Abstract:
A drip pan apparatus for a “M” model BLACK HAWK® helicopter and the like includes an expanded corner structure for accommodating an access port also positioned further outwardly in the corner than in prior drip pan apparatuses, facilitating filter viewing while retaining peripheral o-ring seal. An expanded corner of the airframe skirt is accommodated by the expanded corresponding corner of a frame, which also defines a small radius internal curve. The removable pan has a small radius curve cooperating with the small radius curve of the frame and is sealed thereto by the peripheral o-ring seal sealing the entire pan to the frame. Physical access to the filter is enhanced.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of U.S. Pat. No. 8,317,127, filed Jan. 10, 2012, which claims the benefit of and is a divisional application of U.S. Pat. No. 8,096,496, filed Dec. 8, 2008; and U.S. Provisional Patent Application Ser. No. 61/014,960, filed Dec. 19, 2007, the disclosures of each being incorporated by reference herein in their entirety. 
    
    
     FIELD OF THE INVENTION 
     This invention relates to a fluid-tight drip pan, and more specifically to a fluid-tight drip pan for the engine or transmission compartment of a helicopter. 
     BACKGROUND OF THE INVENTION 
     Larger helicopters, in general, have several features in common in a typical basic configuration or layout. For instance, a typical helicopter will have a cabin section rearward of the pilot&#39;s cockpit or flight deck and which is used to transport people, cargo or both. In addition, the helicopter will have an engine compartment which is located typically above and to the rear of the pilot&#39;s cockpit or flight deck, and above the cabin section. The engine compartment typically houses two primary components, at least one engine and a rotor transmission with a corresponding transmission housing. 
     Both the engine and the rotor transmission contain numerous fluids, such as petroleum-based lubricants, that are critical to the operation of the engine and the transmission. These fluids inevitably leak from various locations in the engine and the transmission during both the operation and storage of the helicopter. Because the engine compartment is generally oriented above the cabin section, any leaking fluids eventually seep or drip into the cabin section, unless proper sealing mechanisms are in place. The inflow of these leaking fluids spoil, stain or damage the cabin&#39;s interior materials such as seat covers and acoustic linings. In addition, the leaking fluids can severely damage or destroy sensitive electronic equipment that may be placed in the cabin section of a helicopter. 
     Moreover, the exterior of the helicopter around the engine and transmission compartment is not completely fluidtight, allowing fluid such as water to leak from these areas into the cabin with similar adverse effects. 
     During routine inspection and maintenance it is necessary to have both ready visual and physical access to portions of the engine or at least the rotor transmission. Such access is required to check critical fluid levels, to replace worn, damaged or depleted parts or filters, or to adjust mechanical systems. Typically, various access panels in or around the engine or transmission compartments provide the requisite openings to achieve ready access to the engine and the rotor transmission. In some helicopters, a forged or fixed airframe structure forms an access opening which is located below the rotor transmission housing and above the cabin section. The opening is thus accessible through the cabin&#39;s ceiling. This access opening, however, must be sealed by a cover against the inevitable oil and fluid drippings which the engine and the rotor transmission will produce, as well as against water leakage. 
     The access opening below the engine compartment in the prior helicopters, such as the BLACK HAWK® helicopter, made for the United States by Sikorsky Aircraft Company of Stratford, Conn., is defined by both the aircraft structural forgings and a flexible or yieldable downwardly-turned skirt which is riveted onto the helicopter&#39;s forged structure. The skirt is thin and many times more flexible relative to the helicopter&#39;s forged structure. 
     Prior drip pan designs attached a covering plate directly to the flexible skirt with a hollow seal sandwiched therebetween. One hollow seal used in prior designs resembled the flexible, hollow door seals used around car doors or refrigerator doors. However, the skirt contains surface aberrations, such as the protruding rivet heads from the rivets securing the skirt to the forged helicopter structure. When the seal engaged both the skirt and the rivet heads, it could be upset enough so that leakage occurred. Accordingly, the hollow seal traversing these aberrations while sandwiched between the skirt and the covering plate is unable to provide a suitable, consistent, long-term fluid seal. Moreover, flexing of the flexible skirt could also cause leakage. 
     Also, the geometry of the cover cannot be such that it protrudes significantly into the interior of the cabin section. Headroom in the cabin section typically is limited and any additional protrusion from the ceiling of the cabin section is undesirable. In addition, because weight is critical to the operation of any aircraft, heavy cover constructions are undesirable. 
     Other prior drip pan structures disclosed in U.S. Pat. Nos. 6,112,856; 6,216,823; 6,446,907 and Design Pat. No. D444,443, which are fully incorporated herein by this express reference, provided improvements and solutions to these difficulties. However, Sikorsky has now introduced its “M” Model BLACK HAWK® helicopter for which these prior structures are not readily adaptable due to a change in configuration of the skirt noted above. 
     In particular, while the prior drip pans provided a port for visual access to an oil filter, the port was offset from the filter, rendering it more difficult to see the filter from many viewing angles through the port, also requiring specially shaped tools to manipulate filter retention bolts and requiring tilting of filters when removed or replaced. 
