Patent Publication Number: US-8118524-B2

Title: Overrideable guide and vertical restraint for an air cargo system

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This is a Divisional of U.S. patent application Ser. No. 11/248,613 filed Oct. 13, 2005, now U.S. Pat. No. 7,429,157. The contents of the aforementioned parent application are incorporated by reference in their entirety. 
    
    
     BACKGROUND OF THE INVENTION 
     The present invention is related to a restraint assembly suitable for mounting on a centerline of an air cargo deck. More particularly, it is directed to such a restraint that is overrideable. 
     Commercial aircraft carry cargo in large containers and pallets called unit load devices (ULDs). ULDs are available in several different configurations with different lengths and widths. All ULDs must be retained during flight to prevent damage to the aircraft and the cargo. 
     Cargo aircraft normally carry ULDs that are either 96 inches wide, or 88 inches wide. To accommodate both widths, centerline restraints are mounted along the centerline of the aircraft. The centerline restraints includes a double-headed center guide/restraint located in the center of the centerline restraint to handle 96 inch wide ULDs and a pair of overrideable guide/restraints at opposite ends of the centerline restraint to handle 88 inch wide ULDs. 
     The overrideable guide/restraints are overrideable in the sense that they are capable of being deflected downwardly to enable an ULD to pass thereover. 
     On any given flight, a commercial aircraft may carry both 96 inch wide ULDs and 88 inch wide ULDs. 
     For 96 inch wide ULDs, the ULDs are restrained on one side by a fixed guide/restraint system located near the side wall of the aircraft and on the opposite side by one head of the center guide/restraint. When a 96 inch wide ULD is loaded into the aircraft fuselage and moved forward or aft into position, the ULD may contact and pass over any erect 88 inch overrideable end guide/restraint, forcing them downwards. 
     For 88 inch wide ULDs, the ULDs will still be restrained on the one side by the fixed guide/restraint system located near the side wall of the aircraft. On the opposite side, however, the ULDs will be restrained by the head of an overrideable guide/restraint belonging to the centerline restraint. 
     U.S. Pat. No. 5,011,348, in its FIGS. 2 and 3, depict a centerline restraint retaining an 88 inch wide ULD and a 96 inch wide ULD, respectively. The contents the &#39;348 patent are incorporated by reference to the extent necessary to understand the present invention. 
     SUMMARY OF THE INVENTION 
     In one aspect, the present invention is directed to an overrideable guide/restraint for an air cargo system. The overrideable guide/restraint comprises a guide body rotatable about a first rotational axis, the guide body having a first side and a second side that are axially spaced apart along the first rotational axis, and a vertical restraint secured to the guide body. In this device, the first side comprises a first channel having first and second stops that are spaced apart from one another, and the second side comprises a second channel having a third stop. 
     In another aspect, the present invention is directed to a centerline restraint for an air cargo system. The centerline system comprises a base and a first overrideable guide/restraint rotatably mounted on the base along a first rotational axis, wherein the overrideable guide/restraint is rotatable around the first rotational axis between a retracted position, an erect position and an overridden position. When the centerline restraint is mounted on a cargo floor, the overrideable guide/restraint has a sufficiently low profile so as to not interfere with the passing of a unit load device thereover, when the overrideable guide/restraint is in either the retracted position or the overridden position. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view of a centerline restraint in accordance with the present invention, with the center guide/restraint and the overrideable guide/restraint in the erect position. 
         FIG. 2  is a side view of the restraint of  FIG. 1 . 
         FIG. 3  is a perspective view of the restraint of  FIG. 1 , but with the overrideable guide/restraint in the overridden position. 
         FIG. 4  is a perspective view of the restraint of  FIG. 1 , but with the center guide/restraint in the retracted position and the overrideable guide/restraint in the retracted. 
         FIG. 5  is a perspective view of the base of the centerline restraint of  FIG. 1 . 
         FIG. 6  is a detailed view of the detent cluster surrounding a plunger hole in a side of the base. 
         FIG. 7  is an exploded view of overrideable guide/restraint. 
         FIG. 7A  is an exploded view of a lift handle assembly seen in  FIG. 7   
         FIG. 8  shows a second perspective view of an assembled overrideable guide/restraint showing the second leg having the dual depth channel. 
         FIG. 9  shows a first perspective view of an assembled overrideable guide/restraint showing the first leg having the single depth channel. 
         FIG. 10  shows one end of the centerline restraint of  FIG. 1  with the overrideable guide/restraint in the retracted position. 
