SIFT Army Aviation Information Practice Test

What is true about induced drag on a helicopter?

1. It is strongest at higher speeds

2. It is created by the airfoil striking the air

3. It always pushes in a direction opposite of lift

4. All of the above are true

The correct answer is: It always pushes in a direction opposite of lift

Induced drag is a crucial concept in aerodynamics, particularly in helicopters. When analyzing induced drag, it is essential to understand its relationship with lift. Induced drag, by definition, is a type of drag that occurs as a result of lift being generated. As a helicopter generates lift, it creates a downward motion of air, which induces a reaction in the airfoil that leads to drag. The correct assertion about induced drag is that it always pushes in a direction opposite of lift. This is true because induced drag arises due to the vertical component of the airflow being altered as lift is produced. The drag is proportional to the amount of lift generated; thus, it naturally acts in opposition to the lift vector, effectively working against the upward force produced by the rotor blades. The other choices do not accurately represent the nature of induced drag. Induced drag is not strongest at higher speeds; in fact, it typically decreases as speed increases. This is because as a helicopter moves faster, it requires less angle of attack to produce the same amount of lift, thus reducing induced drag. The statement about induced drag being created "by the airfoil striking the air" misrepresents the phenomenon, as induced drag is a result of the airfoil creating lift and