Abstract:
An adaptor for mounting a refuelling hose and drogue arrangement to a refuelling boom of an aircraft is arranged to provide fluid communication between the boom and a hose of the hose and drogue arrangement. The adaptor is also arranged such that the hose is movable with respect to the boom. The adaptor includes an actuator arranged to produce a biasing force on the hose, and arranged for affecting movement to adjust the position of the hose in relation to the boom.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims the priority of United Kingdom Application No. 0906774.5, filed Apr. 20, 2009, which is incorporated herein by reference. 
     TECHNICAL FIELD 
     The present invention relates to aerial refuelling apparatus, and in particular to a refuelling apparatus for allowing selective refuelling either by means of a boom, or by means of a hose and drogue arrangement. 
     BACKGROUND 
     In previous arrangements for allowing hose and drogue refuelling from a tanker aircraft which is fitted with a refuelling boom, it has been possible to attach an adaptor to the boom, which has a hose and drogue attached thereto. Such an adaptor is known as a boom drogue adaptor. The adaptor provides fluid communication between the boom and the hose. However, the adaptor and hose/drogue can only be fitted when the aircraft is on the ground, such that the tanker aircraft must be configured either for boom refuelling or for hose and drogue refuelling during any particular flight. 
     In addition, in hose and drogue refuelling, upon engagement with the receiving aircraft, the hose develops slack as the receiver pushes the drogue towards the end of the hose which is attached to the boom, such that great care is required from the receiver aircraft to avoid excessive slack allowing the hose to whip in the air flow. This is frequently the cause of accidents. 
     In order to allow a change in configuration during flight, it has been proposed to mount a hose and drogue, attached to an adaptor, on the aircraft tail. Such an arrangement is shown in US 2006/0102791. A boom is provided which is movable during flight from a deployed position extending away from the aircraft where it can be used directly for refuelling, to a stowed position adjacent the aircraft in which it can be attached to the adaptor in the aircraft tail. In this position the hose and drogue communicates with the boom. The boom can then be extended away from the aircraft with the hose and drogue attached, which can be used for refuelling. 
     However this system has some shortcomings. Since the hose and drogue are mounted in the aircraft tail, the hose must be relatively short in order to provide sufficient ground clearance upon the aircraft taking off and landing. This leads to a lack of hose response such that high loads may be imparted to refuelling probes, and also to a smaller movement envelope for the receiver aircraft. Furthermore landings are made more difficult for the tanker aircraft because of the trailing hose. Also the problem of hose slack being created as the receiver makes contact is not addressed. 
     The present invention aims to address these problems. 
     SUMMARY 
     According to the present invention there is provided an adaptor for mounting a refuelling hose and drogue arrangement to a refuelling boom of an aircraft, the adaptor being arranged to provide fluid communication between the boom and the hose, and being arranged such that the hose is movable with respect to the boom, the adaptor comprising an actuator arranged to produce a biasing force on the hose, for affecting movement of the hose in relation to the boom. 
     With this arrangement, the adaptor may be actuated effectively to retract the hose to take up any slack in the hose when the receiver aircraft makes contact with the drogue. Furthermore, the adaptor may be actuated to move the hose to a position above the boom. Thus the hose may be longer, since the proximal end can be moved away from the ground during takeoff or landing of the aircraft. 
     For example, the adaptor may be actuatable to produce a biasing force on the hose arranged to be in a direction to counter the aerodynamic force on the hose and drogue in flight; that is in a direction generally towards the proximal end of the boom. Thus the biasing force may cause movement of the hose so as to take up any slack in the hose, particularly on contact with the receiver aircraft probe. The biasing force may conveniently be variable. 
     Preferably the adaptor is arranged to be attached to the boom at or adjacent the distal end thereof. It may comprise an arm with a fuel channel, which is pivotally mounted at one end to the boom, and at the other end to the hose. The pivot axis is preferably perpendicular to the boom. In this example, the channel is in fluid communication with the boom and the hose, and the biasing force may be torque applied at the pivotal mount. For example the actuator may comprise a motor for applying torque at the pivotal mounting between the arm and the boom, to move the arm about the pivot. 
