cpqi
Topic Author
Posts: 27
Joined: Wed Apr 14, 2010 7:31 pm

What Is The Truth Behind Turbulence

Thu Jul 28, 2011 7:20 am

I am a very frequent and nervous flyer. A few hours ago we departed SCL for GRU. Over the Maipo Valley and then turned to the Andes. On reaching the Andes the plane dropped and climbed rather violently for 3 minutes. People screamed and many prayed for safety (or a quick death). It was perhaps the worst I have experienced, although I know that it was only severe turbulence and not extreme (no trolleys hitting the roof). As I sit in GRU waiting for the connection to FOR I am wondering if the engineers or pilots can give a really honest answer. I know the wings bend, I know planes are made for the worst of conditions - but it this dangerous ? Txs
I hate turbulence
 
sandyb123
Posts: 743
Joined: Mon Oct 15, 2007 9:29 pm

RE: What Is The Truth Behind Turbulence

Thu Jul 28, 2011 7:34 am

Quoting cpqi (Thread starter):
but it this dangerous

Short answer is that in 99.99% of cases no.

Turbulence is when the wing / aircraft flies through disturbed air or areas of high and low pressure close together. This causes changes to the lift in the wing which is what then creates the bumpy flight.

Depending on the aircraft you flew the flight director will adjust the control surfaces, throttles etc to maintain as smooth a flight as possible at the altitude, route and speed selected. I came back across the alps on Saturday night PMI - EDI in a A319 and it was a bit choppy over central France. Was loving the feeling of the plane compensating for the lumpy air.

There are cases of extreme turbulence causing structural damage but it's so rare nothing to worry about  

Sandyb123
Member of the mile high club
 
cpqi
Topic Author
Posts: 27
Joined: Wed Apr 14, 2010 7:31 pm

RE: What Is The Truth Behind Turbulence

Thu Jul 28, 2011 7:40 am

Thanks Sandy - I know the question is asked too often and after more than 500 flights I believe what you say. I guess after such a scary route (and it was severe believe me) I just need to read some reassuring words
I hate turbulence
 
Pihero
Posts: 4196
Joined: Mon Jan 31, 2005 5:11 am

RE: What Is The Truth Behind Turbulence

Thu Jul 28, 2011 8:57 am

Quoting sandyb123 (Reply 1):

Turbulence is when the wing / aircraft flies through disturbed air or areas of high and low pressure close together.

Turbulence is when the airflow is no longer laminar : there isq an amount of vertical movements inside the flow.
That kind of disturbances of the smooth current has many causes :
- Thermals inside which one sees convective movements, generally materialised by cumulus-type clouds;
- Convection inside a cloud mass. these *convective* currents are the reason a cloud keeps on existing / growing.
- *Orographic* turbulence or *mountain waves*, happens when there is an important obstacle across the wind flow ; as a matter of fact, you'd see two *floors* of disturbance :
1/- the wave at altitude, generally materialised by a set of lenticular clouds, and
2/- a set of rotors just behind the lee-side of the mountain range . Either one of these two phenomena could have associated severe turbulence. That's the turbulence that the OP experienced and it's a lot more usual than people would think? Happens everytime there is a westerly blowing across the Andes (which is about 350 days a year).
- Lastly, the turbulence associated with the Jet stream, on the cold side. It can generate severe CAT if there is a compression associated, i.e a drastic change of direction or a descending airflow.

Most of these can be easily forecasted... BUT it doesn't mean it can be avoided : taking off from SCL, well, you should know you could be in for a bumpy ride. IMHO, the pilot should have warned the passengers and reassured them prior to the event : "Ladies and gentlemen, there is quite a lot of wind blowing over the Andes and the flight up to Mendoza could be rather bumpy. I'd advise you to make sure your seat belt is securily fastened, just for your comfort"...
Contrail designer
 
CHRISBA777ER
Posts: 3715
Joined: Thu Mar 01, 2001 12:12 pm

RE: What Is The Truth Behind Turbulence

Thu Jul 28, 2011 9:06 am

Not dangerous - scary sometimes but not dangerous.

I think the best thing, in a weird sort of way, is to experience prolonged severe turbulence first hand. Its not pleasant, but once you experience it, you have a frame of reference and compare all future events to it. Most people encounter severe turbulence once or twice in their lives - many people think they have encountered it, but few actually have as it is quite rare for aircraft to fly into/near it for obvious reasons. Its not unsafe, its just that nobody wants trolleys and bags and stuff flying round the cabin, and the cabin crew do not want to be cleaning chunder off the carpets and seats.

I've encountered it once - enjoyed it at the time because my wife (who is a nervous flyer and would have been terrified) wasnt with me.
What do you mean you dont have any bourbon? Do you know how far it is to Houston? What kind of airline is this???
 
goldorak
Posts: 1353
Joined: Sat Sep 09, 2006 5:29 am

RE: What Is The Truth Behind Turbulence

Thu Jul 28, 2011 3:29 pm

Quoting Pihero (Reply 3):
Lastly, the turbulence associated with the Jet stream, on the cold side. It can generate severe CAT if there is a compression associated, i.e a drastic change of direction or a descending airflow.

