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Respect the Sign

Turbulence is a daily reality in aviation, but that doesn’t stop all pilots from doing their best to steer clear of it. The possible absence of visual clues where turbulence resides forces flight crews to rely on their knowledge of its causes as well as reports from other nearby aircraft to avoid it. Although a recent trend of turbulence related injuries might substantiate a dose of fear in the mind of some passengers, the likelihood of aircraft damage resulting in a crash is highly remote. However, unexpected encounters of rough air with passengers and flight attendants not strapped in their seats is cause for concern and certainly bares reason to respect an illuminated seatbelt sign.

By definition, turbulence is an unsteady movement of air. Because of the uneven heating of our planet by the suns rays, resulting temperature variations give birth to wind as well as our global weather patterns - all having their hand in the creation of turbulence. Disruption in the flow of wind caused either by obstacles in its path or different wind velocities interacting with one another can create undetectable turbulence better known as clear-air turbulence (CAT). Although turbulence in-of-itself is invisible, inclement weather in the form of thunderstorms or where two or more weather fronts meet often produces obvious signs of bumpy air ahead. Minus these visual clues however, CAT demands a knowledgeable crew to anticipate its likelihood.

Surface heating causes turbulent pockets of rising warm air called thermals, especially in the summer months. Thermals can be found all over the earth’s surface where the sun has a pin-pointed and dramatic impact on objects such as pavement and mountain sides compared to lesser heat absorbed surroundings. Particularly during departure and arrival phases of flight, these often unavoidable turbulent spots are cause for annoyance with potential for nausea!

Couple rising warm air with moisture and cumulous clouds (tall and puffy appearance) can form. These moderately turbulent clouds can eventually grow into thunderstorms (cumulonimbus clouds), often higher than 60,000 feet. Within a thunderstorm, rising moist air cools and condenses into water droplets large enough to fall to the surface as rain. The combination of rising and falling air within the core of a storm is cause for severe turbulence and is to be avoided – often by more than 20 miles. Thunderstorms in the vicinity of airports are a major threat to departing and approaching aircraft due to their associated downdrafts as a result of heavy rainfall. These downdrafts impact the ground and disperse in all directions causing dramatic wind shear called a “microburst”. Microbursts have been linked to numerous aircraft accidents, spawning a plethora of both onboard and ground-based technology to detect and help aircraft avoid their presence.

Turbulence related to a disruption in wind is usually the most difficult to avoid due to the absence of visual cues, i.e., CAT. At higher altitudes CAT can be found in numerous locations, most notably near the jet stream and mountainous areas. The jet stream is a high altitude river of air that flows from west to east. Pilots use the jet stream to their advantage when flying east, as these winds can provide well over a 200mph tailwind. Flying west is clearly a detriment, but either way the price to pay with the jet stream is the turbulence it can cause when flying near its edge. Just like a fast flowing river tends to create “eddies” of turbulent water where it meets a stationary shore, the jet stream also creates turbulent eddies where it meets relatively still air.

Wind related turbulence is also often imparted by interference with stationary objects. As wind forces air up the side of a mountain, gravity attempts to restore the risen air back down the other side. This gravitational pull alongside the horizontal push of wind at a mountaintop causes a phenomenon called “mountain wave turbulence” and can be quite severe. The presence of saucer shaped “lenticular” clouds occasionally lends a visible clue of existing mountain wave turbulence, often spanning more than 200 miles downwind of a mountain range. Closer to the ground, buildings and trees tend to disturb surface winds, creating turbulence not nearly as severe as mountain wave turbulence.

Rough air also tends to reside where air masses converge to form frontal boundaries. Air masses are large volumes of temperature and moisture-constant air, often spanning thousands of square miles. Where two different air masses meet i.e., the frontal boundary, winds have a tendency to suddenly change in both direction and speed, resulting in turbulence of varying severity. One obvious clue of a frontal boundary is a defined change in weather, such as a sharp and drastic line where thunderstorms and/or cloud formations begin and end.

