Patent Abstract:
Apparatuses, systems, and methods described herein provide for a refueling boom having vertical control surfaces extending primarily downward below the horizontal control surfaces out of the auxiliary power unit (APU) exhaust and airframe-induced turbulent flow fields, while reducing the torque moments applied to the boom beam and increasing control authority. According to one aspect of the disclosure provided herein, a refueling boom includes a boom beam, at least one horizontal control surface, and a pair of vertical control surfaces. The vertical control surfaces are positioned on opposing ends of the horizontal control surfaces and each include an upper portion and a longer lower portion projecting downward below the horizontal control surface. Aspects further improve the aerodynamic characteristics of the boom beam, reducing the drag associated with the refueling boom.

Full Description:
BACKGROUND 
     Tanker aircraft utilize refueling booms to transfer fuel from tanks within the tanker aircraft to aircraft receiving the fuel while in-flight. Conventional refueling booms are pivotally mounted at one end to the tanker aircraft and typically include a telescoping nozzle with a connector at the opposite end of the boom that connects to a corresponding receptacle of the receiving aircraft. Once connected, fuel is transferred from the tanks within the tanker aircraft to the receiving aircraft via the boom. 
     Refueling booms are designed to rotate upwards to the tail of the tanker aircraft for stowage in a position that does not interfere with rotation of the tanker aircraft during takeoff operations and to minimize drag on the aircraft when not in use. During refueling operations, typical refueling booms are designed to rotate downwards in position for mating with the receiving aircraft and for transferring fuel. To aid in the process of mating the boom nozzle to the receiving aircraft, conventional booms include control surfaces mounted to the boom that can be manipulated by an operator aboard the tanker aircraft to “fly” the boom as necessary to align the nozzle with the receptacle of the receiving aircraft. 
     Conventional control surfaces for a refueling boom may include a pair of V-shaped surfaces, or ruddervators, that can be moved independently to control the movement of the boom. Alternatively, some refueling booms have control surfaces that include at least one horizontal control surface for controlling the pitch of the boom, and a pair of canted vertical control surfaces attached to opposing ends of the at least one horizontal control surfaces that are used to control the roll and yaw of the boom. These vertical control surfaces extend substantially upwards from the at least one horizontal control surfaces, with a majority of the vertical surfaces above the horizontal surfaces. 
     This upward configuration of the vertical control surfaces creates several undesirable results. First, when the refueling boom is stowed and the tanker aircraft is operating on the ground with the auxiliary power unit (APU) running, the exhaust of the APU flows over the at least one horizontal control surfaces and between the vertical control surfaces. If a sufficient cross-wind exists, this APU exhaust can be pushed over a vertical control surface, undesirably heating and buffeting the control surface, potentially leading to premature material failure or defects due to material fatigue. 
     Second, during cruise flight of the tanker aircraft, ambient airflow over the horizontal stabilizers and elevators of the aircraft creates a turbulent flow aft of the elevator root area. When the refueling boom is stowed during cruise flight, the upward extending vertical control surfaces of the conventional refueling boom may be positioned within this turbulent flow field, creating undesirable buffeting that stresses the control surfaces, which creates additional parasite drag and also could contribute to premature failure or defects. Third, the conventional configuration of the vertical control surfaces positions the aerodynamic center of these surfaces above the refueling boom, which imposes a torque moment on the boom beam, requiring structural solutions that increase the weight of the boom. 
     It is with respect to these considerations and others that the disclosure made herein is presented. 
     SUMMARY 
     It should be appreciated that this Summary is provided to introduce a selection of concepts in a simplified form that are further described below in the Detailed Description. This Summary is not intended to be used to limit the scope of the claimed subject matter. 
     Apparatuses, systems, and methods described herein provide for an improved refueling boom having vertical control surfaces that are not subjected to stresses due to APU exhaust or turbulent flow fields from the tanker aircraft and that reduce the torque moments applied to the boom beam. Aspects further improve the aerodynamic characteristics of the boom beam, reducing the drag associated with the refueling boom. 
     According to one aspect of the disclosure provided herein, a refueling boom includes a boom beam, at least one horizontal control surface, and a pair of vertical control surfaces. The one or more horizontal control surfaces are positioned on the boom beam with the vertical control surfaces positioned on opposing ends. The vertical control surfaces each include an upper portion projecting upwards from the horizontal control surface and a lower portion projecting downward from the horizontal control surface. The length of the lower portion of each vertical control surface is greater than the length of the upper portion. 
