Which statement correctly identifies Mcr and Vs?

• A. Mcr stands for Critical Mach Number; Vs stands for Stall Speed
• B. Mcr stands for Maximum Cruise Radius; Vs stands for Vertical speed
• C. Mcr stands for Mach Constant Ratio; Vs stands for Velocity stability
• D. Mcr stands for Mean Cargo Ratio; Vs stands for Visual speed

Answer: (A)

In aerodynamics, Mcr refers to the Critical Mach Number—the lowest speed at which air flowing over some part of the aircraft reaches Mach 1, signaling the onset of significant compressibility effects and a rapid rise in drag as you fly into the transonic region. Vs is Stall Speed—the minimum steady speed at which the aircraft can maintain level flight in a given weight, configuration, and altitude, below which the wing cannot generate enough lift to support the aircraft. This pairing is the standard way pilots think about speed limits and safe handling: Mcr warns you about approaching transonic drag, while Vs tells you the slowest speed you can fly without stalling. The other phrases listed don’t correspond to conventional flight terms, so they don’t describe these concepts.