Patent Publication Number: US-2021173397-A1

Title: Unmanned aircraft turn and approach system

Description:
The present application is a Continuation Application of U.S. patent application Ser. No. 16/051,481, filed Jul. 31, 2018, which is a Continuation Application of U.S. patent application Ser. No. 15/355,014, filed Nov. 17, 2016, now U.S. Pat. No. 10,042,360, issued Aug. 7, 2018, which claims the benefit of U.S. Provisional Application No. 62/257,206, filed Nov. 18, 2015, each of which is incorporated herein by reference for all purposes. 
     The present invention relates generally to an unmanned aircraft control system providing the ability to turn and approach a target without losing a positive identification of the target. 
    
    
     BACKGROUND OF THE INVENTION 
     The use of unmanned aerial vehicles (“UAVs”) for delivering munitions to a target is known. In some cases, these UAVs are configured as remotely controlled missiles, in that they are configured to detonate upon reaching the target. Because these are typically limited-use or single-use or devices, the cost of each UAV is a critical design parameter. 
     For large single-use UAVs, the cost, size and weight of a guidance system component such as a camera on a two-dimensional gimbal may not be very significant. However, for very small UAVs, the cost, size and weight of such a system component can be very significant. Thus, very small UAVs must be designed with minimal complexity in their systems. 
     Modern rules of engagement may require that a positive identification (“PID”) of a target be established prior to initiating an attack while used within theatres of operation that may contain civilians. Typically, the PID must be maintained from a time prior to an activity that commits to the initiation of the attack, throughout a terminal phase of the attack. Additionally, in such theaters modern rules of engagement may require that a potential target be established as a legitimate target prior to reaching a wave-off requirement, i.e., a period of time (e.g., 5 seconds) prior to completing the attack. 
     With reference to  FIGS. 1A and 1B , a remotely controlled aircraft  10  that is equipped with a forward-looking camera  20 , a side-looking camera  30  and an integrated explosive. The forward-looking camera  20  has a limited forward field of view  22  and a separate side field of view  32  is provided by the side-looking camera  30 . This configuration provides for the aircraft to first locate a potential target  51 , and then loiter in a pattern  53  around the target until an operator/pilot of the aircraft establishes that the aircraft has a PID on a target that is a legitimate target. As shown in  FIG. 1B , one loitering technique is to fly the aircraft  10  in a geometric pattern (e.g., a circle) around the potential target until the legitimacy of the target  51  is established. In doing so, the side-view camera  30  maintains a continuous view of the potential target within its field of view  32 , and therefore it maintains a PID on the potential target so long as there are no obstructions. The velocity vector is roughly 90° off of the direction towards the target. The pattern  53  may be flown at a higher altitude than that of the glide path of an attack on the target. 
     In a target-approach maneuver, when the legitimacy of the target is established, the aircraft operator commits to the action at a ground commit-location  55  (a spot on the ground under the location where commit action was done), and flies an approximately 90° turn  57  to fly outbound, away from the target (on an outbound leg  59 ), for an appropriate distance. During this portion of the flight, the altitude may be reduced. The aircraft then flies a 180° turn  61  to fly inbound toward the target on an inbound leg  63 . 
     The 90° turn  57  is not as tight as the 180° turn  61  (i.e., the radius of the 180° turn has a smaller radius). This places the ground commit-location  55  in which the 90° turn was initiated between the ground locations of the aircraft and the target  51 . Thus, on the inbound leg, the aircraft returns to the ground commit-location  55  over which it initiated the 90° turn, having a velocity vector that is toward the target rather than roughly 90° off of that direction. This can be accomplished using inertial navigation and/or GPS. The inbound leg  63  includes an initial approach  67  leading from the 180° turn  61  to the ground commit-location  55 , and a final approach  69  leading from the ground commit-location  55  to the target  51 . 
     Because the aircraft loses sight of the target  51  throughout a portion of this outbound-and-inbound maneuver, the aircraft must reestablish PID on the target once it is visible in the forward-facing camera  20 . Because PID is lost during these maneuvers, the aircraft operator must then reestablish that the target is the previously identified legitimate target. 
