Fly2HMO
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Would A 747 Be Better With 2 GE-90s?

Tue Mar 09, 2004 4:57 am

I was wonderin', it would be cheaper, less maintenance, safer, etc...

I know this will never happen, but do you think it would be feasible instead of the normal 4 engines? Just curious...

cheers  Smile
 
DeltaGuy
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RE: Would A 747 Be Better With 2 GE-90s?

Tue Mar 09, 2004 6:04 am

I can't imagine two, but four GE90's would be just splendid...abiet, waaay overpowered. Never hurts to dream though  Big thumbs up

DeltaGuy
"The cockpit, what is it?" "It's the little room in the front of the plane where the pilot sits, but that's not importan
 
sean1234
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RE: Would A 747 Be Better With 2 GE-90s?

Tue Mar 09, 2004 7:14 am

You would also have less drag by having two engine nacelles instead of four.
 
david b.
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RE: Would A 747 Be Better With 2 GE-90s?

Tue Mar 09, 2004 7:28 am

But the GE90s are bigger. Won't that cause more drag? Not to mention the whole wing has to be redesign and possibly the landing gears as well.
Teenage-know-it-alls should be shot on sight
 
QantasA332
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RE: Would A 747 Be Better With 2 GE-90s?

Tue Mar 09, 2004 7:28 am

Two GE90 115B's would certainly provide enough thrust, and drag would of course be reduced by there being fewer nacelles. However, four engines for a 747-like aircraft is usually preferable for a few reasons. One major advantage is that having four spaced-out engines on the wing helps counteract the huge wing-bending that is quite large on 747s. Also, having four engines doesn't require lengthy and pricey ETOPS requirements, and many airlines prefer four engines for general safety.

Cheers,
QantasA332

[Edited 2004-03-08 23:30:17]
 
Fly2HMO
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RE: Would A 747 Be Better With 2 GE-90s?

Tue Mar 09, 2004 10:05 am

I'm not talking back to anybody, but everything I've read and heard (not only in the forums) is that today's engines are so reliable, that the less you have, the safer it is. Back in the early days of flight and until the advent of ETOPS it was the opposite, the more engines you had, the safer it was.

Now that I think of it, the 747 would look really ugly with 2 engines.  Laugh out loud
 
MITaero
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RE: Would A 747 Be Better With 2 GE-90s?

Tue Mar 09, 2004 11:11 am

An aircraft is a system, it's hard to change one part of it without ruining some type of optimization that was done.

I think we are moving towards the time when engine reliability makes 2 engines prefereable.
 
SEAPete
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RE: Would A 747 Be Better With 2 GE-90s?

Tue Mar 09, 2004 7:34 pm

Ironically two modern GE-90's with 115,000 lbs of thrust can equal or exceed the total thrust of a 744. With two instead of four holes there is an inherent cost savaings with less maintnance and less drag, etc. However, I agree with DeltaGuy a 744 with 4 GE-90's.. All I can say is WOW. Imagin the TO/climb performance!

Cheers!

Pete
SEA No other place like it
 
727200er
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RE: Would A 747 Be Better With 2 GE-90s?

Tue Mar 09, 2004 10:10 pm

I'm not sure about it being better per se , But It would look interesting.

Four of them would be incredible Imagine the A380 killer you could build with four of them.
"they who dream by day are cognizant of many things which escape those who dream only at night" - Edgar Allen Poe
 
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mighluss
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RE: Would A 747 Be Better With 2 GE-90s?

Tue Mar 09, 2004 10:53 pm

Well, if you have an empty 744 (400.000lbs) and you put 60.000lbs of fuel, then you install 4 GE90's @ 115.000lbs each (460.000lbs) you have a 744 that can climb vertically (I am wrong?)... dream is free! Big grin

anyway, I don't think that those 60.000lbs of fuel would last for a very long time...
Miquel.
 
fritzi
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RE: Would A 747 Be Better With 2 GE-90s?

Tue Mar 09, 2004 11:51 pm

Well, if you have an empty 744 (400.000lbs) and you put 60.000lbs of fuel, then you install 4 GE90's @ 115.000lbs each (460.000lbs) you have a 744 that can climb vertically (I am wrong?)...

If it would be at sea level with standard temperature and pressure, it would only hover, as the ratio is 1:1!  Laugh out loud
 
musang
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RE: Would A 747 Be Better With 2 GE-90s?

Wed Mar 10, 2004 4:17 am

I don't think it would meet the engine failure on take-off requirement.

The GE-90 and similar are rated to allow a 777 to continue the take-off safely if it loses one past V1, but a loaded 747 struggling airborne on one GE-90 would surely be quite interesting.

It would need a serious pylon re-design aswell. The one on the testbed 747 has insufficient ground clearance for (a) ordinary pilots and (b) gusty conditions. One on each side would mean landings would have to be consistently very close to perfectly level (in roll).

