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Title:
AIRCRAFT LANDING METHOD, SYSTEM AND DEVICE
Document Type and Number:
WIPO Patent Application WO/2007/086055
Kind Code:
A1
Abstract:
The invention provides a system, method and landing device for landing an aircraft (50) with respect to a predetermined landing location (P). The aircraft is configured for powered flight at least when the parafoil (60) is deployed, and includes an automatic landing system for controllably executing a landing approach maneuver for the aircraft while in free powered flight with the parafoil deployed to enable the aircraft to be brought into overlying proximity with the landing location. A landing device in the form of an energy absorbing landing net arrangement (20) is provided at the landing location for enabling the aircraft to be landed thereon at least partially vertically when in overlying proximity, and for dampening the landing impact of the aircraft.

Inventors:
SOMECH HAIM (IL)
Application Number:
PCT/IL2007/000090
Publication Date:
August 02, 2007
Filing Date:
January 25, 2007
Export Citation:
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Assignee:
ISRAEL AEROSPACE IND LTD (IL)
SOMECH HAIM (IL)
International Classes:
B64C39/02; B63B35/52; B64D17/80; B64F1/02
Domestic Patent References:
WO1993017908A11993-09-16
Foreign References:
US3980259A1976-09-14
US5109788A1992-05-05
GB279307A1927-10-27
US1739193A1929-12-10
FR2712252A11995-05-19
US4408737A1983-10-11
US4311290A1982-01-19
US1625020A1927-04-19
Attorney, Agent or Firm:
REINHOLD COHN AND PARTNERS (Tel Aviv, IL)
Download PDF:
Claims:
CLAIMS:

1. A system for landing an aircraft with respect to a predetermined landing location, comprising:- an aircraft, comprising: a powerplant for providing motive power to the aircraft; a parafoil, the aircraft being configured for powered flight at least when the parafoil is deployed; and an automatic landing system for controllably executing a landing approach maneuver for the aircraft while in free powered flight with the parafoil deployed to enable the aircraft to be brought into overlying proximity with said landing location; and an energy absorbing landing net arrangement at said landing location adapted for enabling said aircraft to be landed thereon at least partially vertically when in said overlying proximity, and for dampening the landing impact of the aircraft. 2. A system according to claim 1 , wherein said net arrangement comprises

- a net covering an area sufficient for enabling at least a major portion of the aircraft to land thereon, the net being generally inclined to the horizontal at an angle substantially less than 90 degrees;

- a net support structure adapted for supporting the net at said landing location vertically displaced therefrom;

- the net arrangement being configured to prevent substantial displacement of its spatial position with respect to the landing position during operation of the system.

3. A system according to claim 2, wherein said support structure is reversibly deployable with respect to the landing location.

4. A system according to any one of claims 2 or 3, wherein said support structure includes a plurality of struts configured for enabling selective adjusting of the longitudinal lengths thereof.

5. A system according to claim 4, wherein said struts are each anchored at one end thereof with respect to said landing location, and are attached at an opposed end thereof to a periphery of said net.

6. A system according to any one of claims 4 or 5, wherein said struts are telescopically or collapsibly adjustable to any desired longitudinal length between an upper and a lower limit.

7. A system according to any one of claims 4 to 6, wherein said struts are controllably adjustable to generally incline said net with respect to a horizontal plane with respect to one of a number of different directions along said horizontal plane. 8. A system according to claim 7, comprising a plurality of struts in peripheral arrangement with respect to said net, wherein said net is joined to each said struts at a height that is controllably and individually adjustable with respect to said landing location.

9. A system according to any one of claims 2 to 8, wherein said net is configured for deforming elastically or plastically such as to absorb at least part of said landing impact and for dampening the same.

10. A system according to any one of claims 2 to 9, further comprising a dampening mechanism operatively connected to at least one of said net and said struts.

11. A system according to any one of claims 1 to 10, wherein said landing location is on a floating vessel.

12. A system according to claim 11, wherein said floating vessel is a barge or raft.

13. A system according to claim 11, wherein said floating vessel is self-propelled.

14. A system according to any one of claims 1 to 13, wherein said landing location is a deck of said floating vessel. 15. A system according to any one of claims 2 to 14, further comprising auxiliary means for energy absorption disposed at said landing location under the landing net.

16. A system according to any one of claims 2 to 15, wherein said aircraft has fixed wings and said landing net has a first dimension about twice the wingspan of said aircraft.

0

- 21 -

17. A system according to any one of claims 2 to 15, wherein said aircraft has fixed wings with collapsible wing tips sections, and said landing net has a first dimension of magnitude similar to that of the operational wingspan of said aircraft.

18. A system according to any one of claims 1 to 17, wherein said aircraft 5 comprises fixed wings for providing lift during a regular mission, and wherein said parafoil is selectively deployable at the beginning of said landing approach maneuver.

19. A system according to any one of claims 1 to 18, wherein said automatic landing system is adapted for adjusting the landing maneuver to take account of the relative positions of the aircraft and landing location in real time.

