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What If There Was A Trijet Built Off The 777 Tec?  
User currently offline747400sp From United States of America, joined Aug 2003, 3649 posts, RR: 2
Posted (6 years 2 weeks 6 days 2 hours ago) and read 7987 times:

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?

19 replies: All unread, jump to last
 
User currently offlineJcchristie From United States of America, joined Nov 2006, 39 posts, RR: 0
Reply 1, posted (6 years 2 weeks 5 days 20 hours ago) and read 7970 times:

I would think it would fail. Why have 3 engines when you do just fine with 2?

User currently offlineAndz From South Africa, joined Feb 2004, 8455 posts, RR: 10
Reply 2, posted (6 years 2 weeks 5 days 20 hours ago) and read 7968 times:
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Imagine a GE-90 in the tail, that would be outrageous!


After Monday and Tuesday even the calendar says WTF...
User currently offlineAcNDTTech From United States of America, joined Jul 2008, 338 posts, RR: 0
Reply 3, posted (6 years 2 weeks 5 days 11 hours ago) and read 7944 times:



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?


User currently offlineDfwRevolution From United States of America, joined Jan 2010, 979 posts, RR: 51
Reply 4, posted (6 years 2 weeks 5 days 10 hours ago) and read 7936 times:



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.


User currently offlineRussianJet From Belgium, joined Jul 2007, 7704 posts, RR: 21
Reply 5, posted (6 years 2 weeks 5 days 8 hours ago) and read 7918 times:
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Man, it would look cool though.


✈ Every strike of the hammer is a blow against the enemy. ✈
User currently offlineColumba From Germany, joined Dec 2004, 7073 posts, RR: 4
Reply 6, posted (6 years 2 weeks 4 days 20 hours ago) and read 7877 times:



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
User currently offlineHT From Germany, joined May 2005, 6525 posts, RR: 23
Reply 7, posted (6 years 2 weeks 4 days 11 hours ago) and read 7855 times:



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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User currently offlineWILCO737 From Greenland, joined Jun 2004, 9069 posts, RR: 76
Reply 8, posted (6 years 2 weeks 3 days 22 hours ago) and read 7816 times:
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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 



It it's not Boeing, I am not going.
User currently offlineStarlionblue From Greenland, joined Feb 2004, 17056 posts, RR: 67
Reply 9, posted (6 years 2 weeks 3 days 18 hours ago) and read 7768 times:

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."
User currently offlineAlessandro From , joined Dec 1969, posts, RR:
Reply 10, posted (6 years 2 weeks 3 days 12 hours ago) and read 7682 times:

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.


User currently offlineAlessandro From , joined Dec 1969, posts, RR:
Reply 11, posted (6 years 2 weeks 3 days 12 hours ago) and read 7681 times:



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.


User currently offlineStarlionblue From Greenland, joined Feb 2004, 17056 posts, RR: 67
Reply 12, posted (6 years 2 weeks 3 days 4 hours ago) and read 7553 times:



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."
User currently offlineTdscanuck From Canada, joined Jan 2006, 12709 posts, RR: 80
Reply 13, posted (6 years 2 weeks 2 days 22 hours ago) and read 7498 times:



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.


User currently offlineOvrpowrd727 From United States of America, joined Sep 2008, 96 posts, RR: 0
Reply 14, posted (6 years 2 weeks ago) and read 7255 times:



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


User currently offlineStarlionblue From Greenland, joined Feb 2004, 17056 posts, RR: 67
Reply 15, posted (6 years 2 weeks ago) and read 7252 times:



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."
User currently offlineWN700Driver From , joined Dec 1969, posts, RR:
Reply 16, posted (6 years 1 week 6 days 20 hours ago) and read 7220 times:



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. . .


User currently offlineStarlionblue From Greenland, joined Feb 2004, 17056 posts, RR: 67
Reply 17, posted (6 years 1 week 6 days 18 hours ago) and read 7198 times:



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."
User currently offline2H4 From United States of America, joined Oct 2004, 8955 posts, RR: 60
Reply 18, posted (6 years 1 week 6 days 15 hours ago) and read 7174 times:
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DATABASE EDITOR



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



Intentionally Left Blank
User currently offlineOvrpowrd727 From United States of America, joined Sep 2008, 96 posts, RR: 0
Reply 19, posted (6 years 1 week 6 days 15 hours ago) and read 7171 times:

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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