David b. From United States of America, joined Jun 2001, 3148 posts, RR: 6 Reply 3, posted (9 years 3 months 2 weeks 10 hours ago) and read 3156 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.
QantasA332 From Australia, joined Dec 2003, 1500 posts, RR: 35 Reply 4, posted (9 years 3 months 2 weeks 10 hours ago) and read 3157 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.
Fly2hmo From , joined Dec 1969, posts, RR: Reply 5, posted (9 years 3 months 2 weeks 7 hours ago) and read 3091 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.
SEAPete From United States of America, joined Mar 2004, 67 posts, RR: 0 Reply 7, posted (9 years 3 months 1 week 6 days 22 hours ago) and read 2967 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!
Mighluss From Spain, joined Oct 2001, 931 posts, RR: 9 Reply 9, posted (9 years 3 months 1 week 6 days 19 hours ago) and read 2904 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!
anyway, I don't think that those 60.000lbs of fuel would last for a very long time...
Fritzi From United Arab Emirates, joined Jun 2001, 2762 posts, RR: 2 Reply 10, posted (9 years 3 months 1 week 6 days 18 hours ago) and read 2878 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!
Musang From United Kingdom, joined Apr 2001, 759 posts, RR: 7 Reply 11, posted (9 years 3 months 1 week 6 days 13 hours ago) and read 2795 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.
Ha763 From United States of America, joined Jan 2003, 3494 posts, RR: 6 Reply 18, posted (9 years 3 months 1 week 5 days 4 hours ago) and read 2511 times:
QantasA332 From Australia, joined Dec 2003, 1500 posts, RR: 35 Reply 19, posted (9 years 3 months 1 week 5 days 2 hours ago) and read 2497 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.
DfwRevolution From , joined Dec 1969, posts, RR: Reply 20, posted (9 years 3 months 1 week 3 days 10 hours ago) and read 2334 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."
Starlionblue From Hong Kong, joined Feb 2004, 15904 posts, RR: 66 Reply 21, posted (9 years 3 months 1 week 2 days 19 hours ago) and read 2270 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." - from Citadel by John Ringo
Fritzi From United Arab Emirates, joined Jun 2001, 2762 posts, RR: 2 Reply 24, posted (9 years 3 months 1 week 1 day ago) and read 2172 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 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 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
31 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 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 ConcordeBoy: Nah, 2 GOOD 2 USE 4 ENGINES 4 LONGHAUL is much better! Agreed
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