If there is one thing we all dread when flying, it’s the invisible force of turbulence. What is turbulence, and is it really that scary? Let’s dive into it.
What is turbulence?
Turbulence is defined as the ‘irregular motion’ of the air from eddies and vertical airflows. It is different from wind that flows horizontally from different directions, a force that is easily measured by weather services. A turbulent flow can occur when the wind changes directions or a storm arrives at a locality. And, unlike wind, weather services can’t easily detect its presence, although items that create turbulence can be avoided.
There are three different turbulent eddies, affecting either a plane’s pitch (lateral axis), planes roll (longitudinal axis), or aircraft yaw (along the vertical axis).
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What causes turbulence?
There are four main ways that turbulence is created:
Mechanical Turbulence – where the terrain on the ground causes the wind to pool and form vertical eddies. A good example of this would be where the mountains meet the plains or oceans. The flat wind reaches the mountain range and has nowhere to go but up, hitting air traffic and changing direction as it cools. The worse case is hot desert wind (or the tropics) hitting big mountains.
Interestingly, human cities have started to get big enough for eddies to form over skyscrapers and other dense urban areas.
Thermal Turbulence – Heat has a huge impact on turbulence. When the sun heats the air, it starts to rise and cool. However, the sun doesn’t heat the air evenly, and different surfaces may generate more reflected heat than others (such as concrete vs. oceans). The hot air updrafts form pillars of turbulence that can affect aircraft coming to land and eventually form thunderstorms.
However, this type of turbulence is rarely found above the cloud layer. If an aircraft is flying over a region, then it is generally unaffected.
Frontal Turbulence – More common in winter, when a mass of cold air hits warm air, forming a ‘wave’ of wind that pushes all objects up and over. The eddies are formed laterally over the dome and can be very unstable. Once a plane traverses this barrier, then they are generally secure. If there is a thunderstorm in this environment, then the turbulence may be extreme.
Wind Shear Turbulence – The last type of turbulence is when the wind changes in the aircraft path. This can be when entering or exiting a jet stream, hitting a storm front, or crossing over-temperature differences. This type is found most commonly at the sunset barrier – when the sun dips over the horizon and is no longer heating the air, and the air starts to cool. This turbulence is generally horizontal until the thermal and frontal turbulence.
Clear Air turbulence – There is actually a fifth type of turbulence that is not generally categorized with storms or changing weather. Essentially this is where wind forms bends or eddies through its wave-like flow. The best way to describe this is to imagine a river, where the water going around a bend on the outside is much faster than the water on the inside. Clear air turbulence can occur with no visible signs and can be extreme.
How does it affect aircraft?
The above is all well and good if you are reading at home; however, those reading this in the air might like to know what it means for aircraft.
There are four types of turbulence:
- Light turbulence – slight bump, passengers sleep through it.
- Moderate turbulence – bigger bumps and passengers walking in the cabin might lose balance. The plane is under control.
- Severe turbulence – huge changes in altitude and airspeed. The aircraft falls out of control for a short time, and passengers are thrown throughout the cabin.
- Extreme turbulence – the aircraft loses control, and structural damage can occur.
Overall, turbulence is a relatively safe and natural occurrence. The worse turbulence cases occur closer to the ground, but pilots are well trained in handling the conditions. In situations where the plane rapidly loses altitude, the aircraft will descend to the point that the air changes and the pilots regain control (generally only for a few seconds). As always, it’s best to keep your seat belt on at all times.
What do you think? Have you ever flown through bad turbulence? Let us know in the comments.