     The “M” model is currently in the process of introduction by Sikorsky for use by U.S. Military. In that model, and in other aircraft with what are or will be similarly-shaped skirts, there is still a skirt as disclosed in the prior U.S. Pat. No. 6,446,907 with the exception that in the access area or corner for the filter, the corner of the skirt has been pulled outwardly to allow direct and straight-through access to the filter and its filter retention bolts where the pan is removed. Such direct access is preferable as it eliminates the need for the special dog-bone shaped tools necessary to operate the filter retention bolts to remove and install the filter as was required with the prior drip pan, which not only required such tools but also required the filter to be “tipped” as it was removed or replaced and before it could be seated (see FIG. 6 of U.S. Pat. No. 6,446,907). Accordingly, in the new “M” model, one corner of the old prior skirt has been pulled or extended outwardly and asymmetrically to the other corners. 
     Stated in another way, the radius point or center of the expanded corner curve of the skirt has been moved outwardly from its position in the prior drip pan and the straight sides of the skirt are no longer tangent to the curve of this corner. 
     Such modification of the skirt renders the prior symmetric frame and drip pan incompatible with the new “M” model air frame. There is or would be a gap between the new skirt at the expanded corner and the old drip pan and drip pan frame. Accordingly, there is no way for the old drip pan and frame structure of the prior patents, including U.S. Pat. No. 6,446,907, to provide sealing for the new “opened” corner defined by the new skirt to allow more direct access to the filter. 
     In order to overcome this problem, the old frame and drip pan could be re-shaped to the new skirt shape, however, the requirement to seal the pan peripherally to the frame in such a case would require extensive and expensive re-working of the peripheral seal structure of the pan. In particular, the pan would require a special seal seat groove to be milled or otherwise manufactured into the edge of the pan. 
     Specifically, since the straight skirt sides extend in a direction intersecting with, and are no longer tangent to, the skirt curve at this corner, the skirt takes on inwardly-facing convex shapes, directed inwardly of the access opening, before flowing into the new expanded inwardly-facing concave corner. This skirt configuration would require a cooperative configuration of the drip pan whose cover would follow that of the skirt. When a drip pan for a corresponding frame is so shaped, the peripheral o-ring sealing the drip pan to the frame cannot be used as with the prior o-ring groove due to the changed configuration of the sealing surfaces. When stretched to fit, the o-ring on the drip pan would not follow this curved portion of the pan because it would span across the corresponding outwardly-facing concave drip pan curves. Thus, the fit of the o-ring would render installation of the pan to the frame problematical and adversely affect the desired seal. 
     In other words, the spanning o-ring would interfere with the corresponding inwardly-facing convex curve of the frame when the pan was inserted therein. This would, in turn, require the provision of a much more expensive and complicated o-ring retaining groove in the peripheral edge of the removable pan. 
     Moreover, the aforesaid problem of visual access to the filter through the corresponding site port has remained a problem. It is desired to enhance the location of the port to facilitate more visual access to the filter and to its “bypass button” from more viewing locations. The retention of the prior site port in its same position relative to the old drip pan, however, would retain the visual disadvantages mentioned. 
     Accordingly, it is one objective to provide an improved leak-proof drip pan apparatus for use in “M” model BLACK HAWK® helicopters. 
     A further objective of this invention is to provide an improved cover and seal for the interior access opening of helicopters such as the BLACK HAWK® “M” model helicopter and those of similar structure. 
     Another object of this invention is to provide a drip pan that will effectively and consistently seal fluid from passage from an engine or transmission compartment to a cabin section of a BLACK HAWK® “M” model helicopter and similar air frames. 
     Another object of this invention is to provide a drip pan which permits quick visual and physical access to the engine or transmission compartment of a BLACK HAWK® “M” model helicopters and similar helicopters without requiring modification to the existing aircraft structure. 
     Another objective of the invention is to more effectively seal a drip pan to the skirt defining a transmission access opening in a BLACK HAWK® “M” model helicopters and similar helicopters. 
     Still another object of this invention is to provide a drip pan that can be attached to the existing structure of a BLACK HAWK® “M” model helicopter and similar helicopters without modification of the existing airframe structure and with minimal intrusion into the helicopter&#39;s cabin section. 
     Another objective of the invention is to provide an improved drip pan for use with BLACK HAWK® “M” model helicopter and similar air frames using an o-ring seal between drip pan and frame, where all peripheral curves in the pan are convex (i.e., outwardly directed) with respect to the pan. 
     Yet another objective of the invention is to provide enhanced visual access to a filter in an “M” model BLACK HAWK® helicopter. 
     SUMMARY OF THE INVENTION 
     In other features and functions, the new helicopter drip pan apparatus herein covers and effectively seals a structural opening in the helicopter without leakage. 
     To these ends, in one embodiment, a drip pan is adapted to cooperate with a frame having an inwardly-facing peripheral surface. The frame is secured to a depending skirt which defines the structural access opening for access to a rotor transmission of a BLACK HAWK® Model “M” helicopter. The access opening also provides access to components, such as an oil filter, attached to the rotor transmission. 
     The drip pan comprises a member having an outwardly-facing peripheral surface. The outwardly-facing peripheral surface is adapted to cooperate with the inwardly-facing peripheral surface of the frame and defines a first pan corner and at least one other pan corner. The first pan corner differs in curvature from the other pan corner. In one embodiment, the member is removably received within the frame in a single orientation. In one embodiment, the first pan corner is defined by a first pan corner radius and the other pan corner is defined by a pan corner radius that is larger than the first pan corner radius. 
