BOEING747400
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Boeing 744 With 2 GE 90-115 Engines

Wed Aug 07, 2002 4:00 pm

I wondered whether or not 2 GE 90-115 engines (same ones on the Boeing 773 Long Range) could really power a Boeing 744 because the total thrust is around 230,000 lbs. which pretty much equals 4 engines with 57,500 lbs. thrust? But it'd be impossible to fit those huge engines under the wings of a Boeing 744 so they'd have to increase the space between the ground and the wings to do it? What do you think? Thanks.
 
AJ
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RE: Boeing 744 With 2 GE 90-115 Engines

Wed Aug 07, 2002 4:54 pm

Here's a 747 classic with a GE90 in the #2 position:
http://www.air-and-space.com/salval99/747%20ge90%20al.jpg
 
Guest

RE: Boeing 744 With 2 GE 90-115 Engines

Wed Aug 07, 2002 5:09 pm

There has been - in the past - considerations to fit airplanes with other engines (even in numbers) for airplanes, I remember people considering to replace the 4 engines of DC8s with 2 engines of equivalent total thrust...
I doubt that it will ever be achieved... I flew the 707 for many years, which was an outstanding airplane for its size, and considerations were made to retrofit the JT3D engines for CFM-56s... like it was done with the DC8s...
But, Mr. Boeing wanted to sell new airplanes (good marketing strategy)... By all means dont help to keep the old airplanes flying... The 707-700 series with CFM-56 flew as a prototype... the KC-135s (707 tankers) got these CFM-56s, but all the 707s got their ticket for retirement in the deserts, or as restaurants near airports... I doubt any 747 will ever be re-engined, into a twin engine aircraft... as you say the ground clearance would be a problem.
The original 747, at a weight of 710,000 lbs flew with 4 engines of 43,500 lbs of thrust... it is correct to say that 2 engines providing equivalent thrust could be considered... well, actually that is not even true...
Aircraft certification (FAR/JAR 25) require certain gradient of climb (second segment) for an engine failure after V1... with a 4 engine aircraft, the gradient required is 3.0%... with the loss of 1 engine... 25% of power loss...
With a twin engine aircraft the gradient required is 2.4% with the loss of one engine after V1... with 50% power loss... it would take quite powerful engines to achieve that performance level on a "twin engine" 747...
I am a notorious opponent of "twin engine ETOPS" operations, because I am convinced that there will be a ditching of a twin jet one day in high seas, I hope with no casualties... then everybody will say, "is this flight with a 747 rather than a 767 or 777...?"
I had an acquaintance of mine, 767 captain, who had to drag his airplane to Keflavik, Iceland on one engine... and perform an ILS with minimum visibility... As far as I am concerned, I love my old 747 beasts with 4 engine redundancy when I cross the Atlantic Ocean 6 or 8 times a month...
(s) Skipper

 
CPH-R
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RE: Boeing 744 With 2 GE 90-115 Engines

Wed Aug 07, 2002 5:30 pm

AJ: That is one huuuge engine!

I seem to recall that when 747's are stripped, they usually hang a few blocks of concrete in as a replacement so the weight won't shift towards the rear.

IF a 747 was to be equipped with two GE90-115 instead of 4, say, RB211-524's, won't that have a impact on the weight distribution?
 
sllevin
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RE: Boeing 744 With 2 GE 90-115 Engines

Fri Aug 09, 2002 12:38 pm

The trouble with the two-engine 747 is that you have to factor in performance with one engine out.

Currently, while a 747 has 240,000 pounds of thrust, with an engine out, it still has 180,000 pounds of thrust, with only 60,000 pounds asymetrical.

Steve
 
cloudy
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RE: Boeing 744 With 2 GE 90-115 Engines

Fri Aug 09, 2002 6:09 pm

As has been said in other threads, the problem is not
really the reduction of engine redundancy.

The problem is the possibility of engine failure on takeoff. The 777 is more overpowered than the 747 for this reason. It has to be able to at least maintain altitude(even climb?) should one engine quit on takeoff. You need less extra thrust for this if you have 4 engines then if you have two.

