Abstract:
A method of actuating a hydraulic latch and a fan duct includes providing a pressurized fluid for actuating a latch, providing a valve to control flow of pressurized fluid to the latch and the fan duct, and selectively opening the valve, whereby the pressurized fluid opens the fan duct. A gas turbine engine includes a fan duct with an inner structure surrounding an engine core, a fan case surrounding a fan, and at least one latch. The at least one latch secures a first portion of the fan duct inner structure to a core engine fame or to a second portion of the fan duct inner structure. The at least one latch is also configured to secure the second portion of the fan duct inner structure to the core engine fame or to the first portion of the fan duct inner structure.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    This application claims priority to U.S. Provisional Application No. 61/778,494, filed Mar. 13, 2014. 
     
    
     BACKGROUND 
       [0002]    This disclosure relates to a method of operating a hydraulically operated latching mechanism for a gas turbine engine nacelle. 
         [0003]    Gas turbine engines typically include a nacelle surrounding the engine core. Portions of the nacelle can be latched to one another and to the engine itself. Gas turbine engines also typically include a fan case surrounding a fan. The nacelle can also be latched around the fan case and to the engine core. These latches keep the nacelle and engine from separating due to various load cases including the high pressures generated by the engine. The latches may need to be released for on -ground maintenance. 
         [0004]    Currently, remotely operated latching mechanisms on a gas turbine engine are manually operated and are on occasion actuated by cables, rods, or other physical devices. Due to the remote location of latches relative to a handle in the gas turbine engine, it is difficult to actuate the latches and to confirm their successful closure. 
       SUMMARY 
       [0005]    In a featured embodiment, a method of hydraulically operating a latch and a fan duct comprises the steps of providing a pressurized fluid for actuating the latch, providing a valve to control flow of pressurized fluid to the latch and the fan duct, and selectively opening the valve, whereby the pressurized fluid opens the fan duct. 
         [0006]    In another embodiment according the previous embodiment, once the fan duct is opened, the method of hydraulically operating the latch and the fan duct further comprises the step of reducing at least one of a pressure or amount of the pressurized fluid, whereby the fan duct remains opened. 
         [0007]    In another embodiment according to any of the previous embodiments, the method of hydraulically operating the latch and the fan duct further comprises the steps of substantially stopping the flow of pressurized fluid, whereby the fan duct closes and selectively closing the valve, whereby the latch engages. 
         [0008]    In another embodiment according to any of the previous embodiments, the method of hydraulically operating the latch and the fan duct further includes the step of sensing the position of the latch. 
         [0009]    In another embodiment according to any of the previous embodiments, the valve is configured for manual actuation. 
         [0010]    In another featured embodiment, a gas turbine engine includes a fan duct with an inner structure surrounding an engine core, a fan case surrounding a fan, and at least one latch, actuated by pressurized fluid, is configured to secure a first portion of the fan duct inner structure to one of a core engine fame and a second portion of the fan duct inner structure, or is configured to secure the second portion of the fan duct inner structure to one of the core engine frame and the first portion of the fan duct inner structure, whereby actuating the at least one latch provides for releasing the first and second portions of the fan duct inner structure from said first and second portions of the core engine frame or from one another. 
         [0011]    In another embodiment according to any of the previous embodiments, the fan duct includes a door opening system, and the door opening system is actuated by the pressurized fluid, and the pressurized fluid is controlled by at least one valve. 
         [0012]    In another embodiment according to any of the previous embodiments, the latch is mounted on the fan duct. 
         [0013]    In another embodiment according to any of the previous embodiments, the latch is mounted on the core engine frame. 
         [0014]    In another embodiment according to any of the previous embodiments, the gas turbine engine further includes a valve to control the flow of pressurized fluid to the latch. 
         [0015]    In another embodiment according to any of the previous embodiments, the fan duct includes a mechanism to hold the fan duct in an open position. 
         [0016]    In another embodiment according to any of the previous embodiments, the hold-open mechanism is a rod. 
         [0017]    In another embodiment according to any of the previous embodiments, the gas turbine engine further includes a position sensor to sense the position of at least one latch. 