Thank you Pihero for these explanations. The case I quoted from your post is probably what I experienced (?) recently aboard AF A388 flying to IAD on sunday July 10. We experienced severe turbulences (according to the warning given by the Captain) during 15 min, passing south of Greenland. The worst turbulences I experienced and the 15 min seemed very long. But the big whale managed it very well  
 
Pihero
Posts: 4196
Joined: Mon Jan 31, 2005 5:11 am

RE: What Is The Truth Behind Turbulence

Thu Jul 28, 2011 6:09 pm

Quoting goldorak (Reply 5):
We experienced severe turbulences (according to the warning given by the Captain) during 15 min, passing south of Greenland.

Yes, in all probability. It's one of the places I've seen the worst CAT.
Contrail designer
 
FoxBravo
Posts: 2769
Joined: Fri Nov 21, 2003 1:34 pm

RE: What Is The Truth Behind Turbulence

Thu Jul 28, 2011 6:16 pm

Quoting Pihero (Reply 3):

Thanks, Pihero, for the very informative summary.

Quoting goldorak (Reply 5):
The case I quoted from your post is probably what I experienced (?) recently aboard AF A388 flying to IAD on sunday July 10. We experienced severe turbulences (according to the warning given by the Captain) during 15 min, passing south of Greenland. The worst turbulences I experienced and the 15 min seemed very long. But the big whale managed it very well

Very interesting to hear of your experience, Goldorak, since I was also on an AF A388 on July 10, flying from JFK to CDG. My flight was also quite bumpy over the mid-Atlantic, much to my surprise as I was expecting a smoother ride on the "whale." I suspect we were a bit farther south than your route, as we were heading east--the turbulence wasn't severe, but it was enough to wake me up, and definitely rougher than the average transatlantic flight (and I've taken a dozen so far this year!). Must have been a strong jetstream that day.
Common sense is not so common. -Voltaire
 
jrodATC
Posts: 20
Joined: Thu Mar 03, 2011 2:19 pm

RE: What Is The Truth Behind Turbulence

Thu Jul 28, 2011 6:31 pm

Quoting goldorak (Reply 5):
We experienced severe turbulences (according to the warning given by the Captain) during 15 min, passing south of Greenland. The worst turbulences I experienced and the 15 min seemed very long. But the big whale managed it very well

Glad I didn't deal with any CAT on a recent flight to KEF. The trip from JFK to KEF was just south of Greenland and the return was through the country... Again, smooth in both directions on an FI 757 named Hengill  .

I am also a nervous flyer but what makes me most nervous are the prospects of hidden issues with aircraft such as human factors, metal fatigue parts, potentially shoddy maintenance, and freak accidents a la Scandinavian 751, UA 811, TK 981, AS 281, etc...

I try not to think about it by telling myself fate is fate and if it's going to happen, it'll happen.
 
goldorak
Posts: 1353
Joined: Sat Sep 09, 2006 5:29 am

RE: What Is The Truth Behind Turbulence

Thu Jul 28, 2011 6:41 pm

Quoting FoxBravo (Reply 7):
Very interesting to hear of your experience, Goldorak, since I was also on an AF A388 on July 10, flying from JFK to CDG. My flight was also quite bumpy over the mid-Atlantic, much to my surprise as I was expecting a smoother ride on the "whale." I suspect we were a bit farther south than your route, as we were heading east--the turbulence wasn't severe, but it was enough to wake me up, and definitely rougher than the average transatlantic flight (and I've taken a dozen so far this year!). Must have been a strong jetstream that day.

That's funny  
And you were also flying later than me in this zone, so the conditions may have changed a bit. I crossed the Atlantic may be close to 200 times but this is the worst I had. The 2nd worst transatlantic flight, in terms of turbulences, was a DTW-CDG in feb 2010 on board an AF A332 with 1/3 of the flight time very very bumpy in a continuous way, which is very annoying and disturbing. Of course impossible to sleep in these conditions.
 
FoxBravo
Posts: 2769
Joined: Fri Nov 21, 2003 1:34 pm

RE: What Is The Truth Behind Turbulence

Thu Jul 28, 2011 7:06 pm

Quoting goldorak (Reply 9):
And you were also flying later than me in this zone, so the conditions may have changed a bit. I crossed the Atlantic may be close to 200 times but this is the worst I had. The 2nd worst transatlantic flight, in terms of turbulences, was a DTW-CDG in feb 2010 on board an AF A332 with 1/3 of the flight time very very bumpy in a continuous way, which is very annoying and disturbing. Of course impossible to sleep in these conditions.

