United Airline
Topic Author
Posts: 8771
Joined: Wed Jan 10, 2001 5:24 pm

Is It Possible To Make A Twin Engined B 747?

Fri Nov 18, 2005 4:25 am

Is it? I know they tried to make a B 747SP with 3 engines but at the end the plan was scrapped. What about a twin engined B 747? Is it possible? If it is, the operating cost will be a lot lower.
 
kiwiandrew

RE: Is It Possible To Make A Twin Engined B 747?

Fri Nov 18, 2005 4:27 am

Quoting United Airline (Thread starter):
Is it? I know they tried to make a B 747SP with 3 engines but at the end the plan was scrapped. What about a twin engined B 747? Is it possible? If it is, the operating cost will be a lot lower.

OK - old joke I know and I am wearing my asbestos suit waiting to be flamed ........


.... but doesn't BA run 3-engined 744's ?
 
Spruit
Posts: 367
Joined: Fri Oct 28, 2005 12:34 am

RE: Is It Possible To Make A Twin Engined B 747?

Fri Nov 18, 2005 4:29 am

I believe this is a thrust to weight issue, so IMHO no!

Not until they develop more powerful engines, but then I believe you'll have the size on the wing issues causing drag etc etc!

Any more thoughts would be interesting!

 Confused
E=Mc2
 
DAYflyer
Posts: 3546
Joined: Wed Sep 08, 2004 9:35 pm

RE: Is It Possible To Make A Twin Engined B 747?

Fri Nov 18, 2005 4:30 am

Quoting Kiwiandrew (Reply 1):
.... but doesn't BA run 3-engined 744's ?

Priceless....  laughing   laughing 
One Nation Under God
 
lehpron
Posts: 6846
Joined: Tue Jul 10, 2001 3:42 am

RE: Is It Possible To Make A Twin Engined B 747?

Fri Nov 18, 2005 4:59 am

Hello, do realize how large 773 was to the 747? I think it killed pax orders for 744's.
The meaning of life is curiosity; we were put on this planet to explore opportunities.
 
KELPkid
Posts: 5247
Joined: Wed Nov 02, 2005 5:33 am

RE: Is It Possible To Make A Twin Engined B 747?

Fri Nov 18, 2005 5:22 am

Quoting Kiwiandrew (Reply 1):
OK - old joke I know and I am wearing my asbestos suit waiting to be flamed ........


.... but doesn't BA run 3-engined 744's ?


Wasn't there a (cargo) 747 that (physically-as in fell off) lost two engines on side after takeoff from ANC, and then returned to land safely?

 rotfl   rotfl   rotfl   rotfl 

Now THAT'S a Twin-engined 747!!!
Celebrating the birth of KELPkidJR on August 5, 2009 :-)
 
User avatar
zippyjet
Posts: 5089
Joined: Tue Sep 04, 2001 3:32 pm

RE: Is It Possible To Make A Twin Engined B 747?

Fri Nov 18, 2005 5:27 am

Quoting KELPkid (Reply 5):
Wasn't there a (cargo) 747 that (physically-as in fell off) lost two engines on side after takeoff from ANC, and then returned to land safely?

I love humorous reply's. Back on a serious note, anything's possible with enough R &D and money it can be done but why? Much of the flying public though out of the loop airliner wise would percieve this as a cheap underpowered bird. Akin to putting a 73 horse power 4 cylinder engine in a fully loaded Cadillac Escalade.
I'm Zippyjet & I approve of this message!
 
User avatar
Stitch
Posts: 23203
Joined: Wed Jul 06, 2005 4:26 am

RE: Is It Possible To Make A Twin Engined B 747?

Fri Nov 18, 2005 5:58 am

Would a GE90-115B engine physically clear if slung under a 747 wing? The combined thrust rating of two of those is within the ballpark (~10-15,000lbs) of four RB 211s/PW 4062s/GE CF6s.
 
