Abstract:
A ducted fan air vehicle and method of operation is disclosed for obtaining aerodynamic lift and efficiency in forward flight operation without significantly impacting hover stability. One or more retractable wings are included on the ducted fan air vehicle and are deployed during forward flight to provide aerodynamic lift. The wing or wings are retracted when the vehicle hovers to reduce the impact the wings have on stability in a wind. Each wing may conform to the curvature or profile of the vehicle when retracted, and may be constructed in one or more wing sections. The wing or wings may be deployed and retracted automatically or at the command of an operator. Each wing and related components may be integrated into the vehicle or may be detachable.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    The present patent application claims priority under 35 U.S.C. § 119(e) to U.S. Provisional Patent Application Ser. No. 60/915,542, filed on May 2, 2007, the entirety of which is herein incorporated by reference. 
     
    
     FIELD OF INVENTION 
       [0002]    The present application relates to ducted fan air vehicles, and more particularly, to a deployable wing system for such vehicles. 
       BACKGROUND 
       [0003]    A conventional ducted fan vehicle contains one or more motor-driven impellers to generate propulsive force and a means of directing that propulsive force, such as one or more vanes. By controlling the magnitude and direction of the propulsive force, ducted fan vehicles are capable of performing a wide variety of flight maneuvers, including forward flight and hovering. However, ducted fan vehicles have very limited aerodynamic lift in forward flight. The propulsive force provides most of the lift and also provides the thrust to propel the ducted fan vehicle forward. Reliance on the propulsive force to provide both lift and forward thrust limits the range and endurance of the vehicle, and tends to make the vehicle inefficient in forward flight. 
       SUMMARY 
       [0004]    The present application is directed to ducted fan air vehicles and a means of improving forward-light efficiency without disrupting stability while in a hover. One or more retractable wings are deployed to provide aerodynamic lift in forward flight. Either automatically or in response to a command from an operator, the wing or wings can be retracted to return the ducted fan vehicle to an aerodynamic profile that is more stable in a hover. In one embodiment, a servo motor assists in the deployment and retraction of the wings. In another embodiment, the wings are comprised of more than one piece such that the wings follow the contour of the vehicle while in the stowed position. In yet another embodiment, the wings are detachable from the vehicle. 
     
    
     
       BRIEF DESCRIPTION OF FIGURES 
         [0005]      FIG. 1  shows a perspective view of a ducted fan air vehicle in accordance with a first embodiment. 
           [0006]      FIG. 2  shows a perspective view of a ducted fan air vehicle in accordance with a second embodiment. 
           [0007]      FIG. 3  shows a perspective view of the ducted fan air in forward flight operation. 
           [0008]      FIG. 4  shows a perspective view of the ducted fan air vehicle in a hover operation. 
           [0009]      FIG. 5  shows a sequence of perspective views of the ducted fan air vehicle transitioning from the hover operation to the forward flight operation. 
           [0010]      FIG. 6  shows a sequence of perspective views of the ducted fan air vehicle transitioning from the forward flight operation to the hover operation. 
       
    
    
     DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS 
       [0011]    Many traditional aircraft utilize a fixed lifting surface to provide lift in forward flight. However, when a ducted fan vehicle hovers, the aerodynamic profile of the vehicle has a significant impact on the stability of the vehicle, especially when a wind is present. Thus while attaching a fixed lifting surface to the ducted fan vehicle may improve efficiency in forward flight, a fixed lifting surface typically has a detrimental affect on the hover stability of the vehicle in a wind. 
         [0012]      FIG. 1  shows a perspective view of a ducted fan air vehicle  100  in accordance with a first embodiment. The air vehicle  100  includes a body portion  101  comprising a frame  102  to which a motor  103  is attached. The motor  103  drives an impeller  104  to provide propulsion for the air vehicle  100 . A plurality of vanes  105  can be used in cooperation with the impelled air to provide steering capabilities for the body portion  101 , such as by remote control or by a preprogrammed flight plan. The motor  103  may be powered by electrical energy, a gas-fueled engine or other appropriate means of generating mechanical energy. Control of the motor  103  may be exercised remotely or via pre-programmed instructions. 