         [0018]    In another embodiment according to any of the previous embodiments, the pressurized fluid is supplied by a pump via at least one conduit. 
         [0019]    In another embodiment according to any of the previous embodiments, the conduit includes a quick disconnect fitting. 
         [0020]    In another embodiment according to any of the previous embodiments, the latch is configured to secure one of the first and second portions of the fan duct inner structure to the core engine frame. 
         [0021]    In another embodiment according to any of the previous embodiments, the latch is configured to secure the first portion of the fan duct inner structure to the second portion of the fan duct inner structure. 
         [0022]    These and other features can be best understood from the following specification and drawings, the following of which is a brief description. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0023]      FIG. 1  illustrates a schematic gas turbine engine propulsion system. 
           [0024]      FIG. 2   a  illustrates a simplified schematic gas turbine propulsion system. 
           [0025]      FIG. 2   b  illustrates a cross section of the schematic gas turbine engine propulsion system including latching systems securing first and second portions of the fan duct to one another. 
           [0026]      FIG. 3  illustrates an example schematic pin latch securing a fan duct inner structure to a core engine frame. 
           [0027]      FIG. 4   a  illustrates a top-down detail view of the latching systems of  FIG. 2   b.    
           [0028]      FIG. 4   b  illustrates a side detail view of the latching systems of  FIG. 2   b  in the open position. 
           [0029]      FIG. 4   c  illustrates a side detail view of the latching systems of  FIG. 2   b  in the closed position. 
           [0030]      FIG. 5  illustrates a schematic hydraulic system for a fan duct door opening system (DOS) in the closed position coupled to a pin latch. 
           [0031]      FIG. 6   a  illustrates the schematic hydraulic system of  FIG. 5  with the DOS in the hold open position and a hold open mechanism. 
           [0032]      FIG. 6   b  illustrates the hold open mechanism of  FIG. 6   a.    
           [0033]      FIG. 7  illustrates the schematic hydraulic system of  FIG. 5  with the DOS closing and the pin latch disengaged. 
           [0034]      FIG. 8  illustrates the schematic hydraulic system of  FIG. 5  with the DOS closed and the pin latch engaged. 
       
    
    
     DETAILED DESCRIPTION 
       [0035]      FIG. 1  schematically illustrates a gas turbine engine propulsion system  20 . The gas turbine engine propulsion system  20  is disclosed herein as a two-spool turbofan that generally incorporates a fan section  22 , a compressor section  24 , a combustor section  26  and a turbine section  28 . The fan section  22 , the compressor section  24 , and the combustor section  26  are collectively known as a core engine  12 . Alternative engines might include an augmenter section (not shown) among other systems or features. The fan section  22  drives air along a bypass flowpath B in a bypass duct defined within a nacelle  15 , while the compressor section  24  drives air along a core flowpath C for compression and communication into the combustor section  26  then expansion through the turbine section  28 . Although depicted as a turbofan gas turbine engine in the disclosed non-limiting embodiment, it should be understood that the concepts described herein are not limited to use with turbofans as the teachings may be applied to other types of turbine engines including three-spool architectures. 
         [0036]    The engine  20  generally includes a low speed spool  30  and a high speed spool  32  mounted for rotation about an engine central longitudinal axis A relative to an engine static structure  36  via several bearing systems  38 . It should be understood that various bearing systems  38  at various locations may alternatively or additionally be provided. 
         [0037]    The low speed spool  30  generally includes an inner shaft  40  that interconnects a fan  42 , a low pressure compressor  44  and a low pressure turbine  46 . A fan case  23  surrounds the fan  42 . The inner shaft  40  is connected to the fan  42  through a geared architecture  48  to drive the fan  42  at a lower speed than the low speed spool  30 . The high speed spool  32  includes an outer shaft  50  that interconnects a high pressure compressor  52  and high pressure turbine  54 . A combustor  56  is arranged between the high pressure compressor  52  and the high pressure turbine  54 . A mid-turbine frame  57  of the engine static structure  36  is arranged generally between the high pressure turbine  54  and the low pressure turbine  46 . The mid-turbine frame  57  further supports bearing systems  38  in the turbine section  28 . The inner shaft  40  and the outer shaft  50  are concentric and rotate via bearing systems  38  about the engine central longitudinal axis A which is collinear with their longitudinal axes. 
