Abstract:
A method for operating an aircraft refueling system, where the aircraft refueling system has a computer system, a plurality of fuel tanks containing a fuel, a plurality of fuel pumps, a plurality of motor operated valves, and at least one refueling connection. The method may involve using the computer system to signal at least one of the motor operated valves to open; initiating a flow of the fuel to the at least one of the refueling connections using at least one of the pumps; sensing a flow condition of the fuel; signaling the flow condition to the computer system; and varying an operating quantity of the pumps in response to the flow condition.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application is a divisional of U.S. Ser. No. 11/313,190 filed Dec. 20, 2005, which claims priority from U.S. Provisional Application No. 60/689,666, filed on Jun. 10, 2005. The present application is generally related to subject matter disclosed in the following applications: “Shrouded Body Flow Meter Assembly”, U.S. Provisional Application 60/689,677, filed on Jun. 10, 2005; “Shrouded Valve Apparatus And Related Methods”, U.S. Utility application Ser. No. 11/150,853, filed on Jun. 10, 2005; “Redundant Seal Fitting—Fluid Carrying Apparatus”, U.S. Utility application Ser. No. 11/301,131, filed on Dec. 12, 2005; “Surge Pressure Reducing Hose Assembly”, U.S. Utility application Ser. No. 11/258,819, filed on Oct. 26, 2005; “Manifold Mounting—Load Carrying Apparatus, Infinitely Adjustable”, U.S. Utility application Ser. No. 11/440,726, filed on May 24, 2006; and “Ball Joint Assembly—Fluid Conducting Apparatus, Fully Articulating”, U.S. Provisional Application 60/689,499, filed Jun. 10, 2005. The disclosures of the above applications are incorporated herein by reference. 
     
    
     FIELD 
       [0002]    The present disclosure relates in general to refueling aircraft and more specifically to a refueling system functionally installable on a plurality of refueling aircraft platforms. 
       BACKGROUND 
       [0003]    Aircraft in flight are commonly refueled from a refueling aircraft. The refueling aircraft is typically provided with a boom mechanism or a flexible hose which trails behind the aircraft and physically makes a connection to the aircraft to be refueled. Common refueling aircraft have a plurality of wing fuel tanks and a central wing tank. Auxiliary fuel tanks can also be provided within or proximate to a fuselage of the aircraft. Fuel is commonly transferred to the boom or hose via a single wall header which is isolable by one or more shut-off valves. Common refueling systems include pumps to pressurize the fuel for transfer from one or more of the tanks, and valves which are controlled between an open and closed condition by simple on-off switches normally positioned on a refueling system panel and manually selected by a trained refueling operator. 
         [0004]    Common refueling systems require the refueling operator within the refueling aircraft to visually monitor flow and pressure indicators and communicate to the receiving aircraft whose operator/pilot can monitor fuel tank levels. The refueling operator is responsible to manually initiate and shut down the flow of fuel. Inadvertent disconnect of the refueling boom or hose can therefore occur before the receiving aircraft receives a full fuel load if an excess number of fuel transfer pumps are operated or if a pressure spike occurs. Some systems provide automatic disconnect of the refueling boom or hose upon reaching a predetermined fuel over-pressure condition. Because of the use of manual monitoring and manual shut-off of fuel flow, operation of these refueling systems also can result in overfilling of the receiving aircraft fuel tanks and subsequent relief valve discharge of fuel. 
       SUMMARY 
       [0005]    In one aspect the present disclosure relates to a method for operating an aircraft refueling system, where the aircraft refueling system has a computer system, a plurality of fuel tanks containing a fuel, a plurality of fuel pumps, a plurality of motor operated valves, and at least one refueling connection. The method may comprise: using the computer system to signal at least one of the motor operated valves to open; initiating a flow of the fuel to the at least one of the refueling connections using at least one of the pumps; sensing a flow condition of the fuel; signaling the flow condition to the computer system; and varying an operating quantity of the pumps in response to the flow condition. 
         [0006]    In another aspect the present disclosure relates to a method for operating an aircraft refueling system. The method may comprise: connecting a first wing tank and a second wing tank by a connecting header; connecting a forward auxiliary fuel tank to the connecting header; connecting a center wing tank to the connecting header; connecting a rear auxiliary fuel tank to the connecting header; using a refueling connection located remotely from the wing tanks, the forward auxiliary fuel tank, the center wing tank, and the rear auxiliary wing tank, to discharge fuel from at least one said fuel tanks through the refueling connection; monitoring a flow of the fuel out from at least one of the fuel tanks; and controlling at least one of said fuel pumps in communication with one of the fuel tanks in accordance with a monitored fuel flow in said connecting header to transfer the fuel from the one fuel tank to the refueling connection. 
