At what angle of attack is the best lift to drag ratio observed?

The best lift-to-drag ratio is typically observed at a moderate angle of attack, often around 4 degrees. At this angle, the wing is sufficiently generating lift without incurring significant drag. As the angle of attack increases beyond this point, the drag begins to rise more steeply due to increased induced drag as well as potential onset of flow separation.

At lower angles, while drag is lower, the lift generated is often insufficient to maximize the lift-to-drag ratio. Therefore, 4 degrees represents a sweet spot where the aerodynamic forces are balanced effectively, leading to optimized performance. This is why this angle is critical for efficient flight, highlighting how important it is for pilots to understand and manage these aerodynamic principles for effective aircraft operation.