     According to another aspect, a tanker aircraft includes a fuselage, a fuel tank, and a refueling boom attached to the fuselage and fluidly linked to the fuel tank for transferring fuel to a refueling aircraft. The refueling boom includes a boom beam and control surfaces for aerodynamically controlling the movement of the boom beam. The control surfaces include at least one horizontal control surface and a pair of vertical control surfaces. The vertical control surfaces are positioned on opposing ends of the horizontal control surfaces and each include an aerodynamic center that is positioned below the horizontal control surfaces. 
     According to yet another aspect, a method for controlling an aircraft refueling boom of a tanker aircraft includes actuating one or more horizontal control surfaces positioned above the boom beam of the refueling boom and actuating a pair of canted vertical control surfaces positioned on opposing ends of the horizontal control surfaces. Actuating the horizontal control surfaces alters the ambient airflow pressure over the horizontal control surfaces, causing the boom beam to move around a pitch axis. Actuating the vertical control surfaces alters the ambient airflow pressure at an aerodynamic center of each vertical control surface located below the horizontal control surface, causing the boom beam to move around a roll axis. 
     The features, functions, and advantages that have been discussed can be achieved independently in various embodiments of the present disclosure or may be combined in yet other embodiments, further details of which can be seen with reference to the following description and drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIGS. 1A and 1B  are perspective and side views, respectively of a tail portion of a tanker aircraft showing a conventional refueling boom configuration; 
         FIG. 2  is a top view of a tail portion of a tanker aircraft showing the effects of an auxiliary power unit (APU) exhaust stream in a cross wind on a conventional refueling boom in a stowed configuration; 
         FIGS. 3A and 3B  are top and side views of a tail portion of a tanker aircraft showing the effects of a turbulent flow field produced by the tanker aircraft on a conventional refueling boom in a stowed configuration; 
         FIGS. 4A and 4B  are front and perspective views, respectively, of a refueling boom in a deployed configuration according to various embodiments presented herein; 
         FIG. 5  is a side view of a rear portion of a tanker aircraft with a refueling boom in a stowed configuration showing a rotation clearance angle with respect to a refueling boom according to various embodiments presented herein; 
         FIG. 6  is a side view of a rear portion of a tanker aircraft with a refueling boom in a deployed configuration showing a comparison of aerodynamic center positioning and associated roll moment effects between a refueling boom with conventional vertical control surfaces and with vertical control surfaces according to various embodiments presented herein; 
         FIG. 7  is a top view of a refueling boom showing a comparison in horizontal surface area and corresponding pitching moment effects between a refueling boom with conventional vertical control surfaces and with vertical control surfaces according to various embodiments presented herein; 
         FIG. 8  is a cross-sectional view of a conventional refueling boom beam; 
         FIG. 9A  is a cross-sectional view of a refueling boom beam with leading edge and trailing edge fairings according to various embodiments presented herein; 
         FIG. 9B  is a cross-sectional view of a refueling boom beam with a continuous outer surface and symmetrical airfoil shape according to various embodiments presented herein; 
         FIGS. 10A and 10B  show perspective views of a portion of a refueling boom with a snubber fairing, and of the snubber fairing, respectively, according to various embodiments presented herein; 
         FIG. 11  is a flow diagram illustrating a method for providing an aircraft refueling boom according to various embodiments presented herein; and 
         FIG. 12  is a flow diagram illustrating a method for controlling an aircraft refueling boom according to various embodiments presented herein. 
     
    
    
     DETAILED DESCRIPTION 
     The following detailed description is directed to refueling booms, tanker aircraft, and methods for providing an aircraft refueling boom of a tanker aircraft. As discussed briefly above, conventional refueling booms often include vertical control surfaces that are subject to material fatigue and increased drag due to undesirable interaction with the exhaust streams of auxiliary power units (APUs) and with turbulent flow fields created by the horizontal stabilizers and elevators of the tanker aircraft to which the booms are attached. In the following detailed description, references are made to the accompanying drawings that form a part hereof, and which are shown by way of illustration, specific embodiments, or examples. Referring now to the drawings, in which like numerals represent like elements through the several figures, a refueling boom with enhanced vertical control surfaces will be described. 