     This outbound-and-inbound maneuver provides a number of advantages. First, it allows for the aircraft altitude to be reduced to a preferable glide path on both the outbound leg and the inbound leg. Second, it provides for the aircraft&#39;s velocity vector to be turned toward the target. Third, it provides for a longer approach to the target, and therefore more time for the operator to reestablish that the target is a legitimate target. Fourth, it allows for an attack through a narrow window of attack vectors, such as could occur when the target is located around or between tall buildings  65 . 
     Nevertheless, it also has drawbacks, in that requires a substantial amount of time to complete, and that it places the aircraft over more terrain at reduced altitudes. This potentially allows observers in the area, to detect the aircraft and raise the alarm. Moreover, the time for this extended maneuver allows time for a mobile target to depart, even if the aircraft is not detected. Also, after the PID is lost on the outbound leg, the legitimacy of the target must be reestablished on the inbound leg, raising the possibility that the legitimacy might not be reestablished prior to having to abort the attack. 
     It should be noted that in  FIG. 1B , the sizes of the various portions of the flight paths, and the sizes of the aircraft  10 , target  51  and obstructions  65 , are not necessarily representative of actual conditions. Rather, they are sized to clearly illustrate the concepts of the maneuver. 
     Accordingly, there has existed a need for an armed aircraft that is loitering around a target to be able to reduce its altitude to the level of a preferable glidepath, turn its velocity vector toward the target, and not lose time reestablishing that the target is legitimate, all while not incurring significant risk of exposure. Preferred embodiments of the present invention satisfy these and other needs, and provide further related advantages. 
     SUMMARY OF THE INVENTION 
     In various embodiments, the present invention solves some or all of the needs mentioned above, providing a small unmanned armed aircraft system that is able to turn its velocity vector toward a target while not losing a positive identification (“PID”) of the target while it is flying past or loitering around the target. 
     The unmanned aircraft system includes an aircraft including a wing system, a plurality of control surfaces, a camera on a camera pod, and a control system. The wing system is configured to carry the majority of the aircraft weight when in flight. The plurality of control surfaces is configured to control aircraft pitch, aircraft roll and aircraft yaw in flight. The camera is characterized by a field of view, and is mounted on the camera pod. The camera pod is configured to vary the orientation of the camera field of view only in yaw, relative to the aircraft, between a directly forward-looking orientation and a side-looking orientation. 
     Advantageously, when the camera is in an at least partially side-looking orientation and observing an identified target, the control system is configured to control the control surfaces, and further configured to control the camera pod to change the camera position in yaw relative to the aircraft so as to maintain a PID on the target. Using this system, the camera may maintain the PID of the target while the aircraft turns its flight vector toward the target. 
     Under a further feature of the invention, the control system controls the control surfaces such that they induce a significant aircraft yaw causing the identified target to be within the field of view of the camera with the camera in the directly forward-looking orientation. Advantageously, this allows the aircraft to roll significantly more than the field of view would allow without the camera being in the directly forward-looking orientation, providing for a sharper turn. 
     Other features and advantages of the invention will become apparent from the following detailed description of the preferred embodiments, taken with the accompanying drawings, which illustrate, by way of example, the principles of the invention. The detailed description of particular preferred embodiments, as set out below to enable one to build and use an embodiment of the invention, are not intended to limit the enumerated claims, but rather, they are intended to serve as particular examples of the claimed invention. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1A  is a perspective view of a prior art small, unmanned, weaponized aircraft. 
         FIG. 1B  is a prior art target-approach maneuver. 
         FIG. 2  is a perspective view of a small, unmanned, weaponized aircraft that is part of an aircraft system embodying the invention. 
         FIG. 3  is a remote-control station that is part of the aircraft system partially depicted in  FIG. 2 . 
         FIG. 4  is a launch tube that is part of the aircraft system partially depicted in  FIG. 2 . 
         FIG. 5  is a top view of the aircraft depicted in  FIG. 2 . 
         FIG. 6  is a cross-sectional view of the aircraft depicted in  FIG. 2  loaded into the launch tube depicted in  FIG. 4 . 
