Fuselage structure of an aircraft, door assembly of an aircraft, and aircraft

Abstract

The present invention relates to a fuselage structure of an aircraft, a door assembly of an aircraft and an aircraft. In order to allow for an improved door for an aircraft, the present invention proposes a fuselage structure (20) of an aircraft (10), comprising a plurality of frames (23) extending in a circumferential direction of the fuselage structure (20), an aerodynamic skin (24) supported by the frames (23), at least one pair of guide rails (31) extending in a longitudinal direction of the fuselage structure (20) and supported by the frames (23) in a load-transferring manner, wherein each pair of guide rails (31) defines a fuselage opening (25), wherein the guide rails (31) are configured to support a door leaf (35) in a sliding manner such that the door leaf (35) is movable along the longitudinal direction between a fully open position in which the fuselage opening (25) is uncovered and a fully closed position in which the fuselage opening (25) is closed.

Description

Technical Field

[0001] This invention relates to sliding door mechanisms for aircraft. Specifically, it relates to fuselage structures, door assemblies, locking mechanisms, and aircraft equipped with fuselage structures, door assemblies, and locking mechanisms. Background Technology

[0002] In the ever-evolving field of aircraft design and engineering, efficiency, reliability, and performance are paramount. As aircraft structures become more complex and the need for weight reduction and operational efficiency increases, conventional technological solutions often reach their limits. One area requiring significant improvement is the design and integration of fuselage doors—particularly cargo doors, passenger (PAX) doors, and maintenance doors.

[0003] Conventionally, these large fuselage cutouts close using doors that are continuously hinged along one side, secured to the fuselage using a hook-based system. Continuous hinges not only significantly increase the structure's weight, but also require complex and expensive assembly. Furthermore, these hinge-based systems rely on standardized aircraft frame patterns—typically spaced 21 inches—meaning that pressure loads from the cabin or cargo hold area must be distributed across robust door frames that transfer these lateral loads to the fuselage frame. This results in a bulky, mechanically complex system that is ill-suited to the requirements of modern aircraft. Summary of the Invention

[0004] The object of this invention is to improve doors for aircraft. This object is achieved through the subject matter of the main aspects of the invention. Preferred embodiments are the subject matter of the subsidiary aspects of the invention.

[0005] The present invention provides a fuselage structure for an aircraft, comprising: a plurality of frames extending circumferentially along the fuselage structure; an aerodynamic skin supported by the frames; and at least one pair of guide rails extending longitudinally along the fuselage structure and supported by the frames in a load-transfer manner, wherein each pair of guide rails defines a fuselage opening, wherein the guide rails are configured to slide and support a door leaf such that the door leaf can move longitudinally between a fully open position and a fully closed position, wherein in the fully open position the fuselage opening is uncovered, and in the fully closed position the fuselage opening is closed.

[0006] Preferably, the body structure further includes a roller mechanism disposed on a guide rail and comprising a plurality of rollers configured to engage the door leaf to allow sliding movement of the door leaf.

[0007] Preferably, each guide rail includes at least one roller groove configured to movably receive and support the roller.

[0008] Preferably, the body structure also includes a locking mechanism that can switch between an unlocked state and a locked state. In the unlocked state, the installed door leaf can move, and in the locked state, the movement of the installed door leaf is prevented.

[0009] Preferably, the locking mechanism is integrated into the roller mechanism such that, in the locked state, the locking mechanism applies force to the roller to prevent movement by means of frictional engagement and / or form-fit locking.

[0010] Preferably, in the unlocked state, the roller is able to roll, and in the locked state, the roller is forced against the guide rail, preferably against the side wall portion of the guide rail, or forced towards the installed door leaf.

[0011] Preferably, the guide rail is configured to enable a load-bearing joint between the door leaf guided in the guide rail and the frame. Preferably, the load-bearing joint is capable of transmitting bending loads and / or the load-bearing joint includes or is composed of a bending-resistant joint.

[0012] Preferably, the load-bearing joint is formed at least in the fully closed position, and preferably at least partially by means of a locking mechanism in a locked state.

[0013] Preferably, each guide rail includes a pair of sidewall portions and a bottom portion that define a guide channel configured to receive and support a door leaf in a sliding manner.

[0014] Preferably, the roller mechanism and / or locking mechanism are provided on at least one sidewall portion of the sidewall portion.

[0015] Preferably, the roller mechanism is disposed on at least one sidewall, wherein the locking mechanism, preferably the actuating member of the locking mechanism, is partially disposed on the bottom portion.

[0016] Preferably, each roller groove is provided or formed on the sidewall portion.

[0017] The present invention provides a door assembly for an aircraft, the door assembly including the fuselage structure previously described and a door leaf supported for sliding in a guide rail.

[0018] Preferably, the door leaf includes a roller mechanism and a partial locking mechanism.

[0019] Preferably, the door leaf includes at least one roller groove that movably receives and supports the roller.

[0020] The present invention provides an aircraft, preferably an airplane, which includes the fuselage structure and / or the door assembly previously described.

[0021] This is a concept that offers an alternative to traditional methods: a form-fitting sliding door system that could replace the classic cargo doors currently used in a wide range of aircraft (A / C) projects. The sliding door system is designed to be not only lighter and more space-saving, but also structurally robust, providing bending integration with the fuselage and a direct load path for lateral pressure loads.

