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Is It Possible To Make A Twin Engined B 747?  
User currently offlineUnited Airline From Hong Kong, joined Jan 2001, 9191 posts, RR: 15
Posted (9 years 1 week 3 days 10 hours ago) and read 6343 times:

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.

35 replies: All unread, showing first 25:
 
User currently offlineKiwiandrew From New Zealand, joined Jun 2005, 8602 posts, RR: 13
Reply 1, posted (9 years 1 week 3 days 10 hours ago) and read 6331 times:
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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 ?



Moderation in all things ... including moderation ;-)
User currently offlineSpruit From United Kingdom, joined Oct 2005, 375 posts, RR: 0
Reply 2, posted (9 years 1 week 3 days 10 hours ago) and read 6310 times:

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
User currently offlineDAYflyer From United States of America, joined Sep 2004, 3807 posts, RR: 3
Reply 3, posted (9 years 1 week 3 days 10 hours ago) and read 6304 times:

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

Priceless....  laughing   laughing 



One Nation Under God
User currently offlineLehpron From United States of America, joined Jul 2001, 7028 posts, RR: 21
Reply 4, posted (9 years 1 week 3 days 9 hours ago) and read 6217 times:

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.
User currently offlineKELPkid From United States of America, joined Nov 2005, 6428 posts, RR: 3
Reply 5, posted (9 years 1 week 3 days 9 hours ago) and read 6155 times:

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 currently offlineZippyjet From United States of America, joined Sep 2001, 5501 posts, RR: 13
Reply 6, posted (9 years 1 week 3 days 9 hours ago) and read 6129 times:

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.



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User currently offlineStitch From United States of America, joined Jul 2005, 31249 posts, RR: 85
Reply 7, posted (9 years 1 week 3 days 8 hours ago) and read 6034 times:
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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.

User currently offlineNYC777 From United States of America, joined Jun 2004, 5796 posts, RR: 47
Reply 8, posted (9 years 1 week 3 days 8 hours ago) and read 5988 times:

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.
User currently offlineAKelley728 From United States of America, joined Dec 1999, 2194 posts, RR: 5
Reply 9, posted (9 years 1 week 3 days 8 hours ago) and read 5976 times:

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...


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User currently offlinePilottj From United States of America, joined Nov 2004, 279 posts, RR: 0
Reply 10, posted (9 years 1 week 3 days 1 hour ago) and read 5747 times:

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...
User currently offlineSllevin From United States of America, joined Jan 2002, 3376 posts, RR: 6
Reply 11, posted (9 years 1 week 3 days ago) and read 5694 times:

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 currently offlineZeke From Hong Kong, joined Dec 2006, 9210 posts, RR: 76
Reply 12, posted (9 years 1 week 2 days 23 hours ago) and read 5621 times:

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
User currently offlineIkramerica From United States of America, joined May 2005, 21562 posts, RR: 59
Reply 13, posted (9 years 1 week 2 days 23 hours ago) and read 5590 times:

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.
User currently offlineGQfluffy From , joined Dec 1969, posts, RR:
Reply 14, posted (9 years 1 week 2 days 23 hours ago) and read 5583 times:

I seem to remember you asking about this before.... Think you recieved the same response....

User currently offlineUnited Airline From Hong Kong, joined Jan 2001, 9191 posts, RR: 15
Reply 15, posted (9 years 1 week 2 days 22 hours ago) and read 5546 times:

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.


User currently offlineQFA380 From Australia, joined Jul 2005, 2081 posts, RR: 1
Reply 16, posted (9 years 1 week 2 days 21 hours ago) and read 5496 times:

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


User currently offlineZvezda From Lithuania, joined Aug 2004, 10511 posts, RR: 64
Reply 17, posted (9 years 1 week 2 days 21 hours ago) and read 5451 times:

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 currently offlineHAWK21M From India, joined Jan 2001, 31702 posts, RR: 56
Reply 18, posted (9 years 1 week 2 days 19 hours ago) and read 5375 times:

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


regds
MEL



Think of the brighter side!
User currently offlineStarlionblue From Greenland, joined Feb 2004, 17114 posts, RR: 66
Reply 19, posted (9 years 1 week 2 days 15 hours ago) and read 5312 times:

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."
User currently offlineBoeing Nut From , joined Dec 1969, posts, RR:
Reply 20, posted (9 years 1 week 2 days 12 hours ago) and read 5261 times:

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!!!!


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Geeze people, wake up!!!

 rotfl 


User currently offlineLightsaber From United States of America, joined Jan 2005, 13437 posts, RR: 100
Reply 21, posted (9 years 1 week 2 days 11 hours ago) and read 5239 times:
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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



Societies that achieve a critical mass of ideas achieve self sustaining growth; others stagnate.
User currently offline2H4 From United States of America, joined Oct 2004, 8956 posts, RR: 60
Reply 22, posted (9 years 1 week 2 days 11 hours ago) and read 5229 times:
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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 currently offlineStarlionblue From Greenland, joined Feb 2004, 17114 posts, RR: 66
Reply 23, posted (9 years 1 week 2 days 7 hours ago) and read 5175 times:

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."
User currently offlineLightsaber From United States of America, joined Jan 2005, 13437 posts, RR: 100
Reply 24, posted (9 years 1 week 2 days 6 hours ago) and read 5163 times:
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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



Societies that achieve a critical mass of ideas achieve self sustaining growth; others stagnate.
25 Prebennorholm : 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
26 Post contains images Starlionblue : Or you could just bring back good old RATO
27 Post contains images Lightsaber : 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 180
28 Post contains images FTOHIST : Not when you're one of the people who work on that airplane!!!!!!
29 Post contains images Starlionblue : I'm not surprised, but I'm still laughing
30 Dw747400 : 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 addition
31 Starlionblue : 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) wil
32 Prebennorholm : 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
33 Stitch : An all-composite, all-electrical, bleedless twin VLA would be something to see...
34 Starlionblue : 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
35 Zvezda : That's why I wrote "... a twin the size of the B747," and not "a twin B747." I'm confident that Y3 will be a twin. The launch of the B747-8 means tha
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