Patent Publication Number: US-2022219829-A1

Title: Forward secondary structure for a mounting pylon of an aircraft

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims priority to French patent application number 2100298 filed on Jan. 13, 2021, the entire disclosure of which is incorporated by reference herein. 
     TECHNICAL FIELD 
     The disclosure herein relates to a forward secondary structure for a mounting pylon of an aircraft. 
     BACKGROUND 
     As is conventional, and with reference to  FIG. 1 , each wing A of an aircraft supports at least one mounting pylon  1  which in turn supports a turbomachine  2  comprising a nacelle  3  that surrounds an engine (not shown). 
     The mounting pylon  1  comprises a primary structure (not shown) and secondary structures that are affixed to the primary structure and hold systems (for example hydraulic or electrical systems) while supporting the various aerodynamic fairings of the mounting pylon. 
     Secondary structures include a forward secondary structure  4  located at the front of the primary structure of the mounting pylon  1 . When the mounting pylon  1  is installed beneath the wing A and supports the turbomachine  2 , a forward aerodynamic fairing C of the forward secondary structure  4  provides an aerodynamic profile between the nacelle  3  and the front of the wing A. Patent application FR3088906 describes a forward secondary structure with a forward aerodynamic fairing comprising a starboard leaf and a port leaf arranged on either side of a longitudinal median plane of the forward secondary structure. Each leaf is articulated between a closed position in which it is in aerodynamic continuity with the fixed elements of the forward aerodynamic fairing, and an open position in which it frees up an opening allowing access to the systems contained in the pylon. Each leaf passes from the closed position to the open position by moving upwards and outwards from the forward secondary structure. The direction of opening of a first leaf is counter to the direction of opening of a second leaf, such that when the two leaves are both in the open position, technicians have a large opening for access to the systems. 
     One aim of the disclosure herein is an alternative to the abovementioned solution. 
     To that end, the disclosure herein relates to a forward secondary structure for a mounting pylon for a turbomachine, the forward secondary structure extending from upstream to downstream along a longitudinal axis, the forward secondary structure comprising a chassis that is clad with an aerodynamic fairing, and two adjacent cowls, each having an upstream portion, where each of the cowls extends lengthwise along the longitudinal direction and comprises in its upstream portion a system for articulating the cowl to the chassis, by which system the cowl can pivot with respect to the chassis about an axis of rotation that is normal to the longitudinal axis, between a closed position in which all of an inner face of the cowl is pressed against the chassis and an open position in which the cowl frees up an opening in the forward secondary structure. 
     The disclosure herein also relates to a pylon for mounting a turbomachine beneath the wing of an aircraft, the mounting pylon comprising a primary structure in the form of a box extending from front to rear along a longitudinal axis and comprising an upper face at the top and a lower face at the bottom, characterized in that a forward secondary structure according to the disclosure herein is attached to the front of the primary structure. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The abovementioned features of the disclosure herein, as well as others, will appear more clearly upon reading the following description of an example embodiment, the description being provided with reference to the appended drawings, in which: 
         FIG. 1 , which has already been described, is a front perspective view of a prior art mounting pylon equipped with its various aerodynamic fairings and mounted beneath a wing of an aircraft; 
         FIG. 2  is a perspective view of a mounting pylon comprising an unfaired forward secondary structure; 
         FIG. 3  is a view similar to  FIG. 2 , showing a mounting pylon comprising a forward secondary structure that is faired by a forward aerodynamic fairing comprising two cowls that are both shown in the closed position, according to one embodiment of the disclosure herein; 
         FIG. 4  is a perspective view of the forward secondary structure shown in  FIG. 3 , in which the two cowls are both in the open position; and 
         FIG. 5  is a perspective view of the region indicated by the arrow F depicted in  FIG. 4 , showing in detail the articulation of the two cowls to the chassis of the forward secondary structure. 
     
    
    
     DETAILED DESCRIPTION 
     With reference to  FIG. 2 , a mounting pylon  10  for a turbomachine conventionally comprises a primary structure  20  that takes the form of a rigid box which extends lengthwise from forward (upstream) to rear (downstream) along a longitudinal axis X. The longitudinal median plane V is that plane which is parallel to the longitudinal axis X, is orthogonal to the ground and divides the mounting pylon  10  into two parts, left and right. 