         [0007]    In still another aspect the present disclosure relates to a method for operating an aircraft refueling system having a computer system, plurality of independent fuel tanks containing a fuel, a plurality of fuel pumps, a plurality of motor operated valves, and at least one refueling connection. The method may comprise: using the computer system to control a plurality of the motor controlled valves to open and close, and a plurality of the pumps to begin pumping; initiating a flow of said fuel to said at least one refueling connection using at least one of the pumps from at least one of the fuel pumps of a specified one of the fuel tanks; monitoring a flow of the fuel to the one refueling connection; and controlling operation of the motor controlled valves and the fuel pumps to redistribute a volume of fuel in the fuel tanks between selected one of the fuel tanks to balance the weight of said fuel tanks and to control a center of gravity of the aircraft. 
     
    
     
       BRIEF DESCRIPTION 
         [0008]    The present disclosure will become more fully understood from the detailed description and the accompanying drawings, wherein: 
           [0009]      FIG. 1  is a plan view of an aircraft having an air refueling system of the present disclosure; 
           [0010]      FIG. 2  is a plan view of the forward and central tank sections of the air refueling system shown in  FIG. 1 ; 
           [0011]      FIG. 3  is a is a plan view of the aft tank and fuselage sections of the air refueling system shown in  FIG. 1 ; and 
           [0012]      FIG. 4  is a plan view of the port wing of  FIG. 1  showing exemplary wing system details for an aircraft refueling system of the present disclosure. 
       
    
    
     DETAILED DESCRIPTION  
       [0013]    The following description of the various embodiments is merely exemplary in nature and is in no way intended to limit the present disclosure, its application, or uses. 
         [0014]    It is initially noted that an aerial refueling system (ARS) of the present disclosure can be installed or backfitted into a plurality of refueling or tanker aircraft designs, including but not limited to the Boeing 767, Boeing 757, KC-135 and/or KC-10 aircraft. For exemplary purposes only, the present application refers in general to installation in the Boeing 767, including structure and equipment common to that aircraft. 
         [0015]    According to one embodiment of the present disclosure and referring generally to  FIG. 1 , ARS  10  is mounted on a tanker aircraft  12  having a fuselage  14 , a port wing  16  and a starboard wing  18 . ARS  10  includes a receptacle  20  such as a universal aerial refueling receptacle slipway installation which can either receive or transfer fuel. Receptacle  20  is connected to a refueling manifold  22  which generally transfers fuel into or out of a plurality of tanks and directs the fuel to a refueling boom and/or each of a plurality of refueling hoses. 
         [0016]    A plurality of fuel tanks are provided on tanker aircraft  12  including a forward auxiliary fuel tank  24 , a center wing tank  26  separated by a front spar  28  from forward auxiliary fuel tank  24 . A rear auxiliary fuel tank  30  is separated from center wing tank  26  by a rear spar  32 . Each of the port and starboard wings  16 ,  18  include a port wing tank  34  and a starboard wing tank  36 , respectively. Fuel from any of the tanks of tanker aircraft  12  can be transferred to a refueling boom  38 , a refueling hose assembly  40 , or one of a first or second wing mounted aerial refueling pod  42 ,  44 . 
         [0017]    ARS  10  further includes a computer system  46 . Computer system  46  and associated software automatically direct the transfer of fuel from or into any of the fuel tanks and from or to any of the refueling boom  38 , refueling hose assembly  40  and/or first or second wing mounted aerial refueling pods  42 ,  44 . All valves and pumps associated with ARS  10  are also automatically controlled during normal operation using computer system  46 . Computer system  46  therefore eliminates the need for manual control of any of the features of ARS  10  during normal fuel transfer. 
         [0018]    For reference, refueling boom  38  is generally positioned and extendable from a rear of tanker aircraft  12 , and receptacle  20  is generally positioned forward of port and starboard wings  16 ,  18 . Forward and rear as used herein therefore refer generally to a forward end of tanker aircraft  12  and an aft end of tanker aircraft  12  respectively. 
