A380 fuel efficiency

[atakacs]

I realize that actual numbers are supposedly one of the best kept secret of the industry (although I'm not convinced that it can really be kept that secret) but browsing through Wikipedia I'm rather surprised to see the A380 and the 747-400 in the same ballpark. I would have thought that 30 years of engineering would produce some gain here...

Without going too much into specifics are those numbers to be considered seriously ?

[DaveReidUK]

Without going too much into specifics are those numbers to be considered seriously ?

It's likely that different assumptions have gone into various figures quoted, particularly given that they don't all come from the same source.

The general consensus is that the 747-8i burns about 16% less fuel per seat-mile than the 747-400 and about 6% less than the A380.

So the A380 works out about 11% lower than the 747-400.

[atakacs]

The general consensus is that the 747-8i burns about 16% less fuel per seat-mile than the 747-400 and about 6% less than the A380.

Thanks - that sounds more "reasonable".
How would the 777 (current - not X) fit in there ?

[Tipsy Barossa]

I don't know about A380 fuel efficiency, but as an occasional plane spooter I am quite queasy about A380 takeoff climb performance! I have watched full long haul A380 flights consistently achieving about half to two thirds of the heights above a point about 1000ft beyond the DER attained by similarly full long haul B744 and B77W flights. Consistently!

Are A380 operators using derated takeoff thrust with more than 25% reduction from max rated thrust? Or are A380 using a different second/third segment profile?

The B77W seems to have the most impressive takeoff climb profile. Note I have checked the loads, flight lengths, etc. They must departed very close to the MTOWs for those flights.

Just wondering.......

[TopBunk]

The B77W seems to have the most impressive takeoff climb profile.

... which is just as you would expect as the B77W has to be able to climb with 50% of its power lost, whereas the A380 and B747 with 'just' a 25% power loss. The B77W therefore has greater excess power when all engines are operating.

[dixi188]

The A340-300 at max weight seems to get airborne due to the curvature of the earth. I think they had a special SID at Heathrow.

[Radix]

............

[striker26]

Not sure how you guys feel about this but consider the current situation: Airlines are in a dog eat dog world with each other with regards to landing slots and gates at almost every intl airport. I think the a380 will still be around in the future, especially if they come out with a NEO...

We don't have solid numbers to compare with but i can say that its not worth comparing the 747 with the a380, 2 different airplanes introduced in 2 different generations of air travel. Only time will tell, im sure we'll see more a380 orders in the future...

[Cough]

Right I'm not on this aircraft so only hearsay...

Max flex (talking reduced thrust takeoff here!) used to be 25% of max thrust, but this has been thrown out of the window for the A380 which can takeoff with even less thrust still - As I understand it 744's from LHR are usually somewhere around max flex so effectively overpowered. So the aircraft constantly flex's for a balanced field takeoff. Bear in mind that as a 4 engine jet, performance only has to cater for the loss of 25% thrust so a quad is always going to climb slower than a twin on all engines.

But here is the safety net. When they need to, crews can just push the thrust levers to the front stop... Then its going to climb quite well!

Ed to add - I'm sure airports are going to have to consider making airlines have more than 1 landing slot - Say 3 movement slots for a takeoff and landing at a given slot limited airport. Reason - Massive time loss for every A380 sep/arr due to wake turbulence.

[FullWings]

A couple of months ago I did a 11hr+ flight in a 777-300 using the same destination and route as an A380, within an hour of each other. Comparing the fuel plans, we had a payload of 48T and 112T fuel and the A380 55T and 172T. On that basis, the 380 burnt c.50T more fuel to carry another 7T...

I think the A380 makes sense when you can fill it up with passengers but with an empty weight around the 280T mark, that’s a lot to drag around the sky if there are empty seats.

[golfyankeesierra]

It matters what the yield is of the payload. Passengers (especially the Businessclass) yield more then freight.
And the A380 carries more pax and the 773 more freight. Depends on what you need.
I was told at the bar that anywhere BA sends an A380 it needs to send a 777 as well for the freight?

[Hotel Mode]

Those stats only work if 1kg of freight earns the airline the same as 1kg of passenger which it clearly doesn't.

That 20t of freight you carried is worth about £20k to BA. The 176 extra passengers the 380 carried will be paying a tiny bit more than that. The 44 extra club seats alone would be conservatively worth £160k. The 380 still carried some cargo too!

It's a niche for sure, but a very profitable one on the right routes.

[striker26]

Hotel Mode - fully agree with you. The main point in your comment is "right route". A full a380 is definitely worth it. What's sad though is that (ignoring Emirates) an airline could easily do with a couple of a380's, if any, because most airlines see the empty seats as a loss and dont require so many on different routes.

For Airbus, i think it was a historic plane that certainly changed aviation, but from a business perspective hasn't made much sense so far.... Still hope they keep it going though.

[Cough]

I doubt 44 club would be conservatively worth 160k... I have just looked up HKG in sep on the 380 and it gives £1700/seat each way. Take off £182 in taxes gives £1500 * 44 = 66k and thats when you fill it!

[Capt. Inop]

The A340-300 at max weight seems to get airborne due to the curvature of the earth

That would be the -200.

[Meikleour]

.....or a -300 with B2 engines. That was the combo that started all these Airbus rumours.

[Ex Cargo Clown]

That 20t of freight you carried is worth about £20k to BA. The 176 extra passengers the 380 carried will be paying a tiny bit more than that. The 44 extra club seats alone would be conservatively worth £160k. The 380 still carried some cargo too!

Don't know where you got those figures from, but I know on some routes the cargo yield is a hell of a lot more than that.

[nonsense]

Originally Posted by dixi188

The A340-300 at max weight seems to get airborne due to the curvature of the earth.

Or not, should the curvature turn out to be insufficient:

"... the aircraft eventually left the ground, but, by 170 m (558 ft) beyond the end of the runway, it was able to achieve an altitude of only 70 cm (2 ft) above the ground. Subsequently, it took out a 200 m (656 ft) stretch of strobe lights at the end of the runway and continued to climb with difficulties. At 350 m (1,148 ft) beyond the end of the runway, the landing gear hit and damaged the 180 cm (6 ft) high localiser antenna array operated by Airservices Australia. At 500 m (1,640 ft) beyond the end of the runway, the aircraft barely missed the 2.24 m (7 ft) tall airport perimeter fence. It was also reported that after clearing the airport perimeter, the aircraft cleared a small brick building by only 50 centimetres (20 in)."

OK, it was a 340-500, but why let that get in the way of a good example of insufficiently curved earth?

[DaveReidUK]

OK, it was a 340-500, but why let that get in the way of a good example of insufficiently curved earth?

I would guess that most transport aircraft would suffer in the same way if T/O thrust was set based on 100 tonnes less than the actual AUW ...

[atakacs]

Actually they eventually selected TOGA thrust so those numbers are apparently the max climb performance at the time if I understand the incident report correctly. Admittedly they started the takeoff with way too little thrust due to the 100t error...