Buffeting during cruise at normal speed can be caused by:

• A. Only low speed buffet
• B. Only high speed buffet
• C. Either low speed or high speed buffet and it may be difficult to identify
• D. Environmental turbulence only

Answer: (C)

Buffeting arises from unsteady airflow over the aircraft’s surfaces, causing vibrations you can feel through the airframe and controls. In cruise at normal speed, you can encounter two regimes that produce this effect. Low-speed buffet happens as the wing operates near its stall margin; as the angle of attack climbs, the airflow can separate and reattach irregularly, creating a rhythmic vibration. High-speed buffet, also known as transonic buffet, occurs at higher speeds when local flow reaches speeds approaching sound in parts of the wing, leading to shock waves and flow separation that destabilize the flow and generate buffeting. Depending on weight, altitude, configuration, and airspeed, either regime can occur during cruise, and the source isn’t always easy to distinguish by feel alone. So buffeting during cruise at normal speed can be caused by either low-speed or high-speed buffet, and it may be difficult to identify which one is at play.