From Wikipedia, the free encyclopedia

Contents 1 Event description 2 Species 3 Countermeasures 3.1 Vehicle design 3.2 Bird management 3.3 Flight path 4 Incidents 5 Urban legend 6 In popular culture 7 See also 8 External links

A bird strike (sometimes birdstrike, bird hit, or BASH (bird aircraft strike hazard)) in aviation, is a collision between an airborne animal (most often a bird, but also sometimes another species) and a man made vehicle, especially aircraft. It is a common threat to aircraft safety and has caused a number of fatal accidents.

[edit] Event description

It is believed that most potential collisions are avoided because the bird is able to change its course in time. However, aircraft are especially at risk because their high speed give birds less time to react. Most bird strikes happen close to the ground, where the majority of birds are found (in bird airspace). Hence bird strikes happen most often during take off or landing, or during low altitude flight. However, bird strikes have also been reported at high altitudes, some as high as 20,000 to 30,000 feet above ground level. The majority of aircraft - bird collisions occur near or on airports (ICAO90%) during takeoff, landing and associated phases. According to the FAA wildlife hazard management manual for 2005, less than 8% of strikes occur above 3,000 feet and 61% occur at less than 30 m (100 feet).

The point of impact is usually any forward-facing edge of the vehicle, although with jet engine aircraft the animal is frequently sucked into the engine, causing damage to the fans or the housing, or airflow ducts. The force of the impact depends on the weight of the animal and the speed difference and direction at the impact. The weight of the vehicle can usually be ignored since it is usually much larger than the weight of the animal. The energy of the impact increases with the square of the speed difference. Hence the energy of the impact is small at low speeds, and an impact of a small bird on for example the windshield of an automobile has usually only minor or no damage to the car, although it will result in major injuries or death to the bird. High speeds, however, as for example with modern jet engine aircraft will produce considerable energy and may cause considerable damage or even a total catastrophic failure to the vehicle. However, according to the FAA only 15% of strikes (ICAO 11%) actually result in damage to the aircraft. The impact of a 5 kg (12 pound) bird at 240 km/h (150 mph) equals that of a 1/2 ton (1000 pound) weight dropped from a height of 3 meters (10 feet).

Depending on the force of the impact, the bird strike may damage or even destroy components of the vehicle, or injure people in the vehicle. Flocks of birds are especially dangerous, and can lead to multiple strikes, and damage, within a very brief period. Depending on the damage, aircraft at low altitudes or during take off and landing often cannot recover in time and crash.

In the USA, remains of the bird, usually a bloody goo called snarge, are sent to the Smithsonian Institution's Feather Identification Laboratory to determine the species. 1 One flying organization with a bigger than usual birdstrike risk is the Israeli Air Force, as Israel is on a major spring and autumn long-distance bird migration route.

[edit] Species

The animals most frequently involved in bird strikes are large birds with big populations, with geese and gulls causing most serious incidents. 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. Striking 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.

Strangely enough, vehicle-animal air collisions also sometimes include species that cannot fly. The Smithsonian Institution's Feather Identification Laboratory has identified frogs, turtles, and snakes as the animal in the "bird" strike. On one occasion they identified a cat at high altitude and on another a rabbit at a height of 550 metres (1800 feet).

The most likely explanation for this incongruity is that the animal identified had been either eaten or carried aloft by a bird of prey, though there are also meteorological explanations, such as raining animals.

[edit] Countermeasures

There are three basic 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.

[edit] Vehicle design

Most large commercial jet engines include design features that ensure they can safely shut-down after "ingesting" a bird weighing up to 1.8 kg (4 lb). Multiple or large strikes require emergency action to control damage. This limit is also applied to the rest of a modern commercial aircraft—it must be able to land safely after incurring a 1.8 kg strike.

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 for details.

[edit] Bird management

To reduce birdstrikes on takeoff and landing, airports invest in bird management and control. This includes changes to terrain around the airport to reduce its attractiveness as a habitat to birds. Things attractive to birds like landfill sites, water areas, and trees are removed to reduce the bird population around airports.

Other approaches try to scare away the birds using frightening devices, for example sounds, lights, pyrotechnics, radio-controlled airplanes, decoy animals/corpses, lasers, etc.

A tremendously successful approach in recent years has been the utilization of border collie dogs to scare away birds and wildlife.^{[citation needed]} Another alternative is bird capture and relocation.

Falcons are sometimes used to cut down the bird population, as for example on John F. Kennedy International Airport.^{[citation needed]} At Manchester Airport in England the usual type of falcon used for this is a peregrine falcon/lanner hybrid, as its habitual flight range is about the right size to cover the airport and not also much irrelevant land around.

An airport in New Zealand uses electrified mats to reduce the number of worms that attracted large numbers of sea gulls.^{[citation needed]}

[edit] Flight path

Pilots use awareness of bird habits and should avoid migratory routes [1], wildlife reserves, estuaries and other sites where birds may congregate. 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.

[edit] Incidents

The Federal Aviation Administration estimates the problem costs US aviation 600 million dollars annually and has resulted in 195 worldwide deaths since 1988. 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, and according to their 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.

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 controls. 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 plane crashed shortly after take-off into Boston harbor, with 62 fatalities. Subsequently, minimum bird ingestion standards for jet engines were developed by the FAA.

The Space Shuttle Discovery also hit a bird during take-off on July 26, 2005, although the collision occurred early during take off and at low speeds, with no obvious damage to the shuttle. It is not clear if the bird survived.

[edit] Urban legend

An urban legend story related to bird strikes is frequently found on the Internet. Birdstrike simulators are currently used by aircraft manufacturers and/or aviation authorities (such as the FAA, EASA or NASA) to test aircraft against birdstrikes, and usually work by firing a (dead) chicken at the aircraft. According to the stories, British Rail (or in other versions an institute known as the USPA) borrows this device to test the strength of the windshields on their high speed trains. On impact, the chicken shatters the windshield, breaks the operators chair, and comes to rest embedded in the engine. British Rail (or the USPA) asks the manufacturer for help, and receives a one-sentence reply: Thaw the chicken.

This urban legend was tested in two separate episodes of the television show MythBusters. On their first try (Season 1, Episode 9), the Mythbusters obtained a salvaged cockpit from a light aircraft, and several windshields. Upon testing, both the thawed and the frozen chickens caused nearly the same amount of damage, shattering the windshields. However, they later found out that the windshields they used were not rated for bird strikes. Revisiting the myth (Season 2, Episode 14), they built a wooden box to hold 12 layers of window glass, and through subsequent tests, found that a frozen chicken did penetrate through more panes of glass than a thawed chicken.

[edit] In popular culture

• In the film Indiana Jones and the Last Crusade, while remembering a quotation by Charlemagne, the title character's father downs an attacking aircraft by scaring a flock of birds into its flightpath with his umbrella.
• Among Japanese aviation engineers and pilots, birds sucked into a jet engine are referred as yakitori after the popular dish.^{[citation needed]}

[edit] See also

• Birdstrike simulator
• Foreign object damage

[edit] External links

• International Bird Strike Committee
• Bird Strike Committee Canada
• BSC USA
• Birdstrike Control Program
• http://wildlife-mitigation.tc.faa.gov/public_html/index.html
• http://wildlife.pr.erau.edu/FAADatabase.htm
• Wired magazine: Bird Plus Plane Equals Snarge
• Aviation Hazard Advisory System
• US Bird avoidance model
• List of significant bird strikes
• Thaw the Chicken Urban Legend