airplaneguy
Topic Author
Posts: 47
Joined: Tue Dec 29, 2009 12:15 am

How Do Pilots Know When Turbulence Is Ahead?

Mon Jul 12, 2010 10:08 pm

Fellow Nutters,

Recently flew WestJet YYZ-TPA, and a few times along the way the pilot engaged the seatbelt sign and informed us of turbulence ahead. He was right each time. How do pilots know that turbulence is ahead? If it's due to a cockpit instrument, how does the instrument figure it out? Also, what exactly causes turbulence in otherwise normal, straight line, cruise flight, and what causes it to be so localized that altitude changes can avoid it. Thanks in advance.

Airplaneguy
 
FredT
Posts: 2166
Joined: Thu Feb 07, 2002 9:51 pm

RE: How Do Pilots Know When Turbulence Is Ahead?

Mon Jul 12, 2010 10:17 pm

The weather radar, which is mounted in the nose of the aircraft with a scope in the cockpit, will show the storm cells (cumulunimbus clouds). These contain major up- and downdraughts which is felt as turbulence.

Clear air turbulence, such as encountered when going into and out of the jet streams, does not show. Other aircraft flying in front on the same route may report the turbulence on the radio, however.
I thought I was doing good trying to avoid those airport hotels... and look at me now.
 
User avatar
tb727
Posts: 1765
Joined: Thu Jun 30, 2005 1:40 pm

RE: How Do Pilots Know When Turbulence Is Ahead?

Mon Jul 12, 2010 10:30 pm

There are a few ways, ATC will advise of bad rides, also you will hear guys ahead complaining then inevitably someone asks where he is at and you can find out that way. On our flight releases there is also a column that has anything from a 0 to a 10, 10 being the worst on turbulence over every waypoint on our flight plan. I fly freight so it normally doesn't matter to me unless it's something bad enough that we will have to slow down but when I have horses on board we try and make it easy and get smooth routes for them since they are standing the whole time. You can also tell by what kind of cloud types you are heading towards, especially when heading towards Florida this time of year!

When a lot of guys are getting bad rides and we are getting a good one I try and give ATC a heads up that we are getting a smooth ride when I check in once in a while. Hopefully that's a sign that stuff is maybe smoothing out and opens up more options for ATC and for planes that are stuck down low because of bad rides.

This site will give you a basic idea of where you might get some bumps.
http://aviationweather.gov/adds/turbulence/
Too lazy to work, too scared to steal!
 
c5load
Posts: 344
Joined: Tue Sep 16, 2008 9:40 pm

RE: How Do Pilots Know When Turbulence Is Ahead?

Mon Jul 12, 2010 10:59 pm

Quoting tb727 (Reply 2):
On our flight releases there is also a column that has anything from a 0 to a 10, 10 being the worst on turbulence over every waypoint on our flight plan.

But is this based on wx? Is there a radar that can point out specific areas of turbulence, whether it be CAT or Wx related?
"But this airplane has 4 engines, it's an entirely different kind of flying! Altogether"
 
User avatar
Starlionblue
Posts: 17117
Joined: Fri Feb 27, 2004 9:54 pm

RE: How Do Pilots Know When Turbulence Is Ahead?

Mon Jul 12, 2010 11:14 pm

Quoting c5load (Reply 3):
Is there a radar that can point out specific areas of turbulence, whether it be CAT or Wx related?

No. The weather radar shows moisture, not wind flow patterns. So it will show, say, rain clouds and these create turbulence. It doesn't show the turbulence directly. If there is no moisture, as in clear air turbulence, there will be no radar return.
"There are no stupid questions, but there are a lot of inquisitive idiots." - John Ringo
 
User avatar
Buyantukhaa
Posts: 2290
Joined: Thu May 13, 2004 5:33 am

RE: How Do Pilots Know When Turbulence Is Ahead?

Mon Jul 12, 2010 11:21 pm

Another useful site is www.turbulenceforecast.com
I scratch my head, therefore I am.
 
User avatar
tb727
Posts: 1765
Joined: Thu Jun 30, 2005 1:40 pm

RE: How Do Pilots Know When Turbulence Is Ahead?

