Patent Publication Number: US-2022219811-A1

Title: Landing gear door system for a landing gear compartment

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     The present application claims the benefit of priority to the U.S. Provisional Application No. 63/135,294 filed Jan. 8, 2021, which is hereby incorporated by reference in its entirety. 
    
    
     INTRODUCTION 
     This disclosure relates to landing gear door systems for the landing gear compartment of an aircraft. 
     Traditional nose landing gear for an aircraft may either be fixed or retractable. Fixed landing gear designs are simpler, but the protrusion of the landing gear into the airstream during flight causes undesirable drag, turbulence and vibration which compromises flight dynamics and imposes stress and wear upon the landing gear. On the other hand, retractable landing gear may be retracted into the nose or fuselage after takeoff, thus avoiding the exposure of the landing gear to the airstream during flight. Furthermore, once the nose landing gear is retracted, the aperture through which the landing gear is retracted is typically covered by one or more hinged doors whose outer surface closely matches the shape and curvature of the surrounding fuselage. However, such retractable nose landing gear systems typically require egress deployment of the one or more doors when the landing gear is extended for landing. This means the one or more doors are opened outward from the fuselage, and thus into the airstream. Similar to the fixed landing gear designs, this exposure of the egress doors to the high-speed airstream causes undesirable drag, turbulence and vibration which compromises flight dynamics and imposes stress and wear upon the egress doors. 
     SUMMARY 
     According to one embodiment, a landing gear door system for a landing gear compartment includes a door pivotable about a pivot pin configured for disposition in a longitudinal direction on an airframe, the door having a door panel rigidly connected with an arm such that the door panel and arm generally form a V-shape as viewed in the longitudinal direction, and a mechanism configured to rotate the door about the pivot pin between a closed position, in which an outer surface of the door panel is configured to provide aerodynamic continuity with an outer aircraft skin of the airframe, and an open position, in which the door is rotated into the landing gear compartment and an opening is exposed. 
     The door panel and arm may be rigidly connected with each other at a vertex portion of the door, with the pivot pin extending through the vertex portion. The pivot pin may be configured for rotatable connection with one of the outer aircraft skin and a mounting structure within the landing gear compartment. The door panel may have an arcuate profile as viewed in the longitudinal direction so as to provide the aerodynamic continuity with the outer aircraft skin in the closed position, and the arm may have a curved or bent profile as viewed in the longitudinal direction, wherein the curved or bent profile has an apex which extends away from the door panel. 
     The mechanism may be configured for mounting within the landing gear compartment. The mechanism may include: a connecting member having opposed first and second connecting member ends, wherein the first connecting member end is pivotably connected to the arm; a linkage having opposed first and second linkage ends, wherein the first linkage end is pivotably connected to the second connecting member end; a lever having opposed first and second lever ends and a fulcrum point between the first and second lever ends, wherein the first lever end is pivotably connected to the second linkage end and the fulcrum point is configured for rotatable connection with a first mounting point within the landing gear compartment; and an actuator rotatably connected to the second lever end and configured for selectively urging the second lever end in a first direction toward the opening and in a second direction away from the opening. 
     At least one of the connecting member, the linkage, and a portion of the lever between the fulcrum point and the second lever end may be configured to extend and retract in length. The landing gear door system may further include a strut having opposed first and second strut ends, wherein the first strut end is pivotably connected to the first linkage end and the second connecting member end, and the second strut end is pivotably connected to one of a second mounting point within the landing gear compartment and the outer aircraft skin. The strut may be configured to extend and retract in length, and the strut may include a strut extender configured for selectively urging or allowing the strut to extend and retract in length. The first lever end and the second linkage end may define a first joint therebetween, the first linkage end and the second connecting member end may define a second joint therebetween, and the first connecting member end and the arm may define a third joint therebetween, wherein when the first and second joints and the pivot pin are disposed along a substantially straight line, the third joint is disposed outboard of the substantially straight line. 