True, it was late in the evening by the time we passed through that area. I'm glad it smoothed out a bit for my flight. I haven't crossed the Atlantic quite as often as you, but have done it at least 80 times, in a wide variety of conditions. I agree, continuous turbulence can be very annoying, especially when trying to sleep--I've had a few flights like that. The rational part of me knows that there's really no danger, but I still find it difficult to relax during stronger turbulence. Actually, on my recent A380 flight, there were two problems--even when the turbulence itself didn't wake me up, the A380 cabin is so quiet that the "fasten seatbelt" announcements woke me up every time!
Common sense is not so common. -Voltaire
 
kellmark
Posts: 542
Joined: Thu Dec 21, 2000 12:05 pm

RE: What Is The Truth Behind Turbulence

Thu Jul 28, 2011 7:37 pm

Sounds you like you hit mountain wave turbulence over the Andes.

Transport category aircraft are designed to withstand 2.5 Gs positive and 1.0 Gs negative. (Actually they are tested to much greater tolerances than that).
 
Worldliner
Posts: 62
Joined: Wed Aug 24, 2005 11:23 pm

RE: What Is The Truth Behind Turbulence

Thu Jul 28, 2011 7:46 pm

Isnt it just weather at high altitude? I believe turbulence is worse over mountain ranges and at lower altitudes.

The worst experience i have had is on a BA 767 on JFK - MAN, where even the flight attendants were scared and i dont remember the fasten seatbelt sign going off for a good 2-3 hours.

Whenever going across the Atlantic now i find myself on a 777, and we usually fly a few thousand feet higher, and its always smooth.
@777Worldliner
 
LAXdude1023
Posts: 4431
Joined: Thu Sep 07, 2006 3:16 pm

RE: What Is The Truth Behind Turbulence

Thu Jul 28, 2011 8:04 pm

In my travels, this is what Ive found. For the smoothest rides:

Crossing the Atlantic: between late April and September
Crossing the Pacific: between May and October
South America: March-June/October-December, however, you can always expect some turbulence crossing the ITCZ

As bumpy as the Atlantic can get, crossing the Pacific is always more turblent. The nastiest turbulence Ive ever had was from NRT to DFW last May. Of the 11 hours in the flight, 10 1/2 were smooth, but we hit a patch of severe turbulence that was crazy about an hour off the coast of Japan.
It is what it is...
 
emalad
Posts: 365
Joined: Tue May 30, 2006 9:51 pm

RE: What Is The Truth Behind Turbulence

Thu Jul 28, 2011 8:14 pm

I'm not normally scared by turbulance, however 2 instances made me feel a little nervous/worried:

Bay of Bengal - Every time I have flown to Malaysia/Australia on MH we have experienced quite bad turbulance when the cabin crew have been instructed to stop serving the meals and go back to their seats. The first time, they got to the row infront of me and had to stop, I was a little annoyed but was happier when there was a large bump and the meals went all over the laps of the people eating infront    Was pretty cool sitting by the wing and watching it flex!

Manchester - Last February I was on a KLM flight to Amsterdam. We took off towards Stockport and I have never felt so scared in my life. The plane was climbing with a bit of bumping, then suddenly the plane dropped, throttled up and started to climb, dropped again, throttled up and climbed fairly bumpy. There was no comment or anything from the captain, but people were pretty scared. Not sure what caused it though, as I can't remember it being that windy.
 
744lover
Posts: 168
Joined: Mon Nov 06, 2000 5:29 am

RE: What Is The Truth Behind Turbulence

Thu Jul 28, 2011 8:33 pm

Hi cpqi...


This kind of turbulance is very tipical from the Andes... You feel like on a roller-coaster: all of a suden it drops a few hundred feet and then up again....


Best regards!
744lover
 
FoxBravo
Posts: 2769
Joined: Fri Nov 21, 2003 1:34 pm

RE: What Is The Truth Behind Turbulence

Thu Jul 28, 2011 8:50 pm

Quoting LAXdude1023 (Reply 13):
As bumpy as the Atlantic can get, crossing the Pacific is always more turblent.

Totally agree. Some of my roughest flights have been over the Pacific--it always seems to be "cabin crew be seated" for a stretch east of Japan, and I've also had some nasty turbulence between Hawaii and California. The good news is that, at least in my experience, the worst of it doesn't usually last very long.

Quoting emalad (Reply 14):
Bay of Bengal

Yep, that's another bumpy spot for sure.

I think the worst I've had, though, was right after takeoff from Palm Springs in a CRJ--felt like we were being thrown all over the place for a few crazy moments.
Common sense is not so common. -Voltaire
 
tdscanuck
Posts: 8572
Joined: Wed Jan 11, 2006 7:25 am

RE: What Is The Truth Behind Turbulence

Thu Jul 28, 2011 9:01 pm

Quoting cpqi (Thread starter):
although I know that it was only severe turbulence and not extreme (no trolleys hitting the roof).

From your description, it may not even have reached the level of severe. Turbulence strong enough to damage the airplane is far beyond what will petrify even seasoned fliers.

Quoting cpqi (Thread starter):
. I know the wings bend, I know planes are made for the worst of conditions - but it this dangerous ?

Not as you described it, no.

