Why is there often a slight shake when flying through clouds?

Turbulence in aviation is an everyday occurrence that rarely causes any problems. An airplane can shake at any stage of flight, but when crossing clouds, turbulence seems almost guaranteed. So why is it that an airplane going through cloud cover is almost always at least a little shaky?

As always, articles like this should remind us that air travel is safe. Yes, turbulence can scare you, especially if you have a fear of flying or are not an experienced traveler. But it’s completely normal — every passenger on any airplane experiences turbulence, whether it’s weaker or stronger. Airplanes are designed to withstand such stresses, and have been doing so for decades. Just unbuckle your seat belt and watch out the window as the wing moves elegantly, cushioning the flight. If you’re not flying anywhere yet, you can practice the aviator crash game from 1win.

Why do airplanes shake when flying through clouds?

First of all, let’s agree on concepts. Turbulence is not the shaking or jiggling of an airplane. Turbulence is the disorderly motion of liquids or gases. In other words, turbulence is what happens to the air, not what happens to the airplane. You can observe turbulence in a river or when you pour water into a glass. In air, it is simply mixing, spinning and diverting currents. Remember that the Earth’s atmosphere is layered, so to speak, and there are many different processes going on — warm and cold fronts colliding, larger and smaller vortices, convection, and so on. Commercial aviation knows how to exploit some of these processes, which is why eastbound flights tend to be shorter than westbound flights.

Clouds are clusters of water droplets and sometimes small ice crystals suspended in the air. Parents often explain to their children that clouds are made up of vapor, which is not entirely true. Clouds are made up of liquid water, it’s just that the particles are so small that they don’t fall until they coalesce into larger ones. Water vapor has a lower density than most of the rest of the atmosphere, so it rises where it condenses into the clouds you see. This usually happens at altitudes where the air temperature is at or below the dew point.

So why does an airplane often experience turbulence when flying through clouds? The short answer is that clouds often mix and rotate in a variety of ways.

Clouds are rarely smooth and orderly. They have discontinuities, denser and thinner areas. These changes in density affect the lift force generated by the wings and the air resistance the airplane encounters — because one second the airplane is flying through drier air and the next second it is flying through airborne water particles. What’s more, these clouds themselves physically affect air currents. They are like algae in water — they can be carried away by the current, but if you look closely, you can see that the water flow is also being pushed to the side. You may have seen globular clouds in the sky that swirl around like cotton candy on a stick. The wind simply picks up the clouds and starts swirling them up and down, and if it manages to stroke the wings of the airplane, makes the passengers grip the seat handles tighter.

Moreover, the life cycle of the cloud itself does not stop. Water vapor rises from the ground, and rain forms in the cloud itself as water droplets combine and fall downward. This up-and-down motion seems to push the clouds upside down, which contributes to what is described above — almost chaotic air currents. Finally, when an airplane crosses clouds, it flies out of the shade into direct sunlight, which also affects air currents.

There are many more meteorological processes that occur in and around clouds. But the most important thing to understand is that clouds cause air currents to mix, affect wind and even the distribution of heat from the sun. But interestingly, water suspended in the air also affects airplane engines. Not too long ago, water was intentionally sprayed into airplane engines to cool hot spots, reduce unwanted detonation, and increase engine thrust. There are cars with similar systems — the 2016 BMW M4 uses technology developed with Bosch, and similar systems are used in traction vehicles. However, when flying through clouds, this effect is minimal, and the jolt you feel is not caused by the sudden increase and decrease in engine thrust, but by uneven airflow.