Patent Publication Number: US-2023150645-A1

Title: Door assembly

Description:
The present disclosure relates to a door assembly. In particular, the disclosure relates to a door assembly for a payload bay. 
     BACKGROUND 
     Hinge-mounted doors are well known. Hinges, normally located on an edge of the door, provide an articulated join between the door and the structure to which the door is attached. Any force generated by the weight of the door, or imparted to the door, is transmitted to the structure via the hinge. 
     If it is required for the door to be automated, then an actuator must be coupled to the door in some way. This may be via a lever mechanism, which acts on the door. Alternatively, the hinges may be at the edge of the door arms, which swing the door from a closed to an open position. Since doors often need to be opened fully to allow maximum access through an opening they cover, mechanisms of the prior art must be able to open the door to at least ninety degrees from a closed position. Such an example, U.S. Pat. No. 6,536,711B1 (Lockheed Martin), is illustrated in  FIG.  1   . Here, an internal payload bay  1010  for an aircraft includes a pair of doors  4   a ,  4   b . The bay  1010  may contain a payload  1062 . The doors  4   a ,  4   b  are arranged to open outwardly away from the aircraft. Each door  4   a ,  4   b  is connected by at least one hinge  3   a ,  3   b  to a structural member  1014  of the aircraft, such as the fuselage. 
     However, such a door assembly is complicated and, because the hinge  3   a ,  3   b  is attached to one edge of the door  4   a ,  4   b , several hinges  3   a ,  3   b  may be required to support the weight of the door  4   a ,  4   b  and any other forces imparted to the door  4   a ,  4   b . Hence deformation or fatigue of the hinge  3   a ,  3   b  may occur. 
     On applications such as aircraft, the extent to which the door  4   a ,  4   b  opens may cause further problems, for example when the aircraft is on the ground. In the example illustrated in  FIG.  1   , the payload bay  1010  is arranged on the underside of an aircraft such that doors  4   a ,  4   b  open downwards. When a door  4   a ,  4   b  is fully open, the extent to which the free edge of the door  4   a ,  4   b  extends away from the airframe reduces ground clearance and provides an obstruction to access to the cavity within the payload bay  1010 . 
     The doors  4   a ,  4   b  also act to increase wind resistance when the aircraft is in flight, which reduces fuel efficiency and increases actuation loads. 
     Large exposed doors  4   a ,  4   b  can have a negative impact on aircraft lateral stability, often requiring the aircraft&#39;s vertical fin area to be increased or other mechanisms to compensate, resulting in additional weight. 
     Hence a door assembly, which is operable to open and close but reduces the extent to which the door extends away from the structure to which it is attached, is highly desirable. 
     SUMMARY 
     According to a first aspect, there is provided a door assembly for a payload bay having an opening, the door assembly comprising at least one door, the at least one door comprising: 
     a panel section having a first end and a second end; and 
     a first mounting member arranged orthogonally to the panel section at the first end and having a first engagement feature having a rotational axis about which the panel section is arranged to rotate, the engagement feature being arranged to engage with a first fixing member on one side of the payload bay to rotatably couple the panel section to the payload bay, 
     wherein the at least one door is arranged to translate between a closed configuration, in which the panel section is arranged in the same plane as the opening, and an open configuration, in which the panel section is arranged at at least 90 degrees to the plane of the opening, by rotating about the rotational axis, and 
     wherein the panel section is arranged parallel to and offset from the rotational axis, such that an inner surface of the panel section faces the rotational axis. 
     The door assembly may comprise a second mounting member disposed opposite the first mounting member, the second mounting member comprising a second engagement feature arranged co-axially with the rotational axis. The second mounting member may be arranged to engage with a second fixing member on the opposite side the payload bay, and the first engagement feature and second engagement feature may be arranged to permit the panel section to rotate about the rotational axis. 
     The panel section may comprise a free edge extending between the first end of the panel section and the second end of the panel section and a fixing edge parallel to and opposite the free edge, the door comprising a reinforcement member extending from the fixing edge. 
     The extent of the reinforcement member in the horizontal plane may be less than the extent of the panel section in the vertical plane when the door is in the open configuration. In other words, the panel section may be deeper than the reinforcement member. 
     The reinforcement member may comprise mounting means for coupling a payload to the at least one door. The mounting means may be at least one of a recess or pylon. In other words, the door assembly may be a payload carriage. 
     The reinforcement member may comprise a planar portion arranged at about 90 degrees to the panel section. The reinforcement member may comprise an arcuate portion having one edge coupled to the fixing edge. The planar portion may comprise the payload mounting means. 
     The, or each, mounting member may be coupled to the panel section and/or the reinforcement member. 