         [0013]    The air vehicle  100  also includes one or more retractable wings  106 ,  107 . In the embodiment illustrated in  FIG. 1 , two wings  106 ,  107  are shown. For simplicity, only one of these wings will be described. The wing  106  is shown at three separate times. The wing  106  at a first time instant  108  is shown in a stowed or retracted configuration. At a second time instant  109 , the wing  106  is shown at an intermediate semi-deployed position, between a stowed, retracted configuration and a deployed configuration. Finally, at a third time instant  110 , the wing  106  is shown in a fully deployed position. The wing  106  will typically be in either a stowed configuration or a fully deployed configuration. When in a retracted position, the wings  106 ,  107  may be positioned adjacent to the perimeter of the body  101 . However, other retracted positions may provide the desired aerodynamic properties in light of the overall design of the vehicle  100 , the body shape  101 , and/or the shape of the wings  106 ,  107 . 
         [0014]    One or more stopping means, such as a mechanical stop  111  can be included in or on the body portion  101 , or as part of the base of the wings  106 ,  107 , to hold the wings  106 ,  107  open at a desired position, such as a predetermined angle relative to the body portion  101 . When the wings  106 ,  107  are deployed, the wings,  106 ,  107  can be held against the mechanical stop  111  by the aerodynamic forces experienced by the wings  106 ,  107 . 
         [0015]    In addition, one or more retraction servos  112  may be included to retract the wings  106 ,  107  and/or to deploy the wings  106 ,  107 . The retraction servos  112  may be any type of servo mechanism, or a device used to provide control of the position of the wings  106 ,  107 . Generally, an electric servo motor is used to create mechanical force to move the wings  106 ,  107 . However, other types of servos may be used as well, including, but not restricted to, mechanisms using hydraulic, pneumatic, or magnetic principles. 
         [0016]    Deployment of the wings  106 ,  107  is preferably only initiated by the servo  112 , with the resultant air load providing force to fully open the wings. The servo  112  should be able to supply enough force to stow the wing(s)  106 ,  107  when the air vehicle  100  is in a hover. This force will be relatively low in a hover, since the wings  106 ,  107  will not be providing any significant lift to the air vehicle  100  during that time period. 
         [0017]    The wings  106 ,  107  are attached to the body  101  through a hinge or other mechanical pivoting mechanism  113  to allow the wings to rotate outward from the body  101  of the air vehicle  100 . For example, a first end of the wing  106  would be attached to a hinge  113  on the body  101 , so that a second end of the wing can be extended outward and away from the body  101 . 
         [0018]      FIG. 2  shows a perspective view of a ducted fan air vehicle  200  in accordance with a second embodiment. The air vehicle  200  includes a body portion  201  comprising a frame  202  to which a motor  203  is attached. Propulsion for the air vehicle  200  is provided by an impeller  204  which is driven by the motor  203 . In conjunction with the impelled air, a plurality of vanes  205  can be used to provide steering capabilities for the body portion  201 . Steering and other movements can be controlled remotely, or by a preprogrammed flight plan. The motor  203  may be powered by electrical energy, a gas-fueled engine or other appropriate means of generating mechanical energy. Remote control or preprogrammed instructions can be used to control the motor  203 . 
         [0019]    The air vehicle  200  also includes one or more retractable wings  206 ,  207 . In the embodiment illustrated in  FIG. 2 , two wings  206 ,  207  are shown. For simplicity, only one of these wings will be described. The wing  206  is shown at three separate time instants. At a first time instant  208 , the wing  206  is shown in a stowed or retracted configuration. At a second time instant  209 , the wing  206  is shown at a semi-deployed position, between a stowed, retracted configuration and a deployed configuration. At a third time instant  210 , the wing  206  is shown in a fully deployed position. Typically, the wing  206  will be in either a retracted configuration or a fully deployed configuration. When in a retracted position, the wings  206 ,  207  may be positioned adjacent to the perimeter of the body  101 . However, other retracted positions may provide the desired aerodynamic properties in light of the overall design of the vehicle  100 , the body shape  101 , and/or the shape of the wings  206 ,  207 . 