     In one embodiment, a helicopter has an access opening defined by a depending skirt having at least two straight sides connected by a corner. The corner is defined by an inwardly oriented concave curve such that an extension of the concave curve intersects an extension of at least one straight side at an angle greater than zero degrees. The drip pan apparatus comprises a drip pan and a frame. The frame is configured to cooperate with the skirt, including the inwardly oriented concave curve. The frame comprises an inwardly-facing first frame corner defined by a first frame corner radius, and at least one other inwardly-facing frame corner defined by a frame corner radius that is greater than the first frame corner radius. The drip pan cooperates with the frame and comprises a first pan corner defined by a first pan corner radius that is configured to cooperate with the first frame corner, and at least one other corner defined by a pan corner radius that is greater than the first pan corner radius. The at least one other pan corner is configured to cooperate with the at least one other inwardly-facing frame corner. 
     In one embodiment, a drip pan apparatus for covering and sealing the helicopter transmission access opening in a helicopter comprises a drip pan and a frame adapted to mount to the helicopter transmission access opening. The frame has an inwardly-facing peripheral surface extending around the frame. The inwardly-facing peripheral surface has a first frame corner defined by a first frame corner shape and at least one other frame corner defined by a frame corner shape that differs from said first frame corner shape. The drip pan has an outwardly-facing peripheral surface extending around the drip pan. The outwardly-facing peripheral surface has a first pan corner defined by a first pan corner shape and at least one other drip pan corner defined by a drip pan corner shape that differs from the first pan corner shape. The first pan corner cooperates with the first frame corner and the drip pan is configured to be selectively affixed to the frame. A seal member is operably disposed between the outwardly-facing peripheral surface and the inwardly-facing peripheral surface when said drip pan is affixed to the frame. 
     In one embodiment, a drip pan is configured to cooperate with a frame secured to a depending skirt, which defines an access opening for access to a rotor transmission of a helicopter. The frame has an inwardly-facing peripheral surface of asymmetrical shape. The drip pan comprises a member having an outwardly-facing peripheral surface of asymmetrical shape operably corresponding to the asymmetrical shape of the inwardly-facing peripheral surface of the frame. A resilient seal is disposed between the inwardly-facing peripheral surface and the outwardly-facing peripheral surface when the member is operably disposed in the frame for sealing the member to the frame, about the peripheral surfaces. 
     In one embodiment, a drip pan apparatus for a rotor transmission access opening in a helicopter comprises a drip pan having a peripheral edge for fitting in the opening. The edge is defined in part by a plurality of corners, one of which is developed about a radius of smaller extent than the radii of the other corners in the plurality. 
     This configuration is attained despite and contrary to the previously conventional wisdom than an o-ring seal could not be used effectively about and around the relatively small radius of the pan corner. According to conventional wisdom, placing the o-ring seal about such a small radius would result in undue stretch of the o-ring. The belief was that the resulting reduction in diameter of the o-ring would, in turn, result in seal efficiency derogation or other seal failure. Contrary to this belief, embodiments of the pan apparatus do not result in a stretched o-ring and, furthermore, do not require the o-ring to fit into any concave areas extending into the pan to avoid an otherwise interference fit between the o-ring and frame upon pan insertion. 
     These and other objectives and advantages will become readily apparent from the following description of embodiments of the invention and from the drawings in which: 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIGS. 1-6  are reproduced herein from the prior U.S. Pat. No. 6,446,907 for clarity of contrast to the present invention and are described in that patent; 
         FIG. 7  is an exploded isometric view of components of the new drip pan apparatus according to one embodiment of the invention; 
         FIG. 8  is a plan view of the drip pan of  FIG. 7  as will be viewed from the cabin section of a helicopter when in use; 
         FIG. 9  is an enlarged view of the new corner structure according to one embodiment of the invention in the upper left-hand corner of  FIG. 8  but illustrating the prior art access port in phantom for comparison; 
         FIG. 9A  is a cross-sectional view of the corner structure in  FIG. 9 , but illustrating the prior art skirt in phantom for comparison; 
         FIG. 9B  graphically illustrates the new frame of the apparatus contrasted with the old skirt and old pan corner orientation; 
         FIG. 10  is a cross-sectional view taken along lines  10 - 10  of  FIG. 8 ; 
         FIG. 11  is an exploded cross-sectional view similar to  FIG. 10  but showing the port cover removed and illustrating the replacement of a filter through the port; and 
         FIG. 12  is an isometric view of the new drip pan (with port covers not shown for clarity) from the perspective of the transmission side of the new drip pan when in use. 
     
    
    
     PRIOR ART 
     Applicant first describes the prior art as in U.S. Pat. No. 6,446,907 for purposes of environment background and contrast with the invention. Item numbers shown in  FIGS. 2-6  when used on  FIGS. 7-12  designate components in  FIGS. 7-12  which are similar or identical to components in  FIGS. 2-6 . 
