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What is a bird strike? How can we keep planes safe from them in the future?

US Airways Flight 1549 crash-landed in the Hudson River after likely colliding with a flock of Canada geese



David Mueller, via Wikimedia Commons

US Airways Flight 1549 took off from La Guardia Airport in New York City at 3:03 P.M. Eastern time on its way to Charlotte, N.C., with 150 passengers and five crew members on board. As it gained altitude, it reportedly ran into a "massive flock of birds," according to The New York Times, and the jet engines began making noises—and lost power.

Heading north without engine power, the pilot of the Airbus A320 changed course and—in what some are describing as a heroic but calm act—glided to a watery landing in full view of buildings on Manhattan's west side. "The pilot got on and said, 'You guys got to brace for a hard impact,'" passenger Jeff Kolodjay told the Times. "That's when everyone started to say their prayers. I got to give it to the pilot, he did a hell of a landing." When the pilot, Chesley Sullenberger, emerged from the plane, he had not even donned a life vest, according to the Times of London.

A flock of eight-pound (3.5-kilogram) geese had apparently brought down a plane, plunging it and 155 people into the frigid waters of the Hudson River.

A group of rescue boats soon plucked shivering passengers from the wings. They have been taken to area hospitals, and only minor injuries have been reported so far.

But not every bird-struck flight has been so lucky. The first fatal strike was recorded in 1912, just nine years after the Wright Brothers first flight in Kitty Hawk, N.C. The space shuttle Discovery pulverized a bird during a launch in 2005, although no damage to the spacecraft was recorded.

With soaring air traffic and migratory birds recovering from DDT and other pesticides, the number of bird strikes has been rising over the last 20 years, from about 1,500 in 1990 to about 8,000 last year.

In Thursday's crash, investigators believe geese may have been sucked into both engines during take-off, an unusual situation that is simulated, but not tested, during "bird strike" certifications by aircraft engine manufacturers.

To find out more about the dangers of bird strike, we spoke with Richard Dolbeer, a wildlife biologist and expert on bird strikes who retired in September after working 36 years for the U.S. Department of Agriculture in Sandusky, Ohio.

[An edited transcript of the interview follows.]

Why are birds such a threat to aircraft?
It basically comes down to the physics equation for kinetic energy: Energy is proportional to mass times velocity squared. The velocity of the aircraft allows for the impact of this feathered bird to generate enough force to cause an engine to malfunction. (A 12-pound, or 5.5-kilogram, Canada goose struck by an aircraft traveling 150 miles, or 240 kilometers, per hour at liftoff generates the force of a 1,000-pound, or 455-kilogram, weight dropped from a height of 10 feet, or three meters, according to Birdstrike USA.—Editor's Note)

When a plane is taking off, it is going 170 miles (275 kilometers) per hour  and accelerates to several hundred mph. The engine's fan blades during taking off—like this plane today—are going 3[,000] to 4,000 rotations per minute, and the tips of those turbofan blades are actually at the speed of sound or greater—700 to  800 mph (1,125 to 1,285 kilometers per hour). When a bird hits one of those fan blades, there's a tremendous energy transfer from the bird to the engine, and that's basically why a bird can cause serious damage to an aircraft engine.

We do know that for this flight today, Canada geese would be the most likely species. They typically weigh eight to 10 pounds (3.5 to 4.5 kilograms). They are a large bird so you can imagine the force that's generated.

What is the typical outcome of a bird strike?
Since 1990 the FAA (Federal Aviation Administration) has compiled statistics on bird strikes. I'm the author of a report showing that 12 percent to 15 percent of the strikes result in some damage to aircraft. In the majority of strikes, 85 percent or more, nothing happens: The bird bounces off the plane or a small bird…just goes through the engine and there's no discernible damage [to the plane]. In a small percentage you get damage, and in a smaller percentage you get catastrophic damage.

Some recent examples?
Two months ago in Rome, a Boeing 737 operated by Ryanair, flew through a flock of starlings. These are small birds that weigh about 90 grams, or about…[three]…ounces. It hit a large flock of them and there was damage to both engines.The pilot just sort of flew the plane into the runway to control it, and it collapsed the landing gear and caused major damage. Everyone had to be evacuated just like today, and there were some injuries but no fatalities.

Anther recent incident occurred in Belgium last May 2008.  A Boeing 747 cargo airplane, operated by Kalitta Air, was leaving the Brussels airport, and it ingested a bird into one of the engines. The pilot made a decision to abort the takeoff.  He wasn't able to stop the aircraft before the end of the runway. The plane broke in two and was destroyed. Luckily, it was full of cargo and not passengers. [The entire crew survived.]

Are certain aircraft more likely to get hit than others?
Bird strikes are five times more likely to occur on planes with engines mounted under the wings, such as the Boeing 737 or the Airbus A320, than on planes with engines mounted on the fuselage, like the Boeing MD-80 and some...[smaller]...jets.* It is probably because the airflow over the MD-80 causes the birds to get blown away from the engines.

Are bird strikes on the rise?
IIn 1990 there were only 1,750 strikes reported. Right now, for 2008, there will probably be 8,000 bird strikes reported. In 2007 there were 7,600.

One factor is there's probably better reporting today. I also think there has been an increase in populations of birds because of the various environmental programs put in place in the late 1960s and the early 1970s. The resident Canada goose population in the United States, for instance, has increased from one million in 1990 to 3.9 million in 2008.

We're also seeing more and more birds adapt to urban environment, and they find airports very attractive because they provide a large grassy space they can come feed to and rest.

Finally, we've got air traffic increasing 2 percent a year, and the planes are quieter. Most of the noise comes out the back of the engine now, as opposed to propeller-driven aircraft and older jets where noise came out the front.  Birds are less able to detect modern aircraft.

How can we cut down the risk of bird strikes?
There's no silver bullet. There's no magic chemical you can spray or sound you can project that is going to scare the birds away. What it takes, and what we advocate for airports worldwide is integrated management with three pillars:

The first pillar is habitat management. Manage habitat in the airport and surrounding area at least two miles from the airport. You don't want to have any bird attractants like landfills that attract gulls or other scavenging birds. On the airport, you want to eliminate standing water because water is a magnet. You want to have good drainage, and manage the grass and keep it mowed. You also want to keep [animal] populations under control so you don't attract birds of prey. You want to eliminate any perching structures on or around the airport and basically make the airport as sterile as possible.

The second pillar is having trained bird-control teams that patrol the airport and harass and disperse any birds that come onto the airport grounds. They use pyrotechnics and noisemakers that flash lights and that will scare—but not kill—the birds. Some airports use trained dogs. A few airports use trained falcons.

The last resort is lethal control or removal of birds from surrounding areas, which is only done under permit because all of these birds are federally protected under the Migratory Birds Treaty Act. Canada geese, for instance, are rounded up in early summer and euthanized.

That takes care of the airport environment. Once the plane gets away from the airport and the plane is gaining altitude there are a few things that hold promise but are not operational. How do we make aircraft more detectable or noticeable by birds? One concept is using pulsating landing lights instead of having steady lights in order to catch the birds' attention so they realize something fast is approaching. We also know birds see in the ultraviolet range beyond what humans see and one idea is to use UV-reflecting paint.

The final thing being worked on is bird-detecting radar. We have radar that detects weather and radar that detects wind shear around airports. You can program radar to filter out weather and show the birds. That would be available to pilots and air traffic control to help pilots steer around concentrations of birds in the air.

*Note (1/16/09): The original sentence identified the MD-80 as a McDonnell Douglas plane. It also was not clearly stated that the MD-80 is a long-range passenger airplane.

 

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