A non-stick wing coating designed to shed insect residue recently tested by NASA and Boeing engineers reduced bug counts and residue by about 40 percent, compared with an uncoated control surface, NASA announced yesterday. Five of the most promising non-stick coatings developed by NASA Langley were tested by the engineers on Boeing’s ecoDemonstrator 757 for two weeks last month in Shreveport, La., a location selected for its “significant bug population.” Since most insects fly relatively close to the ground, the non-stick coatings were tested over 15 flights from the Shreveport Regional Airport that each included several takeoffs and landings.
Aircraft drag caused by bug residue has long been a challenge for the aviation community, NASA said. “Laminar aircraft wings are designed to be aerodynamically efficient,” noted Mia Siochi, senior materials scientist at NASA Langley Research Center in Hampton, Va. “If you have bugs accumulating, it causes the airflow to trip from smooth or laminar to turbulent, causing additional drag. An aircraft that’s designed to have laminar wings flying long distance can save 5 to 6 percent in fuel usage. Surprisingly, all you need are little bugs that trip the flow and you lose part of this benefit.”
Before they could develop and test non-stick coatings, the researchers had to study bug chemistry and what happens when an insect hits a surface at a high velocity. “We learned when a bug hits and its body ruptures the blood starts undergoing some chemical changes to make it stickier,” said Siochi. “That's basically the survival mechanism for the bug.”
The materials scientists turned to nature for inspiration—namely lotus leaves, which repel water—to create the right combination of chemicals and surface roughness in the test coatings. Engineers at Langley ultimately developed and tested more than 200 coating formulations in a small wind tunnel, then took a number of those to flight on the wing of a NASA jet. They then selected the best candidate non-stick coatings to fly on the Boeing ecoDemonstrator.