Gigneil From United States, joined Nov 2002, 13403 posts, RR: 79 Reply 1, posted (2 years 6 months 5 days 3 hours ago) and read 18050 times:
The A320 is not 20% less efficient than a 737-800. Period. AVITAS rates them too close to call last time I checked.
The 767-400ER is more fuel efficient than an A330-200 because they're not even in the same league in terms of payload/range capability. Much like the 737-900ER and A321 will be much more efficient than a 757, but doesn't do much good if you're leaving people and cargo on the ramp.
The 747-8 doesn't even exist yet. Arguably, a plane to fly in 2009 should be much more efficient.
NorCal From United States, joined Mar 2005, 1248 posts, RR: 1 Reply 3, posted (2 years 6 months 5 days 3 hours ago) and read 18023 times:
The 738 might, hence the *might*, be slightly more fuel efficient than the A320, but this has to do with the fact that it is lighter (smaller cross-section=less weight). However it is no where even close to 20% more efficient than the A320, Airbus wouldn't sell very many A320s if they were 20% less efficient. The order book speaks for itself on this issue. That difference that you have is like a 787 vs. a 767.
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DfwRevolution From United States, joined Mar 2004, 7524 posts, RR: 53 Reply 5, posted (2 years 6 months 5 days 3 hours ago) and read 17955 times:
Quoting FlyDreamliner (Thread starter): Both 747-8 and 777-300 get nearly 10 percent better fuel consumption per passenger mile than A340-600. Why is this?
In response to the A346 re: 748 and 773ER, the main culprit is structural weight. The A340 (-500/600) are much heavier than their respective 777LR counterparts.
This has less to do with engine configuration than design philosophy. Boeing optimized the 777-200A for heavier MTOW while Airbus optimized the A333/A343 for mid-range opperations. When Airbus developed the A340 "NG," they had to reinforce more structures than Boeing, and had to stretch the narrower fuselage longer than the wider 777. Boeing reached their desired MTOW with less dramatic re-engineering.
Note that: (1) the A333 is much lighter than the 772A, (2) Airbus was able to develop a shrink variant (A332) while Boeing was unable to shrink the 777, but (3) the A340NG is much heavier than the 777LR.
Also, the 747-800 is arguably the most structurally efficent 747 ever. Boeing internal studies from the 747-X (late 90s) showed that a 1-2 meter stretch would result in the most volume/capacity per structural lb than any other length. This is the exact amount taken by Boeing with the 748 stretch.
SSTsomeday From Canada, joined Oct 2006, 710 posts, RR: 0 Reply 6, posted (2 years 6 months 5 days 3 hours ago) and read 17925 times:
Oh boy - I have a feeling that this thread is going to be a bloodbath...
Thank you, DFWevolution and FLYdreamliner for such comprehensive information.
Math is not my forte. Perhaps you can elaborate, FLY, on how the statistics indicate a 20% difference in fuel consumption between the 737 and 320. The 320's success would indicate that such a huge difference seems unlikely.
But I know I will follow this thread with interest...
Quoting Glom (Reply 2): How have you chosen those numbers? Have you consulted the payload-range charts?
Quoting Gigneil (Reply 1): The A320 is not 20% less efficient than a 737-800. Period. AVITAS rates them too close to call last time I checked.
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Quoting SSTsomeday (Reply 6): Perhaps you can elaborate, FLY, on how the statistics indicate a 20% difference in fuel consumption between the 737 and 320.
20% delta in SFC between the A320 and 738 is just not possible. If anything, it's probably single digit (2-3%) favor of the 737NG on account of lighter OEW/Seat and AVP Blended Winglets package. It really is close.
Gigneil is right, in many cases, the 737NG and A320 are so closely matched that the deciding factor can come down to a non-performance datum like finance terms and delivery slots.
Quoting SSTsomeday (Reply 6): The 320's success would indicate that such a huge difference seems unlikely.
The A320's recent order surge (2003-2005) is due in large part to a highly aggressive sales team and a speculative decision to boost production in 2001-2002. That has paid off big time, giving Airbus the ability to offer all sorts of delivery schedules and financing terms that knocked Boeing on their rear a few years in a row.
Stitch From United States, joined Jul 2005, 12161 posts, RR: 51 Reply 9, posted (2 years 6 months 5 days 2 hours ago) and read 17880 times:
Of course those figures calculate maximum fuel volume being carried and the plane flying it's maximum distance with maximum passenger load (as defined by Airbus and Boeing, and not the customer). Essentially, they're just hypotheticals based on numbers that don't translate to how these planes are used by customers in "real" configurations and operations.
SSTsomeday From Canada, joined Oct 2006, 710 posts, RR: 0 Reply 11, posted (2 years 6 months 5 days 2 hours ago) and read 17741 times:
Quoting DfwRevolution (Reply 8): The A320's recent order surge (2003-2005) is due in large part to a highly aggressive sales team and a speculative decision to boost production in 2001-2002. That has paid off big time, giving Airbus the ability to offer all sorts of delivery schedules and financing terms that knocked Boeing on their rear a few years in a row.
That's very interesting. It's facinating to me that Boeing would fall behind for these reasons, as opposed to having an inferior aircraft. How can they let this happen?
Atmx2000 From United States, joined Oct 2004, 4564 posts, RR: 22 Reply 12, posted (2 years 6 months 5 days 1 hour ago) and read 17661 times:
Quoting DfwRevolution (Reply 5): In response to the A346 re: 748 and 773ER, the main culprit is structural weight. The A340 (-500/600) are much heavier than their respective 777LR counterparts.