NYC777
Posts: 5076
Joined: Wed Jun 09, 2004 3:00 am

RE: Is It Possible To Make A Twin Engined B 747?

Fri Nov 18, 2005 6:06 am

You would need an engine that produces at least 150,000 lbs of thrust for a twin engined 747. Don't think that's happenening anytime soon.
That which does not kill me makes me stronger.
 
akelley728
Posts: 1965
Joined: Tue Dec 07, 1999 12:35 pm

RE: Is It Possible To Make A Twin Engined B 747?

Fri Nov 18, 2005 6:09 am

Quoting Stitch (Reply 7):
Would a GE90-115B engine physically clear if slung under a 747 wing? The combined thrust rating of two of those is within the ballpark (~10-15,000lbs) of four RB 211s/PW 4062s/GE CF6s.

Yep...


View Large View Medium
Click here for bigger photo!

Photo © Jet City Aviation Photography



View Large View Medium
Click here for bigger photo!

Photo © Je89 W.



View Large View Medium
Click here for bigger photo!

Photo © Je89 W.

 
pilottj
Posts: 274
Joined: Fri Nov 19, 2004 1:23 pm

RE: Is It Possible To Make A Twin Engined B 747?

Fri Nov 18, 2005 1:22 pm

I suppose only airplane geeks like us would find the humor of the GE 747 testbed using 1,3,4 PW engines.

Cheers
TJ
God was my copilot, but we crashed in the mountains and I had to eat him...
 
sllevin
Posts: 3312
Joined: Wed Jan 30, 2002 1:57 pm

RE: Is It Possible To Make A Twin Engined B 747?

Fri Nov 18, 2005 1:47 pm

Quoting Stitch (Reply 7):
Would a GE90-115B engine physically clear if slung under a 747 wing? The combined thrust rating of two of those is within the ballpark (~10-15,000lbs) of four RB 211s/PW 4062s/GE CF6s.

True, but like everything in aviation, it's all about wht happens when one engine fails. That's when you get into trouble with the 74-Twin, because it wouldn't perform too happily...

Now, 4 GE90-115's...that's be something. However, on takeoff, that thing would probably suck in FOD from other states!  Smile

Steve
 
User avatar
zeke
Posts: 9919
Joined: Thu Dec 14, 2006 1:42 pm

RE: Is It Possible To Make A Twin Engined B 747?

Fri Nov 18, 2005 3:06 pm

The 747 would have to be structurally a lot heavier if it were a twin, the outboard engines on any quad provide positive bending moment relief allowing the wing/wing box to be structurally lighter. Having a quad allows for a smaller rudder, if it were a twin it would need a larger rudder, increasing drag, and in creasing weight not only of the vertical stabilizer, also that of the fuselage from the tail to the wing box.
We are addicted to our thoughts. We cannot change anything if we cannot change our thinking – Santosh Kalwar
 
ikramerica
Posts: 13772
Joined: Mon May 23, 2005 9:33 am

RE: Is It Possible To Make A Twin Engined B 747?

Fri Nov 18, 2005 3:27 pm

And with current engine technology, it would need 3xGE90 engines at 100,000 lbs, because the 748 uses 4 66,000 lbs engines, so 1 engine out is 200,000, which they must have determined to be the required safe minimum lift for a safe takeoff.

A 3 engine 747 would look kind of funny, with two on one side and one on the other, as there's no way you're putting a GE90-100 up in the tail.

Alternatively, you'd need a lighter frame and/or an engine capable of at least 180,000 lbs.

Which is why the "Big-Twin" is still a long way off. It needs a very good wing, a very light structure, and very powerful engines.
Of all the things to worry about... the Wookie has no pants.
 
GQfluffy
Posts: 3072
Joined: Tue Apr 19, 2005 1:25 pm

RE: Is It Possible To Make A Twin Engined B 747?

Fri Nov 18, 2005 3:33 pm

I seem to remember you asking about this before.... Think you recieved the same response....
This isn't where I parked my car...
 