     According to another embodiment, a nose landing gear door system for a nose landing gear compartment includes: a door pivotable about a pivot pin configured for disposition in a longitudinal direction on an airframe, the door having a door panel rigidly connected with an arm such that the door panel and arm generally form a V-shape as viewed in the longitudinal direction; and a mechanism configured for mounting within the nose landing gear compartment and configured to rotate the door about the pivot pin between a closed position, in which an outer surface of the door panel is configured to provide aerodynamic continuity with an outer aircraft skin of the airframe, and an open position, in which the door is rotated into the nose landing gear compartment and an opening is exposed. The mechanism includes: a connecting member having opposed first and second connecting member ends, wherein the first connecting member end is pivotably connected to the arm; a linkage having opposed first and second linkage ends, wherein the first linkage end is pivotably connected to the second connecting member end; a lever having opposed first and second lever ends and a fulcrum point between the first and second lever ends, wherein the first lever end is pivotably connected to the second linkage end and the fulcrum point is configured for rotatable connection with a first mounting point within the nose landing gear compartment; and an actuator rotatably connected to the second lever end and configured for selectively urging the second lever end in a first direction toward the opening and in a second direction away from the opening. 
     At least one of the connecting member, the linkage, and a portion of the lever between the fulcrum point and the second lever end may be configured to extend and retract in length. The nose landing gear door system may further include a strut having opposed first and second strut ends, wherein the first strut end is pivotably connected to the first linkage end and the second connecting member end, and the second strut end is pivotably connected to one of a second mounting point within the nose landing gear compartment and the outer aircraft skin. The strut may include a strut extender configured for selectively urging or allowing the strut to extend and retract in length. The first lever end and the second linkage end may define a first joint therebetween, the first linkage end and the second connecting member end may define a second joint therebetween, and the first connecting member end and the arm may define a third joint therebetween, wherein when the first and second joints and the pivot pin are disposed along a substantially straight line, the third joint is disposed outboard of the substantially straight line. 
     According to yet another embodiment, a nose landing gear door system for an aircraft includes: (a) an airframe having a nose landing gear compartment surrounded by an outer aircraft skin; (b) a door pivotable about a pivot pin disposed in a longitudinal direction on the airframe, the door having a door panel rigidly connected with an arm such that the door panel and arm generally form a V-shape as viewed in the longitudinal direction; and (c) a mechanism mounted within the nose landing gear compartment and configured to rotate the door about the pivot pin between a closed position, in which an outer surface of the door panel is configured to provide aerodynamic continuity with the outer aircraft skin of the airframe, and an open position, in which the door is rotated into the nose landing gear compartment and an opening is exposed. In this embodiment, the mechanism includes: (i) a connecting member having opposed first and second connecting member ends, wherein the first connecting member end is pivotably connected to the arm; (ii) a linkage having opposed first and second linkage ends, wherein the first linkage end is pivotably connected to the second connecting member end; (iii) a lever having opposed first and second lever ends and a fulcrum point between the first and second lever ends, wherein the first lever end is pivotably connected to the second linkage end and the fulcrum point is rotatably connected with a first mounting point within the nose landing gear compartment; and (iv) an actuator rotatably connected to the second lever end and configured for selectively urging the second lever end in a first direction toward the opening and in a second direction away from the opening. 
     In this embodiment, the nose landing gear door system may further include a strut having opposed first and second strut ends, wherein the first strut end is pivotably connected to the first linkage end and the second connecting member end, and the second strut end is pivotably connected to one of a second mounting point within the nose landing gear compartment and the outer aircraft skin. Also in this embodiment, the first lever end and the second linkage end may define a first joint therebetween, the first linkage end and the second connecting member end may define a second joint therebetween, and the first connecting member end and the arm may define a third joint therebetween, wherein when the first and second joints and the pivot pin are disposed along a substantially straight line, the third joint is disposed outboard of the substantially straight line. 
     The above features and advantages, and other features and advantages, of the present teachings are readily apparent from the following detailed description of some of the best modes and other embodiments for carrying out the present teachings, as defined in the appended claims, when taken in connection with the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic front view of a landing gear door system in a closed position. 
         FIG. 2  is a schematic front view of a landing gear door system in an open position. 
