Abstract:
A mounting system for use in mounting a gas turbine engine having an engine core to an aircraft comprises an engine support arrangement and front and rear mounting assemblies to mount the engine support arrangement to a casing surrounding the engine core. Each of the front and rear mounting assemblies comprises a plurality of circumferentially spaced mounting members to effect the aforesaid mounting of the engine support arrangement to the casing.

Description:
BACKGROUND 
     This invention relates to mounting systems for use in mounting gas turbine engines on to the fuselages of aircraft. 
     The mounting of gas turbine engines above the fuselage of an aircraft has advantages with respect to noise. However, there may be some issues concerning rotor failures that need to be addressed. 
     SUMMARY 
     According to one aspect of this invention, there is provided an aircraft comprising a gas turbine engine connected thereto via a pylon, the engine having a rotational axis, a core engine and a casing therearound, the gas turbine engine is attached to the aircraft via a mounting system, the mounting system comprises a frame arrangement, front and rear mount assemblies and a load spreading element, the frame arrangement connects to the front and rear mount assemblies that each comprise at least two circumferentially spaced apart mounting members to connect to the casing and the load spreading element extending across the frame arrangement includes three axially spaced connecting members which connect the load spreading element and, thereby, the frame arrangement and the engine, to the pylon. 
     Preferably, each of the front and rear mounting assemblies comprises three circumferentially spaced mounting members. 
     Preferably, the casing defines a bypass duct between the casing and the engine core to provide a path for the flow of air therethrough. 
     Preferably, the load spreading element is connected to the frame arrangement via three axially spaced apart connecting members. 
     Preferably, the load spreading element is elongate and extends across the frame arrangement. 
     Preferably, the frame arrangement comprises an arrangement of struts. 
     Advantageously, the casing is supported on the engine core by a plurality of A-frames. 
     Preferably, the A-frames are arranged in a warren truss arrangement. 
     Preferably, the A-frames are provided towards or at the rear of the engine core. 
     Preferably, the A-frames extend in a single plane generally circumferentially around the core. 
     Preferably, the rear mounting assembly is mounted on the casing in a plane of the A-frames. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       An embodiment of the invention will now be described by way of example only, with reference to the accompanying drawings, in which: 
         FIG. 1  is a diagrammatic front view of an aircraft showing the position of the engines; 
         FIG. 2  is a side view of one of the engines shown in  FIG. 2 ; 
         FIG. 3  is a rear view of the engine shown in  FIG. 2 ; and 
         FIG. 4  is a side view showing an impact on a mounting member. 
     
    
    
     DETAILED DESCRIPTION OF EMBODIMENTS 
     Referring to  FIG. 1 , there is shown a diagrammatic rear view of an aircraft  10 , with the wings and tail removed for clarity. The aircraft  10  comprises a fuselage  12  and two engines  14 ,  16  connected to the fuselage  12  by pylons  18 ,  20 . 
     As can be seen, the engines  14 ,  16  are arranged above the fuselage and extend at an angle of between 30° to 60° to the horizontal. As a result, in the event of failure of one engine, there is a danger that the fragments of the failed component could strike the other engine. For example, as shown in  FIG. 1 , a fragment  22  of a disc of the engine  14  has broken therefrom and is directed towards the engine  16  as shown by the arrow A. It has been calculated that the failure of a disc causing it to break into a fragment of approximately a one third segment of a disc can cause the worst case ballistic impact. 
       FIG. 2  shows the engine  16  having an upstream or front region  24  and a downstream or rear region  26 . The engine  16  comprises a core  28  shown in broken lines, which is surrounded by a casing  29 . The casing  29  defines with the core  28  a bypass duct  30 . A fan  32  is provided towards the front  24  of the engine  16  and drives some of the air through the core  28  and the remainder of the air through the bypass duct  30  to provide the propulsive force. It will be appreciated that the structure of the engine  14  corresponds to the structure of the engine  16 . 
     A mounting system  40  is provided on the casing  29  to enable the engine  16  to be attached to the fuselage  12  by the pylon  20  (not shown in  FIG. 2 ). 
     The mounting system  40  comprises a front mounting assembly  42  and a rear mounting assembly  44 . The front mounting assembly  42  is provided in a front mount plane  46 , and the rear mounting assembly is provided in a rear mount plane  48 . Each of the front and rear mounting assemblies comprises three mounting members  50 A,  50 B,  50 C which are spaced from one another circumferentially around the respective front and rear mounting planes  46 ,  48 . 
     The mounting system  40  further includes an engine support arrangement  52  in the form of a frame arrangement comprising a plurality of struts  54  in the form of a warren truss arrangement. A load spreading element in the form of an elongate brace  56  extends across the mounting system  40 , and can provide the support to the struts  54 . Each of the connecting members  50 A,  50 B,  50 C comprises a link  58  (see  FIG. 3 ) which connects the frame arrangement  52  to lugs  60  provided on the casing  29 . 
     The mounting members  50 A,  50 B,  50 C are spaced from each other by a distance which is greater than one third of the circumference of the largest disc. Since the breaking off of one third of a disc is calculated to provide the greatest ballistic impact, by spacing the mounting members  50 A,  50 B,  50 C from one another by a distance greater than this dimension, the impact of the disc cannot occur on more than one of the mounting members. As a result, a fragment of a disc striking the mounting system  40  can, at worse, strike only one of the mounting members  50 A,  50 B or  50 C. In such a case, the load from the engine is  10  is borne by the remaining mounting members. 
     The brace  56  extending across the frame arrangement  52  includes three axially spaced connecting members  61  which connect the brace  56  and, thereby, the frame arrangement  58  and the engine  16 , to the pylon  20  to provide the connection of the engine  16  to the fuselage  12 . 
     Referring particularly to  FIG. 3  which shows a rear view of the engine  16 , it can be seen that the rear core  28  is connected to the casing  29  by means of a plurality of A frames  62 . The A frames  62  extend in substantially the same plane around the casing  29 . The rear mount plane  48  can be arranged in the same plane as the A frames  62  and the two outer connecting members  50 A can be connected to the casing  29  in the regions of two of the A frames  62 . This provides further strength for supporting the engine  16 . 
     Still referring to  FIG. 3 , the casing  29  is surrounded by hinged cowls  64 , which can be opened to allow maintenance on the engine  16 . The brace  56  supports the hinges for the cowls  64 . 
     Referring to  FIG. 4 , there is shown a further drawing of the engine shown in  FIG. 2 , in which the mounting member  50 C in the front mounting plane  56  has been struck by a failed component, such as a fragment of a disc, of the other engine on the aircraft. As a result of the failure of the front mounting member  50 C, the frame arrangement  52  transmits the load that was supported by the front mounting member  50 C on to the two remaining mounting members  50 A,  50 B in the front plane  46 . The plane arrangement  52  also transferred some of this load to the three mounting members  50 A,  50 B,  50 C in the rear mounting plane  48 . 
     Various modifications can be made without departing from the scope of the invention, for example, the frame arrangement  52  could be replaced by an arrangement of beams riveted together, which may be in the form of a generally monolithic structure, or by any other suitable support arrangement.