Abstract:
An auxiliary power unit mounting system according to an exemplary aspect of the present disclosure includes, among other things, a plurality of linkages to support an auxiliary power unit, and a redundant mount to selectively support said auxiliary power unit.

Description:
CROSS REFERENCE TO RELATED APPLICATION 
       [0001]    This application is the U.S. national phase of PCT/US13/67022, filed Oct. 28, 2013, which claims priority to U.S. Provisional Application No. 61/721,605, filed Nov. 2, 2012. 
     
    
     BACKGROUND 
       [0002]    This disclosure relates generally to a redundant mount system for an auxiliary power unit. Auxiliary power units (APUs) are typically mounted within a tail cone or elsewhere in an aircraft. An APU can provide electric, pneumatic, or hydraulic power prior to start-up of the main gas turbine engines for the aircraft. 
       SUMMARY 
       [0003]    An auxiliary power unit mounting system according to an exemplary aspect of the present disclosure includes, among other things, a plurality of linkages to support an auxiliary power unit, and a redundant mount to selectively support the auxiliary power unit. 
         [0004]    In a further non-limiting embodiment of the foregoing auxiliary power unit mounting system, the plurality of linkages includes a three-link mount, a two-link mount, and a single-link mount. 
         [0005]    In a further non-limiting embodiment of either of the foregoing auxiliary power unit mounting systems, the three link mount is configured to restrict the auxiliary power unit in three degrees of movement, the two link mount is configured to restrict the auxiliary power unit in two degrees of movement, and the single link mount is configured to restrict the auxiliary power unit in one degree of movement. 
         [0006]    In a further non-limiting embodiment of any of the foregoing auxiliary power unit mounting systems, the redundant mount is a first redundant mount, and the system further includes a second redundant mount to selectively support the auxiliary power unit. 
         [0007]    In a further non-limiting embodiment of any of the foregoing auxiliary power unit mounting systems, the first redundant mount is fixed to the auxiliary power unit at a first position, and the second redundant mount is fixed to the auxiliary power unit at a second position, wherein the first position is circumferentially spaced from the second position about a central axis of the auxiliary power unit. 
         [0008]    In a further non-limiting embodiment of any of the foregoing auxiliary power unit mounting systems, the redundant mount is configured to support the auxiliary power unit during an abnormal operation. 
         [0009]    In a further non-limiting embodiment of any of the foregoing auxiliary power unit mounting systems, a plurality of electrical wires communicate power to the auxiliary power unit and the electrical wires are distinct from the redundant mount. 
         [0010]    In a further non-limiting embodiment of any of the foregoing auxiliary power unit mounting systems, the redundant mount is configured to be fixed to an aircraft structure. 
         [0011]    In a further non-limiting embodiment of any of the foregoing auxiliary power unit mounting systems, the redundant mount is configured to be fixed to the auxiliary power unit and to an aircraft structure. 
         [0012]    In a further non-limiting embodiment of any of the foregoing auxiliary power unit mounting systems, the first and second redundant mounts are fixed to an aircraft structure. 
         [0013]    A method of mounting an auxiliary power unit according to another exemplary aspect of the present disclosure includes, among other things, securing a plurality of linkages to an auxiliary power unit, securing the plurality of linkages to an aircraft structure, securing a redundant mount to the auxiliary power unit, and securing the redundant mount to the aircraft. 
         [0014]    In a further non-limiting embodiment of the foregoing method, the method includes restricting the auxiliary power unit in three degrees of movement using a three link mount, restricting the auxiliary power unit in two degrees of movement using a two link mount, and restricting the auxiliary power unit in one degree of movement using a one link mount. 
         [0015]    In a further non-limiting embodiment of either of the foregoing methods, the redundant mount is a first redundant mount, and the method further includes securing a second redundant mount to the auxiliary power unit and securing the second redundant mount to the aircraft. 
         [0016]    In a further non-limiting embodiment of any of the foregoing methods, the first redundant mount is secured to the auxiliary power unit at a first position, the second redundant mount is secured to the auxiliary power unit at a second position, the first position circumferentially spaced from a second position about a central axis of the auxiliary power unit. 
         [0017]    In a further non-limiting embodiment of any of the foregoing methods, the first position is circumferentially spaced at least 90 degrees from the second position. 
         [0018]    In a further non-limiting embodiment of any of the foregoing methods, the first redundant mount is secured to the auxiliary power unit at a first side, the second redundant mount is secured to the auxiliary power unit at a second side, and the first side is substantially opposite the second side. 
         [0019]    In a further non-limiting embodiment of any of the foregoing methods, the first redundant and the second redundant are configured to support the auxiliary power unit during an abnormal operation. 
         [0020]    In a further non-limiting embodiment of any of the foregoing methods, the method further includes securing a third redundant mount to the auxiliary power unit and securing the third redundant mount to the aircraft. 
         [0021]    In a further non-limiting embodiment of any of the foregoing methods, the first and second redundant mounts are cables. 
         [0022]    A redundant cable mount for an auxiliary power unit according to another exemplary aspect of the present disclosure includes, among other things, a cable having a first end and a second end, an attachment feature at the first end to attach the cable to an auxiliary power unit, and a second attachment feature at the second end to attach the cable to a frame of an aircraft. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0023]    These and other features of the disclosed examples can be best understood from the following specification and drawings, the following of which is a brief description. 
           [0024]      FIG. 1A  shows a highly schematic view of an example auxiliary power unit. 
           [0025]      FIG. 1B  shows a highly schematic view of the example auxiliary power unit of  FIG. 1  during an abnormal operation. 
           [0026]      FIG. 1C  shows a highly schematic view of an alternative example auxiliary power unit. 
           [0027]      FIG. 2  shows a perspective front view of the example auxiliary power unit of  FIG. 1 . 
           [0028]      FIG. 3  shows a perspective rear view of the example auxiliary power unit of  FIG. 1 . 
           [0029]      FIG. 4  shows a perspective side view of the example auxiliary power unit of  FIG. 1 . 
       