         FIG. 3  is a schematic front view of a landing gear door system in an intermediate position. 
         FIGS. 4A-L  illustrate a sequence of schematic front views of a landing gear door system, from the closed position through various intermediate positions to the open position, and then from the open position through various other intermediate positions to the closed position. 
     
    
    
     DETAILED DESCRIPTION 
     Referring now to the drawings, wherein like numerals indicate like parts in the several views, a landing gear door system  20  for a landing gear compartment  12  (e.g., for an aircraft  15 ) is shown and described herein. 
       FIGS. 1-3  show schematic front views of the landing gear door system  20  in a closed position  100 , an open position  104 , and an intermediate position  108 , respectively. As further described below,  FIG. 1  shows a first configuration using various extending/retracting portions  58 ,  68 ,  78 ,  98 , while  FIGS. 2-3  show a second configuration without such extending/retracting portions  58 ,  68 ,  78 ,  98 . 
     Also shown in lower-left of each drawing is a reference showing a longitudinal direction  21  (represented by a circle with a “point” or dot in it, indicating that the positive longitudinal direction is pointed out of the plane of each drawing toward the viewer), a lateral direction  23  (represented by an arrow pointing to the right, indicating the positive or portward lateral direction), and a vertical direction  29  (represented by an arrow pointing upward, indicating the positive or upward vertical direction). Note that while the “point” and two arrows of this reference indicate the positive longitudinal, lateral and vertical directions  21 ,  23 ,  29 , the opposite or negative directions are likewise implied (even though they are not explicitly shown). With respect to the conventional layout of a fixed-wing aircraft  15 , the longitudinal direction  21  runs forward and rearward and is parallel to the roll axis, the lateral direction  23  runs to port and to starboard and is parallel to the pitch axis, and the vertical direction  29  runs upward and downward and is parallel to the yaw axis. Also shown at the top of  FIG. 1  are downward and upward directions  82 ,  84  (parallel to the vertical direction  29 ), as well as inboard and outboard directions  86 ,  88 . 
     While traditional nose landing gear door systems require egress deployment of one or more hinged doors, the landing gear door system  20  described herein provides the advantage of ingress deployment of one or more pivotable doors  22 . 
     According to one embodiment, a landing gear door system  20  for a landing gear compartment  12  includes a door  22  pivotable about a pivot pin  44  configured for disposition in a longitudinal direction  21  on an airframe  10 . (The pivot pin  44  pivots about a longitudinal axis  46 , which runs parallel to the longitudinal direction  21 .) The door  22  has a door panel  24  rigidly connected with an arm  30  such that the door panel  24  and arm  30  generally form a V-shape  40  as viewed in the longitudinal direction  21 . The landing gear door system  20  also includes a mechanism  50  configured to rotate the door  22  about the pivot pin  44  (in the direction indicated by arrow  112 ) between (i) a closed position  100 , in which an outer surface  27  of the door panel  24  is configured to provide aerodynamic continuity  102  with an outer aircraft skin  11  of the airframe  10 , and (ii) an open position  104 , in which the door  22  is rotated into the landing gear compartment  12  and an opening or aperture  106  is exposed. 
     The door  22  and/or door panel  24  may be configured such that, in the closed position  100 , the contour of the door panel&#39;s outer surface  27  generally matches the adjacent and surrounding contour of the outer aircraft skin  11 . In other words, with the door  22  disposed in the closed position  100 , the outer aircraft skin  11  and outer surface  27  together provide a substantially smooth, uninterrupted combined surface which minimizes air drag across this surface. On the other hand, when the door  22  is disposed in the open position  104 , an opening or aperture  106  is presented where the outer surface  27  was previously disposed. 
     The door panel  24  and arm  30  may be rigidly connected with each other at a vertex portion  42  of the door  22 , with the pivot pin  44  extending through the vertex portion  42 . The pivot pin  44  may be configured for rotatable connection with one of (i) the outer aircraft skin  11  and (ii) a mounting structure  14  within the landing gear compartment  12 . The door panel  24  may be configured to have an arcuate profile  28  as viewed in the longitudinal direction  21  so as to provide the abovementioned aerodynamic continuity  102  with the outer aircraft skin  11  in the closed position  100 . The arm  30  may have a curved or bent profile  36  as viewed in the longitudinal direction  21 , wherein the curved or bent profile  36  has an apex  38  which extends away from the door panel  24 . 
