Abstract:
A tail-cone of an aircraft includes a skin provided with a movable fairing which, by a swing articulated mechanism, is supported on the skin in order to allow the opening/closing of the movable fairing and gain access to the inside of the tail-cone. The tail-cone includes actuators for operating the swing articulated mechanism in order to permit the automatic opening and closing of the movable fairing to be carried out.

Description:
FIELD OF THE INVENTION 
     The invention relates to a tail-cone of an aircraft that includes a movable fairing that can be opened in order to permit access to the inside of said tail-cone in which an auxiliary power unit (APU) is conventionally housed. 
     The invention has the aim of providing a movable fairing which can be opened by means of a swing articulated mechanism permitting access to the APU. Another aim of the invention is to provide actuators which will to operate the swing articulated mechanism in such a way that the opening of the fairing can be done automatically. 
     DESCRIPTION OF THE PRIOR ART 
     In the state of the art it is known that the skin of the tail-cone of an aircraft incorporates a movable fairing that can be opened in order to permit access to the inside of the tail-cone, in which the current tendency among the large majority of manufacturers is to locate an auxiliary power unit (APU) inside, which provides electrical and/or pneumatic power to the aircraft. The reason for locating it there is that the APU constitutes a possible source of fire and, as the tail-cone is a secondary structure, any possible damage or fault in the tail-cone would not imply a catastrophic failure. Therefore, in order to prevent possible fires in the primary structures of the aircraft, the APU is located in the tail-cone, furthermore being protected from the rest of the fuselage by means of a fireproof bulkhead. 
     Given that the APU requires maintenance, the skin of the tail-cone needs to incorporate a door or similar element permitting access to the APU. 
     In this regard, Spanish patent with application No. P-200602770 can be cited, which describes a movable fairing that can be opened in order to permit access to be had to the APU for carrying out its maintenance. The opening of the movable fairing is carried out by means of rotating shafts oriented in the longitudinal direction of the aircraft, in a way equivalent to how the opening of a hinged lid is carried out. 
     SUMMARY OF THE INVENTION 
     The present invention constitutes an alternative to the tail-cones of aircraft with a movable fairing that can be opened cited in the state of the art, comprising, as do the latter, a skin that includes a movable fairing that can be opened, such that its interior houses an auxiliary power unit (APU) which is supported by fixing means, and all this being done in such a way that the movable fairing is displaced from a closed position in which the skin is kept closed housing the APU, to an open position permitting access to the APU. The main novelty of the invention consists of the fact that the movable fairing comprises a lower longitudinal section of the skin of the tail-cone and is also supported by means of a swing articulated mechanism which facilitates access to the APU. 
     In one embodiment of the invention, the swing articulated mechanism comprises at least a forward rod and a rear rod, the lower ends of which are joined in an articulated way to the movable fairing, while their upper ends are joined either to the inner part of the skin, or to the fixing means of the APU, or to both, depending on the needs for achieving the correct support for the movable fairing. 
     In order to facilitate the opening and closing of the movable fairing, the invention includes at least one automatic actuator, in such a way that the opening and closing of the fairing is done automatically, considerably facilitating access to the APU. 
     The actuator can also be manual, in which case it does not provide the advantage of automatic opening, or it is also possible for the actuator to be automatic and incorporate a manual drive/actuating position in case of failure during automatic operation. 
     In either case the actuators can be pneumatic or hydraulic in order to provide a smooth opening/closing of the movable fairing. 
     In one embodiment of the invention, the actuator is arranged in such a way that it moves one of the forward or rear rods, or both simultaneously depending on the size and design of the movable fairing. 
     In the preferred embodiment of the invention the longitudinal section of the skin constituting the movable fairing is defined by the lower longitudinal half of said fairing, in such a way that when the opening and closing of the movable fairing is carried out, there remains a large open space which considerably facilitates access to the APU. 
     Moreover, in the preferred embodiment of the invention, the swing articulated mechanism consists of a pair of forward rods and a pair of rear rods, which are operated by means of two actuators that can act either on the two forward rods, or on the two rear rods, or on one forward rod and another rear rod 
     Once the movable fairing is in the closed position, and in order to prevent it from being accidentally opened, the invention includes conventional closing means which keep the movable fairing in its closed position, preventing it from opening until said conventional closing means are opened. 
     Said conventional closing means are arranged uniformly along the closing perimeter of the movable fairing with the skin and with the separation structure for the tail-cone with respect to the rest of the fuselage. 
     Furthermore, when the movable fairing is in the open position, there exists the risk of it being subjected to lateral loads owing to gusts of wind, for which the invention comprises means of blocking the movable fairing in its open position. These means consist of at least one rod, one end of which is fixed in an articulated way to the inner part of the fairing, with its other end being fixed to the inner part of the upper skin or onto the fixing means of the APU. 
     In the preferred embodiment of the invention, the means of blocking the movable fairing in its open position are defined by two rods arranged longitudinally and fixed in an articulated way to the inside lower part of the movable fairing, in such a way that when the movable fairing is opened, the rods can be extended and their ends can be fixed to the fixing means of the APU or to the inside of the upper skin, all this in such a way that the rods form a “V” shaped configuration which blocks the movable fairing in its open position so that it absorbs the lateral loads that might be exerted on the movable fairing due to possible gusts of wind. 
     The fixing means of the APU present an arrangement that is supported either on the separation structure between the tail-cone and the rest of the fuselage, or on the inner structure of the skin, or on both, which is possible due to the arrangement presented by the movable fairing. 
     It can also be pointed out that once the fairing is closed, with the conventional closing means being closed, hence securing this position, the invention comprises means of sealing the attachment zone of the moveable fairing with the skin and with the rest of the fuselage in said closed position, therefore, in order to gain access to the inside of the tail-cone, it is first of all necessary to remove the sealing means and then, after carrying out the opening of the conventional closing means , to act on the actuators in order to carry out the opening of the movable fairing as was described. 
     Below, in order to facilitate a better understanding of this descriptive specification and forming an integral part thereof, a series of figures is attached in which the object of the invention has been represented by way of illustration and non-limiting. 
    
