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Twin 747 Possible?  
User currently offlineTimboflier215 From United Kingdom, joined May 2005, 1323 posts, RR: 1
Posted (8 years 6 months 2 weeks 5 days 10 hours ago) and read 7034 times:

hey all!

i was watching a discovery programme the other day about the new GE engines. GE had its own 747 to test out the engines, and put one of them on in place of engine no 3. it looked HUGE compared to the other engines! they said that in flight, they were able to power down the other 3 engines and fly just using the GE. so my question is, with advances in engine technology, would it be possible to fly a 747-sized aircraft using just 2 engines? i know that take-off etc requires a whole lot more power than simply cruising, but does anyone think it could be possible in the future, as 2 engines would be cheaper to maintain than 4??

cheers!

38 replies: All unread, showing first 25:
 
User currently offlineKaitak744 From United States of America, joined Jul 2005, 2364 posts, RR: 3
Reply 1, posted (8 years 6 months 2 weeks 5 days 10 hours ago) and read 7002 times:

Of coarse it would be possible. But on the 747 I doubt. There is not enough wing clearance to safely have 2 GE90s on the in-board pylons. Having them on the outboard positions would cause weight issues. So, yes it's possible but not on the 747.

User currently offlineDw747400 From United States of America, joined Aug 2001, 1257 posts, RR: 1
Reply 2, posted (8 years 6 months 2 weeks 5 days 10 hours ago) and read 6933 times:

It is certainly possible--and in some ways, it has already happened. The Maximum takeoff weight of a 777-300ER is greater than that of the earliest 747 variants. Of course, the -300ER represents close to, if not the, limit in growth for the 777 series, while the 747-100 was the starting point of a series of aircraft that have gotten substantially heavier. Still, it is a twin that is heavier than some of the 747s out there.


CFI--Certfied Freakin Idiot
User currently offlineTifoso From United States of America, joined Jan 2006, 440 posts, RR: 0
Reply 3, posted (8 years 6 months 2 weeks 5 days 9 hours ago) and read 6899 times:

I have wondered about the same question.

Is it possible that Y3 is a twin 747?


User currently offlineTimboflier215 From United Kingdom, joined May 2005, 1323 posts, RR: 1
Reply 4, posted (8 years 6 months 2 weeks 5 days 9 hours ago) and read 6867 times:

thanks for the replies! i hadnt thought of the probs with putting the engines on the in-board pylons. im just surprised that boeing arent modifying the 747-8 wing so it could fit 2 engines.

User currently offlineEHHO From Bulgaria, joined Dec 2005, 815 posts, RR: 7
Reply 5, posted (8 years 6 months 2 weeks 5 days 9 hours ago) and read 6838 times:

Hey guys.. It has been done already!!


Modified Airliner Photos:
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Design © Robert Fall
Template © Daniel & Robert Fall



Just joking of course, but the idea is still cool to think about.



"Get your facts first. Then you may distort them as much as you please" -- Mark Twain
User currently offlineWhiteHatter From , joined Dec 1969, posts, RR:
Reply 6, posted (8 years 6 months 2 weeks 5 days 9 hours ago) and read 6821 times:

There are calculations which show how much thrust would be needed for a twin of the 747's size, and they come out as requiring a lot more thrust than a Ge90 or Trent 8104 currently provides.

It's in relation to engine failure on takeoff. A twin needs sufficient power to continue its climb should an engine fail. With a quad the calculations are done for a single engine losing power and the other three being available.

I think it comes out as needing an engine in the 150,000lbs thrust region to effectively turn a 744 into a twin. And that creates a whole new set of engineering problems with the wing and pylons too.


User currently offlineTerryb99 From United States of America, joined Sep 2004, 291 posts, RR: 0
Reply 7, posted (8 years 6 months 2 weeks 5 days 9 hours ago) and read 6814 times:

Sounds like the 747 we had flying around Seattle years ago during the 777 engine testing. They installed one 777 engine in place of the standard 747 engine. It dwarfed the engine next to it. Was a strange site to see.

User currently offlineTimboflier215 From United Kingdom, joined May 2005, 1323 posts, RR: 1
Reply 8, posted (8 years 6 months 2 weeks 5 days 9 hours ago) and read 6693 times:

Quoting Terryb99 (Reply 7):
It dwarfed the engine next to it. Was a strange site to see.

hehe, yeah! the aircraft looked tres bizarre! youd imagine a 747 engine to be big, but they were nothing compared to the GE!


User currently offlineZvezda From Lithuania, joined Aug 2004, 10511 posts, RR: 64
Reply 9, posted (8 years 6 months 2 weeks 5 days 8 hours ago) and read 6627 times:

Quoting Tifoso (Reply 3):

Is it possible that Y3 is a twin 747?

Y3 will almost certainly be a twin about the size of the B747, but it will definitely not be a B747.

Quoting Timboflier215 (Reply 4):
im just surprised that boeing arent modifying the 747-8 wing so it could fit 2 engines.

