Abstract:
An access door is provided in a housing for a gas turbine engine, with the access door being movable to an access position independent of any required movement of any cowl door or a fan duct door.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    This application relates to an access door provided in an inner housing of a gas turbine engine to provide access to internal components, without the need to open the cowl or fan duct doors. 
         [0002]    Gas turbine engines are known, and often include a fan delivering air to a compressor. Air is compressed in the compressor and delivered downstream to be mixed with fuel and combusted in a combustion section. Products of this combustion pass over turbine rotors, and drive the turbine rotors to rotate. A portion of the air delivered by the fan passes into a bypass duct about an engine core and is not delivered to the compressor. This air provides the majority of thrust for such a gas turbine engine. 
         [0003]    A nacelle surrounds the fan, and defines the bypass duct with an inner housing. The inner housing surrounds the engine core. Typically fan cowl doors, and fan duct/thrust reverser doors (hereafter “fan duct doors”) are provided in the nacelle. These doors may be pivoted to an open position to provide access to the inner components in the inner housing. Typically, when these doors pivot, they carry a portion of the internal housing to provide access to the internal components. Thus, to provide access to internal components, the fan cowl doors, or the fan duct doors must be pivoted to an open position. This is somewhat cumbersome and time consuming, particularly when required for routine maintenance to an internal component such as the gear box or an electrical generator. 
         [0004]    Locally positioned small access doors are incorporated into gas turbine engines to facilitate simple maintenance such as filling oil tanks or reading visual indications of an electrical generator oil level. However, these access doors have not been sufficiently large to allow maintenance such as removal or replacement of an auxiliary gear box or an electrical generator. 
       SUMMARY OF THE INVENTION 
       [0005]    In a disclosed embodiment of this invention, an access door is provided in an inner housing and is movable separately from the fan duct and fan cowl doors. This separately movable door provides access to components within the internal housing. In a disclosed embodiment, the components may include a gear box, and/or an electrical generator. In one disclosed embodiment, the separately movable access door does move with the fan duct doors, however, it is also movable to an open position while the fan duct doors remain in a closed position. 
         [0006]    These and other features of the present invention can be best understood from the following specification and drawings, the following of which is a brief description. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0007]      FIG. 1  is a schematic view of a gas turbine engine. 
           [0008]      FIG. 2  shows prior art fan duct door structure. 
           [0009]      FIG. 3  is a cross-sectional view through an inventive fan duct door. 
           [0010]      FIG. 4  shows an alternative embodiment. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0011]    A gas turbine engine  20  is illustrated in  FIG. 1 . As known, a fan  24  rotates about a central axis  22 . An internal core  26  includes a compressor, a combustor section, and a turbine section, as known. A portion of air from the fan  24  is delivered into core  26 . An outlet nozzle  28  discharges the core engine gas flow. The majority of the fan air is delivered into a bypass duct  25 . Bypass duct  25  is defined between a nacelle  30  and an outer periphery of an inner housing  32 . Included in the nacelle  30  are fan cowl doors  31 , and fan duct doors  33 . 
         [0012]    As shown, there are internal components  34 , which may include an auxiliary gear box, an electrical generator, etc. These components are mounted within the housing  32 . 
         [0013]    As shown in  FIG. 2 , in the prior art, the fan duct doors  33  include inner housing portions  38  and  40 , a hinge beam  35 , a pylon  36 , and a latch beam  42 . Housing portions  38  and  40  are part of inner housing  32 . The fan duct doors are typically provided with a pair of such structures, mounted on opposed circumferential sides of the center line  22 . The doors  33  are hinged on the hinge beam  35 , and latched at the latch beam  42 . In the prior art, to gain access to the interior of the inner housing  32 , the latch beam  42  had to be manipulated to release the latches, and the entire fan duct doors then needed to be pivoted to an open position. This is somewhat labor intensive. 
         [0014]    The present invention is directed to simplifying the amount of work necessary to gain access to the internal components  34 . Thus, as shown in  FIG. 3 , in an embodiment  130 , access doors  142  are pivotally attached at  144  to housing portion  140 . That is, the prior art housing portion  40  may be changed to include portion  140  and access door  142 . Some latching element  147  may latch two tangs  146  on the housing portions  142 . As shown schematically, the entire fan duct door pivots about axis  200 . Without needing to pivot the entire fan duct, the access door  142  may be pivoted to an open position (as shown in phantom) to provide access to the internal components  34 . The present invention is particularly feasible in gas turbine engines having shorter nacelles, such that the location of the components  34  tends to be closer to the axial location of the end of the nacelle. 
         [0015]      FIG. 4  shows another embodiment  150 , wherein the access door  154  pivots about a hinge axis  152  extending generally perpendicular to the axis of the hinges  144  of the  FIG. 3  embodiment. That is, axis  152  is perpendicular to an axis that is parallel to the central axis  22 . 
         [0016]    In the prior art it is known to provide access doors for various functions such as access to lubrication system, etc. However, these access doors have not been provided to facilitate the maintenance and removal of internal components such as the auxiliary gear box or generator. 
         [0017]    While the access doors in  FIGS. 3 and 4  are shown as being pivotably attached, they could be simply removable, and secured in some appropriate manner. 
         [0018]    When it is desired to merely access the auxiliary components such as the auxiliary gear box or electrical generator, the access door may be opened, and the fan duct doors may remain closed. At this position, there is access to the components for maintenance or removal. The fan duct doors need not be opened, and thus gaining access is simplified when compared to the prior art. 
         [0019]    While the access door is shown as part of the fan duct doors, it may be part of the cowl doors, or even separate from both doors. 
         [0020]    Although embodiments of this invention have 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.