     The first engagement feature may comprise an aperture for receiving the first fixing member. Alternatively, the first engagement feature may comprise a protrusion for fitting into an aperture of the first fixing member. The first engagement feature and first fixing member may be arranged to engage with each other by a friction fitting or interlocking teeth. Alternatively, the first engagement feature may be arranged to freely rotate relative to the first fixing member. 
     The door assembly may comprise the first fixing member and a first actuator for driving the first fixing member to rotate the first engagement feature, such that the panel section is rotatable with, and driveable by, the first rotatable fixing member about the rotational axis. 
     The door assembly may comprise the second fixing member and a second actuator for driving the second fixing member to rotate the second engagement feature, such that the panel section is rotatable with, and driveable by, the second rotatable fixing member about the rotational axis. 
     The door assembly may comprise a first door and a second door, arranged such that, when both the first door and second door are in the closed configuration: 
     the free edges of each panel section face each other; and 
     the first door and second door cover substantially the whole of the opening. 
     According to a second aspect of the present invention, there is provided a payload bay comprising a support structure and a door assembly according to the first aspect, wherein the support structure defines an opening providing access to/from a cavity within the payload bay. The mounting member of the at least one door is located inside the cavity such that the rotational axis is offset from the plane of the opening. The support structure, specifically a ceiling thereof, may comprise one or more payload mounting means. 
     In the open configuration, the panel section of the at least one door may only partly extend out of the cavity, the remainder of the at least one door being located in the cavity. 
     According to a third aspect of the present invention, there is provided an aircraft comprising a payload bay according to the second aspect, the payload bay being arranged such that the outer surface of the panel section forms part of an outer surface of the aircraft when the at least one door is in the closed configuration. 
     Hence, there may be provided a door assembly, a payload bay comprising a door assembly of the present disclosure, and an aircraft comprising a payload bay of the present disclosure. The door assembly provides a more space-efficient door assembly compared to examples of the related art, and reduces the surface area of door extended into the airflow when the door is open. It also provides a means of mounting an automated door with a more robust mounting mechanism than that provided by the related art. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Examples of the present disclosure will now be described with reference to the accompanying drawings, in which: 
         FIG.  1    shows a payload bay having a door assembly according to the prior art; 
         FIG.  2    shows a perspective view of an aircraft having a payload bay according to the present disclosure; 
         FIGS.  3   a  and  3   b    show cross-section views of a payload bay of the present disclosure having a door assembly in respectively an open configuration and a closed configuration; 
         FIGS.  4   a  to  4   e    show a perspective view of the opening sequence of the door assembly of the payload bay shown in  FIGS.  3   a    and  3   b;    
         FIG.  5    shows a perspective view of the payload bay having the door assembly in the open configuration; 
         FIGS.  6   a  and  6   b    show cross-section views of a payload bay of the present disclosure having a door assembly in respectively the closed configuration and the open configuration; and 
         FIG.  6   c    shows a plan view the payload bay illustrated in  FIG.  6     b.    
     
    
    
     DETAILED DESCRIPTION 
     Generally, the present disclosure relates to a door assembly for use in covering and uncovering a cavity, recess, compartment or the like, preferably in an aircraft. The door assembly includes one or more doors, along with associated actuation means. One or more payloads may be stored on the inside surface of the door. The door assembly may be used to cover and provide access to mechanisms in a payload bay for maintenance reasons, or the like, or so that a payload can be deployed. The doors are arranged to open and close by rotating about an axis of rotation offset from a panel section of each door, such that when the door is open very little of the panel section extends outside of the payload bay, and when the door is closed the panel section is co-planar with an outer surface of the vehicle or structure in which it is installed. When incorporated into an aircraft, the door therefore becomes part of the aircraft&#39;s outer skin when closed. 
     An aircraft  1  having a payload bay  10  is illustrated in  FIG.  2   . The payload bay  10  may instead be provided as part of a land or sea-going vehicle, or a different type of air vehicle. The payload bay  10  may also be provided as part of a static building or structure. For example, the payload bay  10  could be used to house a lifeboat for a ship internally, landing gear in an aircraft, or cargo in a spacecraft. The payload bay  10 , described in more detail with relation to  FIGS.  3   a  to  6   c   , comprises at least one door  20 ,  220  which is operable to open and close. The payload bay  10  of the present disclosure has particular efficacy when incorporated as part of an aircraft  1 , as here minimising air resistance when deploying payloads is highly desirable. The aircraft  1  may be a transport aircraft, fighter jet, commercial airliner, helicopter or airship, for example. The payload bay  10  in the illustrated embodiment is installed in a ventral part of the fuselage of the aircraft  1 . However, the payload bay  10  may alternatively be installed in a side or dorsal part of the fuselage. The payload bay  10  may also be installed in the wings of the aircraft  1 , or may define an external pod for coupling to the aircraft  1 . The aircraft  1  may be provided with more than one payload bay  10 , depending on mission requirements. 
