versa. For example, the capture mechanism  200  may be coupled with a fuselage F of a target aircraft T and may be configured to capture a towline  202  tethered to a host vehicle (not shown). The capture mechanism  200  may include a first movable portion  220  and second movable portion  222 . The first movable portion  220  may have a leading edge  220   a  and a trailing edge  220   b , and the second movable portion  222  may have a leading edge  222   a  and a trailing edge  222   b . The first and second movable portions  220 ,  222  may be configured to rotate or move between a first, closed or stowed position and a second, open or extended position. For example and without limitation,  FIG.  3    shows the first and second movable portions  220 ,  222  in a second, open position. The capture mechanism  200  may have a first recess  230  configured to receive the first movable portion  220  therein when the first movable portion  220  is in the closed position, and a second recess  232  configured to receive the second movable portion  222  therein when the second movable portion  222  is in the closed position, to optimize the aerodynamics of the capture mechanism. 
     Further, the capture mechanism  190  may include a catch  242  configured to receive the fitting  203 . The catch  242  may be located within the recess  230  and/or recess  232 . The catch may be a device the secures, for example grabs, the fitting  203 . In some embodiments, the catch  242  may be a round opening in the cavity or recesses configured to receive the fitting  203  therein as the movable portions  220 ,  222  close and move the fitting  203  through and/or into the catch  242 . 
       FIGS.  4 A- 4 D  depict sequential views of another embodiment of a recovery system  290  for recovery of a target aircraft T having a capture mechanism  300 . The recovery system  290  may have any of the same features and/or functions as the recovery system  90  or  190 , and vice versa. For example, the capture mechanism  300  may be coupled with a fuselage F of a target aircraft T and may be configured to capture a towline  302  tethered to a host vehicle (not shown). The capture mechanism  300  may include a first movable portion  320  and second movable portion  322 . The first movable portion  320  may have a leading edge  320   a  and a trailing edge  320   b , and the second movable portion  322  may have a leading edge  322   a  and a trailing edge  322   b . The first and second movable portions  320 ,  322  may be configured to rotate or move between a first, closed or stowed position and a second, open or extended position. For example and without limitation,  FIG.  4 B  shows the first and second movable portions  320 ,  322  in a second, open position. The capture mechanism  300  may have a first recess  330  configured to receive the first movable portion  320  therein when the first movable portion  320  is in the closed position, and a second recess  332  configured to receive the second movable portion  322  therein when the second movable portion  322  is in the closed position. 
     Further, the first and/or a second movable portions  320 ,  322  may have a segmented “ski” shape. The movable portions  320 ,  322  may be elongated members with multiple segments to match the contour of the fuselage F and provide a wider outer opening  340  for the towline  302 . The inner segments of each movable portion  320 ,  322  may be spaced to define a constant width opening therebetween. A second outward segment adjacent the inner segment of each movable portion  320 ,  322  may angle away from each other and have an increasing width therebetween in a direction away from the base of the movable portions  320 ,  322 . A third outer segment adjacent the second segment of each movable portion  320 ,  322  may angle outward even more than the second segments, and have an increasing width therebetween that increases at a faster rate in an outer direction as compared to the distance between the second segments. This configuration may create a larger outermost width of an opening  340  located between outer endpoints of the movable portions  320 ,  322  to increase reliability of receiving the towline  302  between the movable portions  320 ,  322  and into the inner section of the opening  340 . 
       FIGS.  5 A- 5 F  depict sequential views of another embodiment of a recovery system  390  for recovery of a target aircraft T having a capture mechanism  400 . The recovery system  390  may have any of the features and/or functions as the recovery systems  90 ,  190 , or  290 , and vice versa. For example, the capture mechanism  400  may be coupled with a fuselage F of the target aircraft T and may be configured to capture a towline  402  tethered to a host vehicle (not shown). The capture mechanism  400  may include a first movable portion  420  and second movable portion  422 . The first movable portion  420  may have a leading edge  420   a  and a trailing edge  420   b , and the second movable portion  422  may have a leading edge  422   a  and a trailing edge  422   b . The first and second movable portions  420 ,  422  may be configured to rotate or move between a stowed position and a deployed position. The capture mechanism  400  may have a first recess  430  configured to receive the first movable portion  420  therein when the first movable portion  420  is in the closed position, and a second recess  432  configured to receive the second movable portion  422  therein when the second movable portion  422  is in the closed position. 
     Further, the first and second movable portions  420 ,  422  may be integral and move together. The movable portions  420 ,  422  may have a single shared base  419  that rotates outward, and include two prongs  421 ,  423  respectively extending outwardly from the base  419 . The base  419  may rotate about an axis that is located on an opposite side, for example right side, of the fuselage F as the side from which the towline  402  is incoming, for example the left side. The base  419  and/or movable portions  420 ,  422  may have a rounded, e.g. circular or elliptical, contour to match the fuselage cross-sectional shape. An opening  440  may be defined between the two prongs  421 ,  423  having a width that decreases in an inward direction toward the aircraft T to a smaller width inner section, which may have a constant width. A fitting  403  may have an elongated shape, such as cylindrical and, in some embodiments, have rounded edges near the longitudinal ends of the fitting  403 , as shown. In any embodiments disclosed herein, the fitting  403  can be cylindrical in shape, as shown in  FIGS.  5 A- 5 E , but may be shorter or longer in length than shown. For example and without limitation, the fitting  403  of any embodiments can have more of an elongated pill shape. The fitting  403  may be long enough to not fit through the inner section of the opening  440 . The fitting  403  may be rounded to match a rounded contour of the underside of the movable portions  420 ,  422 , for example to self-center itself underneath the movable portions  420 ,  422  in the stowed position. 
