SE1650457A1

SE1650457A1 - Landing gear and vtol aircraft comprising such landing gear

Info

Publication number: SE1650457A1
Application number: SE1650457A
Authority: SE
Inventors: Fång Jonas; Meijer Claes
Original assignee: Cybaero Ab
Priority date: 2016-04-05
Filing date: 2016-04-05
Publication date: 2017-10-06

Abstract

The present disclosure provides a landing gear (15) for a vertical take-off and landing aircraft. The landing gear comprises a ground engaging. member (151), adapted for engaging a support on which the aircraft is to land or take off, a mounting base (152a, 152b), attachable to, or forming part of, an aircraft fuselage (11), and across beam (153a, 153b, 153c, 153d) connecting the ground engaging member (151) to the mounting base (152a, 152b). The. landing gear further comprises a parallel linkage mechanism (154, 155) connected between the mounting base and the cross beam, such that a proximal end of the cross beam is movable substantially vertically relative to the mounting base, and a shock absorber (156) arranged to control said relative movement between the cross beam and the mounting base.

Description

LANDING GEAR AND VTOL AIRCRAFT CONIPRISING SUCH LANDINGGEAR Technical field The present disclosure relates to a landing gear for a vertical take-offand landing aircraft and in particular for a helicopter.

The landing gear disclosed herein finds particular application in thefield of unmanned aircraft, specifically unmanned helicopter.

Backgroundln connection with landing, aircraft landing gears are subjected to severe forces when connecting with the support on which the aircraft lands.

Hence, it is generally known to provide shock absorption mechanismfor reducing the impact on the aircraft fuselage and thus also the forces actingon the landing gear.

One shock-absorbing landing gear is known from EP2641831A1. Adisadvantage of this landing gear is that when it is subjected to a high impactforce, the skids will be forced away from each other. When rebounding, thismay cause the entire aircraft to move sideways in an unpredictable manner,partly depending on the friction available between the respective skid and thesupport. There is also a risk of the skids moving unpredictably while theaircraft, due to its inertia, remains stationary. ln either case, there is a risk ofdamaging the aircraft and/or the support, as well as of injuring operators in oraround the aircraft.

These problems may have particular significance in the case ofunmanned aerial vehicles (“UAV”), since they often land more roughlybecause the operator, if any, does not ride in the vehicle, and since theysometimes land on portable platforms. l\/loreover, as today”s VTOL UAVs are generally smaller thanconventional helicopters, and thus have less lifting capacity, the landing gearmust be made very light.

Hence, there is a need for an improved shock absorbing |anding gearfor VTOL aircrafts.

SummaryAn object of the present disclosure is to provide an improved shock absorbing |anding gear. Such a |anding gear should, in addition to providingsufficient shock absorption, be possible to manufacture in a cost efficientmanner. |\/|oreover, such a |anding gear should be possible to make very light.

The invention is defined by the appended independent claim, withembodiments being set forth in the appended dependent claims, in thefollowing description and in the attached drawings.

According to a first aspect, there is provided a |anding gear for avertical take-off and |anding aircraft, comprising a ground engaging, adaptedfor engaging a support on which the aircraft is to land or take off, a mountingbase, attachable to, or forming part of, an aircraft fuselage, and a cross beamconnecting the ground engaging to the mounting base. The |anding gearfurther comprises a parallel linkage mechanism connected between themounting base and the cross beam, such that a proximal end of the crossbeam is movable substantially vertically relative to the mounting base, and ashock absorber arranged to control said relative movement between the crossbeam and the mounting base.

A shock absorber may comprise a resilient device and/or a damperdevice. These devices may be integrated into a single unit, or provided asseparate units.

By using a parallel linkage mechanism, the horizontal movement of theskids during the compression and rebound will be reduced, thus reducing therisk of damage or injury. |\/|oreover, the decrease in sideways movement is advantageous as itmakes the forces acting on the |anding gear less dependent on the frictionbetween the |anding gear and the support on which the vehicle lands, andthus more predictable.

The parallel linkage mechanism may comprise an upper link member,which is pivotably connected to the mounting base at a first joint and which is pivotably connected to the cross beam at a second joint; and a lower linkmember, which is pivotably connected to the mounting base at a third jointand which is pivotably connected to the cross beam at a fourth joint.

The shock absorber may, at its connection to the mounting base, bepivotable about an axis which coincides with the first joint.

I\/|oreover, the shock absorber may, at its connection to the crossbeam, be pivotable about an axis which coincides with the fourth joint.

One of the upper and lower link members may comprise a pair ofseparate members, which extend in parallel and which are connected to thefirst and second joints, or to the third and fourth joints.