     The configurations shown in  FIGS. 1-3  show two generally V-shaped doors  22  disposed in a mirror image arrangement with respect to each other. (Note, however, that the landing gear door system  20  may include only one door  22 , rather than two.) Each door panel  24  includes opposed first and second edges  25 ,  26 , and each arm  30  includes opposed first and second arm ends  32 ,  34 , with the vertex portion  42  of each door  22  including the respective second edge  26  and first end  32 . With the two-door configuration shown in the drawings, the first edges  25  of the two doors  22  may meet, abut and/or seal against each other in the closed position  100  such that a smooth surface and aerodynamic continuity  102  are provided thereat. 
     The mechanism  50  may be configured for mounting within the landing gear compartment  12 . The mechanism  50  may include: (i) a connecting member  52  having opposed first and second connecting member ends  54 ,  56  with a connecting member length L 52  therebetween, wherein the first connecting member end  54  is pivotably connected to the arm  30 ; (ii) a linkage  60  having opposed first and second linkage ends  62 ,  64  with a linkage length L 60  therebetween, wherein the first linkage end  62  is pivotably connected to the second connecting member end  56 ; (iii) a lever  70  having opposed first and second lever ends  72 ,  74  and a fulcrum point  76  between the first and second lever ends  72 ,  74  (with a lever portion length L 78  between the second lever end  74  and the fulcrum point  76 ), wherein the first lever end  72  is pivotably connected to the second linkage end  64  and the fulcrum point  76  is configured for rotatable connection with a first mounting point  16  within the landing gear compartment  12 ; and (iv) an actuator  80  rotatably connected to the second lever end  74  and configured for selectively urging the second lever end  74  in a first direction  82  (e.g., downward) toward the opening  106  and in a second direction  84  (e.g., upward) away from the opening  106 . 
     The actuator  80  may include a contact portion  81  which rotatably connects with the second lever end  74 , and a drive portion  83  which selectively urges or drives the contact portion  81  in the first and second directions  82 ,  84 . For example, the actuator  80  may be a linear actuator configured to selectively drive the second lever end  74  downward and upward. The drive portion  83  may be fixedly disposed within the landing gear compartment  12 , while the contact portion  81  may be free to translate in the first and second directions  82 ,  84  (e.g., downward and upward). 
     At least one of the connecting member  52 , the linkage  60 , and a portion of the lever  70  between the fulcrum point  76  and the second lever end  74  may be configured to extend and retract in length. For example, the connecting member  52  may include a respective extending/retracting portion  58 , the linkage  60  may include a respective extending/retracting portion  68 , and/or the lever  70  (between the fulcrum point  76  and the second lever end  74 ) may include a respective extending/retracting portion  78 . Each of these extending/retracting portions  58 ,  68 ,  78  may assume various configurations, such as shocks, dampers and the like whose extension/retraction is constrained to act only along the length of the respective connecting member  52 , linkage  60  or lever  70 . 
     The landing gear door system  20  may further include a strut  90 ,  91  having a first strut end  92 , a second strut end  94 ,  96  opposed to the first strut end  92 , and a length L 90 , L 91  between the first strut end  92  and the second strut end  94 ,  96 . The first strut end  92  may be pivotably connected to the first linkage end  62  and the second connecting member end  56 , and the second strut end  94 ,  96  may be pivotably connected to one of (i) a second mounting point  18  within the landing gear compartment  12  and (ii) an alternative second mounting point  19  defined or carried by the outer aircraft skin  11  (e.g., on an interior or inboard surface of the outer aircraft skin  11 ). Note that  FIG. 1  illustrates both of these possible connection arrangements for the second strut end  94 ,  96 , utilizing a “short” strut  90  having a second strut end  94  shown on the left side of the drawing, and a “long” strut  91  having a second strut end  96  shown on the right side of the drawing. For example, the door  22  on the left side of the drawing has its second strut end  94  pivotably connected to a second mounting point  18  located within the landing gear compartment  12 , while the door  22  on the right side of the drawing has its second strut end  96  pivotably connected to an alternative second mounting point  19  defined or carried by the outer aircraft skin  11 . (The left side of the drawing also shows dashed lines representing the outline of a “long” strut  91 , if such a strut  91  were used there instead of the “short” strut  90 .) 