       FIGS.  6 A- 6 F  depict sequential views of another embodiment of a system  490  for recovery of a target aircraft T having a capture mechanism  500 . The recovery system  490  may have any of the features and/or functions as the recovery systems  90 ,  190 ,  290  or  390 , and vice versa. For example, the capture mechanism  500  may be coupled with a fuselage F of the target aircraft T and may be configured to capture a towline  502  tethered to a host vehicle (not shown). The capture mechanism  500  may include a first movable portion  520  and second movable portion  522 . The first movable portion  520  may have a leading edge  520   a  and a trailing edge  520   b , and the second movable portion  522  may have a leading edge  522   a  and a trailing edge  522   b . The first and second movable portions  520 ,  522  may be configured to rotate or move between a stowed position and a deployed position. 
     Further, the wing root WR may be a region located aft of the wing, as shown. This region may include space aft of the wing and laterally to the left side of the fuselage. The region may be bounded by the intersection of the trailing edge of the wing and the fuselage, the tail, and the outer tip of the left wing. Thus, the towline  502  may be located aft of the wing and/or to the left of the fuselage. The target aircraft T may slow its speed while maneuvering to have the towline  502  located within this aft wing root WR. Additionally, the first and second movable portions  520 ,  522  may be separate and configured to move independently of one another or to move simultaneously and equally depending on the desire of the operator or of the autonomous system. For example, the towline  502  may be at an angle or position where only one, or both, movable portions  520 ,  522  should be deployed, and the mechanism can be operated accordingly. The movable portions  520 ,  522  may also have a length that, when deployed, extends an outermost tip of the movable portions  520 ,  522  farther outward to allow for capture of the towline  502  located farther from the fuselage F. For example, the movable portions  520 ,  522  may deploy to locate the outermost tips beyond an outer, lateral side of the fuselage F, and/or beyond the intersection of the wing W and fuselage F, and/or beyond 5%, beyond 10%, beyond 15%, or beyond 20% or more of the wingspan as measured between opposite tips of the wings W. 
     The following details apply to any recovery system and any capture mechanism embodiments disclosed herein. In some embodiments, servos, electric motors (high torque geared motors), linear or rotational actuators (for example and without limitation, screw driven linear actuators), hydraulic, pneumatic, and/or other actuation mechanisms may be used to move the first and second movable portions between the first and second positions. For example and without limitation, a first servo, motor, and/or actuator may be configured to rotate a shaft or axle that the first movable portion is coupled with to rotate the first movable portion between the first and second positions. A second servo, motor, and/or actuator may be configured to rotate a shaft or axle that the second movable portion is coupled with to rotate the second movable portion between the first and second positions. The first and second servo, motor, and/or actuators may be independently controlled. In some embodiments, a single servo, motor, actuator, and/or combination thereof may be used to move both the first and second movable portions. 
     In some embodiments, the first and second movable portions may be integrally formed—e.g., may be formed as a single structure, and/or may be separately formed and rigidly connected. In this arrangement, the capture mechanism may be configured such that the first and second movable portions move as a single unit, such that they both moved between the first, close position and a second, open position simultaneously. 
     In some embodiments, the first and second movable portions may be configured to rotate around one or two shafts or axes. For example and without limitation, embodiments wherein the first and second movable portions are connected, made from a single piece, or otherwise configured to move together and simultaneously, the first and second movable portions may rotate about a single shaft or axis. 
     In some embodiments, the shaft or axis of rotation that the first and second movable portions may be configured to move or rotate about may be located on the same side of the fuselage as the target wing root toward which the towline will be directed. In some embodiments, the shaft or axis of rotation that the first and second movable portions may be configured to move or rotate about may be located on the opposite side of the fuselage as the target wing root toward which the towline will be directed, as in the embodiment of the capture mechanism  400  shown in  FIGS.  5 A- 5 F , or on an upper portion of the fuselage, as in the embodiment of the capture mechanism  100  shown in  FIGS.  1 - 2 K . 
     In any embodiments disclosed herein, the capture mechanism and/or fuselage of the target aircraft T may be configured to have a recess or chamber sized and positioned to receive the fitting therein so that the fitting does not prevent or inhibit the moving of the capture mechanism to the second, closed state. For example and without limitation, any embodiments of the capture mechanism or the fuselage of the target aircraft T may have a recess, chamber, or space formed therein that is sized and configured to receive the fitting therein as the towline is being advanced into the space or recess between the first and second movable portions of the capture mechanism. In some embodiments, the recess or space configured to receive the fitting may be generally aligned with the space or recess between the first and second movable portions of the capture mechanism since, in some embodiments, the capture mechanism may be configured to bias the towline and the fitting toward the space between the first and second movable portions of the capture mechanism. In some embodiments, the recess or space configured to receive the fitting may have sloping side portions and/or be configured to bias the fitting toward a middle of the recess or space, or otherwise facilitate the movement of the fitting into the recess or space. 