    
    
     DETAILED DESCRIPTION 
       [0030]    Referring to  FIG. 1A , an example APU  60  includes a turbine section  61  that drives a generator  63  to generate electricity. The APU  60  provides power prior to, for example, start-up the main gas turbine engines of an aircraft. The APU  60  may also provide electric and pneumatic power to the aircraft while the aircraft is stationary. Generally, the APU  60  provides power to the aircraft systems to either supplement or substitute power generated by the main gas turbine engines. 
         [0031]    The example APU  60  is mounted to the structure  67  of the aircraft through a mount system  65 . The mount system  65  includes a primary mount system  100  and a redundant mount system  101 . The structure  67  may be any aircraft structure, but the example APU  60  is mounted within the tailcone. The structure  67  is thus a structure near the tailcone. Alternatively, as illustrated schematically in  FIG. 1B , the primary mount system  100  could be mounted to a structure  67  and the redundant mount system  101  could be mounted to a second structure  67   b . During normal operation, the primary mount system  100  provides support to the APU  60 , as shown schematically in  FIG. 1A . The redundant mount system  101  is configured to support the APU during an abnormal operation. Abnormal operation is shown schematically in  FIG. 1C . 
         [0032]    Referring now to  FIGS. 2 and 3 , the example primary mount system  100  of the mount system  65  includes a one-point mount  62  having one linkage (see  FIG. 2 ), a mount  64  having two linkages, and a mount  66  having three linkages. In this example, during normal operation, the linkages  62 ,  64 ,  66  support the APU  60 . 
         [0033]    An example of abnormal operation is when one or more of the linkages  62 ,  64 ,  66  of the primary mount system  100  does not provide support to the APU  60 . Examples of abnormal operation include one or more of the linkages  62 ,  64 ,  66  failing. 
         [0034]    The example redundant mount system  101  includes a redundant cable mount  68  that can secure directly to the aircraft structure  67  or through a bracket  70  mounted to the structure  67 . In an embodiment, the cable  68  can attach directly to the APU  60  or to an inner bracket  71  secured to a mount flange  74  on a rear of the APU  60 . 
         [0035]    In this example, the redundant mount system  101  includes a second redundant cable mount  69 . The cable  69  can secure directly to the aircraft structure  67  or through a bracket  72  mounted to the structure  67 . The cable  69  can attach directly to the APU  60  or to an inner bracket  73  secured to mount flange  74  on a rear of the APU  60 . 
         [0036]    Because the redundant cables  68 ,  69  are configured to support the APU  60  during an abnormal operation, in an embodiment, redundant cables  68 ,  69  may be given slack so that they provide minimal or no support during normal operation. Providing slack would allow for ease of cable installation and, in some embodiments, would substantially eliminate interference with the primary mount system  100  during normal operation. 
         [0037]    Referring to  FIG. 3 , the first cable  68  is attached to the APU  60  at a position A. The second cable  69  is attached to the APU  60  at a position B, spaced circumferentially from position A about a central axis of the APU  60 . This spacing allows the redundant cables  68 ,  69  to restrain the APU  60  in all degrees of movement. Position A is spaced at least 90 degrees and at a substantially opposite side of the APU from position B. As one example, position A is spaced approximately 180 degrees from position B. 
         [0038]    The APU  60  may utilize a plurality of electrical wires  76  to communicate power to the APU  60 . The electrical wires  76  are distinct from the redundant cable mounts  68 ,  69 , however in various embodiments the electrical wires  76  may be mounted to the cables, or incorporated into or around the cables. 
         [0039]    In an embodiment of primary mount system  100 , the APU  60  is mounted to the structure  67  of the vehicle through linkages  62 ,  64 ,  66 . The three-point mount  66  secures the engine relative to the structure  67  in all 3 degrees of movement. The two-point mount  64  secures two degrees of rotation. The one-point mount  62  secures the third degree of rotation. Thus, the primary mount system  100  reacts 6 degrees of freedom—3 degrees of movement and 3 degrees of rotation. Such a system is statically determinate, not redundant. 
         [0040]    A worker of ordinary skill in this art would realize that this disclosure is not limited to an embodiment having two redundant cables. One cable or more than two cables could be utilized. For example, it may also be useful to include an additional cable at the forward end of the APU to control rotation during abnormal operation. 
         [0041]    Although a preferred 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.