Abstract:
A system for airborne transport of flammable liquids with an aircraft. A fuel tank and a reservoir, each for storing flammable liquids, are joined to the aircraft. A fuel jettison subsystem is coupled between an interior portion and an exterior of the reservoir to selectably expel fuel from the reservoir to an exterior portion of the aircraft. The fuel jettison subsystem includes a jettison valve opening formed in the reservoir. A lid selectably closes off the opening. A biasing member urges the lid away from the jettison valve opening. A solenoid retains the lid in the jettison valve opening when unactuated and releases the lid when actuated. A jettison linkage is coupled to the solenoid, the jettison linkage being operable to actuate the solenoid. The lid is urged away from the jettison valve opening by the biasing member when the solenoid is actuated by the jettison linkage.

Description:
[0001]    This application is a continuation of U.S. patent application Ser. No. 12/702,385, filed Feb. 9, 2010, which claims priority to Canadian patent application no. 2,692,192, filed Feb. 4, 2010. The entire contents of each of these applications is expressly incorporated herein by reference thereto. 
     
    
     FIELD 
       [0002]    The present invention relates generally to a system for transporting flammable liquids, in particular to an aircraft incorporating the system and being usable to transport flammable liquids to remote sites. 
       BACKGROUND 
       [0003]    Consumers of flammable liquids, such as gasoline, kerosene, jet fuel, aviation gas and heating oil are often located at remote sites that are inconvenient or inaccessible by common ground-based transport. For example, industrial mining sites and forward operating bases in military applications are often not served by improved roads. Similarly, remote villages in many wilderness or arctic areas are not accessible by land or water routes during certain seasons. Finally, remote wilderness camps and lodges are often situated far from any land or water routes and within protected wilderness areas that do not allow ground access. 
         [0004]    One way to transport bulk flammable liquids to inaccessible, remote sites is to utilize small and medium-sized aircraft. Such aircraft can be equipped with tundra tires and rugged landing gear for landing and takeoff from unimproved landing strips and beaches. Likewise, the aircraft can be equipped with floats for operation upon lakes and rivers, or skis for operation upon ice and snow covered surfaces. However, special consideration must be given to the air transportation of bulk flammable liquids. Traditional methods of shipping fuel within aircraft cargo bays subjects the container(s) to possible damage during loading and unloading as well as in flight, with an attendant risk of explosion or fire. Another drawback of many fuel containers is that they are not conveniently sized or shaped to efficiently fit the geometries of aircraft cargo bays. Furthermore, loading and unloading containers of flammable liquids is laborious and potentially hazardous. Improper stowing of the fuel containers in an aircraft cargo bay can also result in a weight-and-balance configuration that is outside the safe operating envelope of the aircraft. Fuel containers that are flown inside conventional aircraft are vented into the cargo bays or not vented at all. Aircraft cargo bays are not an intrinsically safe environment and therefore pose a hazard when fuel containers vent or accidentally leak while transported within. Non-vented fuel containers are subjected to expanding and contracting forces as an aircraft descends and ascends, respectively. Lastly, containers of flammable liquids can become hazardous if they are improperly secured in the aircraft and are dislodged during aircraft operation. There is a need for a way to safely transport bulk flammable liquids in aircraft. 
       SUMMARY 
       [0005]    A system for airborne transportation of flammable liquids is disclosed according to an embodiment of the present invention. Storage containers are joined to the aircraft at locations that are appropriate to the aircraft&#39;s center of gravity, so as to maintain an appropriate weight and balance for the aircraft throughout its range of operating limitations with or without flammable liquids in the containers. Filler openings in the storage containers are each selectable and closable by a cap; the openings allow for rapid and efficient filling of the storage containers with flammable liquids. The storage containers are intrinsically safe. The cockpit of the aircraft is protected from flammable liquids by a vented double walled cavity as well as a vapour barrier. A vent system is installed on each storage container and vented to a safe location on the exterior of the aircraft. The vent system accommodates both negative and positive pressure changes that occur during flight operations as well as emergency dump situations. A fuel jettison system allows for rapid removal of flammable liquids from the storage containers in the event of an emergency. The fuel jettison system may include a biased lid to ensure reliable operation of the jettison system under low-temperature and icing environmental conditions. 