United Airline
Topic Author
Posts: 8771
Joined: Wed Jan 10, 2001 5:24 pm

RE: Is It Possible To Make A Twin Engined B 747?

Fri Nov 18, 2005 4:02 pm

Wonder if anyone would ever build a twin engined jumbo/superjumbo

Quoting Lehpron (Reply 4):
Hello, do realize how large 773 was to the 747? I think it killed pax orders for 744's.

Smaller still.
 
QFA380
Posts: 2013
Joined: Fri Jul 22, 2005 4:38 pm

RE: Is It Possible To Make A Twin Engined B 747?

Fri Nov 18, 2005 4:37 pm

Quoting NYC777 (Reply 8):
You would need an engine that produces at least 150,000 lbs of thrust for a twin engined 747. Don't think that's happenening anytime soon.

It may be a long way away but wouldn't it be cool to have an engine that size. GE 90's are massive enough, this would just be incredible. One could probably put an A330 fuselage through the engineand spit it out into billions of pieces. I definately wouldn't like to be caught in the jet blast of that baby on take-off.

QFA380
 
zvezda
Posts: 8891
Joined: Sat Aug 28, 2004 8:48 pm

RE: Is It Possible To Make A Twin Engined B 747?

Fri Nov 18, 2005 5:23 pm

It would be possible to build a twin the size of the B747, but it wouldn't be a B747. With a composite fuselage, it could be light enough to use a pair of GE-90s (probably at about 125,000 lbs. of thrust each).
 
User avatar
HAWK21M
Posts: 29867
Joined: Fri Jan 05, 2001 10:05 pm

RE: Is It Possible To Make A Twin Engined B 747?

Fri Nov 18, 2005 6:38 pm

Quoting Kiwiandrew (Reply 1):
but doesn't BA run 3-engined 744's


regds
MEL
I may not win often, but I damn well never lose!!! ;)
 
User avatar
Starlionblue
Posts: 17115
Joined: Fri Feb 27, 2004 9:54 pm

RE: Is It Possible To Make A Twin Engined B 747?

Fri Nov 18, 2005 11:12 pm

Quoting Ikramerica (Reply 13):
A 3 engine 747 would look kind of funny, with two on one side and one on the other, as there's no way you're putting a GE90-100 up in the tail.

Boeing did toy with a 3 holer 747:

http://www.rosboch.net/various/B747-300_Concept_with_three_engines.jpg

Quoting Zvezda (Reply 17):
It would be possible to build a twin the size of the B747, but it wouldn't be a B747. With a composite fuselage, it could be light enough to use a pair of GE-90s (probably at about 125,000 lbs. of thrust each).

Don't forget the entirely new wing they would have to build.
"There are no stupid questions, but there are a lot of inquisitive idiots." - John Ringo
 
Boeing Nut
Posts: 5078
Joined: Fri Feb 23, 2001 2:42 am

RE: Is It Possible To Make A Twin Engined B 747?

Sat Nov 19, 2005 1:41 am

Quoting United Airline (Thread starter):
Is It Possible To Make A Twin Engined B 747?

Hell yea it is, they've been flying for a while now!!!!


Modified Airliner Photos:
Click here for bigger photo!
Design © Fu Ling Yu
Template © Curtis Hedlund




Modified Airliner Photos:
Click here for bigger photo!
Design © Robert Fall
Template © Daniel & Robert Fall




Geeze people, wake up!!!

 rotfl 
I'm not a real aeronautical engineer, I just play one on Airliners.net.
 
User avatar
lightsaber
Crew
Posts: 11857
Joined: Wed Jan 19, 2005 10:55 pm

RE: Is It Possible To Make A Twin Engined B 747?