     However, before describing the various embodiments disclosed below for resolving these issues, the conventional refueling boom configurations and associated disadvantages will be described with respect to  FIGS. 1A-3B  for illustrative comparative purposes.  FIGS. 1A and 1B  show a tanker aircraft  102  having a conventional refueling boom  104  with control surfaces  108  attached to a boom beam  106 . As described briefly above, the control surfaces  108  include one or more horizontal control surfaces  110  and conventional vertical control surfaces  112  attached to opposing ends of the horizontal control surfaces  110 . The conventional vertical control surfaces  112  may include an upper portion  114  that projects upwards above the horizontal control surfaces  110  and a lower portion  116  that projects downward below the horizontal control surfaces  110 . 
     The upper portion  114  of the conventional vertical control surfaces  112  are longer than the lower portion  116 , resulting in a control surface  108  that generally extends upwards from the boom beam  106 , resting aft of the tail and horizontal stabilizers  120  of the tanker aircraft  102  when the boom is in a stowed configuration. As described above, this positioning has undesirable consequences. One consequence is shown in  FIG. 2 , where the APU  202  for the tanker aircraft  102  is shown in the typical installation location in the tail of the aircraft. When operating while the aircraft is on the ground, the APU  202  creates an APU exhaust stream  204  that flows over the conventional refueling boom  104 , generally between the conventional vertical control surfaces  112 . 
     However, aircraft are commonly subjected to crosswinds during ground operations, as well as during flight. In this scenario, the tanker aircraft  102  is on the ground with the APU  202  operating, while subjected to a crosswind  206 . As seen in  FIG. 2 , the crosswind  206  forces the APU exhaust stream  204  over the conventional vertical control surface  112 . In doing so, the vertical control surface  112  is subjected to undesirable heat and stress. 
       FIGS. 3A and 3B  further illustrate an undesirable consequence of the upwardly extended configuration of the conventional vertical control surfaces  112 . During cruise flight and other flight conditions, the horizontal stabilizers  120  and/or elevators of the tanker aircraft  102  create turbulent vortices, or a turbulent flow field  302 . The conventional vertical control surfaces  112  are exposed to this turbulent flow field  302 , which not only creates undesirable drag on the aircraft, but also stresses the surfaces and creates a potential for material fatigue and failure. 
     Turning now to  FIGS. 4A and 4B , a refueling boom  404  according to various embodiments will now be described. According to this embodiment, the refueling boom  404  includes a boom beam  406  with control surfaces  408  attached. The control surfaces  408  include one or more horizontal control surfaces  410  and a pair of vertical control surfaces  412 . The horizontal control surfaces  410  may include a single or a pair of horizontal surfaces and/or elevators that rotate together or independently to control the vertical movement of the refueling boom  404  around a pitch axis. The pair of vertical control surfaces  412  is attached to opposing ends of the horizontal control surfaces  410 . The vertical control surfaces  412  include an upper portion  414  that projects upwards above the horizontal control surfaces  410  and a lower portion  416  that projects downward below the horizontal control surfaces  410 . 
     The vertical span of the vertical control surfaces  412  includes the length A of the upper portion  414  plus the length B of the lower portion  416 . Length A spans between an upper root edge  418  to an upper tip edge  420 , while length B spans between a lower root edge  422  to a lower tip edge  424 . The precise lengths A and B, as well as the overall length of the vertical span of the vertical control surfaces  412 , may differ according to the specific implementation. However, according to embodiments presented herein, the ratio of A/B is less than one. In other words, the length B of the lower portion  416  of each vertical control surface  412  is longer than the length A of the upper portion  414  of the vertical control surface  412 . 
     As seen in  FIG. 4A , the vertical control surfaces  412  cant outward at an unhedral angle  426  away from the boom beam  406  in a direction from the upper tip edge  420  to the lower tip edge  424 . In doing so, the pivoting surfaces of the vertical control surfaces, or rudders, create aerodynamic forces at an angle to the boom beam  406  that enables an operator to move the refueling boom  404  in a rolling arc-like motion, which along with the pitch control from the horizontal control surfaces  410 , provides full control of the movement of the refueling boom  404  throughout the boom operating envelope. In fact, the configuration of the refueling boom  404  with the downwardly oriented vertical control surfaces  412  provides for increased control authority over the boom movement as compared to the conventional refueling boom  104 , as will be described in greater detail below with respect to  FIGS. 6 and 7 . 
     Referring now to  FIG. 5 , it will become clear that the configuration of the refueling boom  404  does not negatively impact the rotation angle of the tanker aircraft  102  with respect to ground clearance.  FIG. 5  shows two lines,  502  and  504 . Line  502  represents the lowest point of the refueling boom  404  that must clear the ground when the tanker aircraft  102  rotates during takeoff. It should be understood that depending on the specific implementation, the lower tip edge  424  of the vertical control surfaces  412  may or may not extend below a plane parallel with and containing the boom beam  406 . 
