GB2440520A

GB2440520A - Motion Compensated Aircraft Platform

Info

Publication number: GB2440520A
Application number: GB0615474A
Authority: GB
Inventors: Liam Clear
Original assignee: Individual
Current assignee: Individual
Priority date: 2006-08-03
Filing date: 2006-08-03
Publication date: 2008-02-06
Also published as: GB0615474D0

Abstract

A platform 2 on a carrier vehicle 4 is used for launching, landing and accommodating aircraft 12. The platform is controllably moveable such that it may be substantially isolated from selected translational motion of the carrier vehicle. The carrier vehicle 4 may be an air or sea craft or land vehicle and typically is a ship. The position and orientation of the platform 2 is controllably movable to stabilise its level such that the aircraft 12 is able to land or launch on/from e.g. a substantially horizontal surface significantly decoupled from the motion of the carrier vehicle 4. The motion of the platform may be controlled in response to at least one information source, such as satellites regarding the position and orientation of the carrier vehicle and/or the aircraft.

Description

BP.09-0647

MOTION COMPENSATED AIRCRAFT PLATFORM

Field of the Invention

This invention concerns motion compensating platforms attached to a means of transport, for launching, landing and accommodating aircraft. One possible use of the invention would be in a helicopter landing platform attached to a ship at sea that compensates for the vertical ship motion resulting from adverse sea conditions to aid safe landing of helicopters.

Background

Aircraft landing platforms such as helipads upon ships can often be confined to a small area especially when the top deck of the ship is not designed specifically for launching and accommodating multiple aircraft.

When the ship is moving in an unpredictable fashion for example in adverse weather and sea conditions, or simply when the aircraft is not quite on the correct approach for landing, a restricted sized landing area moving with the ship presents difficulties in the safe landing of the aircraft. The pilot may miss the platform or land only partly on it, with disastrous consequçnces. Larger platforms give the pilot a larger target to aim for. However, vertical motion of the platform may still cause unexpectedly hard landings, resulting in structural damage to the aircraft and platform, or unexpectedly soft landings in which the aircraft becomes unwantedly airborne again; in all cases with possible discomfort, injury and alarm for passengers and crew. Unexpected sideways movement of the platform can cause similar discomfort and in extreme cases damage to or overturning of the aircraft. Analogous problems arise on takeoff, so that the platform may be unsafe to use both for takeoff and landing in bad weather.

In such situations, additional systems may need to be employed to aid the landing and launching of aircraft from the platform. Several pitch and roll stabilised aircraft landing platforms have been described including GB patents 360259 and 204696 that BP.09-0647 keep the platform closer to horizontal as the ship is moving. Japanese patent 4306198 employs clamps on a helicopter landing pad which are released from the helicopter undercarriage allowing takeoff only when the reaction forces applied to the platform by the undercarriage are zero. GB patent 952645 employs a levelling mechanism for a lift platform operated by a number of hydraulic rams and US patent 3878805 uses a horizontal plane indicating member to provide visual indication to a pilot attempting to land on a ship as to which way is level. US patent 4236686 describes an articulated boom which is stabilised in space for capture and release of a manned or remotely piloted vertical take off and landing aircraft.

Although prior proposals have contributed towards safe take off and landing of aircraft, none of them address the problem of landing or flying an aircraft from a platform which is subjected to unpredictable translational movements of a carrier vehicle, such as result for example from heave, pitch and roll of a ship.

Summary

In accordance with the present invention, there is provided a platform from or on which aircraft are flown, landed or accommodated, the platform being attachable to a carrier vehicle and controllably moveable such that it may be substantially isolated from selected translational motion components of the carrier vehicle. The controllable movement may likewise isolate the platform from selected angular movement of the carrier vehicle. This can allow pitch, roll and positional stabilisation of the platform in space, significantly decoupling the platform from the unpredictable motion of the carrier vehicle, so that aircraft are able to take off or land with minimal impact from influences such as adverse sea or weather conditions. The carrier vehicle may be an air or sea craft or a land vehicle and typically the present invention would be embodied upon a ship. The position of the platform is desirably controllable to stabilise its position and orientation in space. For example the position and orientation of the platform may be controllably movable relative to the carrier vehicle to stabilise its level such that the aircraft is able to land on a substantially horizontal surface at a substantially fixed height relative to the earth and that is significantly

I

* BP-09-0647 decoupled from unpredictable motion of the carrier vehicle. For example, where the carrier vehicle is a ship which is unpredictably heaving, pitching and rolling but is not under way (e.g. is at anchor) at sea, the platform upper surface can be maintained at a controlled orientation (e.g. level) and stationary in space. To compensate for cross winds or for the aircraft approach velocity or orientation, the platform upper surface may alternatively be maintained at a controlled slope to the horizontal. Where the ship is in similar conditions but is under way and following a steady average course, the platform can be controllably movable relative to the ship to follow the steady course, its upper surface again being maintained at a controlled orientation and at a substantially fixed height relative to the earth (or relative to mean sea level), isolated from the unpredictable ship movement.

