Which statement is correct regarding flight at L/D max?

Flying at the lift-to-drag ratio maximum, commonly referred to as L/D max, signifies the most efficient flight condition regarding lift produced relative to drag experienced. When an aircraft is at this specific angle of attack, it is producing the maximum amount of lift for the least amount of drag, which means it is using its aerodynamic properties most effectively.

The statement about other angles of attack increasing total drag for a given lift is accurate because any deviation from L/D max leads to less efficient performance. If you increase the angle of attack beyond L/D max, the aircraft experiences induced drag due to the stall phenomenon, leading to a rapid increase in total drag while not generating proportionally more lift. Conversely, lowering the angle of attack reduces the airfoil's efficiency, causing an increase in drag relative to the lift generated.

Therefore, maintaining flight at the L/D max angle of attack ensures the aircraft operates at its most efficient point, maximizing the performance capabilities by minimizing drag relative to lift produced. This principle is essential for pilots to understand, especially during gliding and in scenarios requiring optimal fuel efficiency.