Sat Nov 19, 2005 2:35 am

Quoting Ikramerica (Reply 13):
Alternatively, you'd need a lighter frame and/or an engine capable of at least 180,000 lbs.

 checkmark  We have a winner! The 747 needs 180,000 lbf of thrust with an engine out. Thus, three engines of 62,000 lbf or one of ~180,000lbf. Most engine manufacturers are unable to build an engine beyond 150,000lbf. The jump in technology to get to 180,000lbf just isn't there today.

Quoting Zvezda (Reply 17):
It would be possible to build a twin the size of the B747, but it wouldn't be a B747. With a composite fuselage, it could be light enough to use a pair of GE-90s (probably at about 125,000 lbs. of thrust each).

Now there is an idea...  spin  But this wouldn't be a 747, it would be a 787-12.  duck 

Quoting Kiwiandrew (Reply 1):

.... but doesn't BA run 3-engined 744's ?

 rotfl  Poor BA... its going to be like B6 and nose gear, famous for that "oops" for a bit.

Lightsaber
"They did not know it was impossible, so they did it!" - Mark Twain
 
2H4
Posts: 7960
Joined: Tue Oct 19, 2004 11:11 pm

RE: Is It Possible To Make A Twin Engined B 747?

Sat Nov 19, 2005 3:18 am




Quoting Starlionblue (Reply 19):
Don't forget the entirely new wing they would have to build.



...And the fact that most of the existing systems (pneumatic, hydraulic, electrical, etc.) would have to all be pulled out, re-engineered from scratch, re-installed, re-tested, and re-certified.

It would almost certainly be more economical to simply purchase another airplane.




2H4


Intentionally Left Blank
 
User avatar
Starlionblue
Posts: 17115
Joined: Fri Feb 27, 2004 9:54 pm

RE: Is It Possible To Make A Twin Engined B 747?

Sat Nov 19, 2005 6:59 am

Quoting Lightsaber (Reply 21):
Quoting Ikramerica (Reply 13):
Alternatively, you'd need a lighter frame and/or an engine capable of at least 180,000 lbs.

checkmark We have a winner! The 747 needs 180,000 lbf of thrust with an engine out. Thus, three engines of 62,000 lbf or one of ~180,000lbf. Most engine manufacturers are unable to build an engine beyond 150,000lbf. The jump in technology to get to 180,000lbf just isn't there today.

Sure, if you want to rip the wing off  Wink As 2H4 points out, it's not only the wing but "all that other stuff".
"There are no stupid questions, but there are a lot of inquisitive idiots." - John Ringo
 
User avatar
lightsaber
Crew
Posts: 11857
Joined: Wed Jan 19, 2005 10:55 pm

RE: Is It Possible To Make A Twin Engined B 747?

Sat Nov 19, 2005 7:49 am

Quoting Starlionblue (Reply 23):
Sure, if you want to rip the wing off

 checkmark  Hey, as long as my engine works! Structures isn't my job.  spin 

Lightsaber
"They did not know it was impossible, so they did it!" - Mark Twain
 
prebennorholm
Posts: 6430
Joined: Tue Mar 21, 2000 6:25 am

RE: Is It Possible To Make A Twin Engined B 747?

Sat Nov 19, 2005 9:02 am

A twin 747 would do beautifully. In fact an old 747-100 would gain performance having its four PW JT9D-70A exchanged with two GE90-115B.

But a 747-400 would be severely limited in gross weight to max roughly 700,000 lbs with two engines as weak as the -115B.

A twin should not have a thrust to weight ratio much exceeding 6 with one engine going inop after V1. It's all about weight.

A 747-400 taking off at 700k lbs would be cheap to fuel, but it wouln't fly very far compared to the real thing.

A twin 747-400 which should match an ordinary 747-400 should have something like 150k lbs engines.

Quoting Lightsaber (Reply 21):
The 747 needs 180,000 lbf of thrust with an engine out. Thus, three engines of 62,000 lbf or one of ~180,000lbf.

