Forward-swept wing
From Wikipedia, the free encyclopedia
The forward-swept wing is a high-performance aircraft configuration, first proposed in 1936 by a German aircraft designer.[1] Perceived benefits of a forward-swept wing design include
- mounting the wings further back on the fuselage, allowing for an unobstructed cabin or bomb bay, and
- increased maneuverability at transonic speeds, due to airflow from wing tip to wing root preventing a stall of the wing tips and ailerons at high angle of attack.
Not until World War II did designs incorporating forward-swept wings appear; such as the experimental Junkers Ju 287 bomber.
NACA, the precursor to the United States' NASA, researched the advantages of forward-swept wings on the Bell X-1, but encountered structural problems with twisting wingtips. Stronger materials were needed, and the aerodynamic benefits seemed minimal or nonexistent. The only production aircraft with forward-swept wings, the HFB-320 business jet, flew in 1964. Fifty were built; the purpose of the forward swept wing was to allow an unimpeded cabin without a large wing spar passing through it.
The concept was considered highly impractical until the late 1970s, when DARPA began investigating the use of newer composite materials to strengthen the wings; fly-by-wire technology allowed for the design to be dynamically unstable and therefore highly maneuverable. Originally, the F-16 SFW (swept forward wing) was to be the platform for this project, but for mainly political reasons, the Grumman X-29, which used about 16% F-16 components (including the fly-by-wire system), was chosen instead.[2] Grumman built two X-29 technology demonstrators, first flying in 1984, with forward swept wings and canards. The spanwise flow over a forward-swept wing is reversed. Forward swept wings still generate wingtip vortices as the high pressure air wraps around the wingtip toward the lower pressure air above. Maneuverable at high angles of attack, the X-29 remained controllable at 67° of pitch.[3] Advances in thrust vectoring technology and a shift in air combat tactics toward medium range missile engagements decreased the relevance of the forward swept wing.
In 1997, Sukhoi introduced the Su-47 fighter prototype at the Paris Air Show. It has not yet entered production, although it underwent a series of flight tests and performed at several air shows.
[edit] References
- ^ US Centennial of Flight Commission. "Forward-Swept Wings". Retrieved 22 August, 2005.
- ^ F-16.net article about the F-16 SFW
- ^ NASA. "Dryden Fact Sheet - X-29". Retrieved 22 August, 2005.
