747400sp
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What If There Was A Trijet Built Off The 777 Tec?

Sat Sep 13, 2008 1:33 am

I was thinking earlier, about how Airbus got started. Airbus got it's name, because of what the A300 was design to do, which was to do the job L1011's and DC10's was design to do. The US airbuses (L1011, DC10) was originally twin jets but was change to trijets thank to a request from TWA and UA, but Airbus Kept there airbus a twin jet.

I was wondering, if there was an aircraft company that designed a band new plane around the same time the T-7 was design, but it was a trijet using the same engines as T-7 has, want do you think would become of that airliner?
 
jcchristie
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RE: What If There Was A Trijet Built Off The 777 T

Sat Sep 13, 2008 7:54 am

I would think it would fail. Why have 3 engines when you do just fine with 2?
 
andz
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RE: What If There Was A Trijet Built Off The 777 T

Sat Sep 13, 2008 8:09 am

Imagine a GE-90 in the tail, that would be outrageous!
After Monday and Tuesday even the calendar says WTF...
 
acNDTTech
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RE: What If There Was A Trijet Built Off The 777 T

Sat Sep 13, 2008 4:51 pm



Quoting Jcchristie (Reply 1):
Why have 3 engines when you do just fine with 2?

Why have 4 when you could have 2 or 3?
 
DfwRevolution
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RE: What If There Was A Trijet Built Off The 777 T

Sat Sep 13, 2008 6:11 pm



Quoting AcNDTTech (Reply 3):
Why have 4 when you could have 2 or 3?

Four engines is preferable over three. Tail-mounted engines bring a host of technical issues that make them more complicated than just hanging 4 smaller engines from the wing.
 
RussianJet
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RE: What If There Was A Trijet Built Off The 777 T

Sat Sep 13, 2008 7:58 pm

Man, it would look cool though.
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columba
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RE: What If There Was A Trijet Built Off The 777 T

Sun Sep 14, 2008 7:34 am



Quoting 747400sp (Thread starter):
I was wondering, if there was an aircraft company that designed a band new plane around the same time the T-7 was design, but it was a trijet using the same engines as T-7 has, want do you think would become of that airliner?

The same engines would have been difficult as the fan diameter of the 777 engines are too big for a third engine, there was a trijet that competed with the early 777s the MD 11.
It will forever be a McDonnell Douglas MD 80 , Boeing MD 80 sounds so wrong
 
HT
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RE: What If There Was A Trijet Built Off The 777 T

Sun Sep 14, 2008 4:21 pm



Quoting Andz (Reply 2):
Imagine a GE-90 in the tail, that would be outrageous!

It also would add an enourmous weight to the tail of the a/c.

Isn't it the case that a MD-11F (and the DC-10/MD-10F's) need to be loaded / unloaded carefully in order to keep the Center of Gravity within the triangle made up by the landing gear (i.e. to prevent that the a/c's nose ponts high in the air while it rests on its aft section) ?
-HT
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wilco737
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RE: What If There Was A Trijet Built Off The 777 T

Mon Sep 15, 2008 5:36 am



Quoting HT (Reply 7):
Isn't it the case that a MD-11F (and the DC-10/MD-10F's) need to be loaded / unloaded carefully in order to keep the Center of Gravity within the triangle made up by the landing gear (i.e. to prevent that the a/c's nose ponts high in the air while it rests on its aft section) ?

Yes, you need to be careful. And on ferry flights you need a lot of ballast fuel to keep her in trim as well and make her flyable.

3 engines made sense when we had only a small amount of ETOPS, where it was not possible to fly across the north atlantic with only 2 engines. McDonnell had the idea to put the 3rd engine on the tail to fly across the pond. Nowadays with such high ETOPS, you don't need it anymore. Although I remember a thread not too long ago where Airbus is in plans (or thinking) about an aircraft with 3 engines.

WILCO737 (MD11F)
 airplane 
 
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Starlionblue
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RE: What If There Was A Trijet Built Off The 777 Tec?

