Aeronautical Engineering/aeroplane design
Good day sir,I am a class 12 student.I want to know about the designing of the planes having forward swept wings like Sukhoi-47.
Erick - Forward swept wing aircraft are rare because of the problem of structural divergence at high angle of attack and high speed. As the angle of attack increases, the wing twists in such a way to increase angle of attack, which is an unstable condition that can lead to structural failure. Aft swept wings don't have that problem. On the other hand, a forward swept wing will stall at the root before the tip which allows the ailerons to keep working unlike an aft swept wing. But the root carries a high load, so stall can be more rapid. A forward swept wing aircraft will have a strong yaw sensitivity because the downwind wing sees less sweep and more drag in yaw. With the aerodynamic center ahead of the center of gravity, a forward swept wing is statically unstable. That is - any increase in lift will cause a moment in the direction of stall. This may also be true with other designs, but it is aggravated by the forward swept wing. However, the aircraft can be very maneuverable. Actually, there are pros and cons to each design concept so I can't say a forward swept wing is always undesirable. It might be the best thing for a given mission, especially if the structural problem can be solved using new composite materials and the instabilities can be controlled using computer aided control systems.
Do a google search on forward swept wing for more information.