NASA Looks for Safer Icing Forecast For Pilots

Of the many dangers that plague commercial airplanes, icing stands out as one of the most treacherous. The threat of ice build-up on aircraft surfaces has been known and studied for decades, but now NASA is putting new effort into understanding a different kind of ice danger.

A well-known icing problem involves ice forming on wings and other surfaces that can cause drag and power loss on an aircraft. A different threat emerges when airplanes fly into clouds with high ice content found near thunderstorms in very high altitudes. Ice particles, once thought benign because they would simply bounce of airplane surfaces, can accrete deep inside jet engines and shut down the power. This is called “ice particle icing,” to distinguish it from icing caused by super-cooled liquid droplets, which typically occurs at lower altitudes.

There have been more than 240 icing-related incidents in commercial aviation since the 1990s, of which 62 resulted in power-loss likely due to ice particle icing, according to a study authored by Jeanne G. Mason, J. Walter Strapp and Phillip Chow. This condition is difficult for pilots to identify because in many cases the ice is forming only inside the engine, without any visible icing on the wings.

Researchers at NASA’s Langley Research Center are taking a closer look at the phenomenon, which is considered a significant threat to commercial airlines. NASA scientists are developing ways to identify the conditions that cause ice particle icing to better warn pilots about where this might occur.

“It’s something that hasn’t been explored much,” said Chris Yost, a NASA contractor and research scientist with Science Systems and Applications Inc. in Hampton, Va. Yost said his research is at a preliminary stage now, focused on pinpointing the types of clouds connected with ice particle icing. He will present his latest results at the American Geophysical Union fall meeting in San Francisco on Dec. 14.

“These are deep convection, thunderstorm-like clouds,” Yost said. “Thin, wispy cirrus stuff is not so much a problem.”

NASA research is aiming to improve weather forecasts that could steer pilots away from trouble. Building on tools developed to detect surface icing conditions, NASA scientists are using cloud observations from two satellites, CALIPSO and CloudSat.

CALIPSO and CloudSat fly only seconds apart on the same orbit. Together they provide never-before-seen 3-D perspectives of how clouds and aerosols form, evolve, and affect weather and climate. In preliminary research, CloudSat and CALIPSO have been used to build on previous methods of identifying the type of moisture particles that lead to ice particle icing problems. CALIPSO’s lidar is used to create a vertical profile of clouds to accurately measure cloud height while CloudSat provides the estimates of ice concentration in those clouds. Together the two instruments provide very detailed information about the vertical structure of clouds, and the ice particles within them.

Yost and other SSAI researchers have been working with Patrick Minnis, at NASA’s Langley Research Center, on incorporating CALIPSO and CloudSat data into forecast models with the goal of identifying potential ice particle icing conditions.

NASA’s research on ice particle icing began in 2005 with the integration of cloud data from the NOAA satellite GOES. This was followed on by a field experiment on NASA’s DC-8 in 2007 to compare ice particle measurements from GOES with actual aircraft measurements. While this data significantly increased researchers understanding of the icing process, the integration of CALIPSO and CloudSat data has vastly enhanced the ability to see what is within the clouds.

Yost is currently comparing satellite records of weather conditions with the coordinates and time and date of specific airplane power-loss incidents in recent years. The research could illuminate more specifically what type of weather leads to ice particle icing and whether ice particle icing was a factor in these accidents. Future plans include flights with NASA’s DC-8 to take on-board measurements as a comparison point for CALIPSO and CloudSat observations.

Minnis described the group’s ongoing work as a first cut, but envisions it leading to better forecasting of potential ice particle icing conditions in the future.

“The ultimate goal of the project is to be integrated into existing forecast models and eventually into the NextGen (Next Generation Air Transportation System) cockpit system,” Minnis said.

Aviation safety organizations around the world are presently working with the ultimate goal of being able to accurately forecast inflight icing conditions in real-time for pilots. The integration of NASA satellite data into forecasting models is bringing them closer than to that goal, step by step.

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Now Online: Aeronautics Goes E-Book

E-book readers are expected to be among the hottest holiday gifts this year and their growing popularity has stirred NASA to begin reformatting its most popular aviation books to be compatible with the digital devices.