     Additionally, in some embodiments, though not required, the capture mechanism may have latch mechanisms or other securing mechanisms to selectively latch or secure the first and second movable portions in the closed position to prevent the first and second movable portions from moving toward the open position as the target aircraft T is being lifted toward the host aircraft H (e.g., as an upward force is exerted on the first and second movable portions from the towline and fitting). The latch mechanisms in some embodiments may be electronically controlled so that the latch mechanisms may be released or opened before the first and second movable portions are desired to be moved to the open position. In some embodiments, the latch mechanism may include sliding pins and complementary receiving features. 
     In any embodiments disclosed herein, though not required, the capture mechanism can be configured to couple with the fitting or couple with the towline so that the towline extends from the target aircraft T at an approximately lateral center of the target aircraft so that the force exerted on the target aircraft by the towline as the towline is being withdrawn is approximately at a lateral center of the target aircraft. In some embodiments, the capture mechanism may be configured to bias the fitting or fitting, or the towline so that the towline extends from the target aircraft T at an approximately lateral center of the target aircraft so that the force exerted on the target aircraft by the towline as the towline is being withdrawn is approximately at a lateral center of the target aircraft. In other embodiments, the capture mechanism may be configured to bias the fitting or fitting or the towline so that the towline extends from the target aircraft T offset from the lateral center of the target aircraft. In these embodiments, the target aircraft may be configured to counteract any off-center force applied to the target aircraft T by the towline as the towline is being withdrawn toward the host aircraft. 
     In any embodiments of the systems for recovering a target aircraft disclosed herein, including without limitation the embodiments of the systems  90 ,  190 ,  290 ,  390 , and  490 , the towline may be a simple, uniform towline and may include a fitting (such as, without limitation, fitting  103 ,  203 ,  303 ,  403 ,  503 ) positioned along a length thereof. The towline of any embodiment herein may have a width between 0.1 to 1.0 inch (in), or between 0.125 to 0.75 in, or between 0.125 to 0.625 in, or between 0.25 to 0.5 in. The towline maybe steel, stainless steel, improved plow steel, aluminum, synthetic such as nylon, aramid, dyneema or any other material suitable for extended outdoor use in moderately harsh environments. The towline may have a core that is strand, fiber, or independent wire rope core (IWRC). The towline finish may have a corrosion resistant coating (e.g. zinc, nickel, galvanized), or be unfinished. The towline may be uncoated, or coated for abrasion, chemical and/or weather resistance. The towline may have a breaking strength of between 1,000 and 10,000 pound-force (lbf), or between 1,500 and 7,500 lbf, or between 2,000 and 5,000 lbf. 
     As described above, the fitting of any embodiments of the system for recovering a target aircraft disclosed herein may be configured to provide a stop on the towline, when the fitting engaged with the capture mechanism, to prevent further movement of the towline in at least an upward direction relative to the capture mechanism. Further, at least when the capture mechanism is in a closed position, the fitting may be captured by the capture mechanism and be prevented from moving out of contact with or away from the capture mechanism. In some embodiments, all or a portion of the fitting may be sufficiently rigid so as to remain substantially undeformed or uncollapsed during any recovery operation. For example and without limitation, all or a portion of the fitting may be rigid enough to remain substantially undeformed and uncollapsed when the fitting has been captured by the capture mechanism, when the capture mechanism moves to the second, closed state, and/or when the target aircraft is being withdrawn toward the host aircraft during a recovery operation by withdrawing the towline that the fitting is coupled with. 
     In any embodiments, the fitting may have any desirable weight and size, and may have any desired shape. For example with without limitation, in any embodiments, the fitting may have a spherical shape, a conical shape, an oblong shape, or any other desired shape, as further described. 
       FIGS.  7 A- 7 H  illustrate different embodiments of fittings that may be used with or as part of any embodiments of the recovery systems disclosed herein. Any of the fittings shown in  FIGS.  7 A- 7 H  may be used with any of the various recovery systems described herein. Further, any features of one of the fittings may be applied to any of the other fittings. 
       FIG.  7 A  shows an embodiment of a fitting  1000  coupled with or attached to a towline  1002 . The fitting  1000  may have a distal portion  1004  (also referred to herein as a body portion) that may be spherical and a proximal portion  1006  (also referred to herein as a leading portion) that may be generally cylindrical. The distal portion  1004  may be solid, hollow, thin walled, or combinations thereof. The proximal portion  1006  may be coupled with the distal portion  1004  or may be integrally formed. A proximal end of the proximal portion  1006  may be pointed or tapered. The proximal portion  1006  may extend through the opening formed by the flaps of the capture mechanism. The distal portion  1004  may be too large to fit through the opening, such that the flaps contact and engage the distal portion to move the fitting  1000  into the recess of the fuselage when the flaps move from the deployed position to the closed position. 