10 20. A landing device for enabling an aircraft, capable of controlled descent, to be landed at a landing location, comprising

- a net covering an area sufficient for enabling at least a major portion of the aircraft to land thereon, the net being generally inclined to the horizontal at an angle substantially less than 90 degrees;

15 - a net support structure adapted for supporting the net at said landing location vertically displaced therefrom;

- the landing device being configured to prevent substantial displacement of its spatial position with respect to the landing position during operation of the device, and wherein the device is configured for dampening a landing impact of

20 the aircraft when landing thereon.

21. A landing device according to claim 20, wherein said support structure is reversibly deployable with respect to the landing location.

22. A landing device according to claim 20 or 21, wherein said support structure includes a plurality of struts configured for enabling selective adjusting of the

25 longitudinal lengths thereof.

23. A landing device according to claim 22, wherein said struts are each anchored at one end thereof with respect to said landing location, and are attached at an opposed end thereof to a periphery of said net.

24. A landing device according to claim 22 or claim 23, wherein said struts are telescopically adjustable to any desired longitudinal length between an upper and a lower limit.

25. A landing device according to any one of claims 22 to 24, wherein said struts are controllably adjustable to generally incline said net with respect to a horizontal plane with respect to one of a number of different directions along said horizontal plane.

26. A landing device according to any one of claims 22 to 25, comprising a plurality of struts in peripheral arrangement with respect to said net, wherein said net is joined to each said struts at a height that is controllably and individually adjustable with respect to said landing location.

27. A landing device according to any one of claims 22 to 26, wherein said net is configured for deforming elastically or plastically such as to absorb at least part of said landing impact and for dampening the same.

28. A landing device according to any one of claims 22 to 27, further comprising a dampening mechanism operatively connected to at least one of said net and said struts.

29. A landing device according to any one of claims 22 to 28, configured for operation on a sea-faring vessel.

30. A landing device according to any one of claims 20 to 29, further comprising an automatic landing system for enabling an aircraft that is to be landed thereon to controllably execute a landing approach maneuver while in free powered flight with a parafoil deployed such as to bring the aircraft into overlying proximity with said landing location.

31. A method of landing an aircraft equipped with a deployable parafoil at a landing location comprising a flexible energy-absorbing landing net, the method including:

- deploying the parafoil at least when the aircraft is within a predetermined vicinity of the landing net;

- with said parafoil deployed, controllably executing a landing approach maneuver for the aircraft while in free powered flight to bring the aircraft into overlying proximity with said landing net; and

- when in said overlying proximity, causing the aircraft to land onto the landing net in a trajectory having a downward vertical component.

32. The method of claim 31, wherein said landing net is deployed substantially horizontally, or inclined with respect to a horizontal plane, above said landing location. 33. The method of any one of claims 31 or 32, further comprising the step of steering the aircraft with deployed parafoil towards the landing location.

34. The method of any one of claims 31 to 33, wherein in the step of causing the aircraft to land includes a final phase in which the aircraft is not in powered flight.

35. The method of any one of claims 31 to 34, wherein said landing location is any one of a floating barge, an anchored barge or a self-propelled vessel.

36. The method of any one of claims 31 to 35, wherein said aircraft is unmanned.

37. The method of any one of claims 31 to 36, wherein said landing net is normally in retracted position and said net is deployed prior to said aircraft being landed thereon.

38. The method of any one of claims 31 to 37, further comprising the step of deploying additional energy-absorbing means under said landing net.

Description:

AIRCRAFT LANDING METHOD, SYSTEM AND DEVICE

FIELD OF THE INVENTION

This invention relates to landing methods of aircraft, in particular with respect to small landing locations.

BACKGROUND OF THE INVENTION

There are different known methods for the recovery of aircraft, in particular unmanned air vehicles (UAVs) that are required to be landed with respect to a relatively small area on a static or moving platform.

For example, EP 1602576 discloses a system for slowing an air vehicle, including an independently supported aerodynamic drag device ostensibly designed so that, after contact is made between the flying air vehicle and the aerodynamic drag device, one or more parts of the aerodynamic drag device are carried along by the air vehicle thereby decelerating the air vehicle, so that a majority of a kinetic energy dissipation of a combination of the air vehicle and the aerodynamic drag device is due to an aerodynamic drag of the aerodynamic drag device.

US 4,147,317 discloses a deck for landing an arrested RPV having a row of substantially parallel elastic stringers deployed between a pair of open bed trailers. The stringers are attached to longitudinal rails on the trailers and to wind-up winches for tensioning the stringers. A pendant or net is attached across one of the trailers between a pair of stanchions and is connected to energy- absorbers on the other trailer for arresting the landing RPV and dropping it down on the deck. Protruding elements of the RPV slide down inbetween the stringers to protect them from damage as the larger body and wing portions are caught on the stringers.

GB 578,440 discloses means for arresting aircraft at landing, particularly on a ship's deck, comprising a net or a plurality of ropes which is or are resiliently supported and into which the aircraft may be flown or run. A pair of nets spaced to permit entry between them of the forward part of the aircraft is supported by cables which pass

through the deck of a ship to springs or other shock-absorbers, the cables first passing through poles hinged at to the deck. The poles are supported by members and the members may be connected to shock absorbers. Rigid or compressible struts for the poles may also be provided. The nets are thus arranged generally vertically to be engaged by the wings of the aircraft.

