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Do A 747400 Burn Less Fuel Than A L1011?  
User currently offline747400sp From United States of America, joined Aug 2003, 3498 posts, RR: 2
Posted (7 years 7 months 5 days 12 hours ago) and read 5038 times:

This may look like a stupid question, but I am going on what I have reed in a past post. In this past post, it was stated, that a L1011 burn more fuel than a 747 400 or A340 300. If this is true, then I have to ask this question, how? Both the 747 400 and A340 300 has four engines and the L1011 has three. It just do not make since to me.

23 replies: All unread, jump to last
 
User currently offlineZANL188 From United States of America, joined Oct 2006, 3503 posts, RR: 0
Reply 1, posted (7 years 7 months 5 days 12 hours ago) and read 5034 times:
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"Does a 747-400 burn less fuel than a L1011?"

I don't know, but I do know that in order for anyone to answer your question you need to define what answer you want.

Are you talking about fuel in regards to:

Engine? (Is the 747 engine (which one RR, GE, or PW) more efficient than the L1011 engine)
Available seat mile? (How much fuel it takes to move one seat one mile)
Specific fuel consumption?
Pound of thrust?

Probably best to go back to the thread you've already read and figure out in what form you want your answer, then come back here and let us know. If you don't do this you're going to get half a dozen different answers



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User currently offlineStarlionblue From Greenland, joined Feb 2004, 16999 posts, RR: 67
Reply 2, posted (7 years 7 months 5 days 12 hours ago) and read 5027 times:

Quoting 747400sp (Thread starter):
Both the 747 400 and A340 300 has four engines and the L1011 has three. It just do not make since to me.

Just the number of engines is not quite enough here. One GE90 can easily burn more fuel than all four engines on an RJ100.

As ZANL188 says, you need more info.

I would guess that on a 4000nm segment, the 747-400 burns less fuel per seat than the L-1011-500.



"There are no stupid questions, but there are a lot of inquisitive idiots."
User currently offline747400sp From United States of America, joined Aug 2003, 3498 posts, RR: 2
Reply 3, posted (7 years 7 months 5 days 11 hours ago) and read 5008 times:

Quoting ZANL188 (Reply 1):
"Does a 747-400 burn less fuel than a L1011?"

I don't know, but I do know that in order for anyone to answer your question you need to define what answer you want.

Are you talking about fuel in regards to:

Engine? (Is the 747 engine (which one RR, GE, or PW) more efficient than the L1011 engine)
Available seat mile? (How much fuel it takes to move one seat one mile)
Specific fuel consumption?
Pound of thrust?

Probably best to go back to the thread you've already read and figure out in what form you want your answer, then come back here and let us know. If you don't do this you're going to get half a dozen different answers

The thread was post a few weeks ago, so I am have a hard time finding it. I welcome a dozen different answers anyway, I can learn more that way.:D


User currently offlineFr8Mech From United States of America, joined Sep 2005, 5358 posts, RR: 14
Reply 4, posted (7 years 7 months 5 days 11 hours ago) and read 5002 times:

Quoting 747400sp (Reply 3):
I welcome a dozen different answers anyway, I can learn more that way.:D

But they will be contradictory unless you are looking at a specific parameter or measure. Apples to apples and oranges to oranges. It's like statistical analysis, the answers are there, you just jave to know what questions to ask, and how to ask them.



When seconds count...the police are minutes away.
User currently offlineStarlionblue From Greenland, joined Feb 2004, 16999 posts, RR: 67
Reply 5, posted (7 years 7 months 5 days 11 hours ago) and read 4999 times:

The answer is 42.


As has been stated, the variability of the question is pretty much endless. Airlines only care about numbers relating to their particular situation.



"There are no stupid questions, but there are a lot of inquisitive idiots."
User currently offline747400sp From United States of America, joined Aug 2003, 3498 posts, RR: 2
Reply 6, posted (7 years 7 months 5 days 11 hours ago) and read 4990 times:

Quoting Fr8Mech (Reply 4):
But they will be contradictory unless you are looking at a specific parameter or measure. Apples to apples and oranges to oranges. It's like statistical analysis, the answers are there, you just jave to know what questions to ask, and how to ask them.



Quoting Starlionblue (Reply 5):
The answer is 42.


As has been stated, the variability of the question is pretty much endless. Airlines only care about numbers relating to their particular situation

Wow 42

Ok, let's just go with RR engines.