     A diameter or size of the proximal portion  1006  may be less than a maximum diameter or size of the distal portion  1004 , such as, without limitation, at a distal end of the distal portion  1004 . In some embodiments, the diameter or size of the proximal portion  1006  may be 10%, less than 10%, or approximately 10% of a size or diameter of the distal portion, or from 10% to 40% or approximately 40% of a maximum size or diameter of the distal portion  1004 . In some embodiments, the spherical portion of the fitting  1000  may have a width, e.g. diameter, from 1 to 10 inches (in), from 2 to 8 in, from 3 to 7 in, from 4 to 6 in, or about 5 in. The fitting  1000  may weigh from 1 to 20 pounds (lbs), from 1 to 15 lbs, from 2 to 10 lbs, or from 4 to 8 lbs. These width and weight features may apply to any of the embodiments of the fittings described herein. 
     In some embodiments, a maximum diameter or size of the distal portion  1004  of the fitting  1000  may be many times greater than a diameter of the towline  1002 , for example and without limitation, at least fifty times greater than a diameter of the towline, or from twenty times greater to eighty times greater than a diameter of the towline, or from thirty times greater to sixty times greater than a diameter of the towline. 
       FIG.  7 B  is a side view of another embodiment of a fitting  1010  having a tear-drop shape. The fitting  1010  may increase in width from a top to a bottom portion and then decrease in width. The contour may be smooth, with a conical upper portion and spherical lower portion. The conical upper portion may extend through the opening of the flaps and the width of the bottom portion may prevent the fitting from traversing the opening completely. 
       FIG.  7 C  is a side of another embodiment of a fitting  1015  having an arrow shape. The fitting  1015  may have a forward angular portion  1016  attached via an elongated member  1017  to an aft feathered portion  1018 . The angular portion  1016  may form a vertex pointing forward and increase in width in the aft direction. The angular portion  1016  may be planar or three-dimensional, e.g. a conical shape. The feathered portion  1018  may have various protrusion extending outward and aft, and may be planar or three-dimensional. In use, the towline may attach along the member  1017 , with the towline extending through the opening of the flaps, and the fitting  1015  engaging with the underside of the flaps. 
       FIG.  7 D  is a side view of another embodiment of a fitting  1020  having a flying saucer shape. The fitting  1020  may have upper and lower portions  1021 ,  1022  that have spherical contours bulging upward and downward from a ring-like middle portion  1023 . The middle portion  1023  may extend radially farther than the upper and lower portions  1021 ,  1022 . The upper and lower portions  1021 ,  1022  may be symmetric about the middle portion  1023 . 
       FIGS.  7 E and  7 F  are front and side views respectively of a fitting  1025  having a blended-wing body shape with dihedral wings  1027  attached on both sides of a center portion  1026 . The wings  1027  may extend upward from the center portion  1026 . The center portion  1026  may have an airfoil profile, for example a rounded, blunt forward end that tapers to a point or reduced height at an aft end, as shown in  FIG.  7 F . In use, the towline may extend through the opening of the flaps, with the wings  1027  preventing the fitting  1025  from completely traversing the opening. 
       FIGS.  7 G and  7 H  are front and side views respectively of a fitting  1030  having a blended-wing body shape with anhedral wings  1027  attached on both sides of the center portion  1026 . The wings  1027  may extend downward from the center portion  1026 . In use, the towline may extend through the opening of the flaps, with the wings  1031  preventing the fitting  1030  from completely traversing the opening. 
       FIGS.  8 A- 8 C  are front, perspective, and top views respectively of a host aircraft  1100  in flight having multiple target aircrafts  1200  secured via hoist systems  1300 . The aircraft  1100  includes a right wing  1102 , a left wing  1104 , a central fuselage  1106 , and an inverted-V tail  1108 . The host aircraft  1100  may be unmanned, and it may be autonomously flown or remote controlled by a human operator. Other types and configurations of the aircraft  1100  may be used, and this is merely one example embodiment. 
     The hoist systems  1300  are attached to an underside of a respective wing  1102 ,  1104 . The hoist system  1300  may have some or all of the same or similar features and/or functions as the hoist  110  described with respect to  FIG.  1   , and vice versa. There may be fewer than or greater than one hoist system  1300  per wing. There may be zero, one, two, three, four, five, six or more hoist systems  1300  per wing. The hoist system  1300  in flight may deploy one or more towlines to capture a respective target aircraft  1200 , reel in the respective target aircraft  1200  toward the host aircraft  1100  by reeling in the respective towline, and secure the respective target aircraft  1200  to a respective hoist system  1300 , as further described herein. 
       FIGS.  9 A and  9 B  are top views of the target aircraft  1200  shown with the wings  1202 ,  1204  deployed and stowed, respectively.  FIGS.  9 C and  9 D  are front views of the target aircraft  1200  showing the wings  1202 ,  1204  deployed and stowed, respectively. The  1202 ,  1204  are rotatably attached to a center fuselage  1206  and may move from a deployed configuration having a larger width for horizontal flight to a stowed configuration having a smaller width for recovery by the host aircraft and hoist system. The target aircraft  1200  has a propeller  1207  shown schematically. The target aircraft  1200  may be propeller driven, or it may have a turbofan, turbojet, or other type engine. 
       FIG.  10    is a perspective view of the host aircraft  1100  recovering the target aircraft  1200  in flight via the towline  102  extending from the hoist system  1300 . The hoist system  1300  includes a pylon  1310  attached to an underside of the left wing  1104 . The other hoist systems  1300  are removed for clarity, but other hoist systems on either wing may be included. The pylon  1310  is a supporting structure made of metal, composite, or combinations thereof, that supports and protects the various components of the hoist system  1300 , as further described. 
