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Twin Engined 747...is It Possible?  
User currently offlineJcchristie From United States of America, joined Nov 2006, 39 posts, RR: 0
Posted (6 years 2 weeks 6 days ago) and read 14823 times:

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?

27 replies: All unread, showing first 25:
 
User currently offlineN104UA From United States of America, joined Dec 2007, 906 posts, RR: 0
Reply 1, posted (6 years 2 weeks 6 days ago) and read 14833 times:

Well I know that in an emergency they could fly with 2 engines


"Learn the rules, so you know how to break them properly." -H.H. The Dalai Lama
User currently offlineADent From United States of America, joined Dec 2006, 1370 posts, RR: 2
Reply 2, posted (6 years 2 weeks 5 days 23 hours ago) and read 14782 times:

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.


User currently offlineDL767captain From United States of America, joined Mar 2007, 2539 posts, RR: 0
Reply 3, posted (6 years 2 weeks 5 days 22 hours ago) and read 14631 times:

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

User currently offlineUnited Airline From Hong Kong, joined Jan 2001, 9168 posts, RR: 15
Reply 4, posted (6 years 2 weeks 5 days 22 hours ago) and read 14550 times:

Maybe they can make stronger engines for it?

User currently offlineLuv2cattlecall From United States of America, joined Sep 2007, 1650 posts, RR: 2
Reply 5, posted (6 years 2 weeks 5 days 22 hours ago) and read 14542 times:
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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?



When you have to breaststroke to your connecting flight...it's a crash!
User currently offlineCloudyapple From Hong Kong, joined Jul 2005, 2454 posts, RR: 10
Reply 6, posted (6 years 2 weeks 5 days 21 hours ago) and read 14510 times:



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.



A310/A319/20/21/A332/3/A343/6/A388/B732/5/7/8/B742/S/4/B752/B763/B772/3/W/E145/J41/MD11/83/90
User currently offlineAlessandro From , joined Dec 1969, posts, RR:
Reply 7, posted (6 years 2 weeks 5 days 21 hours ago) and read 14498 times:

Of course they could fly a -SP series on two GE90-115, but no economical point of certify one.

User currently offlineBA777ER236 From United Kingdom, joined Sep 2006, 278 posts, RR: 8
Reply 8, posted (6 years 2 weeks 5 days 20 hours ago) and read 14334 times:

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
 Smile



Flying would be easy if it wasn't for the ground
User currently offlineVincewy From Taiwan, joined Oct 2005, 767 posts, RR: 1
Reply 9, posted (6 years 2 weeks 5 days 20 hours ago) and read 14311 times:

Wasn't there a thread about econoliner (twin engine, double decker) earlier? Just a smaller version of A380 in 400 seat category.

User currently offlineUnited Airline From Hong Kong, joined Jan 2001, 9168 posts, RR: 15
Reply 10, posted (6 years 2 weeks 5 days 16 hours ago) and read 13952 times:

A twin engined B 747 makes sense. It's bigger than the B 777-300ER and it saves fuel

User currently offlineKeesje From , joined Dec 1969, posts, RR:
Reply 11, posted (6 years 2 weeks 5 days 16 hours ago) and read 13884 times:

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

http://www.cardatabase.net/modifiedairlinerphotos/photos/big/00005184.jpg
Robert Fall, http://www.cardatabase.net/modifieda...earch/photo_search.php?id=00005184


User currently offlineDtwclipper From , joined Dec 1969, posts, RR:
Reply 12, posted (6 years 2 weeks 5 days 15 hours ago) and read 13785 times:

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

http://i46.photobucket.com/albums/f127/dtwclipper/tri_747.jpg


User currently offlineAcNDTTech From United States of America, joined Jul 2008, 338 posts, RR: 0
Reply 13, posted (6 years 2 weeks 5 days 11 hours ago) and read 13056 times:

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.

User currently offlineEA772LR From United States of America, joined Mar 2007, 2836 posts, RR: 10
Reply 14, posted (6 years 2 weeks 5 days 10 hours ago) and read 12662 times:



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.
User currently offlineRbgso From United States of America, joined Jun 2006, 588 posts, RR: 0
Reply 15, posted (6 years 2 weeks 5 days 10 hours ago) and read 12320 times:



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......


User currently offlineVictrola From United States of America, joined Apr 2008, 506 posts, RR: 1
Reply 16, posted (6 years 2 weeks 5 days 10 hours ago) and read 12206 times:



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?


User currently offlineTugger From United States of America, joined Apr 2006, 5503 posts, RR: 8
Reply 17, posted (6 years 2 weeks 5 days 10 hours ago) and read 12175 times:



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



I don’t know that I am unafraid to be myself, but it is hard to be somebody else. -W. Shatner
User currently offlineBrettFromCLT From United States of America, joined Nov 2006, 136 posts, RR: 0
Reply 18, posted (6 years 2 weeks 5 days 9 hours ago) and read 11129 times:



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


User currently offlineWarren747sp From United States of America, joined Feb 2004, 1158 posts, RR: 0
Reply 19, posted (6 years 2 weeks 5 days 3 hours ago) and read 7427 times:

Definitely work on the SP so bring it on!


747SP
User currently offlineSuperfly From Thailand, joined May 2000, 39834 posts, RR: 74
Reply 20, posted (6 years 2 weeks 5 days 3 hours ago) and read 7307 times:



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
User currently offlineLowrider From United States of America, joined Jun 2004, 3220 posts, RR: 10
Reply 21, posted (6 years 2 weeks 4 days 23 hours ago) and read 7128 times:



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

I wouldn't worry until you see talks of ETOPS 420.



Proud OOTSK member
User currently offlineStarlionblue From Greenland, joined Feb 2004, 17017 posts, RR: 67
Reply 22, posted (6 years 2 weeks 4 days 23 hours ago) and read 7128 times:



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.



"There are no stupid questions, but there are a lot of inquisitive idiots."
User currently offlineSEPilot From United States of America, joined Dec 2006, 6878 posts, RR: 46
Reply 23, posted (6 years 2 weeks 3 days 6 hours ago) and read 6871 times:

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
User currently offlineAcNDTTech From United States of America, joined Jul 2008, 338 posts, RR: 0
Reply 24, posted (6 years 2 weeks 3 days 1 hour ago) and read 6817 times:



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).


25 Post contains images AAH732UAL : 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]
26 SEPilot : 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
27 AcNDTTech : 200k......not a doubt in my mind.
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