User currently offlineZvezda From Lithuania, joined Aug 2004, 10511 posts, RR: 64
Reply 7, posted (7 years 7 months 5 days 11 hours ago) and read 4976 times:

First, the number of engines is completely irrelevant, as Starlionblue points out.

On a per seat basis, a B747-400 will burn less fuel on the same mission than an L-1011 because the former has better aerodynamics, better structural efficiency, and the engines have lower SFC.

On a per trip basis for the same mission, I would expect the L-1011 to burn less because it carries a lot less structure and presents a smaller frontal area and a smaller wetted area, but that's just an educated guess.


User currently offline474218 From United States of America, joined Oct 2005, 6340 posts, RR: 9
Reply 8, posted (7 years 7 months 5 days 3 hours ago) and read 4896 times:

Simple math will answer your question:

747-400, fuel capacity 57,285 gallons. Maximum range 7,260 miles. Works out to 7.89 Gallons per miles.

L-1011-500, fuel capacity 31,867 gallons. Maximum range 5,280 miles. Works out to 6.04 gallons per mile.

You could carry it out a little further:

The 747 has four engines, so it each engine is burning 1.97 gallons per mile.

The L-1011 has three engines, so each engine is burning 2.01 gallons per mile.

Boeing did not specify which engine, Rolls, PW or GE so there numbers my be an average. So using the manufactures numbers the 747 is slightly more economical than the L-1011. However, since the 747 and the L-1011 are with in 2% of each other, individual airframe differences could make that 2% advantage go the other way.


User currently offline747400sp From United States of America, joined Aug 2003, 3498 posts, RR: 2
Reply 9, posted (7 years 7 months 5 days 2 hours ago) and read 4881 times:

Quoting 474218 (Reply 8):
Simple math will answer your question:

747-400, fuel capacity 57,285 gallons. Maximum range 7,260 miles. Works out to 7.89 Gallons per miles.

L-1011-500, fuel capacity 31,867 gallons. Maximum range 5,280 miles. Works out to 6.04 gallons per mile.

You could carry it out a little further:

The 747 has four engines, so it each engine is burning 1.97 gallons per mile.

The L-1011 has three engines, so each engine is burning 2.01 gallons per mile.

Boeing did not specify which engine, Rolls, PW or GE so there numbers my be an average. So using the manufactures numbers the 747 is slightly more economical than the L-1011. However, since the 747 and the L-1011 are with in 2% of each other, individual airframe differences could make that 2% advantage go the other way.

If was to put a 747 classic into this, how would it turn out?


User currently offlineZvezda From Lithuania, joined Aug 2004, 10511 posts, RR: 64
Reply 10, posted (7 years 7 months 5 days 2 hours ago) and read 4876 times:

Quoting 474218 (Reply 8):
Simple math will answer your question:

747-400, fuel capacity 57,285 gallons. Maximum range 7,260 miles. Works out to 7.89 Gallons per miles.

L-1011-500, fuel capacity 31,867 gallons. Maximum range 5,280 miles. Works out to 6.04 gallons per mile.

The numbers would be a lot nearer if the mission were the same.


User currently offlinePhilSquares From , joined Dec 1969, posts, RR:
Reply 11, posted (7 years 7 months 4 days 23 hours ago) and read 4839 times:

Quoting 474218 (Reply 8):
Simple math will answer your question:

Not quite an apples to apples comparison. I've never flown the 1011, but a 744 at MTOW in cruise will burn about 14-15 Tonnes/hour at cruise. At lighter weights it will be down to about 8 Tonnes/hour.

For the classic add about 2-3 Tonnes/hour for the same weight bracket.

I think, just a hunch, if you compare similar gross weights for the 744 and 1011, you would find the 744 would burn less fuel. I don't have any 1011 performance charts available so I can't give you a factual answer.


User currently offlineZeke From Hong Kong, joined Dec 2006, 8867 posts, RR: 75
Reply 12, posted (7 years 7 months 4 days 22 hours ago) and read 4831 times:

Some old average industry numbers I had from 10 years ago (note that the cost of running a L1011 has risen as it is almost impossible to get engine parts, and fuel costs has risen significantly)

Aircraft
Seats
Average cargo payload
Sector length
Operating cost
Fuel kg/seat
Operating cost/seat
Fuel flow/pax/nm (kg)

L-1011-100/200
310
6.6
1206
3720
7259
23.42
12
0.019

L-1011-500
223
5.45
2222
3829
7104
31.86
17.17
0.014

B747-200/300
374
8.33
3489
7300
10952
29.28
19.52
0.008

B747-400
396
8.89
4988
6859
10195
25.75
17.32
0.005



We are addicted to our thoughts. We cannot change anything if we cannot change our thinking – Santosh Kalwar
User currently offlineStarlionblue From Greenland, joined Feb 2004, 16999 posts, RR: 67
Reply 13, posted (7 years 7 months 4 days 18 hours ago) and read 4796 times:

Quoting 474218 (Reply 8):
747-400, fuel capacity 57,285 gallons. Maximum range 7,260 miles. Works out to 7.89 Gallons per miles.

