Beth Dickey
Headquarters, Washington
202-358-2087
beth.dickey-1@nasa.gov

Gray Creech
Dryden Flight Research Center, Edwards, Calif.
661-276-2662
gray.creech@nasa.gov

RELEASE: 08-169

NASA EVALUATES SENSOR TECHNOLOGY FOR FUTURE AIRCRAFT EFFICIENCY

EDWARDS, Calif. -- NASA is evaluating an advanced, fiber optic-based
sensing technology that could aid development of active control of
wing shape. Controlling a wing's shape in flight would allow it to
take advantage of aerodynamics and improve overall aircraft
efficiency.

The Fiber Optic Wing Shape Sensor system measures and displays the
shape of the aircraft's wings in flight. The system also has
potential for improving aircraft safety when the technology is used
to monitor the aircraft structure.

Flight tests on NASA's Ikhana, a modified Predator B unmanned aircraft
adapted for civilian research, are under way at NASA's Dryden Flight
Research Center at Edwards Air Force Base in California. The effort
represents one of the first comprehensive flight validations of fiber
optic sensor technology.

"Generations of aircraft and spacecraft could benefit from work with
the new sensors if the sensors perform in the sky as they have in the
laboratory," said Lance Richards, Dryden's Advanced Structures and
Measurement group lead.

The weight reduction that fiber optic sensors would make possible
could reduce operating costs and improve fuel efficiency. The
development also opens up new opportunities and applications that
would not be achievable with conventional technology. For example,
the new sensors could enable adaptive wing-shape control.

"Active wing-shape control represents the gleam in the eye of every
aerodynamicist," Richards said. "If the shape of the wing can be
changed in flight, then the efficiency and performance of the
aircraft can be improved, from takeoff and landing to cruising and
maneuvering."

Six hair-like fibers located on the top surface of Ikhana's wings
provide more than 2,000 strain measurements in real time. With a
combined weight of less than two pounds, the fibers are so small that
they have no significant effects on aerodynamics. The sensors
eventually could be embedded within composite wings in future
aircraft.

To validate the new sensors' accuracy, the research team is comparing
results obtained with the fiber optic wing shape sensors against
those of 16 traditional strain gauges co-located on the wing
alongside the new sensors.

"The sensors on Ikhana are imperceptibly small because they're located
on fibers approximately the diameter of a human hair," Richards
explained. "You can get the information you need from the thousands
of sensors on a few fibers without the weight and complexity of
conventional sensors. Strain gauges, for example, require three
copper lead wires for every sensor."

When using the fiber optic sensors, researchers do not require
analytical models for determining strain and other measurements on
the aircraft because data derived with the sensors include all of the
actual measurements being sought.

Another safety-related benefit of the lightweight fiber optic sensors
is that thousands of sensors can be left on the aircraft during its
lifetime, gathering data on structural health and performance. By
knowing the stress levels at thousands of locations on the aircraft,
designers can more optimally design structures and reduce weight
while maintaining safety, Richards explained. The net result could be
a reduction in fuel costs and an increase in range.

Further, intelligent flight control software technology now being
developed can incorporate structural monitoring data from the fiber
optic sensors to compensate for stresses on the airframe, helping
prevent situations that might otherwise result in a loss of flight
control.

By extension, the application of the technology to wind turbines could
improve their performance by making their blades more efficient.

"An improvement of only a few percent equals a huge economic benefit,"
Richards said. "The sensors could also be used to look at the stress
of structures, like bridges and dams, and possibilities extend to
potential biomedical uses as well. The applications of this
technology are mind-boggling."

NASA's Aeronautics Research Mission Directorate is supporting
algorithm and systems development, instrument and ground test
validation of the new sensor system. For more information on NASA's
aeronautics research, visit:

http://www.aeronautics.nasa.gov