That would have been far too expensive to develop relative to the advantage. Four GEnx engines are perfect for the B747-8.


User currently offlineGatorman96 From United States of America, joined Dec 2005, 870 posts, RR: 0
Reply 10, posted (8 years 6 months 2 weeks 5 days 8 hours ago) and read 6612 times:






It would be cool, but I can't imagine the 747 with anything less than 4 engines!



Cha brro
User currently offlineNYC777 From United States of America, joined Jun 2004, 5732 posts, RR: 48
Reply 11, posted (8 years 6 months 2 weeks 4 days 14 hours ago) and read 5921 times:

Not only would you need as usbtanitally strengthened wing box but you have to have higher and stronger landing gear if you're going to hang two 150k lb of thrust engines on a plane the size of a 747. That said can you imagine the economics of such a plane...bye bye to 4 engines 4 long haul!!!!


That which does not kill me makes me stronger.
User currently offlineOzarkD9S From United States of America, joined Oct 2001, 5008 posts, RR: 21
Reply 12, posted (8 years 6 months 2 weeks 4 days 14 hours ago) and read 5765 times:

Didn't Boeing do a tri-jet 747 study when they were designing the SP version? I seem to recall seeing a pic years and years ago. It looked like a cross between a 747 and an L-1011.


Next Up: STL-LGA-RIC-ATL-STL
User currently offlineAri From UK - England, joined May 2005, 131 posts, RR: 0
Reply 13, posted (8 years 6 months 2 weeks 4 days 14 hours ago) and read 5237 times:

would it not be possible to have 4 engines,2 more powerful than the other 2,and only use the two more powerful engines during flight?

aRi


User currently offlineNYC777 From United States of America, joined Jun 2004, 5732 posts, RR: 48
Reply 14, posted (8 years 6 months 2 weeks 4 days 13 hours ago) and read 5069 times:

Quoting Ari (Reply 13):
would it not be possible to have 4 engines,2 more powerful than the other 2,and only use the two more powerful engines during flight?

then you're dragging around the weight of two engines that are not doing anything. I think that would be highly inefficient.



That which does not kill me makes me stronger.
User currently offlineGeo772 From United Kingdom, joined Jul 2004, 519 posts, RR: 0
Reply 15, posted (8 years 6 months 2 weeks 4 days 13 hours ago) and read 5008 times:

The 747's wing would have to be completely redesigned were it to only have 2 engines.

The weight of the outboard engines reduces stress on the wing during flight, were the outboard engines not there then the wing would float up by an enormous amount, far more than it already does.

The 777-300ER already has a max takeoff weight greater than the 747-100, 351 tonnes as opposed to 340 tonnes.

There should be no reason why in twenty years time to see 450 tonne aircraft flying with only 2 engines, just not right now.



Flown on A300B4/600,A319/20/21,A332/3,A343,B727,B732/3/4/5/6/7/8,B741/2/4,B752/3,B762/3,B772/3,DC10,L1011-200,VC10,MD80,
User currently offlineIkramerica From United States of America, joined May 2005, 21474 posts, RR: 60
Reply 16, posted (8 years 6 months 2 weeks 4 days 13 hours ago) and read 4913 times:

Quoting Ari (Reply 13):
would it not be possible to have 4 engines,2 more powerful than the other 2,and only use the two more powerful engines during flight?

The new 748I will have 65k engines, roughly. 3 on takeoff is 195k, not 150k. So, using a 115k GE90, that leaves 80k, so the other two engines must be 40k each, which is probably less efficient weight wise than just have four 65k engines. Also, the plane would be overpowered.

2x115+2x40=310k
4x65=260k

That ability to make 50k more is a huge weight and efficiency penalty.

But as stated, the original 747-100 could fly with 2 GE90-115k engines, but engine out would pose a bit of a problem...



Of all the things to worry about... the Wookie has no pants.
User currently offlineTockeyhockey From United States of America, joined Feb 2005, 950 posts, RR: 0
Reply 17, posted (8 years 6 months 2 weeks 4 days 11 hours ago) and read 3641 times:

if the 747x lost as much weight proportionally as the 767 in comparison to the 787, you could probably get the thrust figures to work out with a fully maxed out GE-90. however, there would be substantial redesign issues in the avionics, wing, cockpit, electrical systems, etc.

i wonder if boeing even looked at this as an option when it was dreaming up the 748.


User currently offlineTimboflier215 From United Kingdom, joined May 2005, 1323 posts, RR: 1
Reply 18, posted (8 years 6 months 2 weeks 4 days 11 hours ago) and read 3579 times:

thanks for the replies guys. i was just an interesting thought, but obv the economics of redesign etc are greater than any efficiency savings, or boeing would have gone with it no doubt. i cant imagine they dismissed it out hand; they would have looked at all possibilities, inc a twin im sure.

