For Release: Oct. 8, 1996
Headquarters, Washington, D.C.
Dryden Flight Research Center, Edwards, Calif.
Langley Research Center, Hampton, Va.
Flight Experiment Smoothes Flow Over Supersonic Wings
In a series of flight tests, NASA engineers have smoothed the
flow over the surface of an F-16XL wing flying at
supersonic speeds (faster than sound), bringing to a successful
conclusion a historic achievement in high-speed aerodynamics.
"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," said Jeffrey Lavell,
project manager of the F-16XL Supersonic Laminar Flow Control
(SLFC) experiment at NASA 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
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 US aircraft
industry with the means to design SLFC wings."
Lavell said that the project's objectives were met, although
exact details of the amount of laminar flow achieved and with what
amount of suction is restricted information. The US aircraft
manufacturers may compete with aircraft manufacturers from other
countries someday, and SLFC technology could create a considerable
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 Dryden Flight Research
Center, Edwards, Calif., 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 10 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
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 twelve-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 US 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, Wash., while the suction system was fabricated by
McDonnell Douglas in Long Beach, Calif.
NOTE TO EDITORS: A laminar flow fact sheet, a graphic
of the SLFC concept and video b-roll are available by calling NASA
Langley Research Center at (757) 864-6122. Photos of the F-16XL
aircraft are available by calling NASA Dryden Flight Research
Center at (805) 258-2665.
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