         FIG. 7  is a cross-sectional view of the aircraft depicted in  FIG. 2  being launched from launch tube depicted in  FIG. 4 . 
         FIG. 8  is a perspective view of a camera pod that is part of the aircraft depicted in  FIG. 2 . 
         FIG. 9  is a perspective view of the camera pod depicted in  FIG. 8 , set in a forward looking orientation on the aircraft depicted in  FIG. 2 . 
         FIG. 10  is a perspective view of the camera pod depicted in  FIG. 8 , set in a side looking orientation on the aircraft depicted in  FIG. 2 . 
         FIG. 11  is a depiction of a field of view of a camera on the camera pod depicted in  FIG. 8 . 
         FIG. 12  is an aerial view depiction of a set of possible approach vectors for a target in a first location. 
         FIG. 13  is an aerial view depiction of a set of possible approach vectors for a target in a second location. 
         FIG. 14  is an aerial view depiction of a set of possible approach vectors for a target in a third location. 
         FIG. 15  is a schematic view of an automated control system that is part of the aircraft system partially depicted in  FIG. 2 . 
         FIG. 16  is an aerial view depiction of three different PID operational variations. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The invention summarized above and defined by the enumerated claims may be better understood by referring to the following detailed description, which should be read with the accompanying drawings. This detailed description of particular preferred embodiments of the invention, set out below to enable one to build and use particular implementations of the invention, is not intended to limit the enumerated claims, but rather, it is intended to provide particular examples of them. 
     With reference to  FIGS. 2-5 , typical embodiments of the present invention reside in very small, weaponized, human-portable unmanned aircraft systems. One embodiment of an unmanned aircraft system under the invention includes an unmanned aircraft  101 , a remote-control station  103  (typically a ground station), and a launch tube  105 . The aircraft is configured as a remotely controlled missile, in that it is configured to detonate as a weapon upon reaching a target, destroying the aircraft and damaging or destroying the target. It is therefore a limited-use or single-use or aircraft, and thus the cost of the aircraft is a critical design parameter. 
     Unmanned Aircraft 
     The aircraft  101  includes a fuselage  111 , an empennage  113 , and a wing system including a main wing  115  configured to carry a significant portion of (and often the majority of) the aircraft weight when in flight. The wing and empennage are provided with a plurality of control surfaces  117  configured to control aircraft pitch, aircraft roll and aircraft yaw while in flight. 
     The aircraft  101  is characterized by a roll axis  121 , a pitch axis  123  and a yaw axis  125 . As is known in the art, the roll axis defines direct forward-looking and aft-looking directions, the pitch axis defines direct port and starboard side-looking directions, and the yaw axis defines direct upward-looking and downward-looking directions. 
     Launch System 
     With reference to  FIGS. 2, 4, 6 and 7 , the aircraft empennage  113  and main wing  115  flight surfaces  117  (including the control surfaces) are configured to rotate such that they rotate relative to the fuselage  111  between a retracted position (see,  FIGS. 6 and 7 ) and a flight position (see  FIG. 2 ). With the empennage and main wing in the retracted position, the aircraft  101  can be placed within the launch tube  105 . 
     To launch the aircraft  101  into flight, the aircraft is explosively ejected from the launch tube  105  (see  FIGS. 6 and 7 ). After the aircraft leaves the launch tube, the main wing  115  and empennage  113  are extended to their flight positions. The explosive launch of the aircraft subjects all components of the aircraft to high g-force levels. Therefore, all components of the aircraft must be adequately robust to survive the launch. 
     Camera System 
     With reference to  FIGS. 2, 5 and 8 , mounted on the fuselage  111  is a camera system having at least one camera, and typically including a pair of cameras, including a visual (EO) camera  131  and an infrared (IR) camera  133  mounted on a camera pod  135 . Each camera is characterized by a field of view  136 , which typically will be the same size or larger in a vertical dimension  137  than in a lateral dimension  139  (i.e., it is in a portrait orientation rather than a landscape orientation). The camera pod has only a single gimbal  140 , and is configured to vary the orientation of the camera field of view only in yaw relative to the aircraft  101 . 