         FIG. 11  shows only the plunger assembly and the overrideable guide/restraint in the retracted position with the second leg visible. 
         FIG. 12  shows only the plunger assembly and the overrideable guide/restraint in the retracted position with the first leg visible. 
         FIG. 13  shows one end of the centerline restraint of  FIG. 1  with the overrideable guide/restraint in the erect position. 
         FIG. 14  shows only the plunger assembly and the overrideable guide/restraint in the erect position with the second leg visible. 
         FIG. 15  shows only the plunger assembly and the overrideable guide/restraint in the erect position with the first leg visible. 
         FIG. 16  shows one end of the centerline restraint of  FIG. 1  with the overrideable guide/restraint in the overridden position. 
         FIG. 17  shows only the plunger assembly and the overrideable guide/restraint in the overridden position with the second leg visible. 
         FIG. 18  shows only the plunger assembly and the overrideable guide/restraint in the overridden position with the first leg visible. 
         FIG. 19  shows an exploded view of the centerline restraint of  FIG. 1 . 
         FIG. 20  shows an assembled view of a center guide/restraint assembly of the sort used in the centerline restraint of  FIG. 1 . 
         FIG. 21  shows an exploded view of the center guide/restraint assembly of  FIG. 20 . 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring generally to  FIGS. 1-4 , a centerline restraint  100  in accordance with the present invention has a longitudinal axis L extending along a base  200  having base side walls  202 ,  204  and an upper surface  206 . 
     Mounted in the base  200  is a center guide/restraint  500  for accommodating  96  inch ULDs. The center guide/restraint  500  includes two flipper-style vertical restraints  319  which face in opposite directions. The flipper-style vertical restraints  319  belonging to the center guide/restraint  500  guide a 96 inch ULD in the horizontal direction, and restrain the 96 inch ULD in the vertical direction. 
     The design and operation of the center guide/restraint  500  should be familiar to those skilled in the art.  FIG. 19  shows an exploded view of a centerline restraint  100  in accordance with the present invention, including the base  200 , the overrideable guide/restraints  300   a ,  300   b  discussed below and the known center guide/restraint  500 .  FIG. 20  shows an assembly of the center guide/restraint  500  together with its operating handle  502  and  FIG. 21  shows an exploded view of the assembly of  FIG. 20 . 
     The center guide/restraint  500  occupies either an erect position, as seen in  FIGS. 1-3 , or a retracted position, as seen in  FIG. 4 . A center release handle  502  is used to switch the center guide/restraint  500  between the two positions. Pressing the center release handle  502  unlocks a mechanism that permits rotation of the center guide/restraint  500  about its shaft axis, which is parallel to the longitudinal axis L. To move the center guide/restraint  500  from the erect position to the retracted position, an operator presses the center release handle  502  and rotates the center guide/restraint  500  until its upper portion enters the center guide/restraint cavity  504  formed in the upper surface  206  of the base  200 . To move the center guide/restraint  500  from the retracted position to the erect position, an operator again presses the center release handle  502  and this rotates the center guide/restraint  500  upward under spring force until it locks in the erect position. 
     The centerline restraint of the present invention also includes a pair of overrideable guide/restraints  300   a ,  300   b  made in accordance with the present invention. 
     With reference to  FIGS. 2 and 4 , overrideable guide/restraint  300   a  has a first axle  306   a  which rotates about a first rotational axis A while overrideable guide/restraint  300   b  has a second axle  306   b  which rotates around a second rotational axis B. Rotational axes A and B are both perpendicular to the centerline restraint&#39;s longitudinal axis L. As seen in  FIG. 5 , the rotational axes A, B pass through holes  212  formed in the side walls  202 ,  204  of the base  200 , the holes  212  being configured to receive and support members forming the axles of the overrideable guide/restraints. Each of the overrideable guide/restraints  300   a ,  300   b  may selectively occupy any one of three rotational positions at a time: a retracted position, an erect position and an overridden position, and may be locked in the latter two of these. 
       FIGS. 1 and 2  show both overrideable guide/restraints  300   a ,  300   b  locked in the erect position. 
     Each overrideable guide/restraint  300   a ,  300   b  includes a flipper-style vertical restraint  320 , which may or may not be the same as the flipper-style vertical restraint  319  on the center guide/restraint  500 . When the centerline restraint  100  is mounted on the centerline of cargo deck, the flipper-style vertical restraints  320  of the overrideable guide/restraints  300   a ,  300   b , when in the erect position, are configured to guide an 88 inch wide ULD in a horizontal direction transverse to longitudinal axis L, and restraint the 88 inch wide ULD in a vertical direction. 
