Rotor wash velocity is greatest at which gross weight condition?

• A. Low
• B. High
• C. Medium
• D. Very high

Answer: (B)

Rotor wash velocity reflects how fast air is pushed downward by the rotor to generate the lift needed to support the helicopter. In a hover, the rotor must produce thrust equal to the weight. Heavier weight requires more thrust, and with rotor speed and air density largely fixed, that extra thrust comes from a higher induced downward flow through the rotor. The result is a stronger downward air velocity, i.e., greater rotor wash. Among the given weight levels, the wash is greatest at higher gross weight because that condition demands the most thrust to hover. Lighter weights need less thrust and thus produce weaker downwash, and very high weight sits at the upper limit of hover capability, but within these options the strongest downwash is associated with high gross weight.