Future plane could show where it's hurt


April 07--Thanks to research at Cessna Aircraft, the skin of a composite airplane might one day "bruise" or change color, making damage easier to detect.

The plane might be fitted with an aircraft-grade applique with a design rather than paint, cutting pounds of weight. And the skin itself might be much smoother, meaning smoother airflow and less drag.

Those developments would lead to fuel savings, maintenance improvements and increased aircraft performance, officials say.

Cessna's research is part of a NASA effort to make airplanes of the future greener and quieter.

NASA recently awarded contracts to four industry and academic teams -- Cessna, Boeing Research and Technology, Massachusetts Institute of Technology and Northrop Grumman Systems.

Each team will research futuristic ideas for aircraft that could potentially enter service between 2030 and 2035.

NASA refers to this time frame as "N+3" -- technology three generations more advanced than today.

NASA's $1.9 million, 27-month contract with Cessna is for research on the use of protective outer skins on composite aircraft.

It's what NASA calls a "revolutionary structural concept" that can protect planes against lightning, electromagnetic interference, extreme temperatures and object impacts. Today, composite planes must be overdesigned, or beefier, to handle those forces.

Under the NASA contract, a team of six Cessna engineers will look at ways of making a lighter and leaner composite structure by slipping composite layers over a lighter exterior. The layers would slip over the entire airplane and its wings.

"We're trying to come up with the right set of materials and combination of layers to do all the functions of what's currently done by the composite skin itself," said Vicki Johnson, Cessna engineering specialist and the principal investigator for the NASA contract.

The layers might include a foam layer for impact absorption followed by an outer layer to cover up bumps and gaps.

"Part of the research is to figure out how many layers will it take to meet all of the requirements," Johnson said. "It might take two, but it might take three or four."

NASA calls the research STAR C2, which stands for six areas of focus -- smoothness, thermal insulation, absorption, reflection of ultraviolet radiation, the ability to conduct a large amount of electric current along with a cosmetic or appealing surface.

The team is in the process of selecting composite materials for testing. It will begin building test panels this summer.

Eventually, the team will come up with about 175 test panels of potential concepts, Johnson said.

"Our goal is to show that this is feasible," Johnson said.

Cessna will use commercially available off-the-shelf materials for the panels, she said.

The ability to repair composite structures is also a big issue.

In an aluminum airplane, damage is easy to detect and repair, said Cessna spokesman Doug Oliver. "We're very good at doing that."

It's more difficult, however, to detect and repair damage to composites.

"If you hit a composite fuselage with a wrench, you may not see a mark, but you may have caused damage within the structure," Johnson said.

The research will look at the potential for a material that would "bruise," when damaged, she said. "It would change color if it got hit."

NASA's contract with Cessna began in January. It's the second phase of NASA's effort.

Johnson and her team took part in the first phase of designing an aircraft of the future.

They teamed with GE Aircraft Engines and Georgia Tech to design a 20-passenger aircraft with the thought of it entering service in 2035.

The goal was to reduce fuel burn by 70 percent over today's' aircraft and reduce noise and emissions.

The turboprop aircraft they designed included advanced systems and engines not yet in existence.

The design would cut fuel burn by 69 percent, Johnson said.

"That made us really happy," he said.

Reach Molly McMillin at 316-269-6708 or mmcmillin@wichitaeagle.com.