Retractable landing gear and aerial vehicle

Abstract

A retractable landing gear for an aerial vehicle, comprising: - a gear strut, to which one or more wheels are connected at a bottom thereof; and - a drop link arrangement, pivotably connected to an upper portion of the gear strut and to the aerial vehicle frame structure, wherein the pivot connection between the drop link arrangement and the aerial vehicles frame structure defines a first rotation axis, wherein the pivot connection between the drop link arrangement and the gear strut defines a second rotation axis that, in the deployed configuration, is inclined with ±5° to ±85° with respect to the first rotation axis, the first rotation axis and the second rotation axis positioned to swing the wheels of the gear, upon movement from the deployed configuration to the stowed configuration, or vice versa, and when seen from above, along a curved trajectory.

Description

[0001] Title: Retractable landing gear and aerial vehicle

[0002] BACKGROUND

[0003] The present disclosure relates to a retractable landing gear for an aerial vehicle. Virtually all aircraft that are designed to take off from and / or land on runways having a solid underground, employ a landing gear to safely do so. For some aircraft designed to fly at relatively low speeds, this landing gear is non-retractable. However, for virtually all aircraft designed to fly at Mach numbers higher than 0.3, the landing gear is retractable. A typical landing gear comprises a strut, within which a shock absorber may operate to absorb impact forces acting on the landing gear I the aircraft. Below the shock absorber, a landing gear bogie beam may be arranged, especially when the landing gear comprises a multitude of wheels mounted behind one another. The number of wheels may vary between one for the nose gear of a relatively light-weight aircraft, to, in extreme cases, fourteen for the main gear of relatively heavy-weight aircraft, although it is not excluded that more wheels may be employed in the future on even heavier aircraft than presently known.

[0004] For commercial aircraft, the gear struts of the landing gear are usually mounted directly to the airframe structure of the aircraft. It is quite common that the nose gear of the aircraft folds directly forwards compared to the deployed position, while the main gear of the aircraft fold directly inwards compared to the deployed position. The nose gear is usually arranged centrally with respect to the aircraft layout, so that the most storage space is available when it is folded forwards upon stowing the gear. An alternative may be to rotate it backwards, but this may be undesirable from a fail-mode perspective. For commercial aircraft having wings with conventional sweep angles, which may include a sweep angle of zero degrees, usually a spot below the wing can be found where the main gear may be mounted to fulfil all requirements and while allowing for inboard retraction kinematics, so that the wheels are stored in the aircrafts fuselage. Folding the gear forwards / backwards or inwards is relatively simple from the perspective of gear folding kinematics, so that the number of components of such a landing gear may be kept low. Virtually all contemporary large transport aircraft have wings with a relatively low sweep angle, or no sweep angle at all, so that the above-described sweet spot may easily be found.

[0005] For military aircraft, which may have larger sweep angles and / or a sleeker fuselage design, and the landing gears of which may be designed to withstand relatively higher load scenario’s (e.g. when landing on a carrier vessel or when landing on unsteady terrain), the folding mechanism may be more complicated and in some cases use is made of a so-called drop-link arrangement that is arranged in between the gear strut and the aircrafts’ frame structure. Using a drop-link arrangement, more complicated folding kinematics may be achieved compared to not using a drop-link arrangement, so that the gear may be stored in a more compact space and / or at a position deviating from directly forwards / rearwards or directly inboard. Examples of aircraft employing such a landing gear having a drop-link arrangement are the B-58 Hustler and the Rockwell B-1 B.

[0006] The present inventors have felt that there is a need for more freedom in design choices where it concerns the integration of the landing gear design in the design of an aerial vehicle. Specifically, the present inventors have felt that the relatively low number of presently-known gear retraction mechanisms hinders the design of quite radically different aircraft configurations and layouts, as presently-known gear retraction mechanisms may be incompatible with such new aircraft designs. For example, this specifically holds for aircraft configuration lacking a fuselage, as this is the “standard” place to stow the landing gear after retracting it. As such, there is a need for alternative landing gear retraction mechanisms.

[0007] SUMMARY OF THE DISCLOSURE

[0008] Accordingly, the present disclosure relates to a retractable landing gear for an aerial vehicle, the retractable landing gear moveable between a deployed configuration and a stowed configuration and comprising: a gear strut, to which one or more wheels are connected at a bottom thereof; and a drop link arrangement, pivotably connected to an upper portion of the gear strut with one end thereof and to the aerial vehicle frame structure with the other end thereof, wherein the pivot connection between the drop link arrangement and the aerial vehicles frame structure defines a first rotation axis, wherein the pivot connection between the drop link arrangement and the gear strut defines a second rotation axis that, in the deployed configuration, is inclined with ±5° to ±85° with respect to the first rotation axis, the first rotation axis and the second rotation axis positioned to swing the wheels of the gear, upon movement from the deployed configuration to the stowed configuration, or vice versa, and when seen from above, along a curved trajectory.