     The camera pod  135  can rotate both the EO camera  131  and the IR camera  133  in yaw, relative to the aircraft, looking at least between a directly forward-looking orientation  141  (i.e., in the direct forward-looking direction depicted in  FIG. 9 ), and a directly side-looking orientation  143  (i.e., in one of the direct side-looking directions, such as one depicted in  FIG. 10 ). Optionally, the camera may be able to rotate the camera in yaw further, such as to orient the camera 45° aft  145  of the directly side-looking orientation to an aft-looking orientation  143 . 
     With reference to  FIGS. 8 and 11 , an exemplary EO camera might have a vertical field of view  151  of 60° in the vertical dimension  137 , and a lateral field of view  153  of approximately 40° in the lateral dimension  139 . Because the camera will generally be used for viewing the ground, its vertical center of view  155  might be angled downward from an aircraft lateral direction  157  (in level flight) by a downward-looking angle  159 , such as of 8° or more. Also, to maintain a positive identification (“PID”) of the target during turbulence, a safety margin  161  (typically of 5° to 10° should be maintained between the target&#39;s location in the field of view and the edge of the field of view. This defines an EO camera usable field of view  163 . 
     An exemplary IR camera might well have similar sizing, through not necessarily the exact same dimensions. It will have a vertical field of view in the vertical dimension, and a lateral field of view in the lateral dimension. It will have a center of vertical view angled downward from a camera vertical center view by a downward angle. To maintain PID during turbulence, a safety margin should be maintained between the target&#39;s location in the field of view and the edge of the field of view. Thus defining an IR camera usable field of view. 
     For either camera, when a PID of a target is established in the usable field of view (e.g., the EO camera usable field of view  163 ) with the camera in a side-looking yaw orientation with respect to the aircraft, the ability of the aircraft to roll without losing PID is limited by the usable field of view. More particularly, the aircraft cannot roll to turn toward the target any farther than the top of the usable field of view allows (or PID is lost). Likewise, the aircraft cannot roll to turn away from the target any farther than the bottom of the usable field of view allows (or PID is lost). 
     For either camera, when a PID of a target is established in the usable field of view (e.g., the EO camera usable field of view  163 ) with the camera in a forward-looking yaw orientation with respect to the aircraft, the ability of the aircraft to roll is not limited by the usable field of view so long as the target is within a safe roll zone of the field of view. The safe roll zone is the portion of the field of view in which objects stay in view regardless of the roll angle of the aircraft up to a maximum roll angle, such as up to ±90°. This will be affected by various parameters, such as the downward-looking angle  159  and the flight characteristics of the aircraft. For a given aircraft, this may be experimentally determined. 
     Remote-Control Station 
     With reference to  FIG. 3 , the aircraft system remote-control station  103  will typically, but not necessarily, be used by an operator/pilot on the ground (e.g., a ground station). Other possible operator/pilot locations include a boat or a plane. 
     The remote-control station  103  is configured for the operator to remotely control the aircraft. More particularly, the remote-control station includes a video monitor  171  (as is known for unmanned aircraft) for displaying both flight control information and a live video feed from the aircraft to provide for visual flight, particularly for when the aircraft is not in view of the user. The remote control station further has a manual controller  173  to control the various aircraft features and functions. Optionally, this controller may be of a type similar to those known for video gaming such that the operation of the aircraft  101  might be more quickly learned by operators familiar with video game controls. 
     To provide communication with the aircraft  101 , the remote-control station  103  is provided with communication equipment  175  configured for the transmission and receipt of communication signals  177 , and thus the remote-control station is provided with two-way communication with the aircraft. These communication signals may include flight control information and commands, and payload related signals. 
     Attack Vectors 
     With reference to  FIGS. 12-14 , different target locations will be characterized by different windows of attack vectors. In some locations (see, e.g.,  FIG. 12 ), there may be many obstructions around a target  201 , allowing for only a limited range  203  of attack vectors, extending from an initial attack vector  205  option to a final attack vector  207  option. It should be noted that the terms initial and final in this context respectively denote the first available attack vector (final approach vector) from a given pattern of loiter  209  in a given direction, and the last available attack vector from that pattern of loiter. 