       FIGS.  11 A- 11 C  are perspective, side, and front views respectively of the hoist system  1300  securing the target aircraft  1200  to the wing  1104 . The wing  1104  is removed in  FIG.  11 A  for clarity. The hoist system  1300  may be located to avoid interference with the wing flap  1105  and wing flap hinge  1109 . A clearance  1107  may exist between the pylon  1310  and the lowered flap  1105 , as shown most clearly in  FIG.  11 B . The side of the pylon  1310  may avoid interference with the wing flap hinge  1109 , as shown in  FIG.  11 C . 
     The hoist system  1300  includes forward and aft sway bars  1312 ,  1314  that extend outward and downward from a bottom end of the pylon  1310 . The sway bars  1312  surround an upper portion of the fuselage target aircraft  1200  for lateral stability of the target aircraft  1200  and for ensuring alignment of the target aircraft  1200  during the last phase of reeling in the target aircraft  1200 . In some embodiments, the sway bars  1312 ,  1314  may guide the target aircraft  1200  with stowed wings into position so that a securement mechanism, as further described, may engage with the target aircraft  1200 . The pylon  1310  and sway bars  1312 ,  1314  are further shown in, and described with respect to,  FIGS.  12 A- 12 D . 
     In  FIGS.  11 A- 11 C , the pylon  1310  is shown transparently for clarity purposes, to show components of the hoist system  1300  therein. The hoist system  1300  may include a motorized winch  1400 . The winch  1400  may be located in an aft section of the pylon  1310  relative to other components of the hoist system  1300 . The hoist system  1300  may include a latching system  1500  located forward of the winch  1400 . The towline  102  may extend from the winch  1400  to the latching system  1500  and to the target aircraft  1200 . The latching system  1500  may guide the towline  102  along a path. There may be a fleet pulley assembly  1510  through the towline  102  extends, a top sheave  1520  along which the towline  102  wraps around down through a latch housing  1530  located beneath the top sheave  1520 . Further details of the winch  1400  and latching system  1500  are described herein with respect to  FIGS.  13 A- 14   . The target aircraft  1200  may be secured with the hoist system  1300  with the center of gravity CG of the target aircraft  1200  located toward a forward portion of the pylon  1310 , as shown. The latch housing  1530  or other engaging features of the hoist system  1300 , as described herein, may be located generally above and in line with the center of gravity CG of the target aircraft  1200 . 
       FIGS.  12 A- 12 D  are front, side, cross-section, and bottom views of the pylon  1310 .  FIG.  12 C  is a cross-section, taken from  FIG.  12 B  along the line  12 C- 12 C, and includes a cross-sectional part of the target aircraft  1200  for illustration. The shape, size, configuration, etc. of the pylon  1310  is merely one example embodiment, and other variations of the pylon may be incorporated. 
     The pylon  1310  extends from a forward end  1321  to an aft end  1329 , each end having tapering profiles for aerodynamic efficiency. Opposing lateral sidewalls  1326 ,  1328  may increase in width from the forward end  1321  in the aft direction to a central portion  1323 , and then decrease in width from the central portion  1323  to the aft end  1329 . The sidewalls  1328  may have a maximum width at the central portion  1323 , which width may be sized based on size of the hoist system  1300  components therein, based on the width of the stowed target aircraft  1200 , and/or based on the configuration of the host aircraft wing  1104  and associated features of the host aircraft  1100 . The pylon  1310  may have a length of between 30 and 200 inches (in), between 45 and 90 in, between 55 and 80 in, or between 65 and 70 in. The pylon  1310  may have a width of between 5 and 100 in, between 10 and 50 in, or between 15 and 25 in. The pylon  1310  may have a height of between 5 and 100 in, between 10 and 50 in, or between 15 and 25 in. 
     The pylon  1310  may include an upper attachment portion  1325  for attaching the pylon  1310  to the wing. The upper attachment portion  1325  may have a smaller width than that between the sidewalls  1326 ,  1328 . There may be an upper side  1320  having a contour that matches that of the underside of the wing. The upper side  1320  may be an upper surface of A gap may exist between the upper side  1320  and the lower side of the wing, or there may not be a gap. The pylon  1310  may include a lower side  1322  having a contour that matches an upper portion of the fuselage of the target aircraft  1200 . A gap may or may not exist between the fuselage and the lower side  1322 . 
     The sway bars  1312 ,  1314  may be located on the lower side  1322  at forward portions of the pylon  1310  as shown, or in other locations. The forward sway bar  1312  may be located at or near a lower portion of the forward edge  1321 . The aft sway bar  1314  may be located at or near the central portion  1323  of the pylon  1310 . An opening  1313  in the lower side  1322  of the pylon  1310  may be located in between the sway bars  1312 ,  1314 . The towline may extend from the latching system  1550  through the opening  1313  and out to the target aircraft  1200 . 
     As shown in  FIG.  12 C , the sway bar  1312  may match the contour of the target aircraft  1200  fuselage. The sway bar  1312  may extend along the upper and side surfaces of the upper portion of the target aircraft  1200  fuselage after securing the target aircraft  1200  to the hoist system  1300 . Similar relationships may exist for the aft sway bar  1314  and a rearward portion of the fuselage of the target aircraft  1200 . 