         [0019]    As best seen in reference to  FIG. 2 , a double-wall manifold  48  is connected to receptacle  20  forming part of refueling manifold  22 . Double-wall manifold  48  extends rearward toward a tee  50 . A single-wall manifold  52  extends from a double wall branch of tee  50  as double-wall manifold  48  enters forward auxiliary fuel tank  24 . It is noted that double-wall manifolds are used in ARS  10  to preclude catastrophic rupture of a fuel line within a manned space of tanker aircraft  12  from disbursing fuel into the manned spaces. Generally, single wall manifolds or headers are used within tanks and in non-manned spaces of tanker aircraft  12  for ARS  10 . Single-wall manifold  52  is connected to each of a first and second hydraulically driven pump  54 ,  56 . Each of first and second hydraulically driven pumps  54 ,  56  are powered by a hydraulically driven motor. First and second hydraulically driven pumps  54 ,  56  are operated either singly or in unison to transfer fuel from forward auxiliary fuel tank  24  into refueling manifold  22 . A branch header  58  connected to single-wall manifold  52  includes a normally closed DC motor operated isolation valve  60  having a float  62 . Isolation valve  60  is provided to fill forward auxiliary fuel tank  24 . Isolation valve  60  is normally controlled by computer system  46  to open or close. In the event that fuel in forward auxiliary fuel tank  24  reaches a predetermined level, float  62  is actuated by the level of fuel which mechanically shuts isolation valve  60 , regardless of the electrical signal provided from computer system  46  to operate the DC motor of isolation valve  60 . Float  62  therefore provides a mechanical override to ensure that forward auxiliary fuel tank  24  is not over-pressurized during filling operations. 
         [0020]    As double-wall manifold  48  crosses front spar  28  it is converted to a single-wall manifold  64  within center wing tank  26 . Any fuel which discharges from the inner wall of double-wall manifold  48  upon catastrophic rupture is therefore discharged into center wing tank  26 . A normally open DC motor operated isolation valve  66  is provided immediately proximate to front spar  28  and within center wing tank  26 , to isolate single-wall manifold  64 . 
         [0021]    Four hydraulically driven pumps are provided within center wing tank  26  which are used to pump fuel out of center wing tank  26 . These include each of a third, fourth, fifth and sixth hydraulically driven pumps  68 ,  70 ,  72  and  74 . Each of the pumps  68  through  74  discharge into a common header  76  which is also a single-wall header. Common header  76  connects via a connector  78  to each of a pump discharge header  80 , isolated within center wing tank  26  by a normally open DC motor operated isolation valve  82 , (similar to isolation valve  66 ) and a common wing tank connecting header  84 . Common wing tank connecting header  84  permits flow between port and starboard wing tanks  34 ,  36  and center wing tank  26 . Isolation valve  82  is positioned within center wing tank  26  and proximate to rear spar  32  to isolate pump discharge header  80 . 
         [0022]    Referring generally now to  FIG. 3 , where pump discharge header  80  passes through rear spar  32 , pump discharge header  80  is converted to a double-wall manifold  86 . A double-wall tee  88  is provided in double-wall manifold  86  having a double-wall branch  90  connected to rear auxiliary fuel tank  30 . Within rear auxiliary fuel tank  30  double-wall branch  90  is converted to a single-wall header  92 . Single-wall header  92  is connected to each of a seventh and an eighth hydraulically driven fuel pump  94 ,  96 . Hydraulically driven pumps  94 ,  96  are similar in design and operation to each of hydraulically driven pumps  54 ,  56  and  68  through  74 . Hydraulically driven pumps  94 ,  96  are used to discharge fuel from rear auxiliary fuel tank  30  into double-wall boom manifold  86  which forms a continuous flow path with refueling manifold  22 . A branch header  98  is connected to single-wall header  92  and is isolated by a normally closed DC motor operated isolation valve  100 . Isolation valve  100 , similar to isolation valve  60 , is used to fill rear auxiliary fuel tank  30 . Also similar to isolation valve  60 , isolation valve  100  is provided with a float  102  serving a similar function which will therefore not be further discussed. 