[0009] It should be explicitly noted that, although the design as presented herein stems from the realisation that present landing gear retraction mechanisms may be unsuitable for “non-standard” aircraft configurations, in particular for aircraft configurations lacking a fuselage and / or having limited stowage space, such as the Flying-V configuration, the reverse of that statement, that the landing gear as disclosed herein is only suited for “non-standard” aircraft configurations, is not true. In other words, the landing gear as disclosed herein may well be suited, and even advantageous, also for standard aircraft configurations, irrespective of whether it is a “civil” aircraft, such as a commercial plane or a private plane configuration or a military aircraft, including military trainer aircraft.

[0010] Advantageously, the two different rotation axes for the landing gear components, resulting in a curved movement trajectory for the wheels and a net movement vector thereof that is inclined with respect to both the roll axis and the pitch axis of the aerial vehicle allows the landing gear to be (partially) stowed inside the wings of an aerial vehicle having a high sweep angle. It is noted that although commonly the landing gear is stowed below the fuselage of an aerial vehicle, alternative aircraft configurations are being investigated by several research groups throughout the world. Some of these alternative configurations lack a traditional fuselage, and thus a traditional landing gear bay in said fuselage. One highly promising example of such alternative aircraft configurations is the “Flying-V” concept that is being developed by the applicant. As such, the landing gear concept as described herein can be optimally integrated with a Flying-V aircraft by stowing the landing gear (partially) inside the wings and folding the gear in a non-traditional direction.

[0011] Advantageously, the two different rotation axes for the landing gear components allows to obtain a net movement vector of the wheels that is inclined with respect to both the roll axis and the pitch axis of the aerial vehicle while minimizing the number of components needed to deploy I stow the gear. Less components in general lead to a lower price, a faster assembly time, less maintenance, a higher reliability, a higher robustness, a lower weight and easier maintenance.

[0012] A further advantage of using a drop-link arrangement is that this allows the gear to be folded I stowed in a very compact space, so that the drag-incurring landing gear bay can be minimized in dimensions.

[0013] According to the present disclosure, the retractable landing gear comprises a drop link arrangement. As described in the background portion of the present disclosure, the use of a drop-link arrangement as such is not new. However, the orientation of the rotation axes thereof is deemed novel. Advantageously, by using a drop-link arrangement, when designing a family of aircraft the length of the drop-link arrangement and the gear strut may be adapted for family derivatives while the rest of the gear, the design of the stowage bay and the portion of the wing it belongs to all remain the same on each derivative design. This reduces manufacturing and design costs on a family-level, although it may lead to relatively minor imperfections on a single-aircraft level. By family of aircraft is meant similar aircraft designed to seat a different number of passengers I optimized for a different mission profile (like the Airbus A318 through A321) .

[0014] According to the present disclosure, the drop link arrangement deploys and retracts via a rotation about a first rotation axis and a second rotation axis. The first rotation axis is defined at the position where the drop link arrangement is connected to the frame structure of the aerial vehicle; the second rotation axis is defined at the position where the drop link arrangement is connected to the gear strut. The two axes are inclined with respect to each other. As rotation about the first rotation axis is effected, the second rotation axis moves. When a rotation about both axes is effected at the same time, a complex 3D curved movement for the lower parts of the gear, i.e. the wheels, is obtained. This will be described and shown in more detail with reference to the description of the Figures and the Figures themselves.

[0015] According to the present disclosure, the net movement vector of the wheels may be inclined with respect to both the aerial vehicle’s roll axis and the aerial vehicle’s pitch axis. For example, for backward sweep wings, compared to the deployed position, in the stowed position the wheels may be arranged inboard and forward, or outboard and rearward. For forward sweep wings, compared to the deployed position, in the stowed position the wheels may be arranged inboard and rearward, or outboard and forward.

[0016] In an embodiment of the present disclosure, the landing gear further comprises a brace member, connected to the aerial vehicle’s frame structure and the gear strut, for limiting the movement of the wheels upon their movement from the deployed configuration to the stowed configuration, and vice versa. The addition of a brace member preferably limits the movement of the wheels in the sense that it allows for just a single degree of freedom where the retraction I deployment kinematics are concerned, so that there is only one path the gear can follow between the deployed and stowed position (and vice versa).

