TECHNICAL FIELD

The invention relates to a visual aid device for preventing wire strikes by aircraft, water-borne vehicles or land-based vehicles. In particular, the invention relates to a metal mesh device that hangs from a wire, such as an electricity transmission wire, and has high visibility for aircraft pilots and vehicle operators.

BACKGROUND OF THE INVENTION

Aircraft wire strikes are a matter of ongoing concern for both civil and military helicopters and aeroplanes. Devices to protect the occupants in case of wire strikes have been available for some years. Systems that warn the pilots of the proximity of wires have also been developed. In spite of these developments, wire strikes continue to account for about 5-20% (depending on the year) of all United States civil and military helicopter accidents.

The problem is particularly acute for helicopters because helicopters usually need to operate at low altitudes. Wires are difficult to observe, and the background combined with sunlight can obscure wires. Also, not all helicopters can be equipped with wire cutters, and some of the recently developed devices that warn a pilot of potential wire strikes are very expensive.

Most helicopter wire strikes occur during daytime with good visibility and involve experienced pilots. Wires are difficult to see, partly because of the way the human eye functions, and partly because of the effects of camouflaging. The movement of wires in sunlight and changing sunlight patterns can also obscure wires. Older wires may be difficult to see because, as they age, their colour often changes. For example, copper wires oxidise with age, turning a greenish colour that makes them difficult to distinguish from grass and trees in the background. The exact location of specific wires may change throughout the day because of fluctuating ambient temperatures, which may cause wires to sag or tighten. Sagging wires may also be blown by the wind . The pilot's view of the outside can be affected by the canopy and the vibratory environment of the cockpit. The canopy may not always be clean, which contributes to lower visibility.

The threat is growing constantly. Society's demand for constant connectivity means that thousands of new telecommunications antennas and power transmission towers, along with thousands of miles of wire, are constructed every year. In addition, wind generators and meteorological evaluation towers (METs) are being erected at record rates. Slender METs are nearly impossible to see and are often supported by nearly invisible guy-wires. Because these towers often stand just under 70 metres in height, they are not required to comply with FAA (Federal Aviation Administration) obstruction-marking requirements, making them even more difficult for helicopter pilots to see and avoid.

The near invisibility of wires results from a number of factors in addition to their size. These include atmospheric conditions, cockpit ergonomics, viewing angle, sun position, visual illusions, pilot scanning abilities and visual acuity, flight deck workload, and the camouflaging effect of nearby vegetation, among others. Even the condition of the aircraft's windows or canopy, which may be pitted, have deteriorated with age, or be dirty from dust or bug strikes, will significantly affect the pilot's ability to see wires.

A number of sophisticated and highly technical systems have been developed that can warn pilots of the proximity of wires. In addition, a combination of wire deflectors and wire cutters has been available for some time. A typical installation consists of a roof-mounted cutter and one or more cutters mounted on the fuselage of a helicopter. A deflector running vertically along the middle of the windshield guides the cables into the cutters. However, for the cutters to be effective, the helicopter must be flying at speeds greater than 30 knots and if the helicopter impacts a wire at an angle less than 60° to the wire, the cutters may not cut the wire.

Systems are in use that sense the electromagnetic fields surrounding power lines. They use this information to alert the pilot to the proximity of wires. These systems usually consist of an electronics unit mounted in the cockpit and a whip antenna mounted on the fuselage. The antenna can be placed on the nose, roof, or tail boom of the aircraft. However, the detector only senses active power lines, and the range of detection depends on the electrical power in the lines. Other types of wires such as guy wires, weak telephone lines, and non-active power lines will not be detected.

Laser and radar systems are also available. For example, a radar mounted on the nose of a helicopter can transmit a radio frequency for detecting obstacles in the flight path. The radar constantly searches for obstacles in its field of view. At a given instant of time, the system uses data from the aircraft's GPS receiver to calculate the aircraft's flight path for the next 15-20 seconds. If an obstacle is located, the pilot is given a level of alert that depends on the proximity and zone of the obstacle and is notified by a display in the cockpit that illuminates in accordance with the distance and direction to the obstacle. However, these systems are usually considered too heavy and expensive for most civil helicopters.