         [0006]    An aspect of the present invention is a system for transport of flammable liquids using an aircraft. A fuel tank and a reservoir, each for storing flammable liquids, are joined to the aircraft. A fuel jettison subsystem is coupled between an interior portion and an exterior portion of the reservoir to selectably expel fuel from the reservoir to an exterior portion of the aircraft. The fuel jettison subsystem includes a jettison valve opening formed in the reservoir. A lid selectably closes off the opening. A biasing member urges the lid away from the jettison valve opening. A solenoid retains the lid in the jettison valve opening when unactuated and releases the lid when actuated. A jettison linkage is coupled to the solenoid, the jettison linkage being operable to selectably actuate the solenoid. The lid is urged away from the jettison valve opening by the biasing member when the t solenoid is actuated by the jettison linkage. 
         [0007]    Another aspect of the present invention is a system for transport of flammable liquids using an aircraft. The system comprises a fuel tank for storing flammable liquids, the fuel tank being joined to the aircraft. The fuel tank has a first selectably closable fill port and further includes a first selectably closable discharge port. A reservoir for storing flammable liquids independent of the fuel tank is also joined to the aircraft. The reservoir has a second selectably closable fill port and further includes a second selectably closable discharge port. 
         [0008]    A fuel jettison subsystem is coupled between an interior portion and an exterior portion of the reservoir to selectably expel fuel from the reservoir to an exterior portion of the aircraft in the event of an exigent circumstance wherein landing the aircraft with fuel in the fuel tank and the reservoir inordinately increases the risk of landing. The subsystem includes a first jettison valve opening formed in the reservoir. A first lid selectably closes off the first jettison valve opening. A first biasing member urges the first lid away from the first jettison valve opening. A first solenoid retains the first lid in the first jettison valve opening when unactuated and releases the first lid when actuated. A jettison linkage is coupled to the first solenoid, the jettison linkage being operable to selectably actuate the first solenoid. The first lid is urged away from the first jettison valve opening by the first biasing member when the first solenoid is actuated by the jettison linkage. 
         [0009]    The system also includes a first suction valve coupled between an interior portion and an exterior portion of the fuel tank to selectably admit air to the fuel tank, the first suction valve being closed below a predetermined negative pressure threshold in the fuel tank and being open when the pressure in the fuel tank exceeds the negative threshold. A second suction valve is coupled between the interior portion and the exterior portion of the reservoir to selectably admit air to the reservoir, the second suction valve being closed below a predetermined negative pressure threshold in the reservoir and being open when the pressure in the reservoir exceeds the negative threshold. 
         [0010]    The system further includes a first pressure relief valve coupled between the interior portion and the exterior portion of the fuel tank to selectably expel at least one of air and fuel vapours from the fuel tank, the first pressure relief valve being closed below a predetermined positive pressure threshold in the fuel tank and being open when the pressure in the fuel tank exceeds the positive threshold. A second pressure relief valve is coupled between the interior portion and the exterior portion of the reservoir to selectably expel at least one of air and fuel vapours from the reservoir, the second pressure relief valve being closed below a predetermined positive pressure threshold in the reservoir and being open when the pressure in the reservoir exceeds the positive threshold. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0011]    Further features of the inventive embodiments will become apparent to those skilled in the art to which the embodiments relate from reading the specification and claims with reference to the accompanying drawings, in which: 
           [0012]      FIG. 1  shows the general arrangement of a system for airborne transportation of flammable fluids according to an embodiment of the present invention; 
           [0013]      FIG. 2  is a top plan view of a hopper fuel tank of the system of  FIG. 1 ; 
           [0014]      FIG. 3  shows a venting subsystem of the system of  FIG. 1 ; 
           [0015]      FIG. 4  shows further details of the hopper fuel tank of  FIG. 2 ; 
           [0016]      FIG. 5  is a side elevational view of a reservoir of the system of  FIG. 1 ; 
           [0017]      FIG. 6  is a top plan view of the reservoir of  FIG. 5 ; 
           [0018]      FIG. 7  is a schematic diagram showing the venting subsystem of  FIG. 3 , a fuel cargo jettison subsystem and a fuel cargo offload subsystem according to an embodiment of the present invention; 
           [0019]      FIG. 8  is a bottom plan view of a fuel cargo jettison valve according to an embodiment of the present invention; 
           [0020]      FIG. 9A  is a side elevational view showing details of the jettison valve of  FIG. 8 ; 
           [0021]      FIG. 9B  is a first end elevational view showing additional details of the jettison valve of  FIG. 8 ; 
           [0022]      FIG. 9C  is a second end elevational view showing further details of the jettison valve of  FIG. 8 ; 
           [0023]      FIG. 10  is a schematic diagram showing further details of the fuel jettison subsystem of  FIG. 7 ; 
           [0024]      FIG. 11  is a side elevational view of a fuel offload subsystem of the system of  FIG. 1 ; and 
           [0025]      FIG. 12  shows a vapour barrier for the hopper fuel tank of  FIG. 2   
       
    
    
     DETAILED DESCRIPTION 
       [0026]    The general arrangement of a system  10  for transportation of flammable liquids is shown in  FIG. 1 , the system preferably (but not necessarily) being incorporated into a vehicle such as an aircraft  12 . System  10  includes a hopper fuel tank  14 , an auxiliary fuel tank  16 , a fuel cargo jettison subsystem  18 , a fuel cargo vent subsystem  20  and a fuel cargo offload subsystem  22 . 
