United Airline From Hong Kong, joined Jan 2001, 8803 posts, RR: 17 Posted (7 years 7 months 5 days 6 hours ago) and read 5053 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.
Kiwiandrew From New Zealand, joined Jun 2005, 8435 posts, RR: 14 Reply 1, posted (7 years 7 months 5 days 6 hours ago) and read 5041 times:
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 ;-)
Zippyjet From United States of America, joined Sep 2001, 4740 posts, RR: 13 Reply 6, posted (7 years 7 months 5 days 5 hours ago) and read 4839 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.
Stitch From United States of America, joined Jul 2005, 26944 posts, RR: 83 Reply 7, posted (7 years 7 months 5 days 5 hours ago) and read 4744 times:
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.
AKelley728 From United States of America, joined Dec 1999, 2105 posts, RR: 6 Reply 9, posted (7 years 7 months 5 days 5 hours ago) and read 4686 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.
Sllevin From United States of America, joined Jan 2002, 3376 posts, RR: 6 Reply 11, posted (7 years 7 months 4 days 21 hours ago) and read 4404 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!
Zeke From Hong Kong, joined Dec 2006, 7767 posts, RR: 73 Reply 12, posted (7 years 7 months 4 days 20 hours ago) and read 4331 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
Ikramerica From United States of America, joined May 2005, 21041 posts, RR: 60 Reply 13, posted (7 years 7 months 4 days 19 hours ago) and read 4300 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.
QFA380 From Australia, joined Jul 2005, 2042 posts, RR: 1 Reply 16, posted (7 years 7 months 4 days 18 hours ago) and read 4206 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.
Zvezda From Lithuania, joined Aug 2004, 10511 posts, RR: 65 Reply 17, posted (7 years 7 months 4 days 17 hours ago) and read 4161 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).
Starlionblue From Hong Kong, joined Feb 2004, 15904 posts, RR: 66 Reply 19, posted (7 years 7 months 4 days 12 hours ago) and read 4022 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:
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." - from Citadel by John Ringo
Lightsaber From United States of America, joined Jan 2005, 10879 posts, RR: 100 Reply 21, posted (7 years 7 months 4 days 8 hours ago) and read 3949 times:
Quoting Ikramerica (Reply 13): Alternatively, you'd need a lighter frame and/or an engine capable of at least 180,000 lbs.
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... But this wouldn't be a 747, it would be a 787-12.
Quoting Kiwiandrew (Reply 1):
.... but doesn't BA run 3-engined 744's ?
Poor BA... its going to be like B6 and nose gear, famous for that "oops" for a bit.
2H4 From United States of America, joined Oct 2004, 8950 posts, RR: 62 Reply 22, posted (7 years 7 months 4 days 7 hours ago) and read 3939 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.
Starlionblue From Hong Kong, joined Feb 2004, 15904 posts, RR: 66 Reply 23, posted (7 years 7 months 4 days 4 hours ago) and read 3885 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 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." - from Citadel by John Ringo
Lightsaber From United States of America, joined Jan 2005, 10879 posts, RR: 100 Reply 24, posted (7 years 7 months 4 days 3 hours ago) and read 3873 times:
Hey, as long as my engine works! Structures isn't my job.
Lightsaber
Life is short, Live it!
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 Starlionblue: Or you could just bring back good old RATO
27 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 FTOHIST: Not when you're one of the people who work on that airplane!!!!!!
29 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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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. 
But this wouldn't be a 747, it would be a 787-12. 
As 2H4 points out, it's not only the wing but "all that other stuff".
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