WO2010023253A1

WO2010023253A1 - A bird collision avoidance system

Info

Publication number: WO2010023253A1
Application number: PCT/EP2009/061094
Authority: WO
Inventors: William Michael Butler
Original assignee: Sa Speir Aviation Limited
Priority date: 2008-08-28
Filing date: 2009-08-27
Publication date: 2010-03-04
Also published as: IE20090653A1; IES20090654A2

Abstract

The present invention is directed to a bird collision avoidance system (100, 200), wherein the bird collision avoidance system (100, 200) is installed on an aircraft (102) and comprises a bird detection unit (104) and an associated bird repelling unit (110, 206), wherein, the bird repelling unit (110, 206) comprises at least one sound emitter to generate a sound signal having a variable frequency, focussed beam (114) pattern which is directed along a projected flight path of the aircraft (102). The advantage of using sound signal having a focussed beam pattern is that the beam can be focussed substantially directly at a bird in the projected flight path of the aircraft and can be used to repel the bird away from the projected flight path of the aircraft. By focussing the beam only at the bird in the projected flight path of the aircraft, other birds in the vicinity but not in the projected flight path of the aircraft will not hear the sound signal. A modulated ultrasound signal may be used as the sound signal having a focussed beam pattern. The bird collision avoidance system may also be mounted on wind turbines.

Description

"A bird collision avoidance system"

Introduction

The present invention relates to bird collision avoidance system. In particular, the present invention is directed to an aircraft based system that comprises a bird detection unit and a bird repelling unit.

With the increase in the number of aircraft worldwide and a recorded increase in the number of birds worldwide, the probability that an aircraft will suffer a bird strike has increased in recent years. It has been reported that there were 0.56 bird strikes per 10,000 flights worldwide in 1990. By 2008, this had increased to 1.6 bird strikes per 10,000 flights worldwide.

It should be noted that throughout the following specification, the term "bird strike" shall be understood to refer to the act of a bird or any land-based or airborne animal striking an aircraft whilst the aircraft is either on the ground or in-flight.

The grassy and watery habitats which tend to surround airports, and the cavernous hangers and airport buildings with large flat roofs make for perfect nesting environments for many species of birds.

Bird strikes pose a large risk to passengers of aircraft, the pilots and crew on aircraft and to the aircraft themselves due to the sudden and unexpected nature of their occurrence and also due to the ability of a bird strike to cause catastrophic damage to the aircraft. In many cases, a bird strike into a running engine will lead to a disablement of that engine, which is obviously highly dangerous to the passengers of the aircraft.

The vast majority of bird strikes (somewhere in the region of 85% in fact) occur during the three critical phases of flight: take-off, approach and landing as it is in this altitude range that the majority of birds can be found. During the three critical phases, pilots have little time to react to a sudden failure of one of the engines of their aircraft. Furthermore, the aircraft will be relatively close to the terrain during these three phases and the pilot has little time to recover before having to find a safe landing location for the aircraft. Bird strikes during these flight phases are particularly dangerous and thus bird collision avoidance during these phases is of particular importance.

As aircraft engine development has continued to produce quieter engines, birds are receiving less warning time than before and consequently a large number of bird strikes have been recorded in recent years. The problem of bird strikes is set to be further exacerbated by engine developments as many aircraft manufacturers are turning to twin engines for some of their aircraft types that would previously have used four. This is due to the advancements and developments in engine power and efficiency. A failure of one of the two engines due to a bird strike poses a more serious threat to the safety of the passengers and crew of an aircraft when compared with a failure of one engine out of four. Thus, the aircraft engine developments have not only increased the bird strike rates but have also increased the safety threat due to a bird strike on many aircraft types. There is clearly a serious safety threat which could lead to the loss of lives and/or numerous serious injuries as a result of aircraft crashes caused by both engines failing on a twin aircraft due to a bird strike.

Aside from the danger for passengers and crew, the implications of a bird strike can be costly to aircraft operators. It is estimated that bird strikes cost the airline industry approximately US$1.2 billion in 2002. Any bird strikes which damage the aircraft are very costly as the aircraft needs to be repaired and certified for flight again. In addition, a new aircraft will have to be flown in to replace the damaged aircraft on the aircraft operator's schedule and the disruption to the flight schedule can take hours, or in extreme cases, days to resolve. The delays caused by the disruption can end up affecting numerous flights and costing the airline operator significant amounts of money. Aside from the serious, damaging bird strikes, every bird strike must be reported to an appropriate authority. The reporting and analysis of bird strikes which do not damage the aircraft are still costly in terms of manpower to the aircraft operators and regulatory authorities. It has been reported that even these non-damaging bird strikes which turn out to be false alarms can costs in the region of US$1 ,000 to investigate each time.

It has also been known for airline operators to institute legal proceedings against airport authorities for the financial costs suffered as a result of bird strikes. Therefore, the consequences of a bird strike are not confined to the aircraft operators alone, and airport authorities must also endeavour to minimise the risk of an aircraft that uses their airport from encountering a bird strike. Moreover, if a bird strike occurs on a runway, the airport authority must delay all incoming flights until debris has been cleared and the runway has been thoroughly inspected. Further financial costs may be incurred by the airport authority as a result of these delays.

