Abstract:
The disclosure relates to a device for testing means of detecting the loading of the secondary path of a flight control actuator of the type including a primary path and a secondary path able to take up the effort of the primary path in the event of a breakdown of the latter, wherein a tool is able to press against at least one zone of at least one element of the secondary path, as well as a lever arm which by tilting allows the tool to press against the zone so that it exerts a traction and/or compression force on the secondary path, the lever arm being mounted pivotingly on a support able to be fastened on a structure that is mechanically independent of the secondary path.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims the benefit and priority of French Patent Application Serial No. 0958738, filed on Dec. 8, 2009, which is incorporated by reference herein. 
       BACKGROUND 
       [0002]    This invention relates to a device for testing the detection of load on a flight control actuator. It also relates to a method for testing. In particular, but not in a limiting manner, it relates to testing the detection of the take-up of effort by a secondary path of a flight control actuator of aircraft and in particular advantageously has application in the case of an actuator of the THSA type (Trimmable Horizontal Stabilizer Actuator). 
         [0003]    It is known conventionally, that such actuators comprise two mechanical paths, one primary and the other secondary, with the latter intended to take up the effort when the primary path has broken down. When operating on the primary path, the loads transit through a hollow ball or roller screw. This characteristic makes it possible to house therein a safety rod (so-called “fail safe” bar), grooved at its ends and connected with an allowance to the screw. This structure ensures the continuity of the transmission of the efforts and of the rotation of the whole (avoiding an axial separation of the elements of the screw, in the event of a rupture of the screw itself). The screw is terminated at one of its ends with a fastening piece through which it is connected to the aircraft (primary top fastener). In the event of a breakdown of the latter, the effort is recovered by the safety rod of which the end is of male shape (for example a sphere) arranged in a female shape of a fastening piece of the secondary path (secondary top fastener). This secondary top fastener is itself connected to the aircraft by means of a fastening piece of the aircraft different from that used to support the primary path. 
         [0004]    In normal operation, when the primary path carries the effort, an allowance exists between the male shape which terminates the safety rod and the female shape of the fastening piece of the secondary path, in such a way that the secondary fastening piece of the airplane does not support any effort other than the weight of the secondary female fastening piece of the THSA. During a breakdown of the primary path, the male shape which terminates the screw comes into contact with the female shape of the fastening piece of the secondary path which results in the take-up of effort by the secondary fastening frame of the airplane. 
         [0005]    There are diverse devices for detecting efforts integrated into the flight control actuator making it possible to detect the take-up of effort of the secondary path. An example of a solution in these terms has for example been disclosed by the applicant in application EP 08102826.8. 
         [0006]    Nevertheless, to date there is no simple solution making it possible to test on the ground the operation of such devices for detecting the take-up of effort by a secondary path of a flight control actuator. That is why it is desired to be able to propose solutions making it possible to test such devices, in particular during the periodical inspection of the airplane on the ground. It is also desirable to have testing solutions that can be easily set up on an airplane on the ground. 
       SUMMARY 
       [0007]    The invention proposes a device for testing means of detecting the loading of the secondary path of a flight control actuator of the type comprising a primary path and a secondary path able to take up the effort of the primary path in the event of a breakdown of the latter, characterised in that it comprises a tool able to press against at least one zone of at least one element of the secondary path, as well as a lever arm which by tilting allows the tool to press against said zone so that it exerts a traction and/or compression force on the secondary path, said lever arm being mounted pivotingly on a support able to be fastened on a structure that is mechanically independent of the secondary path. The invention further includes a method for testing. 
