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allrite
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Understanding Turbulence Data

Mon Apr 14, 2008 12:27 pm

I was thinking of taking a JQ flight (JQ17 - A332) northwards between SYD-KIX in the next couple of days. Then I looked at some turbulence information online...

http://www.turbulenceforecast.com/maps/autball12.gif
Source

IDV60075 ** BUREAU of METEOROLOGY - Melbourne ** ** AUSTRALIAN SIGMETS ** 11:20 UTC, 14/04/2008 -------------------------------------------------------------------- YBBB SIGMET BS02 VALID 140941/141541 YMMC- YBBB BRISBANE FIR SEV TURB FCST WI S4700 E16300 - S5000 E16300 - S5000 E15800 - S4400 E15500 - S4400 E15800 - FL200/300 MOV E AT 20KT WKN. STS:REVIEW BS01 140341/140941= YMMM SIGMET ME02 VALID 140941/141541 YMMC- YMMM MELBOURNE FIR SEV TURB FCST WI S4700 E16300 - S5000 E16300 - S5000 E15800 - S4400 E15500 - S4400 E15800 - FL200/300 MOV E AT 20KT WKN. STS:REVIEW ME01 140341/140941= YBBB SIGMET BS01 VALID 140341/140941 YMMC- YBBB BRISBANE FIR SEV TURB FCST WI S5000 E16200 - S4400 E15700 - S4400 E15400 - S5000 E15600 - FL185/300 MOV E AT 25KT NC. STS:NEW=

Bureau of Meteorology - Aviation

(Also Jeppensen, under Australia, gives turbulence maps for different flight levels.)

Now, I'm no pilot so I'm not certain how best to interpret this information or what relevance it has to an A332 about 1 - 2 hours into it a long flight (ie, what altitude it would be cruising at).

Would that red moderate-severe turbulence be likely to impact on the flight?

What measures would be taken to avoid it (ie would the airline/pilot plan a significant course or altitude deviation?)

Is this the jetstream, as these images would seem to indicate?

And on another technical issue, which is the best spot to sit in for vertical turbulence (up and down) so that you feel the minimum of movement? Is it the front of the aircraft or the wingbox? I know from experience it's not the rear! I guess this is determined by the axis of rotation for the aircraft. Does it pivot around the centre of gravity (roughly the wings) or the nose? I can understand the latter as lift (upwards force) is generated at the centre of the plane by the wings so when this force decreases (dropping) the wings should, I think, be the first point to drop.

Sorry for all the questions. Each time I think that I have beaten turbulence I get a flight where I sit at the rear of the aircraft and my fear/displeasure returns.
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wilco737
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RE: Understanding Turbulence Data

Mon Apr 14, 2008 12:39 pm



Quoting Allrite (Thread starter):

Now, I'm no pilot so I'm not certain how best to interpret this information or what relevance it has to an A332 about 1 - 2 hours into it a long flight (ie, what altitude it would be cruising at).

Looks like the tops of the turbulence is at FL300, so if possible get above it where it should be smooth then. And an A332 will be able to climb higher than FL300! Or if possible plan a route which does not penetrate the area of moderate turbulence! but in that case it could be a huge detour!

Quoting Allrite (Thread starter):
Would that red moderate-severe turbulence be likely to impact on the flight?

 thumbsup  I'd say on a flight from SYD-KIX you'll fly through it!

Quoting Allrite (Thread starter):
What measures would be taken to avoid it (ie would the airline/pilot plan a significant course or altitude deviation?)

Flying higher, reroute if possible!

Quoting Allrite (Thread starter):

And on another technical issue, which is the best spot to sit in for vertical turbulence (up and down) so that you feel the minimum of movement?

near the center of gravity! All the movements will be around that point! It is usually near the main gear or slightly ahead of it... The further in the back, the worse it gets! Worst turbulence you have in the rear...

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allrite
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RE: Understanding Turbulence Data

Mon Apr 14, 2008 11:30 pm

Thanks for your answers WILCO737!

Quoting WILCO737 (Reply 1):
near the center of gravity! All the movements will be around that point! It is usually near the main gear or slightly ahead of it... The further in the back, the worse it gets! Worst turbulence you have in the rear...

So turbulent movement at the front of the aircraft should also be moderate compared with over the centre of gravity? Not as much as the rear of the aircraft I know, looking at the aircraft models on my shelf and how much longer they are behind the wing.
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Starlionblue
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RE: Understanding Turbulence Data

Mon Apr 14, 2008 11:40 pm



Quoting Allrite (Reply 2):
looking at the aircraft models on my shelf and how much longer they are behind the wing.

Look at the ones with rear mounted engines one more time.  Wink
"There are no stupid questions, but there are a lot of inquisitive idiots." - John Ringo
 
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allrite
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RE: Understanding Turbulence Data

Tue Apr 15, 2008 12:03 am



Quoting Starlionblue (Reply 3):

Look at the ones with rear mounted engines one more time.



No, can't see any of those on my shelf at work!  Smile
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wilco737
Posts: 7279
Joined: Sun Jun 20, 2004 12:21 am

RE: Understanding Turbulence Data

Tue Apr 15, 2008 4:40 pm



Quoting Allrite (Reply 2):

So turbulent movement at the front of the aircraft should also be moderate compared with over the centre of gravity?

 thumbsup  Yes, the further away from the CG (center of gravity) you are, the worse you feel the turbulence! So, best would be to sit on the CG... Big grin

Quoting Allrite (Reply 4):
No, can't see any of those on my shelf at work! Smile

That's not a huge collection yet  duck 

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