787 Fuel Burn Question

[WesternU]

I tried the search feature, but could not find anything, so I thought would post the question here.

Per Boeing's own statements, the 787 is supposed to have a 17% to 20% advantage over the 767 and A330 in fuel burn (on a per passenger seat basis, when compared to the 767-300ER and A330-200), however, when the 787-8 came out it, it has an ~6% fuel burn disadvantage when compared to the 763ER (didn't check on the A332), which cannot be made up with the additional 10 passengers (at max Y-only capacity) it can carry.  Now, I know that Boeing MAY be taking other items into consideration, such as lower maintenance costs and the speed difference (in AWS cargo isn't a factor), but per my calculations this still does not equate into the difference that should be there.  So, are the fuel burn numbers accurately reflected?

Note: since Boeing just started flight testing, I know we cannot get the initial "real" fuel burn numbers for another 9 to 10 months, but I am looking to see if the AWS estimates can better reflect the capabilities of the next-gen widebodies (A350 too.).  I am also trying to find any more specific stats on fuel burn, but that too may take a while, especially with testing going on.

Thanks,
WesternU

[Sami]

Figures may be very well a bit off in AWS database as 787 was just added (in a bit of an hurry too).. Have to check it.

(but the Boeing advert talks of 20% better fuel burns are always just PR guys dreams, so some sort of realism will be kept, at least until real figures can be obtained) 

[WesternU]

Hey Sami,

Your the man.   I know you try your best, so no worries there.  I just thought they were a little out of wack there.

[Sigma]

Has Boeing actually explictly mentioned the models it's comparing to when it says "20% better"?  All I can recall reading (or find on a quick search just now) is a Boeing statement in regards to "comparably-sized aircraft" which is a hazy statement at best.  The 787 is, oddly, a very heavy aircraft even empty and, with a much higher fuel capacity can weigh as much as 20% more on takeoff than a 767 or A330; so measured on a number of pounds moved to gallon, the 787 is technically more fuel-efficient even if it consumes the same amount of fuel as a much lighter plane (like the 767 or A330).

You can look at other official Boeing figures to get a rough idea of fuel economy and can see that the "20% figure" that PR throws around just doesn't jive up.  Carrying roughly (give or take a few) pax, the 787 has a fuel tank about 38% larger than a 764ER; and a range of about 44% more.  If indeed the 787 got "20% better fuel economy" it should be able to get a LOT further given it's fuel tank is so much larger.  It should easily go 9100+NM if it was indeed burning 20% less fuel for every pax onboard with as much fuel as it's got, but it can't even come close to that.

Given other Boeing information, I would say that the real-life (rather than PR-speak) fuel economy difference between the 787-8 and the 767-400ER is probably in the 5-10% range on the per-passenger level, and that's at best.

EDIT:  Found a site (  http://www.lissys.demon.co.uk/samp1/index.html  ) that did full modeling of the 787-8 using Piano-X, a tool used by airframe and engine manufacturers including Boeing, and they came up with an estimated fuel economy of 11402 lb/hr at cruise with the GEnx -- almost spot-on what Sami's got here.

[WesternU]

Hey Sigma,

Great stuff.   Thank you, I had forgotten about Piano-X (I also reviewed some details on it from Leeham.net, who also uses Piano-X).  I also agree that the marketing hype is a bit far fetched at times.   I have to check what I have still, but I am sure I have/seen some documentation that focuses on the 763ER (as a slightly smaller plane) and the A332 (as the slightly larger plane).  If you want I can see about finding a link for you, just let me know and I'll be happy to see what I can dig up. 

