F-22를 위협하는 비대칭 물체

http://www.af.mil/news/story.asp?id=123093746 Langley officials fight to keep F-22s from being damaged by Tech. Sgt. Russell Wicke Air Combat Command Public Affairs 4/9/2008 - LANGLEY AIR FORCE BASE, Va. (AFPN) -- The Air Force's newest and most technologically advanced fighter, the F-22 Raptor, is under attack here. Free-falling clams dropped by in-flight birds are regular air threats to the F-22 as gulls drop fist-sized mollusks on the Langley Air Force Base runway to break open the shell-fish appetizer. The birds' shelling device just happens to be a convenient launch pad for the F-22. Although the gulls remove half their mess -- slurping up tender meat from the runway -- they leave behind hard, brittle sea shells for an F-22 to suck up through its engine intake that can cause severe damage. Although the Air Force is wildlife friendly, Lt. Col. Lawrence Spinetta, the 1st Fighter Wing Safety Office chief, isn't willing to let a $10.2 million jet engine go to the birds -- or the clams. Langley AFB officials run an aggressive flight-safety program to mitigate the Bird and Wildlife Aircraft Strike Hazard, also called BASH. "BASH is particularly important for Raptors because they are so expensive," Colonel Spinetta said. "If we lose one aircraft, it costs the Air Force and taxpayers $135 million. Most wildlife threats to aircraft are birds, although deer, coyotes, turtles and even clams are also foreign-object-debris threats, said Tom Olexa, a wildlife biologist from the U.S. Department of Agriculture at Langley AFB. "A key component of BASH is to ensure the safety for our pilots and aircraft," Mr. Olexa said. "But we also want to protect (wildlife) from being struck by our aircraft. There's a conservation here that we're all responsible for." All people, not just Air Force officials, are obligated stewards of the environment, he said. But "aircraft conservation" is a priority for Air Combat Command officials, because Air Force "birds" belong to taxpayers, Colonel Spinetta said. "A little sparrow may not seem like it's a threat to a 60,000-pound aircraft, but it is, particularly if it gets sucked down the intake," he said. Even if a bird strike doesn't cause a crash, damages soar into the millions. Federal Aviation Administration officials claimed birds cost the civil aviation industry about $600 million per year. Air Force officials coughed up approximately $16 million in 2007 from bird-strike damages. Only a few types of birds account for the majority of the damage. Certain species in particular do more than peck at the Air Force wallet. For example, the turkey vulture alone accounts for nearly 800 strikes and more than $51 million in Air Force flying history, said Dan Sullivan, the Air Force BASH deputy chief and wildlife scientist. It ranks No. 1 in Air Force bird strikes. However, the most expensive bird is the American white pelican. In only 18 strikes, this bird accounts for more than $257 million in damages. Mr. Sullivan said this cost is attributed to the size and weight of the bird -- a whopping 20 pounds -- compared to an average 5 pounds for the turkey vulture. "The black vulture and turkey vulture are the greatest threat to Air Force aircraft overall because they are somewhat large and soar at high altitudes -- about 3,000 feet," Mr. Sullivan said. "During the day as the air warms up, they ride a rising thermal draft. Their high altitude makes them hard to detect from the ground." These vultures, among other avian species, are increasing in population because of U.S. conservation efforts, he said. Other threatening birds at high altitudes include all raptor species. Mr. Sullivan said these birds are also increasing in numbers because the U.S. stopped using dichlorodiphenyltrichloroethane, a pesticide known as DDT. The cessation of DDT use was necessary, he said, because it threatened the once-endangered bald eagle. But an offshoot of this action means the Air Force shares more of its airspace. And sharing airspace with birds is a moderate concern to Air Force pilots. "I think it would be a life-changing event to have a 5-pound Canadian Goose smash through your windshield at 400 knots," said Colonel Spinetta, who is also an F-15 Eagle pilot. No pilot wants to share the cockpit with fowl, but avoiding birds in midair isn't an option. "It's very difficult (to dodge a bird) at the speeds we're going, (350 to 400 mph at low altitude)," said Capt. Ray Thaler, an F-22 pilot and chief of flight safety. "(With) birds being very small, you never usually see them until the last half-second." The problem is, he said, a single bird can take out an entire engine, could break through a canopy and hit you in the cockpit. This becomes more serious in single-engine aircraft like the F-16 Fighting Falcon. Although there is no pilot training for bird strikes as a specific hazard, Captain Thaler said they train for many procedures, including low-altitude engine loss, which would apply to bird strikes. Almost nothing can be done, short term, to avoid high-altitude strikes. But the Langley AFB BASH team is heading up a project to track the migration of the osprey, the fifth most-dangerous bird species to aircraft, Colonel Spinetta said. There are more than 72 osprey nests within a 20-mile radius of Langley AFB. To mitigate the growing threat, officials from the 1st FW, NASA and USDA came up with a unique way to track the osprey. "Captured birds were fitted with Global Positioning Systems-capable transmitters ... (that) transmit the altitude, speed and direction of travel of each bird every two hours," Colonel Spinetta said in an editorial for the Flight Safety Magazine. "As a result, Langley AFB has been able to pinpoint nests and focus its reduction, suppression and prevention efforts to eliminate many osprey hazards." The nests are usually relocated to safer areas by USDA members. Other more traditional techniques for eliminating hazards involve harassing birds on the airfield, Mr. Olexa said. The most common tool is simply a combination of pyrotechnics and artificial bird distress calls, called bioacoustics. This, he said, is especially useful for birds like gulls that drop their food on the runway. Other long-term techniques take a bit more forethought, called habitat manipulation. "The trick is to make the airfield less attractive to wildlife," Mr. Sullivan said. One way is by planting certain grass species that cause an upset stomach to geese. Another example is to avoid planting fruit/nut producing trees. The Langley AFB BASH team also covered tall airfield objects with spiny metal strips, or cone shaped devices, to deny perching to birds. One technique, which is considered a last resort, is called depredation, or lethal action. But Mr. Sullivan said the purpose of lethal action is to remind other birds there's an actual threat, not to terminate the flock. "Most of what the Air Force does in its BASH program is non-lethal," he said. "We move the birds away from the threat of aircraft." The lethal action Air Force officials take is a response to birds becoming accustomed to non-lethal methods. Lethal action on a few birds prevents the majority from settling in an area where they would be more endangered from aircraft strikes. Birds are smart; they begin to understand when there's a real threat, or just harassment, Mr. Sullivan said. The techniques used by USDA and BASH teams have earned credibility with Air Force commanders. From 1995 to 2000, Langley AFB officials spent more than $1.6 million in aircraft damage from wildlife strikes. Since they employed the services of USDA in 2001, there was a 98 percent reduction in cost. From 2001 to 2006 wildlife strikes accounted for a mere $31,000. "Pocket change," Colonel Spinetta said, compared to the previous five years' cost. This kind of savings is exactly what BASH teams are designed to accomplish. "We're flying multimillion dollar aircraft that belong to our taxpayers," Mr. Sullivan said. "It's our responsibility to mitigate loss of life and equipment." But the effort goes much further than a dollar figure. Human life and wildlife are on the line, he said. And that's why BASH and USDA Wildlife services are partnered up to save aircraft, pilots, birds and maybe even a few clams.