Several solutions have been proposed in light of the above-mentioned problems.

A number of ground based systems are presently used in order to scare birds away from an airport. However, none of the systems have proved to be reliable and consistently effective. Scarecrows and bird kites have been employed in the past but habituation has resulted in the effectiveness of the scarecrows and bird kites being diminished over time. A robotic model falcon was Mailed at Fiumicino airport in Rome during 2008. The trial was relatively successful with the airspace in proximity to the airport free of birds for approximately 1.5 hours after each flight of the robotic model falcon. The disadvantage of this method is that an operator is required and the take-offs and landings must be suspended whilst the robotic model falcon is in flight.

A number of ground based noise emitters are known from the prior art. Distress calls specific to a certain species will move the majority of that species from the area within a relatively short time. Predator calls may be used to move certain types of birds from a particular area. However, many prior art emitters use the same tone and frequency during the emission of the calls, and a regular pattern is detected. Birds become used to the pattern and habituation sets in as the birds become accustomed to the noises from the emitters. This is particularly aggravated as the noises in prior art devices are omni-directional and do not distinguish between birds in the projected flight path of an aircraft and those that do not pose any threat. Therefore, even though some of the birds do not pose any threat, they will still hear the noise emitted and this will increase their rate of habituation, thus reducing the period of effectiveness of the noise emitter. Random frequency emitters and random pattern emitters have been developed to overcome this problem however, habituation still occurs.

Further solutions to the problem of bird strikes are found in the use of pyrotechnics and laser beams. Both of these solutions have drawbacks.

Pyrotechnics are useful as they may be aimed in a certain direction to guide the birds to fly away in an opposite direction. Thus, the birds may be guided away from the runway and associated airspace and flight paths so that the pyrotechnics do not scare the birds to fly directly into an oncoming aircraft. The pyrotechnics typically require an operator to carry out the task of operating the pyrotechnics, and the take-offs and landings must be suspended whilst the pyrotechnics are being fired. This is expensive and is rarely operated in many airports until after a bird sighting has been reported by a pilot or by air traffic control. Also, the pyrotechnics can be quite loud, indeed of the order of 15OdB, and therefore they cause omni-directional noise pollution which is unsatisfactory to people living in close proximity to the airport.

A laser beam has been found to be useful in scaring birds from an area. The laser beam is pointed directly at the birds and the intensity and light-stick effect of the laser beam frightens the bird and causes the bird to fly away from its current location. Again, although the laser beam may be used to direct birds to fly away in a particular direction, away from the runway and associated airspace, the laser must be manned by an operator and furthermore, there have been recent problems associated with the shining of the laser into the eyes of the pilots which is a hazard to the safe operation of the aircraft by the pilot. The laser is only effective when shone directly in front of or to the side of the birds. It will not scare birds when shone onto the rear of the birds. The effectiveness of such lasers is reduced in high light conditions.

Bird detection radars have been used to monitor, in real-time, the population of birds close to the airport. However, these types of radar are not accurate enough to be used in conjunction with the laser beam or pyrotechnics systems in order to create an autonomous bird scaring system which does not need any operator input. Other above-described systems such as the omnidirectional noise emitters may be operated automatically by the radar without human input, however, as previously mentioned these omni-directional noise emitters suffer from habituation problems. Additionally, these systems do not specifically steer birds away from the projected flight path of an aircraft.

A general problem with ground based systems is that the systems are usually not situation specific, and the noise emitters will "fire" at random or predetermined intervals once in a while to scare birds away, although it may not be necessary at the time. As a result, the rate of habituation to the sounds is increased and the effectiveness of the systems diminish. It is a goal of the present invention to provide an apparatus/method that overcomes at least one of the above-mentioned problems, and in particular to reduce the rate of habituation to bird repelling noises.

Summary of the Invention

The present invention is directed to a bird collision avoidance system, wherein the bird collision avoidance system is installed on an aircraft and comprises a bird detection unit and an associated bird repelling unit.

The advantage of using an aircraft based system is that habituation is less likely to occur as the source of the bird repelling unit is moving and will thus, by its very nature, be in different spatial points when it is discharged. The birds will sense the bird repelling unit emanating from differing source locations and the habituation to the bird repelling unit will be lessened.

Also, an effective bird scaring system could reduce the amount of development costs required to develop a new engine because an effective bird scaring system, as described above, would reduce the number of statistical bird strikes and therefore certification and development of new engines would only need to account for the reduced probability of a bird strike. Fewer bird strikes would also be financially beneficial for the aircraft operators, the airport authorities, and most importantly would make air travel safer for passengers and aircraft crew.

It may appear to be a straightforward operation to place the bird collision avoidance system on the aircraft, however, it is very counterintuitive. Aircraft manufacturers would prefer not to have the added expense of more machinery and parts to initially purchase and subsequently maintain. Furthermore, the added weight of the bird collision avoidance system components will reduce the range of the aircraft as the aircraft will be less fuel efficient. Whilst the placement of existing ground based bird collision avoidance system and bird scarers on an aircraft may appear to be a conventional option, there are in fact numerous reason, as mentioned above, as to why such an approach would not be considered by many people in the aircraft manufacturing and aircraft operating business.

