Summary and Key Points: The F-16 SFW (Forward-Swept Wing) was an experimental fighter developed by General Dynamics in the 1970s as part of DARPA’s Forward Swept Wing Program. Designed to reduce drag and improve low-speed handling, the F-16 SFW modified the conventional F-16 Falcon by adding forward-swept wings.

-However, in 1981, DARPA rejected the design in favor of Grumman’s X-29, a forward-swept wing aircraft made possible by advanced carbon composites.

-While the F-16 SFW never made it past the blueprint stage, the X-29’s 242 flights helped researchers understand aircraft control during extreme instability and the mechanics of aeroelastic tailoring.

The Rise and Fall of the F-16 SFW: A Forward-Swept Wing Fighter Lost to History

Meet the F-16 SFW: If you saw the new Godzilla Minus One film, you likely noticed the plane featured prominently in the film’s final sequence – a Kyushu J7W Shinden. The Shinden – a tailless aircraft with a backward-facing “pusher” propeller, rear-mounted wings with vertical stabilizers, and nose-mounted canards – subverts expectations. Only two Shinden prototypes were developed before the end of World War II interrupted the project. The aircraft design was resurrected eighty years later in Godzilla Minus One, to serve as a reminder that the conventions of aircraft design are somewhat arbitrary.

To be clear, the aerodynamic principles are not arbitrary. However, the aircraft designs that have become conventionally accepted as the best options for interacting with those aerodynamic principles are somewhat arbitrary. I’m referring to the single fuselage. Engines mounted in the nose or on the wings. More often than not a “T-shaped” tail that is constructed of a vertical stabilizer and two horizontal stabilizers.

Straight or backward sweeping wings. It’s a form we take for granted as to what an aircraft is supposed to look like. Boeing 737. Airbus A330. Cessna 172. P-51 Mustang. AV-8B Harrier. And seemingly only when the conventional form is subverted do we take notice. The flying wing design of the B-2 Spirit. The sweeping wings of the F-14 Tomcat. The double fuselage F-82 Twin Mustang. The forward-swept wings of two experimental designs: the F-16 SFW (which was rejected before being produced) and the Grumman X-29 (of which two prototypes were produced).

F-16 Forward Swept Wings

Forward-swept wings do have advantages. One, forward-swept wings produce low drag. And two, forward-swept wings improve handling characteristics at low speed. However, manufacturing forward-swept wings using conventional techniques can be difficult to achieve.

So, in the 1970s, the Defense Advanced Research Projects Agency (DARPA) awarded funds to General Dynamics, Rockwell, and Grumman – as part of the Forward Swept Wing Program – to solicit designs for a viable aircraft design featuring forward swept wings.

General Dynamics submitted a modified version of their then-new F-16 Falcon, the F-16 SFW.

“The engineers at General Dynamics studied several designs, including one with canards and an aft-mounted wing,” F-16.net reported. “The final design submitted to DARPA used the landing gear and most fuselage components of the traditional F-16, yet it had a slightly lengthened and strengthened fuselage to allow the forward-swept wing to be attached, since the new wing was slightly larger than the traditional wing.”

DARPA rejected the F-16 SFW, however, in 1981. Instead, DARPA opted for Grumman’s F-5 derivative, the Grumman 712, which was later designated the X-29.

“The decision was mainly a political one,” F-16.net reported, “as many thought that the test-scene at NASA was heavily dominated by General Dynamics’ F-16s.” 

Although, ironically, 16 percent of the Grumman X-29 would be comprised of F-16 components (specifically the control surface actuators and main landing gear).

After DARPA selected the X-29, all development on the F-16 SFW was halted. The novel F-16 was never produced, it never existed anywhere other than on some blueprints and in the imaginations of the jet’s designers. The X-29, however, was built.

F-16 SFW Becomes the Grumman X-29

Two Grumman X-29s were built. NASA and the USAF jointly flew the experimental forward-swept wing aircraft, which made its first flight in 1984.

The use of carbon fiber composites made the construction of the X-29 possible. The wings, which swept forward at more than 33 degrees, were partially built from a graphite epoxy – which was both strong enough, and light enough, to make the forward-swept wings possible.

In constructing the X-29’s forward-swept wings, special attention needed to be paid to aeroelastic divergence. Basically, in forward-swept wing designs, aerodynamic lift produces a twisting force that rotates the wing’s leading edge upward. The twisting force causes a higher angle of attack, which in turn further increases lift, which in turn further increases the twisting motion. The twisting effect, or aeroelastic divergence, can cause structural failure. To make a wing that was light enough to fly, but strong enough to handle the twisting effect, designers used a special laminate.

The X-29, in addition to the forward-swept wings, had a center of gravity that was well aft of the airplane’s aerodynamic center. The result was inherent instability. To compensate for the instability, the X-29 was outfitted with a fly-by-wire system that made 40 control corrections per second. The flight control system consisted of three redundant digital computers. Backing up the digital computers were still three more analog computers. The mass redundancy of the computer systems seems to underscore the idea that the X-29 was not flyable without computer inputs.

In all, the two X-29s flew 242 times between 1984 and 1991. The experiment is generally considered a success, leading to a better understanding of “aeroelastic tailoring to control structural divergence,” and aircraft control during extreme instability.

About the Author: Harrison Kass, Defense Expert 

Harrison Kass is a defense writer with over 1,000 articles published. An attorney, pilot, guitarist, and minor pro hockey player, Harrison joined the US Air Force as a Pilot Trainee but was medically discharged. Harrison holds a BA from Lake Forest College, a JD from the University of Oregon, and an MA from New York University. Harrison listens to Dokken.

Main Image via Lockheed Martin. Intext image is from Creative Commons.