So even if the 777 is equivalent in total thrust to a 747, you are not done yet. You have to compensate somehow for having 1/2 power rather than 3/4 on an engine out takeoff.
You need even more thrust.

At least that is what I understand from what I've read.
 
sllevin
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RE: Boeing 744 With 2 GE 90-115 Engines

Sat Aug 10, 2002 3:48 am

Cloudy;

I forget the specific engine out minima, but be assured that there is no jetliner operating today that cannot climb with an engine out  Smile

Steve
 
Marcus
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RE: Boeing 744 With 2 GE 90-115 Engines

Thu Aug 15, 2002 8:51 am

I am a notorious opponent of "twin engine ETOPS" operations, because I am convinced that there will be a ditching of a twin jet one day in high seas, I hope with no casualties
****************************
If the Azores islands were not close to them, that Canadian A330 would have been the first.
Kids!....we are going to the happiest place on earth...TIJUANA! signed: Krusty the Clown
 
jetsetter
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RE: Boeing 744 With 2 GE 90-115 Engines

Thu Aug 15, 2002 11:16 am

Yeah, but both engines went out on that aircraft, not just one, due to a fuel leak I think. Same thing could have happened with a 4 engined aircraft.
 
L-188
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RE: Boeing 744 With 2 GE 90-115 Engines

Thu Aug 15, 2002 7:33 pm

B747skipper...have I got one for you....

The original proposal for the E-3 by Boeing was to use 8 General Electric TF-34 engines. They would have been slung two to a pod just like on the B-52.

Apparently Boeing thought that they could squeeze more range out of the 707 by going to the eight engine configuration but the proposal later was changed to keep the normal TF33's
OBAMA-WORST PRESIDENT EVER....Even SKOORB would be better.
 
Alessandro
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RE: Boeing 744 With 2 GE 90-115 Engines

Sat Dec 22, 2007 11:51 pm

My dream would be to fit the AN-225 with 3 GE-90-115 engines... Wink
From New Yorqatar to Califarbia...
 
3MilesToWRO
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RE: Boeing 744 With 2 GE 90-115 Engines

Sun Dec 23, 2007 12:48 am

...on each side  Wink

(I've been warned this message was too short, but I hope it won't get cancelled  Wink )
 
QantasHeavy
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RE: Boeing 744 With 2 GE 90-115 Engines

Sun Dec 23, 2007 1:54 am

Reminds me of the urban legend of that great "famous ATC transcripts" email that surfaces every few months...

something to the effect of...

An F16 declares an emergency and requests priority landing is told by the tower he'll have to get behind an inbound B-52 which had already declared an emergency... for one engine out... to which the Falcon driver repsonds... "Oh no, of course, give priority to the 52 on the dreaded 7 engine approach!".

That whole email is a great one... lots of good SR-71 humor as well.
 
Alessandro
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RE: Boeing 744 With 2 GE 90-115 Engines

Sun Dec 23, 2007 2:08 am

3M, I calculated the preformance of 3 GE-90-115 and it would be similar to the current 6 engines...
From New Yorqatar to Califarbia...
 
QantasHeavy
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RE: Boeing 744 With 2 GE 90-115 Engines

Sun Dec 23, 2007 2:12 am

There is a great photo on a.net in the altered images section of a KLM 747-400 with two GE-90s on it. Someone did a great job photoshopping it... looks real!
 
andz
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RE: Boeing 744 With 2 GE 90-115 Engines

Sun Dec 23, 2007 5:30 am



Quoting BOEING747400 (Thread starter):
Posted Wed Aug 7 2002 18:00:41 your local time (5 years 4 months 2 weeks 4 days 13 hours ago)

Wow, I have seen old threads resurrected but this takes the prize! I didn't look at the age of the thread until I saw B747Skipper had posted  Smile
After Monday and Tuesday even the calendar says WTF...
 