[0022] Another concept is to create a sliding door operated via the inner and outer flanges of the aircraft's fuselage frame. This door can slide into place and seal the fuselage cutout by completely closing the gap in the door's final locked position. Properly arranged seals can improve gap closure. The sliding door itself becomes part of the structural system, thereby distributing pressure and loads through direct and continuous engagement with surrounding fuselage sections, particularly the frame, rather than relying on complex actuations of multiple hooks and latches to form a shape with the aircraft fuselage.

[0023] This design makes special use of the junction between the cylindrical and conical sections of the aircraft fuselage. By allowing the door to slide outward and then backward along this conical geometry, the system eliminates wind load issues during movement, thus allowing safe operation even outdoors or in windy conditions. The backward sliding motion can occur entirely outside the fuselage skin, providing the additional benefits of saving internal space and reducing the clearance area required for door operation within the aircraft.

[0024] This approach allows load-bearing sliding door systems to withstand and / or distribute pressure loads at least as effectively as, or even more effectively than, conventional door mechanisms. Furthermore, significant improvements in weight, complexity, and / or operating space can be achieved.

[0025] As the aerospace sector adopts alternative fuels such as hydrogen, it may require larger fuselage openings for equipment access, particularly for fuel tank maintenance. Consequently, the need for robust yet lightweight door systems has increased. The concepts disclosed in this paper offer scalable, technically sound, and future-proof solutions to these emerging needs.

[0026] The proposed form-fit sliding door system demonstrates a significant improvement over existing door technologies used in modern aircraft. This system simplifies door integration, reduces weight and maintenance complexity, and provides a structurally improved alternative to conventional articulated systems. Furthermore, the system can be seamlessly integrated into a variety of aircraft platforms, whether for cargo or passenger applications, making it a valuable advancement in aircraft structural design.

[0027] In some implementations, the cutout in the aircraft fuselage includes integrated locking engagements. These engagements can serve as the primary engagement points for sliding doors, allowing the doors to lock securely in place when closed. Unlike conventional cargo doors, this cutout is geometrically and structurally reinforced as a sliding mechanism, allowing the door to be seamlessly integrated into the contours of the aircraft fuselage.

[0028] The entire system can be constructed as an active load-bearing component of the aircraft's structural system. Once the door is closed and locked, it functions as an extension of the fuselage, effectively distributing both aerodynamic and internal pressure loads. In particular, bending loads can be transferred between the door and the fuselage. The sliding system itself is designed so that, in its final position, the door achieves a tight and continuous form-fit or frictional engagement with the surrounding fuselage structure. This direct engagement allows for the creation of reinforced connections that eliminate the need for external locking hooks or heavy-duty hinges.

[0029] To ensure smooth and reliable movement, the door can operate on rollers, such as ball bearings, which can be integrated with a locking function. Bearings reduce mechanical friction and wear, while also ensuring the door is securely locked in place once it has slid into position. Traditional aircraft door systems often rely on spring-loaded components to close gaps and maintain a seal; however, the disclosed solution eliminates the need for such spring mechanisms. This simplifies the overall system architecture and reduces the number of potential points of failure. Preferably, a more consistent and reliable seal can be achieved.

[0030] Passive sealing systems are another concept in this design. These systems can provide environmental sealing against factors such as pressure differentials, moisture, and / or contaminants without relying on powered actuators or complex mechanisms. The use of passive systems can improve reliability while reducing maintenance needs and energy consumption, making them a highly attractive solution for modern aircraft.

[0031] Another innovative aspect of this design lies in how the door moves during operation. Utilizing the conical geometry of the aircraft's rear fuselage section, the door can move outwards and then slide rearwards along the outer contour of the fuselage. This path allows the door to be held completely outside the aircraft body during movement, which not only helps avoid the complexities associated with internal clearance spaces but also protects the system from wind loads during operation. This is an ingenious solution that has the potential to improve both safety and functionality.

[0032] When the door reaches its final position, it can be continuously locked along its perimeter on the vertical axis (often referred to as the Z-axis in the aircraft coordinate system). This allows for a firm and stable engagement with the fuselage. In addition to vertical locking, the system can also lock the door along a lateral axis, often referred to as the Y-axis, which prevents any unintended movement along the longitudinal direction of the aircraft's center, often referred to as the X-axis. This multi-directional implementation of the locking mechanism allows the door to remain rigid and fully integrated into the aircraft's structure under most—if not all—operating conditions, including pressurized and flight loads.

[0033] This system offers numerous advantages and aligns with the aerospace industry's overall goals of weight reduction, increased reliability, and better space utilization. By eliminating the need for heavy, continuous articulations, external hooks, and complex actuators, the system provides a significantly lighter structural solution. This weight reduction contributes to improved fuel efficiency and increased payload capacity of the aircraft.

[0034] In terms of space efficiency, the outward and backward movement of sliding doors means that their operation typically requires no additional internal clearance. This is especially valuable in space-constrained areas, such as compact cargo holds or maintenance compartments.