         [0023]    From tee  88 , double-wall manifold  86  further includes a fuel flow meter  104  and a pressure transducer  106 . Fuel flow meter  104  is provided to electrically identify to computer system  46  the approximate flow rate of fuel through double-wall manifold  86 . The output signal of fuel flow meter  104  is also used by computer system  46  to identify when additional ones of the hydraulically driven pumps in the appropriate tank are operated. An additional or second flow meter (not shown), similar to flow meter  104 , can be positioned in double wall manifold  48  between tee  50  and  28  front spar  28  to improve flow measurement and determine a flow from forward auxiliary tank  24 . Pressure transducer  106  is provided to identify a pressure differential with fuel flowing in double-wall manifold  86  whose electrical output signal can be used to close a normally open DC motor operated isolation valve  108 . Pressure transducer  106  provides electrical signals to control the position of isolation valve  108  if pressure in a single-wall boom supply header  112  exceeds a predetermined value. A fuel pressure regulator  110  is also provided downstream of isolation valve  108 . Pressure regulator  110  normally maintains a predetermined pressure in supply header  112 . 
         [0024]    With continued reference to  FIG. 3 , double-wall boom manifold  86  is converted to single-wall boom supply header  112  as double-wall boom manifold  86  passes through an aircraft pressure hull  114 . Single-wall boom supply header  112  is connected to refueling boom  38  which is extended or retracted through aircraft outer aft skin  115  of tanker aircraft  12 . 
         [0025]    Between pressure transducer  106  and isolation valve  108 , a double-wall manifold  116  branches off of double-wall manifold  86 . Double-wall manifold  116  connects to a hose reel enclosure  119  which contains refueling hose assembly  40 . Within the hose reel enclosure  119  a normally closed DC motor operated isolation valve  118  isolates a single-wall header  117  from double-wall manifold  116 . A hose reel control motor  120  is used to operate refueling hose assembly  40  for extending or retracting the associated refueling hose. 
         [0026]    Also provided within pressure hull  114  and connected to double-wall manifold  86  is a double-wall manifold  122  isolated by a normally closed DC solenoid operated isolation valve  124 . Isolation valve  124  is opened by computer system  46  after operation of refueling boom  38 . The purpose for double-wall manifold  122  and isolation valve  124  is to permit back flow of fuel to center wing tank  26  which is necessary when refueling boom  38 , which is filled with fuel, is retracted into tanker aircraft  12 . The excess volume of fuel within the boom supply header  112  is thereby allowed to flow back into center wing tank  26  through double-wall manifold  122 . For similar purposes, a single-wall header  126  isolated by a normally closed DC solenoid operated isolation valve  128  is provided in hose reel enclosure  119  connected to single-wall header  117 . When the hose of refueling hose assembly  40  is retracted, the excess fuel within the hose is allowed to transfer back through single wall header  117  and into double-wall manifold  122  toward center wing tank  26 . Isolation valve  128  is therefore automatically opened by computer system  46  when refueling hose assembly  40  is retracted. 
         [0027]    Referring generally now to  FIG. 4 , the portions of ARS  10  associated with port wing  16  are shown. Because the portions of ARS  10  associated with starboard wing  18  are a mirror image of port wing  16 , only the details of port wing  16  will be discussed. From common wing tank connecting header  84  in center wing tank  26 , a normally open DC motor operated isolation valve  130  is provided to isolate port wing tank  34  from center wing tank  26 . A normally closed DC motor operated isolation valve  134  is provided within center wing tank  26 , adjacent port wing tank  34 , to provide fuel inlet flow to fill center wing tank  26 . A float  136  similar in function to float  62  is provided to prevent over-filling center wing tank  26  by mechanically closing isolation valve  134 . A normally closed, DC motor operated drain isolation valve  138  is provided within port wing tank  34  and connected to a fuel tank drain riser  140 . Fuel in port wing tank  34  is drained by gravity flow via fuel tank drain riser  140  into center wing tank  26 . Computer system  46  controls the open or shut position of isolation valve  138  (and its counter-part starboard wing tank isolation valve) to maintain a balanced volume of fuel in each of the port and starboard wing tanks  34 ,  36 . Computations performed by computer system  46  are therefore used to determine the open or shut position of isolation valve  138 . 
         [0028]    A pair of first and second wing tank fill isolation valves  141 ,  142  are each normally closed, DC motor operated valves. First and second wing tank fill isolation valves  141 ,  142  are provided to fill port wing tank  34 . A pair of valves is used for redundancy. First and second floats  144 ,  146  are provided for each of first and second wing tank fill isolation valves  141 ,  142  respectively, operating similar to float  62 , to prevent overfill or over-pressurization of port wing tank  34 . Each of first and second wing tank fill isolation valves  141 ,  142  are connected by piping into wing fuel manifold  132 . 
