What type of airfoil is commonly used in rotor blades?

• A. Symmetrical
• B. Non-symmetrical
• C. Variable camber
• D. Bernoulli lift

Answer: (B)

The correct answer highlights that non-symmetrical airfoils are commonly used in rotor blades due to their aerodynamic performance characteristics. Non-symmetrical airfoils are designed with a camber, meaning that the upper surface is curved more than the lower surface. This design enables these airfoils to produce a significant amount of lift at lower speeds and angles of attack, which is essential in rotorcraft applications where maximizing lift is crucial for effective hovering, takeoff, and maneuverability.

In contrast, while symmetrical airfoils can provide lift, they do so primarily when moving at higher speeds or with a greater angle of attack. This limits their effectiveness in rotor applications where dynamic conditions often vary widely. Variable camber airfoils, while sophisticated, are not standard in rotor blade design as they introduce complexity and weight that could compromise the efficiency. Bernoulli lift is a principle explaining how lift is generated, but it does not categorize the type of airfoil. Therefore, the use of non-symmetrical airfoils is a well-established practice in the design of rotor blades, allowing for superior performance in various flight conditions.