John Sheridan

Wilbur Wright was the first pilot to record a bird strike (in 1905), and the first fatal crash attributable to a bird strike came seven years later. But to most members of the non-flying public, the first time aircraft bird strikes became newsworthy was probably in 2009, when a flock of Canada geese sent <a href="http://www.ainonline.com/aviation-news/2009-01-15/us-airways-a320-ditches-hudson-river">Chesley Sullenberger’s A320 into the Hudson River</a>. In the earlier days of aviation, however, runway foreign object debris (FOD) “strikes” were the prime sources of aircraft damage, from fallen parts, mechanics’ tools, pieces of broken runway surface and other items, with bird-strike damage relatively infrequent. But following WWII, and the introduction of growing numbers of faster and larger aircraft, bird strikes became more noticed. While improved runway surveillance methods–first daily “FOD walks,” then by more frequent vehicle inspections and runway sweepers and, more recently, with the development of automatic alerting radar and video sensors–have kept the inanimate FOD threat down to around four incidents per 10,000 movements, the number of bird strikes has been increasing slowly. Once statistically insignificant, they now account for more than two strikes per 10,000 movements, and are gradually becoming even more frequent.


Leading the effort to keep bird-strike numbers from increasing further is the FAA-designated Center of Excellence in Airport Technology (CEAT) at the University of Illinois at Urbana-Champaign. Within CEAT is the Airport Safety Management Program, coordinated by Professor Emeritus Edwin Herricks, regarded as one of the leading world authorities on FOD and bird, or avian, radar. Herricks earlier evaluated four automatic runway FOD detection systems of different designs, leading to an FAA definitive Advisory Circular (AC) on the subject.


“Avian radar,” noted Herricks, who also provided technical support for an FAA avian radar AC, “is a promising complement to FOD detection equipment, but unfortunately it does not complete the airport threat picture. Conventional FOD on runways is always manageable, but birds, either on the ground or airborne, never can be. I call them the ultimate uncooperative targets.”


So which is worse: striking something solid on the runway or striking a bird? Intuitively, one chooses hitting the bird, an apparently “softer” target. But it turns out that the opposite is closer to the truth. A comprehensive 2010 civil aircraft study showed that while the direct cost of an average inanimate runway FOD incident in 2010 averaged $10,366; the direct cost of an average bird strike was $22,741. Direct cost is the actual cost of repairs, labor and replacement parts, while indirect costs such as loss of service, delays, diversions, replacement aircraft, unplanned hangarage and related effects averaged 10 times more than the direct costs, with the study reporting that United Airlines estimated an 11-times factor for bird strikes. Worldwide, the aviation industry’s annual direct and indirect costs of FOD and bird strikes are now estimated to be well over $13 billion. Yet the true figure for bird strikes is probably higher since, as Steve Osmek, Seattle Sea-Tac’s managing wildlife biologist, told AIN, the U.S. is one of the few nations that does not require compulsory bird-strike reports.


Estimates of species numbers from the government/industry Bird Strike Committee USA indicate the number of birds is on the rise. Starlings–sometimes dubbed “feathered bullets” by ornithologists due to their high body density–arrived in New York’s Central Park in 1890 as 60 individuals brought by emigrants to remind them of home. Some emigrants: there are now estimated to be more than 150 million starlings across North America. Canada geese have also moved south to warmer climes, with approximately 3.5 million non-migrating U.S. residents last year, compared with less than a million in 1990. The greater snow goose also found the U.S. more hospitable, expanding from around 90,000 in 1970 to more than a million last year. Native species have also flourished, with bald eagles flourishing from 400 pairs in 1970 to more than 14,000 pairs today. Over the same period, cormorants around the Great Lakes have increased a thousand-fold, from around 200 to more than 200,000. And, as luck (or bad luck) would have it, white pelicans–weighing 30 pounds or more–are up six-fold in the U.S. since 1970.


System Improvements Needed


So where is avian radar technology today? Herricks points out that while avian radar can readily acquire bird targets, there is no current system that will direct birds away from their chosen flight paths, and attempting to avoid them, particularly near the ground where more than 40 percent of strikes occur, can be hazardous. Similarly, controllers never attempt to give pilots avoidance commands, due to birds’ unpredictable flight paths, although ATIS and controller alerting messages of large flocks, or migrating streams of large birds, are clearly valuable.


Two useful things to know: First, when birds resting on the runway see or hear aircraft approaching them on takeoff, their escape maneuver usually first launches them a few feet vertically, which inevitably lines them up with engine intakes. Second, bird-strike numbers drop off dramatically above 3,000 feet. Sullenberger and all aboard his A320 were just plain unlucky.


With that said, several innovative designs are in use today or are in development, with the aim of bringing some modicum of order to things. Several locations have introduced purpose-built radars aimed at tracking flocks, such as when birds leave and return to their nesting sites at dawn and dusk, or when they concentrate on or near runways and aircraft approach and departure paths. As well, airport wildlife staff regularly patrol these high-activity areas to disperse them. Radar also has value during the north/south migration seasons, and the concept of tying the nationwide Nexrad network into local radars has been investigated, although Nexrad is rather coarse grained.


Yet airports aren’t the only concerns. Accipiter Radar Technologies of Niagara, Ontario, which supports avian radar research systems at SEA and ORD, has established a 1950s Cold War-like distant early warning net around the tailing ponds of Alberta’s oil sands, where approaching flocks of birds are initially detected and tracked by radar and, as they get closer, the radar tracking controls trigger specific arrays of loudspeakers and other harassment devices to divert the birds from the ponds. At Seattle’s Sea-Tac, Accipiter also has a joint program with the airport’s wildlife staff to measure bird movements by sector to assess threats rapidly, particularly in the approach areas, that is showing promising results.


In the Netherlands, Robin Radar of Amsterdam has developed three-dimensional radar that uses the Doppler effect to measure the wing beats of different species, which correlate with bird size. At Dallas/Ft. Worth, SRC of Syracuse, N.Y., has two avian radar adaptations of its military projectile tracking systems under evaluation, while Japan’s Haneda International Airport has installed the first comprehensive avian radar network covering the whole airport complex. Yet certainly the world’s most specialized avian radar installation is the De-Tect system at King Shaka International Airport in Durban, South Africa. There, and within less than an hour at dawn and dusk each day of summer, up to three million barn swallows leave and later return to their nesting area in a nearby protected wetland, less than a mile from the runway end. All flying is banned during those periods of heavy avian traffic.


In addition to the dedicated avian radar manufacturers, companies that had previously developed camera-based runway FOD detection systems are finding multiple approaches to detecting and assessing birds on runways. In Israel, Xsight Systems of Tel Aviv is testing algorithms to identify bird species on the airport surface under all visibility conditions by their stored digitized visual characteristics–analogous to but different from face-recognition security technology–as part of expanding the capabilities of its automatic runway FOD detection systems. Stratech Systems of Singapore is also understood to be further developing the bird-tracking capabilities of its runway FOD detection system.


For Herricks, therefore, the bottom line for airport safety is that while avian radar does some things really well, such as helping us better understand bird movement dynamics, it is far from completely solving the bird-strike problem. As he puts it, “Radar is simply a tool in the toolbox of the competent airport operator, and as other applications, such as FOD detection, find their way to airports, many opportunities for multiple uses will develop.”


It may be that until avian radar technology advances further, perhaps the most practical advice for pilots still appears to be “get above 3,000 feet as soon as you can.”

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