Sunday, December 30, 2007

Bird Strike Testing

Bird strike testing is an important aspect of aviation these days. Bird strike is an aviation term for when there is a collision between a bird and an aircraft. It is a common threat to aircraft safety and has caused a number of fatal accidents. One of the safety concerns plaguing the aircraft industry since its inception has been bird strikes, or bird ingestion. Flocks of birds seem harmless enough when admiring them from the ground, but experiencing them from the cockpit of an aircraft can prove lethal. A 12 lb Canadian goose struck by an aircraft traveling 150mph at liftoff generates an impact force similar to that created by a 1000lb weight dropping from a height of 10ft. More than 300 people have been killed by bird strikes since the first fatality was recorded in 1912. Since 1960, aircraft-bird collisions destroyed 20 U.S. registered commercial aircraft and, since 1985, 23 U.S. military aircraft. The most common impact areas on the aircraft include the engine inlet, the nose, the canopy, and the wing U.S. Air Force (USAF) officials have reported more than 2500 strikes annually, not including strikes to commercial and U.S. civil aircraft. This became the main reason for carrying out bird strike testing on planes.

At present, all aircraft are required to pass a certification test to ensure safe aircraft flight and operation in the event of a bird strike testing. The current certification test for bird strike testing is performed by firing birds from gas cannon onto aircraft components such as windshields, windows, aircraft engines and leading edge structures. During the design and development stage of new aircraft, an artificial bird is often used in place of the real bird; this helps to improve the repeatability of the bird strike testing and reduce the biological hazard associated with the real birds.

Artificial birds used in bird strike testing are often manufactured from gelatine and formed into a simple primitive geometry (cylinder, hemispherical ended cylinder etc.) to represent the principal mass of the bird (torso). Although previous work has shown good agreement between artificial and real birds (impact pressure and impulse), there are certain situations where this is not the case.

In recent work, the influence of bird shape for large bird species such as the Canada Goose has been investigated using computer stimulation. To control the problem airports invest in bird strike testing management and control, changes to terrain around the airport to reduce its attractiveness as habitat to birds, using bird control personnel and frightening devices (sounds, lights or polytechnics) and sometimes the use of falcons or similar. Pilots use awareness of bird habits and should avoid migratory routes and they will not only ensure safety, this may even ease the load for bird strike testing.