     Also note that like the connecting member  52 , the linkage  60 , and the portion of the lever  70  between the fulcrum point  76  and the second lever end  74 , the strut  90 ,  91  may be configured to extend and retract in length L 90 , L 91 , and the strut  90 ,  91  may include a strut extender  98  (which may also be referred to as a strut extending/retracting portion  98 ) configured for selectively urging or allowing the strut  90 ,  91  to extend and retract in length L 90 , L 91 . As used here in the phrase “urging or allowing”, “urging” means “actively acting or causing”, while “allowing” means “passively letting or allowing”. For example, a strut extender  98  may be configured so as to actively urge or cause the strut  90 ,  91  to selectively extend and retract in length L 90 , L 91 , such as by electrical, pneumatic, mechanical, magnetorheological or other actuation. (Note that such means of actuation are not illustrated in the drawings.) Or, the strut extender  98  may assume the form of a shock absorber, damper, telescoping arrangement, or the like which passively allows the strut  90 ,  91  to be extended and retracted in length L 90 , L 91 , such as by the action of forces from the first linkage end  62  and the second connecting member end  56 , which are pivotably attached to the first strut end  92 . 
     The first lever end  72  and the second linkage end  64  may define a first joint J 1  therebetween, the first linkage end  62  and the second connecting member end  56  may define a second joint J 2  therebetween, the first connecting member end  54  and the arm  30  may define a third joint J 3  therebetween, and the second lever end  74  and the contact portion  81  of the actuator  80  may define a fourth joint J 4 . As illustrated in  FIG. 3 , the landing gear door system  20  may be configured such that when the first and second joints J 1 , J 2  and the pivot pin  44  are disposed along a substantially straight line  110 , the third joint J 3  is disposed outboard of (i.e., in an outboard direction  88  from) the substantially straight line  110 . 
     In operation, the landing gear door system  20  may be disposed in the closed position  100  ( FIG. 1 ) after the aircraft  15  has lifted off of the runway and the landing gear  13  has been retracted into the landing gear compartment  12 . The landing gear door system  20  will typically remain in the closed position  102  during normal flight, so that the smooth outer aircraft skin  11  and outer surface  27  together provide aerodynamic continuity  102  and low drag. Then, just prior to landing, the landing gear door system  20  may be disposed in the open position  100  ( FIG. 2 ) so that the landing gear  13  may be extended through the opening  106  for landing. The landing gear door system  20  may remain in the open position  100  during landing and taxiing, and indeed until the aircraft  15  takes off again. Note that each time the landing gear door system  20  transitions between the closed and open positions  100 ,  104 , it also passes through a series of intermediate positions  108  (one example of which is shown in  FIG. 3 ). 
     In order to cycle the landing gear door system  20  among the closed, intermediate and open positions  100 ,  108 ,  104 , the actuator  80  may be selectively actuated to cause the contact portion  81  to move in the first and second directions  82 ,  84  (e.g., downward and upward) in a manner that causes the door  22  to rotate about its pivot pin  44 . This rotation of the door  22  is effected by converting the linear motion of the actuator  80  into rotational motion of the door  22 , via the series of fixed and movable connections between and among the actuator  80 , the lever  70 , the first mounting point  16 , the linkage  60 , the connecting member  52 , the door  22  and the pivot pin  44  (plus, optionally, the strut  90 ,  91  and second mounting point  18 ,  19  as well). 
