Lower attachment system for a trimmable horizontal stabiliser actuator

Abstract

A lower attachment system for a trimmable horizontal stabiliser actuator comprising: a ballnut for being disposed on a screwshaft of the actuator and forming a part of a primary load path of the lower attachment system; a trunnion connected to the ballnut and forming a part of the primary load path of the lower attachment system; a failsafe plate disposed about the trunnion and forming a part of a secondary load path; a secondary connection connected to the failsafe plate and forming a part of the secondary load path; a sheet plate attached to a first mounting point on the secondary connection and a second mounting point on the ballnut; and an adjustment mechanism provided with the sheet plate for adjusting the size or position of the sheet plate to adapt it to fit a distance between the first and second mounting points.

Claims

1. A lower attachment system for a trimmable horizontal stabiliser actuator comprising: a ballnut for being disposed on a screwshaft of the actuator and forming a part of a primary load path of the lower attachment system; a trunnion connected to the ballnut and forming a part of the primary load path of the lower attachment system; a failsafe plate disposed about the trunnion and forming a part of a secondary load path; a secondary connection connected to the failsafe plate and forming a part of the secondary load path; a sheet plate attached to a first mounting point on the secondary connection and a second mounting point on the ballnut; and an adjustment mechanism provided with the sheet plate for adjusting the size of the sheet plate to adapt it to fit a distance between the first and second mounting points.

2. A lower attachment system as claimed in claim 1, wherein the adjustment mechanism comprises: a coupling portion for coupling to a sheet portion of the sheet plate; and a screw mounted to the ballnut at the second mounting point and arranged to adjust the position of the coupling portion to adjust the size or position of the sheet plate.

3. A lower attachment system as claimed in claim 1, wherein the adjustment mechanism comprises: a coupling portion for coupling to a sheet portion of the sheet plate; and a screw mounted to the secondary connection at the first mounting point and arranged to adjust the position of the coupling portion to adjust the size or position of the sheet plate.

4. A lower attachment system as claimed in claim 1, wherein the adjustment mechanism comprises a locking mechanism for preventing changes to the size or position of the sheet plate after adjustment of the sheet plate to fit between the first and second mounting points.

5. A lower attachment system as claimed in claim 1, wherein the sheet plate is arranged to break in case of a failure of the primary load path.

6. A lower attachment system as claimed in claim 1, comprising a fuse pin coupling the sheet plate and arranged to break in case of a failure of the primary load path.

7. A lower attachment system as claimed in claim 1, wherein a part of the secondary load path is and arranged to bear against the secondary connection in case of a failure of the primary load path.

8. A trimmable horizontal stabiliser actuator comprising a lower attachment system as claimed in claim 1.

9. A method of installing a sheet plate of a lower attachment system for a trimmable horizontal stabiliser actuator as claimed in claim 1, the method comprising: coupling the sheet plate to the ballnut at the second mounting point and/or to the secondary connection at the first mounting point; and adjusting the adjustment mechanism to adjust the size or position of the sheet plate to adapt it to fit the distance between the first and second mounting points.

10. A method as claimed in claim 9, further comprising locking the adjustment mechanism to prevent further adjustment of the sheet plate.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) An exemplary embodiment of the invention will now be described by way of example only and with reference to the accompanying drawings in which:

(2) FIG. 1 shows a trimmable horizontal stabiliser actuator arranged to provide control of a flight control surface;

(3) FIG. 2 shows a schematic of primary and secondary load paths;

(4) FIG. 3A shows a primary load path through a THSA;

(5) FIG. 3B shows a secondary load path through the THSA of FIG. 3A;

(6) FIG. 4 shows a perspective view of a lower attachment system for a THSA;

(7) FIG. 5 shows a profile view of the lower attachment system of FIG. 4;

(8) FIG. 6 shows another profile view of the lower attachment system of FIG. 4;

(9) FIG. 7 shows a cross section of the line A-A of FIG. 6;

(10) FIG. 8 shows a cross section of the line B-B of FIG. 6;

(11) FIG. 9 shows a cross section of the line C-C of FIG. 6;

(12) FIG. 10 shows a profile view of a lower attachment system for a THSA;

(13) and

(14) FIG. 11 shows a cross section of the lower attachment system of FIG. 10.

