Early reports suggest that a bird strike caused a jet plane to crash in the
Hudson River near Manhattan today, leaving questions about how a little flying
animal could down a big airliner.
More than 200 people have been killed
worldwide as a result of wildlife strikes with aircraft since 1988, according to
Bird Strike Committee USA, and more than 5,000 bird strikes were reported by the
U.S. Air Force in 2007. Bird strikes, or the collision of an aircraft
with an airborne bird, tend to happen when aircraft are close to the ground,
which means just before landing or after take-off, when jet engines are turning
at top speeds.
The incidents are serious particularly when the birds,
usually gulls, raptors and geese, are sucked into a jet engine and strike
an engine fan blade. That impact displaces the blade such that it strikes
another blade and a cascade can occur, resulting in engine failure.
12-pound Canada goose striking an aircraft going 150 mph at lift-off generates
the force of a 1,000-pound weight dropped from a height of 10 feet, according to
Bird Strike Committee USA.
Today's incident, which occurred just after US
Airways flight 1549 (an Airbus 320) had taken off with more than 150 passengers
and crew members from LaGuardia Airport in New York, en route to Charlotte,
N.C., involved a flock of geese, according to CBS News. Reports indicate no
deaths or serious injuries as of this writing.
Large aircraft are certified
to be able to keep flying after impacting a 4-pound bird, however 36 species of birds
in North America weigh more than this, according to the committee. Even
smaller birds, such as starlings, can cause engine failure.
The greater the
difference in the speed of the plane and the bird, the greater the force of the
impact on the aircraft. The weight of the bird is also a factor, but the speed
difference is a much bigger factor.
Flocks of birds are even more dangerous
as they can result in multiple strikes.
Delicate birds, delicate aircraft
Dale Oderman, associate professor of aviation technology at Purdue
University in Indiana says birds can be very dangerous to aircraft, particularly
in the first several thousand feet after take-off, where the birds are flying.
"Obviously, geese or another large bird would be much more hazardous than a
little black bird," Oderman said. "The speed at which the two are moving causes
the bird to get ingested into the engine. And the engine is very delicate to
withstanding a major impact."
He added: "It just shuts the engine down."
Basically, if the
birds get too close to the engine's intake, it's like a vacuum - the birds
just get sucked in.
"The initial stages of a jet engine are made up of a lot
of compressor blades. Those aren't very big and they can be very easily
damaged," Oderman told LiveScience. "Even if one of those things breaks off,
then the one blade will go through the rest of the engine and it's like shrapnel
to the engine."
And in the case of the Hudson River crash, the birds
apparently took out both engines.
"Apparently in this particular case it
seems both engines were hit. If it was a flock of birds they flew thought it
wouldn't be a surprise to me," Oderman said.
Airports, Oderman said, take
several precautions to keep planes safe from birds. For instance, they often
don't plant many trees nearby, as these are nesting areas for birds. Since La
Guardia is right on the water, he noted, there are a lot of water birds around.
Bird strike remains
Bird strikes are on the rise, according to the
committee. After a bird strike in the United States, the remains, called snarge,
are sent to the Smithsonian Institution's Feather Identification Laboratory to
identify the species, according to WikiPedia.
Bird and other wildlife
strikes to aircraft result in more than $600 million in damage a year, according
to Bird Strike Committee USA. Five jet airliners have had major accidents
involving bird strikes since 1975, the committee says. In one case, about three
dozen people died.
NASA worries about bird strikes, too.
During the July
2005 launch of Discovery on mission STS-114, a vulture soaring around the launch
pad impacted the shuttle's external tank just after liftoff. With a vulture's
average weight ranging from 3 to 5 pounds, a strike at a critical point on the
shuttle - like the nose or wing leading thermal protection panels - could cause
catastrophic damage to the vehicle.
NASA put safety
measures into place in 2005 to reduce the odds of bird strikes with the
shuttle. The agency particularly wants to avoid bird strikes to the shuttle's
fuel tank that could damage the heat shield during launch and landing.
instance, NASA has a special during launch countdown where they can stop to wait
for birds to pass. And during landing, NASA has a sound cannon that they fire to
make sure the runway is clear from birds to make sure shuttle isn't damaged