LHLX
Topic Author
Posts: 112
Joined: Wed Nov 30, 2011 6:25 am

Turbulence To Brazil - Stronger On 744/340?

Wed Nov 30, 2011 6:36 am

Hey everyone, after at least 6 years of reading I decided enough is enough and I signed up. This is my first post.

In April 2011 I flew TLV-GRU-TLV on an LY 772, on both ways there was zero turbulence, not even in that "notorious" area where the AF Airbus went down. I have 2 flight attendants friends, one BA one AF. They both told me that this area is almost always very turbulent.

Now, I do love flying but strong turbulence, particularly over the sea makes me nervous.
I am supposed to fly to GRU again in April, either with LX 340 via ZRH or LH 744/TAM 77W via FRA.

My question is the following: The 777 and the 747 seem "heavier" in the air than the Airbus 340. Does this have any influence on how strong the turbulence is felt? Also, any info on turbulence on flights to/from South America is appreciated!

Thanks  
 
BMI727
Posts: 11176
Joined: Mon Feb 02, 2009 9:29 pm

RE: Turbulence To Brazil - Stronger On 744/340?

Wed Nov 30, 2011 6:41 am

Quoting LHLX (Thread starter):
The 777 and the 747 seem "heavier" in the air than the Airbus 340. Does this have any influence on how strong the turbulence is felt?

Force is always going to be equal to mass times acceleration. And there are tons of other factors that go into flight dynamics too. Sure a smaller plane will get tossed around more, although it will almost always experience a smaller force.

That said, the difference between a 777 and an A340 or any other airliner is likely to be imperceptible. If it does feel smoother, it will be because of active gust alleviation, which I don't recall if the 777 and A340 have or not. I know the A380 and 787 do. Really it just seems most likely that you just caught it on a good day.
Why do Aerospace Engineering students have to turn things in on time?
 
AA737-823
Posts: 4956
Joined: Wed Mar 01, 2000 11:10 am

RE: Turbulence To Brazil - Stronger On 744/340?

Wed Nov 30, 2011 7:31 am

It has a lot to do with wing loading, though I can't really explain all of the detail behind that. Douglas had very high load designed wings; that is, the wing was carrying more weight per square meter than a different wing. Consequently, when these high-loaded wings hit turbulence, they are forced to flex more, and transmit less of the shock to the fuselage.
At least, that's how it has been explained to me here on a.net.
BUT- that's not relevant, unless KLM's MD-11 is in your options.

Otherwise, between a 777 and 747, you're not going to notice much difference. And I suspect the Airbus widebodies are right in there as well.

That said, the ride is smoothest in the seats which are over the wing. In that location, your stomach doesn't have to deal with fuselage flex.
 
tdscanuck
Posts: 8572
Joined: Wed Jan 11, 2006 7:25 am

RE: Turbulence To Brazil - Stronger On 744/340?

Wed Nov 30, 2011 3:13 pm

Quoting BMI727 (Reply 1):
Sure a smaller plane will get tossed around more,

Not necessarily, it all depends on wing loading. There is a general correlation between small aircraft and low wing loading (think C172) but it's not absolute. Something like an F-22 has really high wing loading.

Quoting AA737-823 (Reply 2):
It has a lot to do with wing loading

Exactly. What you feel as turbulence is changes in acceleration. Absolute force doesn't have anything to do with perceived levels of turbulence. What matters is how much the force on the wings changes when you encounter turbulence; that's inversely proportional to the wing loading. Highly loaded wings experience a smaller proportional change in force when they encounter turbulence, so the resulting change in acceleration is lower.

Quoting AA737-823 (Reply 2):
Consequently, when these high-loaded wings hit turbulence, they are forced to flex more

Flex may help damp some of the effects but that's not particularly well correlated to wing loading. A glider has low wing loading and huge flex...a fighter has very high wing loading and negligible flex.

Tom.

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