US 4,311,290 discloses an apparatus and method for recovering and arresting an aircraft or other vehicle, in which a boom is swivelly connected to a support structure via braking mechanism. The boom is pivotally connected to the brake mechanism such that it can also pivot in a second, different plane intersecting the plane of rotation of the brake mechanism. A shear pin prevents pivoting of the boom in the second plane until the boom has experienced a predetermined load in that plane. The distal end of the boom distant from the brake mechanism is provided with structure for engaging the aircraft. When the aircraft is flown at and captured by the boom, the weight and motion of the aircraft breaks the shear pin, causing the boom to move in the second plane until engaged by a stop. This rapid change in position of the engaging end of the boom in the second plane prevents the aircraft from pendulating about the boom. Forward motion of the aircraft also causes movement within the brake mechanism in the first plane which absorbs the kinetic energy of the aircraft as the boom swivels against the brake mechanism, so that the aircraft is slowed and arrested. US 6,338,457 discloses a parachute recovery system which comprises a payload, a parachute or parasail and a guidance control electronics and servo system. The parachute, which is rectangular in shape, is connected by a plurality of control lines to the guidance control electronics and servo system, which is attached to the payload. The payload may be an air launch component such as a spacecraft, a target drone, unmanned air vehicle, camera film, or similar apparatus. The guidance control electronics and servo system is used to control glide path trajectory and provide for a safe non-destructive landing of the payload. Servo system adjust the length of each of the plurality of control lines attached to the parachute to provide a means for controlling the parachute so as to control the speed, direction and lift of the parachute recovery system.

US 3,980,259 discloses a powered remotely piloted vehicle which is not controllable at the low landing speeds necessary for landing on a platform of small area

is provided with a para-foil type wing deployable at the beginning of a recovery sequence, and is further provided with a rocket ejectable line which is passed to the landing platform and winched in so that the composite flight vehicle and deployed para-foil wing is drawn towards the platform after the manner of a kite. US 4,753,400 discloses a shipboard mounted apparatus for the retrieval of air vehicles, including remotely piloted, or autonomous, unmanned vehicles, which includes a deployable lifting device such as a ram-air parachute which is secured through a tow line to the ship traveling upwind therebelow. A capturing device such as a ribbon parachute which may be annular is also movably secured to the tow line immediately below the ram-air parachute and may include a homing beacon therein such that capture of an air vehicle is achieved by it traveling into and collapsing this ribbon parachute. A winch is secured to the ship therebelow and is attached to the lower end of the tow line to control the inward and outward movement of the extended tow line. Once an air vehicle is captured in the ribbon parachute, the tow line is pulled in by the winch allowing the collapsed ribbon parachute and the captured air vehicle to be drawn into the ship to thereby be received by a landing net preferably of an open mesh nylon webbing in a generally slanting configuration.

US 5,109,788 discloses a flexible surface element arranged on a vehicle to form a trampoline-like extendable or stretchable receiving or retrieval surface for drones. For this purpose, the surface element is brought out from a gathered-in, folded or pivoted- inward stored, stowed position into a mounted expanded position by means of extendable retention and guidance elements.

SUMMARY OF THE INVENTION

By "free powered flight" is meant powered flight by an aircraft while untethered or otherwise physically un-connected with respect to the ground or another vehicle.

The present invention relates to a system for landing an aircraft with respect to a predetermined landing location, comprising:- an aircraft, comprising: a powerplant for providing motive power to the aircraft; a parafoil, the aircraft being configured for powered flight at least when the parafoil is deployed; and an automatic landing system for controllably executing a landing approach maneuver for the aircraft while in free powered flight with the parafoil deployed to enable the aircraft to be brought into overlying proximity with said landing location; and an energy absorbing landing net arrangement at said landing location adapted for enabling said aircraft to be landed thereon at least partially vertically when in said overlying proximity, and for dampening the landing impact of the aircraft.

By "overlying proximity" is meant that the aircraft is at a position generally above the landing location, vertically spaced therefrom and within a catch radius around the landing location such that, for a particular set of flight and/or environmental conditions, including, for example, wind speed, turbulence, velocity of the landing location (e.g. when this is on a moving vessel), characteristics of the parafoil, for example when in unpowered flight (optionally controlled via the automatic landing system, for example), weight of the aircraft, aerodynamics of the aircraft, and so on, would ensure that, in some embodiments once the powerplant is switched off, the aircraft follows a trajectory that compels it to automatically land at the landing location, and thus over the net arrangement provided thereat. In some embodiments, landing may occur with the powerplant still operational, though its power output may be controllably reduced. In other embodiments, the landing is unpowered, once the aircraft is in the aforementioned overlying proximity position, so that its momentum, gravity, and trajectory, optionally with parasail control, carry the aircraft to the landing location. In some embodiments, the vertical spacing associated with overlying proximity may be, by way of example, less than about 10m, preferably less than about 5m, for example about 3m. In some embodiments, the catch radius associated with overlying proximity may be, by way of example, within a few aircraft wing spans, and in some cases such as to circumscribe the plan area of the net arrangement.