       FIG.  13 A  is a perspective view of a schematic of part of the hoist system  1300 , showing the winch  1400 , fleet pulley assembly  1510 , and top sheave  1520  in isolation from other components.  FIG.  13 B  is a cross-section view taken from  FIG.  13 A  along the line  13 B- 13 B. 
     The winch  1400  includes a rotating drum  1402  around which the towline  102  is wrapped. The drum  1402  may be cylindrical. A motor  1404  rotates the drum  1402  to control the length of the towline  102  that is paid out from the host aircraft. The motor  1404  may be controlled based on desired length of towline  102 , based on speed of paying our or reeling in of the towline  102 , based on vertical position of the target aircraft  1200 , etc. The winch  1400  may have a width, height and depth no greater than 18 in, 12 in, and 16 in, respectively. 
     The towline  102  may extend through a movable cartridge  1406  at a forward portion of the winch  1400 . The cartridge  1406  may move axially along one or more axles  1408 . The cartridge  1406  may move in response to the relative lateral position of the towline  102  on the drum  1402 . As the towline  102  unwraps from the drum  1402  to pay out, the towline  102  may extend from various lateral locations of the drum  1402 . “Lateral” refers to a direction that is parallel to the axis of rotation  1401  of the drum  1402 , which axis may be perpendicular to a longitudinal axis of the host aircraft fuselage  1106 . 
     The cartridge  1406  may move such that the towline  102  portion located between the fleet pulley assembly  1510  and the drum  1402  may sweep out an angle  104  of at least ten degrees, at least twenty degrees, at least thirty degrees, at least forty degrees, at least fifty degrees, at least sixty degrees, at least seventy degrees, at least eighty degrees, or at least ninety degrees. In some embodiments, the angle  104  is sixty degrees or about sixty degrees. In some embodiments, the angle  104  is not symmetric about the towline  102 . As shown in  FIG.  13 B , the fleet pulley assembly  1510  may be located along a geometric reference line  1516  that is optimized for the pylon  1310  geometry. The line  1516  may be selected for example to allow the towline  102  to be at angle of about thirty degrees on one side but less than thirty degrees on the other side of the line  1516 . These are just examples and other configurations and angles may be used. 
     The fleet pully assembly  1510  may include a first pulley  1512  and a second pulley  1514  oriented generally horizontally and approximately vertically level with the outlet of the towline  102  at the cartridge  1406 . The pulleys  1512 ,  1514  may be wheels rotatable on a central axis and supported by a support structure within the pylon  1310 . The fleet pully assembly  1510  stabilizes the horizontal or lateral direction of the towline away from the cartridge  1406 . The pulleys  1512 ,  1514  may be positioned forward of the winch  1400  to prevent vertical separation of the towline  102  from the groove formed by the opposing pulleys  1512 ,  1514 . In some embodiments, other guides besides pulleys may be used, such as sheaves, stationary and lubricated rounded surfaces, etc. An aft-most portion of the fleet pully assembly  1510  may be located greater than 5 inches (in), greater than 6 in, greater than 7 in, greater than 8 in, greater than 9 in, or greater than 10 in forward of a forward-most portion of the winch. The sweep angle of the towline  102  may be with respect to this distance between the winch  1400  and fleet pulley assembly  1510 . The centers of rotation of the pulleys  1512 ,  1514  may be located about 9 to 11 in from a forward-most portion of the winch  1400 . Each of the pulleys  1512 ,  1514 , and/or the top sheave as further described, may have a diameter between 2 and 12 in, between 4 and 10 in, between 6 and 8 in, or 7 in. 
     The top sheave  1520  may be located forward of the fleet pulley assembly  1510 . The top sheave  1520  may guide the towline  102  in a downward direction as shown. The top sheave  1520  may be a rotating wheel. In some embodiments, the top sheave  1520  may be a stationary guide surface, or other type guide. 
       FIG.  14 A  is a perspective view of an embodiment of the latching system  1500 . The latching system  1500  may include fewer or more components than shown. The towline  102  wraps around the top sheave  1520  and extends down to a towline connector  1528 . The towline connector  1528  may define a channel through which the towline  102  extends. An upper opening of the towline connector  1528  may be located adjacent and below the top sheave  1520  to minimize the amount of towline  102  extending freely between the top sheave  1520  and the upper opening. The towline  102  may exit a lower opening in the towline connector  1528  to extend to the end fitting  103 . In some embodiments, the towline  102  may not extend through the towline connector  1528 . For example, the towline  102  may connect with the towline connector  1528 , which may connect with or be integral to the end fitting  103 , as further described. 
     In some embodiments, the towline connector  1528  may be used to couple the towline  102  with the end fitting  103 . In some embodiments, the towline connector  1528  may be integrally formed with the end fitting  103  or may be separately formed and attached to or otherwise coupled with the end fitting  103 . 
