Many of us have noticed how a wing of some aircraft can flex upward. Most notable is the Boeing 787 which has a high wing flex angle. Well, there are reasons behind these wing flexes.
The Boeing 787's wings are made from carbon fiber material which allows more flexibility. This flexibility allows load changes and wind gusts to be dampened, resulting in an overall smoother, less turbulent ride for passengers.
A low wing pointing upward from the wing root to the wing tip is called Wing Dihedral.
The amount of dihedral determines the amount of inherent stability along the roll axis. Although an increase of dihedral will increase inherent stability, it will also decrease lift, increase drag, and decreased the axial roll rate. As roll stability is increased, an aircraft will naturally return to its original position if it is subject to a brief or slight roll displacement. Most large airliner wings are designed with dihedral.
On low-wing aircraft, the center of gravity is above the wing and roll stability is less pronounced. This factor requires the use of greater dihedral angles in low-wing airplanes.
On low-wing aircraft with wing dihedral, when a wing rolls downward, the relative wind on the descending wing becomes a component of the forward motion of the airplane and the downward motion of the wing. This produces a higher angle of attack on the descending wing and consequently more lift.
Sources:
- http://www.aviation-history.com/theory/wing_dihedral.htm
- https://simpleflying.com/boeing-787-wings-flex/
