What causes Turbulence?


#1

What causes airplane turbuelence? thanks


#2

Think of disruptions like rocks in a stream for water. In a simple way, the air flowing over the ground is the same way over rough terrain like mountains or small geographic areas like a tree line at a local airport. At my airport KMBO, I experience turbulence just about every time the winds blow from the east or south from the winds following the contours of the lay of the land. I let new passengers that I take up to “expect a bump” in the air above before taking off.

Another form of turbulence especially down here in the south, imagine a pot of boiling water with the bubbles rising from the bottom. Same thing the air does, except you can’t see the rising bubbles. The different rates the air rises is the cause of the up and down turbulence.

Last one I can think of is wind shear turbulence where the winds change direction very rapidly or change in speed very quickly. Take off into a 20 knot wind, and the wind stops, the plane will drop since it doesn’t have the lift underneath the wings to maintain flight.

The above is a very rudimentary explaination of what causes turbulence but hopefully will give an over all picture…

PIREPS (Pilot reports) standards can be found at weather.gov/om/brochures/pilot.htm (scroll toward the bottom).


#3

Is there a way to predict or avoid turbulence??


#4

See Weatherquestions.com for answers to questions you have on weather. For your specific question on turbelance, click this link: What causes turbulence?.


#5

Turbulence is about as predictable as other weather phenomenon. In other words, it can be predicated but not with 100% accuracy.

I’ve been on flights where turbulence was predicted but it the flight was as smooth as silk. Have been on other flights where just the opposite happened.


#6

YES some turbulence can be predictable. This is based on real world flying…

Thunderstorms is one place where turbulence will be experienced. Windshear is another. Both are to be avoided at all cost especially for a little spam can like myself… Windy days flight close to the ground will most certainly cause turbulence. The air is amazingly layered where 500 feet can make the difference between a smooth ride or a ride never to be forgotten.

Hot weather 2:00 in the afternoon in the deep south, you can bet on a bumpy ride, so avoid flying during the heat of the day especially in a GA plane. (imagine that pot of boiling water in my prior post)

If you are not near a weather front, mornings and evening flights will just about guarantee a smooth ride. These are times I take up my first time passengers.

Cold fronts generally you will encounter turbulence.

Look at the clouds. GENERALLY speaking (not 100 percent) the puffy clouds (cumulus) are bumpy as they represent updrafts / rising air. Stratus (flat layered clouds) on the other hand generally provide a very smooth ride. I have found if the clouds have “rough edges” or look ragged, the air around that cloud is turbulent. If the cloud has “hard edges” or well defined edges, generally the air is reasonably smooth.

Airplanes are like cars. The bigger and heavier the plane, the better your ride quality will be as it would take more ooomp from the air to move the airplane. So, while I may report moderate turbulence, a 737 in the same air may think differently, thus the importance of model of plane making the turbulence report.

Airliners take extra effort in safety. In the air, it’s very common for hearing “ride reports” from a company plane ahead on the frequency. If a plane reports light or moderate turbulence then the following plane may ask passengers to buckle up. By the time the plane gets to that point where turbulence was reported, the air may have calmed down or that rising bubble of air dissapated…

“Mechanical turbulence” is predictable especially when winds are blowing from a certain direction. Think of being in Chicago or New York and feeling the winds whip around the buildings. Same thing happens in the air over mountains and again, like at my airport trees causing predictable turbulence.

The most unpredictable turbulence are called CATs (Clear Air Turbulence). Wake turbulence from airplane traffic crossing your path can generate these things.


#7

“Turbulence. Solar radiation heats the Earth’s crust, warm air rises, cold air descends - turbulence. I, I don’t like that.”

Turbulence response has more to do with wing loading (pounds per square foot) than absolute size. Turbulence exerts a pressure on the aircraft, so the bigger the wing the more force; on the other hand the acceleration due to that force decreases with more mass. The F-104 (150 psf) and Dash 8 Q200 (60 psf) have about the same weight, but the latter has about three times the wing area per pound so you would expect a rougher ride in turbulence. Some aircraft have active load alleviation systems that respond to turbulent local atmospheric conditions to smooth the ride.