In a further embodiment, the bird repelling unit comprises at least one sound emitter to generate a sound signal having a focussed beam pattern which is directed along a projected flight path of the aircraft.

Throughout the specification, the term "focussed beam pattern" shall be understood to define a sound signal that has a relatively high directivity such that the sound signal has as high Q value.

Throughout the specification, the term "projected flight path" shall be understood to define the actual flight path vector "FPV", and planned flight path when following pre-assigned Standard Instrument Arrival routes "STARS" and Standard Instrument Departure routes "SIDS", of an aircraft and a predetermined volume of space surrounding the actual FPV and planned flight path of an aircraft, within which space, the presence of a bird would pose a threat to the safety of the aircraft.

The advantage of using sound signal having a focussed beam pattern is that the beam can be focussed substantially directly at a bird in the projected flight path of the aircraft and can be used to repel the bird away from the projected flight path of the aircraft. By focussing the beam only at the bird in the projected flight path of the aircraft, other birds in the vicinity but not in the projected flight path of the aircraft will not hear the sound signal, and, therefore habituation to the sound signal will be slower than with omni- directional noise emitters as known from the prior art. Furthermore, the level of noise nuisance in the environs of the airport will be reduced which will have benefits for other animals and for people living close proximity to the airport.

In a further embodiment, the bird repelling unit comprises at least one sound emitter to generate a sound signal having a varying frequency beam pattern which is directed along a projected flight path of the aircraft.

The advantage of using a varying frequency beam pattern is that a relatively long range sound beam may be used at distances between 100 and 800 metres for example, and would be designed to scare birds away from the aircraft. A mid-range sound beam may be used at distances between 50 and 100 metres for example, and would be designed to scare birds away from the wings of the aircraft. A short-range sound beam may be used at distances between 0 and 50 metres for example, and would be designed to scare birds away from the engines of the aircraft as the engines are the most valuable components on the aircraft which must be protected to increase the chances of the passengers of the aircraft surviving a bird strike.

In a further embodiment, the varying frequency beam pattern comprises an infrasound signal, an acoustic signal and/or a modulated ultrasound signal, all of which carry a bird repelling sound.

Throughout the following specification, the term "modulated ultrasound signal" shall be understood to refer to a sound signal that is generated as a parametric sound beam which modulates an audio signal on an ultrasound signal. The ultrasound signal self-demodulates as it passes through non- linearities in the air. Ultrasound signals are generally defined as sound signals having a frequency greater than 20,000 Hz. The bird repelling sound that is modulated by the ultrasound signal may be a distress call, an alarm call, a predator call or other such noises for repelling birds as are known from the prior art such as bangs.

In a further embodiment, the sound emitter generates a signal which varies in frequency from infrasound to ultrasound.

In a further embodiment, the sound emitter receives pressurised air which is tapped from one or more engines of the aircraft.

In a further embodiment, the bird repelling unit further comprises at least one light emitter which is operated in conjunction with the at least one sound emitter.

In a further embodiment, the light emitter generates a laser beam.

In a further embodiment, the bird detection unit comprises a light source and a reflected light detector to detect scattered light reflected back by a bird in the projected flight path of the aircraft.

In a further embodiment, the bird detection unit comprises at least one camera to capture images of the landscape in the projected flight path of the aircraft and an associated image analysis unit to detect if a bird is in the projected flight path of the aircraft.

In a further embodiment, GPS data, speed data, directional data, FPV data, SID data, STAR data, TCAS data, and terrain maps are used to generate images of the expected landscape in the projected flight path of the aircraft in order to assist the bird detection unit to detect birds in the captured images of the landscape in the projected flight path of the aircraft and to avoid false warnings form other aircraft in the vicinity.

In a further embodiment, the bird detection unit comprises a thermal imaging unit to capture thermal images of the landscape in the projected flight path of the aircraft and an associated thermal image analysis unit to detect if a bird is in the projected flight path of the aircraft.

The phrase "the landscape in the projected flight path" is used to define the visual panorama that is seen by an observer looking into the projected flight path of the aircraft from the aircraft.

In a further embodiment, the bird detection unit comprises a sonar system to detect if a bird is in the projected flight path of the aircraft.

In a further embodiment, the bird detection unit comprises a radar system to detect if a bird is in the projected flight path of the aircraft.

In a further embodiment, the at least one sound emitter initially establishes the sound signal in a direction along a central axis of the projected flight path and subsequently sweeps the sound signal outwardly from the central axis towards an outer boundary of the projected flight path to repel birds away from the aircraft.

In a further embodiment, the at least one sound emitter is mounted on the aircraft on one or more of: a leading edge of a wing, a flap-track fairing, a leading edge of a tail fin, a fin tip, a nose cone, a wing root, horizontal stabilizer, an engine inlet cowling or casing, an engine nose cone, an engine pylon, a landing gear assembly and/or an engine casing.

In a further embodiment, the bird repelling unit is activated automatically by the bird detection unit.

In a further embodiment, the bird collision avoidance system further comprises a bird repelling unit activator located in a cockpit of the aircraft to permit the bird repelling unit to be activated manually by a pilot of the aircraft.

