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Would A 747 Be Better With 2 GE-90s?  
User currently offlineFly2hmo From , joined Dec 1969, posts, RR:
Posted (10 years 4 months 2 weeks 4 days 5 hours ago) and read 4163 times:

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

34 replies: All unread, showing first 25:
 
User currently offlineDeltaGuy From , joined Dec 1969, posts, RR:
Reply 1, posted (10 years 4 months 2 weeks 4 days 4 hours ago) and read 3601 times:

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


User currently offlineSean1234 From United States of America, joined Aug 2000, 411 posts, RR: 0
Reply 2, posted (10 years 4 months 2 weeks 4 days 2 hours ago) and read 3557 times:

You would also have less drag by having two engine nacelles instead of four.

User currently offlineDavid b. From United States of America, joined Jun 2001, 3148 posts, RR: 5
Reply 3, posted (10 years 4 months 2 weeks 4 days 2 hours ago) and read 3540 times:

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
User currently offlineQantasA332 From Australia, joined Dec 2003, 1500 posts, RR: 26
Reply 4, posted (10 years 4 months 2 weeks 4 days 2 hours ago) and read 3541 times:

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]

User currently offlineFly2hmo From , joined Dec 1969, posts, RR:
Reply 5, posted (10 years 4 months 2 weeks 3 days 23 hours ago) and read 3475 times:

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


User currently offlineMITaero From United States of America, joined Jul 2003, 497 posts, RR: 8
Reply 6, posted (10 years 4 months 2 weeks 3 days 22 hours ago) and read 3452 times:

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.


User currently offlineSEAPete From United States of America, joined Mar 2004, 67 posts, RR: 0
Reply 7, posted (10 years 4 months 2 weeks 3 days 14 hours ago) and read 3351 times:

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
User currently offline727200er From Canada, joined Mar 2004, 318 posts, RR: 0
Reply 8, posted (10 years 4 months 2 weeks 3 days 11 hours ago) and read 3310 times:

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
User currently offlineMighluss From Spain, joined Oct 2001, 945 posts, RR: 8
Reply 9, posted (10 years 4 months 2 weeks 3 days 11 hours ago) and read 3288 times:

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.
User currently offlineFritzi From United Arab Emirates, joined Jun 2001, 2762 posts, RR: 2
Reply 10, posted (10 years 4 months 2 weeks 3 days 10 hours ago) and read 3262 times:

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


User currently offlineMusang From United Kingdom, joined Apr 2001, 861 posts, RR: 7
Reply 11, posted (10 years 4 months 2 weeks 3 days 5 hours ago) and read 3179 times:

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


User currently offlineConcordeBoy From , joined Dec 1969, posts, RR:
Reply 12, posted (10 years 4 months 2 weeks 3 days 5 hours ago) and read 3178 times:

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


User currently offlineKlaus From Germany, joined Jul 2001, 21406 posts, RR: 54
Reply 13, posted (10 years 4 months 2 weeks 3 days 4 hours ago) and read 3157 times:

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

User currently offlineRoberta From , joined Dec 1969, posts, RR:
Reply 14, posted (10 years 4 months 2 weeks 2 days 23 hours ago) and read 3113 times:

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.


User currently offlineFritzi From United Arab Emirates, joined Jun 2001, 2762 posts, RR: 2
Reply 15, posted (10 years 4 months 2 weeks 2 days 16 hours ago) and read 3063 times:

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


User currently offlineConcordeBoy From , joined Dec 1969, posts, RR:
Reply 16, posted (10 years 4 months 2 weeks 2 days 7 hours ago) and read 3005 times:

"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.


User currently offlineJutes85 From , joined Dec 1969, posts, RR:
Reply 17, posted (10 years 4 months 2 weeks 1 day 22 hours ago) and read 2918 times:

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

User currently offlineHa763 From United States of America, joined Jan 2003, 3632 posts, RR: 5
Reply 18, posted (10 years 4 months 2 weeks 1 day 20 hours ago) and read 2895 times:
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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.



User currently offlineQantasA332 From Australia, joined Dec 2003, 1500 posts, RR: 26
Reply 19, posted (10 years 4 months 2 weeks 1 day 18 hours ago) and read 2881 times:

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


User currently offlineDfwRevolution From United States of America, joined Jan 2010, 960 posts, RR: 51
Reply 20, posted (10 years 4 months 2 weeks 2 hours ago) and read 2718 times:

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


User currently offlineStarlionblue From Greenland, joined Feb 2004, 16991 posts, RR: 67
Reply 21, posted (10 years 4 months 1 week 6 days 11 hours ago) and read 2654 times:

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."
User currently offlineSaleem From Pakistan, joined Mar 2000, 194 posts, RR: 0
Reply 22, posted (10 years 4 months 1 week 4 days 18 hours ago) and read 2576 times:

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

User currently offlineStarlionblue From Greenland, joined Feb 2004, 16991 posts, RR: 67
Reply 23, posted (10 years 4 months 1 week 4 days 17 hours ago) and read 2566 times:

That sure would look cool.


"There are no stupid questions, but there are a lot of inquisitive idiots."
User currently offlineFritzi From United Arab Emirates, joined Jun 2001, 2762 posts, RR: 2
Reply 24, posted (10 years 4 months 1 week 4 days 16 hours ago) and read 2556 times:

"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...


25 Mlsrar : Sorry bub, but you're making your own self look foolish with this one... not I. LROPS requirements will bear identical requirements, despite the chang
26 Klaus : And the A340-500/600 are designed to ETOPS standards (as is the A380).
27 Post contains images Fly2hmo : Interesting replies guys.... But, nobody has mentioned anything about costs... cheaper? the same? more expensive? Won't the much improved GE-90's effi
28 Prebennorholm : ETOPS and proposed LROPS are not the same. Proposed LROPS rules adopt many or all maintenance and equipment capability related things from ETOPS. But
29 Post contains images Sllevin : 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 whe
30 Post contains images Cancidas : 4 engines 4 long haul!
31 Post contains images DfwRevolution : 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 LON
32 Post contains images QantasA332 : How about "4 engines 4 longhaul 2 be 2 good 4 Boeing 2 beat!" ? Okay okay, quite corny, I know... Cheers, QantasA332
33 MD-90 : Nah, 2 GOOD 2 USE 4 ENGINES 4 LONGHAUL is much better!
34 Post contains images ConcordeBoy : Nah, 2 GOOD 2 USE 4 ENGINES 4 LONGHAUL is much better! Agreed
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