- Introduction
- Wildlife deterrent and dispersal technology
- Wildlife-detection technology
- Conclusion: research directions
Introduction
In striving to resolve the wildlife-strike problem, the aviation industry must continue to rely on the system safety approach to reduce exposure to, and probability and severity of, wildlife strikes. Although increasing numbers of some hazardous species and a growing aviation industry pose significant challenges to reducing exposure, a reduction in risk should be achievable. New technologies will contribute to the management of wildlife-associated risk, providing wildlife-detection and deterrence capabilities, and improving the ability of aircraft to avoid wildlife encounters.
Most wildlife-management methods now employed at airports have been in use for several decades. While some new products such as chemical feeding repellents have proven relatively successful, technological advances have, for the most part, been in the refinement of existing products and techniques. Studies have shown that habitat modifications and active wildlife-management techniques remain the most successful long-term solutions when implemented by skilled operators.
Research on new methods to reduce bird-strike probability is currently being pursued on two fronts:
- deterring and dispersing wildlife using technologies that play to recently discovered sensory abilities of birds and mammals; and
- detecting birds and mammals and predicting their movements.
Wildlife deterrent and dispersal technology
Although yet to be developed, there is great appeal in the concept of an airframemounted device that disperses birds by stimulating specific bird senses to induce avoidance behaviour. Through such a device, airspace immediately ahead of an aircraft would be automatically cleared of birds. This technology could also be implemented on the ground to disperse birds from runways
Bird Avoidance Models (BAM) and Avian Hazard Advisory Systems (AHAS) may prove to be the best risk management tools for addressing bird hazards that are beyond the reach of traditional airport wildlife management programs.
Developing this technology will be difficult; its effectiveness would almost certainly vary among bird species and in different environmental conditions. Obtaining industry acceptance would also be a challenge. Nevertheless, research continues on several high-tech fronts. Readers should note that technologies discussed in this chapter are, for the most part, unproven, hypothetical research topics at this time.
Audible radar
There is evidence that some wildlife can ‘hear’ microwaves; for example, anecdotal reports suggest that birds avoid specific radar frequencies used in military applications. This phenomenon was first noted in humans who described being able to hear high-frequency clicks, buzzes, and hisses. If it is possible to deliver a warning to hazardous wildlife through microwave propagation, perhaps an effective wildlifedispersal system could be developed using this technology.
There is no clear understanding of how microwaves may affect birds, but two theories have emerged: microwaves may affect bird behaviour by producing a sense of nausea, or may provide an auditory cue of impending danger. Preliminary experimental results based on limited studies do indicate that birds can audibly detect microwaves, and that this cue can lead to avoidance behaviour. Research continues to determine how best to deliver the microwave signal; specific frequency and modulation patterns may work more effectively on different bird species. While experiments in this field are in their infancy, there has been even less research on mammal behaviour and microwaves. The testing of a prototype system is undoubtedly several years away.
In one application of this technology, microwave-emitting radar systems would be mounted on and projected ahead of aircraft to act as early-warning devices. The microwaves would be projected approximately one mile forward of an aircraft, making the system most effective at low speeds, and therefore during flight phases when aircraft are at the highest risk of being struck: takeoff and initial climb-out, and final approach and landing. Birds would detect the auditory cue, direct their attention to the oncoming aircraft, and then initiate avoidance manoeuvers.
Still, microwave-emitting radar technology faces numerous hurdles relating to product effectiveness, interference with other onboard equipment, additional airframe weight, potential effects on humans, not to mention the costs associated with research, development and implementation. This technology would not likely be applicable to military aircraft flying low-level missions, since these aircraft fly at speeds at which neither pilots nor birds would have time to react. Furthermore, airframe manufacturers and airlines will have to be convinced there’s a payoff, since additional weight greatly affects the revenue-generating capacity of commercial aircraft.
Infrasound
Low-frequency sound—or infrasound—occurs naturally in the atmosphere, created by events such as earthquakes, volcanoes, severe weather systems and jet streams. Some animals use low frequency sound to communicate, and at least some species of birds can detect infrasound. This raises the possibility of using infrasound to intentionally communicate threat warnings that will make birds leave and avoid airfields, as well as the paths of oncoming aircraft.
This technology could be used two ways. Installing infrasound generators along runways would deter birds from aircraft operating areas, including approach/departure paths. These generators could also be attached to aircraft, although various economic, technological and certification challenges might render this approach unfeasible.
Preliminary studies are underway to investigate infrasound’s potential as a wildlifemanagement tool. To be successful, birds would have to detect the infrasound, associate it with a threat and move away. As with any wildlife-management initiatives, habituation to infrasound could limit its effectiveness.
Strobe and pulsed landing lights
A number of laboratory and field studies have investigated the use of strobe lights as warning devices. While there is evidence that birds respond to strobe lights, the data does not clearly indicate that birds are inclined to avoid them.