In a further embodiment, the bird collision avoidance system receives data relating to one or more of: engine output power, ground speed, altitude and aircraft position to determine whether the bird repelling unit may be safely activated.

In a further embodiment, the direction of the generated sound signal relative to a longitudinal axis of the aircraft is varied dependent upon a flight phase of the aircraft.

The present invention is further directed towards a bird collision avoidance system, wherein the bird collision avoidance system is mounted on a wind turbine and comprises a bird detection unit and an associated bird repelling unit, wherein, the bird repelling unit comprises at least one sound emitter to generate a sound signal having a focussed beam pattern which is directed in front of the blades of the wind turbine.

The phrase "in front of the blades of the wind turbine" should be interpreted as a volume of space within which the presence of a bird, or indeed other such animal, presents a danger to the bird and a risk of damage to the wind turbine and the blades of the wind turbine in particular.

The advantage of using sound signal having a focussed beam pattern is that the beam can be focussed substantially directly at a bird in front of the blades of the wind turbine and can be used to repel the bird away from the blades of the wind turbine. By focussing the beam only at the bird in front of the blades of the wind turbine, other birds in the vicinity but not in front of the blades of the wind turbine will not hear the sound signal, and, therefore habituation to the sound signal will be slower than with omni-directional noise emitters. In a further embodiment, the bird repelling unit comprises at least one sound emitter to generate a sound signal having a varying frequency beam pattern which is directed along a projected flight path of the aircraft.

In a further embodiment, the varying frequency beam pattern or the focussed beam pattern comprises an infrasound signal, an acoustic signal and/or a modulated ultrasound signal, all of which carry a bird repelling sound.

In a further embodiment, the light emitter generates a laser beam.

In a further embodiment, the bird detection unit comprises a light source and a reflected light detector to detect scattered light reflected back by a bird in front of the blades of the wind turbine.

In a further embodiment, the bird detection unit comprises at least one camera to capture an image of the landscape in front of the blades of the wind turbine and an associated image analysis unit to detect if a bird is travelling in front of the blades of the wind turbine.

In a further embodiment, an image of the expected landscape in front of the blades of the wind turbine is known and is used to assist the bird detection unit to recognise if a bird is in the captured image of the landscape in front of the blades of the wind turbine. In a further embodiment, the bird detection unit comprises a thermal imaging unit to capture thermal image of the landscape in front of the blades of the wind turbine and an associated thermal image analysis unit to detect if a bird is travelling in front of the blades.

In a further embodiment, the bird detection unit comprises a sonar system to detect if a bird is in front of the blades of the wind turbine.

In a further embodiment, the bird detection unit comprises a radar system to detect if a bird is in front of the blades of the wind turbine.

Detailed Description of Embodiments

The invention will be more clearly understood by the following description of some embodiments thereof, given by way of example only with reference to the accompanying drawings, in which:

Fig. 1 is a top view of an aircraft employing the bird collision avoidance system of the present invention;

Fig. 2 is a top view of an aircraft employing a further embodiment of the bird collision avoidance system of the present invention;

Fig. 3 is a side view of the aircraft of Fig. 2 employing the bird collision avoidance system during take-off;

Fig. 4 is a side view of the aircraft of Fig. 1 employing the bird collision avoidance system during approach; Fig. 5 is a side view of the aircraft of Fig. 1 employing the bird collision avoidance system during landing; and,

Fig. 6 is a top view of an aircraft employing a further embodiment of the bird collision avoidance system of the present invention.

Referring to Figure 1 , there is provided a bird collision avoidance system indicated generally by reference numeral 100. The bird collision avoidance system 100 is installed on an aircraft indicated generally by reference numeral 102. The aircraft 102 is shown to be an airplane in the following drawings, however, it will be understood that the invention is equally applicable to aerostats such as balloons, airships and blimps and aerodynes such as helicopters, gliders and gyroplanes.

A starboard bird detection unit 104 is mounted on a starboard wing 106 of the aircraft 102. The starboard bird detection unit 104 detects birds in a starboard- side detection zone 108. This detection zone 108 is in the projected flight path of the aircraft 102. In a preferred embodiment, the detection zone 108 is 800 metres in longitudinal dimension.

A port bird repelling unit 110 is mounted in a leading edge of the port wing 112 of the aircraft 102. The port bird repelling unit 110 comprises an emitter that produces a sound signal. The beam 114 is swept over a portion of the projected flight path of the aircraft 102 between a central boundary 116 and an outer boundary 118.

It is important to note that in Fig. 1 , for illustrative purposes and for clarity, the starboard bird detection unit 104 is shown mounted on the starboard side of the aircraft 102, and the port bird repelling unit 110 is shown mounted on the port side of the aircraft 102. However, in a preferable embodiment, the starboard bird detection unit 104 on the starboard wing 106 would activate a starboard bird repelling unit (not shown) on the starboard wing 106, and, a port bird detection unit (not shown) on the port wing 112 would activate a port bird repelling unit 110 on the port wing 112. In another embodiment, the starboard bird detection unit 104 may activate both the starboard bird repelling unit (not shown) and the port bird repelling unit 110. Similarly, the port bird detection unit (not shown) may activate both the starboard bird repelling unit (not shown) and the port bird repelling unit 110.