L-1011-500, fuel capacity 31,867 gallons. Maximum range 5,280 miles. Works out to 6.04 gallons per mile.

You could carry it out a little further:

The 747 has four engines, so it each engine is burning 1.97 gallons per mile.

The L-1011 has three engines, so each engine is burning 2.01 gallons per mile.

Your math is fine, but your assumptions are unfortunately flawed. If you fill the tanks, you can't fly with anywhere near full payload since you will exceed MTOW by a fair margin. You need to check fuel quantities at MTOW with full payload for each.



"There are no stupid questions, but there are a lot of inquisitive idiots."
User currently offline474218 From United States of America, joined Oct 2005, 6340 posts, RR: 9
Reply 14, posted (7 years 7 months 4 days 12 hours ago) and read 4722 times:

Quoting Starlionblue (Reply 13):
Your math is fine, but your assumptions are unfortunately flawed. If you fill the tanks, you can't fly with anywhere near full payload since you will exceed MTOW by a fair margin. You need to check fuel quantities at MTOW with full payload for each.



Quoting PhilSquares (Reply 11):
Not quite an apples to apples comparison. I've never flown the 1011, but a 744 at MTOW in cruise will burn about 14-15 Tonnes/hour at cruise. At lighter weights it will be down to about 8 Tonnes/hour.

For the classic add about 2-3 Tonnes/hour for the same weight bracket.

I think, just a hunch, if you compare similar gross weights for the 744 and 1011, you would find the 744 would burn less fuel. I don't have any 1011 performance charts available so I can't give you a factual answer.

You all are making this harder than it really is: The question 747400sp asked was; "Do (Does) the 747-400 burn less fuel than the L-1011" and that's the question I answered. There was no mention of payload/weight/passenger seat miles/MTOW or anything else, just what the fuel burn difference. If an aircraft uses X amount of fuel to fly X distance that is its fuel burn. Sure you use more fuel at takeoff than cruse but you burn more at cruse that you do on landing, but it all gets added together to get the average fuel burn. Which is what I answered.


User currently offlineStarlionblue From Greenland, joined Feb 2004, 16999 posts, RR: 67
Reply 15, posted (7 years 7 months 4 days 12 hours ago) and read 4714 times:

Quoting 474218 (Reply 14):
. If an aircraft uses X amount of fuel to fly X distance that is its fuel burn

With all due respect, but that's not what you answered. You answered with the fuel burn for the max fuel range, just one possible (and pretty uncommon) scenario. And you didn't count reserves.



"There are no stupid questions, but there are a lot of inquisitive idiots."
User currently offline474218 From United States of America, joined Oct 2005, 6340 posts, RR: 9
Reply 16, posted (7 years 7 months 4 days 7 hours ago) and read 4647 times:

Quoting Starlionblue (Reply 15):
With all due respect, but that's not what you answered. You answered with the fuel burn for the max fuel range, just one possible (and pretty uncommon) scenario. And you didn't count reserves.

747400sp didn't ask about reserves either. He asked "Do A 747400 Burn Less Fuel Than A L-1011?" So thats what I answered. I suggest you RTFQ.


User currently offlineStarlionblue From Greenland, joined Feb 2004, 16999 posts, RR: 67
Reply 17, posted (7 years 7 months 4 days 5 hours ago) and read 4622 times:

Quoting 474218 (Reply 16):

747400sp didn't ask about reserves either. He asked "Do A 747400 Burn Less Fuel Than A L-1011?" So thats what I answered. I suggest you RTFQ.

Tsk tsk. Foul language?

I read the question, and it's plenty open for interpretation. Without a few more parameters than in the original question, there is no way to make a valid comparison.

Airliners are not cars. Dividing max fuel quantity by max range does not result in a valid number since it is unknown whether the range number for either aircraft was tabulated at MTOW or simply with max fuel and otherwise empty aircraft apart from crew.