         [0038]    The core airflow C is compressed by the low pressure compressor  44  then the high pressure compressor  52 , mixed and burned with fuel in the combustor  56 , then expanded over the high pressure turbine  54  and low pressure turbine  46 . The mid-turbine frame  57  includes airfoils  59  which are in the core airflow path. The turbines  46 ,  54  rotationally drive the respective low speed spool  30  and high speed spool  32  in response to the expansion. 
         [0039]    Referring to  FIG. 2   a , a fan duct inner structure  112  surrounds the core engine  12  and encloses a core compartment  31 . Various components may be provided in the core compartment  31 , such as fluid conduits, for example, or a compressed air duct  33 . The compressed air duct  33  is under high pressure and may supply compressed air from a low or high pressure compressor stage to a high pressure turbine stage for cooling, for example, or for an airframe Environmental Control System (ECS). 
         [0040]    Referring to  FIG. 2   b , in some nacelle  15  configurations, upper and lower bifurcations  27   a,    27   b  may extend radially in the bypass flowpath  125  in locations opposite one another to accommodate wires, fluid conduits, engine mounting, or other components. 
         [0041]    Referring again to  FIG. 2   a , the bypass flowpath  125  is provided by inner and outer flow surfaces  49 ,  51 , which define portions of the nacelle  15  along an axial portion of the engine propulsion system  20 . A translating sleeve  29  is arranged outwardly of the fan duct flow path  125  in the nacelle  15 . The translating sleeve  29  is shown in a closed position in  FIG. 2   a . Bypass air B flows through the bypass flowpath  125  and produces a significant component of forward thrust. 
         [0042]    Referring to  FIG. 2   b  with continued reference to  FIG. 2   a , the nacelle  15  portion aft of the fan exit guide vanes  25  (shown in  FIG. 2   a ) includes the translating sleeve  29 , the fan duct inner structure  112 , and the upper and lower bifurcations  27   a,    27   b , collectively known as the fan duct  114 . The fan duct  114  opens on the hinge lines  115  to gain access to the core compartment  31  for maintenance or engine removal and replacement. Translating sleeve  29  may actuate portions of the nacelle  15  aft of the fan case  23  to move in the aft direction and act to reverse thrust. 
         [0043]    As is shown schematically in  FIG. 3 , one or more latching mechanisms may be used to secure portions of the core engine frame  113  and the fan duct inner structure  112  to one another. In the example shown in  FIG. 3 , the latching mechanism  154  includes a pin latch. In this example, the pin latch  154  is mounted on the core engine frame  113  and a pin latch receptacle  254  is on the fan duct inner structure  112 . In another example, the pin latch  154  may be mounted on the fan duct inner structure  112  and the receptacle  254  may be mounted on the core engine frame  113 . 
         [0044]    As is shown schematically in  FIGS. 4   a - 4   c,  one or more latching mechanisms may also be used to secure a first portion  112   a  of the fan duct inner structure  112  to a second portion  112   b  of the fan duct inner structure  112 . In the example shown in  FIGS. 4   a - c , the latch  155  is a hook latch mounted on the fan duct inner structure  112 . The hook latch  155  may include an additional pivot point  255 . A hook latch receptacle  256  may receive the hook latch  155 .  FIG. 4   a  shows a top-down schematic view of the hook latch  155 .  FIGS. 4   b  and  4   c  show side schematic views of the hook latch  155  in the open and closed positions, respectively. 
         [0045]    The latches  154 ,  155  can be actuated hydraulically. That is, pressurized fluid can be used to actuate the latches  154 ,  155  from an engaged to a disengaged position once a pressurized fluid source is connected to the latches  154 ,  155 . A pressurized fluid source such as an automated or manually operated pump can be connected to the latches  154 ,  155  during on-ground maintenance and the latches  154 ,  155  can be opened to allow access to the desired engine parts in the core compartment  31 . 