     The payload bay  10  illustrated in  FIG.  2   , and throughout the present disclosure, comprises two doors, disposed opposite each other such that the payload bay  10  is only fully open when both doors are in their fully open configuration. However, it would be appreciated by the skilled person that one single door may be used to fully close or open the opening, depending on the payload bay&#39;s depth and width. Each or the door may also be divided along its length to provide a plurality of doors along the longitudinal axis of the payload bay  10 . When a door of the payload bay  10  is closed, that outer surface of the closed door forms part of the outer skin of the aircraft  1 . 
     The payload bay  10 , specifically a door assembly installed therein, will now be described with reference to  FIGS.  3   a  to  6   c   . In the example of  FIGS.  3   a    to  5 , the payload bay  10  is shown empty.  FIGS.  3   a  and  3   b    show a payload bay having a slightly different door shape than that of  FIGS.  4   a    to  5 , although its method of operation is the same.  FIGS.  6   a  to  6   c    show a similar example of the payload bay  10  illustrated in  FIGS.  4   a    to  5 , but here the payload bay  10  is provided with example payloads  62 . Given the similarities of all of the examples, the same reference numerals have been used to reference like features. 
     Turning to  FIGS.  3   a  and  3   b   , a payload bay  10  is illustrated in cross section. The payload bay  10  comprises a first door  20  and second door  220 . In  FIG.  3   a   , the doors  20 ,  220  of the payload bay  10  are shown in an open configuration (in this example, the fully open configuration, or fully open state). In  FIG.  3   b   , the doors  20 ,  220  of the payload bay  10  are shown in a closed configuration (or closed state). As illustrated in  FIGS.  4   b  to  4   e   , the doors  20 ,  220  translate (or transition) through partially open configurations between the closed configuration and fully open configuration. In partially open configurations, the opening  12  (or relevant region  70 ,  270  thereof) is not open to its full extent. 
     The payload bay  10  comprises a support structure  14  having an opening  12  through which its internal cavity  60  can be accessed. In the examples shown, the opening  12  is substantially rectangular; however, it would be appreciated that the opening  12  could be circular, for example, and the doors  20 ,  220  shaped accordingly. The support structure  14  is substantially cuboid in form. The payload bay  10  as illustrated is self-contained such that it can be retrofitted into or onto existing aircraft  1 . Here, the support structure  14  is a housing or framework (i.e. arrangement of struts) that is independent from the aircraft  1  structure. Alternatively, the payload bay  10  may be integrated with the aircraft  1  such that the aircraft  1  structure itself forms the support structure  14 . The side of the support structure  14  having the opening  12  faces the outside of the aircraft  1 . This side of the support structure  14  forms part of the aircraft&#39;s skin. 
     The payload bay  10  may comprise a single door  20 . In such an example, in the closed configuration, the door  20  covers substantially the whole of the opening  12 . 
     Alternatively, as shown in the Figures, the payload bay  10  may comprise a second door  220  that faces the first door  20  across the payload bay  10 . The first door  20  and second door  220  are mirror images of each other. The second door  220  is of the same form and configuration as the first door  20 , with the same features. Hence, the doors  20 ,  200  are both rotary doors. The first door  20  is provided to cover a first region  70  of the opening  12 , and the second door  220  is provided to cover a second region  270  of the opening  12 . The first region  70  and second region  270  are illustrated in  FIG.  3   a   . In the closed configuration the doors  20 ,  220  co-operate to cover the whole of the opening  12 . While the first region  70  and second region  270  are shown of being approximately equal surface areas, it would be appreciated that in some embodiments one section, and hence one door  20 ,  220 , may be larger than the other. 
     Each door  20 ,  220  comprises a panel section  22 ,  222 . The panel section  22 ,  222  of each door  20 ,  220  may be planar (that is to say, flat). In the illustrated embodiment, a mounting member  30 ,  230  (shown in  FIGS.  4   a  to  6   c   ) is coupled to the panel section  22 ,  220  at right angles to the plane of the panel section  22 ,  220 . The mounting member  30 ,  230  is for mounting the door  20 ,  220  to the inside of the support structure  14 . The mounting member  30 ,  230  includes an engagement feature  31 ,  231 . The engagement feature  31 ,  231  in the illustrated embodiment is an aperture for receiving a fixing member  16 ,  216  in the form of a protrusion. In alternative embodiments, the engagement feature  31 ,  231  is a protrusion arranged to be received by a fixing member  16 ,  216  in the form of an aperture. As illustrated in  FIG.  5   , the fixing member  16 ,  216  is arranged to protrude from the inside of a wall (or strut) of the support structure  14  into the cavity  60 , such that when engaged with the engagement feature  31 ,  231  the door  20 ,  220  is permitted to rotate relative to the wall (or strut) of the support structure  14 . The door  20 ,  220  is operable to rotate about the rotational axis  18 ,  218  passing through the centre of the respective engagement feature  31 ,  231  (i.e. the rotation axis of an engagement feature is its central axis, or the axis passing orthogonal to its plane and through the centre). 