Since we're not all test pilots, and can't guarantee to keep it at zero bank on windy days, they'd need skids under the pods!!

QantasA332 - Agreed, the wing was designed for the existing engine arrangement from the bending moment standpoint. And other considerations aswell. In contrast, the A330 engines are hung at the same point as the A340's inners I believe. But this was designed into it so they could use a common wing.

Regards - Musang
 
ConcordeBoy
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RE: Would A 747 Be Better With 2 GE-90s?

Wed Mar 10, 2004 4:19 am

having four engines doesn't require lengthy and pricey ETOPS requirements

...yet


and many airlines prefer four engines for general safety

too bad said "safety" is at this point an uncorroboratory delusion  Big grin
Faire du ciel le plus bel endroit de la terre c'est impossible sans Concorde!
 
Klaus
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ConcordeBoy

Wed Mar 10, 2004 5:24 am

CB, could you keep ideology out of this for once?  Insane
 
Guest

RE: Would A 747 Be Better With 2 GE-90s?

Wed Mar 10, 2004 10:11 am

here's a 747 with a trent on it


View Large View Medium
Click here for bigger photo!

Photo © Joe G. Walker



i would like to see 4 ge90's on an A342.
 
fritzi
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RE: Would A 747 Be Better With 2 GE-90s?

Wed Mar 10, 2004 5:21 pm

ConcordeBoy,

"having four engines doesn't require lengthy and pricey ETOPS requirements"

...yet


Extended range twin engine opperations

How could a 4 engined jet be considered a twin?  Big grin
 
ConcordeBoy
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RE: Would A 747 Be Better With 2 GE-90s?

Thu Mar 11, 2004 2:45 am

"having four engines doesn't require lengthy and pricey ETOPS requirements"


How could a 4 engined jet be considered a twin?

Sorry bub, but you're making your own self look foolish with this one... not I.  Big grin

LROPS requirements will bear identical requirements, despite the change in acronym.
Faire du ciel le plus bel endroit de la terre c'est impossible sans Concorde!
 
jutes85
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RE: Would A 747 Be Better With 2 GE-90s?

Thu Mar 11, 2004 11:56 am

Doesn't the A380 have bigger engines, in diameter, than the GE90's?
nothing
 
ha763
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RE: Would A 747 Be Better With 2 GE-90s?

Thu Mar 11, 2004 1:33 pm

Well, it would look something like this:


View Large View Medium
Click here for bigger photo!

Photo © Je89 W.
View Large View Medium
Click here for bigger photo!

Photo © Je89 W.

 
QantasA332
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RE: Would A 747 Be Better With 2 GE-90s?

Thu Mar 11, 2004 3:37 pm

Doesn't the A380 have bigger engines, in diameter, than the GE90's?

With just a little bit of searching and referencing, you could have easily found out yourself...I would rather not have to do it for you. Anyway, no, the GE90 is still the largest engine in terms of diameter. Diameters are as follows, in inches:

General Electric GE90 94B/115B (777) = 134/135
Rolls Royce Trent 900 (A380) = 116
Engine Alliance GP 7270/7277 (A380) = 116.7/124

Keep in mind that for four-engined aircraft (even ones as large as the A380), the powerplants usually aren't the most powerful they can be, because there being so many of them, it simply isn't necessary.

Cheers,
QantasA332
 
DfwRevolution
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RE: Would A 747 Be Better With 2 GE-90s?

Sat Mar 13, 2004 7:57 am

A little bit of irony regarding Ha763's post. The engines next to the GE90 on the General Electric testbed aircraft are Pratts. When asked why, a GE employee said "Because they're cheaper."

Ryan
 
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Starlionblue
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RE: Would A 747 Be Better With 2 GE-90s?

Sat Mar 13, 2004 10:29 pm

Fly2hmo said:
I'm not talking back to anybody, but everything I've read and heard (not only in the forums) is that today's engines are so reliable, that the less you have, the safer it is. Back in the early days of flight and until the advent of ETOPS it was the opposite, the more engines you had, the safer it was.


Close but not quite. It's not "safer" with fewer engines, but dispatch reliability can be a tad higher. This is because there are fewer things that can go wrong, delaying departure. 4 engines=more moving parts that can break down.


"There are no stupid questions, but there are a lot of inquisitive idiots." - John Ringo
 
Saleem
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RE: Would A 747 Be Better With 2 GE-90s?

Mon Mar 15, 2004 3:43 pm

What's about 2 GE90 and remaining 2 are present one. So engines will be 4 and with more power. A unique combination.  Smokin cool
 
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Starlionblue
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RE: Would A 747 Be Better With 2 GE-90s?

Mon Mar 15, 2004 4:50 pm

That sure would look cool.
"There are no stupid questions, but there are a lot of inquisitive idiots." - John Ringo
 
fritzi
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RE: Would A 747 Be Better With 2 GE-90s?