         [0029]    A normally closed fuel pod isolation valve  148  (and a similar counter-part in starboard wing tank  36 ) is provided to isolate first wing mounted aerial refueling pod  42  (or second wing mounted aerial refueling pod  44 ). Fuel pod isolation valve  148  is controlled by a DC motor  150  which in turn is controlled by computer system  46 . Isolation valve  148  is opened when fuel is transferred using first wing mounted aerial refueling pod  42 . First wing mounted aerial refueling pod  42  (and its counter-part second wing mounted aerial refueling pod  44  on starboard wing  18 ) each have a turbine  152  which rotates a ram air turbine assembly  154 . Ram air turbine assembly  154  provides additional power to operate a hose reel motor  156  and also as necessary to boost the fluid pressure in the hose as it extends from a hose reel  158 . A common refueling hose connector  160  is provided at a distal end of the hose extended by hose reel  158  to connect to an aircraft to be refueled. 
         [0030]    In the event that tanker aircraft  12  needs to land before delivering its full load of fuel, fuel can be jettisoned to reduce the landing weight of tanker aircraft  12 . A fuel jettison line  162  is therefore provided which is connected into wing fuel manifold  132  for discharging excess fuel during this operation. A normally closed DC motor operated isolation valve  164  is provided to permit fuel discharge via fuel jettison line  162 . Isolation valve  164  is similarly controlled by computer system  46  and can also be manually selected (for example by a switch at a refueling panel, not shown) to open for this operation. 
         [0031]    As noted herein, ARS  10  is capable of receiving a maximum fuel load from a KC-10, KC-135, or Boeing 767 Tanker Transport. A minimum on-load rate of 900 gpm is available using current air refueling procedures. ARS  10  uses a Universal Aerial Refueling Receptacle Slipway Installation (UARRSI), designated as receptacle  20 , located on the fuselage  14 . The five inch shrouded or double wall manifold  48  is routed from receptacle  20  to the ground refueling manifold inside the forward auxiliary tank  24 . 
         [0032]    The ability to manually control the loading of fuel or moving fuel between tanks using hydraulically driven pumps is an advantageous feature of ARS  10 . Fuel can also be directed to/from any tank individually or simultaneously. Reverse air refueling operation of the tanker aircraft can also be accomplished via manual control of valves and pumps while in a “receiver mode”. Reverse air refueling through a boom of another aircraft can also be accomplished in receiver mode. The wing isolation valves and fuel level control valves must be manually closed via ARS  10 , meaning a switch for each of the valves is manually thrown to shut the valves, over-riding computer control of these valves. During reverse air refueling, the pumps must also be manually operated via ARS  10 , meaning a switch for each of the pumps is manually thrown to actuate or shut off the pump, over-riding computer control of the pumps. 
         [0033]    The gravity drain portion of ARS  10  allows fuel to be transferred between the main port and starboard wing tanks  34 ,  36  and the center wing tank  26 . The 767 aircraft refueling system uses for example a 3 inch manifold penetrating a rib, and a line mounted butterfly valve to control the flow. An actuator for the line mounted butterfly valve is mounted on rear spar  32  using an ITT Corporation adapter and motor. A shaft with U-joints connects the adapter to the valve body. An upturned end of the manifold, fuel tank drain riser  140 , which acts as a standpipe, limiting the amount of fuel that can be drained from any individual wing tank. 
         [0034]    The wing isolation valve(s)  130  is a normally open valve that is closed in the event of a catastrophic failure of any portion of the wing fuel manifold  132 . Isolation valve  130  is for example, a 3 inch valve installed in the wing fuel manifold  132  acting as a ground refuel/pod supply manifold. An actuator for isolation valve  130  (not shown) is mounted on the rear spar  32  also using an ITT Corporation adapter and DC motor. A shaft with U-joints connects the adapter to the valve body. The manifold provides support for the valve, thus no additional brackets are needed. The same three inch valve design is used in both gravity drain and wing isolation applications. This valve is commonly used in the same application (wing isolation) on the KC-135 refueling aircraft. The ITT adapter and motor is similar to that used on the 767 fuel jettison system. 
