AUGUST 2015 19 consumption on a long-range flight, according to Christensen. Boeing engineers experimented with a wing high-lift device, called a variable camber Krueger flap that unfolds from the underside of the wing, using it as an impromptu bug shield in different positions on the 757’s left, or port-side, wing. These customized Krueger flap angles were responsible for a significant reduction in insect splatter on the wing’s leading edge, which was a breakthrough. “All of the focus might have been on the bugs, but these tests validated leading-edge technology on the wing as well,” Farrell said. “That was the fun part.” Working independently, a 10-person NASA team applied and monitored five different coatings on the 757’s starboard wing to see if it would limit bug contamination and airflow disruption. The aerospace agency, which eventually will share its test results publicly, found one of the treated layers resulted in a 40 percent decrease in splatter debris. In previous testing in Hampton, Va., NASA researchers had used a “bug gun” to shoot crickets and fruit flies at stationary surfaces, firing just inches away to ensure full impact. In Shreveport, they introduced surface roughness and different chemicals to a wing typically moving at 150 mph (240 kilometers per hour) on low-altitude flights, and determined a combination of the two approaches worked best. “The reduction is 40 percent, not 100 percent, so there’s still something we don’t understand to prevent bugs from sticking at those speeds,” said Mia Siochi, NASA research materials engineer. “But 40 percent is still a significant number.” Lynn Kimsey, University of Photos: (Clockwise from top left) Boeing product development engineers Jeff Burton, left, and Sabre Hecht inspect a removable wing panel for bugs; Alex Mulbah, flight-test engineer, enters data on a laptop while seated on the ecoDemonstrator 757; more than 40,000 bugs, including a paper wasp like this one, splattered onto the 757’s right wing during testing; following bug testing, the ecoDemonstrator 757 was retired and is being recycled. breeding ground and test site. “It was all about the bugs,” said Christensen, ecoDemonstrator 757 program manager, Commercial Airplanes Development. “Were they going to show up when we were there? They definitely showed up.” At Shreveport Regional Airport, the right, or starboard, wing of the 757, wearing experimental coatings applied by NASA, registered a weighty 40,000 insect hits during 83 flights over 10 days. It didn’t look much different from a motor home after a vacation, collecting all sorts of streaks, smears and skeletal bug remains. While it might seem like no more than a messy inconvenience, a jet wing splattered at lower altitudes will disrupt smooth flow of air over the contour of the wings for the rest of the flight, with minuscule bug debris, dirt or even a scratch creating drag and extra fuel consumption, Christensen said. What the ecoDemonstrator 757 team learned in Louisiana is that the usual bug buildup can be prevented to varying degrees, potentially leading to a significant savings in fuel
Frontiers August 2015 Issue
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