       FIG. 3  shows both overrideable guide/restraints  300   a ,  300   b  locked in the overridden (or “outboard”) position. In this position, an end portion of the flipper head  322  of the flipper-style vertical restraint  320  enters a cutout  106   a ,  106   b  formed in the base  200 . This allows the overrideable guide/restraints  300   a ,  300   b  to stay within the footprint of the base  200 , even when overridden in an outboard direction. 
       FIG. 4  shows both overrideable guide/restraints  300   a ,  300   b  in the retracted (or “inboard”) position. In this position, each of the overrideable guide/restraints  300   a ,  300   b  rotates backward around its respective axis A, B, until it lays in its inboard cavity  104 , which is formed in the top surface  206  of the base  200 . 
     When the centerline restraint  100  is mounted on a cargo floor, the overrideable guide/restraints  300   a ,  300   b  have a sufficiently low profile so as to not interfere with the passing of a unit load device thereover, when the overrideable guide/restraints  300   a ,  300   b  are in either the retracted position or locked down in the overridden position. 
     It should be evident from the foregoing discussion with respect to  FIGS. 1-4  that the center guide/restraint  500  and each of the overrideable guide/restraints  300   a ,  300   b  can be moved among their various positions independently of each other. 
     Overrideable guide/restraint  300   a  is rotated from the locked, overridden position of  FIG. 3  to the locked erect position of  FIGS. 1 and 2  by pulling only on lift handle  302   a  in an outward direction, in a direction opposite the longitudinal axis L. When only the lift handle  302   a  is pulled, the overrideable guide/restraint  300   a  rotates in the direction of the center guide/restraint  500  under torsional spring force, and comes to rest in the erect position. 
     Overrideable guide/restraint  300   a  is rotated from the erect position of  FIG. 1  to the retracted position of  FIG. 4  by simultaneously pulling both lift handles  302   a ,  304   a  in an outward direction, in a direction opposite the longitudinal axis L. When both lift handles  302   a ,  304   a  are pulled, overrideable guide/restraint  300   a  rotates backwards in the direction of the center guide/restraint  500  from the erect position under torsional spring force, and comes to rest in the inboard cavity  104 . It should be noted here that pulling both lift handles  302   a ,  304   a  from the overridden position also results in the overrideable guide/restraint  300   a  coming to rest in the retracted position. 
     Similarly, overrideable guide/restraint  300   b  is raised from the locked, overridden position of  FIG. 3  to the erect position of  FIGS. 1 and 2  by pulling only on lift handle  304   b ; and overrideable guide/restraint  300   b  is rotated from the erect position of  FIG. 1  to the retracted position of  FIG. 4  by simultaneously pulling on both lift handles  302   b ,  304   b.    
     As discussed further below with respect to  FIGS. 7-18 , the lift handles  302   a ,  302   b ,  304   a ,  304   b  are operatively connected to a spring-biased plunger  382  that is inwardly biased in the direction of the longitudinal axis L. Pulling on a lift handle withdraws a head  384  of the plunger  382  from abutment against a stop  372 ,  377 ,  379  formed on a corresponding overrideable guide/restraint. This frees that corresponding overrideable guide/restraint, under force of one or more torsion springs  334 ,  336 , to rotate in the direction of the retracted position. 
     In the opposite direction, rotation from the retracted position to the erect position for both overrideable guide/restraints  300   a ,  300   b  is done manually. Rotation from the erect position to the overridden position can also be accomplished manually, though more typically takes place when a ULD passes over the overrideable guide/restraint. 
     The overrideable guide/restraints  300   a ,  300   b  have identical structure and operation, and so from this point forward, the structure and operation of only one of these,  300   a , will be explained. 
       FIG. 7  shows an exploded view of an overrideable guide/restraint  300   a  of the sort seen in the earlier figures. 
     The overrideable guide/restraint comprises a yoke-shaped guide body  308  having a first leg  310  and a second leg  312 . The guide body is rotatable around a rotational axis (e.g., rotational axis A) and the legs  310 ,  312  are axially separated from one another along the rotational axis. A channel  370 , discussed further below, can be seen in the second leg  312 . Mated to the body  308  is a flipper-style vertical restraint  320 . The flipper-style vertical restraint  320  comprises a restraint head  322  to which is attached a restraint shank  324 . 
