Certified Flight Instructor - Flight Instructor Airplane Practice Exam

At what angle of attack is the lift/drag approximately the same as at 2° angle of attack?

1. 9.75° angle of attack

2. 10.5° angle of attack

3. 17.2° angle of attack

4. 15.0° angle of attack

The correct answer is: 17.2° angle of attack

The relationship between angle of attack and the lift-to-drag ratio is critical in understanding aircraft performance. Typically, as the angle of attack increases, both lift and drag also increase, but they do not do so at the same rate. At low angles of attack, such as 2°, the lift-to-drag ratio is relatively high because the aircraft is operating in a more efficient portion of its lift curve. As the angle of attack increases, there comes a point where the lift starts to increase significantly while the drag begins to increase more rapidly, causing the lift-to-drag ratio to drop. To find an angle of attack where the lift-to-drag ratio becomes comparable to that at 2°, you normally look for a higher angle of attack, usually around where the aerodynamic characteristics begin to stabilize again after the initial increase in drag. In this case, 17.2° is identified as the point where the lift-to-drag ratio matches that of the 2° angle of attack. This is generally above the critical angle but falls into a range where the aircraft can still produce adequate lift for its drag, making it a transition point rather than a peak. Understanding this relationship helps pilots recognize that at higher angles of attack, efficient flight