     The invention also provides a refuelling apparatus for an aircraft comprising a boom, and an adaptor as claimed in any preceding claim for attaching the boom to a hose and drogue arrangement. The apparatus may also comprise a control system arranged to control the actuator. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       In order that the invention may be more readily understood, reference will now be made to the accompanying drawings, in which: 
         FIG. 1  is a perspective view of a boom drogue adaptor in use according to the prior art; 
         FIG. 2  is a schematic side view of a further boom drogue adaptor according, to the prior art; 
         FIG. 3  is a schematic side view of a boom drogue adaptor according to an embodiment of the invention, showing a position during flight; 
         FIG. 4  is a schematic side view of the boom drogue adaptor of  FIG. 3  showing the configuration during take off and landing; 
         FIG. 5  is a schematic side view of the boom drogue adaptor of  FIG. 3  showing a configuration during boom refuelling; 
         FIG. 6  is a schematic side view of the boom drogue adaptor of  FIG. 3  showing the configuration during hose and drogue refuelling; 
         FIG. 7  is a further schematic side view of the adaptor of  FIG. 6 ; and 
         FIG. 8  is a schematic exploded perspective view showing the adaptor shown in  FIGS. 3 to 7 , 
         FIGS. 9 ,  10  and  11  are schematic cross-sectional views of the attachment between the boom and the adaptor, and 
         FIGS. 12 and 13  show the control system for operation of the boom and the boom drogue adaptor for boom refuelling and for hose and drogue refueling respectively. 
     
    
    
     DETAILED DESCRIPTION 
     Referring to  FIG. 1 , an aircraft  2  has a refuelling boom  4  for supplying fuel therethrough. The boom  4  is telescopic, with an outer tube  3  and an inner tube  5 . The proximal end  6  of the boom  4  is attached to the underneath of the aircraft fuselage adjacent the tail  8 , such that it has a stowed position lying against the underneath of the fuselage, with the distal end  10  extending just beyond the end of the aircraft tail  8 . In use for boom refuelling, the boom  4  may be deployed downwardly to extend away from the aircraft, such that the distal end  10  of the boom may be guided onto the receiver aircraft receptacle or probe, so that the aircraft can receive fuel. 
     When it is required that the tanker aircraft  2  should supply fuel using a hose and drogue arrangement  12 , the hose  14  must be fitted to the distal end  10  of the boom  4  by an operative on the ground. An adaptor  16  is normally used for this purpose. Fuel may then be supplied via the boom  4  through the adaptor  16  into the hose  14 , and the receiver aircraft probe may be inserted into a reception coupling  18  of a drogue  20  at the distal end of the hose  14  to receive fuel. 
     It can be seen from  FIG. 1  that the hose  14  with this arrangement must be relatively short, so as to give sufficient ground clearance when the tanker aircraft  2  is taking off or landing. Also this arrangement does not provide for hose response upon receiver engagement, which can result in hose whip, and in addition it is necessary for the hose and drogue arrangement  12  to be attached or detached when the aircraft is on the ground. 
     An alternative to this arrangement is proposed in US 2006/0102791, and illustrated in  FIG. 2 . With this arrangement the boom  20  is deployable from the aircraft in a similar manner to that shown in  FIG. 1 . However, in this case the hose and drogue arrangement  22  is mounted to the tail  24  of the aircraft  26 . Thus when the boom  20  is retracted, the distal end  28  of the boom  20  may dock with an adaptor within a tail of the aircraft (not shown), such that it is connected to the hose and drogue  22 . Refuelling may then take place via the hose and drogue  22  when the boom  20  is deployed. However it can be seen from  FIG. 2  that the hose and drogue arrangement  22  of this system must still be relatively short to allow sufficient ground clearance on take off and landing, and still does not provide for hose response. 
     Referring now to  FIG. 3 , in one embodiment of the present invention, the hose and drogue arrangement  30  is connected to the distal end  32  of a boom  34  by means of a boom drogue adaptor  35  providing a linkage in the form of an arm  36 . 
     The linkage arm  36  comprises a rigid elongate member which is pivotally attached at one end  33  to the distal end of the boom  32 , and at the other end  37  to a hose  38  of the hose and drogue arrangement  30 . An actuator, described in more detail below, is provided at the one end  33  to apply a biasing force or torque at the pivotal mount. It can be seen from  FIG. 3  that, when the aircraft is in flight, the boom  34  is stowed against the underside of the aircraft. The hose and drogue arrangement  30  may then be allowed to trail directly behind the aircraft, or the actuator may lock the arm  36  is a suitable position. 