Obstacle collision avoidance systems consist of units located on utility and power line towers. They detect all air traffic entering a predefined warning zone and activate warning lights that illuminate the tower. These systems do not require any installations in the helicopters which can make them attractive to helicopter operators. However, there are considerable installation costs for utilities.

Coloured spherical balls mounted on wires are commonly used as markers to make the wires more visible to aircraft pilots. The balls are typically orange, yellow, red or white, and are of varying diameters. Some markers use a wire rod that wraps around the line to grip the wire. The construction includes the rods connected to the outside of the marker and lock nuts for easier live line installation. These markers use a clam shell design so that they can be installed by hand from a helicopter or installed before the power lines are strung up. The total cost can vary greatly when installing the aerial markers, depending on the number of markers that are necessary for the length of power line and the time it takes to install them.

However, coloured balls have a number of draw backs. They are usually prone to degradation and fading due to the effects of sunlight and varying weather conditions. Many are heavy (e.g. 5-15 kg) and place an undesirable load on wires. They can create high lateral forces due to wind movement. Some have a large upper surface and consequently are prone to problems from additional weight from snow accumulation. Many balls are not able to prevent water ingress. This also means that their weight may increase markedly.

The balls usually need to be fitted either while the wire is being slung or retrofitted from a helicopter which is both expensive and potentially dangerous. When fitted from a helicopter and bolted or otherwise secured in place, the helicopter needs to be hovering in immediate proximity to the wire (and surrounding wires) which has inherent dangers. The weight and shape of balls makes fitting them using an aerial drone impractical.

Light-weight plastic strips have been used instead of balls. They hang from the line, but are usually very light, small in width and are prone to wind disturbance.

The problem of wire strikes is not confined to aircrafts. In some instances, wires can hang low to the ground such that they present an obstacle or danger to land-based vehicles, particularly trucks. In a similar manner, some wires can hang low to the surface of the sea or a lake or river and may therefore be a hazard for water-borne vehicles such as ships, yachts, hovercraft and other types of boats.

The applicant has now developed a visual marker for avoiding wire strike which addresses several of the disadvantages of existing devices or systems.

It is therefore an object of the invention to provide a visual aid device for preventing wire strikes by aircraft, water-borne vehicles or land-based vehicles, or to at least provide a useful alternative to existing devices.

SUMMARY OF THE INVENTION

In a first aspect of the invention there is provided a visual aid device for avoiding wire strike by an aircraft or water-borne vehicle or land-based vehicle comprising a sheet of flexible mesh and an attachment means for attaching the sheet to a wire so that the sheet hangs from the wire, where the mesh sheet provides visual contrast between the device and the backdrop to the device. In some embodiments of the invention the mesh sheet comprises a visual contrast region to provide visual contrast between the device and the backdrop to the device.

In some embodiments the visual contrast region is provided by a centrally located hole in the mesh sheet. In other embodiments the visual contrast region is provided by one or more solid markers attached to the mesh sheet, for example strips of metal, fabric, or plastics material. In some embodiments the device of the invention comprises both a centrally located hole in the mesh sheet and one or more solid markers.

Preferably the mesh is metal mesh, for example stainless steel mesh.

In some embodiments of the invention the attachment means comprises a hanger for holding the attachment means to the wire, the hanger having a bar integrally formed with a clip located at each end of the bar, each clip being shaped to be located over and fit with the wire, and the bar being located within an elongate sleeve from which the mesh sheet hangs when in use.

Preferably the elongate sleeve is a spring, coil or tube. In some embodiments, each clip comprises an insulator to minimise heat build-up in the wire caused by friction

In some embodiments the device further comprises a support member for maintaining the shape of the mesh sheet when in use. The support member may be T-shaped having a horizontal member fixed to a vertical member where the horizontal member is located within the elongate sleeve and the vertical member is fixed to the mesh sheet.

