jcchristie
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Twin Engined 747...is It Possible?

Mon Aug 04, 2008 4:54 am

It is no lie that the 777-300 is a HUGE twin jet and almost the size of the 747. So could 2 777 engines power a 747 and be certified for ETOPS?
 
N104UA
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RE: Twin Engined 747...is It Possible?

Mon Aug 04, 2008 4:55 am

Well I know that in an emergency they could fly with 2 engines
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ADent
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RE: Twin Engined 747...is It Possible?

Mon Aug 04, 2008 5:13 am

No. Not enough thrust to take on (from decision speed) just one 777 engine. It could fly, but it could not be certified.

Assuming the 747 is designed for one engine out operation, a 747-100 could be had with 46,500 lb thrust engines. That implies you need 139,500 lb thrust to operate safely.

Obviously there are more concerns, but this should be in the ballpark.

BTW the 747-400 comes with 59,500 lb engines, so with one engine out it gets 178,500 lb thrust.
 
dl767captain
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RE: Twin Engined 747...is It Possible?

Mon Aug 04, 2008 6:30 am

I don't think the current 777 engines are enough to power a 747 sized jet on two engines. Maybe something like the engines going on the A350 could work... or maybe the A380... but if they could get enough thrust out of one engine to allow it to be ETOPS certified much like the 777 then it could happen. But they would need to redesign the 747 before this could happen
 
United Airline
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RE: Twin Engined 747...is It Possible?

Mon Aug 04, 2008 7:01 am

Maybe they can make stronger engines for it?
 
luv2cattlecall
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RE: Twin Engined 747...is It Possible?

Mon Aug 04, 2008 7:05 am



Quoting DL767captain (Reply 3):
Maybe something like the engines going on the A350 could work... or maybe the A380...

Aren't the T7's engines bigger than the A350 and the A380's though?
.
 
cloudyapple
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RE: Twin Engined 747...is It Possible?

Mon Aug 04, 2008 7:13 am



Quoting DL767captain (Reply 3):
Maybe something like the engines going on the A350 could work...

Definitely - any engine will work with enough of them on an aeroplane.

The GEnx are 66500lbf each x 4, the TXWB are 74000lbf to 92000lbf.

So you need at least 3 (at max rating) or 4 (at nominal rating). Makes a nice new trijet.
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Alessandro
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RE: Twin Engined 747...is It Possible?

Mon Aug 04, 2008 7:14 am

Of course they could fly a -SP series on two GE90-115, but no economical point of certify one.
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BA777ER236
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RE: Twin Engined 747...is It Possible?

Mon Aug 04, 2008 8:37 am

It would be feasible to produce an engine to power a twin of this size, but the fan diameter would preclude putting it under the wing of a 747. It has been done on tests but the ground clearance was very small and not practical for 'normal' operations.

Futhermore, the wing structure would have to be substantially modified as the current wing relies upon the thrust load and bending relief from the engines where they are currently placed.

Additionally, the current hydraulic, electric and air systems would have to undergo considerable modification to suit a twin configuration.

All of this adds up to considerable cost. If Boeing thought it would be worthwhile then they would have done it already!

Tell you what, why not just buy a 777-300ER instead?!  Big grin

Cheers
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vincewy
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RE: Twin Engined 747...is It Possible?

Mon Aug 04, 2008 8:45 am

Wasn't there a thread about econoliner (twin engine, double decker) earlier? Just a smaller version of A380 in 400 seat category.
 
United Airline
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RE: Twin Engined 747...is It Possible?

Mon Aug 04, 2008 12:23 pm

A twin engined B 747 makes sense. It's bigger than the B 777-300ER and it saves fuel
 
keesje
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RE: Twin Engined 747...is It Possible?

Mon Aug 04, 2008 12:43 pm

Yes KLM tried it last winter but returned to squads because of ground clearance concerns.

http://www.cardatabase.net/modifiedairlinerphotos/photos/big/00005184.jpg
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dtwclipper
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RE: Twin Engined 747...is It Possible?

Mon Aug 04, 2008 1:15 pm

There was an earlier study of a 747 tri-jet.

http://i46.photobucket.com/albums/f127/dtwclipper/tri_747.jpg
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acNDTTech
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RE: Twin Engined 747...is It Possible?

Mon Aug 04, 2008 5:55 pm

In time it will happen.....no doubt. Engine technology is growing at a phenomenal rate. I can't wait to see what the next 10-15 years brings. I also think there will be another supersonic passenger aircraft in that time frame. Aviation Week & Space Technology has some pretty good info. about the giant leaps that have/are being made pertaining to SST technology.
 
EA772LR
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RE: Twin Engined 747...is It Possible?

Mon Aug 04, 2008 6:20 pm



Quoting DL767captain (Reply 3):
I don't think the current 777 engines are enough to power a 747 sized jet on two engines. Maybe something like the engines going on the A350 could work... or maybe the A380... but if they could get enough thrust out of one engine to allow it to be ETOPS certified much like the 777 then it could happen.

