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SEPilot
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RE: Stupid 777 Fact That Is Bugging Me!

Fri May 10, 2002 8:01 pm

Quoting OldAeroGuy (Reply 16):
Who said all the ratios are the same?

I didn't; in fact I said that if they weren't that could account for the difference.
The problem with making things foolproof is that fools are so doggone ingenious...Dan Keebler
 
Boston92
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Stupid 777 Fact That Is Bugging Me!

Sun Jul 01, 2007 10:09 am

Why is the 777-200 one inch taller (tail height) than the 777-300?

[Edited 2007-07-01 03:09:46]
 
Go3Team
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RE: Stupid 777 Fact That Is Bugging Me!

Sun Jul 01, 2007 10:23 am

I think it's because shorter planes need taller tails, although one inch probably doesnt make much difference. Could be, they have the same gear, and the inch difference is due to the weight.
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lehpron
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RE: Stupid 777 Fact That Is Bugging Me!

Sun Jul 01, 2007 11:24 am

Quoting Boston92 (Thread starter):
Why is the 777-200 one inch taller (tail height) than the 777-300?

I grow an inch every time I sleep and loose it throughout the day.  Wink
The meaning of life is curiosity; we were put on this planet to explore opportunities.
 
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Starlionblue
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RE: Stupid 777 Fact That Is Bugging Me!

Sun Jul 01, 2007 11:55 am

Quoting Go3Team (Reply 1):
I think it's because shorter planes need taller tails, although one inch probably doesnt make much difference. Could be, they have the same gear, and the inch difference is due to the weight.

Both good theories.
"There are no stupid questions, but there are a lot of inquisitive idiots." - John Ringo
 
Viscount724
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RE: Stupid 777 Fact That Is Bugging Me!

Sun Jul 01, 2007 11:55 am

I stand to be corrected but I'm almost certain the the tails themselves are the same height on all 777s but the overall height from the ground to the top of the tail probably varies slightly due to the different overall lengths and weights etc. I believe the landing gear is also somewhat different on the -300ER vs. the standard -200 and -300.
 
roseflyer
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RE: Stupid 777 Fact That Is Bugging Me!

Sun Jul 01, 2007 3:39 pm

I would assume it has something to do with the modifications done to the landing gear for the 777-300. 1 inch isn't that much, but could be accommodated with a different gear.
If you have never designed an airplane part before, let the real designers do the work!
 
A342
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RE: Stupid 777 Fact That Is Bugging Me!

Sun Jul 01, 2007 5:49 pm

I also think it has got to do with the landing gear. Maybe the 777 has a (very small) "negative AOA" on the ground. As the nose gear length is the same, the shorter fuselage of the 772 makes the tail stand up higher than on the 773.
Exceptions confirm the rule.
 
OzTech
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RE: Stupid 777 Fact That Is Bugging Me!

Sun Jul 01, 2007 9:31 pm

Just a thought but it might have something to do with the tyre size.. Ply ratings etc. I know the different versions of most Boeings have different ply ratings and diameters etc.
No defect too big, no defect too small, nothing in the log --- No defect at all !!
 
KFLLCFII
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RE: Stupid 777 Fact That Is Bugging Me!

Mon Jul 02, 2007 1:39 am

Why is the tail taller on the 747SP compared to the regular 747 models?

Why is the tail taller on the 736 compared to other 737 models?

Why is the tail taller on the A318 compared to other A32X models?


Because shorter (length-wise) aircraft, in order to get the same amount of lateral performance out of the rudder for engine-out operations, need a larger surface area on the tail to account for the decreased distance of the moment "arm" about the CG.  Wink

And yes, that extra "inch" of additional height can make all the difference in the world with regard to Vmc (minimum-controllable airspeed with an engine out).
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OldAeroGuy
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RE: Stupid 777 Fact That Is Bugging Me!

Mon Jul 02, 2007 2:46 am

Quoting KFLLCFII (Reply 8):
Because shorter (length-wise) aircraft, in order to get the same amount of lateral performance out of the rudder for engine-out operations, need a larger surface area on the tail to account for the decreased distance of the moment "arm" about the CG.

And yes, that extra "inch" of additional height can make all the difference in the world with regard to Vmc (minimum-controllable airspeed with an engine out).

Good thinking, but there is no difference in vertical tail sizes between the -200 and -300 models.

Quoting A342 (Reply 6):
I also think it has got to do with the landing gear. Maybe the 777 has a (very small) "negative AOA" on the ground. As the nose gear length is the same, the shorter fuselage of the 772 makes the tail stand up higher than on the 773

You're on the right track, but the concept is wrong. A negative attitude on the ground would mean the longer body airplane would have the tip of the vertical higher off the ground.

Quoting Go3Team (Reply 1):
Could be, they have the same gear, and the inch difference is due to the weight.

Actually it's the weight and the gear. The documents below give a range for the distance between the tip of the vertical tail and the ground. This distance varies as a function of airplane weight, CG position, and gear strut charge pressure.

Model Min Dist Max Dist

-200 60' 5" 61' 6"
-300 60' 5" 61' 6"
-200LR 60' 8" 61' 6"
-300ER 59' 10" 61'10"

http://www.boeing.com/commercial/airports/acaps/777rsec2.pdf

http://www.boeing.com/commercial/airports/acaps/777rsec2.pdf
Airplane design is easy, the difficulty is getting them to fly - Barnes Wallis
 
brettbrett21
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RE: Stupid 777 Fact That Is Bugging Me!

Mon Jul 02, 2007 3:36 am

I have another questionable fact. I dunno where I heard this and I'm pretty sure that it's wrong.

Is the horizontal stabilizer of the 777 roughly the same size as the 737's wings?
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Boston92
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RE: Stupid 777 Fact That Is Bugging Me!