Tue Jul 13, 2010 1:30 am

Quoting Starlionblue (Reply 4):
No. The weather radar shows moisture, not wind flow patterns. So it will show, say, rain clouds and these create turbulence. It doesn't show the turbulence directly. If there is no moisture, as in clear air turbulence, there will be no radar return.

Yeah. What he said! That is true, a CB will naturally be a rough ride, usually we use the radar to avoid those areas of heavy precip which usually helps avoid the worst turbulence by doing that but there isn't really a way to use the radar to specifically avoid only turbulence.

As far as the numbers on our flight release, I honestly couldn't tell you what exactly it uses but I would imagine it takes winds, jet stream and weather patterns into account. It also picks the best path and altitudes for ride, time and economics as well if you choose. The worst I have seen is a 7 and it was a horrible ride but when the plan said it was going to die down to a smoother ride, it did right where it was supposed to.
Too lazy to work, too scared to steal!
 
flybaurlax
Posts: 589
Joined: Sun Oct 05, 2008 12:34 am

RE: How Do Pilots Know When Turbulence Is Ahead?

Tue Jul 13, 2010 1:42 am

Turbulence is created from air constantly flowing through our atmosphere. It's caused by heating and cooling from the ground, and water. It's like if you have the heat on in the house during winter and you let the door or window open a crack, you will feel the air start to move with a slight breeze. This is heat exchange happens all throughout our atmosphere and so massive amounts of air are constantly moving. Sometimes it's bumpier at other altitudes than others just because of temperature and density at that altitude. Just think of a river, the water on top is going to be moving faster than the water on the bottom (although this is due to the boundary layer).

It's kinda funny because in some of my experiences jumpseating, we would reach our cruising altitude and it would be start to get bumpy just as we level off, and I mean within the last 100' of our climb.

Sometimes you'll hear on the radio pilots checking in saying "LA Center United 169 Flight Level 350 smooth." or "Flight Level 350 light chop."
Boilerup! Go Purdue!
 
dxing
Posts: 5859
Joined: Wed Nov 12, 2008 5:14 pm

RE: How Do Pilots Know When Turbulence Is Ahead?

Tue Jul 13, 2010 1:53 am

Easy, there are several weather products available even to the layman via NOAA in the U.S. and other government agencies world wide. Most pilots are going to at least glance at those products to see what their route looks like. They may also look at published pireps for their route. Someone with even a small amount of met training can spot where the turbulence will be in the atmosphere given a jet stream bend or areas tight pressure gradients. When all else fails either you contact the dispatcher or ATC and ask what it is like on up the road.
Warm winds blowing, heating blue skies, a road that goes forever, I'm going to Texas!
 
etherealsky
Posts: 211
Joined: Fri Apr 09, 2010 6:13 pm

RE: How Do Pilots Know When Turbulence Is Ahead?

Tue Jul 13, 2010 5:02 am

Weather products aside, there are also a few fundamental principles of weather that every pilot should know/recognize by heart (and to be honest, I wish I had a fuller understanding of weather and forecasting because it's a fascinating subject in my opinion).

Turbulence has many causes; it can be created mechanically by things like mountain ranges or other terrain which force passing air to rise. It can be created by areas of strong convective activity where rising pockets of air create atmospheric instability. It can also be created by downdrafts/microbursts or other wind shear situations associated with thunderstorms where you've got large changes in air direction/velocity. Then there's the infamous CAT (clear air turb.) which has caused so many incidents recently at cruising altitude (but I'm not an airline pilot and I don't know much about how CAT works, although it's got something to do with jet streams :P)

One good rule of thumb is that the smoothest air is in grey, rainy, poor-visibility skies full of stratoform clouds. Days with excellent visibility and lots of cumulus buildup are usually the bumpiest.

I was privileged to visit an aircraft salvage yard this summer and saw the remains of an Aero Commander 690 which broke up in flight due to excessive airspeed in moderate turbulence in addition to being over 1,000 lbs. over MTOW. The story goes that the pilot (who was either at or near VNE in smooth air -IIRC- had called ATC a few minutes before the crash and asked how long it would be until they were out of the IFR soup. The controller (using pilot reports and surface observations from surrounding airports, I think..) said it would be only a couple minutes until the plane encountered clear weather with excellent visibility. Unfortunately, the pilot didn't clue in to the fact that they were probably encountering a front and didn't think twice about what happens when you suddenly go from smooth, solid IFR conditions to 'severe-clear' weather. The airplane (carrying passengers on an limited experimental ticket, no less) broke apart at something like 20 knots above the placarded max. airspeed for turbulence.
"And that's why you always leave a note..."
 
