A bird strike—sometimes called birdstrike, avian ingestion (only if in an engine), bird hit, or BASH (for Bird Aircraft Strike Hazard)—is a collision between an airborne animal (usually a bird or bat) and a human-made vehicle, especially aircraft. The term is also used for bird deaths resulting from collisions with human-made structures such as power lines, towers and wind turbines (see Bird-skyscraper collisions and Towerkill). A bug strike is an impairment of an aircraft or aviator by an airborne insect.
Bird strikes are a significant threat to flight safety, and have caused a number of accidents with human casualties. The number of major accidents involving civil aircraft is quite low and it has been estimated that there is only about 1 accident resulting in human death in one billion (109) flying hours. The majority of bird strikes (65%) cause little damage to the aircraft; needless to say, the collision is usually fatal to the bird.
Most accidents occur when the bird hits the windscreen or flies into the engines. These cause annual damages that have been estimated at $400 million within the United States of America alone and up to $1.2 billion to commercial aircraft worldwide.
Event description 
Bird strikes happen most often during takeoff or landing, or during low altitude flight. However, bird strikes have also been reported at high altitudes, some as high as 6,000 m (20,000 ft) to 9,000 m (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 Côte d'Ivoire collided with a Rüppell's Vulture at the astonishing altitude of 11,300 m (37,100 ft), the current record avian height. The majority of bird collisions occur near or on 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 (100 ft).
The point of impact is usually any forward-facing edge of the vehicle such as a wing leading edge, nose cone, jet engine cowling or engine inlet.
Jet engine ingestion is extremely serious due to the rotation speed of the engine fan and engine design. As the bird strikes a fan blade, that blade can be displaced into another blade and so forth, causing a cascading failure. Jet engines are particularly vulnerable during the takeoff phase when the engine is turning at a very high speed and the plane is at a low altitude where birds are more commonly found.
The force of the impact on an aircraft depends on the weight of the animal and the speed difference and direction at the impact. The energy of the impact increases with the square of the speed difference. Hence a low-speed impact of a small bird on a car windshield causes relatively little damage. 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%) actually 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, and damage. Depending on the damage, aircraft at low altitudes or during take off and landing often cannot recover in time, and thus crash, as in the case of US Airways Flight 1549.
Remains of the bird, termed snarge, are sent to identification centers 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 zoonoses.
Sacramento International Airport has had more bird strikes (1,300 collisions between birds and jets between 1990 and 2007, causing an estimated $1.6 million in damage) than any other California airport. Sacramento International Airport has the most bird strikes of any airport in the west and sixth among airports in the US, according to the FAA, as it is located along the Pacific Flyway, a major bird migration path.
The animals most frequently involved in bird strikes are 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 large birds to aircraft. In other parts of the world, large birds of prey such as Gyps vultures and Milvus kites are often involved. In the US reported strikes are divided between waterfowl (32%), gulls (28%), and raptors (17%) (Data from the BSC USA). The Smithsonian Institution's Feather Identification Laboratory has identified turkey vultures as the most damaging birds, followed by Canada geese and white pelicans, all very large birds. In terms of frequency, the laboratory most commonly finds Mourning Doves and Horned Larks involved in the strike.
The largest numbers of strikes happen during the spring and fall migrations. Bird strikes above 500 feet (150 m) altitude are about 7 times more common at night than during the day during the bird migration season.
Large land-bound animals, such as deer, can also be a problem to aircraft during take off and landing, and over 650 civil aircraft collisions with deer were reported in the U.S. between 1990 and 2004.
An animal hazard reported from London Stansted Airport in England is rabbits: they get run over by ground vehicles and planes, and they pass large amounts of droppings, which attract mice, which attract owls, which become another birdstrike hazard.
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.
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 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 in the January 15, 2009, forced ditching of US Airways Flight 1549.
Modern jet aircraft structures must be able to withstand one 1.8 kg (4 lb) collision; the empennage (tail) must withstand one 3.6 kg (8 lb) bird collision. Cockpit windows on jet aircraft must be able to withstand one 1.8 kg (4 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. Currently testing is mainly conducted with computer simulation, although final testing usually involves some physical experiments (see birdstrike simulator).
Bird management 
To reduce birdstrikes on takeoff and landing, airports engage in bird management and control. There is no single solution that works for all situations. Birds have been noted for their adaptability and control methods may not remain effective for long. Management techniques include changes to habitat around the airport to reduce its attractiveness to birds. Vegetation which produces seeds, grasses which are favored by geese, and human-made food, a favorite of gulls, all should be removed from the airport area. Trees and tall structures which serve as roosts at night for flocking birds or perches should be removed or modified to discourage bird use.