The net arrangement may comprise: a net covering an area sufficient for enabling at least a major portion of the aircraft to land thereon, the net being generally inclined to the horizontal at an angle substantially less than 90 degrees; a net support structure adapted for supporting the net at said landing location vertically displaced therefrom; the net arrangement being configured to prevent substantial displacement of its spatial position with respect to the landing position during operation of the system.

The present invention also relates to a landing device for enabling an aircraft, capable of controlled descent, to be landed at a landing location, comprising a net covering an area sufficient for enabling at least a major portion of the aircraft to land thereon, the net being generally inclined to the horizontal at an angle substantially less than 90 degrees; a net support structure adapted for supporting the net at said landing location vertically displaced therefrom; the landing device being configured to prevent substantial displacement of its spatial position with respect to the landing position during operation of the device, and wherein the device is configured for dampening a landing impact of the aircraft when landing thereon. The system and/or the landing device according to the invention may have some or all following features.

Optionally, the support structure may be reversibly deployable with respect to the landing location. In some embodiments the support structure includes a plurality of struts configured for enabling selective adjusting of the longitudinal lengths thereof. The struts may be each anchored at one end thereof with respect to said landing location, and are attached at an opposed end thereof to a periphery of said net. Optionally, the struts may be telescopically or collapsibly adjustable to any desired longitudinal length between an upper and a lower limit.

Optionally, the struts may be controllably adjustable to generally incline said net with respect to a horizontal plane with respect to one of a number of different directions along said horizontal plane. In some embodiments, a plurality of struts are provided in peripheral arrangement with respect to said net, wherein said net is joined to each said struts at a height that is controllably and individually adjustable with respect to said landing location. Thus, this feature allows the inclination direction of the net to be matched to the trajectory of the aircraft, the wind direction, direction of motion of the landing location, and other factors, and to do this matching in real time as conditions change. The net may be configured for deforming elastically or plastically such as to absorb at least part of said landing impact and for dampening the same. Optionally, a dampening mechanism may be provided, operatively connected to at least one of said net and said struts.

By way of example, the landing location may be on a floating vessel, such as a deck of a floating vessel, which may be, for example a barge or raft, or wherein the floating vessel is self-propelled.

Auxiliary means may optionally be provided for energy absorption disposed at said landing location under the landing net.

The net may be sized according to the aircraft that is to be landed on it. For example, when the aircraft has fixed wings, the landing net may have a first dimension

(e.g. width or diameter) about twice the wingspan of said aircraft. Optionally, if the aircraft has fixed wings with collapsible wing tips sections, the landing net may have a first dimension of magnitude similar to that of the operational wingspan of said aircraft.

In some embodiments, the aircraft comprises fixed wings for providing lift during a regular mission, and the parafoil is selectively deployable at the beginning of said landing approach maneuver. In other embodiments, the parafoil generates the lift required for the regular mission as well. The automatic landing system may be adapted for adjusting the landing maneuver to take account of the relative positions of the aircraft and landing location in real time.

The landing device according to the invention may be configured for operation on a sea-faring vessel or on any suitably configured vehicle. In some embodiments, the landing device is optionally retroactively installable in any desired landing location, which may be static or on a movable platform such as a vessel, etc. In these or other embodiments, the landing device may further comprise an automatic landing system for enabling an aircraft that is to be landed thereon to controllably execute a landing approach maneuver, while in free powered flight with a parafoil deployed, such as to bring the aircraft into overlying proximity with said landing location. Part of the landing system may be installable in the aircraft. The present invention also relates to a method of landing an aircraft equipped with a deployable parafoil at a landing location comprising a flexible energy-absorbing landing net, the method including: deploying the parafoil at least when the aircraft is within a predetermined vicinity of the landing net; with said parafoil deployed, controllably executing a landing approach maneuver for the aircraft while in free powered flight to bring the aircraft into overlying proximity with said landing net; and when in said overlying proximity, causing the aircraft to land onto the landing net in a trajectory having a downward vertical component. Optionally, the landing net may be deployed substantially horizontally, or inclined with respect to a horizontal plane, above said landing location.

The method may further comprise the step of steering the aircraft with deployed parafoil towards the landing location. The step of causing the aircraft to land may comprise freely landing the aircraft, and may include a final phase in which the aircraft is not in powered flight.

Optionally, the landing location is any one of a floating barge, an anchored barge or a self-propelled vessel, and optionally, the aircraft is unmanned.

Optionally, the landing net is normally in retracted position and said net is deployed prior to said aircraft being landed thereon. Further optionally, the method may include the step of deploying additional energy-absorbing means under said landing net.

According to other aspects of the invention, there is provided a method of landing a fixed-wing aircraft equipped with foldable parafoil, in a landing location, the method including:

- deploying a flexible energy-absorbing landing net substantially horizontally above said landing location;

- navigating the aircraft with folded parafoil towards the landing location;

- opening (deploying) the parafoil in predetermined vicinity of the landing net;

- landing the aircraft, in controlled parafoil flight, onto the landing net.

