Please fasten your seatbelts, we may experience turbulence

For anyone who has flown in an airplane, chances are they have experienced turbulence.  To many, it can be a source of anxiety when flying.  I am going to look at the technical side of what causes turbulence, why it feels like it does, and why it may make you so nervous.  Maybe with a little understanding, it won’t be so bad!

An airplane is held in the air by the air itself.  While the airplane is flying, the air is pushing up on the wings holding it in the air.  In order for the wings to perform this gravity defying act however, there needs to be air passing over the wings.  The faster the plane travels through the air, the more lift the wings produce and vice versa.  When the pilot wants to travel straight and level, he adjusts the speed of the plane so that the wings are making the same amount of lift that gravity is pulling down . The problem is despite the fact you cannot see it, the air is not consistent in it’s denisty nor is it stationary.   So, if the air holding up the plane changes, well, the plane will too!  That’s the simple part of it!

There are many many things that make the air not so consistent.  The first and most obvious one is wind.   We have all felt the wind against our faces, and have also probably experienced heavy wind to the point that it is harder to walk in one direction than another.   The same force that you are feeling walking on that windy day is the same force keeping an airplane in the air.  So what happens if that same gust of wind hits an airplane in the air?  Well, if it is blowing opposite the direction the airplane is traveling in, more lift is created by the wind on the wings…the airplane jumps up!  If the gust of wind is blowing in the opposite direction as the airplane, the airplane will loose lift and fall a little!

In a small airplane like a piper or a Cessna that is only traveling through the air at about 100mph or so, the feeling is more graceful, sort of like the feeling you get in a car traveling ona hilly road at a high speed.  In a big jet airliner that is traveling over 600mph, the feeling is much more forceful because the plane passes through the puffs and gusts of wind more quickly .  The feeling is more like a car riding down a poorly paved highway with lots of ruts and bumps.

Other factors can play a part in turbulence too.  Air does not only move across the land, it can also move up and down.  This is especially noticeable on summer days.  Hot air is less dense and it will rise.  The problem with flying however is that not all the air gets hot and rises at the same time.  The air over land gets hotter than the air over bodies of water.   The air over cities can also rise faster than the air over the countryside.  This is because parking lots and concrete absorb solar heat and make the air over them hotter than the air over wooded areas.   So, what does this all mean for an airplane?

Well,  we all know that the land is not consistent on what is covering it.  There’s a parking lot over there, a building over here, so woods over there and so forth.  Although you cannot see it, that big parking lot has a big column of rising air above it headed up into the sky, and chances are, the lake down the street has a mass of sinking air over top of it.   Columns of rising air are frequently called “thermals”.  Birds frequent thermals because they can use them to stay aloft without having to flap their wings.  In an airplane traveling 600 mph however, passing over a hot parking lot causes a “bump” sort of like running over a rock in your automobile.

Sometimes thermals can get to be really big when combined with weather activity.  Large thermals are how thunderstorms develop when combined with a larger mass of cooler air blowing in.  Those huge towering clouds you see on a hot summer day are created with a large column of rising air carries moisture high into the upper atmosphere as cooler air moves in and displaces it.  Up there in the upper atmosphere, it is cooler, and the moisture condenses out of the air forming the big cloud.  If you fly through this huge column of air however, chances are you will experience a sudden increase in the amount of lift holding your airplane up!  The effects of this air current can be quite strong, and really give a wild ride in a plane.

Turbulence in reality however gives hardly any more G force on the body than a sports car speeding down a road. So, why does the forces caused by turbulence feel so much worse?  Well, much of it has to do with windows and perspective.  The same reason one may get seasick is the same reason why turbulence in an aircraft feels so bad….you can’t see out!  When you are driving in a car entering a curve, going down a hill, or simply hitting a pothole, you can see all around you, but in an airplane, those tiny little windows don’t do much for you, and even if you could see out, there’s not much to look at to gain a perspective to either.

Your inner ear has fluid in it that is excellent for detecting forces on your body.  The problem is that the interior of the airplane is moving with you, so although you can tell that the airplane is being pushed around, you really cannot tell how significant the forces really are.  When you are in a car, you can see the curvy, hilly road ahead.  In an airplane, the air is invisible, so you cannot see the lumps and bumps associated with turbulent air.

In short, the air really isn’t as turbulent as it feels.  It is only magnified because the airplane is moving through different densities of air at a really fast speed!

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