A bird strike—sometimes called birdstrike, bird ingestion (for an engine), bird hit, or bird aircraft strike hazard (BASH)—is a collision between an airborne animal (usually a bird or bat) and a manmade vehicle, usually an aircraft. The term is also used for bird deaths resulting from collisions with structures such as power lines, towers and wind turbines (see Bird–skyscraper collisions and Towerkill).
Particularly, the Canada goose has been ranked as the third most hazardous wildlife species to aircraft with approximately 240 goose-aircraft collisions in the United States each year. 80% of all bird strikes go unreported.
Most accidents occur when a bird (or birds) collides with the windscreen or is sucked into the engine of jet aircraft. These cause annual damages that have been estimated at $400 million within the United States alone and up to $1.2 billion to commercial aircraft worldwide. In addition to property damage, collisions between man-made structures and conveyances and birds is a contributing factor, among many others, to the worldwide decline of many avian species. The International Civil Aviation Organization (ICAO) received 65,139 bird strike reports for 2011–14, and the Federal Aviation Authority counted 177,269 wildlife strike reports on civil aircraft between 1990 and 2015, growing 38% in seven years from 2009 to 2015. Birds accounted for 97%.
Event description
Bird strikes happen most often during takeoff or landing or low altitude flight. However, bird strikes have also been reported at high altitudes, some as high as 6,000 to 9,000 m (20,000 to 30,000 ft) above the ground. Bar-headed geese have been seen flying as high as 10,175 m (33,383 ft) above sea level. An aircraft over the Ivory Coast collided with a Rüppell's vulture at the altitude of 11,300 m (37,100 ft), the current record avian height. The majority of bird collisions occur near or at airports (90%, according to the ICAO) during takeoff, landing and associated phases.
According to the FAA wildlife hazard management manual for 2005, less than 8% of strikes occur above 900 m (3,000 ft) and 61% occur at less than 30 m (98 ft).
The point of impact is usually nose or engine inlet.
The force of the impact on an aircraft depends on the weight of the animal and the speed difference and direction at the point of impact. The energy of the impact increases with the square of the speed difference. High-speed impacts, as with jet aircraft, can cause considerable damage and even catastrophic failure to the vehicle. The energy of a 5 kg (11 lb) bird moving at a relative velocity of 275 km/h (171 mph) approximately equals the energy of a 100 kg (220 lb) weight dropped from a height of 15 metres (49 ft). However, according to the FAA, only 15% of strikes (ICAO 11%) result in damage to the aircraft. Bird strikes can damage vehicle components, or injure passengers. Flocks of birds are especially dangerous and can lead to multiple strikes, with corresponding damage. Depending on the damage, aircraft at low altitudes or during take-off and landing often cannot recover in time. US Airways Flight 1549 is a classic example of this. The engines on the Airbus A320 used on that flight were torn apart by multiple bird strikes at low altitude. There was no time to make a safe landing at an airport, forcing a water landing in the Hudson River.
Remains of the bird, termed snarge, are sent to identification centres where forensic techniques may be used to identify the species involved. These samples need to be taken carefully by trained personnel to ensure proper analysis and reduce the risks of infection (zoonoses).
Species
Most bird strikes involve large birds with big populations, particularly geese and gulls in the United States. In parts of the US, Canada geese and migratory snow geese populations have risen significantly while feral Canada geese and greylag geese have increased in parts of Europe, increasing the risk of these and Milvus kites are often involved. In the US, reported strikes are mainly from waterfowl (30%), gulls (22%), raptors (20%), and pigeons and doves (7%). The Smithsonian Institution's Feather Identification Laboratory has identified turkey vultures as the most damaging birds, followed by Canada geese and white pelicans, all of which are very large birds. In terms of frequency, the laboratory most commonly finds mourning doves and horned larks involved in the strike large birds to aircraft. In other parts of the world, large birds of prey such as Gyps vultures.
Large land animals, such as deer, can also be a problem to aircraft during takeoff and landing. Between 1990 and 2013, civil aircraft experienced more than 1,000 collisions with deer and 440 with coyotes.
Countermeasures
There are three approaches to reduce the effect of bird strikes. The vehicles can be designed to be more bird resistant, the birds can be moved out of the way of the vehicle, or the vehicle can be moved out of the way of the birds.
1. Vehicle design
Most large commercial jet engines include design features that ensure they can shut-down after "ingesting" a bird weighing up to 1.8 kg (4.0 lb). The engine does not have to survive the ingestion, just be safely shut down. This is a 'stand-alone' requirement, i.e., the engine, not the aircraft, must pass the test. Multiple strikes (from hitting a bird flock) on twin-engine jet aircraft are very serious events because they can disable multiple aircraft systems, requiring emergency action to land the aircraft, as on January 15, 2009, forced ditching of US Airways Flight 1549.