         [0035]    A “core” ARS  10  refueling system includes the hydraulically driven refueling pumps and associated manifolds and valves. The placement of the center wing tank pumps  68 - 74  permit the center wing tank  26  to be pumped down to a reserve volume of approximately 600 gallons. The manifold sizes used are 3, 4 and 5 inch OD, and made for example of welded aluminum piping. The double-wall manifolds are disclosed in U.S. Pat. No. 6,848,720, commonly owned by the assignee of the present disclosure, the subject matter of which is incorporated herein by reference. The manifolds are typically attached to aircraft structure via tie rods and/or brackets. Exemplary manifold end connections are Wiggins AW2020 series, or similar designed flanged connections. The core system extends forward to where the receiver manifolds attach and aft to where the boom manifolds attach. The core system can also interconnect with a “green” aircraft ground refueling manifold. 
         [0036]    The drain isolation valves  138  are installed in a span-wise beam. These valves permit a greater volume of fuel to flow to the center wing tank pumps than the aircraft structure would normally allow. Drain isolation valves  138  direct one-way flow toward the aft end of center wing tank  26  to preclude the fuel from loading the front spar  28  in a 9 g forward event. 
         [0037]    The Universal Aerial Refueling Slipway Installation (UARRSI) or receptacle  20  is secured via tool located fasteners in a pressure box located in the upper part of the 767, in section 41. An electrical actuator (not shown) is installed aft of the receptacle pressure box and is connected to the receptacle. A seal (not shown) is installed on an actuator shaft where is passes through the pressure box. A manual override cable (not shown) is routed parallel to the manifold down to an access panel above where the manifold penetrates the main deck. 
         [0038]    The receptacle  20  further includes both hydraulic and electrical systems. A drain tube is connected to the bottom of the pressure box and is routed to the lower lobe and connected to a drain mast. A pressure disconnect transducer (not shown) is installed in the manifold immediately down-stream of receptacle  20 . ARS  10  also controls the disconnect transducer. 
         [0039]    ARS  10  further permits tanker aircraft  12  to be refueled while in the air. An interconnect manifold installed as part of the core fuel system allows pressurized fuel to enter a separate ground refuel system from the ARS  10  system. This pressurized fuel can come from the receptacle  20  or from other tanks such as forward and/or rear auxiliary fuel tanks  24 ,  30  using the hydraulically driven pumps in the tanks. 
         [0040]    Common header  76  is for example a 5 inch OD pipe which interfaces the core fuel system in the center wing tank  26 . Common header  76  routes forward through the span-wise beams to the front spar isolation valve  66 . Front spar isolation valve  66  is a 5 inch valve with an actuator installed on the front spar  28  outside the center wing tank  26 . Common header  76  passes through the front spar  28  and becomes for example 5 inch shrouded or double-wall manifold  48 . Double-wall manifold  48  traverses on the 767 aircraft to the left or port side of tanker aircraft  12  and turns forward and attaches to aircraft stanchions. Double-wall manifold  48  then routes through a lower cargo compartment along the stanchions until it reaches the electrical bay. Double-wall manifold  48  then passes through a fitting in the main deck floor and up into section  41 . Double-wall manifold  48  then routes up a side of the fuselage  14  and traverses forward to the receptacle  20  and probe connections. Double-wall manifold  48  in section  41  is supported for example by tie rods. 
         [0041]    When acting as a receiver system, ARS  10  also provides redundant shutoff capability to the existing fuel level control valves. The existing level control valves are replaced with new level control valves, identified as isolation valves  141 ,  142  that include provisions for attaching a pilot control line. Level control/isolation valves  141 ,  142  are otherwise identical to the existing valves in every other way. The pilot flow, which is normally returned to the associated port or starboard wing tank  34 ,  36  is routed to a pilot valve, identified as first and second floats  144 ,  146  via a control line. In flight, the first and second floats  144 ,  146  serve as a redundant shutoff for the fuel level control valves, isolation valves  141 ,  142 . The pilot flow from each isolation valve  141 ,  142  is returned to its associated wing tank  34 ,  36  and operates normally as long as the first and/or second floats  144 ,  146  are open. Ground refueling orifice tubes (not shown) are also replaced with units previously designed for right hand fill optioned aircraft. This permits equal filling of port and starboard wing tanks  34 ,  36  in flight. 
