Aero Fact: Critical Mach Number
The lowest free-stream Mach at which local airflow first reaches sonic speed on the airframe.
By AircoreDynamics •
•
1 min read
Definition: Free-stream Mach where local airflow first becomes sonic on the airframe.
Physics insight: Shock waves and compressibility; airfoil thickness and nose curvature are key.
Example: As Mcrit is approached, wave drag and buffet rise; operational limit MMO < Mcrit.
Wave-drag increment grows rapidly; sweep and thinner airfoils raise Mcrit.
Rules of thumb: Increase speed in small steps; monitor vibration/buffet cues.
Common pitfalls: Wet/contaminated wing can lower Mcrit.
References: Whitford; Anderson