In use, the starboard bird detection unit 104 may comprise a light source (not shown) and a reflected light detector (not shown). In one embodiment, the lights found on the landing gear and wing root of the aircraft 102 may be used as the light source, because the landing gear will be deployed during the three critical phases of take-off, approach and landing. Light will be transmitted into the detection zone 108 and will be scattered back by a bird (not shown) in the detection zone 108. The reflected light detector will detect the scattered light and automatically activate the starboard bird repelling unit and/or the port bird repelling unit 110. In a further embodiment not shown, the bird repelling unit 110 may be manually activated by a pilot (not shown) or crewmember (not shown) of the aircraft. A bird repelling unit activator (not shown), such as a button or lever, may be installed in the cockpit of the aircraft 102 to either allow manual operation of the bird repelling unit 110, or may allow a crewmember or pilot to override the automatic operation of the bird repelling unit 110.

In another embodiment of the invention, the starboard bird detection unit 104 may comprise a camera (not shown) and an image analysis system (not shown). In one embodiment, cameras used to detect objects that present potential collision hazards to aircraft during the push-back or taxiing phases of a flight may also be used as the camera for the bird detection unit during the take-off, approach and landing phases of the flight. A bird (not shown) in the detection zone 108 will be captured by the camera and sent as part of the captured camera image to the image analysis system. The image analysis system will analyse the captured camera image to scan for an image that is similar to a bird in flight. Upon detection of such an image, the starboard bird detection unit 104 will automatically activate the starboard bird repelling unit and/or the port bird repelling unit 110. Similarly to above, in a further embodiment not shown, the bird repelling units may be manually activated by a pilot or crewmember of the aircraft. Enhanced Vision Systems (EVS) as are currently being fitted to aircraft, use a single infra-red camera fitted in the nose, to give a head-up display of the runway in the cockpit to allow pilots to land in fog, cloud and other poor visibility conditions. Such an EVS may also be designed to be incorporated into the bird collision avoidance system of the present invention.

The port bird repelling unit 110 emits a focussed beam 114. In a preferred embodiment the beam 114 is in the form of a modulated ultrasound beam. The modulated ultrasound beam has a high degree of directivity, and a deterring sound such as a lower frequency engine noise, a predator call or any other such bird scaring noise is modulated onto the high frequency ultrasound signal. In a further embodiment, the beam 114 is a sound signal of varying frequency which varies ifs frequency depending on the proximity of a bird and the probability of a bird strike.

The beam 114 is initially established and directed towards the central boundary 116 at a starting point 120 and is swept in an arcing motion 122 towards an outer boundary 118. The sweeping motion 122 of the beam 114 is used to guide detected birds (not shown) out of the projected flight path of the aircraft 102. In Figure 1 , the outer boundary 118 is shown at one side of the aircraft 102, however, it will be appreciated that the boundary may be above or below the aircraft, may vary with beam frequency, and during different phases of flight, a preferred boundary may be prioritised. For example, during take-off, it may be easier to attempt to direct a bird beneath the aircraft as the aircraft is climbing and gaining altitude and therefore, the relative distance over which the bird must be guided would be less than if the bird were to be directed toward a boundary above the climbing aircraft. In a particular embodiment, the rate of climb, descent and/or angle of bank of the aircraft 102 may be taken into account to decide whether a sideward, upward or downward sweep would be most effective in guiding the detected bird out of the projected flight path of the aircraft 102. It will be appreciated that the main purpose of the sweeping motion of the beam 122 is to move the beam from a central point in the projected flight path outwardly to a point beyond the projected flight path to guide the detected bird out of the aircraft flight path.

Referring to Figure 2, a further embodiment of the bird avoidance collision system is indicated generally by reference numeral 200, wherein like parts previously described have been assigned the same reference numerals. The bird avoidance collision system 200 comprises a starboard side bird detection unit 104 and a port bird detection unit 202. The bird detection units 104, 202 are mounted on the starboard wing 106 and the port wing 112 of the aircraft 102 respectively. The starboard bird detection unit 104 detects birds in a starboard-side detection zone 108 and the port bird detection unit 202 detects birds in a port-side detection zone 204. The detection zones 108, 204 are within the projected flight path of the aircraft 102.

The bird repelling unit 206 is mounted in the leading edge of the tail fin 208 of the aircraft 102. The bird repelling unit 206 comprises an emitter that produces a beam 114. The beam 114 is swept over the projected flight path of the aircraft 102 between a starboard-side outer boundary 212 and a port-side outer boundary 210.

In use, the starboard bird detection unit 104 or port bird detection unit 202 may comprise a light source (not shown) and a reflected light detector (not shown), or a camera (not shown) and an image analysis system (not shown) as previously described above, and not repeated here for clarity and brevity.

The beam 114 is initially directed towards a central starting point 214 along a longitudinal axis of the aircraft 102, and is swept in an arcing motion 216 towards the starboard-side outer boundary 210 or in an arcing motion 218 towards the port-side outer boundary 212. In one embodiment, the sweeping motion of the beam 216, 218 may depend on which bird detection unit 104,

202 activated the bird repelling unit 206 and will guide the detected bird out of the projected flight path of the aircraft 102. As previously, the sweeping motion of the beam 216, 218 may alternatively be in an upward or downward direction to guide birds over or under the aircraft 102 respectively.