     Line  504  is tangential to a boom fitting fairing on the fuselage to which the refueling boom  404  is attached. The boom fitting fairing is unchanged from conventional fairings to which a conventional refueling boom  104  would be attached. Because line  502  is above line  504 , it can be seen that the configuration of the refueling boom  404 , in which the vertical control surfaces  412  are oriented in a substantially downwards direction from the horizontal control surfaces  410 , does not impact the rotation angle of the tanker aircraft  102  since the boom fitting fairing would contact the ground prior to the refueling boom  404 . 
       FIG. 6  shows a roll axis  600  around which the vertical control surfaces  412  roll the boom beam  406 . This figure illustrates the increase in the rolling moment effectuated by the downward configuration of the vertical control surfaces  412  as compared to conventional vertical control surfaces  112 . The vertical control surfaces  412  are depicted in solid lines according to embodiments described herein, while the conventional vertical control surfaces  112  are depicted in broken lines for comparative purposes. The aerodynamic center  602  of the conventional vertical control surface  112  is shown along with the aerodynamic center  604  of the vertical control surface  412 . It should be appreciated that the locations of the aerodynamic centers  602  and  604  are approximated in the figure and that the precise locations would depend on the characteristics of the respective flight control surfaces. 
     As is readily known in the art, the rolling moment around the roll axis  600  may be approximated by the aerodynamic force applied at the aerodynamic center multiplied by the moment arm, or distance of the aerodynamic center from the roll axis  600 . In this example, the rolling moment associated with the conventional vertical control surface  112  is the force applied at the aerodynamic center  602  multiplied by the length of the moment arm  606 . Similarly, the rolling moment associated with the vertical control surface  412  is the force applied at the aerodynamic center  604  multiplied by the length of the moment arm  608 . It can be seen that because the length of the moment arm  608  is greater than the length of the moment arm  606 , for equivalent aerodynamic forces applied at the respective aerodynamic centers, the rolling moment associated with the vertical control surface  412  is greater than the rolling moment associated with the conventional vertical control surface  112 . The result of this increased rolling moment is more control in the roll direction over conventional booms, and consequently, and expanded operating envelope. 
     Another benefit associated with the downward orientation of the vertical control surfaces  412  is the decrease in the torque moment applied to the boom beam  406 . The conventional vertical control surfaces  112  induce a torque moment on the boom beam  406  from the aerodynamic forces applied at the aerodynamic center  602 , which is a moment arm  612  from the boom beam axis  610  extending through the boom beam  406 . As seen in  FIG. 6 , the downward extending vertical control surfaces  412  position the aerodynamic center  604  at a position proximate to the boom axis  610 . This positioning significantly reduces or eliminates the moment arm  612 , which significantly reduces or eliminates the torque applied to the boom beam  406  from the vertical control surfaces  412 . As a result, the materials used to create the boom beam  406  may be lighter than those used to create the conventional boom beam  106 . 
     Moreover, in addition to an increased rolling moment and decreased torque moment, the configuration of the vertical control surfaces  412  of the refueling boom  404  also increase the pitching moment around the pitch axis, further improving the control authority of the refueling system. Looking at  FIG. 7 , a top view of a refueling boom  104 / 404  is shown. The top half of the boom illustrates the horizontal projection of the area of the control surfaces  108  for a conventional refueling boom  104 . The bottom half of the boom illustrates the horizontal projection of the area of the control surfaces  408  for the refueling boom  404 . Because the area associated with the control surfaces  408  (represented by diagonal hatching) is larger than the area associated with the conventional control surfaces  108  (represented by cross-hatching), the aerodynamic force associated with the pitching moment around the pitch axis  702  may be larger as compared to a conventional refueling boom  104 . Because the moment arm  704  does not change, but the force is increased, the result of the configuration of the vertical control surfaces  412  as compared to the conventional vertical control surfaces  112  is an increased pitching moment. 
     Turning now to  FIG. 8 , another embodiment of the disclosure will be described. As seen in  FIG. 8 , a cross-section of a conventional refueling boom beam  106  reveals a linear leading edge surface  802 , a linear trailing edge surface  804 , and connecting curved sidewalls  803 . It should be appreciated that the linear leading and trailing edge surfaces  802  and  804 , respectively, may not be completely flat, but do not aerodynamically transition into the curved sidewalls  803  to create an airfoil cross-sectional shape. Accordingly, as the boom beam  106  traverses through the ambient airflow  806 , substantial drag is induced at the “flat” leading edge of the boom beam  106 , and turbulent airflow  808  is created aft of the boom beam  106 , further increasing the overall drag on the refueling beam  104  and tanker aircraft  102 . 
