7/14/2008 - EDWARDS AFB, CA -- NASA is evaluating an advanced,
fiber optic-based sensing technology that could aid development
of active control of an aircraft's 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
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
"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."
Source: NASA Dryden Press Release