With reference to Figures 3 to 5, wherein like parts have been assigned the same reference numerals as before, the bird collision avoidance systems 100, 200 previously described are illustrated in use during three critical phases of flight: take-off, approach and landing respectively.

Referring to Figure 3, there is provided an aircraft 102 emitting the beam 114 from the leading edge of the tail fin 208 of the aircraft 102 during take-off. The flight path vector 300 of the aircraft 102 varies between 0° and approximately minus 10° relative to the angle of attack of the aircraft 102 during takeoff and initial climbout, and the beam 114 is directed towards the flight path vector 300.

Referring to Figure 4, there is provided an aircraft 102 emitting a beam 114 from the leading edge of the starboard wing 106 of the aircraft 102 during approach. The flight path vector 400 of the aircraft 102 during approach can vary up to -10° relative to the angle of attack of the aircraft 102, and the beam 114 is directed towards the flight path vector 400. Referring to Figure 5, there is provided an aircraft 102 emitting a beam 114 from the leading edge of the starboard wing 106 of the aircraft 102 during landing. The aircraft 102 is shown landing on a runway 500, and a portion of the beam 114 is reflected off the runway 500 to form a reflected beam signal 502. The flight path vector 504 of the aircraft 102 during landing is approximately -3° relative to the angle of attack of the aircraft 102, and the beam 114 and reflected beam 502 is substantially directed along the flight path vector 504.

With reference to Figure 6, when a bird 608 is detected which poses a bird strike threat, a high power, low attenuation infrasound beam 606 is first generated along the projected flight path of the aircraft102. The infrasound beam 606 alerts the bird 608 of the presence of the aircraft 102. The width 607 of the infrasound beam 606 is relatively wide.

If the distance between the bird 608 and the aircraft 102 reduces, and the bird continues to remain a strike threat, the beam will vary in its frequency and increase its frequency into the normal audio range. The acoustic beam 604 is now generated along the projected flight path of the aircrafti 02. The acoustic beam 604 will become more focussed due to the increased acoustic frequency and the width 605 of the acoustic beam 604 is narrower than that of the infrasound beam 606. The acoustic beam 604 may be generated to protect the wings of the aircraft 102.

If the bird 608 remains close enough to pose a direct and immediate threat to the aircraft 102, the frequency of the acoustic beam 604 will be varied. The frequency will be increased to become a highly directional modulated ultrasonic beam 602, which is generated along the projected flight path of the aircraft 102. In particular, the modulated ultrasonic beam 602 may be directed in front of the engines to protect the engines and to deviate the bird 608 away from the engine intakes, in the first instance. Thus, the beam frequency may vary from being initially an infrasonic sound beam to increase frequency and thus reducing beam spread as bird-to-aircraft distance decreases. If the detected bird continues to pose an immediate threat of strike, the beam frequency increases to a modulated ultrasonic beam, which is highly focussed and directed at the bird to scare the bird away from the aircraft 102. The sound beam frequency will vary from infrasound, below 50Hz, increasing through frequencies primarily used by birds to detect a threat, commonly from 300Hz to approximately 8kHz, up to ultrasound frequencies greater than 2OkHz, which may carry a modulated audio signal.

The sound may be electrically generated using piezoelectric crystals and the aircraft structure as a "loudspeaker" sounding board, or may use compressed air from the engine compressor, electronically controlled to generate varying and particular acoustic frequencies. As it is expected that there would be a minimum of one sound generator per engine, the generators may be interlinked to create a more focussed sound beam by electronically linking the sound generator controls.

As hereinbefore mentioned, the closest zone has a focussed modulated ultrasound beam 602. The focussed modulated ultrasound beam 602 has a high degree of directivity due to its high Q factor. In one embodiment, the focussed modulated ultrasound beam has a spread of at most 15 degrees, beyond which 90%dB attenuation is observed. In a further embodiment, the focussed modulated ultrasound beam has a spread of at most 10 degrees, beyond which 90%dB attenuation is observed. In yet a further embodiment, the focussed modulated ultrasound beam has a spread of at most 5 degrees, beyond which 90%dB attenuation is observed.

In a further embodiment, the power source may be a supply of compressed air tapped from the engine high pressure compressor, which is controlled electronically to generate a sound waves of varying frequency. A valve may be used to control the supply of compressed air from the engine compressor to an air horn or similar sound generating device. Alternatively a piston type generator powered by compressor air, may be used to generate a loud bang, similar in effect to the bang produced by pyrotechnics currently used to scare birds.

The ultrasonic beam may also be created using electrically activated piezoelectric crystals mounted in leading edges of the wings or engine inlet or nose-cone.

In a further embodiment (not shown), one or more bird detection unit(s) and one or more bird repelling unit(s) may be mounted in one of, or on a combination of, a leading edge of a wing, a leading edge of a tail fin, a tail tip, a track-flap fairings, an underside of the aircraft, a horizontal stabilizer, an engine inlet cowling or casing, an engine nose cone, an engine pylon, a wing root, a landing gear assembly, a front nose cone, a capsule of a balloon and/or skids of a helicopter.