     The box  20  comprises an upper face Fs at the top, and a lower face Fi at the bottom. When the mounting pylon  10  is attached beneath a wing of an aircraft, the upper face Fs faces the wing while the lower face Fi faces the ground. 
     As is known, a forward secondary structure  30  forms the front of the mounting pylon  10 , and is attached to the front of the primary structure  20  in a cantilever arrangement with respect to the latter. The forward secondary structure  30 , which extends from front to rear along the longitudinal axis X, serves to segregate and hold systems S passing through the mounting pylon. 
     The forward secondary structure  30  is constructed in the form of a chassis  31  made up of an assembly of stringers  32  and ribs  33 - 38 , each stringer  32  extending along the longitudinal axis X of the mounting pylon  10  and each rib extending perpendicular to the stringers  32 , that is to say in a plane T that is transverse to the longitudinal axis X. The ribs  33 - 38  have a shape that is curved and open towards the bottom. 
     The ribs  33 - 38 , together with the stringers  32 , form a cradle B. 
       FIGS. 3 through 5  show a forward secondary structure  40  and its forward aerodynamic fairing  40 . According to the disclosure herein, this forward fairing comprises two adjacent cowls  41 ,  42  that extend from upstream to downstream along the longitudinal axis X and that are mounted articulated to the chassis  31 . 
     Each of the cowls  41 ,  42  is mounted in articulated fashion with an axis of rotation R 1 , R 2  that is normal to the longitudinal axis X at its upstream portion to the chassis  31  via an articulation system  43 ,  44  (particularly visible in  FIG. 5 ) that allows each of the cowls  41 ,  42  to pivot with respect to the chassis between a closed position ( FIG. 4 ) in which all of one face  41   a ,  42   a  of the cowl  41 ,  42 , referred to as the inner face, is pressed against the chassis  31  and partially covers the cradle B, and an open position ( FIG. 3 ) in which the cowl  41 ,  42  frees up an opening in the forward secondary structure  30  in order to allow access to the interior of the forward secondary structure  30 . 
     Each cowl  41 ,  42  further comprises a system  45  for locking the cowls, in order to lock these in place in the closed position on the chassis  31 . 
     From a viewpoint located to the rear of the mounting pylon and oriented towards the front of the pylon, the cowl  41  located on the left of the longitudinal median plane is referred to as the left-hand cowl in the rest of the description, and the cowl  42  located on the right of the longitudinal median plane is referred to as the right-hand cowl. 
     Each of the left and right cowls  41 ,  42  comprises four edges in opposite pairs. More particularly, each of the left and right cowls has a forward edge  41   f ,  42   f  which is arranged at the forward end of the cowl  41 ,  42 , with respect to the longitudinal axis X, and which extends in a plane normal to the longitudinal axis X. Each of the left and right cowls  41 ,  42  has a rear edge  41   r ,  42   r  which is arranged at the rear of the cowl  41 ,  42  with respect to the longitudinal axis X. 
     Each of the left and right cowls  41 ,  42  also has two lateral edges that are generally parallel to the longitudinal axis X, with an inner lateral edge  41   li ,  42   li  and an outer lateral edge  41   le ,  42   le . The two cowls  41 ,  42  are contiguous, with their inner lateral edges  41   li ,  42   li  also contiguous when the two cowls  41 ,  42  are both in the closed position. 
     In identical fashion for each of the left and right cowls  41 ,  42 , the articulation system  43  associated with the left cowl  41 , or respectively the articulation system  44  associated with the right cowl  42 , is arranged at the forward edge  41   f  of the left cowl, respectively at the forward edge  42   f  of the right cowl, and comprises two hinges  43   a - b ,  44   a - b , with one hinge  43   a ,  44   a  arranged on the side of the inner edge  41   li ,  42   li  of the cowl and one hinge  43   b ,  44   b  arranged on the side of the outer edge  41   le ,  42   le  of the cowl. Each hinge  43   a - b ,  44   a - b  comprises a gooseneck of which a first end is attached to the inner face  41   a ,  42   a  of the cowl and a second end is connected to a fitting attached to a rib  33  of the chassis by a pin. The pins of the two hinges  43   a - b ,  44   a - b  of an articulation system  43 ,  44 , which are associated with a cowl  41 ,  42 , are collinear and form the axis of rotation R 1 , R 2  of the articulation system. 