       FIG. 1  shows a widely known configuration of a typical helicopter  10 . While the typical helicopter  10 , for example, in this prior description was a BLACK HAWK® helicopter as manufactured for the United States by Sikorsky Aircraft Company, Stratford, Conn., it will be appreciated that the drip pan structure described in the prior patents was useful in numerous aircraft and helicopter configurations of other prior makes and models. In this configuration the helicopter  10  had a cabin  12  (dashed outline) in which passengers, equipment and cargo could ride during operation. Located just above the cabin  12  was at least one engine  14  which supplied power to a rotor transmission  16 . The rotor transmission  16  was connected to a shaft  18  which imparted rotary motion to the main rotor  20 . The rotor transmission  16  was also connected via a drive shaft (not shown) to a tail rotor  22 . 
     The rotor transmission  16  required frequent inspection and maintenance to ensure proper operation of the transmission. To facilitate easy and ready access to the rotor transmission, rotor transmission access openings were provided on both the exterior and interior of the helicopter. For example, structural opening  24  was located within the cabin  12 , providing the requisite access to the rotor transmission  16  situated directly above the cabin  12 . Structural opening  24  generally had some type of removable covering to seal the transmission area  16  from the cabin area  12 . To accommodate attachment of a removable covering, a flexible skirt  26  ( FIG. 2 ) was fixedly secured around the periphery of structural opening  24  by rivets  28 . Skirt  26  was many times more flexible than the structural opening  24  to which it attached. 
     As can be further appreciated the rotor transmission  16  as well as the engine  14  required various fluids during their respective operations. Generally, these fluids provided the rotor transmission  16  and the engine  14  with lubrication, cooling, and the like. During operation these fluids may leak and drip from either the engine  14  or rotor transmission  16  or both. To prevent leakage of fluid into the cabin  12  via structural opening  24 , a drip pan apparatus  30 , as shown in  FIG. 2 , was used to cover and seal the structural opening  24 . 
     With specific reference to  FIGS. 2-6 , the drip pan apparatus  30  according to one preferred embodiment of the prior structure had a frame member  32 , a drip pan  34 , and a seal member  36  cooperating together to provide a fluid tight sealing arrangement for structural opening  24 . Frame member  32  had a plurality of lugs  38  disposed about the exterior periphery of frame member  32 . Four lugs  38  were disposed on two sides of the frame member  32  and three lugs  38  were disposed on the other two sides of the frame member  32 . Fasteners  40  cooperated with lugs  38  and threaded retention members  42  ( FIG. 4 ) to secure frame member  32  to skirt  26  attached to structural opening  24 . Once installed, frame member  32  typically remained in place and was not routinely removed from structural opening  24 , although it could be readily removed by simply extracting fasteners  40 . Frame member  32  was many times more rigid than the flexible skirt  26 . 
     Drip pan  34  had a plurality of resilient members  50  which serve to hold drip pan  34  in sealing engagement with frame member  32 . Each resilient member  50  had elongated arms  52  with curved portions  54 . Resilient members  50  were free to pivot about brackets  58 . Curved portions  54  selectively engaged slots  56  opening toward and located about the interior periphery of frame member  32 . To secure drip pan  34  to frame member  32 , the drip pan  34  was pushed into the interior of frame member  32  until the drip pan  34  contacted lip  60  ( FIG. 4 ) which extended around frame member  32  and acted as a stop for drip pan  34 . Only part of the curved portions  54  were resiliently inserted into slots  56 . The installation and the removal of the drip pan  34  was accomplished rather quickly using the resilient members  50  because no tools such as screwdrivers or wrenches were required. Equally important, resilient members  50  were permanently secured to the drip pan  34  by brackets  58 , so the resilient members  50  could not be lost or misplaced when the drip pan  34  was removed to gain full access to the engine  14  and rotor transmission  16 . 
     As shown in  FIG. 4 , seal member  36  was disposed in an outwardly-facing groove  62  which extended around the outer periphery of drip pan  34 . In that application, the term “outwardly-facing” represents a direction substantially parallel to the plane of the drip pan  34  and extending away from the drip pan  34 . As illustrated in  FIG. 2 , the outer periphery of drip pan  34 , which had four straight edges or sides  35   a ,  35   b ,  35   c ,  35   d  connected by curved portions  37   a ,  37   b ,  37   c ,  37   d , conformed to frame member  32  which was comprised of four straight sides or rails  39   a ,  39   b ,  39   c ,  39   d  connected by curved portions  41   a ,  41   b ,  41   c ,  41   d  (shown in  FIG. 3 ). With reference to  FIGS. 5 and 6 , when drip pan  34  was installed into frame member  32 , seal member  36  sealingly engaged inwardly-facing surface  64  of frame member  32  to achieve a fluid tight sealing arrangement between drip pan  34  and the frame member  32 . In this application, the term “inwardly-facing” represented a direction substantially parallel to the plane of the frame member  32  and extending toward the interior of the frame member  32  and the pan  34 . Unexpectedly, seal member  36  provided the necessary sealing engagement between outwardly-facing seal member  36  and inwardly-facing surface  64  despite the fact that groove  62  and surface  64  respectively ran along straight sides  35   a ,  35   b ,  35   c ,  35   d  and  39   a ,  39   b ,  39   c ,  39   d . Typically, peripheral o-ring seals were used in cooperation with annular or curved sealing surfaces such as those defined by curved portions  37   a ,  37   b ,  37   c ,  37   d  and  41   a ,  41   b ,  41   c ,  41   d  (shown best in  FIGS. 2 and 3 ). It was previously felt that peripheral seals used along straight sealing surfaces would provide unacceptable sealing integrity. 
