Certified Flight Instructor - Flight Instructor Airplane Practice Exam

What is the approximate lift/drag ratio at a 2° angle of attack compared to a 17.2° angle of attack?

1. 9.75° angle of attack

2. 10.5° angle of attack

3. 17.2° angle of attack

4. 20.0° angle of attack

The correct answer is: 17.2° angle of attack

The lift-to-drag ratio is a critical parameter in aerodynamics that varies with the angle of attack. At lower angles of attack, such as 2°, the aircraft generally experiences a relatively high lift-to-drag ratio due to efficient airflow over the wings and lower induced drag. As the angle of attack increases, like at 17.2°, the lift-to-drag ratio begins to decrease due to increased drag from flow separation and turbulence, which occur as the wings operate beyond their optimal angle of attack. By comparing these two angles, it is understood that while the lift-to-drag ratio at the lower angle (2°) is more favorable, the lift-to-drag ratio at the higher angle (17.2°) is less efficient due to the factors mentioned. Generally, the exact lift-to-drag ratios can be situation-specific and depend on the airfoil design, Reynolds numbers, and other aerodynamic considerations. Thus, interpreting the surrounding context of the question indicates that the approximate lift-to-drag ratio at 2° is indeed much higher than that at 17.2°. This understanding confirms that the greater angle (17.2°) reflects a benchmark for comparison, supporting choice C as the appropriate selection for understanding the relative aer