     In the case of the cradle B having, over its entire length, a cross section that is in the shape of an arc of a circle which is open towards the bottom, the two articulation axes R 1  and R 2  of the two articulation systems  43 ,  44  are collinear. 
     The two cowls  41 ,  42  are mounted articulated to a same rib  33  of the chassis and the forward edge  41   f  of the left cowl  41  extends the forward edge  42   f  of the right cowl  42  (and vice versa) when the two cowls  41 ,  42  are both in the closed position. 
     The figures show the two cowls as being symmetrical with one another with the longitudinal median plane V as the plane of symmetry. This embodiment is the simplest for the manufacture and assembly of the cowls. In other variants (not shown), the cowls  41 ,  42  are not symmetrical. 
     When moving between the closed position and the open position, the left cowl  41 , or respectively the right cowl  42 , moves away from the chassis  31  in an upward movement. Conversely, when moving between the open position and the closed position, the left cowl  41 , or respectively the right cowl  42 , moves towards the chassis  31  in a downward movement. 
     When the two cowls  41 ,  42  are both in the closed position, the inner lateral edge  41   li  of the right cowl  41  is parallel to the inner lateral edge  42   li  of the right cowl  42 . 
     The system for locking the cowls  45  comprises, for each cowl  41 ,  42 , a plurality of through-orifices  45   a  (shown in  FIG. 4 ) that are arranged both on the rear edge  41   r ,  42   r  and on the outer lateral edge  41   le ,  42   le  in order to permit the insertion of removable fasteners (not shown) for fastening the cowl  41 ,  42  to the chassis. The removable fasteners are for example of the screw or lock type. 
     Moreover, the cowl locking system  45  comprises securing structure  45   b  for securing the two cowls  41 ,  42 . The securing structure  45   b  comprises:
         at least one strip, and preferably a row of strips  45   c , as illustrated in  FIG. 5 , that are riveted along the inner edge  41   li  of a first cowl, in this case the left cowl  41  in the example provided in the figures. Each strip  45   c  comprises a free portion that extends out of the first cowl  41  to which the strip is attached, towards the second cowl  42 , in this case the right cowl in the example provided in the figures, and which forms a planar surface on which the second, right cowl  42  rests when the latter is in the closed position;   an anchor  45   d , of the rivet nut type, arranged on the free portion of the strips  45   c . The second cowl  42  is provided with through-orifices (not shown) that are arranged along its inner lateral edge  42   li  and each orifice opens onto a rivet nut  45   d  when the second cowl  42  is in the closed position.       

     When the two cowls  41 ,  42  are both in the closed position, the inner lateral edge  42   li  of the second cowl  42  rests on the free portion of the strips  45   c , and the two cowls  41 ,  42  can be secured to each other by driving screws into the anchor  45   d  through the orifices of the right cowl  42 . 
     Moreover, the strips  45   c  also serve to seal the join between the two cowls  41 ,  42  when the latter are both in the closed position. 
     When an operator wishes to have access to the systems S arranged beneath the cowls  41 ,  42 , they must first separate the two cowls  41 ,  42  by unscrewing the screws from the anchor  45   d , then move first the second cowl  42  to its open position, and thereafter the first cowl  41  to its open position. During refitting, these operations must be carried out in reverse order. 
     The length of each cowl  41 ,  42  is limited only by the necessity of dimensioning the articulation system  43 ,  44  associated with the cowl  41 ,  42  with limited mass and bulk, allowing it to be integrated into the forward secondary structure  30  despite there being little available space once the systems S have been installed. 
     Owing to the manner in which they are attached to the chassis  31 , the cowls  41 ,  42  may extend over a great length and thus cover a large surface and hence take the place of a multitude of panels P that would conventionally be used to form an aerodynamic fairing. This makes it possible to reduce the number of fasteners and hence the time required to gain access to the systems positioned beneath the forward aerodynamic fairing  40 . Furthermore, replacing a multitude of panels with only two cowls  41 ,  42  serves to improve the aerodynamics of the forward aerodynamic fairing  40  of the forward secondary structure  30  by eliminating surface gaps which exist between the panels. 