ThirtyEcho
Posts: 1409
Joined: Tue Jan 01, 2002 1:21 am

RE: How Do Pilots Know When Turbulence Is Ahead?

Tue Jul 13, 2010 5:43 am

Go to www.liveatc.net

Tune in any ATC Center. If there is chop around, you will hear almost constant chatter about turbulence and altitudes and routes. This will answer your questions.

One of the best Center re-broadcasts is Dubuque, Iowa. It picks up Dubuque tower but it also picks up very clear transmissions to and from Chicago Center. The identifier is KDBQ and it is located under "Class 4".
 
Goldenshield
Posts: 5008
Joined: Sun Jan 14, 2001 3:45 pm

RE: How Do Pilots Know When Turbulence Is Ahead?

Tue Jul 13, 2010 11:17 am

Assuming that crews give PIREPs to the controller, then other people, such as dispatchers can then get that information and pass it on.

If an area is clear of PIREPs, then it's assumed smooth, except in the wee hours of the morning when there are very few PIREPs to substantiate anything.
Two all beef patties, special sauce, lettuce, cheese, pickles, onions on a sesame seed bun.
 
Pihero
Posts: 4206
Joined: Mon Jan 31, 2005 5:11 am

RE: How Do Pilots Know When Turbulence Is Ahead?

Tue Jul 13, 2010 12:48 pm

Quoting tb727 (Reply 2):
On our flight releases there is also a column that has anything from a 0 to a 10, 10 being the worst on turbulence over every waypoint on our flight plan.
Quoting tb727 (Reply 6):

As far as the numbers on our flight release, I honestly couldn't tell you what exactly it uses

Those numbers are called "shear rates" and they are just the wind velocity variation per thousand feet around the aircraft planned altitude.
I find it quite amusing that most of our US-based pilots count so much on each other's experiences and reports ; basically the first one gets the brunt of the turbulence, then goes "hunting" for a better level with ATC, and broadcats the experience to all followers...
That's fair but a study of meteorology can help a lot > For instance everybody has mentrioned the radar and the cunimbs ; but there are a few other clouds which could indicate some really serious potential upsets : lenticular clouds are indicative of a standing wave situation and if one could see the associated lines of rolling cumuli, -which hide the rotors -...then it's high time to take a few anti turb measures.
Another generally unused instrument is the outside temperature gauge, this time very useful in a jetstream situation : a falling outside temp is the first indication of nearing the cold-side edge of the jet, very often the most turbulent.
Visual cues are quite important, some quite unexpected : following an aircraft making a nice set of contrails... suddenly the contrail stops, and doesn't resume : indication of a drastic change in the air mass in terms of temperature and humidity...turb is not far away...
All the above techniques could be taught and learned but I've noticed that pilots nowadays tend to rely on others' info, which is a bit of a shame.
Contrail designer
 
User avatar
tb727
Posts: 1765
Joined: Thu Jun 30, 2005 1:40 pm

RE: How Do Pilots Know When Turbulence Is Ahead?

Tue Jul 13, 2010 8:52 pm

Quoting Pihero (Reply 12):
Those numbers are called "shear rates" and they are just the wind velocity variation per thousand feet around the aircraft planned altitude.

That's right! I forgot that is what they are called, thanks!

Quoting Pihero (Reply 12):
I find it quite amusing that most of our US-based pilots count so much on each other's experiences and reports ; basically the first one gets the brunt of the turbulence, then goes "hunting" for a better level with ATC, and broadcats the experience to all followers...

lol yeah and normally when someone hears my airlines callsign they let us go ahead and be the guinea pig.
Too lazy to work, too scared to steal!
 
airplaneguy
Topic Author
Posts: 47
Joined: Tue Dec 29, 2009 12:15 am

RE: How Do Pilots Know When Turbulence Is Ahead?

Tue Jul 13, 2010 9:34 pm

These are some awesome responses. Totally answered my question. Thanks everyone.
 
bri2k1
Posts: 952
Joined: Sun Dec 19, 2004 4:13 am

RE: How Do Pilots Know When Turbulence Is Ahead?

