Relative wind velocity on the retreating blade equals blade speed minus airspeed.

Relative wind velocity on the retreating blade equals blade speed minus airspeed.

• A. Minus Airspeed
• B. Plus Airspeed
• C. Times Airspeed
• D. Divided by Airspeed

Answer: (A)

The retreating blade’s relative wind is determined by two motions: the blade’s rotation through the air and the helicopter’s forward motion. On the retreating side, these two effects oppose each other, so the forward airspeed subtracts from the blade’s rotational speed. That means the relative wind seen by the retreating blade is blade speed minus airspeed. If forward speed increases, the retreating side sees less relative wind, while the advancing side sees more (blade speed plus airspeed), which creates dissymmetry of lift that the rotor system must balance. The other mathematical options don’t reflect this opposing-motion relationship.

The retreating blade’s relative wind is determined by two motions: the blade’s rotation through the air and the helicopter’s forward motion. On the retreating side, these two effects oppose each other, so the forward airspeed subtracts from the blade’s rotational speed. That means the relative wind seen by the retreating blade is blade speed minus airspeed. If forward speed increases, the retreating side sees less relative wind, while the advancing side sees more (blade speed plus airspeed), which creates dissymmetry of lift that the rotor system must balance. The other mathematical options don’t reflect this opposing-motion relationship.