SIFT Army Aviation Information Practice Test

What type of drag is created by the vortices produced from spinning rotor blades?

1. Form drag

2. Rotational drag

3. Parasite drag

4. Induced drag

The correct answer is: Induced drag

Induced drag is primarily the result of lift generation by the rotor blades. When rotor blades spin, they create vortices at their tips, which are essentially spiraling air patterns that emerge from the high-pressure area beneath the blades to the low-pressure area above them. These vortices are an inherent part of the lift process and contribute to the overall drag experienced by the aircraft. Induced drag increases with an increase in angle of attack and is notably significant at lower speeds when lift is needed, as the vortices become stronger. As the angle of attack rises beyond a certain point, the lift-to-drag ratio diminishes, increasing induced drag. The understanding of induced drag is crucial for pilots and aviators as it greatly influences the performance and efficiency of rotorcraft during various flight conditions. Other types of drag, such as form drag and parasite drag, refer to different phenomena that do not relate specifically to the effect of lift-generating vortices produced by rotor blades. Form drag pertains to the shape of the aircraft and how air flows around it, whereas parasite drag involves the sum of all aerodynamic drag not associated with lift generation, including frictional forces. Rotational drag is not a commonly recognized term in aerodynamics, making induced drag the most appropriate