Tue Jul 13, 2010 9:37 pm

Quoting Pihero (Reply 12):
Visual cues are quite important

This is true, but often, there might not be a lot that can be done about it. Light chop or light to moderate turbulence is more of an annoyance than a safety or operational concern. As a passenger, I would rather get to my destination on time with my seat belt on than 20 minutes late after having been allowed to graze through the cabin while we detoured around some chop. As an airline employee, I (would theoretically) have a responsibility to the shareholders to keep on-time stats up when it doesn't interfere with safety, so I wouldn't try to avoid every bumpy-looking cloud in the sky.

If turbulence increases to the point that it becomes a safety hazard or seriously uncomfortable, most pilots will ask around to see if there are clearer patches. Sometimes there are, and they are only a thousand feet above or below. Other times there are not, or they are hundreds of miles off course. The original plan was to make good time, be responsible with fuel burn, and avoid dangerous weather, and I like to see people sticking to a good plan when it makes sense.

That being said, there are countless times when serious weather, CB or TS, lenticular clouds, and the like show up ahead, and many (US-based!) pilots will ask ATC for a deviation well in advance. Because we generally reserve this kind of deviation for times when we need it, ATC knows it's serious and 99% of the time grants it at pilot's discretion.
Position and hold
 
Fly2HMO
Posts: 7207
Joined: Sat Jan 24, 2004 12:14 pm

RE: How Do Pilots Know When Turbulence Is Ahead?

Wed Jul 14, 2010 6:29 pm

Quoting airplaneguy (Thread starter):
How do pilots know that turbulence is ahead? If it's due to a cockpit instrument, how does the instrument figure it out?

Oh no no, not all. Gifted pilots like myself are can see turbulence pockets with our own bare eyes. We can hear them too. 
 
flybaurlax
Posts: 589
Joined: Sun Oct 05, 2008 12:34 am

RE: How Do Pilots Know When Turbulence Is Ahead?

Wed Jul 14, 2010 7:54 pm

Quoting Fly2HMO (Reply 16):
Oh no no, not all. Gifted pilots like myself are can see turbulence pockets with our own bare eyes. We can hear them too.

I just smell it comin....
Boilerup! Go Purdue!
 
User avatar
Aaron747
Posts: 8557
Joined: Thu Aug 07, 2003 2:07 am

RE: How Do Pilots Know When Turbulence Is Ahead?

Wed Jul 14, 2010 9:24 pm

OK so I have a bit of a question -

Three weeks ago I was on an ANA 777 from NRT to HNL. I checked the Pacific turbulence forecast during my layover at NRT and just as predicted, there were long lines of squalls with tops around FL450 in the vicinity of Midway Island. As it was a red-eye I really enjoyed watching all the lightning from a distance. Sitting on the port side of the aircraft, I noticed at one point while passing a pretty large CB that there was another aircraft off our wing on the opposite side of the cell. I spotted the strobes of another aircraft behind another cell to the left of them. The upper level visibility was excellent so from my view, it was our wing - aircraft strobes - another CB - aircraft strobes - if that makes any sense. We would make a slight course correction to the right every few minutes to keep the distance from the other aircraft it seemed.

So my question is - when everyone can see what's ahead on WX radar in the middle of the ocean and there's several CBs scattered around, do the crews coordinate on HF as to who will go where? "You take the one on the left, and we'll deviate around this one" - or something to that effect? I just found it very interesting that despite what I was seeing it seemed we were all avoiding the cells in an organized fashion without any ATC  

For any of you who do regular flying near large CBs, particularly at night, have you ever witnessed one of those massive positive lightning strikes that shoot out the top of a cell?
If you need someone to blame / throw a rock in the air / you'll hit someone guilty
 
dispatchguy
Posts: 606
Joined: Sun Jan 29, 2006 6:08 am

RE: How Do Pilots Know When Turbulence Is Ahead?

Thu Jul 15, 2010 2:50 am

Quoting Pihero (Reply 12):
Those numbers are called "shear rates" and they are just the wind velocity variation per thousand feet around the aircraft planned altitude.

