ME 363 Engineering Tools, Analysis, and Communication
When looking for the next best thing in aviation, sometimes it is important to look back at old ideas that have not been used yet. A forward-swept wing provides better lift to drag ratios, compared to a swept-back wing of the same area, higher lift to drag ratio; higher capacity in dogfight maneuvers; higher range at subsonic speed; improved stall resistance and anti-spin characteristics; improved stability at high angles of attack; a lower minimum flight speed; and a shorter take-off and landing distance. Comparing the only U.S. forward-swept wing jet (X-29A) to contemporary fighters, the X-29A outperforms them in angle of attack and lift to drag ratios. Forward Swept Wing Fighter Needed For US
A forward swept wing design has been tested and dismissed by the United States, though it just might be the right configuration for the next United States fighter aircraft. NASA tested the X-29, a forward-swept wing jet, back in the early 90’s and submitted their data, but a fighter aircraft was never produced. Over the years since then certain areas of engineering have advanced and are now up to the task of supporting an aircraft featuring a forward-swept wing. This forward-swept wing configuration gives several advantages to a fighter aircraft which could be the deciding factor of a dogfight. “In 1936, a German aerodynamicist first postulated developing an airplane with its wings swept forward, but nobody built any actual models at the time.”
Results and Discussion
“Interest in forward-swept wings increased when some wind-tunnel tests in 1931 showed that [pic]of forward sweep provided a greater useful angle-of-attack range than did a corresponding amount of aft sweep. Later, as airplane wings began to experience the effects of local shock waves, A. Busemann and R.T. Jones independently recommended sweepback as a means of reducing transonic and supersonic drag. It was only natural, then, to consider using forward sweep for high-performance aircraft, because forward sweep offered the dual benefits of reducing compressibility effects at transonic speeds and providing high-lift advantages at lower speeds.” The lift-to-drag ratio is higher on a forward-swept wing than on a regular wing and therefore gives you better fuel efficiencies at low speeds. At higher angles of attack maneuverability is higher on a forward-swept wing due to the direction of air flowing across the wings from root to tip. On a forward-swept wing surface stall occurs from the root of the wing out, versus the tip of the wing in like on a swept wing design. This allows the forward-swept wing to achieve slower speeds and use shorter runways for take off and landing. Most modern day fighter aircraft lose maneuverability input around an angle of attack of 40 degrees, though on a forward swept wing it is possible to achieve maneuverability at angles of attack close to 67 degrees. This is a huge leap in aerodynamic ability of fighter aircraft, which could be the difference of winning a dogfight. [pic]
Better lift-to-drag ratios, reducing compressibility factors at transonic speeds, and higher angles of attack are three innate characteristics of a forward-swept wing. “The airflow over a forward-swept wing is reversed; wingtip vortices never appear, as the air travels inward to the fuselage. This creates much more lift than a conventional wing, particularly when combined with canards as on the X-29.” (fig 1) To stablize a forward-swept wing most models and designs produced over the years have had canards. These small wings allow for more input surface and they don’t cause drag like the tail of an F-15 but rather lift.
There are some disadvantages that have been discovered with a forward-swept wing, unstable flight controls and wing strength (aeroelastically). With...