         [0027]    As shown in  FIG. 1 , hopper fuel tank  14  is disposed in a fuselage  24  of aircraft  12 , forward of a pilot compartment  26  and aft of an engine compartment  28 . With reference now to  FIGS. 2 through 4 , hopper fuel tank  14  may include at least one selectably removable, sealable access panel  30  to accommodate cleaning and inspection of the hopper fuel tank. Hopper fuel tank  14  further includes a fill port  32  having a cap  34  that is selectably removable to fill the hopper fuel tank with flammable liquids. A float-type vent valve  36  is coupled to fuel cargo vent subsystem  20  to allow venting of gases from hopper fuel tank  14  to the exterior of aircraft  12  and to provide an overflow path to the exterior of aircraft  12  for flammable liquids in the tank  14 . The float-type vent valve  36  closes when aircraft  12  is not level, is accelerating, or is decelerating, to prevent fuel from escaping under these conditions. 
         [0028]    A pressure relief valve  38  in communication with hopper fuel tank  14  is normally closed off but opens to the exterior of aircraft  12  in the event that the pressure in the hopper fuel tank exceeds a predetermined pressure value, thereby preventing damage to the tank due to an overpressure condition. This can occur, for example, as a result of pressure changes in hopper fuel tank  14  due to changes in the operating altitude of aircraft  12  or the thermal coefficient of expansion of flammable liquids in the hopper fuel tank with vent  36  in a blocked or closed condition. 
         [0029]    With reference to  FIGS. 3 and 4  together, in one embodiment of the present invention hopper fuel tank  14  may include a sidewall  40  that is spaced apart from a bulkhead  42  of aircraft  12 . Together sidewall  40  and bulkhead  42  form a secondary bulkhead  43  with an air space between hopper fuel tank  14  and pilot compartment  26  ( FIG. 1 ), the secondary bulkhead having a float-type vent valve  44  and a hollow drain tube  46  extending from the secondary bulkhead to the exterior of aircraft  12 . Float-type vent valve  44  is otherwise similar to float-type vent valve  36 , detailed above. Any leakage in secondary bulkhead  43 , which is indicative of a leak in hopper fuel tank  14 , may detected by inspecting drain  46  at its exit point to the exterior of aircraft  12  for the presence of fuel prior to flight. In the event of an in-flight leakage of hopper fuel tank  14 , leaked fluids will be directed into the airstream of aircraft  12  by drain  46 . 
         [0030]    Hopper fuel tank  14  may be made from any materials that are compatible with flammable liquids and the expected environment for aircraft  12 . Example materials include, without limitation, metal such as aluminum and epoxy resins such as Derakane®, available from Ashland Composite Polymers of Columbus, Ohio. Electrically conductive portions of hopper fuel tank  14  may be grounded to the airframe of aircraft  12  in any desired manner, such as with electrically conductive brackets, fasteners, wiring, braids, straps and cables to deter the buildup of static electricity and to route lightning discharge currents in a manner calculated to deter damage to the hopper fuel tank or its contents. 
         [0031]    Referring now to  FIGS. 1 ,  3  and  5  together, auxiliary fuel tank  16  includes an aerodynamic fairing  48  covering a reservoir tank  50 , both the fairing and reservoir being removably attached to a lower portion of fuselage  24  of aircraft  12 . A top portion  52  of reservoir  50 , shown best in  FIG. 6 , is spaced apart from fuselage  24  and preferably includes one or more access panels  30 , a fill port  32 , a cap  34  and a pressure relief valve  38 . A vent  94  ( FIG. 3 ) is coupled to fuel cargo vent subsystem  20  and is detailed further below. 