     In one prior drip pan design, a seal was located in a groove opening extending in a direction perpendicular to the plane of the drip pan. The seal would engage a surface which was parallel to the plane of the dip pan. With this arrangement, flexure of the helicopter frame associated with structural opening  24  may breach the seal integrity between the drip pan and the attachment frame causing fluid to leak into the helicopter cabin. Seal member  36  of these  FIGS. 2-6 , however, was a peripheral seal located in outwardly-facing groove  62  to form a fluid seal between the periphery of the drip pan  34  and the inwardly-facing surface  64  of frame member  32 . With this arrangement, flexure of the helicopter frame associated with structural opening  24  did not breach the integrity of the sealing arrangement between the drip pan  34  and the frame member  32 . While the sealing member  36  could be any suitable cross-sectional geometry, seal member  36  was preferably an O-ring. 
     Routine maintenance and inspection of the rotor transmission  16 , does not ordinarily require removal of the entire drip pan  34 . As shown in  FIG. 2 , to accommodate limited access for routine maintenance or inspection, or filter replacement, a plurality of small, removable access port covers  70  were provided in drip pan  34  to allow access through access openings or ports  72  to mechanical linkages in and around the rotor transmission and to allow inspection of the fluid levels associated with the rotor transmission  16 . An access cover  70  for each access opening  72  was removably disposed in sealing engagement covering the access opening  72 . To secure access cover  70  to the access opening  72  in drip pan  34 , each access cover  70  had a resilient member  74  which functioned much like resilient member  54  which secured the drip pan  34  to the frame member  32 . 
     With reference particularly to  FIGS. 5 and 6 , access opening  72  had an annular groove  76  for resiliently receiving curved portion  78  of resilient member  74  to sealingly secure access cover  70  to access opening  72 . Advantageously, no tools were required to operate the resilient members  74  to install or remove the access covers  70 . In addition, brackets  80  permanently secured resilient member  74  to access covers  70  so resilient members  74  could not be lost or misplaced. Each access cover  70  was attached to the drip pan  32  by a suitable attachment device such as a cable or chain  82  so when an inspection procedure was complete the access cover  70  was readily retrieved and positioned into access opening  72 . Each access cover  70  included a seal member  84  disposed in an annular groove  86  extending around the outer periphery of access cover  70 . When access cover  70  was placed into access opening  72 , seal member  84  sealing engaged surface  88  of drip pan  34  which formed part of access opening  72 . Like seal member  36 , seal member  84  formed a peripheral seal between the access cover  70  and the surface  88 . This arrangement improved on prior sealing arrangements which located the seal member between an access cover surface parallel to but outside of the plane of the access cover  70  and the drip pan  32 , i.e., a face seal. As discussed above, the peripheral seal arrangement provided improved seal integrity even if the drip pan  34  flexed. Preferably, seal member  84  was an O-ring. 
     To facilitate the removal of accessing covers  70  from access openings  72 , pull handles  90  were attached to access covers  70 . Fasteners  92  fixedly secured pull handles  90  to access covers  70 . Preferably, pull handles  90  were cable or chain. 
     During the preflight procedure of a helicopter, critical filters must be checked and determined operational before the helicopter is allowed to fly. To facilitate this inspection process, at least one of the access or port covers  70  had a transparent cover member  94  ( FIG. 5 ) so that a bypass button or valve associated with a particular filter could be checked visually through the access cover  70  without physically removing the access cover  70  from the access opening or port  72 . A seal member  96  was disposed between the transparent cover member  94  and access cover  70  to prevent fluid leakage therebetween. Preferably, the transparent cover member  94  was made from acrylic such as Plexiglass™. 
     With reference to  FIGS. 2-4 , drip pan  34  had a drain hole  100  to drain fluid collected by the drip pan  34 . Drain hole  100  included strainer members  102  (shown in  FIG. 4 ) to keep foreign objects coming to rest on the drip pan  34  from clogging the drain hole  100 . A drain tube  104  was attached to the drain hole  100  to direct the collected fluid to a catch basin (not shown) or to the exterior of the helicopter. The drain tube  104  was made preferably from metal tubing having a diameter of about 0.625 inches. Alternatively, a removable stopper could have been used with drain hole  100  for selective drainage. 
     In at least one application, as depicted in  FIGS. 3 and 4 , the drip pan apparatus  30  could have been used on helicopters having carrousel bars added to the interior of the helicopter cabin  12  (shown in  FIG. 1 ) to support, for example, litters used for transporting patients in need of medical attention. Typically, at least one carrousel bar passed directly under the drip pan apparatus  34 . To accommodate a carrousel bar  108  (phantom), elongated recesses  110  were provided in frame member  32  so that the frame member  32  did not interfere with the installation and operation of the carrousel bar  108 . 
     In still another application, the drip pan apparatus  30 , and more specifically the frame member  32 , could have interfered with access to an oil filter associated with the rotor transmission  16  when the drip pan apparatus  30  is installed. To provide for removal of an oil filter  112  ( FIG. 6 ) from the rotor transmission  16 , a portion of frame member  32  was machined away as shown by numeral  114  so that the oil filter  112  could be removed along a line not perpendicular to the drip pan apparatus  30 . During the removal or installation of oil filter  112 , the drip pan  34  was removed to provide even greater access to the oil filter  112 . Frame member  34  was machined just enough to permit removal of oil filter  112 , and maintain sealing engagement between seal member  36  and surface  64  of frame member  34 . 