[0017] In an embodiment of the present disclosure, the net movement vector is inclined at an angle of more than 20 degrees with respect to both the aerial vehicle’s pitch axis and the aerial vehicle’s roll axis. For example, the net movement vector described by the wheels may substantially correspond to the sweep angle of the wing’s rear spar.

[0018] In an embodiment of the present disclosure, the net movement vector of the wheels from deployed position to stowed position points inboards as well as forwards. This may allow to store the gear inside the wing, e.g. behind the rear spar of the wing structure instead of below the fuselage of the aerial vehicle - e.g. because there is no fuselage.

[0019] In an embodiment of the present disclosure, a top portion of the gear strut is T- shaped and the drop link arrangement comprises two linking members connected to the gear strut, the gear strut having connection points at each radial end of the T- shape for pivotably connecting the respective linking members to the gear strut. When one linking member is arranged on each side of the landing gear strut, the forces acting on the entire arrangement may be distributed effectively, in particular with regard to torsion loads.

[0020] In an embodiment of the present disclosure, the retractable landing gear comprises 4 or more wheels. In particular, in such cases, the landing gear may be a main gear. In such embodiments, the number of wheels is preferably an even number, with the wheels e.g. being arranged in a tandem or side-by-side configuration. Nonlimiting examples of such configurations include a 2x2, 2x3, 3x2, 4x2, 2x4 and 3x3 configuration. Especially for relatively large gear, e.g. gear employing a tandem configuration, the problem of insufficient stowage space may be recognized. As such, the retraction kinematics as disclosed herein may be especially advantageous for such configurations.

[0021] In alternative embodiments, the retractable landing gear may comprise two wheels that are arranged next to each other below the landing gear strut.

[0022] In an embodiment of the present disclosure, the gear strut defines a main landing gear strut. In an alternative embodiment, the gear strut defines a nose landing gear strut.

[0023] In an embodiment of the present disclosure, the brace member is connected to the gear strut at a lower portion thereof, e.g. nearer to the point where the landing gear bogie beam is connected to the strut than to the point where the drop-link arrangement is connected to the strut. In particular, the brace member may be connected to the (stationary) gear strut instead of to another component of the landing gear.

[0024] The present disclosure further relates to an aerial vehicle comprising the retractable landing gear as described in the above. In particular, said aerial vehicle may have a wing sweep angle of more than 40 degrees. For example, said aerial vehicle may lack a classical fuselage, so that the aerial vehicle may e.g. be of the “flying wing” and / or the “Flying-V” type.

[0025] BRIEF DESCRIPTION OF THE DRAWINGS

[0026] These and other embodiments of the present disclosure are elucidated further with reference to the attached Figures. In these Figures, the same and like components are indicated with the same reference numerals. In the figures: Fig. 1A - 1 D schematically show, in a view from behind, the folding mechanism of a first exemplary embodiment of the retractable right main landing gear according to the present disclosure;

[0027] Fig. 2A - 2D schematically show, in a view from the side, the retractable right main landing gear of Figs. 1A - 1 D at the same time instances as in these figures;

[0028] Fig. 3A - 3D schematically show, in a view from above, the folding mechanism of a second exemplary embodiment of the retractable right main landing gear according to the present disclosure; and

[0029] Fig. 4A - 4D schematically show, in an isometric view, the retractable right main landing gear of Figs. 3A - 3D at the same time instances as in these figures.

[0030] DETAILED DESCRIPTION OF THE DRAWINGS

[0031] As will be understood by one skilled in the art, landing gear kinematics are highly complex and involve the rotation of several parts, both with respect to each other as with respect to the original position, in 3D space. Although this may be difficult to illustrate in static figures, the applicant has performed the utmost care in detailing the inventive concept as disclosed herein as good as possible using static figures only. For that purpose, four different views of two different embodiments of the present disclosure are shown. In the below, all figures will be described at the same time, but first the relation of the different figures with respect to each other will be explained.

[0032] Figures 1 A - 1 D and 2A - 2D show a first embodiment of the retractable landing gear 1 as defined in the claims. Figures 3A - 3D and 4A - 4D show a second embodiment of the retractable landing gear 1 as defined in the claims, the second embodiment differing from the first embodiment in that for the second embodiment linking members 8 are shown, which are absent from the retractable landing gear 1 according to the first embodiment.

