The International Civil Aviation Organization (ICAO) categorizes turbulence based on the intensity of its impact on both aircraft and passengers.
| Intensity | Description | Impact on Aircraft and Passengers |
|---|---|---|
| Light | Causes slight, erratic altitude and attitude changes. | Passengers feel minor strain against seat belts; unsecured objects may move. |
| Moderate | More pronounced changes in altitude and attitude, but aircraft remains controllable. | Passengers feel more definite strain; unsecured objects can shift; walking is hard. |
| Severe | Large, abrupt altitude and attitude changes; potentially momentary loss of control. | Passengers are thrown against seat belts; unsecured items can become airborne. |
| Extreme | Aircraft is tossed about violently; nearly impossible to control. | Possible structural damage; severe injuries if passengers aren’t securely fastened. |
| Clear Air | Occurs without visual indicators, often near jet streams and shear zones. Invisible and tricky to predict. | Technology like Doppler LIDAR helps in detection, aiding forecasting and safety practices. |
Types of Turbulence
Mechanical Turbulence
Mechanical turbulence happens when airflow is obstructed by surface features like mountains, buildings, or trees.
This type of turbulence typically occurs during takeoff or landing when the aircraft is close to the ground.
Pilots anticipate it in areas with significant topographical features or urban environments.
For instance, at London Heathrow Airport, large buildings can cause planes to deviate slightly before landing. Observations from live stream shows such as Big Jet TV illustrate this well.
Mountain Wave Turbulence
Similar to mechanical turbulence, mountain wave turbulence occurs when stable air flows over mountain ranges, creating waves that can extend miles.
This type of turbulence can affect planes flying at cruise altitudes and can be very severe.
Pilots are trained to recognize and navigate around these waves, identifiable by cloud formations like lenticular clouds.
One notable incident involved BOAC Flight 911 in 1966, which broke apart over Mount Fuji due to extreme turbulence, resulting in the loss of all passengers and crew.
Thermal Turbulence
Also known as convective turbulence, thermal turbulence is caused by uneven heating of the Earth’s surface.
Warm air rises, creating thermals that can lead to turbulence, especially during the early afternoon when the sun’s heat is strongest.
Pilots encounter thermal turbulence frequently over varying terrain and during the summer.
Glider pilots use thermals to gain altitude but must manage the resulting turbulence. Identifying cumulus clouds can help spot these rising air pockets.
Wake Turbulence
Generated by the passage of an aircraft, wake turbulence involves dangerous wingtip vortices, especially hazardous to smaller planes following larger ones during takeoff and landing.
Air traffic controllers use separation standards to mitigate these risks, ensuring safe distances between aircraft.
Radar Distance Separation
Radar distance separation involves using radar systems to maintain safe distances between aircraft to prevent wake turbulence, especially in high-traffic areas.
The separation standards dictated by air traffic controllers are crucial for efficient and safe air traffic management.
Ensuring appropriate spacing between aircraft minimizes the turbulence impact on trailing aircraft, providing a smoother and safer flying experience.
Time Separation
Time separation is another effective safety measure in aviation.
This involves scheduling takeoffs and landings to ensure sufficient time gaps between aircraft.
This method is especially important for preventing wake turbulence, where larger aircraft can create dangerous air disturbances for following smaller planes.
By implementing precise time separation, air traffic controllers reduce the risks associated with closely spaced aircraft.
Impact of Turbulence on Aircraft
Turbulence can have various effects on aircraft, from minor inconveniences to severe safety threats.
In light turbulence, passengers may experience light strain against seat belts and slight disturbances of unsecured objects.
Moderate turbulence escalates these effects, making walking difficult and causing more pronounced discomfort.
Severe turbulence can momentarily throw the aircraft out of control, forcing passengers violently against seat belts and making walking impossible, with unsecured items becoming airborne.
Extreme turbulence poses even greater risks, with potential structural damage to the aircraft and severe injuries to those not securely fastened.
Clear air turbulence, though invisible and often unexpected, adds an additional challenge. It highlights the critical need for advanced detection technology, such as Doppler LIDAR, to improve forecasting and safety measures.
Wasn’t aware of the different types of turbulence. Good to learn something new. Thanks, Ben Croom for explaining it simply.