     To provide further access to the oil filter  112 , the geometry of frame member  32  could be modified. More specifically and with reference to  FIG. 3 , frame member  32  was comprised of four straight sides or rails  39   a ,  39   b ,  39   c ,  39   d  connected by curved portions  41   a ,  41   b ,  41   c ,  41   d , where each rail  39   a ,  39   b ,  39   c ,  39   d  had a respective width indicated by W 1 , W 2 , W 3 , W 4 . To provide improved access to the oil filter  112  (shown in  FIG. 6 ), the opening defined by rails  39   a ,  39   b ,  39   c ,  39   d  was shifted to the left in  FIG. 3  such that the respective widths W 1 , W 2 , W 3 , W 4  of rails  39   a ,  39   b ,  39   c ,  39   d  were not all equal to one another. Preferably, the difference between W 2  and W 4  was about one quarter of an inch. This transverse shift of the opening helped to accommodate removal of the oil filter  112  which was generally located in the compartment above the drip pan apparatus  30  near the upper left hand corner of the drip pan apparatus  30  shown in  FIG. 3 . 
     Accordingly, the prior art disclosed above provided an improved cover and seal for the interior access opening of a helicopter such as the prior BLACK HAWK® helicopter models. As such, that drip pan apparatus sealed against fluid passage from the engine or transmission compartment to the cabin section of a prior model BLACK HAWK® helicopter. In addition, that drip pan apparatus permitted quick access to the engine or transmission compartment of that helicopter, without requiring modification to the existing aircraft structure. 
     The new invention described below provides the same features and advantages in a model “M” BLACK HAWK® helicopter, but also accommodates the new relieved skirt version of the new “M” model, providing more direct filter access, while still providing the desirable seal functions noted above. 
     DETAILED DESCRIPTION OF INVENTION 
     Embodiments of the invention described herein differ from that prior art of U.S. Pat. No. 6,446,907 (the &#39;907 patent) in the structure of the elements defining the asymmetric corner components of a drip pan apparatus  200  shown in  FIGS. 7-12 . In other aspects, such as in materials of construction and function, in one embodiment, the drip pan apparatus  200  of this invention is like that described in said patent. Accordingly, any item numbers found in  FIGS. 7-12  which are the same as those in  FIGS. 2-6  designate like components. Moreover, the helicopter  10  of  FIG. 1  is similar in outward appearance to the “M” model BLACK HAWK® helicopter and for that reason is used herein to illustrate an overall helicopter environment in which the new drip pan apparatus  200  of  FIGS. 7-12  is used. 
     Turning to  FIG. 1 , there is shown therein a helicopter  10  representing generally for this invention a BLACK HAWK® Model “M” helicopter of the type made by the Sikorsky Aircraft Company of Stratford, Conn., and other helicopter air frames similar thereto. Like the prior BLACK HAWK® helicopter, the BLACK HAWK® “M” model helicopter has a cabin  12  and an engine or turbine  14  which powers a rotor transmission  16 . Shaft  18  transmits rotary motion to a rotor  20  while the transmission  16  is also connected by a drive element (not shown) to tail rotor  22 . Like the BLACK HAWK® helicopter, the BLACK HAWK® Model “M” helicopter has a fixed transmission access opening but designated  205  in  FIG. 1 . The “M” model embodies a variety of other differences from the prior BLACK HAWK® helicopter of FIG. 1 of the &#39;907 patent but in ways not relevant to this invention except as further described. 
     Turning now to  FIG. 7 , the drip pan apparatus  200  has application for use in a “M” model BLACK HAWK® helicopter and other similar airframes having the fixed transmission access opening  205  defined by an air frame member  206  and a depending flexible skirt  207  attached thereto. Skirt  207 , like skirt  26  of  FIG. 2 , is many times more flexible than air frame member  206  to which skirt  207  is attached. Skirt  207  of the BLACK HAWK® Model “M” helicopter has two straight portions  208 ,  209  and an expanded corner  210  therebetween, as well as a remaining periphery defined by straight sections and corners. Note that skirt  207 , between straight portions  208 ,  209 , forms two inwardly-facing convex curves  231 ,  232  and an inwardly-facing concave curve  230 . The concave curve  230  is oriented inwardly at the corner  210  so that straight portions  208 ,  209  flow into the curves  231 ,  232  which are tangent to, or flow into, curve  230 . It will be appreciated that an extension of each straight portion  208 ,  209  would intersect an extension of curve  230  at an angle greater than zero degrees. In this manner, the corner  210  of skirt  207  has been expanded outwardly of the location of the same corner of the prior skirt of the &#39;907 patent. 
     In one embodiment of this invention, corner  210  is asymmetric to the other corners (not shown) of the skirt  207 , which other corners may remain in the same configuration. In other words, the corner  210  is defined by a shape that is different than the other corners of the skirt  207 . By contrast, in the access opening covered by the prior drip pans of the &#39;907 patent all four corners of the prior skirt were symmetrical. As is described below, the drip pan apparatus  200  sealingly cooperates with the skirt  207 , including the corner  210 , to cover access opening  205  to prevent fluid drippings from entering the cabin  12  of the Model “M” BLACK HAWK® helicopter  10 . 