In preferred embodiments of the invention the mesh sheet has a width in the range

0.5 to 2.0 m and a length in the range 0.5 to 2.0 m.

In a second aspect of the invention there is provided a method of providing visual aid to an aircraft pilot or operator of a land-based or water-borne vehicle for avoiding wire strike comprising suspending a device of the invention from a wire. In preferred embodiments the device is suspended from the wire or removed from the wire by manual operation by a person located in a helicopter, or by remote operation using an unmanned aircraft, or from the ground using a hot stick.

BRIEF DESCRIPTION OF THE FIGURES

Figure 1 shows a visual aid device of the invention hung on a wire stretching between two pylons.

Figure 2 shows a visual aid device of the invention .

Figure 3 shows a close-up view of a visual aid device of the invention hung on a wire. Figure 4 shows an expanded view of the upper part of a visual aid device of the invention. DETAILED DESCRIPTION

The invention relates to a visual aid device for avoiding wire strike by an aircraft or water-borne vehicle or land-based vehicle. The device comprises a sheet of flexible mesh which provides visual contrast between the device and the backdrop to the device. The device also comprises an attachment means for attaching the sheet to a wire so that the sheet hangs substantially vertically from the wire.

The mesh sheet typically has a mesh size of about 4 to 8 mm which means that, from a distance, the sheet has the visual appearance of a solid sheet of material. The mesh size may vary depending on the application. The highly visible sheet then serves as a warning to a pilot or operator of a water-borne or land-based vehicle. For example, an aircraft pilot will be warned that the aircraft may be approaching wires, or at least approaching an unusual looking object, which is likely to cause the pilot to take evasive action if necessary.

The mesh sheet may be made from any suitable material. The mesh sheet is preferably made from stainless steel. In contrast to commonly used coloured spherical balls which are usually made from a plastics material, stainless steel mesh does not readily degrade or discolour even after long and constant exposure to various weather conditions. Stainless steel mesh tends to retain a subtle shine even after aging and can reflect sunlight stimulating a visual alert in the vision of a pilot. The mesh allows for limited movement in wind. This too creates a visual stimulation effect, particularly on movement of the lower parts of the sheet.

To provide additional visual contrast between the mesh sheet and the backdrop visible to, for example, a pilot, which in many situations may be trees, mountains, rivers and other landscape features, the mesh sheet may be shaped to define a centrally located hole. This additional visual contrast region increases the likelihood of the pilot being alerted to an unexpected or unusual shape or object in their vision causing them to react and take evasive action particularly once they recognise that the shape or object is a visual aid marker for preventing wire strike.

The device may have other visual contrast regions. For example, solid markers may be attached to, or incorporated into, the mesh sheet. The markers may have any suitable shape such as a strip or band, a square, a circle or disc, or a zig-zig hazard shape, and they may be made from any suitable metal, fabric, or plastics material. They may be attached to the sheet using an adhesive or using rivets, or any other suitable attachment method. The device of the invention may typically comprise a centrally located hole in the mesh sheet as well as one or more metal strips. The device may additionally comprise an electric light for greater visibility in poor weather conditions or at night. In some embodiments of the invention, the device has one or more orange-coloured strips attached to the sheet, for example four strips that together represent a cross shape about the centrally located hole. Further, a white horizontal strip may be located across the centre of the hole and attached to the mesh sheet on either side of the hole. The horizontal strip may additionally comprise a reflector portion . As can be appreciated, the combination of the mesh sheet, the centrally located hole, the orange strips in a cross shape, and the white reflectorised horizontal strip running across the hole provides multiple visual contrast regions which all contribute to greater recognition by an aircraft or vehicle operator that there is a potential hazard ahead .