     For example,  FIGS. 4A-L  show a series of schematic representations of how the various elements of the mechanism  50  act together to convert the linear motion of the actuator  80  into the rotational motion of the door(s)  22 . Note that not all of the structure illustrated in  FIGS. 1-3  is shown in  FIGS. 4A-L , in order to simplify the drawings and make it easier to see the sequence of movements from one drawing to the next. Also, for the sake of simplicity and illustration, only the left side of the structure of  FIGS. 1-3  is illustrated. Here in  FIGS. 4A-L , filled-in circles represent connection points that are rotatably fixed (i.e., at  19 ,  44  and  76 ), and open circles represent connection points that are not fixed (i.e., at J 1 , J 2 , J 3  and J 4 ). Also note that while no extending/retracting portions  58 ,  68 ,  78 ,  98  are shown in  FIGS. 4A-L , these elements may optionally be included. Further, note that some elements are labeled with reference numerals in  FIG. 4A  (e.g., the arm  30 , the connecting member  52 , the linkage  60 , the lever  70 , the strut  91 , and various ends thereof  54 ,  56 ,  62 ,  64 ,  72 ,  74 ), but these reference numerals are not repeated throughout  FIGS. 4B-L . 
     In  FIG. 4A , the landing gear door system  20  is in the closed position  100  and the actuator  80  is not causing any motion. In  FIG. 4B  the actuator  80  just begins to actuate the contact portion  81  downward (as indicated by the downward-pointing arrow), and in  FIG. 4C  the contact portion  81  has begun pushing downward on the fourth joint J 4 . Pressing downward on the fourth joint J 4  causes the first joint J 1  to rotate upward about the fixed fulcrum point  76 ; likewise, the upward motion of the first joint J 1  causes the second joint J 2  to also move upward, and causes the third joint J 3  to rotate counter-clockwise about the fixed pivot pin  44 .  FIG. 4D  shows the actuator  80  urging further downward motion of the fourth joint J 4 , which causes further upward motion of the first and second joints J 1 , J 2  and further counter-clockwise rotation of the third joint J 3  about the pivot pin  44 . In the arrangement shown in  FIG. 4D , the overall length of the elements between the first joint J 1  and the pivot pin  44  reaches a maximum, and at that point the actuator  80  ceases its downward urging of the fourth joint J 4 . At this point, the counter-clockwise rotational momentum of the third joint J 3  (and the door  22 ) serves to continue carrying the third joint J 3  (and the door  22 ) in further counter-clockwise rotation about the pivot pin  44 , and the actuator  80  then switches from downward urging of the fourth joint J 4  to upward urging. 
     Next,  FIG. 4E  shows the conflux of three more-or-less simultaneous actions: (i) the continued counter-clockwise motion of the third joint J 3  (and the door  22 ); (ii) the upward urging of the actuator  80  upon the fourth joint J 4  (which also causes the first joint J 1  to be rotated downward); and (iii) the rightward force exerted by the optional strut  90 ,  91  upon the second joint J 2 . This combination of actions promotes further counter-clockwise movement of the third joint J 3  (and door  22 ). Also note that the third joint J 3  is disposed outboard of the substantially straight line  110  (as similarly shown in  FIG. 3 ), which also encourages the further counter-clockwise movement of the third joint J 3  (and door  22 ).  FIG. 4F  illustrates the result of the continued actions and motions of  FIG. 4E , with the door  22  now being sufficiently rotated and the opening  106  being fully presented.  FIG. 4G  shows the actuator  80  ceasing its upward urging, and the landing gear door system  20  being fully in the open position  104 . In this position, the landing gear  13  (not shown) may be extended for landing. 