     With reference to  FIG.  14 B , some embodiments of the towline connector  1528  may have a first proximal portion  1531  and a second distal portion  1533  that is coupled with or integrally formed with the first portion  1531 . The first portion  1531  may be tapered at a leading or proximal portion  1531   a  of the first portion  1531 . Additionally, a distal section  1531   b  of the first portion  1531  of the towline connector  1528  may have a round cross-section, as shown, or can have a square cross-section, polygonal cross-section, or have any other suitably shaped cross-section. The second portion  1533  of the towline connector  1528  can have a round cross-section, as shown, or can have a square cross-section, polygonal cross-section, or have any other suitably shaped cross-section. The second portion  1533  can have a cross-sectional size or diameter that is smaller than a cross-sectional size or diameter of the first portion  1531  such that the towline connector  1528  has a shoulder or ledge  1535  that can engage with a latch assembly  1540 , as will be described in greater detail below. The first and second portions  1531 ,  1533  of the towline connector  1528  maybe coaxially aligned along a longitudinal axis of the first and second portions  1531 ,  1533 . The towline connector  1528  may move up and down (or proximally and distally) along with the towline  102  in order to secure with the target aircraft  1200 . 
     In some embodiments, the towline connector  1528  may include a tube with an opening or pin at the lower end thereof configured to secure with a corresponding structure of the target aircraft  1200 , e.g. to secure with the capture mechanism  100 . In some embodiments, the towline connector may be guided by a bottom sheave (not shown) located below the top sheave  1520  and adjacent to the towline connector  1528 . The towline connector  1528  may be guided by the bottom sheave, for example a rotating wheel thereof. In some embodiments, the towline connector  1528  may be guided by a stationary guide or other component. 
     The latching system  1500  may include a latch housing  1530 . The towline connector  1528  may be located partially inside the latch housing  1530 . The latch housing  1530  may vertically secure the towline connector  1528 , for example by inserting one or more pins or bars through and/or around the adapter. For example, the latch assembly  1540  may be actuated (e.g., advanced and withdrawn in a horizontally axially direction as oriented) to engage and disengage with the towline connector  1528  to vertically secure the towline connector  1528  in place. For example and without limitation, the latch housing  1530  may include the latch assembly  1540  that may move between a first, latched position (as shown in  FIG.  14 A ) wherein the latch assembly  1540  is engaged with the towline connector  1528  so as to prevent any outfeed (e.g. movement vertically downward away from the latching system  1500 ) of the towline  102  and a second, unlatched position (not shown) wherein the latch assembly  1540  is axially withdrawn (e.g. leftward as oriented in the figure) and is disengaged from the towline connector  102  so that the towline  102  can be fed out (e.g. move vertically downward away from the latching system  1500 ). The latch assembly  1540  may move within a channel or passageway within the latch housing  1530 . In some embodiments, the latch assembly  1540  or a pin thereof may be spring-loaded. A spring may bias the latch assembly  1540  into the locked position as shown. The latch assembly  1540 , whether spring-loaded or otherwise, may be actuated in response to receiving the tow connector, which may be automatic, performed by a control system of the latching system, or actuated by a remote operator. 
     In some embodiments, the latch assembly  1540  may have a main body portion  1541  and a distal portion  1542 . The distal portion  1542  may have a recess or opening  1544  formed therein that maybe sized and configured to receive the second portion  1533  of the towline connector  1533  (e.g., may fit around an outside surface of the second portion  1533  of the towline connector  1533 ). The recess or opening  1544  formed in the distal portion  1542  maybe sized and configured to prevent the first portion  1531  of the towline connector  1533  from sliding therethrough such that, when the latch assembly  1540  is in the first, latched position (as shown in  FIG.  14 A ), the shoulder  1535  of the towline connector  1528  maybe abutted against the distal portion  1542  of the latch assembly  1540 . In some embodiments, the distal portion  1542  of the latch assembly  1540  can have an angled or beveled lower surface configured to cause the latch assembly  1340  to axially move or withdraw toward the unlatched position when the towline connector  1528  is reeled in (i.e., withdrawn) and forced into contact with the beveled lower surface of the latch assembly  1540 . In this arrangement, the latch assembly  1540  can be caused to automatically move to the unlatched position when the towline connector  1528  is reeled in and forced into contact with the beveled lower surface of the latch assembly  1540 . In some embodiments, the latch assembly  1540  may include a pin extending outwardly away from the body  1541  which extends through the towline connector  1528 . Therefore, a variety of different latching connections may be implemented. 
     In some embodiments, the latching system  1500  may include a cutter assembly  1542 . The cutter assembly  1542  may be configured to cut the towline  102 . The cutter assembly  1542  may include a blade, edge, knife, rotating saw, or other sharp edge to sever the towline  102 . The towline  102  may be cut in case of emergency where the target aircraft  1200  must be cut loose from the host aircraft  1100 , for instance if the winch  1400  or other mechanism has failed during recovery operations. 
     Any portion of any of the steps, processes, structures, and/or devices disclosed or illustrated in one example in this disclosure may be combined or used with (or instead of) any other portion of any of the steps, processes, structures, and/or devices disclosed or illustrated in a different example or flowchart. The examples described herein are not intended to be discrete and separate from each other. Combinations, variations, and some implementations of the disclosed features are within the scope of this disclosure. 
     While operations may be depicted in the drawings or described in the specification in a particular order, such operations need not be performed in the particular order shown or in sequential order, or that all operations be performed, to achieve desirable results. Other operations that are not depicted or described may be incorporated in the example methods and processes. For example, one or more additional operations may be performed before, after, simultaneously, or between any of the described operations. Additionally, the operations may be rearranged or reordered in some implementations. Also, the separation of various components in the implementations described above should not be understood as requiring such separation in all implementations, and it should be understood that the described components and systems may generally be integrated together in a single product or packaged into multiple products. Additionally, some implementations are within the scope of this disclosure. 
