Don Nolan-Proxmire
Headquarters, Washington, DC               October 8, 1996
(Phone:  202/358-1983)
Fred Brown
Dryden Flight Research Center, Edwards, CA
(Phone:  805/258-2663)
Catherine Watson
Langley Research Center, Hampton, VA
(Phone:  804/ 864-6122)
RELEASE:  96-201
FLIGHT EXPERIMENT SMOOTHES FLOW OVER SUPERSONIC WING
        In a series of flight tests, NASA engineers have 
smoothed the flow over the surface of an aircraft flying at 
supersonic speeds.  These tests will lead to the development 
of surfaces that will greatly restrict the drag of airborne 
airplanes and thus significantly reduce the cost of flying on 
commercial airlines.
       "Supersonic laminar flow control has been called the 
'holy grail' of aerodynamics, because it's the last frontier 
that can offer significant drag reductions and save airlines, 
and eventually the flying public, a great amount of money.  
This  brings to a successful conclusion a historic 
achievement in high-speed aerodynamics," said Jeffrey Lavell, 
project manager of the F-16XL Supersonic Laminar Flow Control 
(SLFC) experiment at NASAs Langley Research Center, Hampton, VA. 
        As an aircraft flies, the friction between the air 
and the wing creates drag, or resistance, called skin 
friction drag.  Skin friction drag accounts for about half of 
the total drag on an aircraft.  When airflow over the wing 
becomes turbulent and separates from the wing, skin friction 
drag increases.  Laminar flow, a condition where the airflow 
over the wings remains smooth and close to the wing, greatly 
reduces skin friction drag.  Smooth, or laminar, flow over a 
wing can reduce drag and contribute to reduced operating 
costs by improving fuel consumption and lowering aircraft weight.
           The objective of the flight tests, part of NASA's 
High-Speed Research (HSR) program, was to demonstrate that 
laminar flow could be achieved over a significant portion of 
a supersonic wing.  "We've had terrific results," Lavell 
said.  "We've obtained a large amount of data that can be 
used to refine our design codes and provide the U.S. aircraft 
industry with the means to design SLFC wings."
         This successful method of maintaining laminar flow 
could be incorporated into the design of a future High-Speed 
Civil Transport (HSCT), a conceptual supersonic airliner of 
the future that would carry 300 passengers at 2.4 times the 
speed of sound. 
         Flights with the SLFC experiment at NASA's Dryden 
Flight Research Center, Edwards, CA, used an F-16XL, which 
has a large delta wing.  The wing's shape is similar to the 
design that likely will be used on the HSCT, making the F-16XL
an excellent testbed for the laminar flow research project.
        A large, titanium panel, perforated with more than 
ten million laser-cut holes, was attached to the upper 
surface of the F-16XL's left wing.  Natural aerodynamic drag 
on an aircraft wing is caused by the friction of a thin 
turbulent layer of air moving across the wing's surface.  
During research flights, a suction system pulled a portion of 
that thin layer of air through the glove's porous surface to 
keep the airflow over the wing from becoming turbulent.
        Without any means of control, the flow over a highly-
swept supersonic wing is laminar for only a few inches.  By 
perforating the skin of the glove and providing suction 
through the perforations, the airflow can remain stable and 
laminar flow can be extended over most of the wing.
        NASA flew approximately 40 flights over a 12-month 
time span, and achieved "a significant amount of laminar 
flow," according to Lavell.  Most of the research flights 
were at speeds of Mach 2 (approximately 1,400 mph) and 
altitudes of 35,000 to 55,000 feet, which is close to the 
proposed range for the future HSCT. 
        The HSR SLFC experiment represents a collaborative 
effort between NASA and the U.S. aerospace industry.  A team 
composed of Boeing, Rockwell and McDonnell Douglas designed 
the wing panel and suction system.  The panel was assembled 
at a Boeing facility in Seattle, WA, while the suction system 
was fabricated by McDonnell Douglas, Long Beach, CA. 
NOTE TO EDITORS:  A laminar flow fact sheet (FS-1996-09-17-
LaRC), a graphic of the SLFC concept and video b-roll are 
available by calling Langley at (804) 864-6122.  Photos of 
the F-16XL aircraft are available by calling Dryden at (805) 
258-2665.  A photo also is available from the NASA 
Headquarters Imaging Branch at (202) 358-1900 (Color photo 
number: 96-HC-573, Black and White photo:  96-H-573).
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