Self locking end stops for aircraft control surfaces

Abstract: A releasable, self-locking end stop arrangement (8) for restricting the linear displacement of an aircraft flight control surface eg: a leading edge slat (5). The end stop (8) extends laterally through and projects to either side of the slat support track (3) such that it is effectively in alignment with stop plate (7) mounted upon wing leading edge ribs 6. The end stop (8) comprises interlockable shouldered studs (12,13) incorporating co-operating lock threads and circlip (24) engaging annular grooves (16, 21) forming a detent. By this arrangement the end stops comprise self-contained, self-locking components without any reliance on separate fastening and inadvertent release is prevented.

Description: This invention relates to self-locking end stops for use with aircraft control surface installations such as leading edge slats and trailing edge flaps which are supported upon arcuate tracks slidably mounted upon the aircraft wing by which means the control surface is moved from a stowed to a deployed location and vice versa. It is important to ensure that when the control surface is deployed it cannot inadvertently overtravel and become detached from the wing. To prevent such an unlikely occurrence an end stop is positioned adjacent the end of each track for engaging a stop plate on the wing at the extreme range of control surface movement. One such device is disclosed in document EP-A-O 291 328, British Aerospace in which such an end stop is used, but is not releasable for removing the control surface. However, it is also necessary to remove the control surface installation from the aircraft for routine servicing or replacement and so the end stops must be readily removable yet of such construction that they are compact, of minimum component parts but positively locked when assembled into place to ensure against control surface jamming. According to the present invention there is provided a self-locking end stop arrangement for restricting the linear displacement of an aircraft flight control surface said flight control surface being mounted upon two or more longitudinal support tracks slidably engaging the aircraft wing by which means the control surface is deployed forwardly or rearwardly with respect to said wing and said end stop arrangement comprising means which when installed protrude from said support tracks such that the protrusions align with and contact means mounted upon the wing structure when the control surface is moved to an extreme forward or rearward position, thus preventing inadvertent detachment of the control surface from the aircraft, wherein the self-locking end stop arrangement is readily releasable for removal of the flight control surface from the aircraft wing and the protruding means and co-operating contact means thereof respectively comprise first and second interlockable studs protruding laterally from opposite sides of the support tracks on the one hand and stop plates on the other hand. One embodiment of the invention will now be described, by way of example only, and with reference to the following drawings in which:- Figure 1 illustrates, in side elevation an aircraft leading edge slat installation. Figure 2 is a part section through the installation taken along the line '2-2' in Figure 1. Figure 3 is a part sectioned elevation through a first component part of the end stop. Figure 4 is a localised enlargement of one portion of the component of Figure 3. Figure 5 is a longitudinal section through a second component part of the end stop. Figure 6 is a localised enlargement of one portion of the component of Figure 5. Figure 7 is an end view on the first and second component parts in direction of arrow 7 in Figures 3 and 5. Referring to the drawings, Figure 1 illustrates a cross-sectional side elevation on a typical leading edge slat installation in which a slat 1 is supported upon a wing fixed leading edge portion 2 by means of arcuate support beams 3, generally two in number for each spanwise portion of slat. The support beam is mounted in rolling engagement with the wing leading edge by means of spaced apart rollers 4 which are generally straddle mounted between spaced apart pairs of leading edge ribs 6. By this arrangement the slat may be deployed from its stowed cruise configuration where it conforms to wing aerodynamic profile to a fully extended 'high lift' configuration 5. For clarity in Figure 1 the nearest leading edge rib 6 is removed to disclose the arcuate track arrangement in more detail. Similarly the arcuate track 3 is locally cut away to show a stop plate 7 which is attached to the inner face of the rib 6 and, as will be seen in Figure 2, is typical for both ribs. Adjacent the end of the arcuate track is the self-locking end stop 8 in accordance with the invention and this is shown on the track in its stowed position and in the deployed sense lying adjacent the stop plate 7. In Figure 2 the disposition of the ribs 6 with respect to the arcuate track 3 is shown. Although not illustrated here the arcuate track is of inverted U-shaped or top hat section with upper and lower outwardly facing side flanges providing roller bearing surfaces. The end stop assembly 8 lying transversely of the beam projects beyond each edge boundary of the track 3 to form the stop surface for contacting stop plates 7 as necessary. It is with the slat in this deployed location that the end-stop is either assembled or removed, access holes 9 being provided in each leading edge rib 6 for insertion or removal of the component parts and for socket spanner access. The end stop assembly effectively comprises two component parts, interlocking shouldered studs 12 and 13. Stud 12, as illustrated in Figures 3 and 4, comprises a shouldered stud portion 14a, a plain shank portion 15 incorporating a circlip retaining groove 16 located part way along its length and a threaded shank portion incorporating a lockthread 17, for example a 'SPIRALOCK' thread form, (SPIRALOCK is the Registered Trade Mark of the 'KAYNAR' company). The stud portion 14a includes a counterbore 18 over a greater portion of its length and further includes a female square drive socket 23 of well known form (as for example in accordance with BS 4006). Stud 13 as illustrated in Figures 5 and 6 comprises a shoulder stud portion, incorporating along its length a counterbore 19 including a circlip engaging groove 21 dimensionally compatible with the mating portion 15 of the stud 12. The stud 13 further includes a threaded bore portion 22 incorporating a lock thread (for example a SPIRALOCK thread form as previously referred to) compatible with the co-operating stud 12 and the stud head similarly includes a female square drive socket, 23 also preferable in accordance with BS 4006. A circlip 24 is incorporated into the recess 16 in the stud 12. On assembly the respective studs 12 and 13 are inserted from each side and rotated by means of socket spanners engaging the head sockets 23 via the rib access holes 9 until the respective lock threads are engaged by means of a lead in 10 and the parts are in locking abutment. Simultaneously the circlip 24 will engage with the co-operating groove 21 in the stud. This circlips effectively constitutes a detent and a secondary locking feature and thus it will be seen that the present arrangement comprises a pair of self-contained, self-locking components without any reliance on separate fastenings, bolted joints etc. On final assembly the studs project from each side of the track to form the stop. Although the invention is described in the context of a wing leading edge slat installation it is equally application to trailing edge flaps or any similar application involving the use of arcuate tracks where there is a requirement to provide restriction in linear movement.