     In contrast, two embodiments of the present disclosure are shown in  FIGS. 9A and 9B , each of which provide for a symmetrical airfoil cross-sectional shape of the boom beam  406  in order to minimize the drag induced by the boom. It should be appreciated that the cross-sectional shapes shown in  FIGS. 9A and 9B  are cut from a plane parallel to the ambient airflow when the refueling boom is configured in a deployed configuration. The first embodiment is shown in  FIG. 9A  and is created by retrofitting or modifying the conventional boom beam  106  shown in  FIG. 8  to create the boom beam  406  having an aerodynamic cross-sectional shape. The cross-sectional shape of an airfoil shown in  FIG. 9A  is created by installing a leading edge fairing  902  and a trailing edge fairing  904  to the linear leading edge surface  802  and to the linear trailing edge surface  804 , respectively, of the existing boom beam  106 . Each fairing is shaped to blend with the exterior curved sidewalls  803  to create the desired airfoil shape. The fairings may be constructed from metal, composite, or any other suitable materials and may have a hollow or honeycomb interior structure. 
     It should be appreciated that the cross-sectional shapes shown in  FIGS. 8 ,  9 A, and  9 B are shown for illustrative purposes only. In practice, the boom beams  106  and  406  may have any cross-sectional shape and features. The leading edge fairing  902  and trailing edge fairing  904  are shaped accordingly to create an outer surface of the boom beam  406  with improved aerodynamic characteristics to decrease the corresponding drag while the boom is deployed or while stowed. The fairings may be installed using any number and type of fasteners  912  or any other fixed or removable securing means. Rubber or other flexible types of gaskets may be used between the fairings and the boom beam  106  to minimize wear between the components. 
     Grooves may be cut longitudinally into the boom beam  106  at the junction of the curved sidewalls  803  with the linear leading and trailing edge surfaces  802  and  804 , respectively, to accommodate a flange on the fairings (not shown) in order to facilitate a conformal fit between the fairings and boom beam  106 . When installed, the boom beam  406  may be divided into a sealed or unsealed leading edge chamber  906 , interior chamber  908 , and trailing edge chamber  910 . The applicable fuel system components, control surface components, and boom extension hardware and associated electrical systems are housed within the interior chamber  908  and are not shown in the various figures. 
     The second embodiment corresponding to the creation of an aerodynamic boom beam cross-sectional shape is shown in  FIG. 9B . In this embodiment, rather than attaching fairing to the existing boom beam  106 , a new boom beam  406  is created from a single piece of metal, composite, or other suitable material according to the desired cross-sectional shape. The boom beam  406  may be created as a composite supported shell structure that has a seamless, continuous exterior surface  1004 . The composite structure may be created with bulkheads  1014  for structural support, which also divides the boom beam  406  into a leading edge chamber  1006 , and interior chamber  1008 , and a trailing edge chamber  1010 . Stiffeners  1002  may also be incorporated for structural support and/or to serve as rails or supporting members for the applicable fuel system components, control surface components, boom extension hardware and/or associated electrical systems. 
     Turning now to  FIGS. 10A and 10B , an additional aerodynamic feature provided to reduce the drag associated with conventional refueling booms  104  will be described. Conventional refueling booms  104  commonly include a snubber device  1002 . The snubber device  1002  is a type of shock absorber mounted on the boom beam  106  used to engage the fuselage when the boom is stowed in order to prevent excessive collisions of the boom with the tailcone of the aircraft. The snubber device  1002  may additionally provide a preload to the refueling boom  104  that assists in deployment of the boom. 
     However, the snubber device  1002  and the interface of the device with the boom beam  106  is a source of additional drag. According to embodiments described herein, this drag is minimized utilizing a snubber fairing  1004 . The snubber fairing  1004  is an aerodynamically shaped cover that encompasses the interface between the snubber device  1002  and the boom beam  406 , as well as a portion of the snubber device itself. The snubber fairing  1004  may be shaped to conform to the aerodynamic trailing edge of the boom beam  406  shown in  FIGS. 9A and 9B . The snubber fairing  1004  may be removably attached with fasteners so that it may be removed for maintenance of the snubber device  1002 . 
