A340-600 Performance

[minibus3]

Hi all,

Wondering if anyone can answer a couple of queries I have, re the A340-600 performance?

Firstly, is there any truth in what I've heard, in that there are normally noticeable oscillations in the cruise?

Also, with regard to the efficiency, how does this compare with the B773ER?

Any answers appreciated.

Thanks guys,

minibus3

[Virginia Plane]

I've never noticed unusual oscillations in the cruise. Certainly used to get them on the 744!
Fuel burn is currently a little high (can be up to about 9 tonnes an hour) however I gather they are looking at increasing trim tank fuel to reduce this.

[jettison valve]

Virginia Plane,

Can you shed some more light on this (increase of tt fuel)...?

Cheers,
J.V.

[minibus3]

Yes I'd be interested in that aswell.

Also, is the A340-600HGW due top be on target with respect to efficiency?

And another - how is the efficiency on the A340-500?

Thanks again,
minibus3

[Fly3]

A345 Fuel Burn.

Average around 8000kg/hr.

[minibus3]

Thanks guys for the replies.

Just another one - does anyone have any idea of the fuel burn of the B777-3ER as reported by AF/JAL/ANA in ops.?

And does anyone know the projected B772LR fuel burn?

Thanks again guys,

Regards,

[N1 Vibes]

Hi minibus 3,

sorry for the late response. CX have noticed the oscillation. Reported by flt crew as 'hunting' to maintain a/c speed. We suspect that it is the FMGEC logic read over from the A340-300 that maintains engine speed to N1 (CFM56) whereas the A340-600 is EPR (Trent 500). Next time you or your pilots are flying ask them to look at the eng N1 speed on the A346 and they wil see that they line up, but the EPR's don't. Basically we suspect the a/c is asking the engine to maintain an N1 speed when it normally works to EPR. That's our take on it anyways.

As ever Der Bus are "looking into it"!

Brgd's

N1 Vibes

Ps Would be interested to hear what you find.

[minibus3]

Thanks very much for the info N1 Vibes, very interesting to hear that.

I'm not actually a pilot at the moment, but very much intend to fly. At the moment I'm studying for a degree in Aeronautical
Engineering in Bristol.

I assume these "oscillations" are doing very much for the fuel burn figs.!

Does the A340-500 have the same problem, bearing in mind they also use the Trent 500?

Thanks very much.

Regards

[scroggs]

We (virgin) have noticed power fluctuations in the cruise too, and N1 Vibes' suspicions are interesting. We have found that occasionally power adjustments can get out of synch with the speed trend and, in extreme examples, the crew may need to take the autothrottles out to smooth things down. It's not common, nor is it a major problem, but it does exist.

[aviate1138]

Question from a VFR strictly amateur pilot.

Aviate1138 asks.....

Do any of these big machines you professionals fly ever match the manufacturers figures? Just curious. In the small aircraft world the figures are very often highly optimistic but I guess the airlines have performance contracts or some safeguard.

Aviate 1138