Define rotational relative wind as applied to an airfoil.

Define rotational relative wind as applied to an airfoil.

• A. Flow of air perpendicular to the flight path
• B. Flow along the chord line
• C. Flow of air parallel to and opposite the flight path
• D. Flow around the leading edge

Answer: (C)

Rotational relative wind is the air flow that the airfoil experiences due to its motion through the air, specifically the part caused by the blade’s rotation. The air moves past the airfoil opposite to the airfoil’s velocity through the air. In other words, the resultant relative wind is directed opposite to the flight path, effectively parallel to that path. The angle between this relative wind and the airfoil’s chord line defines the angle of attack, which governs lift. This description aligns with the idea that relative wind is always opposite the direction of motion through the air.

Rotational relative wind is the air flow that the airfoil experiences due to its motion through the air, specifically the part caused by the blade’s rotation. The air moves past the airfoil opposite to the airfoil’s velocity through the air. In other words, the resultant relative wind is directed opposite to the flight path, effectively parallel to that path. The angle between this relative wind and the airfoil’s chord line defines the angle of attack, which governs lift. This description aligns with the idea that relative wind is always opposite the direction of motion through the air.