NASA 

National Aeronautics and 

Facts

Space Administration 

Dryden Flight Research Center 

P.O. Box 273

Edwards, California 93523 

Voice 661-258-3449 

FAX 661-258-3566 

pao@dfrc.nasa.gov FS-1994-11-023-DFRC 

F-16XL Laminar Flow

Research Aircraft

Two F-16XL aircraft were used by the Dryden Flight Research Center, Edwards, CA, in a NASA-wide 

program to improve laminar airflow on aircraft flying at sustained supersonic speeds. It was the first program to 

look at laminar flow on swept wings at speeds representative of those at which a high speed civil transport 

might fly.

 Technological data from the program will be 

available for the development of future high-speed 

aircraft, including commercial transports. As such, 

it supported the NASA Office of Aero-Space 

Technology’s goal of reducing travel time to Asia 

and Europe by 50 percent within 20 years.

 The initial research phase of the program at 

Dryden was flown in a single-seat F-16XL-1. This 

aircraft was later used at Dryden in a sonic boom 

research project with the SR-71 and in a CrankedArrow Wing Aerodynamics Project (CAWAP) to 

test boundary layer pressures and distribution. In 

1997 Dryden replaced the aircraft’s analog flight 

control system with a digital system and planned to 

use the aircraft as a testbed for autonomous systems 

to be employed in spacecraft.

 The aircraft at Dryden subsequently used for the 

supersonic laminar flow program was the two-seat 

F-16XL-2, identical to its sistership except for the 

cockpit configuration. NASA's single-seat F-16XL flies over the Sierra Nevada 

Mountains of CA. NASA photo EC94-42885-1 

The two aircraft are the only F-16XL's built and were used by NASA because the unique delta wing design 

is representative of the type of wing that will probably be used on future supersonic cruise aircraft. 

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Laminar Flow 

Background

 A certain amount of air turbulence occurs on the 

surface of most aircraft wings, regardless of the 

shape and sizeof the wing. As air moves across an 

airfoil, it is changed by the frictional force between 

it and the airfoil’s surface from a laminar (smooth) 

flow at the forward area to a more turbulent flow 

toward the trailing edge. The “perfect” wing would 

demonstrate laminar airflow across the entire surface of the wing, with no sign of turbulence. This 

turbulence affects flying performance by increasing 

aerodynamic drag and fuel consumption.

Front of F-16XL-2 showing wings as 

modified for flight research. NASA photo 

EC95-43267-2 

Research by NASA to improve laminar flow dates 

back to around 1930 when NASA’s predecessor 

organization, the National Advisory Committee for 

Aeronautics (NACA), photographed airflow turbulence in the variable density tunnel at its Langley 

Research Center in Hampton, VA. Smoke was ejected 

into the air stream and photographed as it showed 

visual signs of turbulence (disturbed rather than 

streamlined flow) on the upper wing surfaces. Early 

research such as this led to the eventual elimination of 

protruding rivet heads and other construction and 

design features that could create turbulence on highspeed aircraft. 

Much laminar flow research is carried out with two 

basic types of experimental devices — active and 

passive — that are attached to the research aircraft’s 

wing. These devices are commonly called “gloves.”

 Active test sections contain tiny holes or slots 

through which most of the turbulent layer of air is 

siphoned off by an internal suction system built into 

the wing. This decreases drag and enhances aerodynamic lift by either eliminating the turbulent 

airflow or reducing its effect.

 Passive experimental devices also attach to or 

become a part of the research aircraft’s wing, but do 

not use a suction system to remove the turbulent air. 

Through careful contouring of the wing’s surface, 

some laminar flow can be achieved naturally.

 Both types of laminar flow devices obtain data from 

sensors and other instrumentation built into or attached to 

the wing to measure airflow characteristics (especially 

the region of transition from laminar to turbulent flow) 

and pressure distribution.

 Dryden has conducted laminar flow studies in past 

years with F-104, F-14, F-15, and F-111 high-performance aircraft, and also with a JetStar business-type 

aircraft. The projects with the F-16XL, however, were 

the first that sought to achieve a significant percentage of 

laminar flow over wings comparable to those of a high 

speed civil transport. These flight tests were conducted 

under supersonic flight conditions similar to those such a 

transport would encounter. 

