Rwy32R
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A340-500/600 Rudder

Thu Aug 24, 2006 8:35 am

Hi
This morning I was contemplating the beautiful Qatar Amiri Flight A340-500 (A7-HHH) when I noticed something quite strange.
On A340-500/600 the base of the rudder trailing edge seems to be cutted.
What's the reason ?
If the reason is "aerodynamic" ,why the freshly built A340-300 ,A330-200/300 aren't equiped with such rudders ?
I know there was the same question in February 2004,but nobody answered !
Many thanks


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bri2k1
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RE: A340-500/600 Rudder

Thu Aug 24, 2006 8:53 am

Here's my guess: The longer -500/-600 models use a larger horizontal stabilizer (and maybe a larger rudder) to aerodynamically compensate for their greater length. If the rudder was fully deflected while the h-stab trim was in the full nose-down position, it looks like the rudder might contact the stabilizer. It's been cut (not cutted) to provide necessary clearance from the other control surfaces.
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speedracer1407
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RE: A340-500/600 Rudder

Thu Aug 24, 2006 10:51 am

Quoting Bri2k1 (Reply 1):
Here's my guess: The longer -500/-600 models use a larger horizontal stabilizer (and maybe a larger rudder) to aerodynamically compensate for their greater length.

I thought that, as a general rule, shorter planes required larger rudders (donno about H-stabs) to complensate for the shorter moment arm.

O
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vikkyvik
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RE: A340-500/600 Rudder

Thu Aug 24, 2006 10:55 am

Quoting Bri2k1 (Reply 1):
Here's my guess: The longer -500/-600 models use a larger horizontal stabilizer (and maybe a larger rudder) to aerodynamically compensate for their greater length. If the rudder was fully deflected while the h-stab trim was in the full nose-down position, it looks like the rudder might contact the stabilizer. It's been cut (not cutted) to provide necessary clearance from the other control surfaces.

While your clearance-from-other-control-surfaces guess may be accurate, typically, the longer the airplane in a series, the smaller the rear control surfaces. This is due to the longer moment arm from the center of gravity. I believe, for instance, that the A330-200 has larger vertical and horizontal stabs than the -300.

~Vik
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bri2k1
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RE: A340-500/600 Rudder

Thu Aug 24, 2006 11:13 am

Well, that's probably true, moment arm and all. I didn't really think about that when I made my guess. Not knowing how the plane is designed, though, we don't know how far the center of gravity or center of lift moved when it was stretched. I'm still probably wrong in saying they're larger because of the very good reason you pointed out, but come on -- it was just a guess  Smile
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Starlionblue
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RE: A340-500/600 Rudder

Thu Aug 24, 2006 11:19 am

Quoting Speedracer1407 (Reply 2):
I thought that, as a general rule, shorter planes required larger rudders (donno about H-stabs) to complensate for the shorter moment arm.

Correct as a general rule. For a good example, check out the 747SP.

However, the 340-500/-600 are not only longer, they also have larger wings and more powerful engines than the 340-200/-300. So they need more control authority beyond that gained by the greater moment arm.Thus, they borrow the empennage from the 330-200/300/8000. This empennage is larger than on the 340-200/300.

Quoting Vikkyvik (Reply 3):
I believe, for instance, that the A330-200 has larger vertical and horizontal stabs than the -300.

I don't think so. But I may be wrong. However as I said above the 330 empennage is larger than the 340Classic empennage due to greater control authority required in an engine out situation. Compare one engine out of two with one engine out of four.

[Edited 2006-08-24 04:19:33]
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HAWK21M
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RE: A340-500/600 Rudder

Thu Aug 24, 2006 8:16 pm

Thats for Clearence from the Elevator if the Stablizer is in the Nose Down position.
regds
MEL
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vikkyvik
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RE: A340-500/600 Rudder

Thu Aug 24, 2006 9:22 pm

Quoting Starlionblue (Reply 5):
I don't think so. But I may be wrong. However as I said above the 330 empennage is larger than the 340Classic empennage due to greater control authority required in an engine out situation. Compare one engine out of two with one engine out of four.