One of the upper and lower link members may comprise an integratedlink member, which is connected to the first and second joints, or to the thirdand fourth joints, and which provides a pair of spaced apart connectingportions, between which a connecting portion of the cross member and/or ofthe mounting base is receivable.

The cross member may comprise an elongate member having atransversely extended portion, which forms a connecting point for the secondjoint and/or for the fourth joint.

The transversely extended portion may be formed as a separate partthat is attached to the elongated member.

The ground engaging member may comprise a skid.

The skid may interconnect at least two cross members.

The landing gear may comprise a pair of substantially parallel skids,each connected with a respective cross member, preferably each connectedto a pair of cross members.

The ground engaging member may, alternatively, or as a supplement,comprise at least one foot.

A foot may be a very short skid-like structure. Alternatively, it may besubstantially rectangular, oval or disc shaped.

The landing gear may comprise at least two cross members which arerotatable relative to the mounting base about substantially parallel axes, andat least one cross member which is rotatable about an axis which forms an angle of 45°-135°, preferably 80°-100° or about 90°, to the axes of said atleast two cross members.

The cross member may be substantially straight and in an unloadedstate form an angle greater than 30°, preferably greater than 40° or greaterthan 50°, to a horizontal plane.

According to a second aspect, there is provided a vertical take-off andlanding aircraft comprising a landing gear as described above.

Such aircraft may comprise at least one rotor arranged to generate alifting force.

The aircraft may be an unmanned aerial vehicle. ln such an aircraft, a landing gear height, from skid to a lowest point ofa fuselage may be greater than 50 °/> of a distance between the skids,preferably greater than 75 °/> of the distance between the skids.

Brief description of the drawinosFig. 1 is a schematic side view of a VTOL aircraft.

Figs 2a-2c schematically illustrate a version of a landing gear.

Figs 3a-3b schematically illustrate a second version of the landinggear Fig. 4 illustrates a version of the landing gear having feet instead ofskids.

Fig. 5 illustrates a tripod version of the landing gear.

Figs 6a-6b illustrate a single damper version of the landing gear.

Detailed descriptionReferring to Fig. 1, there is illustrated a VTOL aircraft in the form of a helicopter 1 comprising a fuselage 11 and a tail boom 12, a main rotor 13, atail rotor 14 and a landing gear 15.

The helicopter is only for illustration purposes, and it is recognized thatthe present disclosure may be applied to any type of VTOL aircraft, and inparticular to VTOL aircraft that comprise at least one lift generating rotor.

The landing gear 15 is indicated as comprising skids. lt is understoodthat such skids may be provided with auxiliary wheels, i.e. fixed or casterwheels that are mounted to the skids in order to facilitate manual handling ofthe aircraft while on the ground.

Referring to Figs 2a-2c, there is illustrated a landing gear 15comprising a pair of skids 151, four cross members 153 and a pair ofmounting bases 152. ln the illustrated design, two cross members 153a, 153bform front cross members and connect to a front mounting base 152a. l\/loreover, two cross members 153c, 153d form rear cross membersand connect to a rear mounting base 152b.

At each connection between cross member 152a-152d and mountingbase 152a, 152b, there is a parallel linkage mechanism comprising arespective upper link 154 and a respective lower link 155. Each parallellinkage mechanism is provided with a shock absorber 156, which maycomprise a damper mechanism and a spring mechanism, which operate inparallel, such that any motion between the cross member 153a-153d and themounting base 152a, 152b is dampened and biased towards a predeterminedposition.

Referring to Fig. 2b, each parallel linkage mechanism may beconstituted as follows.

A proximal end 1541 of the upper link 154 is pivotably connected to themounting base 152a via a first joint 157a. This joint 157a may be formed asan axle which extends through the proximal end of the upper link and throughthe mounting base 152a. Optionally, this axle may extend also through aproximal end of a damper member 156.

The upper link 154 may be provided by a pair of separate linkmembers, as illustrated in Fig. 2a. Thus the axle forming part of the joint 157amay extend through proximal end portions of both such link members.

A distal end 1542 of the upper link 154 is pivotably connected to anupper or proximal end of the cross member 153a-153d via a second joint157b. ln the illustrated example, this connection is provided at a proximalextreme of the cross member. This joint 157b may be formed as an axle which extends through the distal end of the upper link 154 and throughproximal end of the cross member 153a-153d.

Where the upper link is provided by a pair of separate members, theaxle forming part of the joint 157b may extend through distal portions of bothsuch separate members.

As an option, the upper link 154 may be provided by a pair of memberswhich are connected to each other to form generally a V or an H, e.g. bybeing formed in one piece of material.

A proximal end 155a of the lower link 155 is pivotably connected to themounting base 152a via a third joint 157c. This joint 157c may be formed asan axle which extends through the proximal end of the upper link and throughthe mounting base 152a.