[0035] The structural integration achievable through this design is also a major benefit. Doors can function as a true part of the fuselage structure, rather than as separate or loosely attached components. This allows doors to more effectively bear and distribute loads—especially bending loads—thereby reducing stress concentration on nearby fuselage components and enhancing overall structural durability.

[0036] The simplicity and reliability of the system can be further enhanced by reducing moving parts and using passive systems for both movement and sealing. This not only reduces the likelihood of mechanical failure but also reduces maintenance requirements throughout the aircraft's lifespan.

[0037] The versatility of the disclosed concept allows it to be applied to a range of aircraft projects and applications. While particularly well-suited for cargo doors, the design can also be used for passenger (PAX) doors, improving both safety and ease of operation during boarding and disembarkation. Furthermore, the system's robust and space-saving characteristics make it ideal for maintenance doors, particularly those required for servicing hydrogen storage tanks in next-generation zero-emission aircraft.

[0038] In summary, the concept presented in this paper allows for substantial advancements in aircraft door technology, providing a robust, lightweight, and highly reliable alternative to conventional articulated systems. This solution is designed not only to meet the needs of today's aircraft but also to address the challenges of future aerospace innovation.

[0039] The present invention provides a locking mechanism for a door assembly of an aircraft, the locking mechanism being switchable between an unlocked state and a locked state. In the unlocked state, the installed door leaf is movable, and in the locked state, the movement of the installed door leaf is prevented. The locking mechanism includes: a plurality of rollers, the plurality of rollers being suitably arranged to support and engage the installed door leaf of the door assembly; at least one roller support element, the at least one roller support element supporting and engaging the rollers, wherein, in the unlocked state, the roller support element engages with the rollers to allow the rollers to roll, and wherein, in the locked state, the roller support element engages with the rollers to prevent the rollers from rolling by means of frictional engagement with at least the roller support element.

[0040] Preferably, the locking mechanism further includes at least one movable roller support element and at least one fixed roller support element. The at least one movable roller support element supports and engages the first group of rollers, and the at least one fixed roller support element is fixed, supports, and engages the second group of rollers. Preferably, in the unlocked state, the movable roller support element and the fixed roller support element engage with the first and second groups to allow the corresponding rollers to roll. Preferably, the locking state can be achieved by moving the movable roller support element closer to the fixed roller support element in a manner that allows the first group to engage the installed door leaf or fixed member, forming a frictional engagement between the first group and the movable roller support element. Preferably, the second group and the fixed roller support element can form a frictional engagement between the second group and the fixed roller support element due to the first group pushing the installed door leaf or fixed member.

[0041] Preferably, the locking mechanism further includes at least one pair of movable roller support elements. Preferably, a first movable roller support element supports and engages a first group of rollers, and a second movable roller support element supports and engages a second group of rollers. Preferably, in the unlocked state, the movable roller support elements engage with the first and second groups to allow the corresponding rollers to roll. Preferably, the locked state can be achieved by moving the movable roller support elements away from each other in a manner that allows the first and second groups to engage with the installed door leaf or fixing member to form a frictional engagement between the first and second groups and the installed door leaf or fixing member.

[0042] Preferably, the locking mechanism further includes an actuating member arranged to move the roller support element to produce a locked state and an unlocked state.

[0043] Preferably, the actuating member is configured to pivot or linearly displace the roller support element to produce a locked state and an unlocked state.

[0044] Preferably, the load-bearing joint is automatically formed as the door leaf moves to the fully closed position, preferably by means of, for example, automatically moving the actuating member to the fully closed position via a mechanical linkage.

[0045] The present invention provides a door assembly for an aircraft, comprising: a locking mechanism as previously described; a door leaf; and a pair of guide rails extending longitudinally and supporting the door leaf in a load-transfer manner. Preferably, the pair of guide rails define a fuselage opening. Preferably, the guide rails support the door leaf in a slidable manner, such that the door leaf can move linearly along the guide rails between a fully open position and a fully closed position, in which the fuselage opening is uncovered and in the fully closed position, the fuselage opening is closed. Preferably, the locking mechanism is configured such that, in an unlocked state, the door leaf can move between a fully open position and a fully closed position, and in a locked position, movement of the door leaf is prevented.

[0046] Preferably, one of the guide rails includes a movable roller support element that supports and engages a first group of rollers, and the other guide rail includes a fixed roller support element fixed to the guide rail, which supports and engages a second group of rollers. Preferably, in the unlocked state, the movable and fixed roller support elements engage with the first and second groups such that the corresponding rollers can roll to allow movement of the door leaf. Preferably, the locked state can be achieved by moving the movable roller support element toward the door leaf or guide rail such that the first group engages the door leaf or guide rail to form a frictional engagement between the first group, the movable roller support element, and the door leaf or guide rail, and such that the second group and the fixed roller support element form a frictional engagement between the second group and the fixed roller support element due to the first group pushing the door leaf or guide rail.

[0047] Preferably, the locking mechanism further includes at least one pair of movable roller support elements, wherein a first movable roller support element supports and engages a first group of rollers, and a second movable roller support element supports and engages a second group of rollers. Preferably, in the unlocked state, the movable roller support elements engage with the first and second groups such that the corresponding rollers can roll. Preferably, the locked state can be achieved by moving the movable roller support elements away from each other such that the first and second groups engage the door leaf or guide rail and form a frictional engagement with the door leaf or guide rail.