         [0020]    Retractable wings  206 ,  207  for the air vehicle  200  differ from those of the air vehicle  100 , in that each wing  206 ,  207  comprises two portions  211 ,  212  (e.g. portions having a radius of curvature approximating that of the body  202 ). This allows the deployed wings to have a greater surface area to provide improved lift, while maintaining similar hover characteristics while the wings are retracted to those of the air vehicle  100 . 
         [0021]    Retractable wings  206 ,  207  are hinged, or otherwise movably connected, to one another. As shown in  FIG. 2 , a hinge  213  can be included between the two portions  210 ,  211 . While in forward flight, the aerodynamic load experienced by the wing portions  210 ,  211  can hold the wing portions  210 ,  211  in a deployed position. If the wings  206 ,  207  are sufficiently long such that they overlap while in a retracted position, the wings  206 ,  207  can be retracted and deployed sequentially. 
         [0022]    A mechanical stop  214  and retraction servo  215  can also be included in the air vehicle  200  to deploy the wings  206 ,  207 , maintain the position of the wings  206 ,  207  with respect to the vehicle body  201 , and retract the wings  206 ,  207  described with respect to the air vehicle  100  in  FIG. 1 . 
         [0023]      FIG. 3  shows a perspective view of an example ducted fan air vehicle  300  in forward flight operation. The air vehicle  300  is shown in forward flight with the wings  301  fully deployed. As shown in  FIG. 3 , the air vehicle  300  is moving to the left. 
         [0024]    The vehicle  300  includes a body section  302 , an impeller  304  and a motor  305 . The motor  305  drives the impeller  304  to generate a propulsive force. Typically, the motor is driven by electrical power or a gasoline-fueled engine, though any method of generating mechanical energy is appropriate. Control of the motor can be exercised by remote control, or through preprogrammed instructions. The propulsive force from the impelled air is directed by one or more vanes  306  to enable a variety of flight maneuvers. Control of the vanes  306  can also be exercised by remote control or through preprogrammed flight instructions. 
         [0025]    The wings  301  follow the general radius and curvature of the body  302  of the vehicle  300 . When deployed, the wings  301  provide lift while the vehicle is moving forward, reducing the proportion of the force from the impeller  304  directed towards creating lift, and enabling more force from the impeller  304  to be directed towards forward flight. 
         [0026]      FIG. 4  shows a perspective view of the ducted fan air vehicle  300  in hover operation. The vehicle  300  is shown in hover with the wings  301  partially retracted. 
         [0027]    The wings  301  possess a profile  307  such that when the wings  301  are fully deployed and the vehicle  300  is in forward flight, the wings  301  provide lift. The wing profile  307  is only one appropriate profile, and persons of ordinary skill in the art will recognize that any wing profile that provides the desired aerodynamic properties is appropriate. The wings  301  themselves possess a shape and a curvature that generally conforms to the shape of the body  302  of the vehicle  300 . For example, as shown in  FIG. 4 , the wings  301  may be have a semi-circular shape. 
         [0028]    However, the wing shape depicted in  FIG. 4  represents only one embodiment, and alternate wing shapes that provide the desired aerodynamic profile when in a retracted position may also be implemented. 
         [0029]    When hovering, the wings  301  will typically be in a retracted position, while the motor  305  drives the impeller  304  to lift the air vehicle  300  in a vertical fashion. The vanes  306  direct the impelled air to allow for a variety of flight maneuvers while hovering. The wings  301  are retracted during the hover operation to provide less resistance to the movement of the vehicle  300  and increase the stability of the hover. 
         [0030]      FIGS. 5A-C  show perspective views of the ducted fan air vehicle  300  in operation transitioning from the hover operation to the forward flight operation. 
         [0031]    At a first time shown in  FIG. 5A , the vehicle  300  is in a hover position, with the wings  301  stowed in a retracted position. The motor  305  drives the impeller  304  to generate a propulsive force. A plurality of vanes  306  directs the force downward, creating lift and allowing the vehicle  300  to hover. 