         [0042]    The first and second floats  144 ,  146  are installed at a level in port and starboard wing tanks  34 ,  36  above a two percent (2%) ullage space to prevent activation when tanker aircraft  12  is on the ground. In the event that the fuel quantity indication system (FQIS) does not shut off level control/isolation valves  141 ,  142 , fuel will fill the port or starboard wing tank  34 ,  36  to the level of the first and/or second floats  144 ,  146 . Fuel will then mechanically close first and/or second floats  144 ,  146  regardless of the electrical signal directing the position of level control/isolation valves  141 ,  142 . 
         [0043]    ARS  10  incorporates a built-in test before each air refueling operation. The system uses a pre-check of a solenoid connected to a ground refuel manifold to direct fuel to the float line. The fill rate from the pre-check valve is higher than the drain rate of the float line causing the float to rise. This causes the fuel level control/isolation valve to close. ARS  10  detects the un-commanded valve closure thus confirming the redundant shutoff system is functional. 
         [0044]    The wing portions of ARS  10  supply fuel to the wing mounted aerial refueling pods  42 ,  44 . ARS  10  can also open an existing fuel jettison manifold. To supply fuel to either of the refueling pods  42 ,  44 , fuel is pumped from the center wing tank  26  through common header  76  into the common wing tank connecting header  84  (part of the core fuel system). 
         [0045]    An articulated duct allows movement between single wall boom supply header  112  and aircraft structure. Single wall boom supply header  112  then travels outside the skin, while inside a boom fairing, to a boom flexible interconnect and then to the boom  38  itself. 
         [0046]    The solid state pressure transducer  106  is supplied for example by Kulite Semiconductor Corporation and is installed in the flow path of boom manifold  86 . Fuel pressure regulator  110  is installed in boom manifold  86  aft of pressure transducer  106  and isolation valve  108 . Fuel pressure regulator  110  is a mechanical device that limits the fluid pressure in refueling boom  38  to approximately 65 psig. Fuel pressure regulator  110  operates by sensing a differential pressure and uses this differential pressure to operate a flow control valve (not shown) positioned inside fuel pressure regulator  110 . 
         [0047]    ARS  10  also includes an aerial refueling leak detection system, which provides both active and passive fuel leak systems to mitigate failures. This system portion meets FAA regulations. The aerial refuel manifold leak detection system is an active, redundant system designed to provide the aircrew real-time detection of a contained catastrophic leak. The system also provides a passive leak detection system for pre and post flight ground checks of smaller leaks as well as troubleshooting. 
         [0048]    For the active system, the refueling manifold  22  is double walled within the pressure vessel. Pressure activated switches (not shown) are installed on the outer manifold and react to pressure changes in interstitial spaces between the tubes of the double wall manifolds. A catastrophic leak of the inner manifold, caused by a ruptured tube or failed o-ring, causes the interstitial space to become pressurized during refueling operations. The switches are set to 30±5 psig. Pressures above this trigger the leak detection system. The outer manifold is also designed to operate at full system pressure. Each isolated section of the refueling manifold (four to six manifold sections) includes two switches for redundancy. 
         [0049]    The passive portion of the leak detection system includes a series of drains (not shown) connected to the interstitial spaces in the refueling manifold. The drains are connected to the bottoms of each isolated section and run to overboard drains near the bottom of fuselage  14 . These drains are checked pre and post flight. The drains have visual indicators at the manifolds to aid in trouble shooting if a leak is detected at the fuselage drains. Each isolated section of the refueling manifold  22  (four to six manifold sections) will drain at the lowest ground attitude point. 
         [0050]    The ARS  10  system is separate from and can stand alone from the aircraft fuel system and may be operated at all stages of flight within the flight envelope. The ARS  10  operation is designed to reduce crew workload and makes mission controls and displays available to both pilots and the mission systems operator(s). 
         [0051]    For example only, the 767 Tanker ARS  10  system is capable of the following performance:
       Boom offload rates of 900 gallons per minute minimum at 50 psig continuously;   Centerline hose and drogue offload rates of 600 gallons minimum per minute at 50 psig continuously; and   Two wing mounted refueling pods offload simultaneously at rates of 400 gallons per minute minimum at 50 psig continuously.
 
System performance for other aircraft and modified 767 aircraft can vary from the values given above, depending on the piping size(s), pump characteristics, valve designs, and the like selected by the designer.