         [0032]    Reservoir  50  may be made from any materials that are compatible with flammable liquids and the expected environment for aircraft  12 . Example materials include, without limitation, metals such as aluminum. Reservoir  50  may further include one or more internal baffles and/or webbing  56  ( FIGS. 5 ,  6 ) to prevent sloshing of flammable liquids stored therein. Reservoir  50  is preferably attached to fuselage  24  with fasteners that allow the reservoir to be readily removed in the event the reservoir requires servicing. Electrically conductive portions of hopper reservoir  50  may be grounded to the airframe of aircraft  12  in any desired manner, such as with electrically conductive brackets, fasteners, wiring, braids, straps and cables to deter the buildup of static electricity and to route lightning discharge currents in a manner to deter damage to the reservoir or its contents. 
         [0033]    Fairing  48  may be made from a single piece, or may comprise a plurality of fairings. Fairing  48  may be made from any materials that are suitable for the expected environment for aircraft  12 . Example materials include, without limitation, epoxy fiberglass and metals such as aluminum. Fairing  48  may be painted, if desired, and may further include an opening or a selectable closure such as a hinged lid to provide access to fill port  32  on top portion  52  of reservoir  50 . Fairing  48  is preferably attached to fuselage  24  with fasteners that allow the fairing to be readily removed in the event reservoir  50  requires servicing. 
         [0034]    A schematic diagram of fuel cargo jettison subsystem  18  is shown in  FIG. 7 . Hopper fuel tank  14  includes a first jettison valve  58  and reservoir  50  includes a second jettison valve  60 , the jettison valves being coupled to a control  62  operable from pilot compartment  26  ( FIG. 1 ), such as a lever or handle, actuable by a mechanical, electrical or pneumatic linkage  64 . Hopper fuel tank  14  and reservoir  50  each further include a suction valve  66 . In the event that flammable liquids stored in tank  14  and reservoir  50  must be jettisoned, an operator of aircraft  12  operates control  62 , causing jettison valves  58 ,  60  to open. Suction valves  66  open at a resulting low negative pressure in tank  14  and reservoir  50 , allowing a high volume of air to flow into the tank and the reservoir as the flammable liquid is rapidly discharged. 
         [0035]    Details of jettison valve  60  are shown in FIGS.  8  and  9 A-C. Jettison valve  60  selectably closes off an opening  68  in reservoir  50  with a lid  70  having an O-ring seal  72 . Lid  70  is coupled to a link  74  by a spacer  76 . Link  74 , in turn, is hingedly attached to a support  78  at a first end by a fastener  80 . A second, opposing end of link  74  includes a locking tab  82  with an aperture  84 . A biasing member  86  is attached to link  74  and extends away from the link to contact a housing  88  of jettison valve  60 , the biasing member being in a loaded condition when lid  70  closes off opening  68 . An output shaft  90  of a solenoid  92  engages aperture  84  when the solenoid is in an unactuated condition, the solenoid and the locking tab cooperating to resist biasing member  86  and keep lid  70  in a closed condition, closing off opening  68 . 
         [0036]    With reference to  FIGS. 8 through 10  together, when jettison valve  60  is to be opened an operator operates control  62 , which in turn actuates solenoid  92  via linkage  64 . Output shaft  90  moves away from aperture  84  of locking tab  82 , allowing biasing member  86  to urge link  74  to pivot about support  78 , positively moving lid  70  away from opening  68  and thus exposing the opening, allowing fuel in reservoir  50  to be rapidly discharged. Biasing member  86  aids to urge lid  70  away from opening  68 , ensuring the operation of the jettison valve under low-temperature and icing environmental conditions. It should be noted that control  62 , linkage  64  and solenoid  92  may be realized using mechanical, electrical or pneumatic components within the scope of the invention. 