Not entirely correct. Remember that a twin always have two good engines all way up to V1 speed, and therefore accellerates faster than a quad to V1 speed. Roughly 150k would be enough.
Always keep your number of landings equal to your number of take-offs
 
User avatar
Starlionblue
Posts: 17115
Joined: Fri Feb 27, 2004 9:54 pm

RE: Is It Possible To Make A Twin Engined B 747?

Sat Nov 19, 2005 9:21 am

Quoting Prebennorholm (Reply 25):
Not entirely correct. Remember that a twin always have two good engines all way up to V1 speed, and therefore accellerates faster than a quad to V1 speed. Roughly 150k would be enough.

Or you could just bring back good old RATO Big grin
"There are no stupid questions, but there are a lot of inquisitive idiots." - John Ringo
 
User avatar
lightsaber
Crew
Posts: 11857
Joined: Wed Jan 19, 2005 10:55 pm

RE: Is It Possible To Make A Twin Engined B 747?

Sat Nov 19, 2005 9:52 am

Quoting Prebennorholm (Reply 25):
Not entirely correct. Remember that a twin always have two good engines all way up to V1 speed, and therefore accellerates faster than a quad to V1 speed. Roughly 150k would be enough.

Good point. I oversimplified. So with less runway "eaten up" to get to V1, there is more runway left to acheive flight.

But I want to design that 180k engine!  hyper 

A GTF, of course.  bigthumbsup 

Lightsaber

ps
I really hope the next "megaplane" is a BWB. But then again, I'm an aero winnie. Someone else has to figure out the evacuation.  spin 

Quoting Starlionblue (Reply 26):


Or you could just bring back good old RATO

Don't laugh. Its been studied for the 744. I kid you not.
"They did not know it was impossible, so they did it!" - Mark Twain
 
FTOHIST
Posts: 72
Joined: Sat Mar 06, 2004 2:20 pm

RE: Is It Possible To Make A Twin Engined B 747?

Sat Nov 19, 2005 10:04 am

Quoting Pilottj (Reply 10):
I suppose only airplane geeks like us would find the humor of the GE 747 testbed using 1,3,4 PW engines.

Not when you're one of the people who work on that airplane!!!!!!  Wink
 
User avatar
Starlionblue
Posts: 17115
Joined: Fri Feb 27, 2004 9:54 pm

RE: Is It Possible To Make A Twin Engined B 747?

Sun Nov 20, 2005 10:24 am

Quoting Lightsaber (Reply 27):
Quoting Starlionblue (Reply 26):


Or you could just bring back good old RATO

Don't laugh. Its been studied for the 744. I kid you not.

I'm not surprised, but I'm still laughing Big grin
"There are no stupid questions, but there are a lot of inquisitive idiots." - John Ringo
 
dw747400
Posts: 1091
Joined: Wed Aug 15, 2001 8:24 am

RE: Is It Possible To Make A Twin Engined B 747?

Sun Nov 20, 2005 12:42 pm

The 777-300ER has a MTOW considerably higher than that of the 747-100. Obviously, a major redesign would be needed, and I'm not sure how much additional drag the 741 produces compared to a 773, but from a MTOW standpoint, we already have a twin in the 747 class.
CFI--Certfied Freakin Idiot
 
User avatar
Starlionblue
Posts: 17115
Joined: Fri Feb 27, 2004 9:54 pm

RE: Is It Possible To Make A Twin Engined B 747?

Sun Nov 20, 2005 2:40 pm

Quoting Dw747400 (Reply 30):
The 777-300ER has a MTOW considerably higher than that of the 747-100. Obviously, a major redesign would be needed, and I'm not sure how much additional drag the 741 produces compared to a 773, but from a MTOW standpoint, we already have a twin in the 747 class.

Quite true.