     To that end, and with continued reference to  FIG. 7 , the drip pan apparatus  200  includes a frame  215  having a corner structure  216 , a drip pan  220  having a new corner  221 , and an o-ring seal  222 . In use, the frame  215  is secured to air frame member  206 . As shown, rivets  201  or other fasteners may secure the frame  215  to the skirt  207  and air frame  206  through tabs  202 . A flexible sealing media (not shown), such as PROSEAL™ (manufactured by PRC Desoto International, Inc. of Indianapolis, Ind., a PPG Company) or other sealant may be used to seal the frame  215  to skirt  207  when the frame  215  is secured to the air frame  206 . 
     Thereafter, drip pan  220  is inserted into the frame  215  in the position illustrated in  FIGS. 7 and 8 , where seal member or o-ring  222  creates a peripheral seal between the drip pan  220  and frame  215  and provides continuous sealing during air frame flexure and without the disadvantage of any face seal in this regard. Attachment members  50  releasably secure the drip pan  220  to the frame  215  similarly to the prior pan of the &#39;907 patent where elongated arm  52  with curved portions  54  selectively engage slots  56 . Once the pan  220  is inserted into the frame  215 , a drain line  104  may be connected to pass drainage fluids from drain  100 . 
     As set forth above, and with continued reference to  FIG. 7 , the frame  215  accommodates the outward expansion of the skirt  207  at corner  210 . In particular, as is described in more detail below, corner structure  216  of frame  215  has been expanded outwardly to match the outward expansion of the skirt  207 , as shown. In addition, the radius of the inwardly-facing frame corner represented at  242  has been significantly reduced to correspond to a relatively small radius of corner  221  of drip pan  220 . 
     With reference to  FIGS. 7 and 8 , the frame  215  comprises four straight sides or rails  247   a ,  247   b ,  247   c ,  247   d  connected by curved portions  249   a  and  249   b , the corner structure  216 , and curved portion  249   c , respectively. The rails  247   a ,  247   b ,  247   c ,  247   d ; the curved portions  249   a ,  249   b ,  249   c ; and the corner structure  216  collectively define the inwardly-facing peripheral surface  235  (shown in  FIG. 7 ). Each rail  247   a ,  247   b ,  247   c ,  247   d  has a respective width indicated by W 5 , W 6 , W 7 , W 8  (labeled in  FIG. 8 ) measured from the inwardly-facing peripheral surface  235  to an outer periphery of the frame  215 . 
     In one embodiment and with reference to  FIG. 7 , the width of the corner structure  216  varies to accommodate the expansion of the skirt  207 , specifically the curve  230 , at corner  210 . The variation in the width of the corner structure  216  is shown in  FIGS. 8 and 9A . As shown, the width of the corner structure  216  transitions from the width W 7  of rail  247   c  to width W 8  of rail  247   d . In one embodiment, at least a portion of the corner structure  216  is wider than either adjacent rail  247   c  or rail  247   d . Specifically, the width of the corner structure  216  at one location, for example at width W 9  or width W 11  may be greater than either width W 7  or width W 8 . By way of further example, as depicted in  FIGS. 8 and 9A , the width of corner structure  216  may transition from width W 7  to width W 9  that is greater than width W 7 . The width of the corner structure  216  then decreases from width W 9  into an inwardly-facing frame corner  242  or width W 10  that is less than the width W 9 . Further, the width of the corner structure  216  then increases to width W 11  before transitioning to a narrower width W 8  of rail  247   d . It will be appreciated that the width of the corner structure  216  may vary smoothly from W 7  to W 8 . 
     Furthermore, to provide improved access to the filter F (shown in  FIG. 11 ), the opening defined by rails  247   a ,  247   b ,  247   c ,  247   d  may be shifted to the left in  FIG. 8  such that the respective width W 6  and width W 8  of rails  247   b  and  247   d  are not equal to one another. This transverse shift of the opening helps to accommodate removal of the filter which is generally located in the compartment above the drip pan apparatus  200 . It will be appreciated that widths W 5 , W 6 , W 7 , W 8  may not be equal to any of the widths W 1 , W 2 , W 3 , W 4  of  FIG. 3 . 
     With regard to the pan  220  and with further reference to  FIG. 7 , the pan  220  has an outwardly-facing peripheral surface  239 , which has four straight sides  250   a ,  250   b ,  250   c ,  250   d  connected by corners  211 ,  212 ,  213 , and corner  221 . The outwardly-facing peripheral surface  239  conforms to the inwardly-facing peripheral surface  235 . As set forth above, the radius of the corner  242  is significantly reduced to correspond to the radius of the corner  221  of the pan  220 . As shown in  FIGS. 7 and 8 , the corner  221  is developed about a much smaller radius than its other pan corners  211 - 213 . It will be appreciated that the variation of the radius configuration of the corner  221  from the corners  211 - 213  simplifies installation of the pan  220  by preventing incorrect installation since the pan  220  may be inserted into the frame  215  in only one orientation. 
     Additionally, in one embodiment, the drip pan  220  defines a plurality of access ports  223 - 226  and a filter access port  228 , which is provided with a removable port cover  229  having a view window  236  and frame  237 . Once the drip pan  220  is secured to the frame  215 , the status of a filter or other component in or on the transmission may be viewed through the view window  236 . Also, any one or more of the access covers  70  may be removed from its respective access port  223 - 226  such that routine maintenance and inspection of components within access opening  205  may be performed. In one embodiment, the drip pan apparatus  200  differs from that pan apparatus of the prior &#39;907 patent only in the area A as identified in  FIG. 8 . 