According to an embodiment of the invention, the aircraft is self-propelled or powered and the controlled parafoil flight includes powered parafoil flight. According to another embodiment of the invention, the controlled parafoil flight includes parachuting or dropping of the aircraft on the landing net. According to certain embodiments of the invention, the location of landing is a floating barge or a self- propelled vessel, an anchored barge, or a deck of a floating vessel. The aircraft may be manned or unmanned. According to an embodiment of the invention, the method optionally further includes deploying additional energy-absorbing means under said landing net.

According to an embodiment of the invention, the landing net is normally in folded position and the deploying is performed before landing. According to another embodiment of the invention, the net is assembled to movable supporting means and the deploying is performed by moving the supporting means into a predetermined position.

According to an embodiment of the invention there is provided a landing device for practicing the method of the invention, the landing device including a flexible energy-absorbing landing net and a support means adapted to hold the landing net at a predetermined height above the landing location. According to an embodiment of the invention, the support means is movable so that the landing net may be removed from said landing location. According to another embodiment, the support means includes a plurality of telescoping or collapsible struts, also referred to herein as pillars, booms or arms. According to another embodiment of the invention, the landing device further comprises means for energy absorption disposed at the landing location under the landing net. According to an embodiment of the invention, there is provided a fixed-

wing aircraft equipped with foldable parafoil and capable of controlled descent with deployed parafoil, wherein the fixed wing of the aircraft has collapsible or detachable consoles adapted to be collapsed or detached before landing.

According to another embodiment of the invention, there is provided a landing device for landing an aircraft capable of controlled descent in a landing location, the landing device including:

- a flexible energy-absorbing landing net;

- a support means adapted to hold said landing net substantially horizontally at predetermined height above said landing location. According to yet another embodiment of the invention, there is provided a method of landing a fixed-wing aircraft capable of controlled descent, in a landing location, the method including:

- deploying a flexible energy-absorbing landing net substantially horizontally above said landing location; - navigating the aircraft towards the landing location;

- forcing the aircraft in a regime of controlled descent in predetermined vicinity of the landing net;

- landing the aircraft, in controlled descent, onto the landing net.

According to another embodiment of the invention, a fixed-wing aircraft is provided, equipped with foldable parafoil and capable of controlled descent with deployed parafoil, wherein the fixed wing of said aircraft has collapsible or detachable consoles adapted to be collapsed or detached before landing.

According to another embodiment of the invention, a landing device for landing an aircraft is provided, capable of controlled descent in a landing location, the landing device including:

- a flexible energy-absorbing landing net;

- a support means adapted to hold said landing net substantially horizontally at predetermined height above said landing location.

According to another embodiment of the invention, a method is provided of landing a fixed- wing aircraft capable of controlled descent, in a landing location, the method including:

- deploying a flexible energy-absorbing landing net substantially horizontally above said landing location;

- navigating the aircraft towards the landing location;

- forcing the aircraft in a regime of controlled descent in predetermined vicinity of the landing net;

- landing the aircraft, in controlled descent, onto the landing net.

According to aspects of the invention the height of the net above the landing location may be variably adjusted to minimize turbulence effects during the final phase of landing an aircraft onto the net.

BRIEF DESCRIPTION OF THE DRAWINGS

In order to understand the invention and to see how it may be carried out in practice, embodiments will now be described, by way of non-limiting example only, with reference to the accompanying drawings, in which:

Fig. 1 schematically illustrates in side view an embodiment of the system of the invention.

Fig. 2 schematically illustrates the embodiment of Fig. 1 with the net slanting in the direction of approach of the aircraft; Fig. 2(a) illustrates a detail of an embodiment of a net support strut.

Fig. 3 schematically illustrates in top view a net arrangement according to one embodiment of the invention.

DETAILED DESCRIPTION OF EMBODIMENTS

According to one aspect of the present invention, a system and method are provided for landing an aircraft onto a predetermined landing location. Referring to

Figs. 1 to 3, one embodiment of the system, generally designated with the numeral 100, comprises an aircraft 50 and a landing net arrangement 20 at a desired landing location

P, which in this embodiment is comprised on a ship 90, or indeed any other type of

vessel or vehicle, which may be stationary or moving during operation of the system 100.

The aircraft 50 in this embodiment comprises a fixed wing unmanned air vehicle

(UAV) 5 comprising a main body 52, wings 54 and powerplant 56, such as for example at least one front, puller propeller engine. According to other aspects of the invention, the aircraft may optionally be a manned aircraft, and the powerplant may be any other desired powerplant, for example one or more jet engines, pusher propeller, etc.

Further, the aircraft 50 comprises a deployable parafoil 60, which can be selectively deployed when the aircraft is within a predetermined vicinity of the landing location P, for example within a radius of several kilometers.

