Abstract:
An auxiliary power unit bracket, according to an exemplary aspect of the present disclosure includes, among other things, a gearbox mounting face and a compartment mounting face, the gearbox mounting face configured to attach to an auxiliary power unit gearbox below a sump level line, the compartment mounting face configured to attach to a portion of an auxiliary power unit compartment above the sump level line.

Description:
BACKGROUND 
       [0001]    This disclosure relates generally to securing an auxiliary power unit. 
         [0002]    Turbomachines extract energy from a flow of fluid. During operation, air is pulled into the turbomachine. The air is then compressed and combusted. The products of combustion expand to rotatably drive a turbine section of the turbomachine. 
         [0003]    One example turbomachine is an auxiliary power unit (APU). An APU may be located in the tail section or elsewhere on a commercial aircraft. The APU provides electrical power and compressed air to the aircraft. 
         [0004]    During operation, the APU is exposed to extreme temperatures and other harsh operating conditions. Tests have been developed to ensure that the APU and its associated components will respond appropriately when facing such conditions. Tests are continually revised and new tests are added. Passing these tests can be difficult, especially when using retrofitted APUs and retrofitted components. 
       SUMMARY 
       [0005]    An auxiliary power unit bracket, according to an exemplary aspect of the present disclosure includes, among other things, a gearbox mounting face and a compartment mounting face, the gearbox mounting face configured to attach to an auxiliary power unit gearbox below a sump level line, the compartment mounting face configured to attach to a portion of an auxiliary power unit compartment above the sump level line. 
         [0006]    In a further non-limiting embodiment of the foregoing auxiliary power unit bracket, the bracket has a “U” shape. 
         [0007]    In a further non-limiting embodiment of either of the foregoing auxiliary power unit brackets, the bracket comprises steel. 
         [0008]    In a further non-limiting embodiment of any of the foregoing auxiliary power unit brackets, the gearbox mounting face is a first gearbox mounting face and the bracket includes a second gearbox mounting face opposite the first gearbox mounting face. 
         [0009]    In a further non-limiting embodiment of any of the foregoing auxiliary power unit brackets, the compartment mounting face is a first compartment mounting face and the bracket includes a second compartment mounting face opposite the first compartment mounting face. 
         [0010]    In a further non-limiting embodiment of any of the foregoing auxiliary power unit brackets, the gearbox mounting face is configured to attach to an aluminum auxiliary power unit gearbox. 
         [0011]    In a further non-limiting embodiment of any of the foregoing auxiliary power unit brackets, a support strap is configured to interface with a downwardly facing portion of the auxiliary power unit gearbox. 
         [0012]    In a further non-limiting embodiment of any of the foregoing auxiliary power unit brackets, the compartment mounting face is configured to attach to a strut extending from a wall of the compartment to the compartment mounting face. 
         [0013]    An auxiliary power unit assembly according to an exemplary aspect of the present disclosure includes, among other things, a gearbox, the gearbox including a sump level line, the gearbox including at least one mounting pad below the associated sump level line; a bracket including at least one gearbox mounting face secured to a corresponding one of the at least one mounting pad; and an arm of the bracket extending upwardly past the associated sump level line. 
         [0014]    In a further non-limiting embodiment of the foregoing auxiliary power unit assembly, the arm extends past the associated sump level line to a compartment mounting face. 
         [0015]    In a further non-limiting embodiment of either of the foregoing auxiliary power unit assemblies, a support strap of the bracket extending along a downwardly facing surface of the gearbox. 
         [0016]    In a further non-limiting embodiment of any of the foregoing auxiliary power unit assemblies, the at least one mounting pad comprises first and a second mounting pads on opposing lateral sides of the gearbox. 
         [0017]    In a further non-limiting embodiment of any of the foregoing auxiliary power unit assemblies, the first and second mounting pads face in opposite directions. 
         [0018]    In a further non-limiting embodiment of any of the foregoing auxiliary power unit assemblies, the bracket is steel. 
         [0019]    In a further non-limiting embodiment of any of the foregoing auxiliary power unit assemblies, the at least one mounting pad comprises aluminum. 
         [0020]    A method of supporting an auxiliary power unit gearbox according to another exemplary aspect of the present disclosure includes, among other things, securing a bracket to a gearbox of an auxiliary power unit at a location that is below a sump level line of the auxiliary power unit gearbox; and securing the bracket to a compartment of an aircraft housing the auxiliary power unit at a location that is above the sump level line of the auxiliary power unit gearbox. 
         [0021]    In a further non-limiting embodiment of the foregoing method, the method includes supporting the auxiliary power unit gearbox utilizing a strap extending along a downwardly facing surface of the auxiliary power unit gearbox. 
         [0022]    In a further non-limiting embodiment of either of the foregoing methods, the method includes securing the bracket to opposing lateral sides of the gearbox. 
         [0023]    Although the different examples have the specific components shown in the illustrations, embodiments of this disclosure are not limited to those particular combinations. It is possible to use some of the components or features from one of the examples in combination with features or components from another one of the examples. 
     
    
     
       BRIEF DESCRIPTION OF THE FIGURES 
         [0024]      FIG. 1  shows a side view of an auxiliary power unit within a tail section of an aircraft, in an embodiment. 
           [0025]      FIG. 2  shows a perspective view of an example mounting bracket for use with the auxiliary power unit of  FIG. 1 , in an embodiment. 
           [0026]      FIG. 3  shows a front view of the mounting bracket of  FIG. 2  and a section view of a gearbox of the auxiliary power unit of  FIG. 1 , in an embodiment. 
           [0027]      FIG. 4  shows a side view of the mounting bracket of  FIG. 2  and a section view of the gearbox, in an embodiment. 
           [0028]      FIG. 5  shows a side view opposite the side view of  FIG. 4 , in an embodiment. 
           [0029]      FIG. 6  shows a more detailed view of the APU of  FIG. 1  within the tail section, in an embodiment. 
           [0030]      FIG. 7  shows a perspective view of  FIG. 6 , in an embodiment. 
       