     After takeoff, the landing gear  13  may be retracted, and the landing gear door system  20  may move from the open position  104  to the closed position  100 .  FIG. 411  shows the initiation of this sequence, with the actuator  80  once again urging the fourth joint J 4  downward, which causes an upward motion of the first and second joints J 1 , J 2  and a clockwise rotation of the third joint J 3  (and door  22 ) about the pivot pin  44 .  FIG. 41  illustrates further downward urging by the actuator  80 , which causes continued clockwise rotation of the third joint J 3  (and door  22 ). (Note that the arrangement of elements in  FIG. 41  is somewhat analogous to the arrangement shown earlier in  FIG. 4D .) Then, in  FIG. 4J , the actuator  80  ceases its downward urging of the fourth joint J 4  and begins an upward urging of the fourth joint J 4  (as indicated by the upward-pointing arrow). In  FIG. 4K , the actuator  80  continues its upward urging of the fourth joint J 4  until the third joint J 3  has move clockwise enough to move the door  22  into the closed position  100 , at which point the actuator  80  ceases its upward urging of the fourth joint J 4  as shown in  FIG. 4L . Note that in some instances when the actuator  80  is not urging the fourth joint J 4  upward or downward (as in  FIGS. 4A, 4G and 4L ), the drive portion  83  may act to “lock” the contact portion  81  into its current position, thus keeping the door  22  open (as in  FIG. 4G ) or closed (as in  FIGS. 4A and 4L ). 
     According to another embodiment, a nose landing gear door system  20  for a nose landing gear compartment  12  includes: a door  22  pivotable about a pivot pin  44  configured for disposition in a longitudinal direction  21  on an airframe  10 , the door  22  having a door panel  24  rigidly connected with an arm  30  such that the door panel  24  and arm  30  generally form a V-shape  40  as viewed in the longitudinal direction  21 ; and a mechanism  50  configured for mounting within the nose landing gear compartment  12  and configured to rotate the door  22  about the pivot pin  44  between a closed position  100 , in which an outer surface  27  of the door panel  24  is configured to provide aerodynamic continuity  102  with an outer aircraft skin  11  of the airframe  10 , and an open position  104 , in which the door  22  is rotated into the nose landing gear compartment  12  and an opening  106  is exposed. The mechanism  50  includes: a connecting member  52  having opposed first and second connecting member ends  54 ,  56 , wherein the first connecting member end  54  is pivotably connected to the arm  30 ; a linkage  60  having opposed first and second linkage ends  62 ,  64 , wherein the first linkage end  62  is pivotably connected to the second connecting member end  56 ; a lever  70  having opposed first and second lever ends  72 ,  74  and a fulcrum point  76  between the first and second lever ends  72 ,  74 , wherein the first lever end  72  is pivotably connected to the second linkage end  64  and the fulcrum point  76  is configured for rotatable connection with a first mounting point  16  within the nose landing gear compartment  12 ; and an actuator  80  rotatably connected to the second lever end  74  and configured for selectively urging the second lever end  74  in a first direction  82  toward the opening  106  and in a second direction  84  away from the opening  106 . 
     At least one of the connecting member  52 , the linkage  60 , and a portion of the lever  70  between the fulcrum point  76  and the second lever end  74  may be configured to extend and retract in length L 52 , L 60 , L 78 . The nose landing gear door system  20  may further include a strut  90 ,  91  having opposed first and second strut ends  92 ,  94 ,  96 , wherein the first strut end  92  is pivotably connected to the first linkage end  62  and the second connecting member end  56 , and the second strut end  94 ,  96  is pivotably connected to one of (i) a second mounting point  18  within the nose landing gear compartment  12  and (ii) the outer aircraft skin  11 ,  19 . The strut  90 ,  91  may include a strut extender or extending/retracting portion  98  configured for selectively urging or allowing the strut  90 ,  91  to extend and retract in length L 90 , L 91 . The first lever end  72  and the second linkage end  64  may define a first joint J 1  therebetween, the first linkage end  62  and the second connecting member end  56  may define a second joint J 2  therebetween, and the first connecting member end  54  and the arm  30  may define a third joint J 3  therebetween, wherein when the first and second joints J 1 , J 2  and the pivot pin  44  are disposed along a substantially straight line  110 , the third joint J 3  is disposed outboard of the substantially straight line  110 . 