User currently offlineZvezda From Lithuania, joined Aug 2004, 10511 posts, RR: 64
Reply 19, posted (8 years 6 months 2 weeks 3 days 19 hours ago) and read 2700 times:

Quoting Tockeyhockey (Reply 17):

i wonder if boeing even looked at this as an option when it was dreaming up the 748.

Definitely not. Boeing considered three possible derivates from minimal to extensive. The B747-8 is a compromise between the minimal and medium original proposals. A twin would have been much more radical even than the most extensive proposal considered.


User currently offlinePanHAM From Germany, joined May 2005, 9164 posts, RR: 29
Reply 20, posted (8 years 6 months 2 weeks 3 days 19 hours ago) and read 2681 times:

Quoting EHHO (Reply 5):
Hey guys.. It has been done already!!



Quoting EHHO (Reply 5):
Modified Airliner Photos:

Design © Robert Fall
Template © Daniel & Robert Fall

Typically Dutch, always on the cheap side.......
 Wink



E's passed on! That parrot is no more! He has ceased to be! E's expired and gone to meet 'is maker!
User currently offlineBmacleod From Canada, joined Aug 2001, 2243 posts, RR: 0
Reply 21, posted (8 years 6 months 2 weeks 3 days 16 hours ago) and read 2515 times:

Hmmm. Maybe twinning the A380 is possible too?  rotfl   rotfl 

The sheer size and structure of the 747 is just to big for a twin-engine design. Even thinking of a twin-engine 747 is beyond logic.....



The engine is the heart of an airplane, but the pilot is its soul.
User currently offlineTifoso From United States of America, joined Jan 2006, 440 posts, RR: 0
Reply 22, posted (8 years 6 months 2 weeks 3 days 16 hours ago) and read 2504 times:

Quoting Zvezda (Reply 9):
Y3 will almost certainly be a twin about the size of the B747, but it will definitely not be a B747.

Thanks Zvezda. Any reasoning behind this?


User currently offlineMolykote From United States of America, joined Aug 2005, 1340 posts, RR: 29
Reply 23, posted (8 years 6 months 2 weeks 3 days 16 hours ago) and read 2468 times:

Got to love the GE flying testbed with Pratts  Smile


Speedtape - The asprin of aviation!
User currently offlineRichardPrice From , joined Dec 1969, posts, RR:
Reply 24, posted (8 years 6 months 2 weeks 3 days 16 hours ago) and read 2443 times:

Quoting Bmacleod (Reply 21):
Hmmm. Maybe twinning the A380 is possible too?

I have absolutely no links or proof for this, so dont even consider this gospel or anything, but I recall a TV interview in 2005 after the A380 first flew where an Airbus spokesman mentioned in an almost throwaway line that the A380 had been designed with only fitting two engines for a super capacity shorthaul shuttle aircraft in mind. This hasnt been mentioned anywhere else as far as I can see, but it was definately on a UK BBC news interview, I think it was either during a feature on the Broughton wing plant or a research centre in the southwest.

Now that would be cool.


25 Zvezda : If the design were started now, the WhaleJet would almost certainly be a twin. That reminds me of the 1955 IBM research paper which proved that the m
26 Post contains images Ikramerica : Just shows GE engines are too valuable in the marketplace to "waste" on a testbed... Bill Gates said the same thing about 640kB in the early 80s, and
27 RichardPrice : He never said anything of the sort, its a common urban myth thats constantly reiterated.
28 Gigneil : Cost less to operate, sure. Generate more revenue? N
29 Zvezda : Neither Airbus nor Boeing have ever exhibited Bill Gates' fondness for persisting with ancient technology. Airbus and Boeing innovate -- something Mi
30 WAH64D : Aren't they just. Think how many toasters and lightbulbs GE could make out of one GE90.
31 Post contains images EHHO : Oh yeah? We'll see at the Weltmannschaft!! I'll let you know when my compatriates will be singing "Schade Deutschland, alles ist vorbei.." Just jokin
32 Tifoso : I did not mean why it would be a twin, but would it not be a twin 747. Here's what you said: That is the biggest piece of mis-information that has fl
33 Zvezda : To make a twin B747 would require a completely new wing. When Boeing go to the expense of a completely new wing for a B747-size aircraft, they will s
34 Rampart : So you are saying the pic in reply 10 is nothing but a photo retouch? -Rampart
35 Tifoso : The addition of features like the partial FBW, bleed 787 engines makes me think that 748 maybe a stepping stone to an all composite, twin engined 747
36 Dw747400 : It is a real photo. Zvezda may be discussing clearence needs for an operational aircraft, which could differ from an experimental aircraft. I'd ventu
37 Rampart : I was actually quoting Kaitak744, who wasn't clear about differentiating an experimental aircraft from an operational one, only that "there wasn't en
38 Dw747400 : Your right... sorry about that. Must have been looking at the quotes in Reply 34 and 35 at the same time. In terms of wing strength, the long term ef
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