         [0037]    Details of fuel cargo vent subsystem  20 , shown in  FIG. 3 , comprises a hopper fuel tank vent  94 , a secondary bulkhead vent  96  and a reservoir vent  98 . Hopper fuel tank vent  94  includes a vent fitting  100  in communication with hopper fuel tank  14 , a hollow vent line  102  extending away from the vent fitting and being coupled to the exterior of aircraft  12 . Vent  96  for secondary bulkhead  43  also includes one or more vent fittings  100  and vent lines  102 . In addition, a space  104  between a lower fuselage portion  106  of fuselage  24  and the top portion  52  of reservoir  50  includes reservoir vent  98 , one or more vent fittings  100  and vent lines  102 . Vent fittings  100  may be made of any suitable material including, without limitation, Teflon® material available from E. I. du Pont de Nemours and Company of Wilmington, Del. Vent lines  102  may be made from nylon, such as ¼ inch nylon tubing. Vent system  20  also includes at least one vent valve  36  ( FIG. 2 ) and a pressure relief valve  38  ( FIG. 2 ) coupled to each of hopper fuel tank  14  and reservoir  50 . Vent valve  36  and pressure relief valve  38  each open at a predetermined pressure. Vent system  20  may further include a suction relief valve such as suction valve  66  ( FIG. 7 ). Vent system  20  prevents the buildup of either positive and negative air pressure in fuel tank  14  and reservoir  50  due to fuel expansion and contraction due to changes in temperature, and due to changes in the altitude of aircraft  12 . 
         [0038]    Referring now to  FIGS. 1 ,  7  and  11 , fuel cargo offload subsystem  22  includes a hopper fuel tank offload valve  108  in communication with hopper fuel tank  14 . Fuel cargo offload subsystem  22  further includes a reservoir offload valve  110  in communication with reservoir  50 . Each of valves  108 ,  110  includes a hose coupler  112 . Coupler  112  facilitates the selectable attachment of a fuel hose (not shown) for removal of fuel from hopper fuel tank  14  and reservoir  50 . An offload valve control linkage  114 , which extends to pilot compartment  26  ( FIG. 1 ) selectably controls the opening of valves  108 ,  110 . 
         [0039]    With reference to  FIGS. 1 ,  3 ,  4  and  12 , in some embodiments hopper fuel tank  14  may include one or more vapour barriers  116  between a lower portion  118  of the fuel tank and lower fuselage portion  106 . Vapour barriers  116  surround a space between lower fuel tank portion  118  and lower fuselage portion  106  to prevent fumes from entering fuselage  24 . Vapour barriers may be made from cloth conforming to specification MIL-PRF-20696F. Other materials may include, without limitation, rubber, EPDM, nitrile, buna, neoprene, flexible graphite, silicone, metal, mica, felt, plastic polymer such as Teflon® (PTFE), urethane, and ethylene propylene (EP). Vapour barriers  116  may be made from sheet material or may be applied as a liquid gasket, as appropriate to the material selected. 
         [0040]    Referring now to  FIGS. 1 through 12  together, in operation, flammable liquids such as fuel may be loaded into either or both hopper fuel tank  14  or reservoir  50  by removing the appropriate filler cap  34  ( FIG. 2 ). A fuel hose is inserted into a select fill port  32 . Venting during the load operation is accomplished though fill port  32 . After aircraft  12  has reached its offload point appropriate fuel offload hoses (not shown) are coupled to hose couplers  112  ( FIG. 11 ). Offload valve control linkage  114  is actuated, opening valves  108 ,  110  to drain tank  14  and reservoir  50 . If an external pump (not shown) is used for offloading fuel, it is preferable that caps  34  be removed first, to allow for adequate venting of tank  14  and reservoir  50  during the offloading operation. If caps  34  are not removed before pumping fuel from tank  14  and reservoir  50  suction valves  66  ( FIG. 7 ) may open due to the resulting negative pressure in the tank and/or reservoir. Similarly, pressure relief valves  38  will open in the event that a fill pump is inadvertently connected to hose couplers  112  with fill caps  34  installed. 
         [0041]    System  10  may carry a variety of flammable liquids within the scope of the invention including, without limitation, aviation fuel, jet fuel, automobile fuel, kerosene and diesel fuel. 
         [0042]    System  10  further includes a landing gear  120 , shown in  FIGS. 1 and 5 . Landing gear  120  is sized and shaped, and made of a select material to allow aircraft  12  to bear the weight of flammable liquids stored in hopper fuel tank  14  and reservoir  50  during all flight phases, including takeoff and landing. This is in contrast to typical aircraft operations where the aircraft takes off with a full load of fuel but consumes a significant portion of the fuel prior to landing. In one embodiment of the present invention landing gear  120  is made of spring steel. 
         [0043]    Aircraft  12  may further include large tundra-type tires  122 , shown in  FIGS. 1 and 5 . Tundra tires  122  allow aircraft  12  to operate from unimproved surfaces such as dirt, grass and gravel. 
         [0044]    While this invention has been shown and described with respect to a detailed embodiment thereof, it will be understood by those skilled in the art that changes in form and detail thereof may be made without departing from the scope of the claims of the invention.