November 4, 2013
Splattered Bugs Can Be A Real Drag For Aircraft
Brett Smith for redOrbit.com - Your Universe Online
Splattered bugs on your windshield can be gross to look at and they can even obstruct your view. However, for some, the ordeal can be much more of a problem than just an unsightly nuisance.
For pilots, splattered bug guts can be a real drag, quite literally. If an airplane wing accumulates enough splattered bugs, it disrupts the flow of air over the wing and creates more drag on the plane – causing increased fuel consumption.
According to NASA, a group of its researchers dubbed “the big team” recently tested a series of different wing coatings to see if any might be able to reduce bug residue and eliminate unnecessary drag. Take-off and landing tests were performed over the course of a few days using the HU-25C Falcon aircraft at NASA’s Langley Research Center in Virginia.
"The reason we do these tests at low altitudes or do a lot of takeoffs and landings is because bug accumulation occurs at anywhere from the ground to less than 1,000 feet," said Mia Siochi, a materials researcher at NASA Langley.
Not only can bug residue increase fuel consumption, it can also cause greater pollution that results from burning extra fuel. The material scientists performing this work as part of NASA's Environmentally Responsible Aviation (ERA) project said both issues are a concern for them.
For the series of test flights, researchers affixed eight different surfaces covered with various synthetic coatings to each wing of the HU-25C. As a reference, they also performed a run with and ‘uncoated’ wing.
"We fly [test] controls and assume that if the other surfaces were not coated they would get the same density of bug strikes," Siochi said.
If the engineered coatings were found to have fewer bug splats after a test run than the control surfaces, they were considered to be working. The team found that the coated surfaces did indeed have fewer and smaller splats.
The NASA team noted a smaller residue area on the coated surfaces than an untreated surface. In some instances, heights of residue splatter were also reduced. The mix of shorter residue and smaller splat area can help reduce disruption in the flow of air across a wing surface, also called laminar flow. Smaller bug splats also increase the chance that residue will come off during flight, keeping the wing clean.
Despite positive signs, the NASA team said it will probably be a while before the coatings end up on commercial airplanes. In addition to reducing bug splatter, the coatings have to be tough enough to withstand years of operation. The scientists said current durability testing of the coatings include conditions that imitate rain, humidity and ultraviolet radiation.
Siochi noted that if the savings in fuel could make up for the costs associated with using the coatings it would be feasible. "So we have to get through that hurdle of practical application of these materials," she said.
Despite the somewhat unappealing nature of the bug research, NASA researcher John Gardner, who previously worked with Siochi and colleagues on the study of bugs and aircraft aerodynamics, said he was excited to ride along on the flight tests to monitor the coatings. He said flying through the hot, humid, buggy Virginia air was actually a good time.
"I've done other research projects," Gardner said, "and this is definitely the most fun I've had."