https://www.sciencedirect.com/search?qs=airplane%20lifting%20force&show=25&sortBy=relevance

There are four types of turbulence – light, moderate, severe and extreme. Light turbulence is extremely common, while moderate turbulence, which can cause rapid jumps or jolts, is quite rare: between one and five per cent of all turbulence experienced.

Turbulence usually lasts for no more than 10 or 15 minutes, but occasionally may last for several hours, on and off. This sort of turbulence will unsettle even some regular travelers and will cause drinks to spill. The aircraft may be deviating in altitude by 10 or 20 feet. Clear-air turbulence feels more severe to passengers than it does to the crew on the flight deck, which can make for a stressful flight. However, all forms of air turbulence can be caused by a number of factors, including heat, jet streams and flying over mountain ranges.

Choose larger aircraft and book seats towards the front of the plane or over the wing.You'll feel less turbulence than you will at the back. As soon as you board, tell the cabin crew you're afraid of flying. ... Remember that, while turbulence might feel uncomfortable, it's not dangerous.

Generally, turbulence is quite harmless. Turbulence is relatively common and usually harmless, but that doesn't stop it from being any less uncomfortable mid-air, and mid-moment.

Turbulence creates instantaneous variations in relative wind speed (due to horizontal bursts) and angle of incidence (due to vertical bursts), which then create lift variations. This variation of the lift is essentially due to the direction of the air flow, which remains random in case of turbulence.

By construction, a plane is stable, that is to say that when it leaves its equilibrium because of a gust, it resumes of itself as soon as the gust is passed. Turbulence is something fast and instantaneous. Also, by its time of analysis and reaction, a pilot who wishes to calm the effects of turbulence, often only amplifies the phenomenon. As a result, except in exceptional cases, the best thing to do is to lock the handle and move as little as possible.

Thanks Haikel Ben Hamed

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