         [0008]    An advantage of the invention is to propose a simple solution making it possible to test on the ground the operation of a device for detecting the take-up of effort by a secondary path of a flight control actuator, for reasons of maintenance of the airplane in particular. Another advantage of the invention is to propose a solution which is adapted directly on the airplane, in order to facilitate the verification and maintenance operations. Yet another advantage of the invention is to propose a test solution which is adapted directly on the airplane simply and with little invasion. Yet another advantage of the invention is to be able to propose a testing solution which results in the least malfunctions possible in the case where the test procedure is conducted with errors and/or forgotten items, and this in order to guarantee maximum safety. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0009]    Other characteristics and advantages of the invention shall appear in the description which follows, which is purely for the purposes of illustration and in no way limiting, and must be examined with regards to the annexed drawings wherein: 
           [0010]      FIG. 1  is a diagrammatical representation showing the principle of a flight control actuator; 
           [0011]      FIGS. 2   a  to  2   c  are diagrammatical representations of a side view and as a cross-section showing the fastening of the top fastener of the secondary path; 
           [0012]      FIGS. 3   a  and  3   b  show an example of the embodiment of means for detecting; 
           [0013]      FIG. 4  is a cross-section of a screw making it possible to fasten the top fastener of the secondary path; 
           [0014]      FIGS. 5 and 6  are representations in perspective of the device for testing the detection of the take-up of effort by a secondary path of a flight control actuator, set up on an aircraft; 
           [0015]      FIG. 7  is a lateral view of the device of  FIGS. 5 and 6 ; and 
           [0016]      FIGS. 8 and 9  are representations of the device of  FIGS. 5 ,  6  and  7  respectively during a take-up of effort in compression and during a take-up of effort in traction. 
       
    
    
     DETAILED DESCRIPTION 
     General Structure of the Actuator 
       [0017]      FIG. 1  diagrammatically shows a flight control actuator  1  with a primary path and a secondary path. This actuator  1  is for example a cylinder of the THSA type, to control a trimmable horizontal stabiliser  2  of the aircraft. It comprises a primary path which comprises a hollow screw  3  connected to an end, by a cardan joint system  4 , to the structure  81  of the airplane. The primary path further comprises a nut  5 , which cooperates with the screw  3  by being mounted on the latter and which is connected to the stabiliser  2  to be controlled, for example by another cardan joint system  6 . 
         [0018]    A safety rod  9  extends inside the hollow screw  3 . This rod  9  is terminated by a spherical head  7  placed with allowance inside a female spherical shape  10  of a fastening piece  8  of the secondary path, this fastening piece  8  being itself fastened to a structure S 2  of the airplane. This actuator is for example controlled by a hydraulic or electric motor M, which drives the screw  3  in rotation and displaces the nut  5  in translation, the latter being to this effect locked in rotation. The displacement in translation of the nut  5  thus makes it possible to control the tilting that is to be given to the horizontal variable stabiliser  2 . 
         [0019]      FIGS. 2   a ,  2   b  and  2   c  show the fastening of the fastening piece  8  of the secondary path on an upper fastening frame  11  of the structure S 2  of the airplane. As can be seen in these figures, the piece  8  is a yoke joint which comprises two frames between which the frame  11  is received. Two parallel fastening screws  12  extend through the frames of the piece  8  and the piece  11 , with the whole being fastened via clamping between heads  12   a  which terminate the fixation screws  12  at one end and nuts  13  of which the threading cooperates with that of the fastening screws  12  at their other ends. 
         [0020]    In this embodiment, the female shape  10  is made by a piece that is separate from the fastening piece  8 , this fastener piece  8  being placed on the piece which constitutes said female shape  10 . Top fastener of the secondary path designates the assembly consisting in the pieces  8 ,  10 ,  11  and  12 . 
       Detection of the Loading 
       [0021]    Means  20  for detecting efforts are arranged in such a way as to be able to detect the loading of the top fastener of the secondary path. Means for detecting, able to detect an effort are arranged on at least one of the screws  12 , or on at least one of the two frames of the piece  8 , or on rings interposed between the screw  12  and the frames and/or the nut  13 . More generally, these means for detecting can be arranged on any piece participating in the top fastener of the secondary path. 
         [0022]    Several solutions of means for detecting of this type have in particular been proposed by the applicant, as for example in application EP 08102826.8. These solutions are for example with stress gauges and punches, or encore with piezoelectric blades intended to excite the screw  12  around its resonance frequency or frequencies, or with a pressure sensor ring, for example of the silicon bridge type. 
         [0023]      FIGS. 3   a  and  3   b  show an example with strain gauge blades wherein one of the screws  12  has, perpendicular to one of the frames of the fastening piece, hollow grooves  14  whereon extend flexible strain gauge blades  15 . The strain gauge blades  15  are for example distributed at 120 degrees from each other. Punches  16  protruding on the frame come to press against the strain gauge blades and deform them when the pieces of the secondary path are loaded, either in traction, or in compression. These means for detecting effort  20  are for example connected to the computer of the aircraft, which processes the measurements taken by said means in order to deduce a loading of the secondary path and trigger where applicable the corresponding alarms. 
