Since, the early day’s men flew in sky and shared it with other flying animals, collision have occurred some leading to great catastrophic disaster. The seemingly insignificant organism like bird wandering for foods, water and sometimes migrating for survival from extreme climate, strike aircrafts and causes loss of life and belongings. The effect of collision obviously depends on the mass of birds and relative velocity of bird and aircraft. Military exercises at low and high altitude and thus are more exposed to the threat. Pilots may except to encounter two to five strike in his career. More than 33000 bird strikes were recorded by Federal Aviation Administration (FAA) in 1990 to 2000. Depending on environment, different parts of world have different exposure to birdstrike as depicted in the pie-chart below.

Figure 1 Birdstrikes by ICAO ; Source: www.airbus.com

The annual damages caused by the birdstrike have been estimated to be $400 million in U.S alone and over $1.2 billion to the commercial aircrafts on the planet. The major point of impact on the vehicles are at the frontal area which includes nose, engine, cowl, wings etc. The locations and percentage of impact on an aircraft, based on the statics of pilot and maintenance staffs is shown in fig.2.

Figure 2 locations and percentage of impact; Source http://www.boeing.com

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. The percentage of birdstrike on aircrafts based on altitude is shown in the figure shown below.

Figure 3 distribution of birstrike based on altitude

1.MAJOR BIRD STRIKE ACCIDENTS RECORDED

Source: www.airbus.com

S.N	YEAR	PLACE	DESCRIPTION	DEATHS AND/OR DAMAGES
1	1960	Boston	Eastern Air Lines, a Lockheed L-188 Electra flying from Boston, flew through a flock of common starlings during take-off, damaging all four engines	62 fatalities out of 72 passengers.
2	1964	Houston	NASA astronaut Theodore Freeman was killed when a goose shattered the Plexiglas’s cockpit canopy of his Northrop T-38 Talon.	Death of Theodore Freeman.
3	2005		The Space Shuttle Discovery also hit a bird (a vulture) during the take-off of STS-114.	No obvious damage to the shuttle.
4	2007	Rome,	Boeing 767 aircraft, on takeoff, ingested yellow legged gulls into both engines.	The aircraft returned to Rome with both engine damaged.
5	2007	near Manchester	Boeing 757 suffered a bird strike supposedly a heron, was ingested by the starboard engine.	The plane landed safely back at Manchester.
6	2009	Hudson	US Airways Flight 1549, shortly after takeoff, ditched into the Hudson River in 2009 after experiencing a loss of both turbines.	All 150 passengers and 5 crew members were safely evacuated after a successful water landing.
7	2009	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.

2. COURSE OF ACTIONS OF BIRD STRIKE:

The most bewildering situation exists in the cockpit after the birdstrike has been confirmed and any small wrong decision of crew could take them to the no returning death. The best defense against this threat is a well-trained crew in the cockpit. A confirmed birdstrike should be considered, if the flight crew:

• Sees birds flying very close by, and Hears a bang, or

• Observes temporary or permanent changes in the engine parameters, or

• Hears changes in the engine sounds, or

• Observes significant changes to flight instruments, e.g. unreliable airspeed.

If a birdstrike is confirmed, there are three potential situations:

2.1. THE AIRSPEED IS BELOW 100 kt (1knot = 1.852 km/hr.)

A rejected takeoff at low speed has no serious consequences and shall be envisaged for any suspected or confirmed birdstrike. The aircraft will return to the ramp for an integrity check. The consequence will be a flight delay, but events analysis have shown that the next takeoff is then performed with a fully operational aircraft.

2.2. THE AIRSPEED IS ABOVE 100 knot AND BELOW V1

V1 means the maximum speed in the takeoff at which the pilot must take the first action. A rejected takeoff at high speed is a more serious matter. Action must be taken quickly to ensure a complete stop before the end of the runway. If the birdstrike is confirmed, but engine bird ingestion is only suspected, the Captain must evaluate other factors: 

− How many engines are affected?  (Any decision may differ for a 2 or a 4 engine aircraft.)

− Statistically, a continued takeoff followed by an In-Flight Turn Back (IFTB) is a preferred option.

If the birdstrike is confirmed and engine bird ingestion probable, aborting the takeoff can be a good decision. This allows the engines to be inspected. In any case, takeoff must be interrupted, if a thrust loss is detected before V1.

2.3. THE AIRSPEED IS V1 OR ABOVE

The takeoff must be continued, unless the Captain judges that the aircraft will not fly safely after liftoff (e.g. in the case of uncontained engine failure or total thrust loss on more than one engine).

3. PREVENTIVE MEASURES:

Generally, bird control methods vary with location, species, bird behavior, season, and climate etc. The success of certain methods also differs between airports. As a result of this, Airports have a bird control programme that is based on local experience that fits best to the local situation. The best measure to avoid birdstrike is the use of bird detection radar and the other major ways are as follows.

3.1. HABITAT MODIFICATION

Habitat modification is considered to be a very effective and enduring way of preventing the presence of birds. Rodents and insects are potential food sources, for instance attracting birds of prey or flocks of passerines. Control of the prey population is a possible solution. Apart from this fish or meat industries, landfills, sewer treatment plants or lagoons, birds being fed in parks, grain storage and agricultural activities are the other sources of food attractants. Sewage lagoons or treatment plants and on-base landfills should be situated as far from the runways as possible. Agricultural of relatively unattractive crops like hay, cotton and flax may decrease the numbers of birds present. Short grass attracts more hazardous bird species and thus long-grass management is generally considered the right approach. As fresh water is very important to many birds, rain pools can be attractive drinking and preening sites and thus should be eliminated to the greatest extent possible.

3.2. RESOURCE PROTECTION

Resource protection comprises all activities that make areas inaccessible or less attractive to birds. Access to attractive areas can be denied or discouraged by using physical barriers. Water bodies such as ponds or lakes can be made inaccessible with wire systems. Waste sites at meat- or fish-processing industries should also be carefully covered. A number of chemical repellents Reta, Polybutene, Methyl anthranilate, amino pyridine etc. are currently used in most of countries including the United States and Australia. Birds can (temporarily) be chased away with sounds by using pyrotechnics, propane gas cannons and bioacoustics. Remote-controlled model aircraft, shaped in the silhouette of a bird of prey, have been tested with success.

3.3. FLIGHT PATH

Pilots have very little training in wildlife avoidance nor- is training required by any regulatory agency. However, they 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 birdstrike occur below 3,000 feet (910 m).