Throughout the preceding specification, reference has been made to a "bird" and "detected bird", it will be readily understood that such references are also meant to refer to birds that form part of the class of Aves. Moreover, the terms should be interpreted in a wider sense to encompass flocks of birds, other animals capable of flight and land-based animals such as deer, foxes and rabbits which are found in habitats close to airports and wind farms.

In a further embodiment, the at least one emitter uses speed data to account for Doppler effects when generating and establishing the beam 114, and in particular the modulated ultrasound beam. In alternative embodiments, it is foreseen to use a sonar-based system to detect the presence of birds in the projected flight path of the aircraft 102. The sonar may be a passive or active sonar which could use noise equalisation techniques to cancel the effect of noise emanating from the engines of the aircraft 102.

In yet another embodiment, thermal imaging could be used to detect birds in the projected flight path of an aircraft 102. The thermal cameras may be mounted on the aircraft and an associated thermal imaging analysis system may be used to detect birds in the projected flight path. The thermal imaging system can detect the presence of any warm-blooded creatures, such a birds in the projected flight path of the aircraft. It is also envisaged that the thermal imaging system may be used to determine the direction of flight of the bird by analysing any changes of temperature of the detected bird, and by plotting the flight vector of the bird over a time period, such as 0.5 seconds up to 3 seconds.

In a further embodiment, aircraft-based radar may be used to detect a bird, or particularly a flock of birds in the distance. This may be then used to automatically trigger the bird repelling unit on the aircraft 102.

Any of the above mentioned bird detection systems may be used in conjunction with one another to provide an overall bird detection system for mounting on an aircraft 102.

In a further embodiment, different aircraft may generate different tones and frequencies to lessen the rate of habituation of the birds.

The bird repelling unit 110 may preferably be a noise emitter as it is believed that these are more effective than light emitters by virtue of the fact that the direction in which the bird faces is of no consequence to the successful operation of a noise emitter. However, light emitters such as a laser may be used instead of the noise emitters or in conjunction with the noise emitters to provide the bird repelling unit 110. It is also foreseen that the bird collision avoidance system may be mounted on a wind turbine to protect both bird and the blades of a wind turbine from becoming damaged. A space in front of the blade of the wind turbine may be deemed as a "no-fly" zone and any birds entering this zone may be repelled in case they would fly towards the blades of the turbine and damage the blades of the wind turbine.

It is envisaged that it will be easier to detect birds that pose a threat to the safe operation of the wind turbine as the wind turbine is stationary and the landscape images, devoid of any birds, that a camera mounted on the wind turbine should capture will be relatively easy to store for comparisons with actual captured images. This is in contrast to the system described above for aircraft as the landscape images captured by the aircraft and the expected landscape images are constantly changing due to the motion of the aircraft.

The location of the sound generators may be on the blade tips, where the relative airspeed may be used as a power source, and may be electronically modified to create a sound beam.

In addition, an electrically powered, piezoelectric generated, modulated ultrasonic sound generator may be mounted directly on the generator casing of wind turbine, to scare birds clear of the no-fly zone.

In the specification the terms "comprise, comprises, comprised and comprising" or any variation thereof and the terms "include, includes, included and including" or any variation thereof are considered to be totally interchangeable and they should all be afforded the widest possible interpretation and vice versa.

The invention is not limited to the embodiments hereinbefore described which may be varied in both construction and detail with the scope of the appended claims.

Claims

1. A bird collision avoidance system, characterised in that the bird collision avoidance system is installed on an aircraft and comprises a bird detection unit and an associated bird repelling unit.

2. A bird collision avoidance system as claimed in claim 1 , wherein, the bird repelling unit comprises at least one sound emitter to generate a sound signal having a focussed beam pattern which is directed along a projected flight path of the aircraft.

3. A bird collision avoidance system as claimed in claim 1 , wherein, the bird repelling unit comprises at least one sound emitter to generate a sound signal having a varying frequency beam pattern which is directed along a projected flight path of the aircraft.

4. A bird collision avoidance system as claimed in any of claims 2 or 3, wherein, the varying frequency beam pattern comprises an infrasound signal, an acoustic signal and/or a modulated ultrasound signal, all of which carry a bird repelling sound.

5. A bird collision avoidance system as claimed in claim 3, wherein, the sound emitter generates a signal which varies in frequency from infrasound to ultrasound.

6. A bird collision avoidance system as claimed in claim 3, wherein, the sound emitter receives pressurised air which is tapped from one or more engines of the aircraft.

7. A bird collision avoidance system as claimed in any preceding claim, wherein, the bird repelling unit further comprises at least one light emitter which is operated in conjunction with the at least one sound emitter.

8. A bird collision avoidance system as claimed in claim 7, wherein, the light emitter generates a laser beam.

9. A bird collision avoidance system as claimed in any preceding claim, wherein, the bird detection unit comprises a light source and a reflected light detector to detect scattered light reflected back by a bird in the projected flight path of the aircraft.

10. A bird collision avoidance system as claimed in any of claims 1 to 8, wherein, the bird detection unit comprises at least one camera to capture images of the landscape in the projected flight path of the aircraft and an associated image analysis unit to detect if a bird is in the projected flight path of the aircraft.