According to other aspects of the invention the aircraft 50 is equipped with the parafoil as the regular lift-producing surface for normal flight, or may be an auxiliary lift arrangement and may be deployed at any desired range from the landing location P. The parafoil 60 includes any form of steerable parachute capable of providing controllable forward motion, and may include, for example, ram-air parachutes or parasails, for example, which are commonly known in the art. One type of parafoil is disclosed in US 3,285,546, the contents of which are incorporated herein in their entirety.

The parafoil 60 comprises a fabric body 62 or the like, which may provide lift during forward motion, and the shape of the body 62 is maintained by the airflow over the body 62; the parafoil also comprises controllable flaps (not shown) for enabling substantially vertical landing maneuvers, for example. A plurality of control lines 64 are connected to strategic points along the periphery of the fabric body 62, for example at the two lateral ends 61 where the lines 64 are longitudinally spaced one from another at a first end thereof, enabling the parafoil 60 to be controlled by pulling or giving slack to the individual lines 64. The second end of the lines 64 are fed to a control unit 68, which includes a suitable guidance control electronics and a suitable servo system 70 for controlling the lengths of the lines, and thus the speed, direction and lift of the parafoil 60. The system 100 further comprises an automatic landing system 80 configured at least for controllably executing a landing approach maneuver for the aircraft while in free powered flight with the parafoil 60 deployed to enable the aircraft 50 to be brought

into overlying proximity with said landing location P. The landing system 80 may comprise a flight computer 82 comprised in the aircraft 50, a ground station computer 84 associated with the landing location P, and suitable communications link (not shown) between the flight computer 82 and the ground computer 84. The flight computer 82 is configured for controlling servo system 70 via said guidance control electronics, for example, such as to steer the aircraft 50 and navigate the same towards the landing point P. The computer 82 may be configured to determine and track the position and velocity of the aircraft 50, and may be equipped with a GPS or other global positioning system, for example DGPS, GLONASS and so on (and may optionally be assisted by additional automatic radar landing system for main or backup landing, as will be described in greater detail below), which allows the position of the aircraft to be accurately determined in real time. Further, suitable attitude and speed sensors may be provided in the aircraft for determining the direction and speed thereof. Alternatively, the direction and speed of the aircraft may be obtained by analysis of the positioning data as a function of time. The flight computer 82 may comprise a suitable transmitter (not shown) for transmitting the position data, and optionally other data such as for example aircraft velocity, height, attitude (roll, pitch and or yaw) or other data, to the ground computer 84. The flight computer 82 may also comprise a suitable receiver (not shown) for receiving data or commands from the ground computer 84, and the flight computer 82 is thus also configured to process the same.

The flight computer 82 may also be configured for controlling the regular operations of the aircraft, for example regarding surveillance, etc., or alternatively the aircraft 50 may have a separate computer for these functions.

The ground computer 84 may be configured to determine and track the position and velocity of the ship 90, for example in a similar manner to the way in which the position of the aircraft 50 is tracked via the flight computer 82, mutatis mutandis. Thus, the ground computer 84 may also be configured for determining the position of the landing location, and thus may also comprise a GPS or other global positioning system, which allows the position of the landing location P, i.e., the to be accurately determined in real time. Similarly, suitable speed and direction (heading) sensors may be provided in the ship 90 for determining the direction and speed thereof. Alternatively, the direction and speed of the ship 90 may be obtained by analysis of the positioning data as

a function of time. The ground computer 84 may comprise a suitable receiver (not shown) for receiving data etc from the flight computer 82, and the ground computer 84 is thus also configured to process the same. The ground computer 84 may also comprise a suitable transmitter (not shown) for transmitting the position data, and optionally other data such as for example ship velocity, height, attitude (roll, pitch and or yaw) or other data, to the flight computer 82.

Thus, in this embodiment, the landing system 80 computes the position and direction of the ship 90, and provides a prediction of where the ship will be within a certain time period. Then, given the position speed and direction of the aircraft 50, determines a trajectory for the aircraft to follow so as to come into proximity with the ship 90 at a particular point in time. These calculations may be updated continuously or periodically, so as to correspondingly update the flight path of the aircraft 50 if necessary. Once the aircraft 50 has come within a predefined vicinity of the ship 90, in particular the net arrangement 20, final landing maneuvers may be implemented. The landing system 80 is further configured for commanding the aircraft 50 via the flight computer 82 such as to execute additional maneuvers, including for example the final landing maneuvers. For example, once the aircraft has been brought into close proximity to the landing location P, in particular in overlying relationship with the net arrangement 20, the flight computer 82 provides a suitable command signal to the powerplant to cease providing motive power, and thus enables the aircraft to drop onto the net arrangement 20. Additionally, the landing system 80 may optionally also control the flight path of the aircraft 50 such as to execute evasive maneuvers if the approach path is not safe, for example.