[0033] The respective figures 1 / 2 / 3 / 4A - 1 / 2 / 3 / 4D show different “instances” of the folding kinematics that are carried out in folding the retractable landing gear 1 from a deployed position (respective figures A) to a stowed position (respective figures D), as well as two intermediate positions. As will be understood by one skilled in the art, when the gear is deployed from a stowed position, the “steps” shown in Figures 1 / 2 / 3 / 4A-D are taken in the reverse order.

[0034] Apart from the folding members 8, the embodiment of the first set of figures is identical to the embodiment of the second set of figures. Of course, one skilled in the art will understand that the invention as described herein is not limited to this specific set-up or layout. The scope of protection is defined by the claims, and the claims only. The figures are merely to show two exemplary embodiments of the invention, while the person skilled in the art, using the information disclosed herein, may think of a vast multitude of alternative designs, all falling within the scope of the appended claims.

[0035] That being said, the figure series 1A - 1 D shows the retractable landing gear 1 as it is being retracted from a deployed position to a stowed position, in a view from behind. The figure series 2A - 2D shows the same landing gear 1 , at the same snapshots of the folding sequence, but in a view from the side. The figure series 3A - 3D shows the landing gear 1 , inclusive of the folding members 8, at the same snapshots of the folding sequence as for figures 1 and 2, in a view from above. The figure series 4A - 4D, finally, shows the landing gear again in the same snapshots of the folding sequence as for the previous figures. The gear depicted is a right main gear. The same principles may be applied on a left main gear and / or on a nose gear.

[0036] In figures A, the landing gear 1 is in the deployed configuration, with all wheels 7 able to contact a ground surface and a shock absorber 5 retracted inside the strut 3. The strut 3, which is T-shaped, is connected to a frame structure of a (non-shown) aerial vehicle through drop-link arrangement 2. To that end, the drop link arrangement 2 includes a pair of outer linking members 8 that are each pivotably connected to one radially outer end of the top bar of the gear strut 3, at respective connection points. While the drop link arrangement 2 is thus mounted to the gear strut 3 near a top end thereof, the brace member 4 is mounted to the gear strut 3 at a lower end thereof. These mounting locations are however, as will be understood by one skilled in the art, optional and non-mandatory.

[0037] The retractable landing gear 1 further comprises a brace member 4, which is like the drop-link arrangement 2 at one end pivotably connected to the gear strut 3 and with the other end pivotably connected to the frame structure of the aerial vehicle. Further components of the landing gear 1 may include a bogie beam 6, in particular when there are more than two wheels 7. In the presently shown embodiments the landing gear 1 comprises four wheels 7, arranged in a 2x2 tandem configuration. Of course, it will be understood by one skilled in the art that the number of wheels is in no way limiting for the inventive concept as disclosed herein.

[0038] As will become more clear in the below and with respect to the B series of figures and the C series of figures in particular, the drop-link arrangement 2 rotates about a first rotation axis R1 when retracting and deploying. As shown perhaps most clearly in the view from the back, i.e. Figure 1A, the first rotation axis R1 is inclined with respect to both the pitch axis Y of the aerial vehicle and the roll axis X of the aerial vehicle. As perhaps shown most clearly in Figure 1A as well, the first rotation axis R1 is inclined with respect to the aircraft yaw axis Z as well. As should be understood by one skilled in the art, depending on the desired stow position, and the exact design / configuration of the landing gear 1 , the precise inclination angle of the first rotation axis R1 in 3D space may be more of less similar to what is shown here in Figures A.

[0039] As will become more clear in the below and with respect to the B series of figures and the C series of figures in particular, the second rotation axis R2 is defined by the line through which gear strut 3 and drop-link arrangement 2 connect. The landing gear rotates about this second rotation axis R2when retracting and deploying. The orientation of this second rotation axis R2 is dynamic, as it moves through space when the drop-link arrangement 2 rotates about the first rotation axis R1 . The brace member 4 limits the movement freedom of the gear 1 resulting in simultaneous rotations about the first rotation axis R1 and the second rotation axis R2. Without brace member 4, these rotations could be independent and uncoupled. As shown perhaps most clearly in the view from the back, i.e. Figure 1A, the second rotation axis R2 is inclined with respect to both the pitch axis Y of the aerial vehicle and the roll axis X of the aerial vehicle. As perhaps shown most clearly in Figure 1A as well, the second rotation axis R2 is inclined with respect to the aircraft yaw axis Z as well. As shown perhaps most clearly in Figures 2A and 4A, the second rotation axis R2 is further inclined with respect to the first rotation axis R1. As should be understood by one skilled in the art, depending on the desired stow position, and the exact design / configuration of the landing gear 1 , the precise inclination angle of the second rotation axis R2 in 3D space may be more of less similar to what is shown here in Figures A.