     As can be seen from  FIG. 8 , the arm  36  comprises an elongate tube, for example having an oval cross-section with a fluid channel  44  extending along the inside thereof. At the proximal end  46  of the arm  36  a first bearing  48  is provided for mounting in an aperture  50  at the distal end  32  of the boom  34 . A similar second bearing  52  is provided at the distal end  37  of the arm  36  for attachment to the proximal end  54  of the hose  38 . The first and second bearings  48 , 52  allow pivotal movement between the boom and arm, and the arm and hose respectively. 
     Referring also to  FIGS. 9 ,  10  and  11 , in each case the proximal end  46  of the arm  36  is shown together with a motor and gearbox arrangement  58  to actuate the arm  36  by applying torque. It can be seen that a fuel pipe  59  extends along the arm to cooperate with a fuel inlet, e.g.  57  in  FIG. 10 . In each case, the motor and gearbox arrangement  58  may be operated to apply a force to turn the arm  36  about the bearing  48  with respect to the aperture  50  in the boom  34 . 
       FIG. 12  shows an operating system for the adaptor within the aircraft. An aircraft mission computer  60  is in communication with a boom drogue adaptor controller  62 , and a boom refuelling system controller  64 . The adaptor controller  62  is operatively connected to the motor and gearbox arrangement  58  for actuating the arm  36 . The boom controller  64  is operatively connected to the boom for positioning the boom. 
     Referring now to  FIG. 4 , when a configuration for take off or landing is required, the computer  60  may instruct the boom controller  62  to actuate the arm  36 , by operation of the motor  58 , to pivot the arm upwardly about the first bearing  48 . 
     Thus, the arm  36  moves towards a vertical position, raising the trail axis  66  of the hose  38  above the axis  68  of the boom  34 . The controller  62  may then lock the motor in position. This configuration is suitable for take off or landing, as it raises the hose and drogue arrangement  30  away from the ground. 
     As shown in  FIGS. 5 and 12 , for boom refuelling, the computer  60  instructs the boom controller  64  to position the boom  34  for refuelling. The adaptor controller  62  actuates the motor  58  to rotate the arm  36  further about the first bearing  48  in the anticlockwise direction, moving the hose to a stowed position, and locking it there. Thus in flight the hose and drogue  30  are located above the boom  34  and clear of the distal end  32  thereafter so as to allow an aircraft  56  which is to be refuelled to use the boom  34  for refuelling. 
     Alternatively, should the aircraft  56  require hose and drogue refuelling, the mission computer  60  instructs the boom controller  64  to hold boom position. The adaptor controller  62  is instructed to move to refuel, in which condition it operates autonomously. Thus, the adaptor controller  62  uses data from the boom drogue adaptor  35  to calculate the required torque and instruct the actuator to apply torque. In the refuelling position, the bearing  48  is rotated in a clockwise direction such that the arm  36  extends below the boom  34  (see  FIGS. 6 and 13 ). In this position, a straight hose end path may be provided, and further clearance between the tanker  41  and receiver aircraft  56  is also possible. 
     Under the control of the adaptor controller  62 , torque is applied by the motor  58  to bring the hose and drogue forward against the aerodynamic drag force, for example until it is about 25° from the vertical. The torque is sufficient to rotate the arm forwardly to this point, and with any further forward movement of the arm, the torque is reduced to a lower value sufficient to keeps the hose under tension with a receiver engaged. As the receiver makes contact, the load on the drogue is reduced, and the controller  62  keeps the torque at a level which keeps the hose under sufficient tension to prevent whipping under air loads. 
     As shown in  FIG. 7 , as the receiver pulls back such that the arm exceeds 25° to the vertical in the trail direction, with the torque in the actuator maintained, the tension is increased sufficiently to cause the receiver to unlatch from the reception coupling and separate. If the receiver fails to separate, then the boom, arm and hose will stream under the tension from the reception coupling until the coupling separates from the receiver as a result of the high tension. Thus the arm  36  can effectively take up loads in the rearward direction such that they need not be resisted as torque in the system.