[0048] Preferably, each guide rail includes a pair of sidewall portions and a bottom portion that define a guide channel that slidably receives and supports the door leaf.

[0049] Preferably, the locking mechanism is disposed on the guide rail, and more preferably on the side wall portion.

[0050] Preferably, the locking mechanism is partially disposed on the door leaf, wherein the actuating member is partially disposed on the bottom portion.

[0051] Preferably, the door leaf or each guide rail includes at least one roller groove that movably receives and supports the roller.

[0052] The present invention provides an aircraft fuselage structure comprising: a previously described door assembly; a plurality of frames extending in a circumferential direction along the fuselage structure; and an aerodynamic skin supported by the frames, wherein a pair of guide rails extends in a longitudinal direction along the fuselage structure and is supported by the frames in a load-transfer manner.

[0053] Preferably, the actuating member is at least partially disposed on one of the frames of the frame.

[0054] The present invention provides an aircraft, preferably an airplane, which includes any of the previously described locking mechanism, door assembly and fuselage structure.

[0055] The concept described in this paper represents an advancement in aircraft door systems, offering a practical, efficient, and / or structurally improved solution that can be incorporated into all aircraft (A / C) projects involving large fuselage cutouts. This innovation is not limited to a specific aircraft type or configuration; rather, it is designed to be adaptable and scalable, providing improvements to door systems from cargo and passenger (PAX) doors to specialized maintenance access points. Of particular relevance is the application of this concept to doors capable of maintaining hydrogen storage systems, an area that is becoming increasingly important with the rise of alternative energy aircraft and zero-emission aviation initiatives.

[0056] Traditional cargo doors are typically attached to the fuselage using continuous hinges. These hinges are integrated along the entire edge of the door and usually require a precise frame pattern, typically based on the aircraft fuselage frame's 21-inch pitch. In this configuration, the door achieves a shape-fitting fit with the fuselage using actuation hooks that engage the door during flight and hold it in place. While this approach has been standard practice for decades, the hinges and hook mechanisms are generally heavy and expensive.

[0057] In these conventional systems, internal pressure loads generated by pressurized compartments or cargo holds are typically transferred from the doors to the fuselage via robust door frames. These frames are designed to withstand lateral loads, but they do not allow for bending-resistant integration between the doors and the fuselage.

[0058] The disclosed concept introduces a shape-fitting sliding door that can be directly integrated into the aircraft's fuselage structure. This door design not only replaces the classic hinged cargo door but also surpasses it in performance, load management, and efficiency. For example, compared to classic design methods, the rigidity and stability of the door-fuselage joint can be increased through continuous bending-resistant frame attachments. Furthermore, it reduces the complexity of the aircraft structure and maintenance procedures. Due to its efficient load path design, the door can also withstand increased structural loads.

[0059] One concept is to implement a locking system that secures the door along the aircraft's longitudinal axis (typically the X-direction) while allowing the door to function as a form-fitting load-bearing element within the fuselage structure. This concept enables the door to become an integral part of the frame rather than an additional structure, especially when the locking mechanism is in its locked state.

[0060] In some implementations, the sliding mechanism operates via inner and outer flanges of the aircraft fuselage frame. When the door moves to its final closed position, the sliding gap can be completely sealed, resulting in a tight form-fit integration. This allows the door, particularly when the locking mechanism is engaged, to structurally engage with the fuselage frame by creating a bending-resistant connection. This design provides a continuous and stable load path for lateral pressure loads, significantly enhancing the structural integrity of the entire assembly.

[0061] Another aspect of the system is its use of the junction between the conical and cylindrical sections of the aircraft fuselage. By utilizing this transition zone, the door can move laterally without being affected by wind loads, and then move rearward to the outside of the aircraft skin. This external movement is unaffected by aerodynamics and allows for safe, space-saving operation. Furthermore, because the door remains outside the fuselage during the sliding process, usable internal compartment or cargo hold space is preserved, and operational efficiency is improved.

[0062] Another component of this concept is its locking system, which secures the door in the X-direction once it reaches its final position. This allows the door to remain stable and fixed during flight, contributing to both safety and structural strength. The form-fitting locking mechanism reinforces the door as a load-bearing structure, effectively making it a functional extension of the fuselage rather than a separate, detachable component.

[0063] In some implementations, ball bearings with a locking function are used. These bearings not only facilitate smooth sliding motion but also secure the door in place once it reaches its end position. This dual-purpose function allows for a reduction in the number of moving parts and simplifies the mechanical complexity of the system.

[0064] On the other hand, it involves a continuous shape-fit locking of the door in the Z direction, which corresponds to the vertical axis of the aircraft. By engaging the door vertically along its entire circumference, this locking method ensures a consistent and robust attachment, thus resisting vertical displacement or deformation that may be caused by pressurization or aerodynamics. Similarly, the system also allows the door to be locked in the Y direction—the lateral axis—thereby effectively blocking movement in the X direction through (additional) frictional engagement. The result is a stable three-dimensional locking frame that maintains the door's position in all spatial dimensions.