Other approaches try to scare away the birds using frightening devices, for example sounds, lights, pyrotechnics, radio-controlled airplanes, decoy animals/corpses, lasers, dogs etc. Firearms are also occasionally employed. A successful approach has been using dogs, particularly Border collies, to scare away birds and wildlife. Another alternative is bird capture and relocation. Trained falcons are sometimes used to harass the bird population, as for example on John F. Kennedy International Airport. At Manchester Airport in England the usual type of falcon used for this is a peregrine falcon/lanner falcon hybrid, as its flight range covers the airport without straying too far. An airport in New Zealand uses electrified mats to reduce the number of worms that attracted large numbers of sea gulls.
Flight path 
Pilots have very little training in wildlife avoidance nor is training required by any regulatory agency. However, they should not takeoff or land in the presence of wildlife, 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 birdstrikes occur below 3,000 feet (910 m). Additionally pilots should slow their aircraft when confronted with birds. The energy that must be dissipated in the collision is approximately the relative kinetic energy () of the bird, defined by the equation where is the mass and is the relative velocity (the difference of the velocities of the bird and the plane if they are flying in the same direction and the sum if they are flying towards each other). 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.
The body density of the bird is also a parameter that influences the amount of damage caused.
The US Military Aviation Hazard Advisory System uses a Bird Avoidance Model based on data from the Smithsonian Institution, historical patterns of bird strikes and radar tracking of bird activity. This model has been extremely successful. Prior to flight USAF pilots check for bird activity on their proposed low level route or bombing range. If bird activity is forecast to be high, the route is changed to one of lower threat. In the first year this BAM model was required as a preflight tool, the USAF Air Combat Command experienced a 70% drop in birdstrikes to its mission aircraft.
TNO, a Dutch R&D Institute, has developed the successful ROBIN (Radar Observation of Bird Intensity) for the Royal Netherlands Airforce. ROBIN is a near real-time monitoring system for flight movements of birds. ROBIN identifies flocks of birds within the signals of large radar systems. This information is used to give Air Force pilots warning during landing and take-off. Years of observation of bird migration with ROBIN have also provided a better insight into bird migration behaviour, which has had an influence on averting collisions with birds, and therefore on flight safety. Since the implementation of the ROBIN system at the Royal Netherlands Airforce the number of collisions between birds and aircraft in the vicinity of military airbases has decreased by more than 50%.
There are no civil aviation counterparts to the above military strategies. Some experimentation with small portable radar units has taken place at some airports. However, no standard has been adopted for radar warning nor has any governmental policy regarding warnings been implemented.
The Federal Aviation Administration (FAA) estimates the problem costs US aviation 400 million dollars annually and has resulted in over 200 worldwide deaths since 1988. In the United Kingdom, the Central Science Laboratory estimates that, worldwide, the cost of birdstrikes to airlines is around US$1.2 billion annually. This cost includes direct repair cost and lost revenue opportunities while the damaged aircraft is out of service. Estimating that 80% of bird strikes are unreported, there were 4,300 bird strikes listed by the United States Air Force and 5,900 by US civil aircraft in 2003.
The first reported bird strike was by Orville Wright in 1905; according to the Wright Brothers' diaries Orville … flew 4,751 meters in 4 minutes 45 seconds, four complete circles. Twice passed over fence into Beard's cornfield. Chased flock of birds for two rounds and killed one which fell on top of the upper surface and after a time fell off when swinging a sharp curve.
In 1911 French pilot Eugene Gilbert encountered an angry mother eagle over the Pyrenees Mountains en route from Paris to Madrid during the great aviation race held that year between those two cities. Gilbert, flying an open-cockpit Bleriot XI, was able to ward off the large bird by firing pistol shots at it but not killing it.
The first recorded bird strike fatality was reported in 1912 when aero-pioneer Cal Rodgers collided with a gull which became jammed in his aircraft control cables. He crashed at Long Beach, California, was pinned under the wreckage and drowned.
The greatest loss of life directly linked to a bird strike was on October 4, 1960, when Eastern Air Lines Flight 375, a Lockheed L-188 Electra flying from Boston, flew through a flock of common starlings during take off, damaging all four engines. The aircraft crashed into Boston harbor shortly after take-off, with 62 fatalities out of 72 passengers. Subsequently, minimum bird ingestion standards for jet engines were developed by the FAA.
NASA astronaut Theodore Freeman was killed when a goose shattered the plexiglass cockpit canopy of his Northrop T-38 Talon, resulting in shards being ingested by the engines, leading to a fatal crash.
In 1995, a Dassault Falcon 20 crashed at a Paris airport during an emergency landing attempt after sucking lapwings into an engine, which caused an engine failure and a fire in the airplane's fuselage; all 10 people on board were killed.
