Bird strikes are a major safety hazard in aviation. It is assumed that more than 200 people died in civil aviation crashes related to bird strikes since 1988. The annual cost resulting from bird strikes are estimated at $1.3 billion worldwide (estimate from 2000) for commercial flights only (excluding GA aircraft and helicopters). The majority of bird strikes (85%) cause little damage.
It is estimated that 80% of the bird strikes are not reported. Sources indicate that in the past more than 6000 bird strikes were reported annually. In the UK it is mandatory to report bird strikes and in 2007 in the UK alone there were 1,299 bird strikes reported.
One of the most recent examples of a bird strike accident was US airways flight 1549 from La Guardia to Charlotte on January 15, 2009. The aircraft ditched in the Hudson river after experiencing a loss of both engines due to bird strikes.
90% of all accidents occur near airports: FAA states that less than 8% of bird strikes occur above 900meters (2,953 feet).
Analysis reveals that the major treat to airliners and executive jets is engine ingestion. Aircraft up to 5,700 kg and helicopters are most at risk from windshield penetration.
Birds do not only present a danger in the air but also on the runway.
Civil aviation authorities try to predict bird migration and to spot birds at airports. New radar systems like the British Tarsier, the Dutch ROBIN and the US Merlin systems are in use. These can provide real time alerts related to bird strikes.
Airports are encouraged to develop their bird control management plan to assess their bird strike risk and to define and implement control measures.
These measures include habitat management to remove vegetation and potential food sources. In New Zealand electrified mats are used to reduce worms that attract seagulls. One of the problems is that areas outside the airport perimeter can attract bird.
Other techniques try to scare the birds off like:
- broadcasting recorded bird distress calls appropriate to the bird species (bio acoustics like the UK Scarecrow system)
- pyrotechnics and other noise
- trained hawks and dogs
- radio controlled hovercrafts, UAV’s
- kites and balloons
There are combinations of multi sensor acoustic and radar systems that should localize and scare birds.
US patent 6407670 proposes to combine light sources, acoustics and a water canon to provide unconditioned stimuli to prevent birds from entering the airport perimeter.
All these measures seem to have some effect but still the number of bird strikes is alarming. This is of special importance if airports would be constructed at sea.
The idea that came up during the Create workshop was to avoid costly ground infrastructure and to emit sound from the approaching airplanes. The advantage would be that the airlines and airspace users which suffer from bird strikes are made responsible for bird strike avoidance rather than the airport operator.
The idea is to emit sound in front of the aircraft that will scare birds away. The sound should not be annoying to human beings. Therefore the original idea was to emit ultra sound waves in front of the aircraft. This would only be operated near airports and in airspace where concentrations of birds are detected by radar.
The sound emitted by aircraft could be the result of noise sources located at strategic locations on the aircraft.
The system should not only protect large civil airliners but also be adoptable to small aircraft and helicopters as most fatalities due to bird strikes fall in that category.
Benefits to the Air Transport System
As already stated such a system would avoid loss of life and create big benefits to airlines. These befits would not only relate to avoiding repairs but also to disrupting flight schedules.
The benefits would even be bigger for small aircraft and rotorcraft operations. As it is feasible that air taxi operations will be introduced on a large scale in Europe, these small aircraft need protection from bird strikes as well. Cost for airport operators will be kept to a minimum. Liability will remain only with the aircraft operator and many disputes between aircraft operators and airport operators can be avoided.
Likelihood of Public Acceptance
If the on board sound system would not be influencing the human behaviour or hearing, the system would be fully accepted by both passengers and people living in the vicinity of airports. In fact if the sound waves could replace pyrotechnics and other noise, light and lasers people living next to the airport will appreciate the new system. However, possible ecological concerns regarding disturbance of other animals could be an issue.
All studies that we are aware of deal with ground based systems. None have addressed the feasibility of airborne systems. (Note: we are still waiting for the technology assessment by QinetiQ). No airborne device specifically aimed at bird strike avoidance is in use today.
Credibility of the Physics
The original idea was to emit ultra sound (20 kHz and above) in front of the airplane. Literature studies indicate that bird will not hear this ultra sound. Different bird species are sensitive to different frequencies of sound. For most, this is about 1-4 kHz ( which is in the domain of audible sound of 101Hz and 20kHz) but some species are sensitive to lower and higher frequencies. The general threshold is 10kHz. Few species are sensitive to low frequency sound (20HZ -100HZ0 and few may to infrasound (below 20Hz). Tests in the UK have not demonstrated any response from birds to infrasound emissions.
Besides the frequency the sound intensity (loudness) and the relevance of the signal play an important role. Acoustic signals according to these studies are most effective when they are reinforced with activities that produce painful or death experience. ( What can birds hear, Robert C. Beason, University of California press, Davis, 2004).
Acoustic signals have to meet 3 basic conditions: detectable, audible and relevant . Constant signals will be biologically irrelevant.
If birds only react to noise in the audible sound domain, there would be a substantial effect on the people living near to airports as well if the sound would be emitted by aircraft flying overhead.
The study must verify the type of sound that would need to be emitted from the aircraft, the intensity and the altitude on descent and departure at which the system would need to be switched on as well as the effect on human beings.
The study must also verify the technical requirements for such an onboard system if the theory proves to be effective.
Criteria for Successful Incubation
The initial incubation study should identify the noise characteristics needed to scare away birds in the flight path of aircraft. Then it should verify if such a system would be acceptable for human beings in the vicinity of airports. Finally the outlines of such a system ( location, energy requirements, loudspeakers, operations) should be established. It is important to evaluate the basic capability of the proposed system to achieve sufficient safety levels regarding bird strike threats.
Only if these elements are researched and proven to be desirable and feasible, the system could be offered for regular research programs.
It is recommended to perform small scale test during the incubation period to validate the feasibility of the system.
The incubation period will initially be very dependent on expertise from biologists. Technical solutions will only be sought once a solution seems feasible.
Timescale for Incubation
A 2 year study seems to be appropriate.
Budget required for Incubation
A first estimate for the incubation would be € 1 million in total.
Partnering needs for Incubation
Several disciplines need to work together. Literature shows that some technical studies were conducted without a proper input by biologists.
The project would need to engage experts on bird behaviour, biologists, experts in the field of sound propagation, system engineers (safety assessments, etc.), aircraft engineers, human factor specialists etc.
Related and Supporting Capabilities
The study will have to be supported by airport specialists, airline operators, large/
small aircraft/ helicopter manufacturers, representatives of people living near airports etc.
Good management will be needed to ensure a positive attitude from airport operators that may want to promote their not yet fully depreciated ground based equipment.
Scalability of the Idea
The introduction of a potential system will be fully scalable. New aircraft could be fitted with the sound device. A retrofit program should be feasible. It is expected that ground based systems will stay in use for a number of years as there will be a long test period required and the introduction of a system will be gradual.
The involvement of EASA is yet unclear, but EASA has at this moment no authority over bird strike prevention at airports. However as soon as the system is aircraft based, EASA will need to certify the system.
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