The platform in accordance to the present invention compensates for motion of the carrier vehicle andlor of the landing aircraft, such as motion imposed by adverse weather and/or sea conditions. Advantageously, the platform may take any position and orientation within the limits of its constructional range of motion about the carrier vehicle to aid aircraft launching or landing irrespective of relative motions of the aircraft and carrier vehicle.

The platform may have its movement controlled in response to at least one information source regarding the motion of the carrier vehicle and/or the aircraft. The platform may have an information source provided from satellite technology. The platform may also have an information source provided from instruments and/or people upon any of the carrier vehicle, the aircraft and/or the platform. The instruments may comprise for example one or more accelerometers, inclinometers, angular measurement devices, compasses, altimeters, and/or rangefinders/relative speed detectors of known kind, in any suitable combination. In one embodiment the platform is hydraulically manoeuvred about a boat with an extendable support member attached to the platform and ship by one or more pivoting joints that allow the platform's position and orientation to be controlled in response to information coming from a global positioning system (GPS) and/or other information sources/instruments.

* BP-09-0647 Additionally or alternatively, the platform may incorporate one or more sensors to detect landed or approaching aircraft such that the platform then moves to cushion the landing.

The platform may be attached to the carrier vehicle via at least one support member and at least one pivoting joint or other element having means to provide a controllably movable platform. This member may be an articulated support member optionally comprising sub-members attached to each other via one or more flexible joints. The platform may have fixed or variable length support members or support sub-members.

Variable length support members or support sub-members may have controllably adjusted lengths. Support members or support sub-members may be attachable to the carrier vehicle and/or the platform so as to allow the ends of the support member to undergo translational movement relative to the vehicle and/or platform.

Further features and advantages of the invention are described below with reference to illustrative embodiments shown in the drawings.

Brief description of the drawings

Figure 1 schematically illustrates an embodiment of the present invention where the platform is attached to a ship at sea via a variable length support member and a lower pivoting joint. The side view of the ship is shown where a helicopter is accommodated on the platform.

Figure 2 corresponds to figure 1, except that the ship has moved vertically downwards with respect to its original position and the platform has compensated by keeping its original position.

Figure 3 corresponds to figure 1, except that the ship has moved vertically upwards with respect to its original position.

* BP-09-0647 Figure 4 schematically illustrates an embodiment of the present invention where the platform is attached to a ship at sea via a variable length support member and two pivoting joints. The back view of the ship is shown where a helicopter is taking off from the platform.

Figure 5 corresponds to figure 4, except that the ship has both tilted and moved from its original orientation and position and the platform has compensated by keeping its original position and orientation aided partiy by the variable length support member extending from its original length.

Figure 6 schematically illustrates an embodiment of the present invention where the platform is attached to a ship at sea via an articulated support member comprising three fixed length support sub-members and two pivoting joints, the articulated support member in turn being attached to the platform and ship via respective pivoting joints. The back view of the ship is shown where a helicopter is landing on the platform.

Figure 7 schematically illustrates an embodiment of the present invention where the platform accommodating a helicopter is connected via a pivot joint to a variable length support member which in turn is attached to a sliding rail mounted on a ship so that the support member and platform are both movable (translatable) transversely of the ship.

Figure 8 corresponds to figure 7 where the combined actions of the sliding rail, pivot joint and variable length support member compensate for transverse positional shift and rolling motion from the ship.

Figure 9 schematically illustrates an embodiment of the present invention where the platform changes orientation to counteract the induced motion upon a helicopter from high wind forces.

p BP.09.0647 Figure 10 illustrates the same embodiment as figure 1 whereby sensors are located on the platform to detect a landing helicopter.

Figure 11 corresponds to figure 10 but shows the helicopter landing upon the platform and the platform moving to cushion this landing.