Tom.
 
Pihero
Posts: 4196
Joined: Mon Jan 31, 2005 5:11 am

RE: What Is The Truth Behind Turbulence

Thu Jul 28, 2011 9:19 pm

I wouldn't like this thread to turn into scary experiences :
YOU ARE QUITE SAFE !

Let's, shall we get a more accurate idea of the influence of turbulence in terms of accelerations, bearing in mind that an aircraft, by certification can sustain 2.5 g without a permanent deformation.
1:- Horizontal gust :
The formula is N = 1 + 2 v / V where N is the acceleration ( we prefer the term *load factor* ), v the gust velocity and V the aircraft speed. Here, let's take a speed of 250 m/s equivalent to a .82 Mach or 485 kt.
developping the above, we find that 2v / V = 1.5 ===> v = 1.5 x 250 / 2 = 187.5 m/s or 675 km/h or 365 kt.
That's one hell of a gust !

2:- Vertical gust :
Here the formula goes N = 1 + k v.V /W/s where W/s is the wing loading and k a coefficient for each aircraft which takes into account its characteristics : wing and airframe elasticity, damping... etc...
The *instantaneous* gust does not exist but we accept that k could be around .2, thus the gust value will be around 15 m/s or some 2600 ft/min
That's one hell of a gust, too. !
Of course, the slower the aircraft gets, the lower the load factor. In some freak weather occurrences,i.e mountain wave situation over the Rockies, aircraft encounter them during their approach or initial climb-out phases, when their speeds are still quite low.
So, you see, turbulence can be impressive, spectacular...etc... but you are very far from the inflight break-up scenario !
On the other hand, it's a reminder that one should keep one's seat belt securily fastened as being projected to the ceiling is the most dangerous aspect of turbulence.

[Edited 2011-07-28 14:20:50]
Contrail designer
 
User avatar
Starlionblue
Posts: 17055
Joined: Fri Feb 27, 2004 9:54 pm

RE: What Is The Truth Behind Turbulence

Thu Jul 28, 2011 10:04 pm

As one pilot immortally said: "If you're going to worry, don't worry about turbulence. Worry about windshear."

Quoting tdscanuck (Reply 17):
Turbulence strong enough to damage the airplane is far beyond what will petrify even seasoned fliers.

Quite. The vast majority of turbulence experienced by pax is "light". Sometimes "moderate" is encountered. "Severe" is apparently quite something but I am pretty sure I've ever been there, despite hundreds of flights, some of them very bumpy. And even "severe" is typically no danger.

Quoting cpqi (Thread starter):
I know that it was only severe turbulence and not extreme (no trolleys hitting the roof).

I don't think "extreme" is an official definition. As I have been told it is as follows.:

Moderate Turbulence. There may be moderate changes in aircraft attitude and/or altitude, but the aircraft remains under positive control at all times - usually, small variations in air speed - changes in accelerometer readings of 0.5g to 1.0g at the aircraft's centre of gravity - difficulty in walking - occupants feel a strain against seat belts - loose objects move about.

Severe Turbulence. Abrupt changes in aircraft attitude and/or altitude - aircraft may be out of control for short periods - usually, large variations in air speed - changes in accelerometer readomgs greater than 1.0g at the aircraft's centre of gravity - occupants are forced violently against seat belts - loose objects are tossed about.
"There are no stupid questions, but there are a lot of inquisitive idiots." - John Ringo
 
dlednicer
Crew
Posts: 513
Joined: Sat May 28, 2005 9:35 am

RE: What Is The Truth Behind Turbulence

Thu Jul 28, 2011 11:56 pm

 
FoxBravo
Posts: 2769
Joined: Fri Nov 21, 2003 1:34 pm

RE: What Is The Truth Behind Turbulence

Fri Jul 29, 2011 1:31 am

Quoting dlednicer (Reply 20):

Haha, that cartoon was the first thing I thought of when I saw the thread title! It's a classic.
Common sense is not so common. -Voltaire
 
bond007
Posts: 4423
Joined: Mon Mar 14, 2005 2:07 am

RE: What Is The Truth Behind Turbulence

Fri Jul 29, 2011 1:48 am

Quoting Starlionblue (Reply 19):
Quite. The vast majority of turbulence experienced by pax is "light". Sometimes "moderate" is encountered. "Severe" is apparently quite something but I am pretty sure I've ever been there, despite hundreds of flights, some of them very bumpy. And even "severe" is typically no danger.

Right! It's possible that although the pilot may have advised pax about the 'severe turbulence', that may have been 'severe' as in what the pax might expect, and not the true definition. Few flights encounter severe turbulence, and from my experience of pax reports, they generally classify the level of turbulence at least one level higher than it actually is.


