Patent Publication Number: US-2023159179-A1

Title: Engine pylon for coupling a jet engine to a wing of an aircraft

Description:
CROSS-REFERENCES TO RELATED APPLICATIONS 
     This application claims the benefit of the French patent application No. 2112256 filed on Nov. 19, 2021, the entire disclosures of which are incorporated herein by way of reference. 
     FIELD OF THE INVENTION 
     The present invention relates to an engine pylon for mounting a jet engine beneath the wing of an aircraft, and to an aircraft comprising a jet engine, a wing and such an engine pylon for mounting the jet engine beneath the wing. 
     BACKGROUND OF THE INVENTION 
     Usually, for an aircraft, a propulsion unit comprises a jet engine which is fixed beneath a wing of the aircraft using an engine pylon. 
     First connecting means fix the jet engine to the engine pylon. These connecting means conventionally comprise a forward engine mount, a rear engine mount and reaction rods which absorb the thrust forces generated by the jet engine. 
     Second connecting means fix the engine pylon to the wing. These second connecting means react and absorb the bending moments and shear forces at the interface between the engine pylon and the wing. An example of such an arrangement is described in document US-A-2016/0221682. 
     According to one embodiment of the prior art, the engine pylon is made up of a primary structure allowing load transfer and formed of a box structure made up of an upper spar, of a lower spar and of two lateral panels connecting the two spars and of internal ribs distributed along the box structure. Producing the box structure therefore consists in producing four rows of fish-plating, namely one row between the upper spar and each lateral panel and one row between the lower spar and each lateral panel. 
     According to another embodiment of the prior art, the engine pylon is made up of a primary structure formed of a box structure made up of an upper spar, of a lower spar and of two lateral panels connecting the two spars, of internal ribs distributed along the box structure and of four brackets distributed at the four corners of the box structure. Creating the box structure then consists in producing eight rows of fish-plating, namely two rows per bracket. 
     The primary structure is covered by a secondary structure which forms an exterior fairing having an aerodynamic exterior surface and under which systems (fuel, electric, oil, etc. systems) can be installed. 
     Even though such installations are satisfactory, they are relatively heavy because all of the elements are made of metal and the assembly process is complex with various layers needing to be stacked and component parts needing to be assembled sequentially one after another. 
     SUMMARY OF THE INVENTION 
     It is an objective of the present invention to propose an engine pylon for mounting a jet engine beneath the wing of an aircraft where the engine pylon has a particular assembly enabling a saving in weight and in assembly time. 
     To this end, what is proposed is an engine pylon for mounting a jet engine beneath a wing of an aircraft, the engine pylon comprising:
         an upper spar having an inverted U-shaped profile with a roof and two lateral walls extending downwards from the roof,   a lower spar having a U-shaped profile with a bottom and two lateral walls extending upwards from the bottom, where each lateral wall of a spar has a free end extending until it comes into the vicinity of the free end of the lateral wall of the other spar,   fixing means for fixing the free end of a lateral wall of one spar to the free end of the lateral wall of the other spar, and   a plurality of ribs distributed along the length of the lower spar and housed between the upper spar and the lower spar, where each rib has a top end fixed to each lateral wall of the upper spar and a bottom end fixed to the lower spar,       

     wherein the engine pylon comprises, for each rib, a pad housed in the lower spar and secured thereto, and each pad has a transverse wall which extends transversely with respect to the lower spar and has a fixing zone at which the bottom end of the associated rib is fixed. 
     Such an engine pylon thus offers a reduced number of component parts and a single row of fixings per side, enabling a saving in weight and in assembly time. 
     Advantageously, the fixing zone takes the form of a cavity in the transverse wall in which cavity the bottom end of the associated rib is housed. 
     Advantageously, the top end comprises a web extending transversely with respect to the upper spar and, on each side of the web, a flange secured to the web, and each flange bears against an internal face of a lateral wall of the upper spar and is fixed to the lateral wall. 
     Advantageously, the lower spar and the pads are made of metal and the upper spar is made of composite materials. 
     Advantageously, the upper spar is shaped to form an aerodynamic exterior fairing. 