Figure 12 illustrates a further embodiment of the present invention where the platform is controlled by six variable length support members and six pivot joints.

Figure 13 shows a further embodiment of the invention, modified for stowage within a ship's hull.

Description of the Preferred Embodiments

A platform 2 attached to a ship 4 via a single variable length support member 6 is shown in side view in figure 1. The upper end 10 of the support member is rigidly connected to the platform and the lower end of the support member is connected to the ship's deck by a universal joint 8. As shown, the ship is afloat at sea and carrying a helicopter 12 which is accommodated on the platform. When the ship changes position such as by moving vertically downward as shown by arrow 14 in figure 2, the variable length support member 6 adjusts (lengthens) its length to keep the platform substantially at the same height relative to the earth or mean sea level.

Similarly, a shift in the vertically upward direction of the ship's position (arrow 16, figure 3) is also compensated for by shortening the variable length support 6. Such controlled movement is desirable for maintaining an aircraft on the platform and providing a stable landing and takeoff surface for the aircraft whilst the carrier vehicle (ship 4) is subject to adverse sea andlor weather conditions. Without such control of the platform, the aircraft may undesirably land on a surface that is uncontrollably moving in vertical extent, increasing the danger of the landing. The support member 6 is maintained in a substantially vertical orientation by a plurality of linear actuators 7 acting between the ship's deck and the support member 6, spanning the universal joint 8. For example at least three single acting hydraulic or compressed gas operated 4 BP-09-0647 rams 7 are provided equi-angularly spaced around the support member 6, or two preferably orthogonally positioned double acting hydraulic etc. rams (only two shown in figure 1) may be provided. Other arrangements of actuators will be readily apparent, allowing positioning of the support member 6 in any direction relative to the ship's deck. Besides maintaining the support member 6 substantially upright so that the upper surface of the platform 2 is maintained substantially level (horizontal), the actuators 7 can be used to maintain the support at a predetermined angle to the vertical, in a predetermined azimuthal direction, for example to tilt the platform by a predetermined amount so as to compensate for crosswinds or for the orientation and direction of approach of an incoming aircraft. The support 6 may itself comprise a linear actuator such as a single or multi-stage hydraulic or gas operated ram, or a scissor or lazy tongs type structure (not shown). Other suitable variable length supports will be readily apparent.

When an aircraft such as a helicopter is taking off it is desirable to keep the platform which it is taking off from stable in position and orientation. Figures 4 and 5 depict the back view of a ship 4 at sea carrying a helicopter 12 that is about to take off in the direction of arrow! 8 from a platform 2. The support member 6 attaching the platform to the ship in this embodiment is a variable length support member. Figure 5 shows the ship 4 after having changed its orientation such as by rolling (arrow 22) and yawing (arrow 24). In response to this, the variable length support member adjusts its length, and adjusts its orientation relative to the ship 4 about a lower connecting universal joint 8, to compensate for the overall ship motion and keep the platform stable in space when the ship is not under way, or travelling along a steady course when the ship is travelling along a steady average course. The platform 2 is maintained level or with its upper surface at a desired angle to horizontal by pivoting on the upper end of the support member 6 via a further universal joint 11. For controlling the required movement, both joints 8, 11 may be equipped with actuators similar to the actuators 7 of joint 8 in figures 1 -3; omitted for clarity/simplicity in figures 4 and 5.

* BP-09-0641 When an aircraft such as a helicopter is attempting to land (arrow 26, figure 6) on a carrier vehicle such as a ship, it may also be desirable for the aircraft to land upon the platform 2 such that the motion of the ship and/or the approach of the aircraft can be compensated for such that the aircraft can safely and successfully land upon the platform. This may be applicable, for example in figure 6 where a helicopter is landing upon a platform of a ship at sea and adverse weather and/or sea conditions are changing the ship's position and orientation as well as the helicopter's approach to the ship. The platform may also in this embodiment attempt to compensate for any other deviances in approach of the helicopter such that those arising from piloting or navigation errors that may entail the helicopter having to land when the platform is outboard of or below the top deck of the ship 4. Figure 6 depicts an embodiment of the present invention where a platform is attached to a ship at sea via an articulated support member 28 comprising three fixed length support sub-members 20 and two pivoting joints 30, 32. Respective ends of the support member 28 are attached to the platform 2 and ship 4 via pivoting joints 9, 13. All of the joints 9, 13, 30, 32 are equipped with suitable actuators (not shown). Joints 13, 30, 32 may be arranged to pivot about horizontal axes only, whilst joint 9 may be a universal joint arranged on a turntable (not shown) mounted on the ship's deck. Such an articulated support member 28 is of variable overall effective length and may also serve to position the platform 2 to avoid other fixed or moving objects such as other static or launching/landing aircraft.