Jimbo
I'd rather be on the ground wishing I was in the air, than in the air wishing I was on the ground!
 
cpqi
Topic Author
Posts: 27
Joined: Wed Apr 14, 2010 7:31 pm

RE: What Is The Truth Behind Turbulence

Fri Jul 29, 2011 2:10 am

I want to thank you all for so much comment. From the description this was indeed severe turbluence, we were on a violent roller coaster. I have landed in NY in a thunderstorm with lightening all around and in a snowstorm in Glasgow - that was tame compared to the turblence on this flight. Pihero - as always that is some fantastic analysis. The knowledge does really help to calm my nerves. Chrisba777er - I totally agree with you. The connecting flight from GRU to FOR was more turbulent than usual but frankly I didnt care (aside from the lack of sleep). I had survived the big one and nothing else would match that. 744lover - I think you have helped me decide that someone else will be making regular trips to SCL to care for our business there, not me !!! As always great help and advice from the professionals
I hate turbulence
 
bond007
Posts: 4423
Joined: Mon Mar 14, 2005 2:07 am

RE: What Is The Truth Behind Turbulence

Fri Jul 29, 2011 2:14 am

Quoting cpqi (Reply 23):
From the description this was indeed severe turbluence

Yes, I wasn't implying your experience wasn't severe ... but generally pax say 'severe' when it's barely moderate


Jimbo

[Edited 2011-07-28 19:17:15]
I'd rather be on the ground wishing I was in the air, than in the air wishing I was on the ground!
 
wn700driver
Posts: 1475
Joined: Wed Aug 29, 2001 10:55 pm

RE: What Is The Truth Behind Turbulence

Fri Jul 29, 2011 3:33 am

Quoting tdscanuck (Reply 17):

From your description, it may not even have reached the level of severe. Turbulence strong enough to damage the airplane is far beyond what will petrify even seasoned fliers.

I think moderate chop is about the most I've ever experienced. When it was done, our galley looked like a pantry threw up in there. There was crap everywhere, and a few of us scrambled to "organize" galleys. No emergency landing or anything like that. The thing I'll never forget though was when our purser said "Cheer up kids. We're all getting Laid!" Ah.. memories...
Base not your happiness on the deeds of others, for what is given can be taken away. No Hope = No Fear
 
SAAFNAV
Posts: 337
Joined: Wed Mar 17, 2010 5:41 pm

RE: What Is The Truth Behind Turbulence

Fri Jul 29, 2011 4:35 am

Quoting cpqi (Thread starter):
but it this dangerous ? Txs

For a pax, very dangerous if you don't keep your seatbelt fastened. Even if it is just lightly around your lap
On-board Direction Consultant
 
User avatar
Starlionblue
Posts: 17055
Joined: Fri Feb 27, 2004 9:54 pm

RE: What Is The Truth Behind Turbulence

Fri Jul 29, 2011 8:07 am

Quoting cpqi (Reply 23):
From the description this was indeed severe turbluence, we were on a violent roller coaster.

Probably not severe actually. Severe turbulence is avoided by pilots if at all possible. As wn700driver notes, even "moderate" is quite enough to make it look as if a bomb went off in the cabin.
"There are no stupid questions, but there are a lot of inquisitive idiots." - John Ringo
 
ILUV767
Posts: 3035
Joined: Mon May 29, 2000 2:21 pm

RE: What Is The Truth Behind Turbulence

Fri Jul 29, 2011 6:12 pm

Severe turbulence requires an aircraft inspection.
 
voiceofgoa
Posts: 22
Joined: Wed Feb 23, 2011 5:41 am

RE: What Is The Truth Behind Turbulence

Sat Jul 30, 2011 5:14 am

I was recently on an Icelandair flight from SEA to KEF. It was smooth until about an hour from Iceland (we had just crossed the shore of eastern Greenland) when suddenly, with no warning, it felt as if someone administered a solid punch to the aircraft. It was unusual, the force and suddenness. The pilots immediately turned on the seatbelt sign and asked the FAs to take their seats. I presume this was CAT, invisible to the radar? Usually there is a soft lead-in into turbulence, but this one was a step function.

On a flight last week from GOI to BOM in a 737, I noticed that the pilot was bobbing and weaving the aircraft. There were heavy monsoon clouds (this is the monsoon season in western India), so I presumed he was making rapid adjustments trying to avoid the 'weather.' I had never seen anything like this before. And he stayed at around 24,000 ft the whole 45 mins flight (normally they climb to 33-35K). Is there special training for flying in monsoon conditions?
 
KELPkid
Posts: 5247
Joined: Wed Nov 02, 2005 5:33 am

RE: What Is The Truth Behind Turbulence

Sat Jul 30, 2011 6:10 am

If you don't want to be subject to bumps and the movements of the fluid in which you're travelling, then don't travel in it   It just happens to be the best medium in which we humans have mastered travel within...it gets you there safer and quicker than the alternatives    And yes, it is much bigger and more powerful than anything we've built so far to travel in it...although bigger aircraft get bumped around less than smaller ones. Also, aircraft with higher wing loading get bounced around less than aircraft with light wing loadings...
Celebrating the birth of KELPkidJR on August 5, 2009 :-)
 
User avatar
Starlionblue
Posts: 17055
Joined: Fri Feb 27, 2004 9:54 pm

RE: What Is The Truth Behind Turbulence

Sat Jul 30, 2011 9:15 am

Quoting voiceofgoa (Reply 29):
Is there special training for flying in monsoon conditions?