         [0046]    In one embodiment, release of the latches  154 ,  155  and opening of the fan duct  114  around hinge line  115  can be accomplished by a single hydraulic system with a source of pressurized fluid. Referring to  FIG. 5 , an example fan duct  114  has a door opening system (DOS)  152  coupled to a hydraulic system  157  and the latch  154  which, in this example, is a pin latch as compared with hook latch  155 . Note the latch can be another kind of latching mechanism. A pump  156  supplies pressurized fluid by conduit  158  to the pin latch  154  and the DOS  152 . The conduit  158  can include a fitting  160 , such as a quick-disconnect fitting, for manual control of the hydraulic system  157 . In another example, the DOS  152  may also include an accumulator. In another example the pump  156  may be motorized. In another example the pump  156  may be permanently attached to the rest of the hydraulic system  157 . 
         [0047]    In this example, the pump  156  provides pressurized fluid to disengage the pin latch  154 . Fluid flow from the pump  156  is controlled by a pump valve  159 . A one-way check valve  162  may be present between the pump  156  and the pin latch  154  to prevent inadvertent closure or re-engagement of the mechanism during opening and closing of the fan duct  114 . The one-way check valve  162  may be manually operated. 
         [0048]    A manually operated valve  164  is present between the pump  156  and the DOS  152 . The manually operated valve  164  is in a closed position when the DOS  152  is closed, as is shown in  FIG. 5 . As is shown in  FIGS. 6   a - 6   b,  when the manually operated valve  64  is opened, the pressurized fluid supplied by the pump  156  extends the DOS  152  and consequently opens the fan duct  114 . The DOS  152  and consequently the fan duct  114  can include a mechanism  166  to hold it open. In one example, the hold-open mechanism  166  may be a rod. When the hold-open mechanism  166  is in use, the pressurized fluid supplied by the pump  156  can be reduced to allow the fan duct  114  to rest on the hold-open mechanism  166 . In another example, a locking mechanism may also be included in the DOS  152 . 
         [0049]    To close the DOS  152  and consequently the fan duct  114 , the system is pressurized, which simultaneously opens the pin latch  154 , and extends the DOS  152 . This allows the hold-open mechanism  166  to be disengaged by relieving the effect of the weight of the fan duct  114 . As is shown in  FIG. 7 , the manually operated valve  164  is in the open position and the pump valve  159  is turned to a second position to allow inflow. The weight of the fan duct  114  closes the DOS  152  and forces the pressurized fluid out of the DOS  152 . The pin latch  154  remains open due to the trapped fluid in that portion of the circuit. 
         [0050]    As is shown in  FIG. 8 , once the DOS  152  is empty of fluid and the fan duct  114  is closed, the manually operated valve  164  can be turned to a second position. The spring force provided by a spring  118  in the latch mechanism will return the retained fluid from the pin latch  154  back to the reservoir in the pump  156  by the return line  116 . As the pin latch  154  returns to its nominal state the latching mechanism is re-engaged so that the fan duct  114  can resist a high pressure event in the core compartment  31 . In another example, the return line  116  may not be present. 
         [0051]    In another example, the DOS  152  and the latch  154 ,  155  may be controlled by separate hydraulic systems. 
         [0052]    The hydraulic system  157  can also include a position sensor  168  ( FIGS. 5-8 ). The position sensor  168  can detect the position of the latch  154 ,  155 . The position sensor  168  can confirm engagement or disengagement of the latch  154 ,  155 . Because the position sensor  168  and the latch  154 ,  155  may be positioned in the engine core compartment  31 , which may have high operating temperatures, in one example, the position sensor  168  and the latch  154 ,  155  are capable of withstanding a high temperature environment. 
         [0053]    Although an embodiment of this invention has been disclosed, a worker of ordinary skill in this art would recognize that certain modifications would come within the scope of this invention. For that reason, the following claims should be studied to determine the true scope and content of this invention.