     A through bore  325  is formed in the restraint shank  324  to accept a dowel pin  356 . A washer  358  and a leaf spring  354  are mounted around a lower portion of the restraint shank  324 , within the guide body  308 . Opposing edges of the leaf spring  354  are separated by an end of the dowel pin  356 . The dowel pin  356 , which rotates with the restraint shank  324 , is used as an actuator to abut and rotate the opposing edges of leaf spring  354 . Thus, when the restraint head  322  turns in a first direction, the dowel pin  356  turns in the same direction, compressing the leaf spring  354  and creating a restoring force that urges the vertical restraint  320  towards its neutral position within the guide body  308 . People skilled in the art are familiar with using such actuators and leaf springs in the art of implementing vertical restraints. 
     The terminal end of the restraint shank  324  is provided with a threaded member  326 . A washer  350  and nut  352  are used in conjunction with the threaded member  326  to secure the vertical restraint  320  to the guide body  308 . 
     A wear strip  327  is attached to a wear strip mounting surface  328  of the guide body  308  by screws  329 . The wear strip  327  helps protect the upper surface of the overrideable guide/restraint  300   a  from ULDs and other objects that may bump into it. Thus, the wear strip  327  is typically made from a harder material than the guide body  308 . 
     The overrideable guide/restraint  300   a  is rotatably mounted on the base  200 . A pin  330  is configured to support the overrideable guide/restraint  300   a . The pin  330  is threaded through a pair of openings  212  formed on the sides  202 ,  204  of the base, across from one another. A cotter pin  333  passing through a through hole formed at one end of the pin  330  and secures the pin to the base  200 . 
     A portion of the pin  330  is covered by a sleeve  332 . The sleeve  332  is configured to rotate on a first pair of bushings  314  implanted in circular openings formed in the legs  310 ,  312 , and a second pair of bushings  316  mounted in the holes  212 . A pair of torsion springs  334 ,  336  are mounted on the sleeve  332 . A first torsion spring end  338  anchors the spring  334 ,  336  to a hole formed the base  200  while a second torsion spring end is anchored to a hole formed on a surface of the overrideable guide/restraint itself. Thus, when the overrideable guide/restraint is rotated, the springs  334 ,  336  provide a torsional spring force that urges the overrideable guide/restraint  300   a  back towards the retracted position. 
       FIG. 7A  shows an exploded view of the lift handle assembly  380  seen in  FIG. 7 . The lift handle assembly  380  includes a lift handle  302   a , a plunger  382 , a coil spring  390  and a plunger pin  392 . 
     The lift handle  302   a  has the same structure as the other lift handles  304   a ,  302   b ,  304   b  seen in the figures. The lift handle  302   a  comprises a cup-shaped hollow body  395  with a rim  397 , and a pair of axially extending projections  396  formed on the rim  397  and diametrically across from one another. The lift handle  302   a  also includes a pair of handle through bores  394  formed in the body for receiving a plunger pin  392 . 
     The plunger  382  comprises an enlarged head portion  384  connected to a cylindrical shaft  386 . The head portion  384  is configured and dimension to travel along a channel formed in the overrideable guide/restraint. At the far end of the shaft  386 , opposite from the head  384 , is a pair of shaft through bores  388 . 
     When the lift handle assembly  380  is being assembled, the coil spring  390  is mounted over the plunger shaft  386  and the plunger shaft is inserted through an opening  210  (see  FIG. 6 ) formed in a side wall  202  of the base  200 . The far end of the shaft  386  is then inserted into the hollow body  395  of the lift handle  302   a  with the handle through bores  394  and the plunger through bores  388  aligned Finally, the plunger pin  392  inserted in the through bores to secure the lift handle  302   a  to the plunger  382 . 
     When so assembled, the coil spring  390  biases apart the lift handle  302   a  and the plunger  382 . Pulling on the lift handle  302   a  in an outward direction draws the plunger  382  in a direction away from the longitudinal axis L and towards the side wall  202  of the base  200 . It also causes the coil spring  390  to compress against an inner surface of the side wall  202 , thereby creating a restoring force that urges the plunger  382  back towards the longitudinal axis L. 