Not sure if it is really special training, but certainly pilots used to flying in the tropics tend to have more practice in the conditions. Down here pilots will typically try to avoid the big clouds pretty actively.

Quoting voiceofgoa (Reply 29):
And he stayed at around 24,000 ft the whole 45 mins flight (normally they climb to 33-35K). I

This can happen anywhere due to prevailing winds. For example I've flown LHR-MAN at FL240.
"There are no stupid questions, but there are a lot of inquisitive idiots." - John Ringo
 
Viscount724
Posts: 18846
Joined: Thu Oct 12, 2006 7:32 pm

RE: What Is The Truth Behind Turbulence

Mon Aug 01, 2011 1:03 am

Quoting tdscanuck (Reply 17):
Quoting cpqi (Thread starter):
although I know that it was only severe turbulence and not extreme (no trolleys hitting the roof).

From your description, it may not even have reached the level of severe. Turbulence strong enough to damage the airplane is far beyond what will petrify even seasoned fliers.

FAA description of turbulence types:

TURBULENCE INTENSITY

a. Light Chop. Slight, rapid, and somewhat rhythmic bumpiness without appreciable changes in altitude or attitude.

b. Light Turbulence. Slight, erratic changes in altitude and/or attitude. Occupants may feel a slight strain against seatbelts. Unsecured objects may be displaced slightly. Food service may be conducted and little to no difficulty walking.

c. Moderate Chop. Rapid bumps or jolts without appreciable changes in aircraft altitude or attitude.

d. Moderate Turbulence. Changes in altitude and/or attitude occur, but the aircraft remains in positive control at all times. It usually causes variations in indicated airspeed. Occupants feel definite strain against seatbelts, unsecured objects are dislodged, and food service and walking are difficult.

e. Severe. Large, abrupt changes in altitude and/or attitude. Usually causes large variations in indicated airspeed. Aircraft may be momentarily out of control. Occupants are forced violently against seatbelts, unsecured objects are tossed about, and food service and walking are impossible.

f. Extreme. Aircraft is violently tossed about and is practically impossible to control. May cause structural damage.
 
tdscanuck
Posts: 8572
Joined: Wed Jan 11, 2006 7:25 am

RE: What Is The Truth Behind Turbulence

Mon Aug 01, 2011 5:38 am

Quoting Starlionblue (Reply 31):
Not sure if it is really special training, but certainly pilots used to flying in the tropics tend to have more practice in the conditions. Down here pilots will typically try to avoid the big clouds pretty actively.

Amen to that. I've heard an awful lot of "Cleared to deviate 100 miles left/right of course for weather" in the South Pacific.

Tom.
 
shnoob940
Posts: 171
Joined: Sat Sep 27, 2008 9:53 am

RE: What Is The Truth Behind Turbulence

Wed Aug 03, 2011 12:34 pm

Quoting Viscount724 (Reply 32):
e. Severe. Large, abrupt changes in altitude and/or attitude. Usually causes large variations in indicated airspeed. Aircraft may be momentarily out of control. Occupants are forced violently against seatbelts, unsecured objects are tossed about, and food service and walking are impossible.

I have had an experience like that on a DJ flight BNE-SYD a few years back. We were the last flight in before they closed the airport due to severe weather and we had to go around twice. Everyone was screaming and crying and the cabin erupted into applause when we finally landed.
A319 A320 A321 A332 A333 A359 A388 733 734 735 737 738 739 743 744 762 763 772 77E 773 77W 788 789 E170 E190 Q400 AT7 DH
 
Goldenshield
Posts: 5005
Joined: Sun Jan 14, 2001 3:45 pm

RE: What Is The Truth Behind Turbulence

Wed Aug 03, 2011 2:35 pm

Quoting Pihero (Reply 3):
- *Orographic* turbulence or *mountain waves*, happens when there is an important obstacle across the wind flow ; as a matter of fact, you'd see two *floors* of disturbance :
1/- the wave at altitude, generally materialised by a set of lenticular clouds, and

Except that mountain waves aren't actually turbulent. They are quite smooth. The inability to maintain altitude could be disasterous when you have multiple aircraft crossing the area.

The rotor, on the other hand, is another story.
Two all beef patties, special sauce, lettuce, cheese, pickles, onions on a sesame seed bun.
 
Pihero
Posts: 4196
Joined: Mon Jan 31, 2005 5:11 am

RE: What Is The Truth Behind Turbulence

Wed Aug 03, 2011 9:53 pm

Quoting Goldenshield (Reply 35):
Except that mountain waves aren't actually turbulent.