Mon Sep 15, 2008 9:49 am

WILCO737 has it right. The triplet came about from a particular set of requirements at a particular time. Nowadays you'd just stay at 2 (777, 350) or go to 4 (380).

Quoting HT (Reply 7):
Isn't it the case that a MD-11F (and the DC-10/MD-10F's) need to be loaded / unloaded carefully in order to keep the Center of Gravity within the triangle made up by the landing gear (i.e. to prevent that the a/c's nose ponts high in the air while it rests on its aft section) ?

This is true. But there are plenty of pics in the database of 747s sitting on their tails as well.

Trijets (and tail engined aircraft) have the wings and gear further back, thus solving some of the weight distribution issue.

Quoting WILCO737 (Reply 8):
3 engines made sense when we had only a small amount of ETOPS, where it was not possible to fly across the north atlantic with only 2 engines. McDonnell had the idea to put the 3rd engine on the tail to fly across the pond. Nowadays with such high ETOPS, you don't need it anymore. Although I remember a thread not too long ago where Airbus is in plans (or thinking) about an aircraft with 3 engines.

The one with the split tail. Yeah that was cool.
"There are no stupid questions, but there are a lot of inquisitive idiots." - John Ringo
 
Alessandro
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RE: What If There Was A Trijet Built Off The 777 Tec?

Mon Sep 15, 2008 3:57 pm

Hmm, I´m not sure that the DC-10 and Tristar was meant as twin engined first. Later the company
worked on a Bistar, but it never made it.
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Alessandro
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RE: What If There Was A Trijet Built Off The 777 Tec?

Mon Sep 15, 2008 4:02 pm



Quoting HT (Reply 7):
Quoting Andz (Reply 2):
Imagine a GE-90 in the tail, that would be outrageous!

It also would add an enourmous weight to the tail of the a/c.

Isn't it the case that a MD-11F (and the DC-10/MD-10F's) need to be loaded / unloaded carefully in order to keep the Center of Gravity within the triangle made up by the landing gear (i.e. to prevent that the a/c's nose ponts high in the air while it rests on its aft section) ?
-HT

Well, if an imaginary 3 engined aircraft would´ve been made like that, I would´ve suggested a
supportwheel like the Il-62 got, for parking the aircraft.
From New Yorqatar to Califarbia...
 
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Starlionblue
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RE: What If There Was A Trijet Built Off The 777 Tec?

Mon Sep 15, 2008 11:48 pm



Quoting Alessandro (Reply 10):
Hmm, I´m not sure that the DC-10 and Tristar was meant as twin engined first. Later the company
worked on a Bistar, but it never made it.

As you say it was the other way round. They were triplets first.

IIRC there was a LGA requirement that necessitated certain take-off performance with certain range. The only way to do that with the engines at the time was to install three.
"There are no stupid questions, but there are a lot of inquisitive idiots." - John Ringo
 
tdscanuck
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RE: What If There Was A Trijet Built Off The 777 Tec?

Tue Sep 16, 2008 6:05 am



Quoting 747400sp (Thread starter):
I was wondering, if there was an aircraft company that designed a band new plane around the same time the T-7 was design, but it was a trijet using the same engines as T-7 has, want do you think would become of that airliner?

Well, it would either be *massively* overpowered or need a takeoff weight greater than an A380.

With three 777 engines, you're talking an engine-out thrust of 230000 lbs. That's comparable to what an A380 has, and far more than a 777 or 747. So you're either packing around a *lot* more engine than you need (with related weight and fuel burn penalties) or you're talking about a very very big aircraft, so big that there's probably not enough market to justify it.

Tom.
 
ovrpowrd727
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RE: What If There Was A Trijet Built Off The 777 Tec?