       FIG. 8  shows a perspective view of the overrideable guide/restraint  300   a  in the erect position with the first leg or side  310  of the body  308  visible. A first channel  374  is formed along this first side  310 . The first channel  374  includes a shallow first track  376  terminating in a first plunger stop  377 . Communicating with the shallow track  376  is a deep second track  378  terminating in a second plunger stop  379 . The second plunger stop  379  is farther inward along rotational axis A than the first plunger stop  377 . Thus, the first side  310  of the body  308  is provided with two rotational stops  377 ,  379  which are at different axial depths and positioned at different portions of the first channel  374 , and thus are spaced apart from one another both rotationally and axially. 
       FIG. 9  shows a perspective view of the overrideable guide/restraint  300   a  in the erect position with the second leg or side  312  of the body  308  visible. A second channel  370  is formed along this second side  312 . The second channel  370  comprises a shallow third track  371  terminating in a third plunger stop  372 . The shallow third track  371  and the shallow first track  376  have approximately the same depth. Similarly, the third plunger stop  372  and the first plunger stop  377  are approximately the same distance inward along the rotational axis A from their respective sides. Thus, the second side  312  of the body  308  is provided with a single rotational stop  372  at the same axial depth as the first plunger stop  377 . Furthermore, the two sides of the guide body are axially separated from one another along the rotational axis A. As seen in  FIGS. 7-9 , the first channel  374  faces in an outward direction of the guide body along a first direction of the first rotational axis A, while the second channel  370  faces in an outward direction of the guide body along a second, opposite direction of the first rotational axis A. 
       FIGS. 10 ,  11  and  12  all show the overrideable guide/restraint  300   a  in the retracted position.  FIG. 10  shows this in the context of the centerline restraint of  FIG. 1 .  FIGS. 11 and 12  show the overrideable guide/restraint  300   a  with the base  200  removed and the lift handles  302   a ,  304   a  and the lift handle assemblies  380  left in place to show their relationship to the first channel  374  ( FIG. 11 ) and the second channel  370  ( FIG. 12 ).  FIG. 11  shows the overrideable guide/restraint  300   a  from the same perspective as  FIG. 10 . As seen in  FIGS. 11 and 12 , when the overrideable guide/restraint  300   a  is in the retracted position, the lift handle assemblies  380  (and thus the plunger heads  384 ) on either side are free and clear of the first channel  374  and the second channel  370 . Since no plunger head  384  abuts any of the stops  372 ,  377  or  379 , the overrideable restraint/guide  300   a , under a torsional spring bias urging it towards the retracted position, rests in the cavity  104 . 
       FIGS. 13 ,  14  and  15  all show the overrideable guide/restraint  300   a  in the erect position.  FIG. 13  shows this in the context of the centerline restraint of  FIG. 1 .  FIGS. 14 and 15  show the overrideable guide/restraint  300   a  with the base  200  removed and the lift handles  302   a ,  304   a  and the lift handle assemblies  380  left in place to show their relationship to the first channel  374  ( FIG. 14 ) and the second channel  370  ( FIG. 15 ).  FIG. 14  shows the overrideable guide/restraint  300   a  from the same perspective as  FIG. 13 . As seen in  FIG. 14 , the plunger head  384  associated with lift handle  302   a  is positioned in the shallow first track  376  of the first channel  374  and abuts the first plunger stop  377  of the first channel  374 . As seen in  FIG. 15 , the plunger head  384  associated with lift handle  304   a  is positioned in second channel  370  and abuts the third stop  372  (not shown). Since the plunger heads  384  associated with both lift handles  302   a ,  304   a  abut stops  377 ,  372 , the overrideable restraint/guide  300   a , despite the torsional spring bias urging it towards the retracted position, remains erect. 
       FIGS. 16 ,  17  and  18  all show the overrideable guide/restraint  300   a  in the overridden position.  FIG. 16  shows this in the context of the centerline restraint of  FIG. 1 .  FIGS. 17 and 18  show the overrideable guide/restraint  300   a  with the base  200  removed and the lift handles  302   a ,  304   a  and the lift handle assemblies  380  left in place to show their relationship to the first channel  374  ( FIG. 17 ) and the second channel  370  ( FIG. 18 ).  FIG. 17  shows the overrideable guide/restraint  300   a  from the same perspective as  FIG. 16 . As seen in  FIG. 17 , the plunger head  384  associated with lift handle  302   a  is positioned in the deep second track  378  of the first channel  374  and abuts the second plunger stop  379  of the first channel  374 . As seen in  FIG. 18 , the plunger head  384  associated with lift handle  304   a  is positioned in the middle of second channel  370  and does not abut the third stop  372 . Since the plunger head  384  associated with lift handle  302   a  abut stop  379 , the overrideable restraint/guide  300   a , despite the torsional spring bias urging it towards the retracted position, remains in the overridden position. 