Mon Mar 15, 2004 5:34 pm

"having four engines doesn't require lengthy and pricey ETOPS requirements"

...yet



Sorry bub, but you're making your own self look foolish with this one... not I.

LROPS requirements will bear identical requirements, despite the change in acronym


ETOPS was being discussed, not LROPS. Two different things...
 
mlsrar
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RE: Would A 747 Be Better With 2 GE-90s?

Tue Mar 16, 2004 7:32 am

Sorry bub, but you're making your own self look foolish with this one... not I.

LROPS requirements will bear identical requirements, despite the change in acronym


United has long since applied the ETOPS maintenance and A-check standards to their entire fleet as it has improve dispatch reliability, regardless of whether or not the aircraft is a twin or a quad.

Newer entrants to the certification process are encouraged to do so, and Northwest is using ETOPS practices across its long-haul fleet.
I mean, for the right price I’ll fight a lion. - Mike Tyson
 
Klaus
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RE: Would A 747 Be Better With 2 GE-90s?

Tue Mar 16, 2004 9:15 am

And the A340-500/600 are designed to ETOPS standards (as is the A380).
 
Fly2HMO
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RE: Would A 747 Be Better With 2 GE-90s?

Tue Mar 16, 2004 9:57 am

Interesting replies guys....

But, nobody has mentioned anything about costs... cheaper? the same? more expensive? Won't the much improved GE-90's efficiency justify the cost of installing them?

Anyways, would researching the possibility of doing this in a 747 even be worth it?!?!  Confused
 
prebennorholm
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RE: Would A 747 Be Better With 2 GE-90s?

Tue Mar 16, 2004 10:08 am

ETOPS and proposed LROPS are not the same.

Proposed LROPS rules adopt many or all maintenance and equipment capability related things from ETOPS.

But first of all, LROPS = "ETOPS-99,999" meaning that a quad LROPS plane doesn't need to zig-zag to stay within certain minutes flight time from alternates.

Secondly, LROPS planes will in many cases of equipment failure still maintain sufficient redundancies on electrical, hydraulic, aircon systems etc. and can maintain a high cruising altitude to destination when an ETOPS plane must divert. And must often descend to "safe pressure altitude".

The advantages of non-ETOPS quads are all maintained with LROPS. When quads are built and maintained to ETOPS standards (proposed LROPS rules), as many already are, then it is a minor disadvantage to the airline bean counters compared to current quad minimum standards.

I'm not an airline bean counter, but an ordinary passengers, and I regard it as a minor advantage.

There is for instance no valid reason why a long range quad shall not meet the same baggage compartment fire control standards as an ETOPS plane. Which for historic reasons is not the case today.

Happy landing, Preben Norholm
Always keep your number of landings equal to your number of take-offs
 
sllevin
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RE: Would A 747 Be Better With 2 GE-90s?

Tue Mar 16, 2004 11:21 am

Won't happen because it won't actually work.

Well, it would with both engines running -- you'd still have 240,000 pounds of thrust.

but what about when you lose one?

In the current 747, you go down to 180,000 pounds of thrust, with 60,000 pounds of loss on one side. The "747 twin" would drop to just 120,000 pounds, all asymetrical, and would fall from the sky at high weights  Smile

Now, 4 GE90's...humm...although I doubt the wing could handle the increased loading.

Steve
 
cancidas
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RE: Would A 747 Be Better With 2 GE-90s?

Tue Mar 16, 2004 1:35 pm

4 engines 4 long haul!  Smile/happy/getting dizzy
"...cannot the kingdom of salvation take me home."
 
DfwRevolution
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RE: Would A 747 Be Better With 2 GE-90s?

Tue Mar 16, 2004 1:51 pm

I know Boeing would never get away with it, but I'd love for Boeing to paint as big as possible on the 777-300ER testbed-

2 GOOD 2 USE 4 ENGINES 4 LONGHAUL

If you're going to have a multi-billion dollar corporate rivalry, you might as well have some fun with it!  Nuts
 
QantasA332
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RE: Would A 747 Be Better With 2 GE-90s?

Tue Mar 16, 2004 1:58 pm

How about "4 engines 4 longhaul 2 be 2 good 4 Boeing 2 beat!" ? Okay okay, quite corny, I know... Laugh out loud

Cheers,
QantasA332
 
MD-90
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RE: Would A 747 Be Better With 2 GE-90s?

Wed Mar 17, 2004 2:39 am

Nah,

2 GOOD 2 USE 4 ENGINES 4 LONGHAUL

is much better!
 
ConcordeBoy
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RE: Would A 747 Be Better With 2 GE-90s?

Wed Mar 17, 2004 3:02 am

Nah,

2 GOOD 2 USE 4 ENGINES 4 LONGHAUL

is much better!




Agreed  Big thumbs up
Faire du ciel le plus bel endroit de la terre c'est impossible sans Concorde!

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