The third joint 157c may be provided at a portion of the mounting base152a, 152b, which is at a lower vertical level than the first joint 157a.

The lower link 155 may be provided by a pair of separate linkmembers, or by an integrated link member, which comprises two portions thatextend in parallel, as illustrated in Fig. 2a. Thus the axle forming part of thejoint 157c may extend through proximal end portions of both such portions.

A distal end 1552 of the lower link 155 is pivotably connected to anupper or proximal end of the cross member 153a-153d via a fourth joint 157d.

The fourth 157d joint may be positioned at a lower vertical level thanthe second joint 157b. ln the illustrated example, this connection is provided at a transverselyextended portion 1531 of the cross member.

As a non-limiting example, the cross member may be provided by anelongate rod or tube having a substantially constant cross section, with thetransversely extended portion being formed as a wedge, which is attachedalong an upper portion of the cross member 153a-153d, such that it tapersdownwardly towards the skids 151.

This fourth joint 157d may be formed as an axle which extends throughthe distal end of the lower link 155 and through the proximal end of the crossmember 153a-153d.

Where the lower link 155 is provided by a pair of members, these maybe connected to each other to form generally a V or an H, e.g. by beingformed in one piece of material.

Where the lower link 155 is instead provided by a pair of separatemembers, the axle forming part of the joint 157d may extend through distalportions of both such separate members.

The damper unit 156 may be formed as an integrated damper/springunit or as separate damper and spring units. Preferably, dampercharacteristics may be adjustable, for compression and/or for reboundmovements. ln the illustrated example, there is provided a single damper unit 156for each cross member 153a-153d. ln such case, a proximal portion 1561 ofthe damper unit 156 may be connected to the mounting base 152a, 152b, forexample, but not necessarily, in the vicinity of the first joint 157a. ln theillustrated example, the proximal portion of the damper unit is connected tothe axle forming part of this first joint 157a.

As another alternative, the proximal portion of the damper unit 156 maybe connected to a proximal portion of the upper link 154.

A distal portion 1562 of the damper unit 156 may be connected to theproximal portion of the cross member 153a-153d, for example, but notnecessarily, in the vicinity of the fourth joint 157d. ln the illustrated example,the distal portion 1562 of the damper unit 156 is connected to the axleforming part of this fourth joint 157d.

As another alternative, the distal portion 1562 of the damper unit 156may be connected to a distal portion of the lower link 155.

As another option, the damper unit may operate between an axleforming part of one of the second and the fourth joints 157b, 157d and anarbitrary point of the mounting base 152a, 152b, so long as the damper unit156 does not operate in parallel with any of the links 154, 155.

Figs 3a-3b illustrate another version of the landing gear, wherein themounting base 152a”, 152b' and the cross members 153a”-153d” have adifferent design. Other parts of the landing gear are identical to those of theversion illustrated in Figs 2a-2c.

Referring to Fig. 3b, it can be seen that the cross members 153a”-153d' are integrated with the respective transversely extended portion 1531 ”_I\/|oreover, the cross members have a width which tapers in the directiontowards the skids 151, i.e. towards dista| portions of the cross members.

I\/|oreover, proximal portions of the cross members are generallycurved or angled relative to the dista| portions of the cross members. Thisbent or angled portion may extend over less than 50 °/> of a length of thecross member, preferably over less than 25 °/> or over less than 20 °/> of thelength.

The proximal portions of the cross members may present a respectivewidened portion, which may be bifurcated so as to provide a pair of verticallyspaced apart attachment portions at which the links 154, 155 may beaüached.

Referring to Fig. 4, there is illustrated a landing gear, which is designedlike the one illustrated in Figs. 3a-3b, but which, instead of skids comprisesfeet 151 ”_ Each foot may have an arbitrary shape. ln the illustrated example,each foot 151' has the form of a short skid, which only attaches to a singleone of the cross members 153a”-153d”.

The feet may be given any shape and they may even beexchangeable. For example, the shape of the foot may be different dependingon what support the vehicle is intended to land on, such as on a hard, smoothbase, e.g. on tarmac or on a ship; or on a softer and/or uneven base, e.g. ona field or on a lawn.

Referring to Fig. 5, there is illustrated a landing gear which is providedwith three feet 151a”, 151b',151e”.

A first pair of feet 151a”, 151b' may be designed indentical to a pair offeet as described with respedt to Fig. 4, while the third foot may, as such, alsobe designed in this manner, but turned about 90° around a vertical axisrelative ot the other feet. For example, this third foot 151e' may extendrearwardly while the other two feet 151a”, 151b” form front feet, or vice versa.