On September 22, 1995, a U.S. Air Force Boeing E-3 Sentry AWACS aircraft (Callsign Yukla 27, serial number 77-0354), crashed shortly after take off from Elmendorf AFB. The aircraft lost power in both port side engines after these engines ingested several Canada Geese during takeoff. It crashed about two miles (3 km) from the runway, killing all 24 crew members on board.
On November 28, 2004, the nose landing gear of KLM Flight 1673, a Boeing 737-400, struck a bird during takeoff at Amsterdam Airport Schiphol. The incident was reported to air traffic control, the landing gear was raised normally and the flight continued normally to its destination. Upon touching down at Barcelona International Airport, the aircraft started deviating to the left of the runway centreline. The crew applied right rudder, braking and the nose wheel steering tiller but could not keep the aircraft on the runway. After it veered off the paved surface of the runway at about 100 knots, the jet went through an area of soft sand. The nose landing gear leg collapsed and the left main landing gear leg detached from its fittings shortly before the aircraft came to a stop perched over the edge of a drainage canal. All 140 passengers and six crew evacuated safely, but the aircraft itself had to be written off. The cause was discovered to be a broken cable in the nose wheel steering system caused by the bird collision. Contributing to the snapped cable was the improper application of grease during routine maintenance which led to severe wear of the cable.
The Space Shuttle Discovery also hit a bird (a vulture) during the launch of STS-114 on July 26, 2005, although the collision occurred soon after lift-off and at low speed, with no obvious damage to the shuttle.
On November 10, 2008, Ryanair Flight 4102 from Frankfurt to Rome made an emergency landing at Ciampino Airport after multiple bird strikes caused both engines to fail. After touchdown, the left main landing gear collapsed, and the aircraft briefly veered off the runway. Passengers and crew were evacuated through the starboard emergency exits.
On January 4, 2009, a Sikorsky S-76 helicopter hit a Red-tailed Hawk in Louisiana. The hawk hit the helicopter just above the windscreen. The impact forced the activation of the engine fire suppression control handles, retarding the throttles and causing the engines to lose power. Eight of the nine persons on board died in the subsequent crash; the survivor, a passenger, was seriously injured.
On January 15, 2009, US Airways Flight 1549 from LaGuardia Airport to Charlotte/Douglas International Airport ditched into the Hudson River after experiencing a loss of both turbines. It is suspected that the engine failure was caused by running into a flock of geese at an altitude of about 975 m (3,200 feet), shortly after takeoff. All 150 passengers and 5 crew members were safely evacuated after a successful water landing. On May 28, 2010, the NTSB published its final report into the accident.
Bug strike 
Flying insect strikes, like bird strikes, have been encountered by pilots since aircraft were invented. Future United States Air Force general Henry H. Arnold nearly lost control of his Wright Model B in 1911 after a bug flew into his eye while he was not wearing goggles, distracting him.
In 1986 a Boeing B-52 Stratofortress on a low-level training mission entered a swarm of locusts. The insects' impacts on the aircraft's windscreens rendered the crew unable to see, forcing them to abort the mission and fly using the aircraft's instruments alone. The aircraft eventually landed safely. In 2010 the Australian Civil Aviation Safety Authority (CASA) issued a warning to pilots about the potential dangers of flying through a locust swarm. CASA warned that the insects could cause loss of engine power and loss of visibility; and blocking of an aircraft's pitot tubes, causing inaccurate airspeed readings.
See also 
- Gard, Katie ; Groszos, Mark S. ; Brevik, Eric C. ; Lee, Gregory W. (2007). "Spatial analysis of Bird-Aircraft Strike Hazard for Moody Air Force Base aircraft in the state of Georgia.(Report)" (PDF). Georgia Journal of Science 65 (4): 161–169.
- Manville, A.M., II. (2005). "Bird strikes and electrocutions at power lines, communication lowers, and wind turbines: state of the art and slate of the science — next steps toward mitigation.". In C.J. Ralph and T. D. Rich. Bird Conservation Implementation in the Americas: Proceedings 3rd International Partners in Flight Conference 2002. U.S.D.A. Forest Service. GTR-PSW-191, Albany. CA.
- Sodhi, Navjot S. (2002). "Competition in the air: birds versus aircraft.". The Auk 119 (3): 587–595. doi:10.1642/0004-8038(2002)119[0587:CITABV]2.0.CO;2.
- Thorpe, John (2003). "Fatalities and destroyed civil aircraft due to bird strikes, 1912-2002" (PDF). International Bird Strike Committee, IBSC 26 Warsaw.
- Milson, T.P. & N. Horton (1995). Birdstrike. An assessment of the hazard on UK civil aerodromes 1976-1990. Central Science Laboratory, Sand Hutton, York, UK.
- Allan, John R.; Alex P. Orosz (2001-08-27). "The costs of birdstrikes to commercial aviation". DigitalCommons@University of Nebraska. Retrieved 2009-01-16.