OldAeroGuy
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RE: Boeing 744 With 2 GE 90-115 Engines

Sun Dec 23, 2007 4:57 pm



Quoting Cloudy (Reply 5):
It has to be able to at least maintain altitude(even climb?) should one engine quit on takeoff. You need less extra thrust for this if you have 4 engines then if you have two.



Quoting Sllevin (Reply 6):
I forget the specific engine out minima, but be assured that there is no jetliner operating today that cannot climb with an engine out

For second segment takeoff climb (gear up to 400' AGL or higher) with one engine inoperative, the minimum climb gradient for a twin is 2.4% and a quad is 3.0%.

As others have stated, this is why the all engine thrust to weight ratio for a twin must be higher than than a quad.
Airplane design is easy, the difficulty is getting them to fly - Barnes Wallis
 
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LTU932
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RE: Boeing 744 With 2 GE 90-115 Engines

Sun Dec 23, 2007 10:58 pm



Quoting QantasHeavy (Reply 14):
There is a great photo on a.net in the altered images section of a KLM 747-400 with two GE-90s on it. Someone did a great job photoshopping it... looks real!

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One good thing about this photoshop is that it can give you a rough impression of how double-slotted flaps on the upcoming 747-8 could look like.
 
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SEPilot
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RE: Boeing 744 With 2 GE 90-115 Engines

Mon Dec 24, 2007 12:33 pm



Quoting Marcus (Reply 7):
If the Azores islands were not close to them, that Canadian A330 would have been the first.

If the Canadian A330 had had 20 engines the result would have been the same. No matter how many engines you have they will all stop if you run completely out of fuel.
The problem with making things foolproof is that fools are so doggone ingenious...Dan Keebler
 
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Starlionblue
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RE: Boeing 744 With 2 GE 90-115 Engines

Mon Dec 24, 2007 12:45 pm



Quoting BOEING747400 (Thread starter):
I wondered whether or not 2 GE 90-115 engines (same ones on the Boeing 773 Long Range) could really power a Boeing 744 because the total thrust is around 230,000 lbs. w

Because:

Quoting Sllevin (Reply 4):
Currently, while a 747 has 240,000 pounds of thrust, with an engine out, it still has 180,000 pounds of thrust, with only 60,000 pounds asymetrical.

Exactly. Calculations are made with one engine out regardless of the number of engines. With an engine out, a 744 still has around 180k lb thrust. So a twin engine 744 would need engines with 180k lb of thrust. That's way beyond the state of the art today.

Quoting Marcus (Reply 7):
I am a notorious opponent of "twin engine ETOPS" operations, because I am convinced that there will be a ditching of a twin jet one day in high seas, I hope with no casualties

There might well be one someday. But ETOPS has been around for a while now. Don't you think it's "proven itself"? There will always be risk in any flying. Don't you think there are other things to worry about that deserve more of our focus?

Quoting SEPilot (Reply 18):
Quoting Marcus (Reply 7):
If the Azores islands were not close to them, that Canadian A330 would have been the first.

If the Canadian A330 had had 20 engines the result would have been the same. No matter how many engines you have they will all stop if you run completely out of fuel.

Damned straight.
"There are no stupid questions, but there are a lot of inquisitive idiots." - John Ringo
 
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SEPilot
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RE: Boeing 744 With 2 GE 90-115 Engines

Mon Dec 24, 2007 1:56 pm



Quoting Starlionblue (Reply 19):
There will always be risk in any flying. Don't you think there are other things to worry about that deserve more of our focus?

In fact, with the current state of reliability of jet engines, I suspect the chances of an uncontained failure leading to structural damage and a subsequent crash is higher than the chances of two unrelated engine failures, so it could be argued that twins are in fact safer than quads, as there are only two chances for an uncontained failure on a twin as opposed to four on a quad. Look at the El Al crash in Amsterdam; an engine fell off, which should have been survivable, but in doing so it struck the other one on that side knocking it off as well and extensively damaging the leading edge of the wing, which is what actually caused the loss of control and subsequent crash. Had it been a twin it would undoubtedly have landed safely.
The problem with making things foolproof is that fools are so doggone ingenious...Dan Keebler
 
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litz
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RE: Boeing 744 With 2 GE 90-115 Engines

Mon Dec 24, 2007 7:53 pm



Quoting LTU932 (Reply 17):

One good thing about this photoshop is that it can give you a rough impression of how double-slotted flaps on the upcoming 747-8 could look like.