Available on the NASA aeronautics research Web site, the e-books can be downloaded at no charge for use with the Kindle™, SONY® Reader and, eventually, the nook™. Other formats for those without an e-book reader will be available as well.

The first NASA book to be made available is X-15: Extending the Frontiers of Flight by Dennis R. Jenkins. The book tells the story of the pioneering rocketplane that tested the limits of aviation during the 1960s and directly influenced the design and operation of the space shuttle.

"NASA's contributions to aviation affect everyone who has ever stepped foot inside an airplane. Now anyone can read about this historic aeronautical research with the convenience of a hand-held device," said Jaiwon Shin, associate administrator for NASA's Aeronautics Research Mission Directorate.

Next up on the list of books offered is Apollo of Aeronautics: NASA's Aircraft Energy Efficiency Program, 1973-1987 by Mark D. Bowles. This award-winning publication details the innovative research to improve aircraft and jet engine design in order to reduce fuel consumption by 50 percent.

And even as all archived NASA aeronautics books are being reformatted for use with the various e-book readers, plans are set for all future government-published books covering NASA's aeronautics research to be made available in e-book format.

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SOFIA Aloft

An F/A-18 mission support aircraft shadows NASA's Stratospheric Observatory for Infrared Astronomy, or SOFIA, 747SP during a functional check flight Dec. 9, 2009. The flight included an evaluation of the aircraft's systems, including engines, flight controls and communication.

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Chopper Drop Tests New Technology

How do you make a helicopter safer to fly? You crash one.

NASA aeronautics researchers recently dropped a small helicopter from a height of 35 feet (10.7 m) to see whether an expandable honeycomb cushion called a deployable energy absorber could lessen the destructive force of a crash.

On impact, the helicopter's skid landing gear bent outward, but the cushion attached to its belly kept the rotorcraft's bottom from touching the ground. Four crash test dummies along for the ride appeared only a little worse for the wear.

Researchers must analyze the test results before they can say for sure whether the deployable energy absorber worked as designed.

"I'd like to think the research we're doing is going to end up in airframes and will potentially save lives," said Karen Jackson, an aerospace engineer who oversaw the test at NASA's Langley Research Center in Hampton, Va.

According to the National Transportation Safety Board, more than 200 people are injured in helicopter accidents in the United States each year, in part because helicopters fly in riskier conditions than most other aircraft. They fly close to the ground, not far from power lines and other obstacles, and often are used for emergencies, including search and rescue and medical evacuations.

For the test at Langley, researchers used an MD-500 helicopter donated by the U.S. Army. The rotorcraft was equipped with instruments that collected 160 channels of data. One of the four crash test dummies was a special torso model equipped with simulated internal organs. It came from the Johns Hopkins University Applied Physics Laboratory in Laurel, Md.

Technicians outfitted the underside of the helicopter's crew and passenger compartment with the deployable energy absorber. Created by engineer Sotiris Kellas at Langley, the device is made of Kevlar and has a unique flexible hinge design that allows the honeycomb to be packaged and remain flat until needed.

Kellas initially came up with the idea as a way to cushion the next generation of astronaut-carrying space capsules, but soon realized it had many other possible applications. So the concept became part of a helicopter drop test for the Subsonic Rotary Wing Project of NASA's Aeronautics Research Mission Directorate in Washington.

Jackson said researchers tested the deployable energy absorber under realistic conditions. "We crash-tested the helicopter by suspending it about 35 feet (10.7 m) into the air using cables. Then, as it swung to the ground, we used pyrotechnics to remove the cables just before the helicopter hit so that it reacted like it would in a real accident," she explained.

The test conditions imitated what would be a relatively severe helicopter crash. The flight path angle was about 33 degrees and the combined forward and vertical speeds were about 48 feet per second or 33 miles per hour (14.6 meters per second, 53.1 kph).

"We got data to validate our integrated computer models that predict how all parts of the helicopter and the occupants react in a crash. Plus the torso model test dummy will help us assess internal injuries to occupants during a helicopter crash."

Engineers say the MD-500 survived relatively intact as a result of the honeycomb cushion. They plan to recycle the helicopter and drop it again next year, but without the deployable energy absorber attached, in order to compare the results.

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