     The panel section  22 ,  222  has as a fixing edge  50 ,  250  and a free edge  51 ,  251 . The free edge  51 ,  251  as illustrated in the Figures is tapered, however in other embodiments the edge may be squared off or rounded. The panel section  22 ,  222  is arranged in the same plane as the opening  12  when in the closed configuration ( FIG.  3   b   ). In other words, the outside surface of the panel section  22 ,  222  is co-planar with an outside plane of the support structure  14 . The free edge  51 ,  251  is extended out of the plane of the opening into the atmosphere outside the aircraft  1 , when the door  20 ,  220  is in an open configuration (e.g. fully open). When the first door  20  and second door  220  are in the closed configuration, the free edges  51 ,  251  are disposed opposite and parallel to each other. The fixing edge  50 ,  250  is disposed on the side of the panel section  22 ,  222  opposite the respective free edge  51 ,  251 . 
     In the illustrated embodiments, a reinforcement member  52 ,  252  is coupled to the fixing edge  50 ,  250 . The reinforcement member  52 ,  252  tends to provide additional surface area for coupling the mounting member  30 ,  230  to the door  20 ,  220 , increasing the mechanical strength of the door  20 ,  220 . The mounting member  30 ,  230  may be coupled to the inside surface of the panel section  22 ,  222 , reinforcement member  52 ,  252  or both. The panel section  22 ,  222  and reinforcement member  52 ,  252  together form approximately an “L” shape (when viewed in longitudinal cross-section). In a preferred embodiment, the intersection of the orthogonal portions of the “L” is curved. The “L” shape tends to provide strength to the door  20 ,  220 . 
     Further, the reinforcement member  52 ,  252  may provide coupling means for attaching a payload (item  62  in  FIG.  6   c   ) to the door  22 ,  220 . The coupling means in the illustrated embodiment takes the form of a bracket  56 ,  256  (or pylon). In alternative embodiments, such as illustrated in  FIG.  5   , the coupling means takes the form of a recess to house a suitable release unit. The coupling means is arranged to face the opening  12  when the door  20 ,  220  is in the fully open configuration. The reinforcement member  52 ,  252  may be provided with numerous forms of coupling means in the same embodiment. The coupling means may provide electrical, hydraulic or pneumatic communication to the payload  62  from the aircraft  1 . In other words, the door  20 ,  220  may function as a payload carriage. 
     In the embodiment illustrated in  FIGS.  3   a  and  3   b   , the reinforcement member  252  comprises a planar portion  54 ,  254  and an arcuate portion  53 ,  253 . The arcuate portion  53 ,  253  is coupled to the fixing edge  50 ,  250  and curves inwards, towards the centre of the cavity  60  such that the plane of the planar portion  54 ,  254 , coupled to the free edge of the arcuate portion  53 ,  253  lies at approximate 90 degrees to the plane of the panel section  22 ,  222 . Instead of an arcuate portion  53 ,  253 , the planar portion  54 ,  254  may be directly coupled to the fixing edge  50 ,  250 . Alternatively to the arcuate portion  53 ,  253 , the planar portion  54 ,  254  may be coupled to the fixing edge  50 ,  250  by one or more further planar portions arranged at oblique angles to the planar portion  54 ,  254  and the panel section  22 ,  222 . 
     The width of the planar portion  54 ,  254  is less than the width of the panel section  22 ,  222 . In other words, if the panel section  22 ,  222  and planar portion  54 ,  254  were overlaid, the flat portion  54 ,  254  would be shorter than the panel section  22 ,  222 . This tends to reduce the volume occupied by the door  20 ,  220  within the cavity  60 , enabling smaller payload bays  10  for a given size of payload  62 . 
     The doors  20 ,  220  are operable to rotate through at least 90 degrees about their rotational axes  18 ,  218  in order to expose the opening  12  to its greatest extent (shown in  FIG.  3   a   ). In the illustrated embodiment, the doors  20 ,  220  rotate through about 100 degrees about their rotational axes  18 ,  218 . As can be seen, the planar portion  54 ,  254  of the reinforcement member  52 ,  252  moves from being parallel to one side of the cavity  60  to move to a position in the fully open configuration in which it is substantially parallel with the ceiling  64  of the cavity  60 . This enables a payload  62  coupled thereto to be released into the airflow outside the aircraft  1  without being obstructed by any feature of the door assembly. 