The steel mesh device of the invention may have any dimensions suitable for the application . The dimensions of the device will usually be about 0.5 to 5 m in width and about 0.5 to 5 m in height. Most often, the width will be in the range 0.5 to 2 m and the length will be in the range 0.5 to 2 m. In most situations, the device will have a generally rectangular shape, which may have its long axis orientated horizontally or alternatively its long axis orientated vertically, again depending on the situation and factors such as the terrain and the distance between pylons (or other supporting structures) . It will be appreciated that the mesh may be any network or interlaced structure of wire or metal thread and may be formed from rings or loops having a suitable diameter. Preferably the diameter of the rings or loops is in the range 4 mm to 8 mm.

The device is considerably lighter than a typical spherical ball marker of comparable size. For example, the device may weigh only about 1.7 kg which is about 30% of the weight of many spherica l ball markers. A lower weight device means there are lower swing-related forces on the wire caused by winds. The device of the invention nevertheless has sufficient weight to hang from a wire without being disturbed too much by wind .

Preferred examples of the device of the invention include a means for assisting the mesh sheet retain its shape even in strong winds. For example, the device may include a vertical support bar centrally located and fixed to the mesh sheet. The vertical support bar may be attached to, or integrally formed with, a horizontal support bar such that they form a T-shaped support. The horizontal bar is connected to, or holds, the upper edge of the mesh sheet when located on a wire.

The attachment means for attaching the sheet to a wire may be any means suitable to hold the sheet in place and hang substantially vertically from the wire. In some embodiments of the invention the attachment means comprises a hanger for holding the attachment means to the wire. The hanger preferably has a bar integrally formed with a clip located at each end of the bar, each clip being shaped to be located over and fit with the wire. The bar is located within an elongate sleeve from which the mesh sheet hangs when in use . Each clip may also be formed with a downwardly angled bar when in use to prevent the device from becoming detached from the wire due to movement from wind .

The attachment means may incorporate a mechanism to fix the device to the wire to prevent the device becoming dislodged from the wire or to prevent the device sliding along the wire. The mechanism to fix the device to the wire may, for example, be a system enabling the device to be held in place by screws or other suitable fixing components. The attachment means may also incorporate an insulator, which may be made of porcelain or any other insulating material, to prevent the formation of heat spots in the wire caused by friction from movement of the attachment means on the wire.

The device is sufficiently light-weight and easy to manoeuvre so that it can be easily, quickly and safely installed on a wire using a hot stick, drone or helicopter. In the electricity distribution industry, a hot stick is an insulated pole, usually made of fiberglass, used by electricity utility workers when engaged in live-line working on energised high-voltage electric power lines, to protect them from electric shock. The attachment means may incorporate a hook, loop or other means for engagement with the hot stick, drone or helicopter. It will be appreciated that there are some situations where it is desirable to quickly hang (and remove) a visual aid on a wire by a drone or helicopter or by other means. Examples include bush fires where wires are a hazard for aerial firefighting . When a bush or forest fire breaks out, fire fighters may be able to quickly hang visual aid devices of the invention on any wires in the region prior to fighting the fire using helicopters and other aircraft. The visual aid devices may then easily be removed, if necessary, once the fire has been extinguished. It may also be desirable to readily hang and then remove devices of the invention for agricultural work where flight paths for spraying may cross with wires.

Preferred devices of the invention are made entirely from stainless steel. This avoids any degradation or other issues when different metals components are in contact with each other. Being constructed entirely of steel also assists with radar detectability of the device which may be useful in some situations, for example during night flying.

It will be understood that the device of the invention may have two mesh sheets that hang vertically when in use. One sheet may hang in a plane substantially parallel to the line of a wire. The other sheet may hang in a plane substantially perpendicular to the line of the wire. In this embodiment of the invention, a top or bottom view of the device will resemble a cross when hanging in use.

It will also be understood that two or more devices of the invention, rather than a single device, may be located on a wire. For example, if the wire is particularly long, it may be desirable to hang two or three, or possibly more devices, along the length of the wire at suitable locations on the wire.

The invention is now further described with reference to the Figures. It will be appreciated that the invention as claimed is not intended to be limited in any way by the Figures.