     According to yet another embodiment, a nose landing gear door system  20  for an aircraft  15  includes: (a) an airframe  10  having a nose landing gear compartment  12  surrounded by an outer aircraft skin  11 ; (b) a door  22  pivotable about a pivot pin  44  disposed in a longitudinal direction  21  on the airframe  10 , the door  22  having a door panel  24  rigidly connected with an arm  30  such that the door panel  24  and arm  30  generally form a V-shape  40  as viewed in the longitudinal direction  21 ; and (c) a mechanism  50  mounted within the nose landing gear compartment  12  and configured to rotate the door  22  about the pivot pin  44  between a closed position  100 , in which an outer surface  27  of the door panel  24  is configured to provide aerodynamic continuity  102  with the outer aircraft skin  11  of the airframe  10 , and an open position  104 , in which the door  22  is rotated into the nose landing gear compartment  12  and an opening  106  is exposed. In this embodiment, the mechanism  50  includes: (i) a connecting member  52  having opposed first and second connecting member ends  54 ,  56 , wherein the first connecting member end  54  is pivotably connected to the arm  30 ; (ii) a linkage  60  having opposed first and second linkage ends  62 ,  64 , wherein the first linkage end  62  is pivotably connected to the second connecting member end  56 ; (iii) a lever  70  having opposed first and second lever ends  72 ,  74  and a fulcrum point  76  between the first and second lever ends  72 ,  74 , wherein the first lever end  72  is pivotably connected to the second linkage end  64  and the fulcrum point  76  is rotatably connected with a first mounting point  16  within the nose landing gear compartment  12 ; and (iv) an actuator  80  rotatably connected to the second lever end  74  and configured for selectively urging the second lever end  74  in a first direction  82  toward the opening  106  and in a second direction  84  away from the opening  106 . 
     In this embodiment, the nose landing gear door system  20  may further include a strut  90 ,  91  having opposed first and second strut ends  92 ,  94 ,  96 , wherein the first strut end  92  is pivotably connected to the first linkage end  62  and the second connecting member end  56 , and the second strut end  94 ,  96  is pivotably connected to one of a second mounting point  18  within the nose landing gear compartment  12  and the outer aircraft skin  11 ,  19 . Also in this embodiment, the first lever end  72  and the second linkage end  64  may define a first joint J 1  therebetween, the first linkage end  62  and the second connecting member end  56  may define a second joint J 2  therebetween, and the first connecting member end  54  and the arm  30  may define a third joint J 3  therebetween, wherein when the first and second joints J 1 , J 2  and the pivot pin  44  are disposed along a substantially straight line  110 , the third joint J 3  is disposed outboard of the substantially straight line  100 . 
     Note that in some configurations of the landing gear door system  20 , the orientation and/or positioning of the linkage  60  and the lever  70  (and possibly of the strut  90 ,  91  as well) may be generally the same for the closed and open positions  100 ,  104 , as may be seen by comparing  FIGS. 4A-B  and  4 K-L (showing the closed position  100 ) with  FIGS. 4F-G  (showing the open position  104 ). 
     The above description is intended to be illustrative, and not restrictive. While the dimensions and types of materials described herein are intended to be illustrative, they are by no means limiting and are exemplary embodiments. In the following claims, use of the terms “first”, “second”, “top”, “bottom”, etc. are used merely as labels, and are not intended to impose numerical or positional requirements on their objects. As used herein, an element or step recited in the singular and preceded by the word “a” or “an” should be understood as not excluding plural of such elements or steps, unless such exclusion is explicitly stated. Additionally, the phrase “at least one of A and B” and the phrase “A and/or B” should each be understood to mean “only A, only B, or both A and B”. Moreover, unless explicitly stated to the contrary, embodiments “comprising” or “having” an element or a plurality of elements having a particular property may include additional such elements not having that property. And when broadly descriptive adverbs such as “substantially” and “generally” are used herein to modify an adjective, these adverbs mean “for the most part”, “to a significant extent” and/or “to a large degree”, and do not necessarily mean “perfectly”, “completely”, “strictly” or “entirely”. Additionally, the word “proximate” may be used herein to describe the location of an object or portion thereof with respect to another object or portion thereof, and/or to describe the positional relationship of two objects or their respective portions thereof with respect to each other, and may mean “near”, “adjacent”, “close to”, “close by”, “at” or the like. 
     This written description uses examples, including the best mode, to enable those skilled in the art to make and use devices, systems and compositions of matter, and to perform methods, according to this disclosure. It is the following claims, including equivalents, which define the scope of the present disclosure.