What is low speed mach buffet?

Answer 1

Low speed mach buffet is a term used in aviation to describe the buffet or vibration that occurs on an aircraft as it approaches the critical mach number at low speeds.

The critical mach number is the speed at which the airflow over the wings reaches the speed of sound, causing a shock wave to form and disrupt the airflow over the wings.

When an aircraft approaches the critical mach number at low speeds, such as during takeoff or landing, it may experience buffet or vibrations as the airflow becomes turbulent and begins to separate from the wings.

This can cause a decrease in lift and an increase in drag, making it more difficult for the aircraft to maintain control.

Pilots are trained to recognize and respond to low speed mach buffet by adjusting their speed and angle of attack to prevent the aircraft from entering an aerodynamic stall.

By understanding the effects of low speed mach buffet and how to mitigate them, pilots can safely operate aircraft at low speeds without compromising performance or safety.

Answer 2

There is no such thing as "low speed Mach buffet". It is sometimes confused with stall buffet. Mach buffet is caused by the local airspeed (such as air going around a nacelle or over a wing which is locally faster than the surounding air relative to the aircraft airspeed.) going above the speed of sound and hitting part of the airframe or another area of high speed air from the airframe or nacelle. It occurs usually above .75 Mach or so.

Stall buffet is caused by the wing losing lift due to travelling too slowly and requiring an angle of attack that is too high. Stall buffet can be higher airspeed if the aircraft is heavy or under "G" loads greater than 1, in effect requiring a higher angle of attack to maintain altitude.

At very high altitudes, it is possible for stall speed and Mach buffet speed to be the same. This is often referred to as the "coffin corner". This is generally at an altitude higher than most aircraft can climb to, so is only a factor in high performance fighters or reconaissance aircraft such as the U-2.

This is because Stall Speed is a factor of Calibrated Airspeed, which does not change much with altitude. As altitude is increased, the air density is lower so the aircraft must go faster to maintain a given Calibrated Altitude. True Airspeed ismuch faster at high altitude for a given Calibrated Altitude. Mach number is relatively constant with altitude andvaries with temperature, so the Stall Speed canhave a high True Airspeed at high altitude - and if one goes high enough the Stall Speed and the critical Mach number, where Mach buffet occurs, will be the same True Airspeed.

There is no such thing as "low speed mach buffet".

Answer 3

The previous answer is not correct. There are two types of Mach buffets.

Low speed mach buffet is due to AoA being increased at high altitudes causing the airflow over the wing to locally exceed the speed of sound creating a pressure wave that causes the following air flow to separate from the wing. This is a different type of stall than airflow separation due to slow speed.

High speed mach buffet is due to a part of the aircraft exceeding the speed of sound due to excessive speed. Whether or not the previous induvial recognizes "low speed mach buffet" the FAA test for ATM asks about it, so understand the difference between Low speed and high speed mach buffets and their causes.