Flight Research

 The initial flight test phase of the Dryden Supersonic 

Laminar Flow Control project (SLFC) examined the 

performance of an active experimental wing section on 

the upper surface of the left wing of the single-seat F16XL-1. The 1991-1992 tests showed that with active 

laminar flow control, the aircraft achieved laminar flow 

over a significant portion of the wing during supersonic 

flight, although it did not obtain laminar flow on the 

active glove at the design point of Mach 1.6 (1.6 times 

the speed of sound) at 44,000 ft. The experimental glove 

with active (perforated titanium) and passive sections 

was designed by Rockwell International’s North American Aircraft Division, El Segundo, CA. (now a division 

of Boeing) 

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 Dryden then used the two-seat F-16XL-2 to conduct a 

more comprehensive research effort, consisting of two 

phases. The first phase used a passive glove on the right 

wing to obtain baseline configuration data that served in 

the design of the active glove, which was installed over a 

portion of the left wing. This effort was far more comprehensive than the initial flight phase, and explored 

regions of transition and the maximum extent of laminar 

flow obtained over a wider range of supersonic Mach 

numbers.

 The glove covered about 75 percent of the upper wing 

surface and 60 percent of the wing’s leading edge. It was 

designed by a NASA and contractor team which included the Langley Research Center, Dryden, Rockwell 

International, Boeing, and McDonnell Douglas. It 

featured a titanium suction panel and a foam-and-fiberglass passive fairing. The device was instrumented to 

measure laminar flow and other variables such as surface 

imperfections and the acoustic environment that may 

affect laminar flow at various flight conditions.

 The metal surface of the experimental wing panel 

was perforated with about 10 million nearly microscopic laser-cut holes. Through the tiny holes, a 

suction system embedded in the wing (and mechanized by a turbocompressor in the fuselage) drew off 

a very small portion of the boundary layer of air just 

above the wing’s surface, thereby expanding the 

laminar flow across the wing. The flight engineer 

used a control panel located in the aft cockpit of the 

airplane to fine-tune the amount of airflow sucked 

through the holes. This procedure permitted investigation of the effect of suction volume on the area distribution of laminar flow. Researchers believe that 

laminar flow conditions can reduce aerodynamic drag 

(friction) and help reduce operating costs by reducing 

fuel consumption. 

F-16XL single-place aircraft with the SLFC glove installed

F-16XL ship 2 with glove. 

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 The project flew the F-16XL-2 45 times between 

Oct.13, 1995, and Nov. 26, 1996, obtaining significant 

amounts of valuable flight research data. NASA research 

pilot Dana Purifoy flew 38 of the missions, with NASA 

research pilot Mark Stucky flying the other 7. During the 

flights, there were few problems with the experimental 

suction hardware. Because all laminar-flow-related data 

are restricted, however, the results of the flight research 

cannot be reported publicly at this time. 

Project Management

 The F-16XL flight project office was located at the 

NASA Dryden Flight Research Center, Edwards, CA. 

The NASA Langley Research Center, developed and 

coordinated F-16XL experiments. Project managers at 

Dryden were Marta Bohn-Meyer and Carol Reukauf.

 Aircraft Specifications

 The F-16XL aircraft were built by General Dynamics 

Corp., at Ft. Worth, TX, as prototypes for a derivative 

fighter evaluation program conducted by the U. S. Air 

Force between 1982 and 1985.

 The aircraft were developed from basic F-16 airframes, with the most notable difference being the delta 

(cranked arrow) wing, which give the aircraft a greater 

range because of increased fuel capacity in the wing 

tanks and a larger load capability due to increased wing 

area.

 Crew size: F-16XL-2, used in the second phase of the 

laminar flow project, has a two-seat cockpit. 

F-16XL-1, used in the 1991-1992 tests, is a single-seat 

aircraft.

 Size: Length, 54.2 ft (16.52 m); wingspan, 34.3 ft 

(10.45 m); height at vertical tail, 17.7 ft (5.39 m).

 Max. weight: 48,000 lb (17,915.60 kg)

 Engines: The two-seat aircraft at NASA Dryden has a 

General Electric F110-GE-129 engine (with afterburner) 

rated at 29,000 lb thrust. The single-seat F-16XL is 

powered by a Pratt and Whitney 100-PW-100 engine 

(with afterburner), rated at 23,830 lb thrust. 

Controls: Both aircraft featured an analog fly-by-wire 

electronic flight control system during the laminar flow 

research. The single-seat aircraft now has a digital flight 

control system.

 Wing construction: The delta (cranked arrow) wings 

on both aircraft are manufactured of advanced graphite 

composites to provide strength for high wing loads 

during flight.

 Design load: Baseline F-16XL: 9 “Gs”. Modified F16XL: 3 “Gs”)

 Maximum Speed: F-16XL-2, Mach 2 (approx. 1,400 

mph) (2,253 k/hr); F-16XL-1, Mach 1.8 (approx. 1,260 

mph)

 Range: Over 2,500 nautical miles (4,630 k), without 

in-flight refueling, and unlimited with in-flight refueling 

Three-view of F-16XL-2.

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