Additionally or alternatively, the landing system 80 may comprise an automatic radar landing system, in the form of a radar-based target acquisition system, comprising one or a plurality of suitable radars and associated computers. The radars may be located in the aircraft 50, and configured for detecting, identifying and tracking the ship 90, and the computer may then compute the appropriate flight path to bring the aircraft 50 into close proximity with the ship, and command the aircraft to do so. The computed flight path may be updated continuously or periodically, as the relative spatial positions of the ship and aircraft are changed. Additionally or alternatively, the radars may be provided on the ship 90, which is configured for detecting, identifying and tracking the

aircraft 50, and the computer may then compute the appropriate flight path to bring the aircraft 50 into close proximity with the ship, and a suitable transmitter may then transmit appropriate commands to the aircraft flight control computer to enable the aircraft to do so. In this embodiment, the ship 90 may comprise, for example a naval ship, merchant ship, scientific or survey ship, and so on, equipped with a suitable open area, such as for example a helicopter landing deck 92, container top, or the like, which may be considered the landing location P for the aircraft.

The landing net arrangement 20 is provided at the landing location P and is configured for enabling the aircraft 50 to land thereon, substantially vertically with respect to the net 20 (which may be moving horizontally together with the ship 90) or in a landing trajectory having a significant vertical motion component with respect to the net arrangement 20.

In this embodiment, the net arrangement 20 comprises a net 22, of generally rectangular plan form, having corners 22a, 22b, 22c, 22d, mounted at said corners with respect to a pair of laterally spaced forward pillars, booms or struts 12a, 12b and a pair of laterally spaced rear pillars, booms or struts 12c, 12d, respectively, in rectangular arrangement when viewed from above. Referring particularly to Fig. 2(a), each strut, collectively referred to by the numeral 12, is anchored, in this embodiment pivotably mounted, at one longitudinal end 11 thereof, to said deck 92. A second longitudinal end

13 of each strut is connected to a part of the periphery of the net 22, such that at least a part of the net 22 is supported in vertically overlying relationship with the deck 92, providing a vertical spacing H between the deck 92 and the net 22.

Additional struts (not shown) may be provided along the periphery of the net for further support.

Alternatively, the net 22 may have any desired shape, for example circular, elliptical, polygonal, etc., and supported by means of a plurality of struts 12 around the periphery thereof.

The net 22 may be held taut between the struts 12, or alternatively may be provided with limited slack so that it is not in pre-tension before the aircraft is landed thereon.

Optionally, the front edge 22A of the net 22, supported by struts 12a, 12b, may be held at a higher position than a rear edge 22B of the net 22 supported by rear struts 12c, 12d.

Alternatively, one lateral edge 22C of the net 22 may be higher than the other lateral edge 22D of the net 22, wherein the corresponding lateral pair of struts 12a and

12d, support the corresponding net corners 22a and 22d at a relatively higher position, while the other lateral pair of struts 12b and 12c, support the corresponding net corners

22b and 22c at a relatively lower position. In this manner, a laterally sloping net 22 may be presented to an aircraft approaching the ship 90 from one lateral direction. Conversely, the net may be configured to slope in the opposite lateral direction by having lateral edge 22D higher than lateral edge 22C.

Alternatively, the heights of corners 22a, 22b, 22c, 22d may be set to be equal one with another, such as to present a generally horizontal landing surface for the aircraft 50, for example as illustrated in Fig. 1. Alternatively, each corner 22a, 22b, 22c, 22d may be set at a specific height which may be different one from another, such as to present a generally sloping landing surface for the aircraft 50 as the aircraft approaches from any particular lateral direction along the horizontal plane.

Optionally, the corners 22a, 22b, 22c, 22d are fixedly joined to the corresponding ends 13 of strut 12a, 12b, 12c, 12d, respectively, and these struts are configured for selectively, reversibly and optionally differentially extending longitudinally, such as to raise or lower the corresponding net corner. For example the struts 12 may be telescopically extendible and retractable, the longitudinal dimension of each strut 12 being controllable by means of a suitable control unit (not shown). The struts 12 may be configured to controllably extend and retract hydraulically, pneumatically, electrically or mechanically, for example.

Alternatively, the corners 22a, 22b, 22c, 22d are fixedly joined to a collar or the like that is configured for longitudinal displacement with respect to the corresponding end 13 of strut 12a, 12b, 12c, 12d, respectively. Thus, these struts may be of a particular and fixed longitudinal length when the system 100 is in operation (but may optionally be telescopically or otherwise reversibly retractable for stowage when the system is not

in use), and the collars are configured for selective, reversible and optionally differential displacement longitudinally, such as to raise or lower the corresponding net corner. Displacement of the collars may be done in any suitable manner, for example by being mechanically coupled to pneumatic, hydraulic, mechanical, electrical or other actuators that may be aligned with the corresponding strut 12.

The landing net 22 may comprise any suitable net structure that is sufficiently strong and elastic to enable it to absorb part or all of the mechanical energy of the descending aircraft. Such nets may be commercially available, or may be custom-made to suit the particular requirements of a particular system 100 of the invention. According to one aspect of the invention, the net arrangement is configured for dampening the landing impact of the aircraft 50 thereon. In one embodiment, the material of the net 22, and optionally the manner in which the net is weaved or otherwise constructed from this material, provides the net 22 with an elasticity and modulus that is sufficient to enable the net 22 to deform elastically or plastically such as to absorb the landing impact of the aircraft 50 thereon without causing damage to the aircraft 50 or ship 90, or minimizing such damage. For example, the net 22 may deform elastically or plastically at a rate such as to decelerate the landing velocity of the aircraft over a time period and stopping distance (typically less than the height H), that does not induce high deceleration forces. At the same time, the rebound from the net 22 may be dampened in a natural manner if the elastic/plastic elongation characteristics of the net 22 are matched to the landing impact and acceleration loads of the aircraft, which may be a function of the aircraft weight and landing impact velocity, for example.