[0065] In some embodiments, an unfolding mechanism is used to convert sliding motion into locking motion. This achieves a seamless transition from door movement to door locking without requiring a separate mechanical stage. The invention also includes an actuated locking system designed for form-fit engagement and body reinforcement, enhancing the security and reliability of the components. Another concept involves including rolling supports within the sliding system, which contributes to smooth, durable, and low-friction operation of the door throughout its lifespan.

[0066] In addition to its structural benefits, this invention offers improvements in weight efficiency. By eliminating the need for heavy, continuous hinges and complex actuation hook systems, the overall weight of the door assembly can be reduced. This directly benefits aircraft performance by improving fuel efficiency and payload capacity. Furthermore, the simplified mechanical architecture reduces the number of parts subjected to wear and tear, which in turn reduces maintenance requirements and increases system reliability over time.

[0067] The disclosed concept is highly versatile. It can be applied equally to cargo and passenger doors, providing enhanced safety, simplified operation, and reduced maintenance in a variety of usage scenarios. Furthermore, the concept can be implemented in the design of maintenance doors, providing access to critical components such as hydrogen storage tanks. As the aviation industry shifts towards cleaner energy and sustainable technologies, systems that allow robust and efficient access to these components will be crucial. The proposed door system is well-suited to meet these future needs. Attached Figure Description

[0068] Embodiments of the present invention will be described in more detail with reference to the accompanying schematic diagrams listed below:

[0069] Figure 1 A top view of the rear section of the aircraft is depicted;

[0070] Figure 2 A side view of the rear section is depicted, in which the door is in the fully open position;

[0071] Figure 3 A side view of the rear section is depicted, in which the door is in the fully closed position;

[0072] Figure 4 The implementation of the fuselage structure is described;

[0073] Figure 5 The fuselage structure with a roller mechanism is depicted;

[0074] Figure 6 The fuselage structure is depicted, in which the door assembly is in the unlocked state;

[0075] Figure 7 The fuselage structure is depicted, in which the door assembly is in a locked state;

[0076] Figure 8 The illustration shows the load transfer of the fuselage structure, with the door assembly in a locked state;

[0077] Figure 9 Another embodiment of the fuselage structure is depicted, in which the door assembly is in an unlocked state; and

[0078] Figure 10 The fuselage structure is depicted, in which the door assembly is in a locked state. Detailed Implementation

[0079] Reference Figure 1 The rear section of the aircraft 10 is depicted. It is helpful to consider the following definitions: the longitudinal axis of the aircraft 10 is designated as the Z-axis, the vertical axis of the aircraft 10 is designated as the Y-axis, and the lateral direction of the aircraft 10 is designated as the X-axis. It should be noted that the term "direction" can also be used instead of "axis".

[0080] The aircraft 10 includes a fuselage structure 20. In a manner known per se (and therefore omitted), the aircraft 10 includes wings for generating lift and engines for generating thrust, which are mounted to the fuselage structure 20.

[0081] The fuselage structure 20 includes a tail section 21. The tail section 21 may include and support a plurality of functional surfaces, namely a horizontal stabilizer 21a, an elevator 21b, a vertical stabilizer 21c, and a rudder 21d, in a manner known in the art.

[0082] The tail section 21 includes aerodynamic skin 24 forming aerodynamic surfaces. The tail section 21 has a generally conical tapering shape that tapers towards the rear. In other words, observing a series of longitudinally continuous transverse cross-sections (i.e., disregarding functional surfaces) through the tail section 21, the outer circumference of each cross-section monotonically decreases towards the rear. The cross-sections are typically circular or elliptical in shape.

[0083] The fuselage structure 20 also includes a main fuselage section 22. The main fuselage section 22 generally forms the body of the aircraft 10. The main fuselage section 22 has a generally cylindrical shape with only slight variations in diameter. In other words, observing a series of longitudinally continuous transverse cross-sections through the main fuselage section 22 (i.e., ignoring details such as windows, doors, etc.), the outer circumference of each cross-section is approximately the same within a tolerance zone of 5% to 10%. The cross-sections typically have a circular or elliptical shape.

[0084] The fuselage structure 20 includes a fuselage opening 25, which is preferably formed in a circumferential section of the fuselage structure 20.

[0085] The aircraft 10 also includes a door assembly 30 integrated into the fuselage structure 20. The door assembly includes a door leaf 35 that covers the fuselage opening 25 when in the closed position.

[0086] Reference Figure 2 and Figure 3 The image depicts an aircraft 10 in a side view. The aircraft 10 may include one or more liquid hydrogen tanks 11. The liquid hydrogen tanks 11 may be housed within the tail section 21 and the rear portion of the main fuselage section 22. Preferably, one hydrogen tank 11 may bridge the boundary between the tail section 21 and the main fuselage section 22.

[0087] The fuselage structure 20 includes a plurality of frames 23 spaced apart by a predetermined distance in the longitudinal direction, for example, typically 21 inches. The frames 23 extend in the circumferential direction of the fuselage section 20. For clarity, not all of the frames 23 are shown.

