Which term describes the flow of air produced by rotor rotation that is affected by induced flow?

Which term describes the flow of air produced by rotor rotation that is affected by induced flow?

• A. Resultant Relative Wind
• B. Relative Wind
• C. Induced Wind
• D. Rotor Wind

Answer: (A)

When a rotorcraft generates lift, air is diverted downward through the rotor disk, creating induced flow. The air that actually flows past a rotor blade element is not just the aircraft’s forward airspeed; it’s the combination of that forward (relative) wind with the downward induced flow, plus the blade’s own motion through the air. The resulting direction and speed of the air seen by the blade—the vector sum of these components—is called the resultant relative wind. This is the wind that the blade’s airfoil actually “feels,” and it governs the blade’s angle of attack and the lift produced. Other terms describe parts of this overall flow (for example, relative wind in general or induced wind for the downward component alone), but the flow that results from rotor rotation and is modified by induced flow is best described as the resultant relative wind.

When a rotorcraft generates lift, air is diverted downward through the rotor disk, creating induced flow. The air that actually flows past a rotor blade element is not just the aircraft’s forward airspeed; it’s the combination of that forward (relative) wind with the downward induced flow, plus the blade’s own motion through the air. The resulting direction and speed of the air seen by the blade—the vector sum of these components—is called the resultant relative wind. This is the wind that the blade’s airfoil actually “feels,” and it governs the blade’s angle of attack and the lift produced. Other terms describe parts of this overall flow (for example, relative wind in general or induced wind for the downward component alone), but the flow that results from rotor rotation and is modified by induced flow is best described as the resultant relative wind.