Turbulence could be defined as the loss of laminarity of the airflow, i.e the different vectors materialising the flow are no longer parallel to one another. The wave status is hardly thus.
So, as far as I'm concerned, a phenomenon that would give me important vertical gust values so much that some control losses have been experienced is plenty turbulent to me.
Contrail designer
 
eisenbach
Posts: 98
Joined: Mon Mar 05, 2001 12:57 am

RE: What Is The Truth Behind Turbulence

Wed Aug 03, 2011 10:59 pm

Quoting Goldenshield (Reply 35):
Except that mountain waves aren't actually turbulent. They are quite smooth. The inability to maintain altitude could be disasterous when you have multiple aircraft crossing the area.

The rotor, on the other hand, is another story.

Completely laminar flows over mountain ranges and even hills are very rare - as the air flow is disturbed, you will have rotors, "ripples", waves,...

There are some "good" turbulences with westerly winds in VIE behind an unimpressive hill range, on some windy days the turbulences at Vienna are even worst than Innsbruck.
DC-6, Do228, Saab340, Twin-Otter, C212, Fokker50, AN24, ATR42, ATR72, Dash8-400Q, MD90, MD83, EMB120, A300, A343, A346, B721, B743, B748...
 
notaxonrotax
Posts: 964
Joined: Wed Mar 16, 2011 2:29 pm

RE: What Is The Truth Behind Turbulence

Thu Aug 04, 2011 3:09 am

Quoting sandyb123 (Reply 1):

Short answer is that in 99.99% of cases no.

Understood.
However, what if it happens at very low altitude?
I know wind shear is a different phenomena, but unexpected violent movements has brought down airliners.

I can only talk about my tiny LSA, but here we have notorious runways at which you have to battle the elements till the very (bitter) end.
Unforeseeable moves from left to right, up and down makes for interesting flying at times, and an unforeseen change of underwear on extreme days.

Quoting tdscanuck (Reply 17):

From your description, it may not even have reached the level of severe. Turbulence strong enough to damage the airplane is far beyond what will petrify even seasoned fliers.

Tom, I know one of your hobbies is going rather extreme in brand new aircraft.
So my question is, do you actively pursue turbulence?
Do you intentionally go for wind shear as well?

And how bad was your worst experience?
Did your can of coke just hit the roof, or did you manage to cause structural damage?


Cheers!!

No Tax On Rotax
For anybody that happens to be wondering:"yes, owning your own aircraft is a 100% worth it!"
 
User avatar
Starlionblue
Posts: 17055
Joined: Fri Feb 27, 2004 9:54 pm

RE: What Is The Truth Behind Turbulence

Thu Aug 04, 2011 8:53 am

Quoting notaxonrotax (Reply 38):
Quoting sandyb123 (Reply 1):

Short answer is that in 99.99% of cases no.

Understood.
However, what if it happens at very low altitude?

Well sure, but it would have to be VERY violent to actually send the aircraft out of control or damage the aircraft. In most cases turbulence just bumps the aircraft around max a few meters. That's not enough to cause problems.

There was an accident with an NLM Cityhopper F28 (flight 431) where it flew through a tornado in the midst of thunderstorms the right wing broke off. Not that more altitude would have helped.

Man-made turbulence at low altitudes is more of an issue, specifically wake turbulence. AA587 is a prime example. Certainly the low altitude was a factor since time for recovery was very short.

I remember that landing at LHR on the southern runway there would often be a jolt very low as the aircraft flew past a line of hangars. Wind from the north would, I guess, flow over and around and create a turbulent pocket. There was a jolt but the aircraft didn't really move very much. Again, not a problem.


BTW in a docu about the Blue Angels they asked a pilot if turbulence was a problem in formation. His answer was something like: "Well, we tend to hit it together so we all bump in the same direction." 
"There are no stupid questions, but there are a lot of inquisitive idiots." - John Ringo
 
tdscanuck
Posts: 8572
Joined: Wed Jan 11, 2006 7:25 am

RE: What Is The Truth Behind Turbulence

Thu Aug 04, 2011 1:08 pm

Quoting notaxonrotax (Reply 38):
Tom, I know one of your hobbies is going rather extreme in brand new aircraft.
So my question is, do you actively pursue turbulence?

Yes, when testing calls for it.

Quoting notaxonrotax (Reply 38):
Do you intentionally go for wind shear as well?

Not that I'm aware of. I certainly haven't, although I've had wind shear warnings during other flying.

Quoting notaxonrotax (Reply 38):
And how bad was your worst experience?

I've seen moderate turbulence (FAA definition), not severe. But it's a lot different when 1) you know it's coming and 2) you're at the pointy end and have much better situation awareness than a typical revenue passenger.

Quoting notaxonrotax (Reply 38):
Did your can of coke just hit the roof, or did you manage to cause structural damage?

Although negative g testing is part of certification (your coke will hit the roof if you don't secure it), I've managed to miss that and only do 0g. In 0g you usually go a tiny bit negative so you can be sure you hit the test point, at which point lots of stuff floats up a few inches/feet then drops back down. The last time I did it the pilot managed to get all the garbage right back in the same bags.