[0088] It should be noted that although the description focuses on hydrogen tank 11, hydrogen tank 11 can be considered as a substitute for any other equipment that may require regular maintenance and is typically only accessible through a large fuselage opening 25. A fuselage opening 25 is typically large in this sense if it spans at least two or three frames 23 along the longitudinal direction of the fuselage structure 20.

[0089] The aircraft 10, particularly the fuselage structure 20, includes an aerodynamic skin 24. The aerodynamic skin 24 is supported by a frame 23.

[0090] like Figure 2 As depicted, door assembly 30 is in the open position. Figure 3 As depicted, door assembly 30 is in the closed position. The door assembly includes a pair of guide rails 31, which are examples of fixed members. The guide rails 31 are arranged at the top and bottom of the body opening 25. The guide rails 31 are mounted to the frame 23. The guide rails 31 can be installed by cutting the frame 23 in place to form the body opening 25 and having the remaining sections support the guide rails 31.

[0091] Reference Figure 4 It depicts a cross-section through the fuselage structure 20, including the fuselage opening 25. As indicated by the axes, the vertical upward direction (Z direction) points to the left, the vertical downward direction points to the right, the lateral outward direction (Y direction) points upward, the lateral inward direction points downward, the longitudinal forward direction (X direction) points outward from the drawing plane, and the longitudinal backward direction points into the drawing plane. For all Figures 4 to 10 Maintain this orientation.

[0092] The guide rail 31 is adapted to receive the door leaf 35 and to support the door leaf 35 in a movable manner. For example... Figure 4 As shown in the figure, the guide rail 31 may include a guide channel 32.

[0093] The guide channel 32 may be a substantially U-shaped channel. The guide channel 32 opens toward the fuselage opening 25. The guide rails 31 are arranged such that the respective guide channels 32 face each other through their respective openings.

[0094] The guide rail 31 may include a pair of sidewall portions 33 and a bottom portion 34. The sidewall portions 33 are spaced apart from each other along the Y direction via the bottom portion 34. The sidewall portions 33 protrude from the bottom portion 34 toward their respective opposing guide rails 31 along the Z direction. The sidewall portions 33 may also protrude from the bottom portion 34 in opposite directions, thereby forming a pair of flanges 37.

[0095] The bottom portion 34 contacts the frame 23. The bottom portion 34 extends parallel to the Y direction.

[0096] The guide rail 31 is arranged to contact the frame 23 and the aerodynamic skin 24. The guide rail 31 can be fastened to the frame 23 by multiple bolts 36. Other fastening methods are possible, such as adhesive bonding, crimping, or any other method commonly used in the aerospace industry to fasten major structural components.

[0097] Reference Figure 5 The body structure 20, particularly the door assembly 30, may include a roller mechanism 40. The roller mechanism 40 is configured to support the door leaf 35 when it is installed.

[0098] The roller mechanism 40 may include a plurality of rollers 41. The rollers 41 are preferably arranged linearly along the guide rail 31. The rollers 41 may be bearing balls 42. The rollers 41 are preferably arranged such that they are exposed to the guide channel 32, so that the door leaf 35 can be supported by the rollers.

[0099] The roller mechanism 40 may include a plurality of roller support elements 43. Each roller support element 43 supports a plurality of rollers 41. The roller support element 43 may be an elongated profile. The roller support element 43 is preferably disposed on the sidewall portion 33.

[0100] The roller mechanism 40 may include one or more roller grooves 44, which may be formed on the door leaf 35. Figure 6 ) or on guide rail 31 ( Figure 9 The roller groove 44 is shaped to receive the roller 41 and allow the roller 41 to move easily within the roller groove 44. In addition, the roller groove 41 is preferably shaped to prevent lateral movement of the roller 41 relative to the side of the roller groove 41 (which corresponds to vertical movement relative to the fuselage structure 20).

[0101] Reference Figure 6 The body structure 20, particularly the door assembly 30, may include a locking mechanism 50, which is shown in an unlocked state. The locking mechanism 50 may include a plurality of locking recesses 51. The locking recesses 51 are preferably shaped to receive rollers 41. The locking recesses 51 may be formed to form a form engagement (also known as a form-fit engagement) with the rollers 41. Additionally or alternatively, the locking recesses 51 may be configured to form a friction engagement with the rollers 41. The locking recesses 51 are preferably formed within roller grooves 44.

[0102] The locking mechanism 50 may include movable roller support elements 52. Each movable roller support element 52 is configured to support the rollers 41 of the first set 54a such that the rollers 41 of the first set 54a can roll in the unlocked state. The movable roller support elements 52 are preferably arranged on one side of the guide rail 31 or guide channel 32, for example, on the side wall portion 33.

[0103] The locking mechanism 50 may include fixed roller support elements 53. Each fixed roller support element 53 is configured to support the rollers 41 of the second set 54b such that the rollers 41 of the second set 54b can roll in the unlocked state. The fixed roller support elements 53 are preferably arranged on opposite sides of the guide rail 31 or guide channel 32 relative to the movable roller support elements 52.