Not necessarily. I think the Jeppesen flight planning system uses that system, but the SABRE Dispatch Manager (not SABRE FOS like at AA and US) uses some painfully complex algorithm to determine where the rides suck, and numbers above 7 or 8 indicate the crap rides - the numbers go up to 13 or 14 or so.
Nobody screws you better than an airline job!
 
dxing
Posts: 5859
Joined: Wed Nov 12, 2008 5:14 pm

RE: How Do Pilots Know When Turbulence Is Ahead?

Thu Jul 15, 2010 3:16 am

Quoting Aaron747 (Reply 18):
without any ATC

The ATC is still there, they just don't have radar coverage. It's all down by plot. A flight will call in and request a new altitude and KZAK in the case of Midway will either approve or disapprove. The flights are seperated enough on coast out that some lateral course deviations can be done by the crews as long as they call in what they are doing. There are airways out there.
Warm winds blowing, heating blue skies, a road that goes forever, I'm going to Texas!
 
User avatar
Aaron747
Posts: 8557
Joined: Thu Aug 07, 2003 2:07 am

RE: How Do Pilots Know When Turbulence Is Ahead?

Thu Jul 15, 2010 3:35 am

Quoting dxing (Reply 20):
The flights are seperated enough on coast out that some lateral course deviations can be done by the crews as long as they call in what they are doing.

Right - I knew they have the plots I was just curious as to how they know who's doing what - but that clears things up. Between TCAS and the clear night up there I'm sure the crews can see where some of the other aircraft are visually as well.
If you need someone to blame / throw a rock in the air / you'll hit someone guilty
 
ThePinnacleKid
Posts: 497
Joined: Wed Feb 23, 2005 9:47 am

RE: How Do Pilots Know When Turbulence Is Ahead?

Thu Jul 15, 2010 5:04 pm

I can tell it's going to get bad pretty soon when I see white caps forming in my coffee...
"Sonny, did we land? or were we shot down?"
 
User avatar
Aaron747
Posts: 8557
Joined: Thu Aug 07, 2003 2:07 am

RE: How Do Pilots Know When Turbulence Is Ahead?

Thu Jul 15, 2010 8:13 pm

Quoting ThePinnacleKid (Reply 22):
I can tell it's going to get bad pretty soon when I see white caps forming in my coffee...

You also know something interesting is about to hit when the engines suddenly throttle back...
If you need someone to blame / throw a rock in the air / you'll hit someone guilty
 
ThePinnacleKid
Posts: 497
Joined: Wed Feb 23, 2005 9:47 am

RE: How Do Pilots Know When Turbulence Is Ahead?

Thu Jul 15, 2010 9:16 pm

Quoting Aaron747 (Reply 23):
You also know something interesting is about to hit when the engines suddenly throttle back...

I wish I had that... my lil' jet doesn't have auto-throttles.... Just have the rough seas in the coffee...
"Sonny, did we land? or were we shot down?"
 
n92r03
Posts: 361
Joined: Sun Jan 10, 2010 10:46 pm

RE: How Do Pilots Know When Turbulence Is Ahead?

Sat Jul 17, 2010 1:47 am

Was on UA 896 in Dec 2008 HKG-ORD. Pilot came on the PA and said to hunker down as we were first in line across the Pacific and that it was going to be a bumpy ride. It was, but not too bad, was still able to sleep as I had all 3 seats to stretch out on. Was certainly more turbulent that the average flight almost all the way across from Japan to Alaska.
 
comorin
Posts: 3857
Joined: Sun May 29, 2005 5:52 am

RE: How Do Pilots Know When Turbulence Is Ahead?

Sat Jul 24, 2010 4:37 pm

Does extended turbulence cause fatigue? Does it cause inner-ear processing overloads for pilots?
 
wn676
Posts: 1142
Joined: Mon Jun 20, 2005 5:33 am

RE: How Do Pilots Know When Turbulence Is Ahead?

Sun Jul 25, 2010 11:24 am

I was wondering about this recently on a flight from IAH to CCS. We were about a third of the way into the flight, right during the meal service, when the pilot came on and asked all crewmembers to return to their seats immediately. The seatbelt sign came on, and no more that 5 seconds after the announcement we hit some of the most severe turbulence I've ever experienced. It lasted for maybe 15 seconds, but it left one flight attendant sprawled out on top of a row of passengers.
Tiny, unreadable text leaves ample room for interpretation.

Who is online

Users browsing this forum: YYZYYT and 15 guests