Modern jet aircraft structures must be able to withstand one 1.8 kg (4.0 lb) collision; the empennage (tail) must withstand one 3.6 kg (7.9 lb) bird collision. Cockpit windows on jet aircraft must be able to withstand one 1.8 kg (4.0 lb) bird collision without yielding or spalling.
At first, bird strike testing by manufacturers involved firing a bird carcass from a gas cannon and sabot system into the tested unit. The carcass was soon replaced with suitable density blocks, often gelatin, to ease testing. Current testing is mainly conducted with computer simulation, although final testing usually involves some physical experiments (see birdstrike simulator).
Based on US NTSB recommendation following the 2009 US Airways Flight 1549, the EASA in 2017, followed a year after by the FAA, proposing that engines should sustain a bird strike not only on takeoff where turbofans are turning at their fastest but also in climb and descent when they turn more slowly; new regulations could apply for the Boeing NMA engines.
2. Wildlife management
Though there are many methods available to wildlife managers at airports, no single method will work in all instances and with all species. Wildlife management in the airport environment can be grouped into two broad categories: non-lethal and lethal. Integration of multiple non-lethal methods with lethal methods results in the most effective airfield wildlife management strategy.
3. Non-lethal
Non-lethal management can be further broken down into habitat manipulation, exclusion, visual, auditory, tactile, or chemical repellents, and relocation.
One of the primary reasons that wildlife is seen in airports is an abundance of food. Food resources on airports can be either removed or made less desirable. One of the most abundant food resources found in airports is turfgrass. This grass is planted to reduce runoff, control erosion, absorb jet wash, allow passage of emergency vehicles, and to be aesthetically pleasing (DeVault et al. 2013) However, turfgrass is a preferred food source for species of birds that pose a serious risk to aircraft, chiefly the Canada goose (Branta canadensis). Turfgrass planted at airports should be a species that geese do not prefer (e.g. St. Augustine grass) and should be managed in such a way that reduces its attractiveness to other wildlife such as small rodents and raptors (Commander, Naval Installations Command 2010,[26] DeVault et al. 2013). It has been recommended that turfgrass be maintained at a height of 7–14 inches through regular mowing and fertilization (U.S. Air Force 2004).
5. Exclusion
Though excluding birds from the entire airport environment are virtually impossible, it is possible to exclude deer and other mammals that constitute a small percentage of wildlife strikes. Three-meter high fences made of chain link or woven wire, with barbed wire outriggers, are the most effective. When used as a perimeter fence, these fences also serve to keep unauthorized people off of the airport (Seamans 2001). Realistically every fence must have gates. Gates that are left open allow deer and other mammals onto the airport. 4.6 meter long cattle guards are effective at deterring deer up to 98% of the time (Belant et al. 1998).
6. Visual repellents
There have been a variety of visual repellent and harassment techniques used in airport wildlife management. They include using birds of prey and dogs, effigies, landing lights, and lasers. Birds of prey have been used with great effectiveness at landfills where there were large populatioEffigies of both predators and conspecifics have been used with success to disperse gulls and vultures.
Lasers have been used with success to disperse several species of birds. However, lasers are species-specific as certain species will only react to certain wavelengths. Lasers become more effective as ambient light levels decrease, thereby limiting effectiveness during daylight hours. Some species show a very short time to habituation (Airport Cooperative Research Program, 2011). The risks of lasers to aircrews must be evaluated when determining whether or not to deploy lasers on the target of feeding gulls (Cook et al. 2008). Dogs have also been used with success as visual deterrents and means of harassment for birds at airfields (DeVault et al. 2013). However, airport wildlife managers must consider the risk of knowingly releasing animals in the airport environment. Both birds of prey and dogs must be monitored by a handler when deployed and must be cared for, when not deployed. Airport wildlife managers must consider the economics of these methods (Seamans 2001)
Southampton Airport utilizes a laser device which disables the laser past a certain elevation, eliminating the risk of the beam being shone directly at aircraft and air traffic control tower (Southampton Airport 2014).
7. Auditory repellents
Auditory repellents are commonly used in both agricultural and aviation contexts. Devices such as propane exploders (cannons), pyrotechnics, and bioacoustics are frequently deployed on airports. Propane exploders are capable of creating noises of approximately 130 decibels (Wildlife Control Supplies). They can be programmed to fire at designated intervals, can be remote-controlled, or motion-activated. Due to their stationary and often predictable nature, wildlife quickly becomes habituated to propane cannons. Lethal control may be used to extend the effectiveness of propane exploders (Washburn et al. 2006).
