Airplane turbulence | Common, but rarely fatal

Although turbulence is a relatively common phenomenon in aviation, it rarely causes accidents like that of the Singapore Airlines flight in which one passenger died and 104 others were injured on Tuesday. The flight control teacher at the Charlesbourg Transport Training Center (CFTC) Pierre Gauthier answered our questions on turbulence to better understand this atmospheric phenomenon.

How does turbulence occur?

Turbulence can be associated with a jet stream. It is an accumulation of air particles which will occur at high altitude, at the junction between cold air and hot air. Where the two air masses meet, the wind can reach more than 300 km/h.

This can greatly destabilize aircraft flying nearby. When crossing a jet stream perpendicularly, it can cause a sudden and instantaneous increase or decrease in the speed of an aircraft.

Are there geographic areas or times of year where we see more than others?

During the change of seasons, when we go from summer to winter or vice versa, we observe much more often very strong jet streams which will fly over the regions between the 30^e and the 60^e parallel.

Turbulence can also be caused by nearby mountainous terrain, such as the Rockies or the Andes. These mountain ranges will produce a bit of the same effect as rocks on the surface of water in a river: the winds will strike these mountain ranges and create very powerful updrafts and downdrafts which will, on occasion, cause very strong turbulence.

Can we predict them or avoid them?

We have tools that help us predict areas where there could be turbulence. We can make forecasts up to 24 hours in advance, but it is not foolproof. A simple cloud can have an effect on warming the ground which will, in turn, warm the atmosphere. And it can influence the layers of the atmosphere over several thousand feet.

There is also turbulence associated with thunderstorms. Thunderstorms are like a chimney of hot air that rises in altitude. So we teach pilots and flight dispatchers the need to plan flights outside of these large chimneys that are the cumulonimbus clouds. But unfortunately, it is possible that on occasion, we have misjudged the proximity of these large storm cells, and this can cause turbulence.

With climate change, do we expect to see more turbulence than before? Or of a higher intensity?

Climate change is causing tropical air masses to rise toward northern latitudes, so there is a greater chance that the clash of these air masses will cause more intense turbulence.

We are also seeing more and more sectors affected by atmospheric disturbances that we did not see 10 or 15 years ago. For example, in the Kuujjuaq region, there were practically no storms before. Now we see some that can reach 35 or 40,000 feet. I’m not a meteorologist, but it’s a safe bet that it’s due to climate change.

Where do you feel the most turbulence on the plane?

If people are not restrained during severe turbulence, they can hit their heads on the ceiling and injure themselves.

In a plane, the most comfortable place is the cockpit, but it is not accessible to everyone. I would say that at the wings or in front is preferable.

The tail of the plane is where the range of movement is greatest. It’s a bit like a leverage effect: the further you are from the pivot, the greater the effects become.