     In other locations (see, e.g.,  FIG. 13 ), there may be some obstructions around a target  211 , allowing for a much wider range  213  of attack vectors, extending from an initial attack vector  215  option to a final attack vector  217  option around a given pattern of loiter  219  in a given direction. In yet other locations (see, e.g.,  FIG. 14 ), there may be no obstructions around a target  221 , allowing for a 360° range  223  of attack vectors  225  options. It should be noted that the shape of the loiter pattern might also limit the range of attack vectors. For example, the aircraft might have to avoid casting a shadow on the target, and thus it might fly too close to a target to set up an attack vector using a desired maneuver. 
     It should be noted that in the various figures depicting targets and flight paths in this detailed description, the sizes of the various portions of the flight paths, and the sizes of the targets and obstructions are not necessarily representative of actual conditions. Rather, they are sized to clearly illustrate the depicted concepts. 
     Automated Control System 
     With reference to  FIGS. 2, 3 and 15 , the aircraft system includes an automated control system  241  having both hardware and software, the hardware including a processor and computer memory. The automated control system includes an aircraft control system  243  on the aircraft  101 , and a station control system  245  on the remote-control station  103 . 
     The aircraft control system  243  is provided with wiring functionally linking the aircraft control system to servos configured to control the control surfaces  117 , and is further provided with wiring functionally linking the aircraft control system to a servo configured to control the camera pod  135  so as to change the camera orientation in yaw relative to the aircraft. 
     To provide communication with the remote-control station  103 , the aircraft  101  is provided with communication equipment configured for the transmission and receipt of the remote-control station communication signals  177 . These communication signals may include flight control information and commands, and payload related signals. 
     The automated control system  241  provides an operator of the remote-control station  103  to manually control the aircraft  101 , and further provides for various automated autopilot functions. Among these automated autopilot functions is a COMMIT function for use when a target is identified, typically with PID. The COMMIT function may be used when the camera pod  135  positions the camera  131  in an at least partially side-looking orientation (e.g., depicted in  FIG. 10 ) and observing an identified target to the side of the aircraft and within the range of side looking angles that are within the yawing range of the camera pod. Also among the functions is an ABORT function, in which a COMMIT function is aborted and full control of the aircraft either returns to the operator or returns to a standard flight computer autopilot. 
     The COMMIT function causes the automated control system  241  to control the control surfaces, the camera system yaw servos and the payload (weapon) such that the aircraft is guided to the target and the payload is activated. The COMMIT function may be used in a variety of situations. In each of the situations, the operator of the remote-control station  105  has typically established a PID of a target that has been established as a legitimate target. 
     In a first situation, the aircraft  101  is circumnavigating an identified target in a pattern that might or might not be circular. In this situation, the camera pod  135  might not have to adjust the yaw of the camera system relative to the aircraft to keep the target within view prior to using the COMMIT function. In a second situation, the aircraft is flying past an identified target, possibly in a straight line. In this situation, the camera pod needs to continuously (or periodically) adjust the yaw of the camera system relative to the aircraft to keep the target within the usable field of view of at least one camera of the camera system. Similarly, in a third situation, if the aircraft was close to a target on the side of the aircraft (e.g., flying in a circle around the target or a straight line past the target), the aircraft could spiral radially outward relative to the target, allowing a PID while slightly increasing the approach distance and decreasing the altitude. A wide variety of other situations are also envisioned within the scope of the invention, such as spiraling inward toward a target. 
     The COMMIT function may include a variety of operational variations. At least some of these COMMIT function operational variations maintain the PID of the target throughout the flight to the target, and require no further participation by an operator. 
     Regardless of what operational variation is desired, prior to initiating the COMMIT function, the desired operational variation is selected, such as from a pull-down menu. Depending on the selected operational variation, some pre-COMMIT flight activities might be necessary. For example, some altitude may need to be reduced prior to doing certain operational variations. Also, some changes in airspeed may be necessary. To accommodate some maneuvers, it might be preferable to manually spiral outward or inward prior to initiating the COMMIT function. It should be noted that all of the described pre-COMMIT flight activities could be incorporated into a COMMIT function to create yet additional operational variations of the COMMIT function. 