[0040] Turning our attention now to Figures 1 B / 2B / 3B / 4B, folding of the retractable landing gear 1 away from the deployed position has partially taken place. It should be noted that, throughout the folding sequence, rotation takes place about the first rotation axis R1 and the second rotation axis R2 at the same time, although this may not be required for every possible embodiment of the present disclosure. As shown perhaps best in Figures 1 and 3, the movement from Figures series A to figure series B is in the present embodiment both upwards and inwards. It should however be repeated explicitly that the precise movement as shown in the figures is non-limiting to the inventive concept as described in the claims.

[0041] Turning our attention to Figures 1C / 2C / 3C / 4C and 1 D / 2D / 3D / 4D now, it may be observed that upon further rotation of the drop-link arrangement 2 about the respective rotation axis R2, R1 , an end, stowed, position may be obtained for the gear that is, compared to the deployed position, at a net inclination with respect to the aerial vehicle’s pitch axis Y, it’s roll axis X and it’s yaw axis Z. This may be seen especially well on the sequence shown in the top views of Figures 3A - 3D, where the wheels 7 of the gear 1 are rotated both inboards and forwards with respect to the deployed position. Further noteworthy is that the wheels 7 have carried out a 90 degree rotation in the stowed position compared to the deployed position. This is perhaps best visible from the series of figures 1 A - 1 D, where it is seen that the wheels 7 that are arranged side-by-side in the deployed position are arranged on top of each other in the stowed position.

[0042] As perhaps best visible from the folding sequence shown in Figures 3A - 3D, the top view, from the perspective of the wheels 7 of retractable landing gear 1 the swinging movement from deployed position in figure 3A to stowed or retracted position in figure 3D is non-linear and may prescribe a curved trajectory.

Claims

CLAIMS1. A retractable landing gear for an aerial vehicle, the retractable landing gear moveable between a deployed configuration and a stowed configuration and comprising: a gear strut, to which one or more wheels are connected at a bottom thereof; and a drop link arrangement, pivotably connected to an upper portion of the gear strut with one end thereof and to the aerial vehicle frame structure with the other end thereof, wherein the pivot connection between the drop link arrangement and the aerial vehicles frame structure defines a first rotation axis, wherein the pivot connection between the drop link arrangement and the gear strut defines a second rotation axis that, in the deployed configuration, is inclined with ±5° to ±85° with respect to the first rotation axis, the first rotation axis and the second rotation axis positioned to swing the wheels of the gear, upon movement from the deployed configuration to the stowed configuration, or vice versa, and when seen from above, along a curved trajectory.

2. The retractable landing gear according to claim 1 , further comprising a brace member, connected to the aerial vehicle’s frame structure and the gear strut, for limiting the movement of the wheels upon their movement from the deployed configuration to the stowed configuration, and vice versa.

3. The retractable landing gear according to claim 1 or 2, wherein, when seen from above, a net movement vector of the wheels is inclined at an angle of more than 20 degrees with respect to both the aerial vehicle’s pitch axis and the aerial vehicle’s roll axis.

4. The retractable landing gear according to claim 3, wherein the net movement vector points inboard as well as forwards with respect to the deployed position of the gear.

5. The retractable landing gear according to any one of the preceding claims, wherein a top portion of the gear strut is T-shaped and the drop link arrangement comprises two linking members connected to the gear strut, the gear strut having connection points at each radial end of the T-shape for pivotably connecting the respective linking members to the gear strut.

6. The retractable landing gear according to any one of the preceding claims, comprising 4 or more wheels.

7. The retractable landing gear according to claim 6, wherein the wheels are arranged in a tandem configuration, such as a 2x2 or a 3x2 configuration.

8. The retractable landing gear according to any one of the preceding claims, wherein the gear strut defines a main landing gear strut.

9. The retractable landing gear according to any one of the preceding claims 2 - 8, wherein the brace member is connected to the gear strut at a lower portion thereof.

10. An aerial vehicle comprising the retractable landing gear according to any one of the preceding claims.

11. The aerial vehicle according to claim 10, wherein wings of the aircraft have a wing sweep angle of more than 40 degrees.

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