The pivot 8, 9 attaching the support member 6, 28 to the carrier vehicle 4 as described above is positioned at a fixed location on the carrier vehicle. In a modificaiion, the support member attachment point may be moveable to different locations on the carrier vehicle. For example the support member attachment location may be movable across the upper deck of the carrier vehicle (ship) 4. Such an attachment may be a static/fixed attachment or via a pivoting joint. Figure 7 shows an embodiment where a platform is connected via a pivot joint 11 and actuators such as 7 (not shown in figures 7 and 8) to the top end of a variable length support member 6 which in turn is attached at its bottom end to a sliding rail 34 or similar linear guide mounted transversely of the a ship 4. Suitable actuators (not shown) are provided for moving a BP-09-0647 the support member 6 and platform 2 along the sliding rail 34. Figure 8 shows the same embodiment as figure 7 where the combined actions of the sliding rail, pivot joint and variable length support member compensate for yawing (arrow 24) and rolling (arrow 22) motion of the ship 4. Because the ship's centre of rolling 23 is offset from the upper surface of the platform 2, rolling will cause swaying or lateral movement of the platform 2 as represented by arrows 25. The lateral movement of the support member along the guide rail 34 can be used to compensate for such swaying 25 as well as yawing 24 of the ship 4. The joint 11 is used to maintain the platform 2 level or at a predetermined angle to the horizontal, whereas the variable length support 6 is used to maintain the platform 2 at a substantially fixed elevation relative to the earth or mean sea level. The joint II may be provided at the lower end or part-way along the length of the of the support member, instead of at its upper end as shown in figures 7 and 8. As well as or instead of the guide rail 34 provided at the carrier vehicle's deck, a similar linear guide (not shown) can be provided across the underside of the platform 2, so that the point of attachment of the upper end of the support member 6 is linearly movable crosswise of the platform. The platform linear guide and the deck linear guide, where both present, may be at an angle (e.g. orthogonal) to each other, so that swaying and displacement of the support means in all sideways directions (resulting e.g. from pitching, yawing and rolling of the carrier vehicle 4) can be compensated for. It is envisaged that any method of attaching support members to the carrier vehicle and/or platform where the attaching location is controllably movable about the carrier vehicle and/or platform falls within the scope of the present invention. Moreover, support members, pivot joints, platforms and any other elements providing controllably movable platform position and orientation about the carrier vehicle may take any form of technology that is sufficient to accomplish the aforementioned tasks. Different features of the various embodiments described throughout this specification may readily be combined in ways not specifically described or illustrated.

The platform according to the present invention may be controllably moved about the carrier vehicle in response to at least one information source regarding the motion of the carrier vehicle and/or the aircraft. In an embodiment of such a platform, the * flp.9. 647 information source is provided by satellite technology such as Global Positioning Systems (GPS) which may track the movement of the aircraft andlor carrier vehicle.

In another embodiment of such a platform, the information sources are provided from instruments and/or people upon any of the carrier vehicle, the aircraft and the platform. These may take the form of visual input from crew of the aircraft or of the carrier vehicle. Other instruments acting as information sources according to the present invention may comprise for example gyroscopic and other self levelling apparatus, accelerometers, inclinometers, angular measurement devices, compasses, altimeters, rangefinders and/or relative speed detectors arranged in known manner to control the elevation, orientation and lateral positioning of the platform, and/or its separation and/or relative approach speed with respect to an incoming aircraft. It is envisaged that information sources and combinations thereof are not restricted to those specifically disclosed in the present application and that any sources of relevant position and/or orientation information may be utilised including the use of multiple sources in conjunction. As a non-limiting example, a first GPS receiver can be provided on the platform to determine its position and orientation relative to the earth; a second GPS receiver can be positioned on the carrier vehicle to likewise determine its position and orientation. One or more laser rangefinders or the like can then be used to monitor the relative position of the carrier vehicle and the platform (e.g. where the vehicle is a ship, the distance between the ship's deck and the underside of the platform). The directly measured relative position can then be compared with the difference in the GPS readings to determine error conditions and generate alarms.