     While the panel section  22 ,  222  illustrated in the Figures is longer than it is wide, with its longitudinal axis being parallel with the rotational axis  18 ,  218  of the door  20 ,  220 , it would be appreciated that in other embodiments the panel section  22 ,  222  may be relatively short in the direction of the rotational axis  18 ,  218 . 
     As shown in  FIG.  3   a   , the panel section  22 ,  222  of an open door  20 ,  220  only partly extends out of the opening  12 , with the remainder of the panel section  22 ,  222  of the open door  20 ,  220  being located inside the cavity  60 . 
       FIGS.  4   a  to  4   e    show a payload bay  10  opening sequence, while the payload bay  10  is empty. That is to say, a payload bay  10  is illustrated having first and second doors  20 ,  220  for covering an opening  12 . In  FIG.  4   a   , both doors  20 ,  220  are closed.  FIGS.  4   b  to  4   e    show the first door  20  in a fully open configuration while the second door  220  rotates about its rotational axis  218  until in  FIG.  4   e    both doors  20 ,  220  are in the fully open configuration. The first door  20  rotates anticlockwise about the rotational axis  18  of the engagement feature  31  to move to the fully open configuration, while the second door  220  rotates clockwise about the rotational axis  218  of the respective engagement feature  231  to move to the fully open configuration. It would be understood that it is not necessary to open both doors  20 ,  220  simultaneously, and in fact only one of the doors  20 ,  220  may open depending on the access to, or egress from, the cavity  60  that is required (as illustrated in  FIG.  4   b   , for example). 
     In the illustrated embodiment, a recess  80  is used as a coupling means for coupling a payload  62  to the reinforcement member  252 . The coupling means is disposed partway along the length of the reinforcement member  252 . 
     The panel section  22 ,  222  extends along the length L of the opening  12 . The panel section has a first end  24 ,  224  and a second end  26 ,  226  disposed opposite each other. As illustrated in  FIG.  5   , the fixing edge  50 ,  250  extends along the length L of the panel section  22 ,  222  from the first end  24 ,  224  to the second end  26 ,  226 . The reinforcement member  52 ,  252  also extends along the full length L of the panel section  22 ,  222 . However, in other embodiments, the reinforcement member  52 ,  252  may be bifurcated or extend only partway along the length L of the panel section  22 ,  222 . 
     The panel section  22  of the first door  20  is offset from its rotational axis  18  along its length L, and extends in the same direction as the first rotational axis  18  along its length between the ends  24 ,  26 . Likewise, the panel section  222  of the second door  220  is offset from its rotational axis  218  along its length L, and extends in the same direction as the rotational axis  218  along its length between the ends  224 ,  226 . That is to say, the panel section  22 ,  222  of each door  20 ,  220  does not intersect with its respective rotational axis  18 ,  218  at any point along its length L. 
     In some examples, for example where the panel sections  22 ,  222  are planar, the panel section  22 ,  222  is offset from (i.e. spaced apart from), and parallel with, its respective rotational axis  18 ,  218  along the length L of the panel section  22 ,  222 . In some examples, for example where the inner and/or outer surface of the panel sections  22 ,  222  are planar, the respective surface of the panel section  22 ,  222  is offset from (i.e. spaced apart from), and parallel with, its respective rotational axis  18 ,  218  along the length L of the panel section  22 ,  222 . 
     In embodiment illustrated in  FIG.  5   , the mounting member  30 ,  230  and the fixing member  16 ,  216  are coupled such that the door  20 ,  220  is rotatable with, and driveable by, the fixing member  16 ,  216  about the rotational axis  18 ,  218  to rotate the panel section  22 ,  222  about the rotational axis  18 ,  218 . Hence, the respective fixing members  16 ,  216  are spaced apart from one another across the width of the payload bay  10 . The fixing member  16 ,  216 , therefore, is coupled to an actuator  32 ,  232  (i.e. a motor). In other words, the fixing member  16 ,  216  is a drivable shaft. The first door  20  and second door  220  are controllable to open and close individually as each fixing member  16 ,  216  is coupled to an independent actuator  32 ,  232 . The actuators  32 ,  232  may be controllable by a pilot-operable switch in the cockpit or a ground station where the aircraft  1  is an unmanned aerial vehicle. 