    
     
       BRIEF DESCRIPTION OF THE FIGURES 
         FIG. 1 . shows a side elevation view of the tail-cone in which the movable fairing has been drawn transparently. 
         FIG. 2 . shows a perspective view of the above figure in which the movable fairing has been represented half-open. 
         FIG. 3 . shows a detail of the fixing of the actuator to one of the rods of the swing articulated mechanism and to the inner part of the upper part of the movable fairing. 
         FIG. 4 . shows another detail of the fixing of the actuator to the arm in order to allow it to operate, in accordance with the previous figure. 
         FIG. 5 . shows a perspective view of the movable fairing in its open position, in which the rods have also been represented in their blocked position. 
         FIG. 6 . shows a perspective view of the movable fairing in its closed. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Given below is a description of the invention based on the figures commented on above. 
     The tail-cone of the invention comprises a skin that is endowed with a movable fairing  1  that can be opened, inside which is housed an auxiliary power unit (APU)  2 , which is supported by fixing means  3  defined by a support structure consisting of a series of longitudinal and transverse elements, which are not described in further detail since they are not the object of the invention. In the example of the embodiment these longitudinal and transverse elements are fixed to the separation structure  4  between the tail-cone and the rest of the fuselage. 
     As is known in the state of the art, and in order to facilitate an understanding of the invention it can be mentioned that the APU  2  is provided with an air intake  5  and an exhaust pipe  6 . 
     The movable fairing  1  is arranged on the skin by means of a swing articulated mechanism consisting of four rods  7 , two forward and two rear, whose ends are fixed in an articulated way  11  to the inner part of the upper half of the skin. Likewise, the lower ends of the rods  7  are fixed in an articulated way to the inner part of the movable fairing  1 , and more specifically to some frames  8  that are integral with the inside of said movable fairing  1 . 
     In order to facilitate the opening and closing of the movable fairing  1 , the invention includes two actuators  9  for operating the rods  7 . These actuators  9  are of a hydraulic or pneumatic nature and, in a preferred embodiment, they are governed by a control circuit, the operation of which is permits the opening and closing of the movable fairing  1  to be carried out automatically. 
     For this purpose, said actuators  9  are fixed by one of their ends to one of the rods  7  by means of a rotating joint  10 , and by their other end to a rib  8   b  provided on the inner side of the upper skin, this joint being effected in a rotating point  12 . Moreover, the rod  7  is fixed to a rib  8   a  supported on the inside of the upper skin, by means of a rotating point  11 . 
     Once the opening of the movable fairing  1  has been carried out, it needs to be kept in a stable open position, for which purpose blocking means  13  are included for keeping the movable fairing  1  in its open position. These blocking means consist of two rods  13  which are articulated in separate points  14  provided in one of the frames  8 , such that in the closed position of the movable fairing  1  they are arranged longitudinally along the inside of said movable fairing  1 , and more specifically resting on the frames  8 . 
     Once the opening of the movable fairing  1  is carried out by operating the actuators  7 , until the movable fairing  1  is situated in its open position ( FIG. 5 ), the rods  13  open are extended to a substantially vertical position, in such a way that they are fixed to the inside of the upper half of the skin, which secures the positioning of the open position of the movable fairing  1  with regard to any possible lateral wind gusts that might occur. 
     Finally, it can be pointed out that the invention includes conventional closing means  15  which are uniformly distributed along the closing perimeter of the articulated movable fairing  1  with the closure of the skin and with the separation structure  4 between the tail-cone and the rest of the fuselage, all this in order to maintain a secure closed position for the movable fairing  1  in such a way that it is prevented from being accidentally opened. 
     In addition, sealing means are included for the joining zone between the movable fairing  1  and the skin and the rest of the fuselage in its closed position, in such a way that, in order to carry out the opening of the movable fairing  1  it is first of all necessary to remove the seal and then carry out the opening of the conventional closing means  15 , at which point the actuators  9  are able to be operated in order to effect the opening in the manner already mentioned. 
     In order to carry out the closure of the movable fairing  1 , the reverse procedure is followed. 
     The sealing means are defined in line with the periodicity with which the APU needs to be accessed, and as a consequence will be any of those provided for in the state of the art in such a way that permits them to be replaced quickly and simply in accordance with that periodicity.