The position information thus obtained may also be cross-checked with position and range information from the aircraft (helicopter) avionics.

Another embodiment of the present invention is shown in figure 9 where the platform 2 changes orientation to counteract the induced motion upon a helicopter 12 from high wind forces represented by arrow 36. Information sources may be used to aid this embodiment, such as those for predicting or monitoring weather conditions such as wind speed or direction.

BP-09-0647 In a further embodiment of the invention, sensors 38 may be located on the platform to detect when a helicopter lands. Figure 10 illustrates a helicopter 12 making a landing approach to such a platform 2 rigidly connected at 10 to a variable length support member 6 which is in turn connected to a fixed location on a ship via a pivot joint 8. The sensors 38 in this embodiment may be motion sensors, pressure sensors or any sensor that provides feedback information regarding whether the helicopter has landed. Upon contact by the helicopter, as shown in figure 11, the sensors provide information that causes the variable length support member 6 to reduce in length and cushion the landing of the helicopter.

In another embodiment of the invention, figure 12 shows a platform 2 connected to a deck 5 of a carrier vehicle such as a ship, via six variable length support members 3 connected in closed zigzag fashion between three pivot joints I la-c on the platform underside and three pivot joints 8a-c on the deck. The support members 3 may comprise any suitable linear actuator, such as a single or multi-stage hydraulic or gas-operated ram. In this embodiment the variable length support members may increase or decrease their length dependently or independently and move about the pivot joints to provide the controllable movement of the platform to any position and orientation within their range of extension. Other numbers and configurations of support members are readily possible. Ends of the support members may be connected to the deck 5 and/or platform 2 by individual spaced pivots, rather than the shared or adjacent pivots shown.

A further modification is shown in figure 13. Here a sub-platform 4a has a variable length support member 6 and platform 2 somewhat as shown in figure 4 mounted on its upper surface. The sub-platform 4a can be moved between a raised position (shown in solid lines) flush with a ship's deck 4, to a lowered position shown in phantom lines at 4a'. When lowered, the entire platform assembly is stowed within the hull of the ship. In the raised position, the sub-platform 4a occupies and closes the aperture in the ship's deck 4 from which the platform 2 and support member 6 rise.

When the sub-platform 4a is fully lowered, the deck aperture may be closed by the platform 2. Alternatively a separate hatchway or cover (not shown) may be provided, * BP.09-0647 closable above the platform 2 after this is lowered through the deck aperture into the ship's hull. To reduce the sizes of the sub-platform 4a and corresponding deck aperture needed, the platform 2 (e.g. its edge parts 2a, 2b as shown) may be foldable, and/or the platform may be tilted about the joint 11 to present a smaller profile for passage through the deck aperture. When lowered, one of the platform folding parts 2a, 2b could in this case be used to close the deck aperture, or the platform 2 could be provided with a side apron (not shown) for this purpose. For simplicity, the actuators for controlling movement of the joints 8, ii are again omitted. Any other suitable form of the motion compensated platform may be made stowable within the hull of the ship in a similar way.

Claims

BP.09.0647 Claims: 1. A platform from or on which aircraft are flown,

landed or accommodated, the platform being attachable to a carrier vehicle and controllably moveable such that it may be substantially isolated from selected translational motion components of the carrier vehicle.

2. A platform as defined in claim 1 that compensates for motion of the carrier vehicle and/or landing aircraft.

3. A platform as defined in claim I or 2, with the platform movement controlled in response to an information source regarding the motion of the carrier vehicle and/or the aircraft.

4. A platform defined in claim 3 where the information source is provided from satellite technology.

5. A platform defined in claim 3 or 4 where the information source is provided from instruments and/or people upon any of the carrier vehicle, the aircraft or the platform.

6. A platform defined in any preceding claim comprising a sensor to detect landed or approaching aircraft.

7. A platform defined in claim 6 that moves to cushion the landing of an aircraft in response to information from the sensor.

8. A platform as defined in any preceding claim in which the platform is attachable to the carrier vehicle via a variable length support member.

BP.09.0647 9. A platform as defined in claim 8 in which the variable length support member comprises an articulated support member having support sub-members attached to each other via one or more flexible joints.

10. A platform as defined in any of preceding claim comprising a pivoting joint between the platform and the carrier vehicle.

11. A platform as defined in any preceding claim in which a support member extends between the platform and the carrier vehicle, an end of the support member being linearly movable to different locations on the carrier vehicle and/or platform.