     In the embodiment illustrated in  FIGS. 3 through 5 , the cowls  41 ,  42  do not cover the entire length of the chassis  31  along the longitudinal axis X. According to this embodiment, the forward aerodynamic fairing  40  of the forward secondary structure  30  comprises, from front to rear, a band  50  which covers the front of the chassis and which is attached to the latter by screws (not shown), then the movable cowls according to the disclosure herein (the two cowls being of identical shape and length, and each cowl  41 ,  42  extends over a majority of the length of the forward secondary structure  30 , covering part of the cradle B), then, at the rear of the forward secondary structure  30 , panels P attached to the chassis  31  by screws in order to cover the rest of the chassis. 
     Preferably, and as illustrated in  FIG. 5 , each of the left and right cowls  41 ,  42  comprises an actuator J, of the pneumatic or gas cylinder type, for helping to open the articulated cowl  41 ,  42  and to hold it in the open position. The actuator J is for example a gas cylinder. Each actuator J associated with a cowl comprises a first end attached to the chassis  31 , more specifically to the rib  34  following the rib  33  to which the cowls  41 ,  42  are articulated, and a second end attached to the inner face  41   a ,  42   a  of the cowl at a point remote from the articulation system  43 ,  44  associated with the cowl  41 ,  42 . 
     A system of the stay type (not shown) may also be arranged to hold the cowls  41 ,  42  in the open position. For each cowl  41 ,  42 , the stay consists of or comprises a rod whose first end is pivotably attached to the rib  33  to which the cowls  41 ,  42  are articulated, and whose second end can be inserted into an anchor point arranged on the inner face  41   a ,  42   a  of the cowl. The anchor point is positioned in such a way that the second end of the rod can be inserted therein when the cowl is in the open position. 
     The disclosure herein as described above can use a horseshoe-shaped cradle B that is open towards the bottom, changing the orientation of the axis of rotation R 1  of the articulation system  43  of the left cowl  41  with respect to the orientation of the axis of rotation R 2  of the articulation system  44  of the right cowl  42 . In the example shown in  FIG. 5 , the chassis  31  has a particular shape since the shape of the ribs  33 - 38  in the transverse plane T changes from front to rear in the longitudinal direction X of the mounting pylon  10 . Thus, from front to rear in the longitudinal direction X of the mounting pylon, the ribs (ribs  33 ,  34 ) have first of all in the transverse plane a shape that is slightly curved and open towards the bottom, then (rib  35 ) an omega shape that is open towards the bottom, then (ribs  36 - 38 ) a horseshoe shape that is open towards the bottom. 
     In order to use this particular shape of the cradle B, the axis of rotation R 1  of the articulation system  43  of the left cowl  41  and the axis of rotation R 2  of the articulation system  44  of the right cowl  42  are not mutually collinear but instead are coplanar and intersect with an obtuse angle between them, the apex of this angle being oriented upwards. The axis of rotation R 1  of the articulation system  43  of the left cowl  41  and the axis of rotation R 2  of the articulation system  44  of the right cowl  42  remain normal to the longitudinal axis X. 
     Thus, when moving between the closed position and the open position, the left cowl  41 , or respectively the right cowl  42 , moves away from the chassis  31  with a movement that is oriented both laterally outwards from the chassis  31  and upwards from the chassis  31 . Conversely, when moving between the open position and the closed position, the left cowl  41 , or respectively the right cowl  42 , moves towards the chassis  31  with a movement that is oriented both laterally towards the interior of the chassis  31  and towards the bottom of the chassis  31 . 
     This particular arrangement of the axes of rotation R 1 , R 2  means that when the two cowls  41 ,  42  are both in the closed position, the inner lateral edge  41   li  of the left cowl  41  is parallel to the inner lateral edge  42   li  of the right cowl  42 . By contrast, when the two cowls  41 ,  42  are both in the open position, the inner lateral edge  41   li  of the left cowl  41  and the inner lateral edge  42   li  of the right cowl  42  are no longer parallel but rather form between them an angle whose apex is oriented towards the front of the mounting pylon  10 . 
     While at least one example embodiment of the 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 example embodiment(s). In addition, in this disclosure, the terms “comprise” or “comprising” do not exclude other elements or steps, the terms “a”, “an” 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.