Researchers are relying more on computational analysis to see how aircraft designs and ice-protection systems will react in icing conditions.
A tunnel that builds ice
The Icing Research Tunnel (IRT) at NASA Glenn Research Center is that center's oldest and busiest facility. Built at the end of World War II, it was critical in developing ice-protection systems for piston-powered and propeller-driven aircraft. Since then, it's been updated with computer controls, a larger fan motor, better fan blades, and electronic data collection.
The closed-loop subsonic wind tunnel generates airspeeds from 50 to about 400 mph and temperatures as low as 30°F, controllable to within 1°, regardless of the weather outside, thanks to a 1,800-ton heat exchanger. To initiate icing, 10 spray bars eject supercooled water droplets between 15 and 40 m in diameter and create air with a liquid water content from 0.5 to 2.5 gm/cu m. The test section measures 6 ft high, 9 ft wide, and is 20 ft long, large enough for many full-sized aircraft components and large-scale models. An 8.6-ft-diameter turntable in the test section rotates ±20° to vary angles of attack.
Today, engineers use the tunnel to investigate low-power ice-protection systems, anti-icing fluids, and icing on fixed-wing and rotor craft vehicles. They also use it to certify ice-protection systems for military and commercial aircraft and understand the physics of icing.