Claims: A self-locking end stop arrangement (8) for restricting the linear displacement of an aircraft flight control surface (1) said flight control surface (1) being mounted upon two or more longitudinal support tracks (3) slidably engaging the aircraft wing (2) by which means the control surface (1) is deployed forwardly or rearwardly with respect to said wing (2) and said end stop arrangement (8) comprising means (12,13) which, when installed, protrude from said support tracks (3) such that the protrusions (14) align with and contact means (7) mounted upon the wing structure (6) when the control surface is moved to an extreme forward or rearward position, thus preventing inadvertent detachment of the control surface from the aircraft, characterised in that the self-locking end stop arrangement (8) is readily releasable for removal of the flight control (1) suface from the aircraft wing (2) and the protruding means and co-operating contact means thereof respectively comprise first and second interlockable studs (12, 13) protruding laterally from opposite sides of the support tracks (3) on the one hand and stop plates (7) on the other hand. An end stop arrangement according to Claim 1 in which said first stud (12) includes a shouldered stud portion (14a), a plain shank portion (15) incorporating an annular groove (16) for retaining a circlip (24) and a threaded shank portion (20), and a square drive socket (23) in the end of the shouldered stud portion (14a) said second stud (13) including a shouldered stud portion (14b) having at one end a counterbore (19) including a circlip engaging annular groove (21), at the opposite end a square drive socket (23) and an interconnecting threaded bore (22), the threads associated with said first stud (12) and second stud (13) being of the lockthread type, the arrangement being such that said first and second studs (12,13) are inserted into the support track (3) from their respective sides such that they become engaged one with the other and differentially rotated by drive means, engaging said sockets (23) until they are in locking abutment with each other and prevented from loosening rotation by interlocking of the respective thread portions, the circlip (24) engaging the annular groove (21) to form a detent.

Inventors: BRITTON JOHN, BRITTON, JOHN
Applicants: BRITISH AEROSPACE, BRITISH AEROSPACE PUBLIC LIMITED COMPANY
Application year: 1990
Main classification: B64C9
IPC codes: B64C9