       
 
         [0055]    ARS  10  can operate any one or a combination including up to all four fuel pumps in center wing tank  26 . A seven (7) second (maximum) delay is incorporated into the system between the start of each successive pump. Each pump has a three (3) second start-up time to minimize fuel pressure transient loads on both the tanker aircraft  12  and receiver fuel system. This is a mechanical limit and is not software controlled. 
         [0056]    ARS  10  will command a pump on and wait up to seven seconds for an indication (via pressure switch on the pump). The next pump in line is then commanded on upon closure of the pressure switch which could be in as little as three (3) seconds. Should ARS  10  fail to receive a closed indication signal within seven seconds, the pump in question is flagged as failed and the next pump selected. 
         [0057]    The ARS  10  system also selects an appropriate number of operating pumps for a specific aircraft to be refueled. The fuel off-load is sequenced to keep tanker aircraft  12  with a predetermined center of gravity (CG) envelope. The AR pumps and tank levels are controlled to preclude tanker aircraft  12  from being put into an out of CG condition during air refueling operations. The system architecture enables all aircraft fuel to be available for offload (except for reserve fuel) with no degradation to offload rate throughout the range of tanker fuel loads. 
         [0058]    ARS  10  uses for example hydraulically driven Argo-Tech 6161-27 refueling pumps, four in center wing tank  26  to pump fuel from the center and wing mains and two in each of the auxiliary tank systems. A flame arrestor (not shown) is installed in the inlet to meet FAA requirements. ARS  10  commands the fuel pumps on only after a “contact made” signal is received. This signal is acquired from either the boom or from the pod/hose and drogue unit (HDU). The signal from the boom is sent as long as the boom is plugged into a receptacle. The signal from the pod or HDU is sent as long as the receiver is in the proper fuel range. Any time a contact made signal is lost, all of the fuel pumps are shut down. In the case of the Boom or HDU, the boom fuel return valve and manifold pressure relief valves also open. 
         [0059]    The fuel pumps of the forward and rear auxiliary fuel tanks  24 ,  30  (body tanks) discharge directly to the refueling manifold  22 . Fuel is therefore not dumped into center wing tank  26 . Center wing tank fuel is also discharged directly to refueling manifold  22 . Fuel from the wing tanks  34 ,  36  is gravity drained to the center wing tank  26  and then pumped into the refueling manifold  22 . Fuel may be directed from the refueling manifold  22  into the common wing tank connecting header  84  from any tank (wing fuel still must be drained into the center tank first). 
         [0060]    ARS  10  seeks to maintain a pressure of 60 psig downstream of the fuel pressure regulator  110  to limit surge pressures independent of the number of pumps required by a specific receiver type. If the pressure upstream of the fuel pressure regulator  110  exceeds 73 psig for 30 seconds, ARS  10  will shut down a fuel pump. ARS  10  will restart a pump only if the system pressure drops back below 50 psig for 30 seconds. 
         [0061]    The gravity drain system allows fuel from the port and starboard wing tanks  34 ,  36  to be drained into the center wing tank  26 . Stand pipes prevent the wings from being drained below a predetermined value. ARS  10  commands the gravity drain isolation valves open any time the required offload exceeds the fuel available in the center wing tank and the auxiliary tanks are empty. The system seeks to maintain an appropriate fuel volume in each wing tank to minimize wing bending loads. 
         [0062]    The air refueling system of the present disclosure offers several advantages. A computer system automatically controls the selection and operation of any number of pumps during fuel transfer, eliminating the need to manually monitor fuel flow and pressure and manually adjust the number of operating pumps. Electrically operated valves are also provided which are automatically controlled by the computer system, for automatically isolating or opening one or more flow paths. The ability to manually control the loading of fuel or moving fuel between tanks using the pumps is also an advantageous feature of ARS  10 . Fuel can be directed to/from any tank individually or simultaneously. Reverse air refueling operation of the tanker aircraft can also be accomplished via manual control of valves and pumps while in receiver mode. Reverse air refueling through a boom of another aircraft can also be accomplished in receiver mode. 
         [0063]    While various embodiments have been described, those skilled in the art will recognize modifications or variations which might be made without departing from the inventive concept. The examples illustrate the invention and are not intended to limit it. Therefore, the description and claims should be interpreted liberally with only such limitation as is necessary in view of the pertinent prior art.