"There are no stupid questions, but there are a lot of inquisitive idiots."
User currently offlinePhilSquares From , joined Dec 1969, posts, RR:
Reply 18, posted (7 years 7 months 3 days 23 hours ago) and read 4583 times:

Quoting 474218 (Reply 16):
747400sp didn't ask about reserves either. He asked "Do A 747400 Burn Less Fuel Than A L-1011?" So thats what I answered. I suggest you RTFQ.

I'd have to agree with Starlionblue on this issue. Your assumption of "max" range is really meaningless since that figure is somewhat of a unrealistic number to begin with. I tried to give a general fuel burn from the 400 and the classic in hopes someone who had flown the 1011 would be able to offer a similar figure.

As I stated previously, my gut feeling is the 400 burns less on an hourly basis at the same gross weights when compared to the 1011.

FYI....no need to get nasty in here. People are just trying to give the best answers they can....


User currently offline411A From United States of America, joined Nov 2001, 1826 posts, RR: 8
Reply 19, posted (7 years 7 months 3 days 23 hours ago) and read 4580 times:

No speculation...facts.

L1011, standard body airplane.

Fitted with RB.211-22B engines, with a takeoff at max weight, the average fuel consumption would be, 8.3 metric tons/hour for a six hour sector.

Fitted with RB.211-524B4 engines, 8.2 metric tons/hr, same six hour sector.

L1011, short body airplane (IE, -500 model), 8.1 metric tons/hr for a six hour+ sector.

All fuel consumption figures are averaged oiver the sector quoted.

IF an engine should fail enroute, and the flight is continued to destination, once the driftdown maneuver had been accomplished. the average TAS is 430 knots, and the fuel consumption is increased by 500 kg/hr.
All models, mid cruise weights.


User currently offlineTristarSteve From Sweden, joined Nov 2005, 3980 posts, RR: 34
Reply 20, posted (7 years 7 months 3 days 18 hours ago) and read 4542 times:

Well I have departed aircraft from ARN to New York JFK and EWR.
Looking at the departure fuel loads the average Fuel in Tanks for a
B744 is 90-95tons.
Many years ago we sent TWA Tristar 1s to JFK and they went out with about full tanks which is about 70 tons. But I remember that it was marginal with a -1 aircraft, and needed en-route reclearance to make it. The -100 was no problem.
For comparison I now depart B777 to EWR and the load is about 60tons.
So yes the B744 uses more fuel on the same sector than the L1011 (but carries more pax).


User currently offlineStarlionblue From Greenland, joined Feb 2004, 16999 posts, RR: 67
Reply 21, posted (7 years 7 months 3 days 16 hours ago) and read 4524 times:

Quoting 411A (Reply 19):

Fitted with RB.211-22B engines, with a takeoff at max weight, the average fuel consumption would be, 8.3 metric tons/hour for a six hour sector.

Fitted with RB.211-524B4 engines, 8.2 metric tons/hr, same six hour sector.

L1011, short body airplane (IE, -500 model), 8.1 metric tons/hr for a six hour+ sector.

All fuel consumption figures are averaged oiver the sector quoted.

Finally some real world figures WITH THE UNDERLYING ASSUMPTIONS. Now if we can get the same for the 744 we'll be all set.



"There are no stupid questions, but there are a lot of inquisitive idiots."
User currently offlinePhilSquares From , joined Dec 1969, posts, RR:
Reply 22, posted (7 years 7 months 3 days 6 hours ago) and read 4448 times:

For a PW powered 744 taking off at MTOW would be as follows:
First 2 hours at FL 270 M.855 347 KIAS fuel burn is 3467kgs/eng or 13868kgs/hour

The remaining 4 hours is at 290 with a M.858 335 KIAS and a fuel burn of 3274kgs/eng or 13069kg/hour

However, you're still above your maximum landing weight at the end of the 6 hour flight. Assuming you're in a 396 or 398 aircraft you'd only be down to about 316 to 318 tonnes. The max landing weight is about 286,000Kgs so you still have another 2 hours to go. If you look at a PW freighter then the landing weight goes up to 302 tonnes, so you would only have one hour to burn fuel to land.

My point of this exercise is it's like comparing apples to oranges: it doesn't really tell you anything worthwhile.

If you want to compare fuel burn at similar mission profiles, that's another thing..


User currently offlineZvezda From Lithuania, joined Aug 2004, 10511 posts, RR: 64
Reply 23, posted (7 years 7 months 3 days 4 hours ago) and read 4425 times:

PhilSquares and Starlionblue are correct. The original question was about as specific as "How long is a piece of string?" and just as open to interpretation.

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