Referring to Figs 6a-6b, there is illustrated a landing gear wherein asingle damper is used to provide the dampening action.” ln this landing gear, the skids 151 (or feet, as the case may be), thecross members 153a”-153d” and the base 152a' may be designed asdescribed above.

However, instead of connecting the damper 156' between a proximalportion of the cross member or a link and the base member or the other link,the damper may be connected between a pair of lower links 155” (asillustrated) or between a pair of upper links 154 (not shown).

Hence, each link, in this case the lower links, may be provided with adamper mounting portion 1553, which may be provided as a portion whichprotrudes out of a plane defined by the joint axes 157a, 157b; 157c, 157dassociated with that link, and which provides connection joint 1554 to whichthe damper 156' may be attached, preferably rotatably attached. ln such an embodiment, it may be advantageous to provide a stabilizeror anti-roll device.

Claims

CLAIIVIS

1. A landing gear (15) for a vertical take-off and landing aircraft,comprising: a ground engaging member (151), adapted for engaging a support onwhich the aircraft is to land or take off, a mounting base (152a, 152b), attachable to, or forming part of, anaircraft fuselage (11), and a cross beam (153a, 153b, 153c, 153d) connecting the groundengaging member (151) to the mounting base (152a, 152b), characterized by a parallel linkage mechanism (154, 155) connected between themounting base and the cross beam, such that a proximal end of the crossbeam is movable substantially vertically relative to the mounting base, and a shock absorber (156) arranged to control said relative movementbetween the cross beam and the mounting base.

2. The landing gear as c|aimed in c|aim 1, wherein the parallelIinkage mechanism comprises: an upper link member (154), which is pivotably connected to themounting base at a first joint (157a) and which is pivotably connected to thecross beam at a second joint (157b); and a lower link member (155), which is pivotably connected to themounting base at a third joint (157c) and which is pivotably connected to thecross beam at a fourth joint (157d).

3. The landing gear as c|aimed in c|aim 2, wherein the shockabsorber, at its connection to the mounting base, is pivotable about an axiswhich coincides with the first joint (157a).

4. The landing gear as c|aimed in c|aim 2 or 3, wherein the shockabsorber, at its connection to the cross beam, is pivotable about an axiswhich coincides with the fourth joint (157d). 11

5. The landing gear as claimed in any one of c|aims 2-4, whereinone of the upper and lower link members (154, 155) comprises a pair ofseparate members, which extend in parallel and which are connected to thefirst and second joints (157a, 157b), or to the third and fourth joints (157c,157d).

6. The landing gear as claimed in any one of c|aims 2-5, whereinone of the upper and lower link members (154, 155) comprises an integratedlink member, which is connected to the first and second joints, or to the thirdand fourth joints, and which provides a pair of spaced apart connectingportions, between which a connecting portion of the cross member and/or ofthe mounting base is receivable.

7. The landing gear as claimed in any one of the preceding c|aims,wherein the cross member (153a, 153b, 153c, 153d) comprises an elongatemember having a transversely extended portion (1531), which forms aconnecting point for the second joint (157b) and/or for the fourth joint (157d).

8. The landing gear as claimed in claim 7, wherein the transverselyextended portion (1531) is formed as a separate part that is attached to theelongate member.

9. The landing gear as claimed in any one of the preceding c|aims,wherein the ground engaging member comprises a skid.

10. The landing gear as claimed in claim 9, wherein the skidinterconnects at least two cross members.

11. The landing gear as claimed in claim 9 or 10, wherein thelanding gear comprises a pair of substantially parallel skids (151), eachconnected with a respective cross member.

12. The landing gear as claimed in any one of the preceding c|aims,wherein the ground engaging member comprises at least one foot. 12

13. The landing gear as claimed in any one of the preceding claims,wherein the landing gear comprises at least two cross members which arerotatable relative to the mounting base about substantially parallel axes, andat least one cross member which is rotatable about an axis which forms anangle of 45°-135°, preferably 80°-100° or about 90°, to the axes of said at least two cross members.

14. The landing gear as claimed in any one of the preceding claims,wherein the cross member is substantially straight and in an unloaded stateforms an angle greater than 30°, preferably greater than 40° or greater than50°, to a horizontal plane.

15. A vertical take-off and landing aircraft (1) comprising a landinggear as claimed in any one of the preceding claims.

16. The aircraft as claimed in claim 11, wherein the aircraftcomprises at least one rotor (13) arranged to generate a lifting force.

17. The aircraft as claimed in claim 11 or 12, wherein the aircraft (1) is an unmanned aerial vehicle.

18. The aircraft as claimed in any one of claims 11-13, wherein alanding gear height, from skid to a lowest point of a fuselage (11) is greaterthan 50 °/> of a distance between the skids, preferably greater than 75 °/> ofthe distance between the skids (151).