Now unfortunately, the wife is calling me, so I can not review more tonight, but I noticed that the report you got your figures on (from the main page at lissys) may not be the latest on the 787-8 that is out.  I quickly looked at the updated files from lissys (available when you download Piano-X) and you are able to see the latest figures, which include the latest mtow increases (late 2009) along with the more up to date estimated performance figures for the engines.  In that report it lists the Total Fuel Flow at 10443 lb/hr.  The older report (I can't tell, but the data used looks to be somewhere between 2006 and 2008) that lissys posted shows it at the 11402 lb/hr you mentioned, which is where the confusion may be generated (lissys stopped updating the report a while ago). 

Also don't forget, even though the fuel tanks are huge, the flight parameters may restrict how much fuel is used.  With the 242 passenger count (7633NM Range) flight profile used I believe they are weight restricted so the tanks are not full, plus they are carrying ~18K lbs of reserve fuel (diversion, holding, contingency).  In fact with max fuel (@ MTOW + payload of ~15K lbs) it can go 9685NM and with zero payload (OEW + max fuel), it can go 10056NM.

Again, interesting stuff and thank you again for your input and reminding me about the Piano-X reports. 

Best regards,
WesternU

[MM21]

Hey Sigma,

Great stuff.   Thank you, I had forgotten about Piano-X (I also reviewed some details on it from Leeham.net, who also uses Piano-X).  I also agree that the marketing hype is a bit far fetched at times.   I have to check what I have still, but I am sure I have/seen some documentation that focuses on the 763ER (as a slightly smaller plane) and the A332 (as the slightly larger plane).  If you want I can see about finding a link for you, just let me know and I'll be happy to see what I can dig up. 

Now unfortunately, the wife is calling me, so I can not review more tonight, but I noticed that the report you got your figures on (from the main page at lissys) may not be the latest on the 787-8 that is out.  I quickly looked at the updated files from lissys (available when you download Piano-X) and you are able to see the latest figures, which include the latest mtow increases (late 2009) along with the more up to date estimated performance figures for the engines.  In that report it lists the Total Fuel Flow at 10443 lb/hr.  The older report (I can't tell, but the data used looks to be somewhere between 2006 and 2008) that lissys posted shows it at the 11402 lb/hr you mentioned, which is where the confusion may be generated (lissys stopped updating the report a while ago). 

Also don't forget, even though the fuel tanks are huge, the flight parameters may restrict how much fuel is used.  With the 242 passenger count (7633NM Range) flight profile used I believe they are weight restricted so the tanks are not full, plus they are carrying ~18K lbs of reserve fuel (diversion, holding, contingency).  In fact with max fuel (@ MTOW + payload of ~15K lbs) it can go 9685NM and with zero payload (OEW + max fuel), it can go 10056NM.

Again, interesting stuff and thank you again for your input and reminding me about the Piano-X reports. 

Best regards,
WesternU

Thanks for WesternU too. And happy new year to everyone. 
Inside AWS the 788 got it's fuel burn as 5 160 KG/H, I checked the range chart and found that the plane can fly to somewhere near Puerto Rico from Tokyo depands on configuration.. saying about 15 hours of flying time. Then the plane must at least got 77400 KG of fuel on board for cruise and we did't count any reserve fuel, which is the plane can carry much more fuel than 73364KG, the max fuel capacity of 763ER.

We can see right now the size of 788 is very close to 763 and the different between 763 and 788 is 787 family got very least metal on it's fuselage also aerodynamic and engines improved a lot on the new plane, so that I think the fuel burn number on Boeing 787-8 must be lowered than 767 for at least in the game.

[freshmore]

to be fair the 767 is out of production isn't it?! So the 787-8 would be our only choice normally. I'm expecting it to have similar fuel burn to the 767 but have much less than 332 or 333 of which it has close to a 1000kg per hour over them.

[EYguy]

I find quite difficult to compare B767 and A330 (200 or 300) and the B787... Mainly because the A330 is a much bigger a/c with more passenger in its usual service configuration. Anyway, according to what Boeing said, the 20% saving will be achieved only when the GEnx engine will be in service. Up to now, with only the Trent1000 engine in service, the expected saving would be of around 12% according to what I've heard...