Additionally or alternatively, the energy absorbing and dampening features of the net arrangement 20 may be provided by means of mechanical, hydraulic or pneumatic damping devices, which are coupled to the periphery of the net 22, such that the impact loads on the net 22 are at least partially transmitted to the dampers when the aircraft is landed on the net 22.

For example, and referring to Fig. 3, a pair of brake drums 35 may be provided, one on each lateral side of the net 22. Each pair of laterally adjacent corners 22a, 22d and 22b, 22c of the net 22 are connected to one or another of brake drum 35 via a brake cable 36 that is fixed to the corresponding laterally adjacent net corners. The net corners 22a, 22d and 22b, 22c are mounted to the ends 13 of the corresponding struts 12 for

relative movement therewith by means of pulleys 37 that are provided the ends 13.

Thus, and referring to the position of the net and aircraft indicated by the dotted lines in

Fig. 2, when the net 22 is depressed downwards, in reaction to an aircraft 50 landing thereon, for example, the corners 22a, 22d and 22b, 22c are downwardly displaced from the corresponding strut ends 13, pulling on the corresponding brake cables 36, which in turn pull the braking and damping mechanism in the brake drums 35, thereby absorbing and dampening .the landing impact on the net 22.

Optionally, the dampers may be incorporated in the structure of the struts 12, particularly in embodiments where the struts are extendible, or in embodiments where the struts 12 are elastically or plastically bendable to absorb and dampen the landing impact forces.

Optionally, additional means for energy absorption may be disposed on the landing deck 92, such as for example inflatable pads or elastic mats. Additional arrangements may optionally be provided for preventing net recoil after landing, for example suitably designed pads.

The plan area of the landing net 22 may be sized to be about twice the wingspan, square, of the aircraft 50, for example. If the aircraft wings have collapsible or detachable wing tips the landing net may be correspondingly even smaller.

Optionally, the struts 12 may be movable or retractable, for example they be configured as collapsible or telescoping, so that the net 22 may be removed from the deck when not needed.

One mode of operation of the system 100 is as follows. During aircraft's take-off and mission flight, the parafoil 60 normally folded and hidden in the aircraft body 52.

Before- landing, at some predetermined distance and height from the landing location P, the parafoil 60 is deployed and the aircraft 50 performs a controlled descent towards the landing net 22, the velocity of the aircraft having been significantly reduced by the deployment of the parafoil 60.

During the descent, the aircraft may be steered and trimmed by means of the parafoil 60, via lines 64. Optionally, the flight of the aircraft 50 may also be controlled by means of the wing control surfaces of wings 54 and tail, for example the ailerons, and the rudder, and the powerplant 56 continues to power the flight of the aircraft 50.

Accordingly, if necessary, a landing pass may be aborted, and the aircraft flown around

000090

- 18 - the ship 90 to try again later. The aircraft 50 is in free flight, at a relatively low airspeed, for example up to about 40 knots, supported via the parafoil 60, and untethered or otherwise physically connected to the ship 90. When the aircraft 50 is at a position close to and above the net 22, for example a height of about 3m, and moving at a predetermined low forward velocity relative to that of the ship 90, which may be close to zero or up to about 20 knots relative velocity, for example, the powerplant is stopped, the parafoil flaps are operated and the aircraft parachutes or drops onto the net 22. The net arrangement absorbs at least a portion of the landing impact forces, minimizing or eliminating damage risk to the aircraft 50 or ship 90. It will be appreciated that the system, and in particular the horizontal or inclined landing net arrangement and the inventive method of landing according to the invention, may be used not only on a motor ship with a landing deck, but in any restricted landing location such as a barge or raft (anchored or not), roof of a building, courtyard, automotive vehicle, etc. The landing device may further include a vertical net, known per se, to be used in an emergency case of non-deployment of the parafoil.

Furthermore, the horizontal landing net may be used with aircraft capable of steep descent in deep stall, without deploying a parafoil, similar to that described above, mutatis mutandis.

The landing method and device of the present invention allow long-endurance missions of UAVs starting and finishing in a spot-sized landing location. For example, an UAV of 15m wingspan and about 600kg to about 1000 kg take-off weight may be launched by means of booster rockets or catapult, operate in a 1000 nautical miles range and return to a landing net of about 25mx25m in size.

In the method claims that follow, alphanumeric characters and Roman numerals used to designate claim steps are provided for convenience only and do not imply any particular order of performing the steps.

Finally, it should be noted that the word "comprising" as used throughout the appended claims is to be interpreted to mean "including but not limited to".

While there has been shown and disclosed example embodiments in accordance with the invention, it will be appreciated that many changes may be made therein without departing from the spirit of the invention.