     The actuators  32 ,  232  are shown disposed outside the support structure  14 , with the fixing members  16 ,  216  passing through the walls (or struts) of the support structure  14  to enable the doors  20 ,  220  to rotate relative to the support structure  14 . The actuators  32 ,  232  therefore may be disposed in the body of the aircraft  1 . Alternatively, the payload bay  10  may comprise another housing (not shown) encompassing both the support structure  14  and the actuators  32 ,  232 . In other embodiments, the actuators  32 ,  232  are coupled to the inside of a wall (or strut) of the support structure  14 , within the cavity  60 . 
     Instead of each door  20 ,  220  having independent actuators  32 ,  232  that enable each door  20 ,  220  to be opened and closed independently at different speeds, each of the fixing members  16 ,  216  may be coupled, for example by some gearing means, to the same actuator  32 ,  232  such that the doors  20 ,  220  open and close at the same time and speed. 
     It would be appreciated by the skilled person that other means for controlling the doors  20 ,  200  to open and close by rotating about their rotational axes  18 ,  218  are available in the art, instead of being driven by the fixing members  16 ,  216 . While in the embodiment of  FIG.  5    the fixing member  16 ,  216  and mounting member  30 ,  230  are shown as mutually rotatable, in other embodiments the fixing member  16 ,  216  may remain fixed while the mounting member  30 ,  230  rotates about it. For example, electromagnets affixed to the support structure  14  may be used to retain the doors  20 ,  220  in the closed configuration (where ends  24 ,  224 ,  26 ,  226  of the panel section  22 ,  222  comprise magnetic material or further electromagnets), and the electromagnets may be switched off in order to release the respective doors  20 ,  220 . The electromagnets may then be reactivated to draw the respective doors  20 ,  220  back into the closed configuration. 
     In another embodiment, a tensile member (e.g. a rope, chain or lanyard) coupled to the outside edge (i.e. towards or at the free edge  51 ,  251 ) of the panel section  22 ,  222  may be driven to pull the respective door  20 ,  220  towards the ceiling  64  of the cavity  60  to close the door  20 ,  220 . The tensile member may be driven by an actuator (e.g. a winch) within the cavity  60  or disposed outside the upper surface of the support structure  14 . For example, the actuator may be disposed on the ceiling  64  of the cavity  60 . The tensile member may therefore be released to allow the respective door  20 ,  220  to open. 
     Instead of being driveable, the fixing members  16 ,  216  may be apertures or spigots about which the doors  20 ,  220  are driven to rotate. In other words, one important aspect of the present disclosure lies in the relative positioning of the panel sections  22 ,  222  and their rotational axes  18 ,  218 , rather than how they are driven to rotate about those rotational axes  18 ,  218 . 
     While the actuators  32 ,  232  are shown as being direct drive rotary motors, they may instead be arranged to drive respective doors  20 ,  220  about their rotational axes  18 ,  218  by a mechanism of gears and/or journals. In other words, the actuators/motors  32 ,  232  may not be co-axial with the rotational axes  18 ,  218  of the respective doors  20 ,  220 . The fixing members  16 ,  216  here, instead of being longitudinal shafts, may be geared wheels. 
     In the illustrated embodiment, the mounting member  30 ,  230  has an engagement feature  31 ,  231  which engages with a compatible engagement feature on the fixing member  16 ,  216 . For example, the engagement feature  31 ,  231  may be an aperture into which the fixing member  16 ,  216  in the form of a shaft is located and engaged, for example by some mechanical means such as a friction mounting, splined arrangement, or interlocking arrangement. Therefore, the mounting member  30 ,  230  and fixing member  16 ,  216  are engaged such that they are rotatable together around the rotational axis  18 ,  218 . In other words, in the illustrated embodiments, the engagement feature  31 ,  231  is a journal for receiving the fixing member  16 ,  216 , which is in the form of a rotatable shaft (or spigot). However, in other embodiments, the fixing member  16 ,  216  may be in the form of an aperture or recess in a wall (or strut) of the support structure  14 . Here, the engagement feature  31 ,  231  is in the form of a shaft/spigot for passing through the aperture and engaging with an actuator  32 ,  232 . 
     As best shown in  FIG.  5   , each panel section  22 ,  222  comprises a second mounting member  130 ,  330  spaced apart from and opposite the respective mounting member  30 ,  230  along the length L of the panel section  22 ,  222 . The second mounting member  130 ,  330  comprises a second engagement feature  131 ,  331  configured to engage with a second fixing member  116 ,  316 . The second engagement feature  131 ,  331  is disposed co-axially with the respective engagement feature  31 ,  231 . In some embodiments, the second fixing member  116 ,  316  is coupled to the support structure  14 . In the illustrated embodiment, the second fixing member  116 ,  316  is a rotatable drive coupled to a second actuator  132 ,  332 . The second fixing member  131 ,  331  and respective second mounting member  130 ,  330  are configured to permit the respective doors  20 ,  220  to rotate about their respective rotational axes  18 ,  218 . The second mounting member  130 ,  330  and the second fixing member  116 ,  316  are coupled such that the door  20 ,  220  is rotatable with, and driveable by, the second fixing member  116 ,  316  about the rotational axis  18 ,  218  to rotate the panel section  22 ,  222  about the rotational axis  18 ,  218 . 
