Mach Buffet occurs when the airplane goes faster than which, causing a shock wave and boundary layer separation that can produce buffet?

• A. The aircraft stalls due to ice.
• B. No buffet occurs at any speed.
• C. When the airplane goes faster than the critical Mach number, a shock wave forms and control surface buffet may occur.
• D. It is caused by tailplane flutter at high altitude.

Answer: (C)

Mach buffet is a transonic phenomenon that occurs when the aircraft exceeds the critical Mach number. At this speed, parts of the airflow over the wing reach sonic conditions, forming a shock wave. That shock creates a sharp pressure rise and an adverse pressure gradient, which can cause the boundary layer to separate. The resulting flow instability on the wing and around control surfaces leads to buffet. This is not about ice-induced stall, nor is it true that buffet cannot occur at any speed; and tailplane flutter is a different aeroelastic issue, not the classic Mach buffet described here.