     Terms of orientation used herein, such as “top,” “bottom,” “proximal,” “distal,” “longitudinal,” “lateral,” and “end,” are used in the context of the illustrated example. However, the present disclosure should not be limited to the illustrated orientation. Indeed, other orientations are possible and are within the scope of this disclosure. Terms relating to circular shapes as used herein, such as diameter or radius, should be understood not to require perfect circular structures, but rather should be applied to any suitable structure with a cross-sectional region that may be measured from side-to-side. Terms relating to shapes generally, such as “circular,” “cylindrical,” “semi-circular,” or “semi-cylindrical” or any related or similar terms, are not required to conform strictly to the mathematical definitions of circles or cylinders or other structures, but may encompass structures that are reasonably close approximations. 
     Conditional language, such as “may,” “could,” “might,” or “may,” unless specifically stated otherwise, or otherwise understood within the context as used, is generally intended to convey that certain examples include or do not include, certain features, elements, and/or steps. Thus, such conditional language is not generally intended to imply that features, elements, and/or steps are in any way required for one or more examples. 
     Conjunctive language, such as the phrase “at least one of X, Y, and Z,” unless specifically stated otherwise, is otherwise understood with the context as used in general to convey that an item, term, etc. may be either X, Y, or Z. Thus, such conjunctive language is not generally intended to imply that certain examples require the presence of at least one of X, at least one of Y, and at least one of Z. 
     The terms “approximately,” “about,” and “substantially” as used herein represent an amount close to the stated amount that still performs a desired function or achieves a desired result. For example, in some examples, as the context may dictate, the terms “approximately,” “about,” and “substantially,” may refer to an amount that is within less than or equal to 10% of the stated amount. The term “generally” as used herein represents a value, amount, or characteristic that predominantly includes or tends toward a particular value, amount, or characteristic. As an example, in certain examples, as the context may dictate, the term “generally parallel” may refer to something that departs from exactly parallel by less than or equal to 20°. All ranges are inclusive of endpoints. 
     Several illustrative examples of towlines and related systems and methods have been disclosed. Although this disclosure has been described in terms of certain illustrative examples and uses, other examples and other uses, including examples and uses which do not provide all of the features and advantages set forth herein, are also within the scope of this disclosure. Components, elements, features, acts, or steps may be arranged or performed differently than described and components, elements, features, acts, or steps may be combined, merged, added, or left out in various examples. All possible combinations and subcombinations of elements and components described herein are intended to be included in this disclosure. No single feature or group of features is necessary or indispensable. 
     Certain features that are described in this disclosure in the context of separate implementations may also be implemented in combination in a single implementation. Conversely, various features that are described in the context of a single implementation also may be implemented in multiple implementations separately or in any suitable subcombination. Moreover, although features may be described above as acting in certain combinations, one or more features from a claimed combination may in some cases be excised from the combination, and the combination may be claimed as a subcombination or variation of a subcombination. 
     Further, while illustrative examples have been described, any examples having equivalent elements, modifications, omissions, and/or combinations are also within the scope of this disclosure. Moreover, although certain aspects, advantages, and novel features are described herein, not necessarily all such advantages may be achieved in accordance with any particular example. For example, some examples within the scope of this disclosure achieve one advantage, or a group of advantages, as taught herein without necessarily achieving other advantages taught or suggested herein. Further, some examples may achieve different advantages than those taught or suggested herein. 
     Some examples have been described in connection with the accompanying drawings. The figures may or may not be drawn and/or shown to scale, but such scale should not be limiting, since dimensions and proportions other than what are shown are contemplated and are within the scope of the disclosed invention. Distances, angles, etc. are merely illustrative and do not necessarily bear an exact relationship to actual dimensions and layout of the devices illustrated. Components may be added, removed, and/or rearranged. Further, the disclosure herein of any particular feature, aspect, method, property, characteristic, quality, attribute, element, or the like in connection with various examples may be used in all other examples set forth herein. Additionally, any methods described herein may be practiced using any device suitable for performing the recited steps. 
     For purposes of summarizing the disclosure, certain aspects, advantages and features of the inventions have been described herein. Not all, or any such advantages are necessarily achieved in accordance with any particular example of the inventions disclosed herein. No aspects of this disclosure are essential or indispensable. In many examples, the devices, systems, and methods may be configured differently than illustrated in the figures. or description herein. For example, various functionalities provided by the illustrated modules may be combined, rearranged, added, or deleted. In some implementations, additional or different processors or modules may perform some or all of the functionalities described with reference to the examples described and illustrated in the figures. Many implementation variations are possible. Any of the features, structures, steps, or processes disclosed in this specification may be included in any example. 
     In summary, various examples of towlines and related systems and methods have been disclosed. This disclosure extends beyond the specifically disclosed examples to other alternative examples and/or other uses of the examples, as well as to certain modifications and equivalents thereof. Moreover, this disclosure expressly contemplates that various features and aspects of the disclosed examples may be combined with, or substituted for, one another. Accordingly, the scope of this disclosure should not be limited by the particular disclosed examples described above, but should be determined only by a fair reading of the claims.