     According to one particular embodiment, an internal face of the free end of each lateral wall of the upper spar bears against an external face of the free end of a lateral wall of the lower spar, in the region where a lateral wall of the upper spar is superposed on a lateral wall of the lower spar, the lateral walls have coaxial through-bores passing through them, and the fixing means comprise, for each pair of coaxial through-bores, a shanked fastener which has a shank that is inserted into the through-bores and a head at each end of the shank so as to sandwich the lateral walls. 
     According to one particular embodiment, the free end of each lateral wall of the upper spar is butted against the free end of a lateral wall of the lower spar, the free end of each lateral wall has through-bores passing through it, the fixing means comprise, on the one hand, for each pair of butted-together lateral walls a fishplate placed against an external face of each lateral wall of the pair, where each fishplate has, for each through-bore of the associated pair, a complementary through-bore coaxial with the through-bore and, on the other hand, for each through-bore a shanked fastener which has a shank that is inserted into the through-bore and into the coaxial complementary through-bore and a head at each end of the shank so as to sandwich the associated fishplate and lateral wall. 
     According to one particular embodiment, the free end of each lateral wall of the lower spar has a plurality of housings where each has a contact wall roughly (+/−10 degrees) perpendicular to the associated lateral wall of the upper spar, the edge face of the free end of each lateral wall is positioned against the contact walls of the associated housings, each contact wall has a through-bore of which the axis is roughly (+/−10 degrees) parallel to the associated lateral wall of the upper spar, for each through-bore, the associated lateral wall of the upper spar has a first bore of which the axis is perpendicular to the axis of the through-bore and a second bore coaxial with the through-bore and opening into the first bore, and the fixing means comprise, for each through-bore, a sleeve nut housed in the first bore and a screw of which the shank passes successively through the through-bore, and the coaxial second bore to screw into the sleeve nut in the associated first bore. 
     The invention also proposes an aircraft comprising a wing, a jet engine and an engine pylon according to one of the preceding variants, fixed between the wing and the jet engine. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The abovementioned features of the invention, together with others, will become more clearly apparent from reading the following description of one exemplary embodiment, the description being given in connection with the attached drawings, among which: 
         FIG.  1    is a side view of an aircraft according to the invention, 
         FIG.  2    is a side view of an engine pylon according to the invention and assembled between a wing and a jet engine, 
         FIG.  3    is a view in section on III-III of the engine pylon of  FIG.  2   , 
         FIG.  4    is an exploded view of a lower spar and of a rib according to the invention, 
         FIG.  5    is a view of assembly detail V of  FIG.  3    according to a first embodiment of the invention, 
         FIG.  6    is a view of assembly detail V of  FIG.  3    according to a second embodiment of the invention, and 
         FIG.  7    is a view of assembly detail V of  FIG.  3    according to a third embodiment of the invention. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       FIG.  1    shows an aircraft  10  which comprises a propulsion system  100  with a jet engine  102  fixed to a wing  104  of the aircraft  10  by means of an engine pylon  106  according to the invention. 
     In the description that follows, terms relating to a position are considered with reference to an aircraft in the normal flying position, which is to say as depicted in  FIG.  1   , and “front” and “rear” positions are considered with respect to the front and the rear of the jet engine and with respect to the direction of forward travel of the aircraft  10  when the jet engine  102  is in operation. 
     In the description that follows and by convention, X is the name given to the longitudinal direction of the jet engine which is parallel to the longitudinal axis of the jet engine, Y is the name given to the transverse direction which is horizontal when the aircraft is on the ground, and Z is the vertical direction which is vertical when the aircraft is on the ground, these three directions X, Y and Z being mutually orthogonal. 
     The jet engine  102  has a revolution shape about its longitudinal axis and is surrounded by a nacelle made up of panels forming an aerodynamic exterior surface. Likewise, the wing  104  has a structure surrounded by a skin forming an aerodynamic exterior surface. 
     The engine pylon  106  forms a rigid structure. 
       FIG.  2    shows an example of an installation of the engine pylon  106  according to the invention without the exterior fairings between the wing  104  without the skin and the jet engine  102  without the nacelle. 
     The engine pylon  106  takes the form of a box structure which is fixed between the jet engine  102  and the wing  104 . 
