Editing Lift-to-drag ratio (section)

===Lift and drag coefficients===
The rates of change of lift and drag with angle of attack (AoA) are called respectively the [[lift coefficient|lift]] and [[drag coefficient]]s C<sub>L</sub> and C<sub>D</sub>. The varying ratio of lift to drag with AoA is often plotted in terms of these coefficients.

For any given value of lift, the AoA varies with speed. Graphs of C<sub>L</sub> and C<sub>D</sub> vs. speed are referred to as [[drag curve]]s. Speed is shown increasing from left to right. The lift/drag ratio is given by the slope from the origin to some point on the curve and so the maximum L/D ratio does not occur at the point of least drag coefficient, the leftmost point. Instead, it occurs at a slightly greater speed.  Designers will typically select a wing design which produces an L/D peak at the chosen [[cruising speed]] for a powered fixed-wing aircraft, thereby maximizing economy. Like all things in [[aeronautical engineering]], the lift-to-drag ratio is not the only consideration for wing design. Performance at a high angle of attack and a gentle [[Stall (flight)|stall]] are also important.