Which main helicopter force acts perpendicular to the relative wind?

Which main helicopter force acts perpendicular to the relative wind?

• A. Lift
• B. Weight
• C. Drag
• D. Thrust

Answer: (A)

Lift is the force that acts perpendicular to the relative wind. The relative wind is the airflow seen by the rotor blades as they move through the air; the blade airfoil generates lift by deflecting that air downward, which creates an upward force on the blade that is at right angles to the incoming air. This orientation remains true even as the helicopter changes speed or attitude, because lift is defined as perpendicular to the relative wind. In contrast, weight acts straight downward due to gravity, drag runs parallel to the relative wind as it resists the motion through air, and thrust is produced along the rotor shaft and does not have to be perpendicular to the relative wind. Therefore, the main helicopter force perpendicular to the relative wind is lift.

Lift is the force that acts perpendicular to the relative wind. The relative wind is the airflow seen by the rotor blades as they move through the air; the blade airfoil generates lift by deflecting that air downward, which creates an upward force on the blade that is at right angles to the incoming air. This orientation remains true even as the helicopter changes speed or attitude, because lift is defined as perpendicular to the relative wind. In contrast, weight acts straight downward due to gravity, drag runs parallel to the relative wind as it resists the motion through air, and thrust is produced along the rotor shaft and does not have to be perpendicular to the relative wind. Therefore, the main helicopter force perpendicular to the relative wind is lift.