The big question now is if Boeing's next gen large platform to replace the 747 and 777 (sometimes referred to as Yellowstone 3 or Y3) will be a twin. My guess is yes. But the related question is how far can you go with a twin with current technology. You could probably make a 744 class twin in a few years if (and it's a big if) the engines are powerful enough. However there's a problem with the investment for such engine development. Just as with the 380, you hit a point where additional investment is very high for a smaller and smaller market.
"There are no stupid questions, but there are a lot of inquisitive idiots." - John Ringo
 
prebennorholm
Posts: 6430
Joined: Tue Mar 21, 2000 6:25 am

RE: Is It Possible To Make A Twin Engined B 747?

Mon Nov 21, 2005 5:17 am

Quoting Starlionblue (Reply 26):
Or you could just bring back good old RATO

Operationally, not a bad idea at all - in fact a very good idea. Carrying some emergency bottles in the main gear well instead of building ever more overpowered twins for the ever more rare occation when it has to take off on one engine, it might make economic sense.

But for safety reasons...? When an airliner slips off the runway, gear is ripped off etc, fuel leakes all over the place, emergency slides are inflated, then self-igniting of a damaged RATO bottle is probably the last thing you would want.
Always keep your number of landings equal to your number of take-offs
 
User avatar
Stitch
Posts: 23203
Joined: Wed Jul 06, 2005 4:26 am

RE: Is It Possible To Make A Twin Engined B 747?

Wed Nov 23, 2005 4:28 am

An all-composite, all-electrical, bleedless twin VLA would be something to see...
 
User avatar
Starlionblue
Posts: 17115
Joined: Fri Feb 27, 2004 9:54 pm

RE: Is It Possible To Make A Twin Engined B 747?

Wed Nov 23, 2005 1:12 pm

Quoting Stitch (Reply 33):
An all-composite, all-electrical, bleedless twin VLA would be something to see...

In my view this whole discussions illustrates the problem with airliner design today. There's very little out of the box thinking. It's basically all refining a tube with wings. While I understand the reason why, I can't help but think that designers can do better. Dick Rutan certainly proves this regularly even though he isn't in the airliner business. My fear is that airframers have so much invested in the current state of the art (a tube with wings) that it will be hard to break the constraints once we start reaching the limits of the design.

As the 80mx80m box limitation at airports shows, or the difficulty in actually making a product just a little bit better, we may be reaching the limits of the current planform. Who will come out on top when the customers say: "Ok, now we need a plane to tak 800 tons of cargo or 1200 pax". Or "We need to go from London to New York in 2 hours". I'm not saying that these things will ever come to pass, but if they do, that will be one expensive development hurdle...

Ok, getting off my soapbox now.
"There are no stupid questions, but there are a lot of inquisitive idiots." - John Ringo
 
zvezda
Posts: 8891
Joined: Sat Aug 28, 2004 8:48 pm

RE: Is It Possible To Make A Twin Engined B 747?

Sun Nov 27, 2005 2:01 am

Quoting Starlionblue (Reply 19):
Don't forget the entirely new wing they would have to build.



Quoting 2H4 (Reply 22):
...And the fact that most of the existing systems (pneumatic, hydraulic, electrical, etc.) would have to all be pulled out, re-engineered from scratch, re-installed, re-tested, and re-certified.

That's why I wrote "... a twin the size of the B747," and not "a twin B747."

Quoting Starlionblue (Reply 31):
The big question now is if Boeing's next gen large platform to replace the 747 and 777 (sometimes referred to as Yellowstone 3 or Y3) will be a twin. My guess is yes. But the related question is how far can you go with a twin with current technology. You could probably make a 744 class twin in a few years if (and it's a big if) the engines are powerful enough. However there's a problem with the investment for such engine development. Just as with the 380, you hit a point where additional investment is very high for a smaller and smaller market.

I'm confident that Y3 will be a twin. The launch of the B747-8 means that Boeing have about ten years before they need to launch Y3. By that time, it should be easy enough to develop a 125K+ thrust engine. And by that time, the GEnx and Trent 1000 will no longer be up-to-date technology.

Who is online

Users browsing this forum: No registered users and 7 guests