         [0032]    At a second time shown in  FIG. 5B , the wings  301  are in the process of deploying. During deployment of the wings  301 , the vehicle  300  tips forward such that the propulsive force generated by the motor  305  and the impeller  304  provides lift for the vehicle  300  in conjunction with the lift provided by the wings  301 . Deployment of the wings  301  is initiated by servo motors and is further aided by the air pressure experienced by the wings  301  during deployment. 
         [0033]    At a third time shown in  FIG. 5C , the wings  301  are fully deployed, and the vehicle  300  is in forward flight (e.g., moving to the right as shown in  FIG. 5C ). In this configuration, the wings  301  provide lift for the vehicle  300 , and the propulsive force generated by the motor  305  and impeller  304  primarily provides forward thrust. The direction of the vehicle  300  is controlled primarily by a plurality of vanes  306 , which can change orientation to provide the desired change in direction of the vehicle  300 . 
         [0034]      FIG. 6  shows a perspective view of the ducted fan air vehicle  300  in operation transitioning from forward flight operation to the hover operation 
         [0035]    At a first time as shown in  FIG. 6A , the vehicle  300  is beginning the transition from forward flight to hover. The wings  301  are in a fully deployed position, and the body of the vehicle  300  is beginning to move into an upright position. In this configuration, the deployed wings  301  provide air braking to assist the vehicle  300  in transitioning from forward flight to hover. 
         [0036]    At a second time as shown in  FIG. 6B , the vehicle  300  is in a hover and has commenced moving the wings  301  into a retracted position. In this configuration, there is little or no air load on the wings  301  and servo motors can be used to move the wings  301  into a retracted position. 
         [0037]    At a third time shown in  FIG. 6C , the wings  301  are stowed in a retracted position, and the vehicle  300  is in a hover. 
         [0038]    In general, the wings  301  will typically be stowed while the air vehicle  300  is in a hover, in order to improve stability characteristics (e.g. with regard to winds). The wings  301  will generally be deployed during forward flight (e.g. other than hover flight), in order to improve aerodynamic lift and efficiency. The wings  301  and other aspects of the design may be optimized for a particular speed of travel. 
         [0039]    Deployment and retraction of the wings  301  can be implemented automatically based on the airspeed of the vehicle  300 . The wings  301  could automatically be deployed based on exceeding a given speed threshold based on where the wings  301  become effective. Retraction could occur when the vehicle  300  has slowed to where the wings  301  are no longer effective and where minimal retraction force would be required. These speeds could be determined empirically, for example. 
         [0040]    Design details for a retractable wing will depend on the characteristics of the air vehicle itself (e.g. size, shape, propulsive capabilities of the motor). For example, the wings could be constructed using two layers glass with a carbon stiffener, and formed in a shape that approximates a profile of the air vehicle itself. However, persons of ordinary skill in the art will recognize that the wings can be constructed from a wide variety of materials and formed in any shape that provides the desired aerodynamic properties. 
         [0041]    In some situations, such as when operation of the air vehicle includes minimal non-hover flight, increased forward-flight efficiency provided by wings may not overcome the loss in efficiency due to the additional weight of the wings. In an example implementation, the associated additional weight is avoided by using the deployable wing only when the operation of the air vehicle includes distance requirements. In such a case, the wing would be used as a temporary attachment to the vehicle, as called for by a desired operation. 
         [0042]    While the wings illustrated in  FIGS. 1-6  are generally round in shape, with a radius of curvature similar to that of the body of the air vehicle, this is an example implementation only. Other implementations, such as those utilizing a wing that straightens upon deployment, could alternatively be utilized. 
         [0043]    The applications to which present embodiments may apply are not limited to the examples described above. While example applications for the air vehicles include operations in which the air vehicle glides or flies to its target location, the present application may provide benefits to other uses as well. Using the present embodiments, aerodynamic lift, and thus efficiency can be improved without significantly affecting hover stability in a wind. 
         [0044]    While examples have been described in conjunction with present embodiments of the application, persons of skill in the art will appreciate that variations may be made without departure from the scope and spirit of the application. The true scope and spirit of the application is defined by the appended claims, which may be interpreted in light of the foregoing.