[0104] Now refer to Figure 2 , Figure 3 as well as Figures 6 to 8 The operation of door assembly 30 is described in more detail below. Initially, door assembly 30 is in the open position ( Figure 2 ), and the locking mechanism 50 is in the unlocked state ( Figure 6 In this configuration, the hydrogen tank 11 (or other equipment) can be accessed for maintenance through the fuselage opening 25. The door 35 is supported by guide rails 31 and can move linearly within the corresponding guide channels 32. In this configuration, the door 35 is laterally outside the tail section 31. This is achieved by configuring the guide rails 31 as telescopic rails similar to telescopic elements on a sliding drawer. Since the mechanism itself is well understood and known, it is not shown or explained in detail.

[0105] If a gust of wind strikes the door leaf 35 in this state, the force can be transmitted from the door leaf 35 to the frame 23 through the roller mechanism 40 and the guide rail 31. Thus, the door leaf 35 is firmly supported and can be prevented from moving due to the wind.

[0106] The door assembly 30 can be closed by manually moving the door leaf 35 along the guide rail 31. The door leaf 35 moves along the telescopic guide rail 31 until the door leaf 35 reaches the fully closed position. Figure 3 During movement, the door leaf 35 is again firmly supported against external, preferably lateral, forces, and the rollers 41 facilitate movement in the longitudinal direction.

[0107] As the travel of the door leaf 35 nears its end, the locking mechanism 50 can be actuated by an actuating member 55, which can be operatively coupled to the movable roller support element 52, for example via a known mechanical linkage or an electronic control system (neither shown for clarity). The actuating member 55 can push the movable roller support element 52 against the door leaf 35 via a first set 54a. Thus, the door leaf 35 is pushed outward along the lateral Y direction away from the center of the body opening 25. Consequently, the first set 54a is pushed into the locking recess 51 on the inner side of the door leaf 35. The door leaf 35 is pushed outward against the fixing member 31, which in this example is formed by a corresponding guide rail 31. The lateral movement of the door leaf 35 can further push the second set 54b into the locking recess 51 on the outer side of the door leaf 35, since the door leaf 35 can contact the fixed roller support element 53.

[0108] like Figure 8 As shown in more detail, the first group 54a and / or the second group 54b form a form-fit engagement with the door leaf 35. The door leaf 35 and the guide rail 31 are connected via a load-bearing joint 57, i.e., a joint capable of transmitting loads. Preferably, the load-bearing joint 57 is a bending joint 58. As indicated, if a force acting laterally on the door leaf 35 causes a bending force F... B Then these bending forces F B The door leaf 35 can be transferred to the frame 23 via the locking recess 51, the movable roller support element 52 and / or the fixed roller support element 53 and the guide rail 31. Therefore, the body structure 20 and the door assembly 30, especially the door leaf 35, are integrated in a bending-resistant manner.

[0109] It should be noted that, alternatively or additionally, the bearing joint 57 may be formed by friction engagement. For friction engagement, movable roller support elements 52 and / or fixed roller support elements 53 are pressed against the first group 54a and / or the second group 54b, such that friction between the respective roller support elements 52, 53 and the associated groups 54a, 54b prevents the respective rollers 41 from moving.

[0110] Reference Figure 9 and Figure 10 Another embodiment of the door assembly 30, which differs from the previous embodiment, will be described in more detail.

[0111] The locking mechanism 50 includes a first movable roller support element 52a and a second movable roller support element 52b. The first movable roller support element 52a and the second movable roller support element 52b are preferably disposed within the door leaf 35. The first movable roller support element 52a and the second movable roller support element 52b are each pivotable about an axis substantially parallel to the door leaf 35, i.e., in the longitudinal direction. The first movable roller support element 52a and the second movable roller support element 52b are spaced apart from each other in the transverse Y direction, for example, forming a gap 52c between them.

[0112] The locking mechanism 50 may also include an actuating member 55, which is preferably configured in the form of a wedge. The locking mechanism 50 may also include a control cam 56 configured to engage the actuating member 55 at a specific position.

[0113] Figure 9 The door assembly 30 is depicted in a near-closed position and in an unlocked state. In this configuration, the door leaf 35 is supported by a guide rail 31 and is movable within a guide channel 32. Roller grooves 44 and locking recesses 51 are provided on the guide rail 31, specifically on the side wall portion 33.

[0114] Figure 10 A door assembly 30 is depicted in the fully closed and locked position. During the movement of the door leaf 35 along the guide rail 31, an actuating member 55 can move with the door leaf 35. At a specific point in the travel of the door leaf 35, the actuating member 55 engages the control cam 56 and is pushed towards the center of the door leaf 35. The actuating member 55 is pushed into a gap 52c, causing the first movable roller support element 52a and the second movable roller support element 52b to pivot about a pivot axis, and pressing the corresponding first set 54a and second set 54b towards a fixed member, such as the guide rail 31. This creates a frictional engagement between the door leaf 35 and the guide rail 31 via the first set 54a and the second set 54b.

[0115] To unlock the locking mechanism 50 again, a considerable force exceeding the frictional locking force can be applied, even using some kind of lever. A release mechanism (not shown) may also be provided, which allows the control cam 56, and thus the actuating member 55, to move slightly, thereby allowing the first movable roller support element 52a and the second movable roller support element 52b to move again, along with the first set 54a and the second set 54b. It should be noted that such mechanisms are known and therefore are not shown or described in more detail herein.