       FIGS. 9 ,  9 A, and  9 B illustrate area A of  FIG. 8  in greater detail. As shown in  FIG. 9 , the extra material provided by expansion of the pan  220  out to the smaller radius corner  221  allows port  228  to be moved out toward the corner  221  and more directly under (when in use) a filter compared to the prior art port  72  (shown in phantom line). Thus positioned, the port  228  provides improved visual access to components on the transmission, such as the filter, and any indicator or “bypass button” thereon, indicating the operational status thereof. In other words, the indicator or button can be more easily viewed through filter access port  228  from more widely varied viewing positions than in the prior drip pan configuration. 
     Similarly, with respect to the prior art skirt and the new skirt  207 , the prior skirt is identified in phantom lines at  240  in  FIG. 9A . In one embodiment of this invention, as described above, the new skirt  207  is expanded outwardly as shown in the solid lines at this corner to form  242 . The smaller radius corner  242  corresponds to small radius corner  221  of the pan  220 , shown in  FIG. 9 .  FIG. 9B  graphically illustrates the comparison of the new frame  215  and the respective orientations of the old skirt  26  designated  240  and the old prior art pan corner  245  (both shown in phantom line). 
     With continued reference to  FIG. 9B , in one embodiment, radius R 1  of the prior art pan corner  245  may be of greater length than the radius R 2  of corner  221  in the drip pan apparatus  200 , thereby allowing the filter access port  228  to be moved more directly in line with a filter. However, even though the radius of corner  221  is smaller, as shown in  FIG. 7 , the o-ring seal  222  situated between the outwardly-facing peripheral surface  239  and the inwardly-facing peripheral surface  235  unexpectedly seals the drip pan apparatus  200  and prevents egress of fluids from access opening  205 . 
     With reference now to  FIGS. 9A ,  10 , and  11 , in order for the frame  215  to cooperate with the skirt  207  and form a small radius at the corner  242  (shown in  FIG. 7 ), the frame  215  may include an inner rim  218  and an outer rim  219  forming a trough  234  having a floor at  217  therebetween. Preferably, the rim  218  at corner structure  216  is at least partially expanded outwardly from its position in the prior pan to accommodate skirt  207  and form the corner  242 . Accordingly, trough  234  may vary in width “L” such that the width of corner structure  216  varies, as described above, as required about frame  215  to accommodate the concave curve  230  (shown in  FIG. 7 ). 
     Furthermore, this corner structure at  216  will be appreciated by contrasting prior art  FIGS. 5 and 6  with new  FIGS. 10 and 11 . In  FIGS. 10 and 11 , the frame  215  has been expanded at  217  to the length “L”. In prior  FIGS. 5 and 6 , the frame was not so expanded. Thus, skirt  207  (at concave curve  230 ) has been moved significantly to the left as viewed in  FIGS. 10 and 11  as compared to the prior frame. According to embodiments disclosed herein, a filter F ( FIG. 11 ) can advantageously be removed or inserted in a direction along and parallel to an elongated filter axis  204  when the removable port cover  229  is removed from the pan  220 . 
     If desired, in one embodiment, a trim ring (not shown) can be applied to aesthetically cover the frame  215 , leaving only drip pan  220  and the ports  223 - 226 ,  228  clear for use or for overall removal of the drip pan  220  for access to the transmission  16 . 
     Moreover, and if desired, while o-ring  222  is shown in a simple, outwardly facing, parallel sided groove, other groove shapes capturing the o-ring  222  to the drip pan  220  (or alternatively to frame  215 ) may be used. It will also be appreciated that the scale of the figures such as in  FIGS. 10 and 11  may be changed, such that o-ring  222  is actually in more of an oval or circular cross-section, or more of a squared configuration than as shown in these figures, and more like, for example, the cross-sectional configuration of peripheral seal  238  in  FIGS. 10 and 11 . 
     With reference to  FIGS. 7 and 12 , while the corners of the frame  215  and the pan  220  are drawn and referenced as being defined by radii, one skilled will appreciate that other shaped corners may be utilized. Even so, the corner  221  and the corner  242  are cooperatively shaped. The remaining corners of the pan  211 - 213  cooperate with their respective other corners (unlabeled) of the frame  215 . The shape at the corner  221  is, however, different than the shape of the corners at  211 - 213 . Thus, the pan  220  may be inserted into the frame  215  in only one orientation. 
     The drip pan  220  otherwise performs the same sealing and access functions for the “M” Model as in the prior BLACK HAWK® helicopter without requiring air frame modifications and without utilizing face seals to seal any of the ports  223 - 226  and  228  or to form the seal between the drip pan  220  and the frame  215 . 
     While the present invention has been illustrated by the description of embodiments thereof, and while the embodiments have been described in considerable detail, they are not intended to restrict or in any way limit the scope of the appended claims to such detail. Additional advantages and modifications will readily appear to those skilled in the art. The invention in its broader aspects is therefore not limited to the specific details and drawings shown and described. Accordingly, departures may be made from such details without departing from the scope of the general inventive concept.