It has been suggested that there is a much greater drag penalty that is reflected in cruise thrust requirements than would be expected due to just increased OEW.
Quoting SSTsomeday (Reply 11): That's very interesting. It's facinating to me that Boeing would fall behind for these reasons, as opposed to having an inferior aircraft. How can they let this happen?
Perhaps you have heard of 9/11, an event that more severely impacted Boeing's customers and caused Boeing to retrench a great deal.
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FlyDreamliner From United States, joined Jan 2006, 2115 posts, RR: 11 Reply 13, posted (2 years 6 months 5 days 1 hour ago) and read 17649 times:
I'm using data from www.boeing.com and www.airbus.com. You can say whatever you'd like, I never talked about payload, i simply showed what the per mile consumption for each aircraft was, and what the per seat mile consumption was, assuming every seat was full.
A320 came out years before 73G. The A320 is way better than 737 Classic. Their continued sales show that a lot of people like fleet commonality.
I was just posting numbers I found strange, not making any statements, I just wanted to know if people had explanations for these numbers. I wasn't trying to start an A vs. B debate.
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Atmx2000 From United States, joined Oct 2004, 4564 posts, RR: 22 Reply 14, posted (2 years 6 months 5 days 1 hour ago) and read 17604 times:
Quoting FlyDreamliner (Reply 13): I'm using data from www.boeing.com and www.airbus.com. You can say whatever you'd like, I never talked about payload, i simply showed what the per mile consumption for each aircraft was, and what the per seat mile consumption was, assuming every seat was full.
Quoted range does not equal range with a maxed out fuel capacity. Trade offs between revenue payload weight and fuel weight to stay under maximum take off weight limits usually mean for a weight limited aircraft that the fuel tanks won't be filled at the design payload, thus less fuel will be used than maximum fuel capacity. The ranges you provide are for design payloads, not payload after fuel capacity is maxed out.
ConcordeBoy is a twin supremacist!! He supports quadicide!!
Ruscoe From Australia, joined Aug 1999, 1019 posts, RR: 1 Reply 15, posted (2 years 6 months 5 days 1 hour ago) and read 17593 times:
I think the fundamental problem with comparing fuel consumption this way is that it does not take into account each companies philosophy with regard to payload range.
Airbus generally have more tankage than Boeing. This often gives them a greater range, but at a payload no-one would want to operate at on a regular basis. Boeing on the other hand limit tankage to the lowest likely payload that a customer is likely to want to use on a regular basis.
Put another way, with a typical payload if you fill the tanks on an Airbus you will probably go overweight, but on a Boeing you will probably be at about MTOW.
Thr Airbus philosophy probably gives more flexibility because you can sacrifice more payload for range, but in normal day to day ops I doubt it makes much difference.
This is a generalisation from memory, but I beleive it is the underlying reason why you can't compare fuel consumption the way the original poster has done.
MarcoT From Italy, joined May 2005, 217 posts, RR: 2 Reply 16, posted (2 years 6 months 5 days ago) and read 17503 times:
Quoting FlyDreamliner (Reply 13):
I'm using data from www.boeing.com and www.airbus.com. You can say whatever you'd like, I never talked about payload, i simply showed what the per mile consumption for each aircraft was, and what the per seat mile consumption was, assuming every seat was full.
The problem is that, when you divide _max fuel capacity_ by _max range with full pax_ for obtaining 'mile consumption' for each aircraft, you are also assuming (without realizing it) that max range with full pax is achieved taking off with the fuel tanks completely full, which is simply not true. In most cases doing so you'll end above MTOW ...
Instead you _should_ talk about payload.
Usually manufacturers claims something like 'max range with a payload of X tonnes -corresponding to a full load of N passengers and baggages- is Y nm'.
So, if you know the MTOW and the OEW (Operating Empty Weight) you can then calculate the _weight_ of the fuel used as MTOW - (OEW + X), and dividing by the (average) fuel density you obtain the quantity in litres/gallons whatever.
A couple of warnings:
First, the figures given are usually assuming standard fuel reserves. So if you use this data for calculating 'liters/km' you'll end up with an higher value than in reality, and short range aircraft are penalized proportionally more...
Also, for doing accurate comparison, you should investigate how much 'standard' reserves are standard...
Second, the OEW used by the manufacturers are the lightest they can get by. In airline service it really depends on the cabin furnitures and the various amenities installed. This should be kept in mind when doing comparison between different arlines and/or the manufacturers figures...
Too short space for my favorite hopelessly long winded one liner
Glom From United Kingdom, joined Apr 2005, 1981 posts, RR: 5 Reply 17, posted (2 years 6 months 5 days ago) and read 17441 times:
Your best bet, if you really want to go down this road, is to consult a bunch of payload-charts, picking the point with max fuel payload and work from there.
For example, going for the answer we already knew, looking at the 777 (source).
777-200LR
At maximum payload for full fuel, the ZFW will be ~408klb for a range of ~9350NM. The figures they used to reach these values are OEW of 320klb and max fuel capacity of 320.9lkb. Due to this, we may assume that the payload carried by 408lkb, is 88klb. It is carrying 88lkb over a distance of 9350NM using 321klb (yeah okay this includes reserves and stuff but what are you going to do?).
So, the fuel burn is 0.00039 lb fuel per lb payload per mile.
Now I can't find the charts for the A345. They used to be on the Airbus website, but they've taken them away (too embarassing probably).
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