Avoiding turbulence begins on the ground with thorough pre-flight planning. Prior to each flight, pilots digest an array of meteorological data at their disposal and enact a strategy of steering clear, or at the very least, coping with areas of bumpy air. To paint a big picture of the weather issues facing a particular flight, crews plot their route on a map that simultaneously displays weather radar returns, frontal boundaries, and wind data. Where threats are pinpointed, a decision may be coordinated with a flight planner to alter a route or cruising altitude in an effort to deviate around expected turbulence.

Once in flight, flight crews use onboard weather radar as well as their own eyes to avoid potential rough air. Additionally, radio communicated turbulence reports between air traffic control (ATC) and other nearby aircraft can provide a “heads-up” solution for other aircraft seeking a smooth ride. For example, an aircraft experiencing turbulence at 36,000’ might report their experience and request a “ride report” from ATC. ATC in turn may inform the pilots that an aircraft 50 miles ahead of them is reporting smooth conditions at 32,000’. At the pilot’s request, ATC would likely permit a descent to the affected aircraft in search of smoother air.

When juggling decisions, pilots must always prioritize safe outcomes, occasionally at the detriment of passenger comfort. Consequently, aircraft or fuel endurance limitations may prevent flight crews from desired turbulence deviations. In this case, or anytime the Captain determines turbulence is a threat, extinguishing the seatbelt sign may not be in the cards. Considering a rising trend of passenger apathy toward an illuminated seatbelt sign, my hope is that this information provides a newfound respect to an often unpredictable danger.

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Max Tribölet 13
Daniel, great insight on the many causes of turbulence. Hopefully this provides some wisdom to the flying public.
Good luck with that wisdom to the flying public who jump with the slightest movement.
Funny, in all my business and leisure flying time, during a variety of unusual flying situations that would cause most novice flyers to scream, in almost all I have witnessed calm and control. Certainly never people getting jumpy from the slightest turbulence.
joel wiley 7
Very good. From the perspective back in coach, the ultimate passenger comfort IMHO, is arriving safely in one piece.
bigal3322 4
It's always great to read about turbulence about how to avoid it and how to deal with it. It's just something that we need to understand and respect. Awesome information.
KC Hoover 4
Call me a sissy, but after so many rough flights, I have gotten into the habit of not taking off my seatbelt during a flight. I have had some really turbulent flights over the Pacific ocean and these were over 11 hours flights. Very information article
Agree and a "dollar store" travel mug keep my beverage hot/cold longer and doesn't spill.
peteral 3
Thank you for posting this. After reading, I now have a better understanding of turbulence and what causes it. The more you know about something, the less it scares you.
Bruce Cohen 2
Thank you for the article. I was on a Continental Express flight with severe turbulence a few years ago. At the worst, anyone not belted in would certainly have been thrown from their seat. The pilot handled it brilliantly. He told us what was going on (becoming sandwiched between two storm systems), warned us what would happen, and said from the safety concern he was more concerned about spilling his coffee than anything else. He also got on the horn every 3 minutes telling us it was ok and that when he saw a hole in the eastern storm we would feel a sharp bank to the right, go through 2 minutes of bad turbulence and then would be fine. This is what happened and when we were in clear air everyone applauded. I thanked the pilot for keeping everyone calm with his words. As we were getting off the plane, the conversation was that it was the pilot that kept us calm, and without his words we would be panicked.
WavemanT 1
I completely agree. For example, an announcement such as "Ladies and gentlemen, we're entering a turbulent area, so I'm turning the seat belt sign on - the ride should smooth out in 20 minutes or so" is far better than one that doesn't give any indication of the expected duration of the disturbance. I recall one flight during which we experienced moderate turbulence flying through cloud tops. The captain took the unusual step of announcing that while the ride was no doubt disconcerting to us passengers, it was no problem for the aircraft and we would be in smooth air in a while.
isardriver 2
thank you for this very informative report
loufrankel 2
Similarly to the below, I always have my seat belt on when seated. I don't understand why seat belts are not required at all times, just like in a car. Instead of a seatbelt light, A/C should have a stay in your seat light. When the light is off, you can get out of your seat but once you return, the seat belt must go back on.
Donald McCann 2
There is a lot more useful turbulence forecast information available to pilots today than what was available just a few years ago. And even better forecasts are on the way. Stay tuned.
Y Win 1
I recommend it to be red by most of air travellers simply to notice the illuminated seat belt sign and act on it. We all have to play a role for safty of air travelling.
Tom Weber 1
I agree. I'm amazed how many passengers rip off the belt immediately when the sign comes off - it's not like an airplane seat belt is that uncomfortable. Even if they just loosened it a bit and kept it on, it would help avoid their head bumping the ceiling in the case of CAT.