     In the embodiment of the invention that is depicted here, the engine pylon  106  is fixed to the jet engine  102  by first connecting means comprising a front engine mount  202 , a rear engine mount  204  and reaction rods  205  which absorb the thrust forces generated by the jet engine. 
     In the embodiment of the invention that is depicted here, the engine pylon  106  is fixed to the wing  104  by second connecting means comprising a set of connecting rods  206   a - c.    
     These connecting means are given here by way of example and may adopt other forms known to those skilled in the art. 
       FIG.  3    shows the engine pylon  106  and  FIG.  4    shows certain components for creating the engine pylon  106 . 
     The engine pylon  106  takes the form of a box structure and has a longitudinal midplane P parallel to the plane XZ and passing through the longitudinal axis X of the jet engine  102 . 
     The engine pylon  106  comprises an upper spar  302  extending roughly (+/−10 degrees) parallel to the longitudinal direction X and having, in a plane perpendicular to the longitudinal direction X, an inverted U-shaped profile with a roof  302   a  and two lateral walls  302   b - c  which extend downwards from the roof  302   a  on each side of the longitudinal midplane P. There is thus a port-side lateral wall  302   b  and a starboard-side lateral wall  302   c.    
     The engine pylon  106  comprises a lower spar  304  extending roughly (+/−10 degrees) parallel to the longitudinal direction X and having, in a plane perpendicular to the longitudinal direction X, a U-shaped profile with a bottom  304   a  and two lateral walls  304   b - c  which extend upwards from the bottom  304   a  on each side of the longitudinal midplane P. There is thus a port-side lateral wall  304   b  and a starboard-side lateral wall  304   c.    
     Each lateral wall  302   b - c ,  304   b - c  of a spar  302 ,  304  has a free end which extends until it comes into the vicinity of the free end of the lateral wall  304   b - c ,  302   b - c  of the other spar  304 ,  302 . 
     The engine pylon  106  also comprises fixing means for fixing the free end of a lateral wall  302   b - c ,  304   b - c  of one spar  302 ,  304  to the free end of the lateral wall  304   b - c ,  302   b - c  of the other spar  304 ,  302 . 
     Thus, the free end of the port-side lateral wall  302   b , or respectively the starboard-side lateral wall  302   c , of the upper spar  302  is fixed to the port-side lateral wall  304   b , or respectively to the starboard-side lateral wall  304   c , of the lower spar  304 . 
     There is therefore one row of fixings per side, namely a first row of fixings  306   b  for fixing the free ends of the respective lateral walls  302   b  and  304   b  and a second row of fixings  306   c  for fixing the free ends of the respective lateral walls  302   c  and  304   c  of the spars  302  and  304  to one another requiring a reduced number of fixing means. 
     The engine pylon  106  also comprises a plurality of ribs  308  which are housed in the box structure formed by the upper spar  302  and the lower spar  304  and which are distributed along the length of the lower spar  304 . 
     Each rib  308  has a top end  308   a  which is fixed to each lateral wall  302   b - c  of the upper spar  302  and a bottom end  308   b  which is fixed to the lower spar  304 . 
     The ribs  308  connect the upper spar  302  and the lower spar  304  along a plurality of vertical connecting planes distributed along the length of the spars  302  and  304  and give the engine pylon  106  stability and transfer torsional loads (Mx). 
     Such an engine pylon  106  thus has a reduced number of component parts and a single row of fixings per side, enabling a saving in weight and in assembly time. 
       FIG.  4    shows an exploded view of the lower spar  304  and of a rib  308 . 
     The engine pylon  106  comprises, for each rib  308 , a pad  402  housed in the lower spar  304  and secured thereto. The lower spar  304  and the pad  402  may be one and the same single component or two components fixed together. 
     Because the ribs  308  are distributed over the length of the lower spar  304 , there is also a plurality of pads  402  distributed along the length of the lower spar  304 . 
     In the embodiment of the invention that is depicted in  FIGS.  3  and  4   , each pad  402  has a transverse wall  406  which extends transversely with respect to the lower spar  304 , which is to say, perpendicular to the longitudinal direction X. The transverse wall  406  has a fixing zone  404  at which the bottom end  308   b  of the associated rib  308  is fixed. 