     Turning now to  FIG. 11 , an illustrative routine  1100  for providing an aircraft refueling boom  404  will now be described in detail. It should be appreciated that more or fewer operations may be performed than shown in the  FIG. 11  and described herein. Moreover, these operations may also be performed in a different order than those described herein. The routine  1100  begins at operation  1102 , where a determination is made as to whether an existing refueling boom  104  is being modified to incorporate the concepts described above, or whether a new refueling boom  404  is being created. If an existing boom is being modified, then the routing  1100  proceeds to operation  1104 , where a leading edge fairing  902  and trailing edge fairing  904  are installed as described above to create the desired symmetric airfoil cross-sectional shape of the boom beam  406 . The routine  1100  continues to operation  1108  and proceeds as described below. 
     However, if at operation  1102 , a new boom beam  406  is being created, then the routine  1100  continues to operation  1106 , where the boom beam  406  is created from composite or other materials such that the exterior surface is continuous and shaped according to the desired airfoil cross-sectional shape. From operation  1106 , the routine  1100  continues to operation  1108 , where the horizontal control surfaces  410  are attached to the boom beam  406 . As discussed above, the horizontal control surfaces  410  may be one or two components, which move together or independently as an entire surface or with integrated rudders. 
     At operation  1110 , the canted vertical control surfaces  412  are attached to the opposing ends of the horizontal control surfaces  410 . It should be appreciated that this operation may occur before the horizontal control surfaces  410  have been attached to the boom beam  406 , during the creation of the horizontal control surfaces  410 , or at any time during the creation and assembly of the refueling boom  404 . The vertical control surfaces  412  are created and positioned such that the lower portion  416  extends downward towards the boom beam  406  farther than the upper portion  414  extends upwards. In doing so, the aerodynamic center  604  of the vertical control surfaces  412  is lowered to a position below the horizontal control surfaces  410 , in contrast to the configuration of conventional control surfaces  108 , resulting in the numerous advantages discussed above. From operation  1110 , the routine  1100  continues to operation  1112 , where the snubber fairing  1004  is installed around the snubber device  1002 , and the routine  1100  ends. 
     It should be understood that the routine  1100  has been greatly simplified for illustrative purposes to highlight the applicable operations associated with the concepts and technologies described above. There are numerous operations involved with creating and installing a refueling boom  404  and associated components that have not been addressed herein. 
       FIG. 12  shows an illustrative routine  1200  for controlling an aircraft refueling boom  404 . The routine  1200  begins at operation  1202 , where a determination is made as to whether a change in pitch of the refueling boom  404  is desired. This determination is made according to whether or not a control input has been received corresponding to the horizontal control surfaces  410 . If a change of pitch is not desired, the routine  1200  proceeds to operation  1206  and continues as described below. However, if a pitch control input has been received, then the routine  1200  continues to operation  1204 , where the horizontal control surfaces  410  are actuated according to the received input. As a result of this pitch control surface actuation, the pressure of the ambient airflow around the horizontal control surfaces  410  is altered accordingly, and the refueling boom  404  is moved around a pitch axis. 
     From operation  1204 , the routine  1200  continues to operation  1206 , where a determination is made as to whether an adjustment to the positioning of the refueling boom  404  around a roll axis is desired. This determination is made according to whether or not a control input has been received corresponding to the vertical control surfaces  412 . If a change of positioning around the roll axis is not desired, the routine  1200  proceeds to operation  1210  and continues as described below. However, if a roll control input has been received, then the routine  1200  continues to operation  1208 , where the vertical control surfaces  412  are actuated according to the received input. As a result of this roll control surface actuation, the pressure of the ambient airflow around the vertical control surfaces  412  is altered accordingly, and the refueling boom  404  is moved around a roll axis. 
     From operation  1208 , the routine  1200  continues to operation  1210 , where a determination is made as to whether the refueling operation is complete. If the aerial refueling has not completed, then the routine  1200  returns to operation  1202  and continues as described above. If the aerial refueling operation has completed and the refueling boom  404  is stowed, then the routine  1200  ends. It should be appreciated that the pitch and roll operations described herein may occur concurrently depending on the control input provided by the boom operator. 
     The subject matter described above is provided by way of illustration only and should not be construed as limiting. Various modifications and changes may be made to the subject matter described herein without following the example embodiments and applications illustrated and described, and without departing from the true spirit and scope of the present invention, which is set forth in the following claims.

Technology Classification (CPC): 1