[0116] List of reference numerals in the attached diagram:

[0117] 10 Aircraft

[0118] 11 Hydrogen Tanks

[0119] 20. Fuselage Structure

[0120] 21 Tail section

[0121] 21a Horizontal stabilizer

[0122] 21b Elevator

[0123] 21c Vertical stabilizer

[0124] 21d rudder

[0125] 22 Main body section

[0126] 23 Framework

[0127] 24 Aerodynamic Skin

[0128] 25. Fuselage opening

[0129] 30-door assembly

[0130] 31 Guide rail (fixed component)

[0131] 32 Guiding Channels

[0132] 33 Side wall portion

[0133] 34 Bottom section

[0134] 35 Door panels

[0135] 36 bolts

[0136] 37 Flange

[0137] 40 Roller Mechanism

[0138] 41 Roller

[0139] 42 bearing balls

[0140] 43 Roller support elements

[0141] 44 Roller Grooves

[0142] 50 Locking mechanisms

[0143] 51 Locking recess

[0144] 52 Movable roller support element

[0145] 52a First movable roller support element

[0146] 52b Second movable roller support element

[0147] 52c gap

[0148] 53 Fixed roller support element

[0149] 54a Group 1

[0150] 54b Group 2

[0151] 55 Actuating Components

[0152] 56 Control Cam

[0153] 57 Load-bearing joint

[0154] 58 Bending Joint

[0155] F B Bending force

Claims

1. A fuselage structure (20) of an aircraft (10), said fuselage structure (20) comprising: Multiple frames (23) extend along the circumferential direction of the fuselage structure (20); Aerodynamic skin (24), which is supported by the frame (23); At least one pair of guide rails (31) extending along the longitudinal direction of the fuselage structure (20) and supported by the frame (23) in a load-transfer manner, wherein each pair of guide rails (31) defines a fuselage opening (25). The guide rail (31) is configured to support the door leaf (35) in a sliding manner, so that the door leaf (35) can move along the longitudinal direction between a fully open position and a fully closed position. In the fully open position, the body opening (25) is not covered, and in the fully closed position, the body opening (25) is closed.

2. The body structure (20) according to claim 1 further includes a roller mechanism (40) disposed on the guide rail (31) and comprising a plurality of rollers (41) configured to engage the door leaf (35) to allow sliding movement of the door leaf (35).

3. The fuselage structure (20) according to claim 2, wherein, Each guide rail (31) includes at least one roller groove (44) configured to receive and support the roller (41) in a movable manner.

4. The fuselage structure (20) according to any one of the preceding claims further includes a locking mechanism (50) capable of switching between an unlocked state and a locked state, wherein in the unlocked state the installed door leaf (35) is movable, and in the locked state the movement of the installed door leaf (35) is prevented.

5. The fuselage structure (20) according to claim 4, wherein, The locking mechanism (50) is integrated into the roller mechanism (40) such that, in the locked state, the locking mechanism (50) applies force to the roller (41) to prevent movement by means of frictional engagement and / or form fit locking.

6. The fuselage structure (20) according to claim 4 or 5, wherein, In the unlocked state, the roller (41) is able to roll, and in the locked state, the roller (41) is forced against the guide rail (31), preferably against the side wall portion (33) of the guide rail (31), or forced toward the installed door leaf (35).

7. The fuselage structure (20) according to any one of the preceding claims, wherein, The guide rail (31) is configured such that a load-bearing joint (57) can be realized between the door leaf (35) guided in the guide rail (31) and the frame (23), and the load-bearing joint (57) can transmit bending loads and / or the load-bearing joint (57) includes or is composed of a bending joint (58).

8. The fuselage structure (20) according to claim 7, wherein, The bearing joint (57) is formed at least in the fully closed position, preferably at least partially by means of the locking mechanism (50) in the locked state.

9. The fuselage structure (20) according to any one of the preceding claims, wherein, Each guide rail (31) includes a pair of sidewall portions (33) and bottom portions (34) that define a guide channel (32) configured to receive and support a door leaf (35) in a sliding manner.

10. The fuselage structure (20) according to claim 9, wherein, The roller mechanism (40) and / or the locking mechanism (50) are disposed on at least one sidewall portion of the sidewall portion (33); and / or, wherein the roller mechanism (40) is disposed on at least one sidewall portion of the sidewall portion, wherein the locking mechanism (50), preferably the actuating member (55) of the locking mechanism (50) is partially disposed on the bottom portion (34).

11. The fuselage structure (20) according to claim 9 or 10, wherein, Each roller groove (44) is provided or formed on the sidewall portion (33).

12. A door assembly (30) of an aircraft (10), the door assembly (30) comprising a fuselage structure (20) according to any one of the preceding claims and a door leaf (35) supported for sliding in the guide rail (31).

13. The door assembly (30) according to claim 12, wherein, The door leaf (35) includes the roller mechanism (40) and partially includes the locking mechanism (50).

14. The door assembly (30) according to claim 12 or 13, wherein, The door panel (35) includes at least one roller groove (44) that movably receives and supports the roller (41).

15. An aircraft (10), preferably an airplane, the aircraft (10) comprising a fuselage structure (20) according to any one of claims 1 to 11 and / or a door assembly (30) according to any one of claims 12 to 14.

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