8. Tactile repellents
Sharpened spikes to deter perching and loafing are commonly used. Generally, large birds require different applications than small birds do (DeVault et al. 2013)
9. Chemical repellents
There are only two chemical bird repellents registered for use in the United States. They are methyl anthranilate and anthraquinone. Methyl anthranilate is a primary repellent that produces an immediate unpleasant sensation that is reflexive and does not have to be learned. As such it is most effective for transient populations of birds (DeVault et al. 2013). Methyl anthranilate has been used with great success at rapidly dispersing birds from flight lines at Homestead Air Reserve Station (Engeman et al. 2002). Anthraquinone is a secondary repellent that has a laxative effect that is not instantaneous. Because of this, it is most effective on resident populations of wildlife that will have time to learn an aversive response (Izhaki 2002, DeVault et al. 2013).
10. Relocation
Relocation of raptors from airports is often considered preferable to lethal control methods by both biologists and the public. Complex legal issues are surrounding the capture and relocation of species protected by the Migratory Bird Treaty Act of 1918 and the Bald and Golden Eagle Protection Act of 1940. Before capture, proper permits must be obtained and the high mortality rates, as well as the risk of disease transmission associated with relocation, must be weighed. Between 2008 and 2010, U.S. Department of Agriculture Wildlife Services personnel relocated 606 red-tailed hawks from airports in the United States after the failure of multiple harassment attempts. The return rate of these hawks was 6%; however, the relocation mortality rate for these hawks was never determined (DeVault et al. 2013).
11. Lethal
Lethal wildlife control on airports falls into two categories: reinforcement of other non-lethal methods and population control.
12. Reinforcement
The premise of effigies, pyrotechnics, and propane exploders is that there be a perceived immediate danger to the species to be dispersed. Initially, the sight of an unnaturally positioned effigy or the sound of pyrotechnics or exploders is enough to elicit a danger response from wildlife. As wildlife become habituated to non-lethal methods the culling of small numbers of wildlife in the presence of conspecifics can restore the danger response (Baxter and Allan 2008, Cook et al. 2008, Commander, Naval Installations Command 2010, DeVault et al. 2013).
13. Population control
Under certain circumstances, lethal wildlife control is needed to control the population of a species. This control can be localized or regional. Localized population control is often used to control species that are residents of the airfield such as deer that have bypassed the perimeter fence. In this instance, sharpshooting would be highly effective, such as is seen at Chicago O'Hare International Airport (DeVault et al. 2013).
Regional population control has been used on species that cannot be excluded from the airport environment. A nesting colony of laughing gulls at Jamaica Bay Wildlife Refuge contributed to 98–315 bird strikes per year, in 1979–1992, at adjacent John F. Kennedy International Airport (JFK). Though JFK had an active bird management program that precluded birds from feeding and loafing on the airport, it did not stop them from overflying the airport to other feeding sites. U.S. Department of Agriculture Wildlife Services personnel began shooting all gulls that flew over the airport, hypothesizing that eventually, the gulls would alter their flight patterns. They shot 28,352 gulls in two years (approximately half of the population at Jamaica Bay and 5–6% of the nationwide population per year). Strikes with laughing gulls decreased by 89% by 1992. However, this was more a function of the population reduction than the gulls altering their flight pattern (Dolbeer et al. 1993, Dolbeer et al. 2003, DeVault et al. 2013).
14. Flightpath
Pilots should not take off or land in the presence of wildlife and should avoid migratory routes, wildlife reserves, estuaries and other sites where birds may congregate. When operating in the presence of bird flocks, pilots should seek to climb above 3,000 feet (910 m) as rapidly as possible as most bird strikes occur below 3,000 feet (910 m). Additionally, pilots should slow down their aircraft when confronted with birds. The energy that must be dissipated in the collision is approximately the relative kinetic energy ({\displaystyle E_{k}}E_{k}) of the bird, defined by the equation {\displaystyle E_{k}={\frac {1}{2}}mv^{2}}E_{k} = \frac{1}{2} m v^{2} where {\displaystyle m}m is the mass of the bird and {\displaystyle v}v is the relative velocity (the difference of the velocities of the bird and the plane, resulting in a lower absolute value if they are flying in the same direction and higher absolute value if they are flying in opposite directions). Therefore, the speed of the aircraft is much more important than the size of the bird when it comes to reducing energy transfer in a collision. The same can be said for jet engines: the slower the rotation of the engine, the less energy which will be imparted onto the engine at collision.
RECENT REPORTED BIRD HITS:-
Russian Plane Hits Birds Minute After Takeoff, Hero Pilot Pulls A 'Sully'.
US Stealth Fighter Suffers Millions In Damage From Bird Strike.
GoAir Pilots Shut Down the Wrong Engine, Restarted It After Bird-Hit.
GoAir Flight Suffers Bird Hit; Returns To Delhi Airport.
Doha-Bound Indigo Flight Suffers Bird Hit, Returns To Chennai.
AirAsia Jet Returns To Australia After Suspected Bird Strike.