11. A bird collision avoidance system as claimed in claim 10, wherein GPS data, speed data, directional data, FPV data, SID data, STAR data, TCAS data, and terrain maps are used to generate images of the expected landscape in the projected flight path of the aircraft in order to assist the bird detection unit to detect birds in the captured images of the landscape in the projected flight path of the aircraft and to avoid false warnings form other aircraft in the vicinity.

12. A bird collision avoidance system as claimed in any of claims 1 to 8, wherein, the bird detection unit comprises a thermal imaging unit to capture thermal images of the landscape in the projected flight path of the aircraft and an associated thermal image analysis unit to detect if a bird is in the projected flight path of the aircraft.

13. A bird collision avoidance system as claimed in any of claims 1 to 8, wherein, the bird detection unit comprises a sonar system to detect if a bird is in the projected flight path of the aircraft.

14. A bird collision avoidance system as claimed in any of claims 1 to 8, wherein, the bird detection unit comprises a radar system to detect if a bird is in the projected flight path of the aircraft.

15. A bird collision avoidance system as claimed in any of claims 2 to 14, wherein, the at least one sound emitter initially establishes the sound signal in a direction along a central axis of the projected flight path and subsequently sweeps the sound signal outwardly from the central axis towards an outer boundary of the projected flight path to repel birds away from the aircraft.

16. A bird collision avoidance system as claimed in any of claims 2 to 15, wherein, the at least one sound emitter is mounted on the aircraft on one or more of: a leading edge of a wing, a flap-track fairing, a leading edge of a tail fin, a fin tip, a nose cone, a wing root, horizontal stabilizer, an engine inlet cowling or casing, an engine nose cone, an engine pylon, a landing gear assembly and/or an engine casing.

17. A bird collision avoidance system as claimed in any preceding claim, wherein, the bird repelling unit is activated automatically by the bird detection unit.

18. A bird collision avoidance system as claimed in any preceding claim, wherein, the bird collision avoidance system further comprises a bird repelling unit activator located in a cockpit of the aircraft to permit the bird repelling unit to be activated manually by a pilot of the aircraft.

19. A bird collision avoidance system as claimed in any preceding claim, wherein, the bird collision avoidance system receives data relating to one or more of: engine output power, ground speed, altitude and aircraft position to determine whether the bird repelling unit may be safely activated.

20. A bird collision avoidance system as claimed in any of claims 2 to 19, wherein, the direction of the generated sound signal relative to a longitudinal axis of the aircraft is varied dependent upon a flight phase of the aircraft.

21. A bird collision avoidance system, characterised in that the bird collision avoidance system is mounted on a wind turbine and comprises a bird detection unit and an associated bird repelling unit, wherein, the bird repelling unit comprises at least one sound emitter to generate a sound signal having a focussed beam pattern which is directed in front of the blades of the wind turbine.

22. A bird collision avoidance system as claimed in claim 1 , wherein, the bird repelling unit comprises at least one sound emitter to generate a sound signal having a varying frequency beam pattern which is directed along a projected flight path of the aircraft.

23. A bird collision avoidance system as claimed in any of claims 21 or 22, wherein, the varying frequency beam pattern or the focussed beam pattern comprises an infrasound signal, an acoustic signal and/or a modulated ultrasound signal, all of which carry a bird repelling sound.

24. A bird collision avoidance system as claimed in claim 22 or 23, wherein, the sound emitter generates a signal which varies in frequency from infrasound to ultrasound.

25. A bird collision avoidance system as claimed in any of claims 21 to 24, wherein, the bird repelling unit further comprises at least one light emitter which is operated in conjunction with the at least one sound emitter.

26. A bird collision avoidance system as claimed in claim 25, wherein, the light emitter generates a laser beam.

27. A bird collision avoidance system as claimed in any of claims 21 to 26, wherein, the bird detection unit comprises a light source and a reflected light detector to detect scattered light reflected back by a bird in front of the blades of the wind turbine.

28. A bird collision avoidance system as claimed in any of claims 21 to 26, wherein, the bird detection unit comprises at least one camera to capture an image of the landscape in front of the blades of the wind turbine and an associated image analysis unit to detect if a bird is travelling in front of the blades of the wind turbine.

29. A bird collision avoidance system as claimed in claim 28, wherein, an image of the expected landscape in front of the blades of the wind turbine is known and is used to assist the bird detection unit to recognise if a bird is in the captured image of the landscape in front of the blades of the wind turbine.

30. A bird collision avoidance system as claimed in any of claims 21 to 26, wherein, the bird detection unit comprises a thermal imaging unit to capture thermal image of the landscape in front of the blades of the wind turbine and an associated thermal image analysis unit to detect if a bird is travelling in front of the blades.

31. A bird collision avoidance system as claimed in any of claims 21 to 26, wherein, the bird detection unit comprises a sonar system to detect if a bird is in front of the blades of the wind turbine.

32. A bird collision avoidance system as claimed in any of claims 21 to 26, wherein, the bird detection unit comprises a radar system to detect if a bird is in front of the blades of the wind turbine.

83. A bird collision avoidance system as claimed in any of claims 21 to 32, wherein, the bird repelling unit is activated automatically by the bird detection unit.