     Once any pre-COMMIT activities are completed, the operator activates the COMMIT function on the remote-control station  105 . At this point the automated control system takes control of the aircraft and guides it to the target. For many (though typically not all) COMMIT operational variations, this activity happens from beginning to end without losing PID, and thus without requiring the operator to reestablish that the target is a legitimate target. 
     Regardless of the pre-COMMIT activities, in the situations described above there are a number of possibilities regarding the relative positions of the aircraft and target prior to a pre-COMMIT function. First, the aircraft can be approaching the target on a linear or curving profile, such that the necessary turn angle (i.e., the angle between the present velocity and the final approach angle) is under 90°. This may also be because the aircraft is on a curving flyby that has not yet achieved flight normal to the radial vector from the target. Second, the aircraft can be circumnavigating the target, such that the necessary turn angle (i.e., the angle between the present velocity and the final approach angle) is likely to be (though not necessarily be) close to 90°. Thirdly, the aircraft can be receding from the target, such that the necessary turn angle (i.e., the angle between the present velocity and the final approach angle) is greater than 90°. 
     Commit Function Operational Variations 
     In a first operational variation, the operator may select the use of the prior art outbound-and-inbound maneuver. In this operational variation, the operator must reestablish PID on the target once it is flying directly toward the target, and therefore establish the legitimacy of the target. In other operational variations, the operator may select one of a variety of maneuvers that allow for a PID of the target to be maintained throughout the maneuver. The phrase “PID operational variations” is to be defined as operational variations that allow for a PID of the target to be maintained throughout the maneuver so long as an obstruction does not interfere with PID. 
     With reference to  FIGS. 16 and 11 , a first PID operational variation  301  is the use of a coordinated turn  302  (i.e., a turn with all control surfaces coordinated to prevent any aircraft side-slip) to turn the aircraft toward a target  303 , such as from a loiter pattern  305 . More particularly, from a ground commit-location  307  the turn  302  is conducted and completed prior to entering a preferably straight final approach  309  on the target. During this maneuver, the yaw of the camera system must be continuously or periodically adjusted to keep the camera pointing toward the target. Because PID must be maintained, the aircraft roll angle is limited by the location of the target in the usable field of view. More particularly, the target cannot be allowed to drift past the top of the usable field of view. 
     An advantage of this first PID operational variation  301  is that it limits the time to reach the target, and the risk of detection. Limitations to the use of this PID operational variation include the possibility that the aircraft is to high to lose enough altitude before the ground location is reached (i.e., flying over the target instead of at the target). Another limitation is that if a certain length of time in straight flight final approach is desired, the aircraft it must have a wide enough loiter to complete the turn prior to entering the final approach. 
     A second PID operational variation  321  is a two part maneuver. In the first part  323 , from the ground commit-location  307 , the aircraft is directed to increase its distance from the target while maintaining PID. This can be done by flying past the target, by spiraling away from the target, or even by turning partially away from the target. In the second part  325 , a coordinated turn is used to turn the aircraft back toward the target, and preferably into a straight final approach  327 . During this maneuver, the yaw of the camera system must be continuously or periodically adjusted to keep the camera pointing toward the target. Because PID must be maintained, the aircraft roll angle (both in turning away from the target and toward the target) is limited by the location of the target in the usable field of view. More particularly, the target cannot be allowed to drift past the either the top or the bottom of the usable field of view. 
     An advantage of this second PID operational variation  321  is that it allows for more altitude loss prior to reaching the target, while limiting the time to reach the target as much as the altitude loss requirements will allow. Another advantage is that it may significantly lengthen the time spent in straight final approach  327 . Thus, if PID is lost during the turning portions of the maneuver (such as due to turbulence or obstructions), more time is available to reestablish PID of the target. 