The 777-300ER's GE90-115B has 115,300lbs of thrust and demonstrated127,900lbs of thrust...much much more than the TrentXWB will produce and even more than the Trent900/GP7200 can produce. So if there was any engine able to power a 747 as a tin, it would be a derivative of the GE90-115B

Quoting Keesje (Reply 11):
Yes KLM tried it last winter but returned to squads because of ground clearance concerns.

 rotfl  That is really awkward seeing a 747 with 2 engines...
We often judge others by their actions, but ourselves by our intentions.
 
Rbgso
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RE: Twin Engined 747...is It Possible?

Mon Aug 04, 2008 6:39 pm



Quoting EA772LR (Reply 14):
That is really awkward seeing a 747 with 2 engines...

Actually, I thought it looked rather striking. I could live with that design......
 
victrola
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RE: Twin Engined 747...is It Possible?

Mon Aug 04, 2008 6:46 pm



Quoting Keesje (Reply 11):
Yes KLM tried it last winter but returned to squads because of ground clearance concerns

What's the story behind this picture? Was this just some clever photoshop?
 
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Tugger
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RE: Twin Engined 747...is It Possible?

Mon Aug 04, 2008 6:47 pm



Quoting Keesje (Reply 11):
but returned to squads because of ground clearance concerns.

Guess you could have giant versions of the 737NG's CFM56-3 series housing......

Tugg
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BrettFromCLT
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RE: Twin Engined 747...is It Possible?

Mon Aug 04, 2008 7:51 pm



Quoting Victrola (Reply 16):
What's the story behind this picture? Was this just some clever photoshop?

That's from Modified Airliner Photos - yes, it's photoshopped.

Brett  Smile
 
warren747sp
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RE: Twin Engined 747...is It Possible?

Tue Aug 05, 2008 1:47 am

Definitely work on the SP so bring it on!
747SP
 
Superfly
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RE: Twin Engined 747...is It Possible?

Tue Aug 05, 2008 1:58 am



Quoting Jcchristie (Thread starter):
could 2 777 engines power a 747 and be certified for ETOPS?

I hope not!
4 engines forever!
Bring back the Concorde
 
lowrider
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RE: Twin Engined 747...is It Possible?

Tue Aug 05, 2008 5:55 am



Quoting Superfly (Reply 20):
I hope not!
4 engines forever!

I wouldn't worry until you see talks of ETOPS 420.
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Starlionblue
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RE: Twin Engined 747...is It Possible?

Tue Aug 05, 2008 5:58 am



Quoting DL767captain (Reply 3):
I don't think the current 777 engines are enough to power a 747 sized jet on two engines. Maybe something like the engines going on the A350 could work... or maybe the A380

The 380 engines are smaller than the 777 engines.

Quoting United Airline (Reply 4):
Maybe they can make stronger engines for it?

Well yes. That would be the idea. However you would be developing the most expensive engines ever for a rather small market (at least to start with). Not saying it won't happen, just that there are a few economic hurdles.

Quoting United Airline (Reply 10):
A twin engined B 747 makes sense. It's bigger than the B 777-300ER and it saves fuel

Just because it has two engines doesn't necessarily mean it saves fuel.
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RE: Twin Engined 747...is It Possible?

Wed Aug 06, 2008 10:15 pm

This is never going to happen. The market for VLA's is not big enough to justify it, and the cost of developing the engine would be prohibitive. Eventually an engine big enough for the job will be developed, but it will go on Y3 or its successor. The 747 would require too much redesign to accommodate engines that large.
The problem with making things foolproof is that fools are so doggone ingenious...Dan Keebler
 
acNDTTech
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RE: Twin Engined 747...is It Possible?

Thu Aug 07, 2008 4:05 am



Quoting AcNDTTech (Reply 13):
In time it will happen.....no doubt.

I have to quote myself on this one. I didn't mean that we will see a twin engine 747. What I meant to say was that I believe that we will see a twin engine plane with the equivalent cargo and/or pax capacity as the current 747(400).
 
AAH732UAL
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RE: Twin Engined 747...is It Possible?

Thu Aug 07, 2008 5:51 am

IIRC the 747-400(ferry weight) can fly on 2 engines thought out the entire flight regime. So yeah its possible maybe  

[Edited 2008-08-06 22:54:55]
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RE: Twin Engined 747...is It Possible?

Thu Aug 07, 2008 2:48 pm



Quoting AcNDTTech (Reply 24):
I have to quote myself on this one. I didn't mean that we will see a twin engine 747. What I meant to say was that I believe that we will see a twin engine plane with the equivalent cargo and/or pax capacity as the current 747(400).

This I totally agree with. I have no doubt that eventually we'll see twins even bigger than the A380. They may be BWB's, but they will come. I do not believe that there is any absolute limit on engine size; right now the practical limit seems to be about 150k, but when the 777 was in development they were pushing the practical limits then to get 90K. Once 150K engines appear the "practical limit" will get pushed again, probably to 200k.
The problem with making things foolproof is that fools are so doggone ingenious...Dan Keebler
 
acNDTTech
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RE: Twin Engined 747...is It Possible?

Thu Aug 07, 2008 5:18 pm

200k......not a doubt in my mind.

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