- Richardson, W. John (1994). "Serious birdstrike-related accidents to military aircraft of ten countries: preliminary analysis of circumstances" (PDF). Bird Strike Committee Europe BSCE 22/WP22, Vienna.
- Thomas Alerstam, David A. Christie, Astrid Ulfstrand. Bird Migration (1990). Page 276.
- Note however that the momentum (as distinct from the kinetic energy) of the bird in this example is considerably less than that of the tonne weight, and therefore the force required to deflect it is also considerably less.
- Dove, CJ, Marcy Heacker, Lee Weigt (2006). "DNA identification of birdstrike remains-progress report". Bird Strike Committee USA/CANADA, 8th Annual meeting, St. Louis.
- Laybourne, R. C. and C. Dove (1994). "Preparation of Bird Strike Remains for Identification." (PDF). Proc. Bird Strike Comm. Europe 22, Vienna 1994. pp. 531–543.
- Noam Leader, Ofer Mokady, Yoram Yom-Tov (2006). "Indirect Flight of an African Bat to Israel: An Example of the Potential for Zoonotic Pathogens to Move between Continents". Vector-Borne and Zoonotic Diseases 6 (4): 347–350. doi:10.1089/vbz.2006.6.347. PMID 17187568.
- SMF Tops California Airports For Bird Strikes 100 Bird Strikes Reported Annually In Sacramento, Experts Say January 15, 2009
- Sacramento airport seeks bird-kill law for air safety
- Allan, J. R. ; J. C. Bell;V. S. Jackson (1999). "An Assessment Of The World-wide Risk To Aircraft From Large flocking Birds". Bird Strike Committee Proceedings 1999 Bird Strike Committee-USA/Canada, Vancouver, BC.
- Wired Magazine: Bird Plus Plane Equals Snarge
- Dolbeer, RA. "Height Distribution of Birds Recorded by Collisions with Civil Aircraft". Journal of Wildlife Management: 1345–1350.
- Television program "Stansted: the Inside Story", 6 to 7 pm, Sunday 6 March 2011, Fiver (TV channel)
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- IBSC (2006). Recommended Practices No. 1: Standards For Aerodrome Bird/Wildlife Control. Issue 1 (PDF).
- Carter, Nicholas B., Dr. (April 2003). Border collies prove effective in controlling wildlife at airports 58 (3). ICAO. pp. 4–8. Retrieved 2009-01-16.
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- "Determination of body density for twelve bird species". Ibis 137 (3): 424–428. 1995. doi:10.1111/j.1474-919X.1995.tb08046.x.
- US Bird avoidance model
- John Ostrom, Chair, BSC-USA. "Bird Strike Committee USA statistics on birdstrikes". Retrieved 2009-12-13.
- The Pathfinders c.1980 by David Nevin for Time-Life books
- Howard, Fred (1998). Wilbur and Orville: A Biography of the Wright Brothers. Courier Dover. p. 375. ISBN 0-486-40297-5.
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- "CVR transcript Boeing E-3 USAF Yukla 27 - 22 SEP 1995". Accident investigation. Aviation Safety Network. 22 September 1995. Retrieved 2009-01-16.
- Accident description at the Aviation Safety Network
- Young, Kelly (2006-04-28). "The Space Vulture Squadron". Retrieved 2009-01-17.
- Milmo, Dan (10 November 2008). "Bird strike forces Ryanair jet into emergency landing in Italy". guardian.co.uk. Retrieved 2009-01-16.
- "Brief of accident; Sikorsky S-76C aircraft registration N748P". National Transportation Safety Board. 2010-11-24. Retrieved May 2, 2012.
- US Airways Plane Crashes Into Hudson River
- "CREW ACTIONS AND SAFETY EQUIPMENT CREDITED WITH SAVING LIVES IN US AIRWAYS 1549 HUDSON RIVER DITCHING, NTSB SAYS". NTSB. Retrieved 19 Aug 2010.
- Turek, Raymond (March 2002). "Low-level locusts: Think through the potential consequences of any plan". Combat Edge (The US Department of the Air Force). Retrieved May 2, 2012.
- Orreal, Jorja (September 27, 2010). "Aircraft warned to avoid flying in locust plague areas". The Courier Mail (Brisbane). Retrieved May 2, 2012.
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|Wikimedia Commons has media related to: Bird strike|
- A photo gallery of the bird strike conseguence between aircraft and birds
- International Bird Strike Committee
- Bird Strike Committee Canada
- BSC USA
- Aviation Hazard Advisory System
- Australian Aviation Wildlife Hazard Group
- The FlySafe Bird Avoidance Model (FlySafe-BAM)
- List of significant bird strikes