Mon Jul 02, 2007 3:45 am

Quoting Brettbrett21 (Reply 10):
I have another questionable fact. I dunno where I heard this and I'm pretty sure that it's wrong.

Is the horizontal stabilizer of the 777 roughly the same size as the 737's wings?

The 777 Horizontal Stabilizer is 66 feet wide, the wingspan of the 737 is 112 feet, so yeah, the 777 HS is larger than a 737 wing.
 
Viscount724
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RE: Stupid 777 Fact That Is Bugging Me!

Mon Jul 02, 2007 6:41 am

Quoting OldAeroGuy (Reply 9):
Quoting KFLLCFII (Reply 8):
Because shorter (length-wise) aircraft, in order to get the same amount of lateral performance out of the rudder for engine-out operations, need a larger surface area on the tail to account for the decreased distance of the moment "arm" about the CG.

And yes, that extra "inch" of additional height can make all the difference in the world with regard to Vmc (minimum-controllable airspeed with an engine out).

Good thinking, but there is no difference in vertical tail sizes between the -200 and -300 models.

Assuming you're referring to the 747, the -200 and -300 are the same length.
 
legoguy
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RE: Stupid 777 Fact That Is Bugging Me!

Mon Jul 02, 2007 8:22 am

Quoting Brettbrett21 (Reply 10):
I have another questionable fact. I dunno where I heard this and I'm pretty sure that it's wrong.

Is the horizontal stabilizer of the 777 roughly the same size as the 737's wings?

Slightly off topic but I thought the fact was more along the lines of the A380 horizontal stabilizer is the same size as a 737's wing.
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jetmech
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RE: Stupid 777 Fact That Is Bugging Me!

Mon Jul 02, 2007 11:58 am

Quoting Boston92 (Thread starter):

Could be the extra sag in the longer fuselage  Wink !

Regards, JetMech
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SEPilot
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RE: Stupid 777 Fact That Is Bugging Me!

Mon Jul 02, 2007 8:41 pm

Quoting OldAeroGuy (Reply 9):
You're on the right track, but the concept is wrong. A negative attitude on the ground would mean the longer body airplane would have the tip of the vertical higher off the ground.

Actually, both of you are wrong. If the landing gear are both the same length and the ratio of the length from main gear to nose gear and main gear to tail is the same, the tail height will be exactly the same regardless of length, although the angle will be different. If the ratio changes the height will also change, which may account for the difference.
The problem with making things foolproof is that fools are so doggone ingenious...Dan Keebler
 
OldAeroGuy
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RE: Stupid 777 Fact That Is Bugging Me!

Tue Jul 03, 2007 1:04 am

Quoting SEPilot (Reply 15):
Actually, both of you are wrong. If the landing gear are both the same length and the ratio of the length from main gear to nose gear and main gear to tail is the same, the tail height will be exactly the same regardless of length,

Who said all the ratios are the same?
Airplane design is easy, the difficulty is getting them to fly - Barnes Wallis
 
Boston92
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RE: Stupid 777 Fact That Is Bugging Me!

Tue Jul 03, 2007 1:57 am

Quoting SEPilot (Reply 17):
I didn't; in fact I said that if they weren't that could account for the difference.



Quoting SEPilot (Reply 17):
5 years 1 month 3 weeks 3 days 5 hours ago

I started the thread yesterday, a.net is broken...
 
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SEPilot
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RE: Stupid 777 Fact That Is Bugging Me!

Tue Jul 03, 2007 3:45 am

Quoting Boston92 (Reply 18):
I started the thread yesterday, a.net is broken...

Are you sure? Perhaps you took a quick unwitting trip in your time machine....
The problem with making things foolproof is that fools are so doggone ingenious...Dan Keebler
 
brettbrett21
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RE: Stupid 777 Fact That Is Bugging Me!

Tue Jul 03, 2007 8:36 pm

Quoting Boston92 (Reply 11):
Quoting Brettbrett21 (Reply 10):
I have another questionable fact. I dunno where I heard this and I'm pretty sure that it's wrong.

Is the horizontal stabilizer of the 777 roughly the same size as the 737's wings?

The 777 Horizontal Stabilizer is 66 feet wide, the wingspan of the 737 is 112 feet, so yeah, the 777 HS is larger than a 737 wing.

I actually *gasp* looked it up after I asked, man do I feel dumb!
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A342
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RE: Stupid 777 Fact That Is Bugging Me!

Tue Jul 03, 2007 8:44 pm

Quoting OldAeroGuy (Reply 9):
You're on the right track, but the concept is wrong. A negative attitude on the ground would mean the longer body airplane would have the tip of the vertical higher off the ground.

Yes, but because the forward fuselage is also longer (on the 773), the negative attitude should be reduced, shouldn't it?
Exceptions confirm the rule.
 
OldAeroGuy
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RE: Stupid 777 Fact That Is Bugging Me!

Tue Jul 03, 2007 10:13 pm

Quoting A342 (Reply 21):
Yes, but because the forward fuselage is also longer (on the 773), the negative attitude should be reduced, shouldn't it?

As noted earlier, the change in tail height depends on the ratio between forward and aft body stretches. Note that there is no difference between 772 and 773 vertical tail ranges in Reply 21.

Quoting OldAeroGuy (Reply 9):


Model Min Dist Max Dist

-200 60' 5" 61' 6"
-300 60' 5" 61' 6"
-200LR 60' 8" 61' 6"
-300ER 59' 10" 61'10"
Airplane design is easy, the difficulty is getting them to fly - Barnes Wallis
 
InnocuousFox
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RE: Stupid 777 Fact That Is Bugging Me!

Tue Jul 03, 2007 10:55 pm

I like the 777 fact that you can fit a 737 or MD-80 fuselage inside a 777 engine.  Smile
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