damn, that's the best thread in terms of detailed answers to questions... why can't any thread be as informative as this one??

keep goin' guys, that's how pprune has to be!

Correct,

That is why the 748i is more efficient than the 777-300ER, and maybe why Boeing has not sold a 777 this year. The GEnx/Trent 1000 family on the new aircraft either on a twin or a quad are far more efficient than the equivalent current models.

The 787-10 is better than the 777-200, 747-800 better than the 777-300ER, nothing to do with the number of engines, just the type.

A friend of mine who is working for an airline who operates both types of the same series, 330 and 340, gave me a few very interesting figures:

If that airline has to send a 340 instead of a 330 on a route that is not ideally suited to that 4 engines, let's say a 6 or 7 hours flight, on an identical typical payload, the 340 will use about 15% more fuel !

To partially explain that extra fuel burn, the 340 suffers from an extra 8% on the OEW.

It might be somewhat off-topic, but anyway, this is my question:

What are/used to be the reasons for the practice of shutting down one or two engines right after vacating the runway on 2 or 4 engine aircraft respectively? Is there any fuel benefit in doing so, or the only reason is to enhance engine life? I think that this practice is not that common anymore, why is that?

Thanks,
OK

You should check out http://www.pprune.org/forums/showthread.php?t=219191

admiral ackbar: merci:ok:

Upon re-reading many of the well thought out inputs here, I have to agree that comparison between aircraft such as the B777 and B747 is unfair, the B747 does not have the advantage of the much later refined super-critical wing of the B777, and has good, but older technology engines. The only fair comparison would be to build a 2 engined B747 with comparable technology engines, or alternatively to build a 4 engined version of the B777 with comparable technology engines.

Fortunately for this argument, Airbus has done just that for us in building the very similar technology A330 and A340, and CONF iture's post has well illustrated the fuel efficiency differences between the essentially similar 2 engined A330 and 4 engined A340.

It all gets down to excess thrust allowing for much improved climb, and the ability to cruise at higher levels at all phases of flight at similar weights.

Regards,

Old Smokey

A Fair comparison. I am asking a Fare comparisson .

The 777 was marketed as a replacement for airlines flying clapped out old 747 classics.
I for one could not see the comparison between the 2 when the 777-200 emerged as it was a (3 class config) 300 seater but the 777-300 is a 350 seat (3 class config) with more cubic cargo space than a 747.

Lets assume the aircraft will be based at the ass end of the earth (to quote a former prime minister) and many of your airlines cash earning routes are 6 - 8.5 hour flights to asia which would be well suited to the 777.

These routes for years have been serviced by 747 classic and 747-400 due to the fact that no new/efficient type aircraft were purchased in the 90s.

I am asking difference in fuel burn from a 777 to 747 as a 747 classic burns over 100K fuel to Japan and a 744 around 90K.

It would appear but I can not confirm that a 777-300 full pax and cargo over these distances would burn about 30K kgs less fuel

The Fair comparison is about commercial reality with the price of fuel souring thru the $70 US and more.

Can anyone help with these figures?

Bolty

All the data I have goes in favor of the 777 vs the 744 in terms of FF compared with weight.

Fuel planning data (x1000 lbs);
777 landing weight 400 lbs
744 landing weight 500 lbs

...............777......744
4000 nm....118....174
3000 nm......87....127

Also BADA data and long range cruise tables show a similar picture.

How this compares pr SEAT however, I have no clue...:O

Cheers,

M

Yes, that's a fair comparison. Someone has a comparison between a 330 and a 777?

One has to understand that Airbus designed its A340 before Boeing began boosting its Etops limitations. Before that, lots of flights were economically not useful with a twin. That's why Airbus should have started selling the A330 as the standard long haul type, whith an A330-500 and even -600.

Dani

Drifting off-topic, but I used to have a series of graphs that plotted fuel burn against sector distance for several aircraft types. Obviously the figure was very high for ultra-short hauls, and descended steeply thereafter before levelling out and … starting very gradually to rise again (burning fuel in order to … carry fuel).

The consequence was that, for any given type, the optimum stage length in terms of fuel burn was significantly shorter than the capability of the aircraft. For a typical longhaul widebody this might be about 5500km (say, London-Dubai).

So two 5500km sectors (4x taxi, 2x takeoff, climb, landing…) would burn less fuel IN TOTAL than one 11000km (say, London-Singapore).

Seems counter-intuitive, but a tech stop very close to the Great Circle could be a fuel-saving measure.

All

have we overlooked the fact that with a 2 engined aircraft you only have to overhaul 2 engines at say $3-4 million a piece on a 777, when on the A340 you have to shop visit 4 engines at say $2-3 million. B777 = $7 million, A340 $10 million. Approximate figures used, terms and conditions may apply, the value of your A340 may go up as well as down!

And, with the CFM haridryer's having just enough thrust and EGT margin to pull the skin off a rice pudding you will be shop-visiting more often than say it's bulletproof GE90 big-brother.

So perhaps the comments were leaning more towards the bean counters who love twin engined a/c because of the above. My current operator, spend 1/3 of the engineering budget on the noise generators.

Thoughts?

N1 Vibes :8

Which they could not quite have done... Airbus started with shorthaul widebody twin (A300) and continued with a somewhat longer haul twin (A310). ETOPS was very much pioneered by Airbus... but they felt that it still limited their routes and range, which is why A340 was designed.

Problem: A330 seemed to be hard to stretch. I think that the standard MTOW for A330 is 230 tons (both -200 and -300) and the MTOW for A340-200/300 is 275 tons.

I have heard rumours that it may be the landing gear/engine clearance of A330/A340 - could it be the case? That A340 could have enlarged wing and stretched body for the -500/600 version while 330 would run out of the available underwing space for expanding the two (big to begin with) engines?

A350 quotes MTOW of 245 tons to begin with. Can they expand it?

B777 has been successfully expanded to 350 tons -200LR and -300ER - with a new wing. But the old wing -200ER and -300 have appreciably lower MTOW... How does B777-200 (non-ER) OEW and fuel burn compare with A330?

According to BADA, the A333 has far better cruise FF than the B772 for
the same weight. The B772 has however much bigger MTOW and range.
I guess it would be more fair to compare the B772 with the A343.

Compare the below with the A333 and A343 tables on the end of the previous page.

Cheers,
M
http://www.xplanefreeware.net/morten/DOCS/772.jpg