Tom.
 
Pihero
Posts: 4196
Joined: Mon Jan 31, 2005 5:11 am

RE: What Is The Truth Behind Turbulence

Thu Aug 04, 2011 1:19 pm

Quoting eisenbach (Reply 37):
There are some "good" turbulences with westerly winds in VIE behind an unimpressive hill range, on some windy days the turbulences at Vienna are even worst than Innsbruck.

Yeah ! Seen some real sporty approaches there (2 GoArounds once !)
Contrail designer
 
Goldenshield
Posts: 5005
Joined: Sun Jan 14, 2001 3:45 pm

RE: What Is The Truth Behind Turbulence

Thu Aug 04, 2011 2:01 pm

Quoting Pihero (Reply 36):
Turbulence could be defined as the loss of laminarity of the airflow, i.e the different vectors materialising the flow are no longer parallel to one another. The wave status is hardly thus.
So, as far as I'm concerned, a phenomenon that would give me important vertical gust values so much that some control losses have been experienced is plenty turbulent to me.

I agree with you here. Flying through the wave slowly, as gliders do, you wouldn't see much change at all. Flying through it at jet speeds, the constant up-down could be quite jarring.
Two all beef patties, special sauce, lettuce, cheese, pickles, onions on a sesame seed bun.
 
User avatar
Aquila3
Posts: 496
Joined: Sun Nov 14, 2010 3:18 pm

RE: What Is The Truth Behind Turbulence

Thu Aug 04, 2011 4:29 pm

Quoting eisenbach (Reply 37):
Quoting eisenbach (Reply 37):
There are some "good" turbulence's with westerly winds in VIE behind an unimpressive hill range, on some windy days the turbulences at Vienna are even worst than Innsbruck.


Yes, I guess Wieners are quite acquainted with turbolences an wind in general. You can experience them even in a car riding the highway to the south just out of the city. Neat 90 degrees gusts. You guess why the placed there a lot of windmill generators..
About mountain wave, you should try Lugano in Switzerland . There to the mountain wave has even given a name "l'urlo del Ceneri" (the scream of Mount Ceneri) since is present most of the times.
The stripe, right to feet of the Alps and with the lake in front, makes for some interesting landings, especially in the winter. My deep respects to the pilots (Swissair at the time) that always managed it safely.
chi vola vale chi vale vola chi non vola è un vile
 
notaxonrotax
Posts: 964
Joined: Wed Mar 16, 2011 2:29 pm

RE: What Is The Truth Behind Turbulence

Fri Aug 05, 2011 11:40 pm

Quoting tdscanuck (Reply 40):
In 0g you usually go a tiny bit negative so you can be sure you hit the test point,

You mean you go a bit further into the weather system to make sure you go negative?
Or do pilots make violent inputs to get over the 0g edge?

I do wonder though, if even you guys don´t hit "severe"……..when is severe actually tested on an airframe?

Quoting tdscanuck (Reply 40):
The last time I did it the pilot managed to get all the garbage right back in the same bags.

Kudos for keeping the cockpit tidy!!



No Tax On Rotax
For anybody that happens to be wondering:"yes, owning your own aircraft is a 100% worth it!"
 
User avatar
Starlionblue
Posts: 17055
Joined: Fri Feb 27, 2004 9:54 pm

RE: What Is The Truth Behind Turbulence

Sat Aug 06, 2011 12:06 am

Quoting notaxonrotax (Reply 44):
I do wonder though, if even you guys don´t hit "severe"……..when is severe actually tested on an airframe?

My guess is that's what static testing is for. No need to risk the aircraft.
"There are no stupid questions, but there are a lot of inquisitive idiots." - John Ringo
 
tdscanuck
Posts: 8572
Joined: Wed Jan 11, 2006 7:25 am

RE: What Is The Truth Behind Turbulence

Wed Aug 10, 2011 11:58 pm

Quoting notaxonrotax (Reply 44):
Quoting tdscanuck (Reply 40):
In 0g you usually go a tiny bit negative so you can be sure you hit the test point,

You mean you go a bit further into the weather system to make sure you go negative?

I can't speak for all, by my group would never go for 0g in a weather system...we'd do it in clear air with a visible horizon and minimal turbulence. Getting to 0g is done by diving for speed, pulling up into a climb, then pushing over to 0g. You can do a straight pushover from level flight but that makes it harder to hit the altitude/speed/g point that you're going for.

Quoting notaxonrotax (Reply 44):
Or do pilots make violent inputs to get over the 0g edge?

You don't want to use violent inputs...too much chance of missing the test point and/or overstressing the aircraft. It's all done "slowly" and smoothly.

Quoting notaxonrotax (Reply 44):
I do wonder though, if even you guys don´t hit "severe"……..when is severe actually tested on an airframe?

Like Starlionblue said...static test. To actually hit severe in flight on purpose you'd have a significant chance of accidentally going past it to "dead".

Tom.

Who is online

Users browsing this forum: Google Adsense [Bot] and 12 guests