    
    
     DETAILED DESCRIPTION 
       [0031]    Referring to  FIG. 1 , a tail section  10  of an aircraft houses an example auxiliary power unit (APU)  14  within an APU compartment  16 . As known, the APU  14  is used to provide power and pressurized air for use in the aircraft. 
         [0032]    During operation, air moves to a turbine section  18  of the APU  14  from a plenum  22 . The turbine section  18  rotatably drives a generator  30 . A gearbox  34  rotatably couples the generator  30  to the turbine section  18 . The APU  14  includes various other components to assist in its operation. 
         [0033]    Although shown in the tail section  10  of the aircraft, a person having skill in this art and the benefit of this disclosure will understand that the APU  14  could be located elsewhere within the aircraft. 
         [0034]    The example APU  14  includes forward mounts  38  and rear mounts  42 . Struts (not shown in  FIG. 1 ) are coupled to the mounts  38  and  42  to secure the APU  14  within the compartment  16 . To meet regulations, the mounts  38  and  42  must withstand relatively intense temperatures. In one example, the mounts  38  and  42  are required to suitably withstand a temperature of 2000° F. (1093° C.) for 15 or more minutes. The mounting strategy of the example APU  14  facilitates meeting this and other regulations. 
         [0035]    Referring now to  FIGS. 2-5  with continuing reference to  FIG. 1 , the gearbox  34  of the example APU  14  includes the forward mounts  38 . The gearbox  34  is supported in a mounted position by a bracket  46  secured to the forward mounts  38 . 
         [0036]    The bracket  46  includes a first arm  50  and a second arm  54  extending upwardly from opposing ends of a support strap  56 . Lower ends of the arms  50  and  54  each include a gearbox mounting face  60 . Upper ends of the arms  50  and  54  each include a compartment mounting face  64 . The bracket  46  generally has a “U” shape. 
         [0037]    The bracket  46  is steel in this example, which is a material considered capable of withstanding temperature-based tests. The gearbox  34 , by contrast, has an outer housing  66  that is aluminum, which is less capable of withstanding temperature-based tests than steel. 
         [0038]    When assembled, the support strap  56  extends across a downwardly facing surface  68  of the gearbox  34 , and the gearbox mounting faces  60  attach directly to mounting pads  70  on oppositely facing outer lateral sides of the gearbox  34 . The mounting pads  70  are aluminum. Exposure to extreme temperature can damage the mounting pads  70  and undesirably disrupt the connection between the mounting pads  70  and the gearbox mounting faces  60 . 
         [0039]    In this example, the mounting pads  70  are positioned vertically below a sump level line  74 , which represents a level of lubricant (such as oil) held within the gearbox  34 . During a thermal event exposing the bracket  46  and the gearbox  34  to extreme temperatures, the lubricant within the gearbox  34  evaporates and cools areas of the gearbox  34 , particularly those areas of the gearbox  34  at or below the sump level line  74 . Placing the mounting pads  70  below the sump level line thus facilitates maintaining the integrity of the mounting pads  70  during a high temperature event. 
         [0040]    The example bracket  46  is secured to the gearbox  34  via four mechanical fasteners  76 , such as screws, extending through the gearbox mounting faces  60  to the mounting pads  70  of the gearbox  34 . 
         [0041]    In this example, positioning the mounting pads  70  below the sump level line  74  ensures that these mechanical fasteners  76  do not loosen or disengage during a thermal event. The bracket  46  maintains its integrity due to its material composition. 
         [0042]    Notably, in the event that the connection between the mounting faces  60  and the mounting pads  70  should weaken or become disengaged, the support strap  56  limits downward movement of the gearbox  34  from the mounted position. 
         [0043]    When the gearbox  34  is in the mounted position within the compartment  16 , the arms  50  and  54  of the bracket  46  extend upwardly past the sump level line to the compartment mounting faces  64 . As shown in  FIGS. 6 and 7 , struts  78  extending from interior walls of the compartment  16  may be used or secured directly to the compartment mounting faces  64 . 
         [0044]    Some other APUs include gearboxes that do not require as much vertical packaging area as the gearbox  34 . In those APUs, the bracket  46  may be omitted and the struts  78  may attach directly to the gearbox at a position below a sump level line. The bracket  46  of this disclosure allows the APU  14 , which requires more vertical packaging area for the gearbox  34 , to be introduced into environment designed for the other APUs without requiring significant changes to the locations of the struts, etc. 
         [0045]    In this disclosure, elevations and vertical differences refer generally to an orientation where the APU  14  and surrounding structures, such as the aircraft, are on level ground or in straight or level flight. 
         [0046]    Features of the disclosed examples include a bracket that permits retrofitting a vertically taller APU into an existing environment without requiring significant packaging changes and while meeting temperature-based testing requirements. 
         [0047]    The preceding description is exemplary rather than limiting in nature. Variations and modifications to the disclosed examples may become apparent to those skilled in the art that do not necessarily depart from the essence of this disclosure. Thus, the scope of legal protection given to this disclosure can only be determined by studying the following claims.