A reader of the blog (one of probably only two or three!) asked if I would talk a little bit about turbulence and what causes it. I know that turbulence is probably the single biggest fear of skittish fliers, so I want to dispel some myths and explain what is actually going on. Knowledge is power. Understanding brings peace. I’m almost never scared when I fly as a passenger because I know what’s going on and what caused that noise that scared so many other people. When you know and understand what is happing, in any situation, it makes things much less frightening.

When I hear people regaling stories of the terrible turbulence they experience and how they “fell almost a thousand feet,” I work hard to not allow my eyes to roll backward and have to bite my tongue until it bleeds. It never ceases to amaze me what people will say about some incident they had on board an airliner. If someone fell a thousand feet, they’d be dead. If you fell off your dining room chair, you probably break your tailbone, and that was just two feet! Without an altimeter, no one can tell how far they’ve fallen (or risen).

Turbulence, in it’s simplest form, is just shifting air. The air is the airplane’s version of a highway. If the air is moving up, the airplane will go up and if it’s moving down, the airplane will go down, just like a car traveling through the mountains. Now imagine that car traveling through the mountains at 500 miles per hour. That slow, gentle slope will be a big bump and toss you around the inside of the car. Small bumps in the air do the same thing to aircraft. A small ripple, at 500 m.p.h. gets magnified. If a large airliner drops just a few feet in a quick bump, that’s enough to send the flight attendants into the ceiling.

The important thing to remember is that even thought the aircraft is getting tossed all around in a lot of turbulence, it is still flying! I liken it to a canoe. The canoe may hit whitewater and get tossed all around because the river is changing directions and making foamy waves, but even so, the canoe is still floating! It is following the surface of the water and an aircraft is following the current in the sky. Unlike in the movies, unless an aircraft stalls (not caused by turbulence) it cannot fall out of the sky. If it’s nose pointed toward the ground and started accelerating toward the Earth, this would cause an increase in airflow over the wings, which causes more lift, which causes the nose to pitch up, which caused the aircraft to stabilize again. Aerodynamics keep the aircraft inherently stable, and when it gets disrupted, like “falling from the sky,” it tends to right itself on its own, by it own aerodynamic design.

Large airliners often have better glide ratios that even small Cessnas because of the design of their wings. At cruise altitude, even if an airliner’s engines fell off, it would be able to glide over 100 miles before hitting the ground, and in that amount of time, you can be sure the pilots have found an airport and are heading right for it. So, turbulence won’t cause the aircraft to fall from the sky because even through the bumps, it is still flying as it follows the ripples in the air. If airplanes flew by being suspended in the air by a chain, then yes, I’d be nervous too if we started bouncing around, as that will put a lot of strain on that chain. I wonder if we think of flying in the same way — dangling by a rope, so bumps may cause that rope to break. Unless the wings fall off, you are fine in bumps.

There are many things that cause turbulence, but five biggies are:
1) Thermal activity from the sun
2) Thunderstorms
3) Jetsream wind
4) Mechanical mountain waves and
5) Wake turbulence generated behind large aircraft.

The sun causes most of the turbulence you feel. The simple version is that it heats the surface of the Earth at differing levels. The hot asphalt parking lot creates a lot more heat than the cornfield next to it. The hot surface of the parking lot causes the column of air above it to rise more rapidly than the warm air above the corn field. These two columns of air are rising at differing speeds and so when an aircraft flies through those two columns, you feel a bump. The sun also causes the formation of thunderstorms. Now pilots don’t fly into them, as they can be destructive. However, even the air surrounding them can be very bumpy. Thunderstorms form with rising air and then falling air which will cause bumps both inside and outside the storm. Some days, it doesn’t matter what altitude you try or direction you fly, the air is just bumpy from storms. Think of the sun like the flame on a gas range. If you put a pot of water above that flame on the stove, it will boil. The heat causes the roiling of the atmosphere, in the same way the water roils and boils in the pan. The worst, most bumpy days occur on what we would call “a pretty, sunny afternoon.” When you see puffy white clouds in the sky, they are bumpy. The smooth days are usually in the winter (less heat for stirring up the sky) and rainy days, where there is no thunder. The atmosphere is at its most stable in a slow, steady rain, without thunder. Thunder means a thunderstorm, which is lots of turbulence, but when there is just a steady rain, the air is as smooth as glass.

The jetstream also causes bumps. They are high winds that encircle the globe and cause more problems in the winter than in the summer. In summer months, they recede up to more northerly latitudes, but in the winter, they drop down to lower ones, like through the middle of the U.S. They are jets of wind that can reach 200 m.p.h. and are like a cylinder of wind moving from West to East. At the core of the “tube of wind” the winds are strongest, and out toward the edge, the winds are less, like 50 m.p.h. Passing through these rapid changes will always make for a bumpy ride.

Mountain waves are where wind blows up the side of a mountain and continue to shoot up into the air. On the downwind side of mountains, there can be very serious bumps, where the wind spills over the peak and spirals down the other side. Don’t be there! When I used to fly from Ohio down to Florida, over the Smoky Mountain range, there was almost a predictable amount of turbulence as the mountains sent wind currents up to the flight levels and annoyed me as I tried to sip my hot coffee.

There is also wake turbulence. The lift created by the wings of a large aircraft cause the air to be stirred up behind it. When smaller jets fly behind bigger ones, air traffic control is always alerting the small guy to be cautious of wake turbulence. Air will spiral horizontally (like the curls of a phone cord) behind the wing tips of aircraft and they become larger as they recede from the aircraft, so they are cone shaped. A small business jet might fit inside the wake from a Boeing 757, and that will flip the jet over on it’s back, as the wings follow the spiraling air. Air traffic control is good about providing enough separation that this is as rare as winning the lottery and pilots are keen on that as well. However, when you start descending for an airport and you get a big jolt, it may be wake turbulence.

Above all else, remember that the pilots are not flying the aircraft you are riding on by remote control from some brew pub in their home town. Their lives are at the same risk as yours! They don’t want to die, either, and will do all they can to keep you safe because their life is on the line too. As a matter of fact, if an aircraft hits a mountain side, guess who dies first? The pilots! I remember one of my flights when I was getting ready to leave DFW for Columbus, Ohio and as a lady boarded, she asked if it was safe to fly with these thunderstorms all around. I assured her that we had onboard radar and would avoid the storms. She asked if I was absolutely sure it was safe. I chuckled and told her: “Look, I care a lot about you as a passenger, but I care even more about me, and I won’t go if I think it will kill me!” She laughed and the light came on in her mind as she said, “Yeah, I guess that makes sense.”

Have no fear of the bumps and remember that the aircraft, though bouncing around, is still just as happy as a clam, following the ripples in the air. The airplane is happy, so you can be too! Enjoy the bumps and think of them as the best roller coaster you’ll ever ride.