Contrary to popular belief, turbulence is not an air gap but an irregular movement of the atmosphere. The irregularities that occur in the normal airflow in the atmosphere are called turbulence. Turbulence occurs when invisible airwaves moving at a certain speed encounter another air mass moving at a different speed.
As the planes pass through turbulence, they shake, move up and down, deviates from their course, accelerates or slow down according to the intensity of the turbulence. Turbulence can cause structural damage to the aircraft. It can also cause an aircraft engine stall, although less common. May cause harm to passengers and crew.
Classification of Turbulence
1-Thermal (Convective) Turbulence
Thermal or Convective turbulence occurs as a result of the heating of the air parcel from the bottom. Localized convective currents occur as a result of the warming of the ground surface or the movement of cold air over the hot ground surface. Convective currents are called the locally vertical downward and upward movements of the air in certain regions. These convective currents also cause thermal turbulence.
2- Mechanical Turbulence
Mechanical turbulence is the name given to turbulence that occurs when the wind is forced to flow over or around a natural or man-made obstacle. Buildings, trees, cliffs, and large uneven terrain block the direction of the wind and prevent the wind from flowing smoothly. Mechanical turbulence depends on the speed of the wind and the roughness of the obstacles. As the wind speed increases, the turbulence intensity increases. Similarly, the greater the roughness of the obstacle, the greater the intensity of the turbulence.
3- Wake Turbulence
When an airplane takes off, it gains speed by pushing a certain amount of air mass down. Thus, as the wings rise, they cause the air to swirl under the wings or swirl around the wingtips. Since the landing gear carries the entire weight of the aircraft, eddies do not form on the wingtips during landing. However, as soon as the pilot activates the aircraft’s control gear for landing, these vortices begin to form again. This turbulence created by planes in the layers of atmosphere they pass through is called Wake turbulence.
4- Clear Air Turbulence
CAT is defined as sudden severe turbulence that occurs in cloudless areas and causes aircraft to crash violently. This turbulence occurs in cirrus clouds, in and around standing lenticular clouds, and in some cases near thunderstorms. Mostly seen at high altitudes.
It can be defined as sudden changes in wind speed or direction, or both, between two specific points in the atmosphere. This change can be horizontal or vertical. This meteorological event; always poses a risk for flights in the areas where it occurs. Especially low-level shear (Low-Level Wind Shear) poses a danger to aircraft on landing, take-off, and along the runway. Shear occurring at these points; on the descent, energy gain or loss, sudden altitude changes, runway miss. During take-off, very sudden altitude changes can cause energy loss and take-off difficulties.