Forward-swept wing

The forward-swept wing is a high-performance , first proposed in 1936 by a German aircraft designer.US Centennial of Flight Commission. [http://www.centennialofflight.gov/essay/Evolution_of_Technology/foward_sweep/Tech9.htm "Forward-Swept Wings".] Retrieved 22 August, 2005.] 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.

Military Use

Not until World War II did designs incorporating forward-swept wings appear; such as the experimental Junkers Ju 287 bomber. After war, the Soviet Union used Ju 287 as a base for OKB-1 EF 140 prototype. In 1948, the Soviet Union created the Tsybin's LL-3. [ [http://aeroweb.lucia.it/~agretch/RAFAQ/six5th_5.html Russian Aviation Page: Sukhoi S-37 Berkut (S-32)] ] The prototype subsequently had a great impact on Construction of Sukhoi's SYB-A in 1982, produced more than two years earlier than Grumman X-29 FSW demonstrator.huh|date=June 2008
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 concept continued to be dismissed as 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, the Grumman X-29 was chosen instead. [http://www.f-16.net/f-16_versions_article26.html F-16.net article about the F-16 SFW] ] 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.NASA. [http://www.nasa.gov/centers/dryden/news/FactSheets/FS-008-DFRC.html "Dryden Fact Sheet - X-29".] Retrieved 22 August, 2005.] 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.

The Northrop-Grumman YF-23 does not so much use a Forward-swept wing but a Diamond Wing which combines both, backwards and swept.

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.

Civilian use

Several civilian aircraft exist with wings exhibiting a slight forward sweep, including:

*The CZAW Parrot [ [http://www.airplane.cz/parrot.htm CZAW web site] ] )
*The HFB-320 business jet, of which 50 were built, first flew in 1964. The purpose of the forward-swept wing was to allow an unimpeded cabin without a large wing spar passing through it),
*The Saab Safari, a 1969 military trainer, used slightly forward-swept wings to increase visibility.
*The Scaled Composites Boomerang, a prototype piston twin design which would allow for safe handling in the event of a single engine failure. Only one exists as of 2007.
*The Cessna NGP, a prototype single-engine aircraft intended as the first in a family that will eventually replace the venerable Cessna 172 and Cessna 182, also uses a forward-swept wing.
*The Let Kunovice LET L-13 Blaník

Many high-wing training gliders with two seats in tandem have slightly forward-swept wings. This is to enable the wing root to be located further aft and therefore prevent the wing root from obscuring the rear occupant's sideways view. L-13 Blaník, one of most world successful training gliders, is typical example.

See also

* Swept wing
* Sweep theory
* Variable-sweep wing

References