Fri Sep 19, 2008 3:57 am



Quoting Andz (Reply 2):
Imagine a GE-90 in the tail, that would be outrageous!

im sure the trents would look funny too, it sux that in today's day you wouldn't see it, i have spoken to a few MD-11 pilots, specifically RG and AY and the airframe is pilot friendly... they both agreed that the power and range are not sacrificed because of load factors to a degree, the MD-11 is actually very capable, wasn't there a plan to stretch the Md-11 once more but it was scrapped because Mcdonnell Douglas went under?? aside from maintenance a tri-jet can be very durable
 
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Starlionblue
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RE: What If There Was A Trijet Built Off The 777 Tec?

Fri Sep 19, 2008 4:06 am



Quoting Ovrpowrd727 (Reply 14):
wasn't there a plan to stretch the Md-11 once more but it was scrapped because Mcdonnell Douglas went under??

There was indeed:

http://rosboch.net/aviationmedia/Proposed_MD-XX_MD-12_trijet.jpg

I should be noted that the tail engine mounting is a very costly engineering challenge. Bigger fans make the cost grow very fast.
"There are no stupid questions, but there are a lot of inquisitive idiots." - John Ringo
 
wn700driver
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RE: What If There Was A Trijet Built Off The 777 Tec?

Fri Sep 19, 2008 7:50 am



Quote:

With three 777 engines, you're talking an engine-out thrust of 230000 lbs. That's comparable to what an A380 has, and far more than a 777 or 747. So you're either packing around a *lot* more engine than you need (with related weight and fuel burn penalties) or you're talking about a very very big aircraft, so big that there's probably not enough market to justify it.

Quite relevant. A bit off topic, but along those lines, I have often wondered why the 747-8 is remaining a quad. I realize its a bit heavier than a 77W, but is it so much so that four smaller units are better than what the two 77W or 77L packs? I guess it makes more difference with the cargo ops, but I can't see very many segments out there where the extra few percent of power or 200-300km of range really makes that much difference.
Of course for Boeing to do that they would need a new wing, but weren't they doing that anyway? Just something I've been thinking about here & there. . .
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Starlionblue
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RE: What If There Was A Trijet Built Off The 777 Tec?

Fri Sep 19, 2008 9:57 am



Quoting WN700Driver (Reply 16):
Quite relevant. A bit off topic, but along those lines, I have often wondered why the 747-8 is remaining a quad. I realize its a bit heavier than a 77W, but is it so much so that four smaller units are better than what the two 77W or 77L packs? I guess it makes more difference with the cargo ops, but I can't see very many segments out there where the extra few percent of power or 200-300km of range really makes that much difference.
Of course for Boeing to do that they would need a new wing, but weren't they doing that anyway? Just something I've been thinking about here & there. . .

The MTOW of the 747-8 will be 970,000 lb. The MTOW of the 777-300ER is 775,000 lb. So it's not a few percent extra.

The 747-8 will be powered by the GEnx-2B67 at 66500 lb/f of thrust. That's 199500 with an engine out. To make it a twin you'd need 200k thrust engines (200k with an engine out). That's about 75% more power than the current most powerful engine.
"There are no stupid questions, but there are a lot of inquisitive idiots." - John Ringo
 
2H4
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RE: What If There Was A Trijet Built Off The 777 Tec?

Fri Sep 19, 2008 1:06 pm



Quoting WN700Driver (Reply 16):
Of course for Boeing to do that they would need a new wing, but weren't they doing that anyway?

They'd need all new systems, too, would they not? Hydraulic, pneumatic, electrical, fire protection....all of it would have to be reengineered and rerouted to the new configuration.

Then, the certification would require full flight test in every flight regime, whereas (I assume) the 747-8 can get away with significantly less testing, as the airframe and aerodynamic changes are comparatively minimal.

2H4
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ovrpowrd727
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RE: What If There Was A Trijet Built Off The 777 Tec?

Fri Sep 19, 2008 1:08 pm

why can't the freighters pick it up?? they hardly use the planes already in service to their full potential anyway there's no call for it... freight revenue and pax revenue are two different things completely, c'mon when are you going to see MD-11's doing domestic flight unless its freight

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