I also think they should show the video of that CRJ getting spun on the ground by an A380 during the safety briefing. I'm amazed how many people throw off the seat belt immediately after landing!
dgsandigo 1
Ditto - and then there are those who disobey the seat beat sign when illuminated to get that all-important iPad or laptop or who-the-hell-knows-what out of their luggage in the overhead bin! I always watch in disbelief and silently wish for a quick but forceful "bump" to teach them a lesson (though what usually happens is an FA embarrasses the living daylights out of them over the PA system).
Dee Lowry 1
Dgsandigo...all it would take, is for the cockpit crew to "tap" the brakes and that person, who is getting their all important iPad or Laptop out of the overhead bin, would turn into a human projectile. Hopefully, you or anybody else are not in the path of that projectile. Not a pretty sight.
dgsandigo 1
By and large, most of my fellow passengers on my weekly flights tend to be an obedient bunch - and I'm one of those folks who never takes the seat belt off unless nature calls - but I'm always surprised at those who blithely ignore the seat belt sign, on occasion even getting up minutes after take-off when the plane is obviously climbing...when I see such blatant disobedience of crew directions (I'm hard-pressed to call it ignorance) and, as you mention, possible endangerment of others, that's what gets me!
Fred Heasley 1
Excellent article, gives me a better understanding of why I can be strapped in for long periods when flying long haul.
Flying an aeroplane is not an easy task.Travelers must not worry because the pilots with the electronic facilities they can afort they are doing their job very well to avoid turbulence to make the trip as smooth as possible.
Feel very much enlightened.Thank you.
OhanaUnited 1
Well written. I am going to share this with climatology & meteorology students
Dee Lowry 1
Keep it low and tight...if you don't, you'll meet the ceiling inflight. Great post Daniel! We, as Crew Members get it but the "Flying Public" doesn't have a clue. I've seen alot and been literaly slammed about in my 30 years.
(Retired) United Flight Attendant
great article !!!
Klaus Feinberg 1
AOPA Member?
Daniel Fahl Staff Writer 1
Donna Bell 1
Wow, this is so informative - my first time reading an article here, and find it very helpful! After reading about the turbulence around a thunderstorm and the necessity to avoid, I'll be a lot more patient during future travel when delayed by weather! =) Thanks for a some great explanations!
Very informative, thanks so much Daniel.
The turbulence that bothers me is when the pilot/copilot in training stalls the plane about 30 ft off the runway during landing like what I experienced at Minneapolis/St. Paul about 25 yrs ago on a DC-9. Needless to say the pilot/copilot did not want to be greeted by the passengers disembarking so they let everyone off at the rear stair ramp. A first for me.
Keith Schäfer 1
Great artikel, thanks
raymond watson 1
a very intersting article,thanks for the info.
Fred Fuchs 1
Allen Schnaak 1
My father is a retired captain from a major airline with over 35k hours and has Influence my flying habits in 2 ways 1). ALWAYS wear your seat belt when seated, if not for your own safety, the safety of those around you. And 2) ALWAYS wear your shoes during take off and landings.
Excellent description of turbulence , calming for any nervous traveller. Well done.
Alf Goddard 1
A very interesting article. I have learnt a great deal more about turbulence and what may cause it. I will now feel a bit more relaxed when in such a situation. Great information. Thanks.


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