         [0024]      FIG. 4  shows another example wherein a spring box  23  is interposed advantageously between the nut  13  associated to the fixation screw  12  and the frame of the piece  8  that it comes to clamp. This spring box  23  makes it possible to distribute the clamping effort and makes the loading of the gauges independent of the torque clamping effort applied to the screw during assembly. False detections due to the assembly conditions are as such avoided. 
       Device for Testing 
       [0025]    The device for testing shown in  FIGS. 5 to 7  includes a lever arm  30  mounted pivotingly on a support  31 . At its end opposite its grasping portion, the piece forming a lever arm  30  is terminated by a stop  32  intended to cooperate with a complementary U-shaped element  36 , belonging to a tool  33 , said stop  32  coming to press against the inside flanks of the U-shaped element wherein it is received when the lever arm is tilted in one direction or the other. 
         [0026]    The support  31  can be an added vice, for example screwed, on a mechanically uncoupled structure in relation to the secondary path, here on the cardan joint system  4  of the primary path. Other embodiments can of course be considered. The support  31  could in particular press against a piece of the primary path or on the structure of the airplane itself. 
         [0027]    The tool  33  clamps at least one element of the top fastener of the secondary path in such a way that it makes it possible to exert on said top fastener, by tilting of the lever arm  30  and transmission of a load by pressing against the stop  32  on the inside flanks of the U-shaped element  36 , either a traction load, or a compression load, or even, as in the case which is provided as an example here, a traction load or a compression load according to the direction of tipping of the lever arm  30 . 
         [0028]    This clamping tool  33  is here carried out by the assembly of two front and rear plates  34 , by means of two clamping screws  35   a  and  35   b , which are positioned in a reduced space between an edge of the piece  8  and an edge that has, perpendicular to this edge, the piece that forms the female shape  10 . In this way, there is a tool  33  which clamps the piece  8  and is able to press against either the edge of the piece  8  or against the edge of the piece  10 , in such a way that a tipping movement of the lever arm  30  generates, according to the direction of this tipping movement, a traction or a compression on the secondary path. 
         [0029]    Other configurations may be considered. For example, the clamping tool  33  may press against only the top portion of the piece  8  and allow only to exert a compression load. 
         [0030]    The tool  33  is able to press against at least one zone of at least one element of the secondary path. Advantageously, the tool  33 , comprising in particular the front and rear plates  34  connected by the clamping screws  35   a,    35   b,  is able to clamp around a zone of an element of the top fastener of the secondary path, as shown for example in  FIG. 7 . 
       Examples of Tests of Loading 
       [0031]      FIGS. 8 and 9  show a loading of the secondary path by the device for testing. Where applicable, in the structures using a spring box  23 , the latter is loosened beforehand in order to prevent mechanical friction and allow for the resetting of the means for detecting effort on the secondary path. In the case of  FIG. 8 , the secondary path is solicited in compression. 
         [0032]    The pivoting downwards of the lever arm  30  around its pivoting axis, tips the stop  32  pressing against the top inside flank of the U-shaped element  36 . The pressing force is transmitted to the fastening piece  8 , belonging to the top fastener of the secondary path, by the intermediary of the clamping tool  33 .  FIG. 9  shows an effort in the opposite direction. 
         [0033]    During a loading by means of the device for testing which has just been described, it is verified that the means  20  for detecting effort on the secondary path did indeed detect the effort applied. This inspection can be carried out in several ways, by using or not using specifically-dedicated electronic means. 
         [0034]    A first possibility is to position an operator in the cockpit of the aircraft, whose role is to check than an alarm, which is triggered when the means  20  for detecting have detected a loading of the secondary path, has indeed been triggered. Another possibility is to use a detector that is connected to a computer of the airplane in communication with the means  20  of detecting. Once the tests in traction and/or compression are complete, the device for testing is removed from the aircraft by unscrewing the clamping screws  35   a,    35   b  and by removing the clamping vice  31 . At the end of the test, the spring boxes  23  and the nuts  13  are put back in place.