     A third PID operational variation  351  is also a two part maneuver. In the first part  353 , at the ground commit-location  307 , the aircraft is directed to sharply yaw so as to face the target, while maintaining PID. This will cause a significant slip and loss of lift, as the aircraft&#39;s flight vector will not change substantially, and it will not be flying in the direction it is facing. The pitch of the aircraft must be kept such that position of the target in the usable field of view is within the safe roll zone. With the target in front of the aircraft and in the safe roll zone, the aircraft can freely roll without loss of PID. 
     In the second part  355  of the maneuver, a significant roll is initiated to turn the aircraft flight vector toward the target. During this part of the maneuver, the yaw of the camera system will usually not need to be adjusted to keep the camera pointing toward the target. Because PID is not at risk when the aircraft rolls while facing the target, the aircraft roll angle is not limited by the location of the target in the usable field of view. Once the flight vector is directly toward the target, the aircraft roll angle is returned to zero and a straight final approach  357  is entered. 
     An advantage of this third PID operational variation  351  is that it may provide for a much sharper turn in the flight path than a coordinated turn that is limited in roll angle (the first PID operational variation  301 ). Also, the altitude may be reduced during both parts of the maneuver, and a longer final approach  357  may be obtained as compared to the first PID operational variation  301 . 
     Limitations to the use of this third PID operational variation  351  include the fact that the aircraft control surfaces will only be able crab the aircraft (turn it in yaw) a certain amount, which will vary depending on factors such as the aerodynamics of the aircraft. It is likely that this crab limitation will be to angles no greater than 90°, and probably to a crab limitation significantly less than 90°. Thus, this PID operational variation might be most useful when the aircraft is flying partially toward the target (such as flying in a straight line toward an entry point to a circular loiter). Another limitation is that either or both parts of this maneuver could cause the aircraft to have partially or completely separated flow over the wing system. As a result, the control surfaces could lose effect, causing a loss of control over the aircraft. Therefore, this risk further limits the extent to which the maneuver can be conducted. 
     Additional PID operational variations may include combinations of portions of the aforementioned PID operational variations. For example, in a fourth PID operational variation if the aircraft is outside the crab limitation of the third PID operational variation  351  (e.g., it is in a circular loiter, or it is in a straight line flight passing the target), in a first part of a maneuver, the aircraft may be directed to start the coordinated turn of the first PID operational variations  301 . Once the aircraft has turned toward the target enough to be within the crab limitation of the third PID operational variation, the aircraft is rolled to be level, and then the third PID operational variation is conducted. Optionally, the third PID operational variation yaw could be initiated without first rolling to level. It should be noted that this PID operational variation can be used even if the aircraft starts off within the crab limitation of the third PID operational variation. 
     Similar to this, in a fifth PID operational variation, if the aircraft is outside the crab limitation of the third PID operational variation  351 , in a first part of a maneuver, the aircraft may be directed to start the coordinated turns of the second PID operational variation  321 . Once the aircraft has turned toward the target enough to be within the crab limitation of the third PID operational variation, the aircraft is rolled to be level, and then the third PID operational variation is conducted. Optionally, the third PID operational variation yaw could be initiated without first rolling to level. It should be noted that this PID operational variation can also be used even if the aircraft starts off within the crab limitation of the third PID operational variation. 
     It should be noted that additional operational variations may include variants of the PID operational variations that are programmed for use near visual obstacles. In these additional operational variations, the automated control system can be programmed to mimic any one of the PID operational variations, and continue to fly the maneuvers even when the view is obstructed by the visual obstacle. Once the obstacle is passed, the view of the target is reestablished, and the operator must reestablish PID, i.e., establishing that the target is legitimate. 
     It is to be understood that the invention comprises apparatus and methods for designing aircrafts and for producing aircrafts, as well as the apparatus and methods of the aircraft itself. In short, the above disclosed features can be combined in a wide variety of configurations within the anticipated scope of the invention. 
     While particular forms of the invention have been illustrated and described, it will be apparent that various modifications can be made without departing from the spirit and scope of the invention. Thus, although the invention has been described in detail with reference only to the preferred embodiments, those having ordinary skill in the art will appreciate that various modifications can be made without departing from the scope of the invention. Accordingly, the invention is not intended to be limited by the above discussion, and is defined with reference to the following claims.