DETAILED DESCRIPTION

(15) FIG. 4 shows a lower attachment system 25 for a THSA comprising a ballnut 101 with a trunnion 102, a failsafe plate 150, a secondary connection 140, and a sheet plate 120. The sheet plate 120 comprises a screw mount 121, a coupling portion 122, and a sheet portion 123. In use, a surface bracket (not shown) is pivotally mounted on the trunnion 102 so that movement of the lower attachment system 25 along a screwshaft (not shown) controls the position of the surface bracket and a flight control surface connected thereto.

(16) During normal operation, the primary load path passes through the ballnut 101 and the trunnion 102. In the case of a failure of the primary load path, a secondary trunnion (not shown) disposed in an aperture 142 of the secondary connection 140 bears against the secondary connection and transfers load through the secondary connection 140 to the failsafe plate 150 and the surface bracket connected thereto. When the primary load path fails, the secondary connection 140 is moved by the secondary trunnion (not shown), which causes breakage of the sheet plate 120. Specifically, a fuse pin 124 coupling the sheet portion 123 to the coupling portion 122 is arranged to break in case of primary load path failure, thereby decoupling the sheet portion 123 and the coupling portion 122.

(17) The sheet plate 120 is fixed to the secondary connection 140 at the first mounting point 144, and to the ballnut 101 at the second mounting point 104. The sheet plate 120 is mounted to the ballnut 101 via the screw mount 121 housing a screw 125. The coupling portion 122 is connected to the screw mount 121 via the screw 125 such that adjustment of the screw 125 causes movement of the coupling portion 122 relative to the screw mount 121.

(18) The coupling portion 122 is coupled to the sheet portion 123 of the sheet plate 120, so that the sheet portion 123 is moveable by adjustment of the screw 125. Therefore, once the sheet plate 120 is attached to the ballnut 101 at the second mounting point 104 via the screw mount 121, the screw 125 may be adjusted to align the sheet portion 123 with the first mounting point 144, and the sheet portion may then be connected to the secondary connection 140 e.g. by bolts.

(19) The sheet portion 123 may also be connected firstly to the secondary connection 140, while the coupling portion 122 is connected to the ballnut 101 via the screw mount 121. The screw 125 may then be adjusted to align the coupling portion 122 with the sheet portion 123 so that they may be coupled together e.g. by the fuse pin 124.

(20) The sheet plate 120 thus fits the distance between the first and second mounting points 144, 104 and sets the separation of the ballnut 101 and secondary connection 140. Upon failure of the primary load path, the secondary connection 140 is moved by the secondary trunnion (not shown) bearing against it in the aperture 142, thus causing the sheet portion 123 of the sheet plate 120 to break.

(21) FIG. 5 shows the same arrangement as depicted in FIG. 4 but from another perspective. The lower attachment system 25 comprises two sheet plates 120, one on either side of the ballnut 101. Both sheet plates 120 work in the manner described above.

(22) FIG. 6 shows the screw mount 121, screw 125 and coupling portion 122 of the sheet plate 120. These parts are used to fix the relative position between the primary load path and secondary load path. The secondary connection 140 and failsafe plate 150 are secondary load path parts.

(23) FIG. 7 shows the screw mount 121 which mounts the screw 125 to ballnut 101. Size and position fixing means 126 and 127 fix the size and/or position of sheet plate 120 in a first direction. A size and position fixing means 128 fixes the size and/or position of sheet plate 120 in a second direction. A locking means 129 locks the size and position fixing means 128 in a desired position. The coupling means 122 provides adjustment by changing the size and/or position of sheet plate 120 through a thread e.g. cooperating with the screw 125 in the screw mount 121. In normal use, the ballnut 101 forms part of the primary load path together with a primary load path component 111.

(24) FIG. 8 shows a cross section along the line B-B of FIG. 6. The sheet portion 123 is coupled to the coupling portion 122 by the fuse pin 124, which disconnects the two parts of the sheet plate 120 when the primary load path fails.

(25) FIG. 9 shows a cross section along the line C-C of FIG. 6. A fixing 145 fixes the sheet plate 120 to the secondary connection 140. A locking means 146 locks the fixing 145 in a desired position. An adjustment means 143 adjusts the size and/or position of sheet plate 120 through adjustment means 147 and secondary connection 140.

(26) FIG. 10 shows another view of the lower attachment system 25, and FIG. 11 shows a cross section of FIG. 10. The sheet plate 120 is coupled between the ballnut 101 and the secondary connection 140, with its size and/or position adjustable.