#8

Good point to bring out on wing loading. My droop wing tips on my plane from what I was told was designed to smooth out the ride during days where a Cessna would be tossed all around.


#9

avoid flying into or by mountain ranges or storms.


#10

OK thanks everybody that was very helpful, exspecially the boiling water example. I have one more question, it seems like there are some flights that are allways turbulent and some that never are, why is that? For example, the three times ive flown BNA-BWI it has always been the absolute worst turbulence (dropping 150ish feet a few times), but it seems that most eastward bound flights are usually less turbulent, for example AUS-BNA tonight, i flew on flt 1425 and it was as smooth as a babies bottom even though we flew over a cold front and that just a few hundered miles to the north there were massive thunderstorms. Why is that? Are all eastbound flights usually smoother due to the gulfstream?


#11

Terrain, terrain terrain. You are going over the Appalachia mountains BNA to BWI. Mountains will induce turbulence especially at the lower altitudes on climb and descents.

Going west BNA to AUS, there are no mountains per se, so the terrain is more conducive of a smoother flight. I don’t see a cold front between AUS and BNA on today’s weather???

flightaware.com/resources/weather_maps/ shows a warm front / stationary front crossing TX WEST of Austin. There is a cold front on the very tail end, but surely wasn’t in your flight path?

I know at my altitudes I fly, west or east, doesn’t make a difference. Can’t say if it’s the same for jet routes or not. I’d be inclined to think not a difference myself.


#12

o well I just looked on weather.com and it looked as if we would have to cross a cold front over memphis maybe?


#13

Yes, there were severe watches & warnings around western TN & KY, and Arkansas as you guys were posting.

After my Grand Canyon flight, I’m a believer in the wing loading theory. The day I went, surface winds were gusting to 28 kts. 30 knots is the limit for most of the canyon tour companies. I was on a Cessna 207, tossed around the whole flight with the stall horn piping up almost constantly. But everyone on the plane pulled thru ok. However, quite a few people exiting the Twin Otters were looking pretty green. Twin Otters have less wing loading that a C207, according to the pilot.

You don’t need to be in the deep south for the boiling water effect, but anywhere it gets pretty warm. PHX area for example, especially this time of year. Anywhere below 15,000 and you’ll get some good pockets during the daytime.

Flying into KSAN’s 27, I usually get some bumps from REEBO (final fix) to the runway, due to the rising terrain next to the airport.


#14

Well, it was already quoted, but here is the mp3 for y’all:

Alec Baldwin in “Hunt for Red October”

–spud–:slight_smile:


#15

Very much so…from the radiational heat off of the surface (which can vary widely from the composition of the surface releasing the heat) and surface/low level winds churning it all up. Some days it can get a bit uncomfortable. :open_mouth: At higher altitudes (jet cruise altitudes) turbulence is primarily caused by shearing, or changes in the speed and/or direction of the upper level (jetstream) winds being flown through.

And as has been said… The higher the wing loading limit of an aircraft’s wing, the more ability it has to flex, absorbing the atmospheric instability that causes turbulence.


#16

Trying to join the mile-high club in a small plane can cause turbulence alsoo. :smiling_imp: :smiling_imp: :smiley: :smiley: :slight_smile: :slight_smile: :laughing: :laughing: :laughing: :laughing:


#17

Never ceases to amaze me the impact mountains have on causing turbulence. The Appalachians and Alleghenys, not really that tall, from Nashville or Pittsburgh east, can really bounce you around. Nothing like the DC-3 days, but…!

And, flying west, right at the Front Range just west of Pueblo or Denver. May have been smooth the first 3 hours and then, bang! welcome to the Rockies! Amazing!

In my days of travel, don’t believe I’ve ever been on rougher flights than those up and down along the Front Range, like Denver to Colorado Springs. Any more turbulent routes?

Airports? Always thought that landing south at Reno was one of the worst. “Is that pilot ever going to get this thing lined up to make a landing?” Any other major airports with severe turbulence/wind problems?