     In the embodiment of the invention that is depicted in  FIG.  4   , the fixing zone  404  takes the form of a cavity in the transverse wall  406  in which cavity the bottom end  308   b  of the associated rib  308  is housed, but in another embodiment which has not been depicted, the transverse wall  406  may be planar and the fixing zone  404  is then the planar surface of the transverse wall  406 . In the embodiment of the invention that has been depicted in  FIGS.  3  and  4   , the fixing of the bottom end  308   b  of the rib  308  is performed using bolts or rivets  320  through bores  320   a - b  parallel to the longitudinal direction X and provided for this purpose through the bottom end  308   b  of the rib  308  and through the transverse wall  406 . 
     In the embodiment of the invention that has been depicted in  FIGS.  3  and  4   , the top end  308   a  of the rib  308  comprises a web  410  extending transversely with respect to the upper spar  302 , which is to say, perpendicular to the longitudinal direction X, and on each side of the web  410  with respect to the longitudinal midplane P, a flange  412   a - b  secured to the web  410 , and each flange  412   a - b  bears against the internal face of a lateral wall  302   b - c  of the upper spar  302  and is fixed to the lateral wall  302   b - c.    
     In the embodiment of the invention that is depicted in  FIGS.  3  and  4   , each flange  412   a - b  is fixed by means of bolts or rivets  322  through bores  322   a - b  perpendicular to the lateral wall  302   b - c  concerned and provided for that purpose in the flange  412   a - b  and the lateral wall  302   b - c  of the upper spar  302 . 
     Because of the presence of the jet engine  102  below the lower spar  304  and the pads  402 , these latter components are subjected to very high temperatures. In order to be able to withstand these temperatures, the lower spar  304  and the pads  402  need to be made from a material able to withstand these high temperatures and they are preferably made of metal. 
     Likewise, the ribs  308  are preferably made of metal in order to withstand the high temperatures in the vicinity of the bottom ends  308   b  and in order to withstand the forces passing through them. 
     Conversely, the upper spar  302  is subjected to lower temperatures and it is therefore possible to produce the upper spar  302  from a less weighty material and this is made, for example, of composite materials such as CFRP (carbon fiber reinforced polymer). 
     Such a structure enables the lightening of the engine pylon  106 . 
     Because of its structure being made of composite materials, the upper spar  302  can be given a complex shape. Such a complex shape makes it possible to create an aerodynamic exterior fairing which offers an aerodynamic exterior surface and forms the exterior fairing of the engine pylon  106  providing the connection between the nacelle of the jet engine  102  and the skin of the wing  104 , unlike in the prior art where an additional exterior fairing is needed. 
     The upper spar  302  thus acts as the primary structure, aimed at transferring load, and as the secondary structure, aimed at aerodynamically cladding the primary structure and housing the systems therein. 
     If the upper spar  302  is unable to constitute the aerodynamic exterior fairing, clips  310  are fixed to the outside of each lateral wall  302   b - c  of the upper spar  302  onto which to attach an additional aerodynamic exterior fairing (which is not depicted in the figures). 
     An assembly method enables the creation of two modules which are then fixed to one another along rows of fixings  306   b - c , allowing simple rapid assembly. 
     A first module is made up of the upper spar  302  and of the clips  310 , if present, and a second module is made up of the lower spar  304  and of the ribs  308  fixed in place by their bottom ends  308   b.    
     The two modules are then fixed together by fitting fixing means and by fixing the top end  308   a  of the ribs  308  to the upper spar  302 . 
       FIGS.  5  to  7    show various embodiments of the fixing means along the row of fixings  306   c  (the two rows of fixings  306   b - c  are identical). 
     In the embodiment of  FIG.  5   , an internal face of the free end of each lateral wall  302   b - c  of the upper spar  302  bears against an external face of the free end of a lateral wall  304   b - c  of the lower spar  304 . The internal face is the face that faces towards the inside of the engine pylon  106  and the external face is the face that faces towards the outside of the engine pylon  106 . 