The Transportation Development Centre—the research division of Transport Canada— commissioned a comprehensive study to examine the responses of Laughing Gulls and American Kestrels to strobe lights of varying wavelengths and frequencies. The tests
Figure 14.1 Foreign Object Ingestion Detection System (FOIDS)
clearly demonstrated that the test birds were aware of the strobe-light stimuli and responded physiologically with increased heart rates. Overt avoidance reactions were not observed, leading the authors to conclude that while strobe lights may attract the attention of birds, these tools do not result in obvious fright-and-flight responses when there are no other threatening stimuli. If birds could associate strobe lights’ visual cues with a threat—such as an approaching aircraft—they might initiate evasive responses. If no real threat exists, habituation would likely develop.
Strobe lights are mounted on many aircraft as anti-collision devices, and while birds may detect an approaching aircraft by its flashing strobes sooner than an aircraft without lights, there is no data at this time to support the concept. Another area that may hold some promise is the use of pulsed landing lights. Current research indicates that birds become aware of an approaching vehicle equipped with pulsed lights sooner than one without. Floatplane pilots on the Pacific coast of Canada insist that pulsed landing lights reduce their bird-strike incident rate.
Lasers
In recent decades, public demand has grown for non-lethal, non-injurious and environmentally benign airport wildlife-management interventions. The use of relatively low-power, hand-held Class-II and III laser devices—which are silent, highly directional, and accurate over distances— may help address this demand. Current laser technology poses little risk of eye damage to birds, and offers some promise as a bird-dispersal solution (the authors are unaware of any work undertaken to examine the effectiveness of lasers in dispersing mammals). Some of the most recent and illuminating work has been conducted at the United States Department of Agriculture’s National Wildlife Research Centre (NWRSC) in Sandusky, Ohio (www.aphis.usda.gov/ws/nwrc). In 2002, NWRSC conducted a series
Figure 14.2 Outputs from the FOIDS Signal Processor
of experiments to examine laser-avoidance behaviours of brown-headed cowbirds, European Stalrings and Canada geese, among other birds. Results demonstrated that wildlife-control methods are often species- and context-specific. For example, neither cowbirds nor starlings were repelled by lasers used in the experiments, while geese exhibited marked avoidance behaviour.
The researchers contend that lasers will prove to be valuable components of comprehensive bird-management programs; however, these experts stress that further controlled studies are needed to examine the technique in greater detail.
Available laser devices include models designed specifically for bird dispersal, and at least one brand that is used by military and law-enforcement agencies for threat deterrent; prices range from approximately USD$5,600 to USD$7,500. One manufacturer has indicated it intends to combine its laser with Dopler radar to enable site-specific, on-demand targeting of problem birds.
Wildlife-detection technology
The detection of wildlife activity is a key component of any wildlife-strike reduction program. Early detection allows time to plan and implement strategic and tactical measures to either manage birds or—if possible—adjust flight profiles.
Warning of foreign-object ingestion
Existing detection technologies could be applied to inform flight crews when an engine has ingested birds—information vital in assisting pilot decision-making following an actual or suspected bird strike.
Ongoing research and development work in the U.S. using existing radar technology may someday provide real-time warnings of bird activity that will benefit airport wildlife management teams, pilots and ATS providers.
A project is underway to develop a foreign-object ingestion-detection system (FOIDS), employing four Doppler radars mounted on the engine nacelle (see Figure 14.1). Foreign objects, including birds and bird remains, are detected and tracked as they enter an engine. The relative size of an object, its velocity, track and likely point of impact within the engine are all computed.
FOIDS could provide pilots with time-critical information on the magnitude of engine damage following an actual bird strike. Furthermore, if flight crews were in doubt as to whether or not a bird strike had occurred, FOIDS would be able to confirm, or deny, it. The value of such information is clear considering often unnecessary and costly precautionary flight returns to airports—and the even more costly repairs that result when maintenance and repairs are delayed.
The FOIDS signal processor (see Figure 14.2) is also an excellent tool for maintenance personnel. It would allow engine inspectors to confirm a FOD event and adjust engine-inspection procedures and schedules based on the severity of the event. This could both enhance safety by preventing delayed FOD-related engine failure, and reduce costs associated with unnecessary engine teardowns.
Bird avoidance models (BAM) and Avian Hazard Advisory Systems (AHAS)
Radar and other detection and telemetry techniques—including satellite telemetry— have long been used in the study of bird migration routes, nocturnal migrations, flight altitudes, bird numbers and daily movement patterns. A significant database exists—a compilation of historical information on movement patterns from many areas of the world.
In the early 1980s, a bird-avoidance model (BAM) was conceived by the U.S. Air Force to warn flight crews of bird activity, and to take advantage of existing birdmovement detection capabilities and data. By compiling historical data on hazardous bird populations and their movements, BAM gives pilots and mission planners the information needed to consider evasive action.