     The second engagement feature  131 ,  331  may be an aperture, or other suitable mechanical means configured to engage with a compatible second fixing member  116 ,  316 . The second fixing member  116 ,  316  may be provided as a spigot, which the second mounting member  130 ,  230  is free to rotate around and/or relative to. In other words, the second fixing member  116 ,  316  may not be rotatable, or may not be actuated. 
     In other words, the second mounting member  130 ,  330 , second engagement feature  131 ,  331 , second fixing member  116 ,  316  and second actuator  132 ,  332  may take the same form as, respectively, the mounting member  30 ,  230 , engagement feature  31 ,  231 , fixing member  16 ,  216  and actuator  32 ,  232 , but disposed opposite thereto. The second actuator  130 ,  330  may be driven at the same time and speed as the respective actuator  30 ,  230  in order to enable smooth opening of the door and reduce stress on one end  24 ,  26 ,  224 ,  226 . Alternatively, the actuator  32 ,  232  may be configured to rotate the door  20 ,  220  in the opposite direction to the respective second actuator  132 ,  332 . For example, the actuator  32 ,  232  may be activated to open the door  20 ,  220  while the second actuator  132 ,  332  may be activated to the close the same door  20 ,  220 . Here, when one of the actuator  32 ,  232  and second actuator  132 ,  332  is activated, the opposing actuator  32 ,  232  or second actuator  132 ,  332  is allowed to freely rotate. 
     Each door  20 ,  220  may be divided along its length L, perpendicularly to the rotational axes  18 ,  218 , into two parts, such that each part is independently configurable to be in an open configuration or the closed configuration by way of actuation of a respective actuator  32 ,  132 ,  232 ,  332  coupled to that part. In other words, the panel section  22 ,  232  and (where present) the reinforcement member  52 ,  252  may be bifurcated. This enables part of the cavity  60  to be accessible without having to reveal the entire contents of the cavity  60  or expose parts of the panels  22 ,  222  unnecessarily to the airflow. Two parts of one door  20 ,  220  may be opened simultaneously to fully reveal the associated region  70 ,  270  of the opening  12 . 
     The, or each, mounting member  30 ,  130  is located inside the cavity  60 , and the rotational axis, or rotational axes,  18 ,  218  are offset from the opening  12  along their respective lengths. Hence, the fixing members  16 ,  116 ,  216 ,  316  provided on or through the support structure  14  are located inside the cavity  60 , offset from the opening  12 . That is to say, the engagement features  31 ,  131 ,  231 ,  331  and the mounting members  30 ,  130 ,  230 ,  330  to which they relate, are spaced apart from the opening  12  on the inside of the cavity  60 . 
     The shortest distance of the rotational axes  18 ,  118  to the opening  12  may be at least 15% but no more than 50% of the panel section  22 ,  222  width. The shortest distance of the rotational axes  18 ,  118  to the opening  12  may be dependent on at least aircraft  1  structural form, applied loads, door stiffness required, speed of operation, and/or internal load packaging. 
     As illustrated in  FIGS.  6   a - c   , the support structure  14  (i.e. housing) may be used to house payloads  62  (i.e. equipment) of various kinds, for example sensors (e.g. optical camera), landing gear, ordnance, cargo, drones, antennas, cameras and/or fuel tanks. In the Figures, the payloads  62   a - f  (generally  62 ) are shown as missiles. Each of the payloads  62  may be different to one another. 
     As shown by comparison of  FIGS.  6   a  and  6   b   , one or both of the doors  20 ,  220  may be provided with a payload  62 , which rotates with the door  20 ,  220 . For example, payload  62   a ,  62   b , may be attached to the inside surface of the planar portion  54 ,  254  or the inside of the panel section  22 ,  222  such that when the door  20 ,  220  is open, the payload is in a position ready to be operated or accessed. As best shown in  FIGS.  4   b - e   , the planar portion  54 ,  254  of the reinforcement member  52 ,  252  may comprise recesses  80  (i.e. pockets) for coupling of payloads  62 . 