     The overridden position may be realized when an ULD passes over an overrideable restraint/guide  300   a  from behind when in the erect position. In the preceding discussion, the overrideable restraint/guide  300   a  becomes locked in the overridden position when the plunger head  384  associated with the lift handle  302   a  abuts the axially inward stop  379  associated with the deep second track  378 . 
     This “locking” function may selectively be disabled, thereby allowing the overrideable restraint/guide  300   a  to spring back up to the erect position, each time it is temporarily forced downward into the overridden position. Selective disablement is facilitated by a detent cluster  220  (See  FIGS. 5 and 6 ) formed around the hole  210  associated with lift handle  302   a.    
     As best seen in  FIG. 6 , the detent cluster  220  comprises two pairs of detents  222 ,  224 . Rotationally about the hole  210 , the members from each pair are 180° apart, and adjacent detents are 90° apart. The first pair of detents  222  have a first depth in the side wall  202  and the second pair of detents  224  have a second depth in the side wall, the second depth being deeper than the first depth. 
     As discussed above with respect to  FIG. 7A , the cup-shaped hollow body  395  of the lift handle  302   a  has a rim  397  provided with a pair of axially extending projections  396 . The diameter of the rim  397  is approximately the same as the spacing between members of either pair of detents. The axially extending projections  396  likewise have substantially the same spacing, and so may be inserted into either pair of detents  222 ,  224 . 
     When the axially extending projections  396  are inserted into the second pair of detents  224  (the deeper pair), the lift handle  302   a  can be positioned closer to the first channel  374  of the overrideable restraint/guide  300   a  and so its associated plunger head  384  is capable of entering the deep second track  378  and abutting the second plunger stop  379 . In such case, when the overrideable restraint/guide  300   a  is forced from the erect position to the overridden position, the associated plunger head  384  abuts the second plunger stop  379  and locks the device in the overridden position. 
     On the other hand, when the axially extending projections  396  are inserted into the first pair of detents  222  (the shallower pair), the lift handle  302   a  is positioned slightly farther from the first channel  374  of the overrideable restraint/guide  300   a  and so its associated plunger head  384  is no longer capable of entering the deep second track  378  or abutting the second plunger stop  379 . In such case, when the overrideable restraint/guide  300   a  is forced from the erect position to the overridden position, the associated plunger head  384  does not abut the second plunger stop  379  and so the device returns to the erect position from the overridden position, once the ULD or other object no longer pushes down the overrideable restraint/guide  300   a.    
     It can be seen from the foregoing, then, that one may selectively enable or disable locking in the overridden position simply by (a) slightly pulling out the lift handle  302   a  until its projections  396  clear the pair of detents  222 ,  224  they were occupying, (b) rotating the lift handle by 90°, and (c) allowing the projections  396  to enter the other pair of detents  224 ,  222 . 
     The centerline restraint of the present invention provides lateral and vertical restraint of 88 inch wide ULDs and also 96 inch ULDs. 
     As seen from the above description, in the centerline restraint of the present invention, the overrideable guide/restraint has a constant axis of rotation which does not move laterally along the longitudinal axis of the centerline restraint. The overrideable guide/restraint is thus able to pivot in place between a retracted position, an erect position and an overridden position. This contrasts with prior art designs in which a sliding mechanism is needed to laterally translate the axis of the overrideable guide/restraint along the longitudinal axis. Furthermore, in the centerline restraint of the present invention, the overrideable guide/restraint can selectively be configured to either (a) lock in place once forced into the overridden outboard position, or (b) spring back up after being temporarily forced into the overridden outboard position. 
     Another feature of the present invention is that when the overrideable guide/restraint is in the overridden outboard position, no portion of the overrideable guide/restraint extends past the footprint of the base. This contrasts with prior art devices that require additional clearance between the parts, which could create regions of reduced strength in the centerline restraint. 
     Finally, in the centerline restraint of the present invention, the flight load is reacted into the vertical walls of the base through the retractable plungers and pin mount. This contrasts with prior art designs in which the loads are reacted into the bottom of the base, oftentimes necessitating a thicker base. 
     While the present invention has been described herein above in connection with a plurality of aspects and embodiments, it is understood that these aspects and embodiments were presented by way of example with no intention of limiting the invention. Accordingly, the present invention should not be limited to any specific embodiment or aspect, but rather construed in breadth and broad scope in accordance with the recitation of the claims appended hereto.