Well unfortunately they don't have stabilizer reference areas on the Airbus website that I could find. The 330-200 is slightly taller than the -300; considering that it shouldn't need taller landing gear, I'd assume the tail is a bit taller. But that in itself doesn't mean anything.

Also, good point about the engine-out situations.

By the way Speedracer, sorry to repeat you - you beat me to it  Smile

~Vik
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zeke
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RE: A340-500/600 Rudder

Thu Aug 24, 2006 10:27 pm

Quoting Vikkyvik (Reply 7):
Well unfortunately they don't have stabilizer reference areas on the Airbus website that I could find. The 330-200 is slightly taller than the -300; considering that it shouldn't need taller landing gear, I'd assume the tail is a bit taller. But that in itself doesn't mean anything.

If my memory serves correct, the 346 rudder is about a foot longer than the 343. If you were only doing short haul in a 346 designers could have derated the powerplants and used the 343 rudder. However for ULH you need fuel, and thrust to get that mass airborne.

Where thrust ratings of powerplants are similar like on he 737NG series, the above observations about rudder size and moment arms are correct.

The 346 rudder is sized for two engine out operations on one side with a lot more thrust and a larger aircraft.
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boeingfixer
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RE: A340-500/600 Rudder

Thu Aug 24, 2006 11:19 pm

Quoting HAWK21M (Reply 6):
Thats for Clearence from the Elevator if the Stablizer is in the Nose Down position.

Wouldn't that be the full "Nose Up" stab trim + elevator position? LE of the stab down, TE up = Nose Up.  Wink

Cheers,

John
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HAWK21M
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RE: A340-500/600 Rudder

Fri Aug 25, 2006 2:26 am

Quoting BoeingFixer (Reply 9):
Wouldn't that be the full "Nose Up" stab trim + elevator position? LE of the stab down, TE up = Nose Up.

Thats correct .I was reffering to Stablizer nose dwn,elevator tail up.
regds
MEL
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wilax
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RE: A340-500/600 Rudder

Fri Aug 25, 2006 3:29 am

Quoting Bri2k1 (Reply 1):
Here's my guess: The longer -500/-600 models use a larger horizontal stabilizer (and maybe a larger rudder) to aerodynamically compensate for their greater length. If the rudder was fully deflected while the h-stab trim was in the full nose-down position, it looks like the rudder might contact the stabilizer. It's been cut (not cutted) to provide necessary clearance from the other control surfaces

You are aboslutely correct. I read that fact about the 346 a while ago. It is simply there for clearance of the stab.
 
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HAWK21M
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RE: A340-500/600 Rudder

Fri Aug 25, 2006 10:35 am

I may not win often, but I damn well never lose!!! ;)
 
bri2k1
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RE: A340-500/600 Rudder

Fri Aug 25, 2006 10:49 am

Quoting Rwy32R (Thread starter):
I know there was the same question in February 2004,but nobody answered !

Looks like they answered in April 2004.



Thanks, MEL, for posting in replies 6 and 10, and not pointing out the other thread until reply 12.

Quoting Bri2k1 (Reply 1):
It's been cut (not cutted) to provide necessary clearance from the other control surfaces.



Quoting HAWK21M (Reply 6):
Thats for Clearence from the Elevator if the Stablizer is in the Nose Down position.



Quoting HAWK21M (Reply 10):
I was reffering to Stablizer nose dwn,elevator tail up.



Quoting HAWK21M (Reply 12):
http://www.airliners.net/discussions...ech_ops/read.main/87118/6/#ID87118
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HAWK21M
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RE: A340-500/600 Rudder

Fri Aug 25, 2006 10:56 am

Quoting Bri2k1 (Reply 13):
Thanks, MEL, for posting in replies 6 and 10, and not pointing out the other thread until reply 12.

The Search function does not always pick the right thread.Took time to find the post.
Look at it positively....At least We got a link now.
regds
MEL
I may not win often, but I damn well never lose!!! ;)
 
Rwy32R
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RE: A340-500/600 Rudder

Mon Aug 28, 2006 5:23 pm

Thanks to all for your answers.
Bye

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