     In the region where a lateral wall  302   b - c  of the upper spar  302  is superposed on a lateral wall  304   b - c  of the lower spar  304 , the lateral walls  302   b - c  and  304   b - c  have, passing through them, coaxial through-bores  501   a - b  distributed along the length of the spars  302  and  304 . 
     The fixing means  500  comprise, for each pair of coaxial through-bores  501   a - b , a shanked fastener  502  which has a shank that is inserted into the through-bores  501   a - b  and a head at each end of the shank so as to sandwich the lateral walls  302   b - c  and  304   b - c . The shanked fasteners  502  are, for example, bolts or rivets. The sandwiching is between the head of the screw and the nut in the case of a bolt, or between the head and the headed tail in the case of a rivet. 
     In the embodiment of  FIG.  6   , the free end of each lateral wall  302   b - c  of the upper spar  302  is butted against the free end of a lateral wall  304   b - c  of the lower spar  304 . 
     The free end of each lateral wall  302   b - c ,  304   b - c  has passing through it through-bores  601   a - b  that are distributed along the length of the spar  302 ,  304 . 
     The fixing means  600  comprise, for each pair of butted-together lateral walls  302   b - c ,  304   b - c , a fishplate  604  which is placed against an external face of each lateral wall  302   b - c ,  304   b - c  of the pair. The external face is the face facing towards the outside of the engine pylon  106 . 
     Each fishplate  604  has, for each through-bore  601   a - b  of the associated pair, a complementary through-bore  603   a - b  coaxial with the through-bore  601   a - b.    
     The fixing means  600  comprise, for each through-bore  601   a - b , a shanked fastener  602  which has a shank that is inserted into the through-bore  601   a - b  and the coaxial complementary through-bore  603   a - b  and a head at each end of the shank so as to sandwich the associated fishplate  604  and lateral wall  302   b - c ,  304   b - c . The shanked fasteners  602  are, for example, bolts or rivets. The sandwiching is between the head of the screw and the nut in the case of a bolt or between the head and the headed tail in the case of a rivet. 
     In the embodiment of  FIG.  7   , the free end of each lateral wall  304   b - c  of the lower spar  304  has a plurality of housings  704  distributed along the length of the lower spar  304  where each housing  704  has a contact wall  706  which is roughly (+/−10 degrees) perpendicular to the associated lateral wall  302   b - c  of the upper spar  302 , which is to say, is on the same side as and constitutes the free end of the lower spar  304 . 
     The edge face of the free end of each lateral wall  302   b - c  of the upper spar  302  is placed against the contact walls  706  of the associated housings  704 . 
     Each contact wall  706  has a through-bore  701   b  of which the axis is roughly (+/−10 degrees) parallel to the associated lateral wall  302   b - c  of the upper spar  302 . 
     For each through-bore  701   b , the associated lateral wall  302   b - c  of the upper spar  302  has a first bore  701   a  of which the axis is perpendicular to the axis of the through-bore  701   b  and a second bore  701   c  coaxial with the through-bore  701   b  and opening into the first bore  701   a.    
     The fixing means  700  comprise, for each through-bore  701   b , a sleeve nut  702   a  (also known as a tube nut or a barrel nut) housed in the first bore  701   a  and a screw  702   b  of which the shank passes successively through the through-bore  701   b , and the coaxial second bore  701   c  to screw into the sleeve nut  702   a  in the associated first bore  701   a.    
     The contact wall  706  and the lateral wall  302   b - c  of the upper spar  302  are thus sandwiched between the head of the screw  702   b  and the sleeve nut  702   a  which collaborate with one another. 
     While at least one exemplary embodiment of the present invention(s) is disclosed herein, it should be understood that modifications, substitutions and alternatives may be apparent to one of ordinary skill in the art and can be made without departing from the scope of this disclosure. This disclosure is intended to cover any adaptations or variations of the exemplary embodiment(s). In addition, in this disclosure, the terms “comprise” or “comprising” do not exclude other elements or steps, the terms “a” or “one” do not exclude a plural number, and the term “or” means either or both. Furthermore, characteristics or steps which have been described may also be used in combination with other characteristics or steps and in any order unless the disclosure or context suggests otherwise. This disclosure hereby incorporates by reference the complete disclosure of any patent or application from which it claims benefit or priority.