Definition
An aerodynamic vibration of the airframe caused by airflow separation behind shock waves that form on the wing as the aircraft approaches its critical Mach number. As local airflow over portions of the wing reaches the speed of sound, shock waves develop and disturb the airflow behind them, producing a shaking felt through the airframe.
Plain English
A shaking of the aircraft that happens when it flies fast enough for the air over its wings to reach the speed of sound. The disturbed airflow behind the resulting shock waves makes the airframe vibrate.
Context Anchor
Seen in high-speed flight and Mach buffet boundary discussions, especially when comparing altitude, airplane weight, and speed limits.
Derivation
Buffet comes from an Old French word meaning to strike or knock about. The term captures the feel of the phenomenon: the aircraft is being knocked around by disturbed air, in this case at high speed rather than from turbulence or a stall.
Why Pilots Care
It serves as an early warning that the aircraft is nearing a speed where controllability may decrease and structural loads can rise sharply, prompting the pilot to reduce speed or descend.
Grounding Statement
Picture a high-flying airplane near its speed limit: a small increase in speed can disturb the airflow enough for the airplane to start shaking.
Intuition Check
Buffet here does not mean a meal. In aviation, buffet means shaking caused by disturbed airflow striking the airplane.
Example Sentence 1
Climbing into the thin air at FL410, the crew slowed slightly after feeling the first hint of high-speed buffet.
Example Sentence 2
The instructor pointed out that high-speed buffet appears before the aircraft reaches its critical Mach limit.