Figure 1 shows an example of a device 1 of the invention. The device is shown hanging from a wire 2 stretching between two pylons 3. The device 1 is not shown to scale. It is shown larger than it would be in reality compared to the size and height of the pylons 3 for the purpose of more clearly illustrating the invention in use against a backdrop of mountains, sky and trees. It will be appreciated that the wire 2 may not be easily visible to the pilot of a helicopter or fixed-wing aircraft, but for the presence of the device 1 which has regions of visual contrast with the backdrop making it much more visible to the pilot.

The components of the device 1 are more clearly shown in Figure 2. The device 1 comprises a mesh sheet 4 which is generally rectangular in shape and has a W-shaped lower end 5. It will be appreciated, however, that the mesh sheet may have a different shape. The mesh sheet 4 is shown having a centrally located hole 6. It is also shown having two strips 7 attached to the mesh sheet 4. The strips 7 may be stainless steel strips or alternatively may be may be made of a fabric or plastics material . They may be coloured white or any other colour such as bright orange, or may be reflective or luminous to provide some lighting in darkness. Although not shown in Figure 2, the device may comprise two additional strips 7 located on the mesh sheet 4 in such a way that our four strips 7 form a cross shape. The device may also incorporate a horizontal strip (not shown) running across the hole 6 to provide an additional visual contrast region.

The hole 6 and the strips 7 provide visual contrast regions making the device 1 more easily distinguishable from the landscape backdrop when hanging from a wire. A pilot will therefore more readily be visually alerted that a wire or wires may be in close proximity or in the flight path of the aircraft. Figure 3 shows the device 1 hanging from the wire 2. A typical landscape backdrop of mountains, sky and trees is shown clearly distinguishable from the mesh sheet 4.

The device 1 requires a means for attachment to a wire. The attachment means 8, as shown in Figures 3 and 4, comprises a spring 9 extending across the upper edge of the mesh sheet 4. Rings of the mesh sheet 4 link with coils of the spring 9 so that the mesh sheet 4 hangs from the attachment means 8 supported by the spring 9. A support bar 10 is shown extending through the core of the spring 9 and forming a clip 11 at each end of the support bar 10. Each clip 11 has a loop 12 located on the wire 2 and integrally formed with an angled bar 13 that extends downwardly at an angle. The shape of each clip 11, with its loop 12 and angled bar 13, allows for the device 1 to be located on the wire 2 with some limited rotational movement with respect to the wire, but with sufficient impedance to dislocation by movement due to wind.

The support bar 10 also comprises a centrally located loop 14 for engagement with a hook which may be fixed to the end of a hot stick or longline operated from a helicopter or drone, or operated from the ground, for locating the device 1 on the wire 2 or for removing it from the wire 2.

One important advantage of the device of the invention is that its low weight, compared with other devices such as coloured spherical balls, means that a drone may be used for locating the device on a wire or removing the device from a wire. The ability to use an unmanned drone avoids the high cost of using a helicopter and avoids the inherent dangers of using a helicopter in close proximity to wires. In other situations, a person may be able to install or remove the device from the ground using a hot stick or similar implement.

The device 1 is shown having a vertical support bar 15 extending downwardly from the top of the mesh sheet 4. The vertical support bar 15 is attached to a horizontal support bar 16 which runs through the spring 9 alongside the support bar 10 and provides some rigidity and structure to the mesh sheet 4 so that it generally retains its shape in windy conditions and prevents the mesh sheet 4 from flipping over the wire 2 in strong winds.

As can readily be appreciated, the visual aid device of the invention has a number of advantages over currently employed methods for avoiding wire strikes. These include:

• inexpensive to make

• easy and inexpensive to install or remove from a wire

• light-weight

• durability

• high visibility

As used in this specification, the words "comprises", "comprising", and similar words, are not to be interpreted in an exclusive or exhaustive sense. In other words, they are intended to mean "including, but not limited to".

Although the invention has been described by way of example, it should be appreciated that variations and modifications may be made without departing from the scope of the invention as defined in the claims. Furthermore, where known equivalents exist to specific features, such equivalents are incorporated as if specifically referred in this specification.