Staying at or below which speed in 1 G flight will prevent Retreating Blade Stall?

Staying at or below which speed in 1 G flight will prevent Retreating Blade Stall?

• A. VNO
• B. VNE
• C. VFE
• D. VLE

Answer: (B)

Retreating blade stall happens when forward flight increases the angle of attack needed on the retreating blade to produce lift, and the rotor system can’t keep up with the demands, leading to a stalled blade on the retreating side. To avoid that aerodynamic limit, fly within the rotor’s safe operating envelope, which is defined by the never-exceed speed. Staying at or below this speed keeps the rotor in a regime where the lift distribution between advancing and retreating blades remains within design limits and the risk of retreating blade stall is minimized. The other speeds govern different aspects of the airframe (normal operating range, flap limits, gear limits) and don’t directly address the rotor aerodynamics responsible for retreating blade stall.

Retreating blade stall happens when forward flight increases the angle of attack needed on the retreating blade to produce lift, and the rotor system can’t keep up with the demands, leading to a stalled blade on the retreating side. To avoid that aerodynamic limit, fly within the rotor’s safe operating envelope, which is defined by the never-exceed speed. Staying at or below this speed keeps the rotor in a regime where the lift distribution between advancing and retreating blades remains within design limits and the risk of retreating blade stall is minimized. The other speeds govern different aspects of the airframe (normal operating range, flap limits, gear limits) and don’t directly address the rotor aerodynamics responsible for retreating blade stall.