Re: Singapore Airlines The A340 vs 777 saga continues

Date:         07 Aug 99 01:22:38 
From:         "Tim Lee" <>
Organization: BT Internet
References:   1 2 3
Followups:    1
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Matt727 wrote in message ...
>Tim Lee wrote in message ...
>>Hang on a minute, James!
>>Frankly, 6.5 tons is not a huge amount - not at this stage of
>>development, anyway.........
>Not a huge amount?  If you say so....

Not particularly, no. Have a look at the weight of seat back video systems
(Virgin are even looking at gyms, for god's sake!), and this puts a slightly
heavy airframe in perspective.  In any case, have a look at Airbus' press
release on this subject.

>>>The run to Europe from Singapore in an A340 is nearly an hour longer
>>>than it is in a 747, or a 777.  It is extra travel time, and it
>>>complicates connections within Europe.
>>The 747 is a quick aircraft, but I doubt this is true for the 777, which
>>has a stated cruise of 30kts less than A340.
>747    Mach .85
>777    Mach .84
>A340 Mach .82, but it has to go slower for the long range.

Since I wrote this, I checked up.  Compare the BA flight time LHR-LAX by 744
with the VS time on the same route (340).

>>Prove this one, please!  AI aircraft have a similar climb rate to the
>>777, and the 747 climb performance can be dismal...  Also, no-one can
>>convince me that any aircraft in commercial use can climb over a cu-nim
>>cloud - they can peak at over 60,000ft.....
>It has nothing to do with how fast it can climb... it is about wing loading.
>As you go higher the air gets thinner.  So if you are at MTOW in a A340 you
>cant climb way up high because the thin air wont support the aircraft.  Now,
>if you have a big Boeing wing you can go right on up.  That is how it works.
>Wing loading and air density at altitude.

I still refer to the original mailing - the original comment implied that
the Airbus would have to either fly around a cu-nim, or not fly, because it
couldn't climb over the top.  I repeat that since cu-nims top out at 60k +,
nothing on the civil market could overfly it, so rate of climb is academic
in this case.  I think you'll find in any case that most aircraft finish the
cruise at a higher altitude than they started it for the reason you quote,
Boeing included.

>>AI products do this without problem - VS toc is typically 39,000 on the
>>HKG-LHR with a 340.
>Sure, maybe at a LOW aircraft weight.

So how heavy is a 744 after the run from HKG to LHR?

>The A340 has the same wingspan as the 777, but the mean chord is way less
>therefore creating a wing with less area.  (I hope no one at Airbus reads
>this... then they would know how to make a good airplane!  (a bigger wing
>also adds fuel capacity!)

But the AI wing has a higher aerodynamic efficiency (l/d ratio).  The Boeing
wing is hardly SOTA - it was orginally put together for 707, and has changed
little, except in size, since.

>>Do we work for Boeing by any chance?
>........and where do you work?

I work in consultancy - not with AI.  By profession, I am a Chartered
Engineer, and a member of the Royal Aeronautical Society.