Note the plane from nosewheel to mlg ... those engines just about touch - if not break - that plane.

Shows how low slung they'd really be ... maybe the bottom of the nacelle needs to be flattened 737-style!

- litz
 
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LTU932
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RE: Boeing 744 With 2 GE 90-115 Engines

Tue Dec 25, 2007 6:33 am



Quoting Litz (Reply 21):
Note the plane from nosewheel to mlg ... those engines just about touch - if not break - that plane.

Interesting. I didn't really notice that until you said it.

Quoting Litz (Reply 21):
Shows how low slung they'd really be ... maybe the bottom of the nacelle needs to be flattened 737-style!

What about the landing gear? Wouldn't it also need to be heavily re-designed to help with ground clearance issues in a hypothetical 747 with GE90s?
 
cobra27
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RE: Boeing 744 With 2 GE 90-115 Engines

Tue Dec 25, 2007 9:14 am

Just build an airplane with 1 engine, and that engine ge-90-115
 
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flyingclrs727
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RE: Boeing 744 With 2 GE 90-115 Engines

Wed Dec 26, 2007 3:37 pm



Quoting Marcus (Reply 7):

If the Azores islands were not close to them, that Canadian A330 would have been the first.

But the fuel problems that caused it to lose two engines would have also caused it to lose four engines. Either way it was lucky that the plane was close to the Azores. The fact that the Airbus A330 wing is optimized for takeoff and climbing probably made it a better glider.
 
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SEPilot
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RE: Boeing 744 With 2 GE 90-115 Engines

Wed Dec 26, 2007 7:11 pm



Quoting FlyingClrs727 (Reply 24):
But the fuel problems that caused it to lose two engines would have also caused it to lose four engines.

Another similar incident was the BA 747 that flew through a volcanic cloud and lost all 4 engines. Fortunately they were able to restart after they emerged from the cloud; again, that had nothing to do with the number of engines.
The problem with making things foolproof is that fools are so doggone ingenious...Dan Keebler
 
Viscount724
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RE: Boeing 744 With 2 GE 90-115 Engines

Wed Dec 26, 2007 10:33 pm



Quoting Cobra27 (Reply 23):
Just build an airplane with 1 engine, and that engine ge-90-115

Or the equally reliable P&W Canada PT6.  Smile


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rwessel
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RE: Boeing 744 With 2 GE 90-115 Engines

Fri Dec 28, 2007 3:41 am



Quoting FlyingClrs727 (Reply 24):
But the fuel problems that caused it to lose two engines would have also caused it to lose four engines.

A minor variable is that the same fuel leak on a quad would likely have been somewhat slower, since the high pressure fuel pump pushing the fuel out the broken pipe would have been smaller (given the smaller engine). That would likely have added some time to the equation.

Quoting FlyingClrs727 (Reply 24):
Either way it was lucky that the plane was close to the Azores.

Without doubt.
 
tdscanuck
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RE: Boeing 744 With 2 GE 90-115 Engines

Sun Dec 30, 2007 7:29 am



Quoting Rwessel (Reply 27):
A minor variable is that the same fuel leak on a quad would likely have been somewhat slower, since the high pressure fuel pump pushing the fuel out the broken pipe would have been smaller (given the smaller engine).

Not really. The high pressure fuel pumps are on the engine...the pump that was dumping fuel overboard in this case was the low pressure boost pump that's in the wing. The boost pumps are grossly oversized because they have to be able to do fuel transfers and to supply multiple engines at once (for when you have to burn all engines from one tank). The unloaded fuel flow rate for boost pumps between quads and twins isn't that big. Depending on which aircraft you pick, they could be bigger on the quad.

Tom.

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