Drucella Andersen
Headquarters, Washington, D.C.                                              
November 5, 1991
(Phone:  202/453-8613)

Don Haley
Ames-Dryden Flight Research Facility, Edwards, Calif. 
(Phone:  805/258-3456)


RELEASE:  91-183

PRESSURE-SENSITIVE PAINT PASSES TEST WITH FLYING COLORS


    NASA has successfully tested a new method to measure surface 
pressure on airplanes during flight that could replace the sensing 
devices traditionally used to gather such data.  Pressure 
measurements give engineers information on the strength of an 
aircraft's wings and tail, knowledge that lets them certify or 
improve the plane's design.

    The NASA tests used paint that becomes luminescent under 
ultraviolet light.  The intensity of the light radiated by the 
paint results from the pressure it receives in flight.  
Researchers use videotapes or photographs taken in ultraviolet 
light to study the pressure patterns.  

    Data from the research flights on an F-l04 aircraft at NASA's 
Ames-Dryden Flight Research Facility, Edwards, Calif., shows that 
"surface pressure measurements from the luminescent paint are 
comparable to those collected the conventional way," said Dr. 
Blair McLachlan, Project Scientist at NASA's Ames Research Center, 
Mountain View, Calif.  More laboratory work to improve the paint's 
characteristics will be done before the next series of flights.

     Aerospace experts hail the pressure-sensitive paint as 
revolutionary because it could lead to large areas of a test 
aircraft being studied at once.  The light pink paint is quick and 
easy to apply and the entire test surface can be "mapped."   An 
aircraft does not have to be modified with wires and tubing needed 
for a conventional data collection system, although video or photo 
cameras and ultraviolet light systems are required.


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     Surface pressure is normally measured with sensors and small 
openings that are part of a data collection system on the 
aircraft.  But this method produces data only from single, fixed 
points and the systems are expensive and time-consuming to 
install.  To measure large areas such as an entire wing, hundreds 
of sensors are needed and the pressure readings still do not 
represent 100 percent of the test surface.

     The luminescent paint test is based on a concept called 
oxygen quenching.  The paint "senses" the amount of oxygen on the 
surface and responds by varying the light it emits.  As surface 
pressure increases, the oxygen concentration also rises and the 
light emitted by the luminescent molecules decreases.  The 
resulting light pattern can be photographed and processed to 
produce a map of pressures across the test surface.

     The NASA F-104 carried the paint experiment in a 
belly-mounted flight test pylon where a video system recorded the 
pressure variations.  The paint was tested on three flights in a 
varied flight environment in which the plane reached nearly 1,200 
mph (1.6 times the speed of sound) and 30,000 feet.

     The luminescent paint development is a cooperative research 
program between the chemistry department at the University of 
Washington and the Fluid Mechanics Laboratory at Ames Research 
Center.  The effort began in 1987, followed by wind tunnel tests 
at Ames in 1989.

    Ames Research Center manages the project.  Lisa Bjarke is the 
Project Flight Test Engineer at Ames-Dryden.

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Note To Editors:  A photograph of computerized results from a 
luminescent paint test flight is available by calling 
202/453-8375.

Color: 91-HC-711            B&W: 91-H-810