     The ceiling  64  of the cavity  60  (i.e. the inside top surface of the support structure  14 , facing the opening  12 ) is provided with at least one pylon  356  for receiving a payload  62   c - f . In other words, the support structure  14  and the doors  20 ,  220  may be configured to carry payloads  62 . In some embodiments, only the doors  20 ,  220  are arranged to carry payloads  62  to minimise the required width of the panel section  22 ,  222 . 
     Hence, there may be provided a door assembly (providing at least one door  20 ,  220 ), a payload bay  10  comprising the door assembly of the present disclosure rotatably coupled thereto, and/or an aircraft  1  comprising a payload bay  10  of the present disclosure. The door assembly may be provided with actuation means. The door assembly tends to provide a more space-efficient door assembly compared to examples of the related art. It also tends to provide a means of mounting an automated door  20 ,  220  with a more robust mounting mechanism than that provided by the related art. 
     The door  20 ,  220  design of the present disclosure tends to maximise use of the cavity  60  volume. This is because the doors  20 ,  220  of the present disclosure are provided to the sides of the support structure  14  and provide a small obstruction when open, rather than in examples of the related art where door-actuating mechanisms and hinges may partly obstruct the opening when the doors are open. Also, since, when open, the panel sections  22 ,  222  of the doors  20 ,  220  of the present disclosure do not extend as far out of the bay as examples of the related art, there is less wind resistance (i.e. less drag) when open in flight, and the ground clearance of the aircraft  1  is increased which makes maintenance of the aircraft  1  easier for ground crew. 
     Hence, for a given opening  12  perimeter (i.e. size), the size of the door  20 ,  220  surface area exposed to aerodynamic forces tends to be significantly reduced compared with traditional designs, which tends to result in improved aircraft  1  aerodynamic properties when the payload bay  10  is open, primarily in the form of lower drag. In other words, less kinetic energy is lost during times when the bay doors  20 ,  220  are open, and lower impact on host aircraft  1  stability and control. Smaller exposed door area, and hence lower aerodynamic loading, may also mean smaller or less powerful actuators  32 ,  132 ,  232 ,  332  are required to open the door  20 ,  220 . 
     The doors  20 ,  220  of the present disclosure may rotate through 90 degrees or more to expose the opening  12  without the need of extended hinges  3   a ,  3   b  (for example as shown in the prior art of  FIG.  1   ). This provides a simpler actuation solution compared to examples of the related art. 
     Additionally, the actuation mechanism infrastructure of the present disclosure compared to traditional designs tends to be reduced. With a traditional payload bay design, an actuator would be connected to a gearbox to drive a shaft or torque tube from which powered hinges extract motive force to drive doors through a set angle. The door assembly concept of the present disclosure replaces much of this with fixing members  16 ,  216 ,  116 ,  316  which form part of, or are coupled to, the door panel sections  22 ,  222 . Hence the doors  20 ,  220  of the present disclosure are driven from one or both ends by an actuator  16 ,  216 ,  116 ,  316 , thereby simplifying the actuation mechanism design which in turn may improve reliability (for example, because fewer parts are required) and also mechanical accuracy (because fewer parts are used, and hence there are fewer parts with a tolerance to stack up) which could simplify door assembly and control. 
     As discussed, in some examples a single door  20  may be provided to cover the opening  12  of the payload bay  10  (i.e. the entrance to the cavity  60  within the payload bay  10 ). However, for a given opening  12  size, the provision of two doors  20 ,  220 , as shown in  FIGS.  3   a  to  6   c   , which rotate in opposite directions, means that the overall payload bay  10  height/depth may be less, tending to allow for greater packaging efficiency. Packaging efficiency may be defined as number of stores (i.e. payloads  62 ) per unit cross sectional area or per unit volume. Arranging doors  20 ,  220  to rotate in this way allows them to mostly retract internally, resulting in the benefits described above. Embodiments with a single door  20  may relate to payload bays  10  for carrying a single missile or landing gear unit, for example. Such a payload bay  10  may be found on the shoulder of the aircraft&#39;s fuselage. 
     All of the features disclosed in this specification (including any accompanying claims, abstract and drawings), and/or all of the steps of any method or process so disclosed, may be combined in any combination, except combinations where at least some of such features and/or steps are mutually exclusive. 
     Each feature disclosed in this specification (including any accompanying claims, abstract and drawings) may be replaced by alternative features serving the same, equivalent or similar purpose, unless expressly stated otherwise. Thus, unless expressly stated otherwise, each feature disclosed is one example only of a generic series of equivalent or similar features. 
     The invention is not restricted to the details of the foregoing embodiment(s). The invention extends to any novel one, or any novel combination, of the features disclosed in this specification (including any accompanying claims, abstract and drawings), or to any novel one, or any novel combination, of the steps of any method or process so disclosed.