Through BAM, bird density is overlaid on a standard map. Each square km of the 48 contiguous U.S. states is assigned a unique bird-strike risk value (BAM development is currently underway for Alaska and Western Europe). BAM provides data on 60 species of birds most hazardous to aircraft flying at low levels. (These species include Turkey Vultures and Red-tailed Hawks—birds that account for 27 percent of identified strikes and 53 percent of the risk (probability of damage) to low-level missions.) To simplify the system, these 60 species are grouped into 16 composite types according to behaviour. BAM is accessed through a menu-driven, Web-based PC program, allowing users to obtain bird-hazard information according to geographic locations, time of year, time of day, and selected routes. By comparing the relative risk of different flight plans, users are able to select the safest times and locations in which to fly.
BAM has proven to be an extremely useful tool in forecasting bird positions based on past knowledge of their locations. Flight planners and pilots in all aviation sectors can use this information for planning in advance of 24 hours.
Together, BAM and the Avian Hazard Advisory System (AHAS) support long and short-term flight planning by focusing on bird movements and behaviours. In fact, AHAS was developed to extend the capacity of BAM and provide more immediate, near real-time information on bird concentrations and behaviours. AHAS is designed to link:
- BAM’s historical data on bird activity;
- weather conditions in relation to bird activity; and
- strike rates for specific bird species.
To meet the need for information on real-time bird concentrations and behaviours, the Avian Hazard Advisory System (AHAS) was developed, extending the capacity of BAM. AHAS is designed to link:
In addition, AHAS now incorporates data on bird activity gathered by nextgeneration weather radar (NEXRAD), making it possible to provide bird-strike risklevel information that’s updated every 20 to 35 minutes. AHAS now operates over the contiguous 48 states of the U.S.
Applying bird-avoidance modeling techniques: two examples
Example 1
Integrating bird migratory data in the planning of flight routes and schedules has led to a dramatic reduction in the number of fatal and costly bird strikes experienced by the Israeli Air Force.
Israel is at the migratory crossroads of Europe, Asia, and Africa; large numbers of birds pass through the region twice a year to avoid the Mediterranean Sea. Particularly significant are the hundreds of thousands of hawks, eagles, storks, pelicans, and cranes that move through the area—large to extremely large birds that pose serious threats to aircraft.
Intensive studies have been carried out using radar, radio telemetry, gliders, and the coordinated observations of large numbers of ground personnel, all examining the movements of these birds through Israel. Observations have shown that movements occur:
- during well-defined weather conditions,
- at predictable times of the year, and
- along routes that are similar from year to year.
The effects of daily variations such as local crosswinds are monitored in real-time with radar, supplementing the predictive models and providing very accurate and current information.
Example 2
Studies of soaring pelicans have recently been conducted at Naval Air Station (NAS) Fallon, near Reno, Nevada. Satellite telemetry transmitters were attached to ten American White Pelicans. The transmitters enabled monitoring of the geographic location and altitude of each bird as it flew between a nesting colony and a distant feeding area. Additional climatological data was also gathered. This information is being analyzed to determine whether there are predictive relationships between flight paths and altitudes used by the pelicans and local climatological conditions— especially boundary layers within the airspace used by pelicans.
A work in progress, this technique shows promise in accurately predicting daily flight behaviour of White Pelicans in the area. The timing and routing of pilot-training flights can be scheduled to reduce the risk of strikes involving these birds.
The future of bird-warning systems
There is potential to enhance the BAM concept in the future, perhaps leading to a national or even global database of bird movements and bird strikes.
Bird-warning systems in Europe and the U.S. have worked well in military aviation, where the ability to forecast bird migrations provides a fit with the flight planning flexibility available in most peacetime military missions. For the same reason, however, the value of bird movement data in commercial aviation may be limited.
Commercial aviation is relatively inflexible—bound to schedules, flight routes and altitudes that are dictated by factors other than bird movements. And yet there is value to any new risk-management tool, including those that predict bird movements. If airline operators and pilots can enhance their knowledge of the presence of birds— and associated risk—they can make informed decisions to accept or reject the risk; when risk is too high, flights can be delayed and rerouted.
Conclusion: research directions
While technological advances have the potential to reduce the level of damage to aircraft from wildlife strikes, economic and operational realities may render impractical the goal of protecting aircraft and engines from all bird and mammal destruction.
Meanwhile, wildlife-management tools and methods may be derived from ongoing research that focuses on two aspects of wildlife behaviour—wildlife response to stimuli and wildlife-prediction modeling.
Still more research is required to develop new and effective wildlife-management methods. As discussed in this book, the annual economic losses from wildlife strikes are significant. The possibility of a catastrophic accident is clearly evident in strike data and risk analysis. There must be renewed urgency on the part of national authorities, airport operators and the aviation industry to continue efforts to reduce the probability and severity of wildlife strikes to aircraft.