Re: Are Two Engine 757 & 767 Jets Dangerous?

Date:         08 Dec 96 04:12:35 
From:         mikeh@zeta.org.au (Michael Hore)
Organization: Kralizec Dialup Unix Sydney, +61-2-837-1183 V.32bis
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Stefano Pagiola <spagiola@worldbank.org> writes:

>H Andrew Chuang wrote:
>> >BTW why did Airbus design a new *four* engine plane A340 and, not like
>> >the 777 a twin-engine A340 ?
>>
>> ... The fact that Airbus needed to put four engines on the A330
>> and called it the A340 was because there was no suitable engines
>> available at the time.  If the B777-class engines were available at
>> the time the A330/A340 was launched, I doubt the A340 would have existed.
>...
>
>First, should the 4-engine A340 have been built at all? ie, are you
>correct in supposing that it would not have been had 777-class engines
>been available at the time?  If one judges by the continuing demand for
>the A340 even now that the 777 is available, including by airlines that
>have 777s on order (eg Cathay), it would seem that not all agree with you.

So far nobody seems to have mentioned the most important reason why the
A340 has 4 engines - let me quote from _Flight International_, 5-11 June,
1991, p28:

"With a pair of high-thrust turbofans, the wing could support a maximum
take-off weight of 212t, giving the A330 its 8,800km range with 335
passengers.  With two further engines located outboard, giving extra
bending relief, the wing could support more fuselage weight without
stressing the wing/fuselage join more than that of the A330.  This
meant that an extra 41,700 litres of fuel could be carried in the fuselage
centre-section, giving the A340 the extra range it needed."

So it appears to me that the A340 would always have had 4 engines, regardless
of what engines might have been available.  It's part of Airbus' philosophy
of meeting 2 markets (medium range / long thin) with 2 designs optimized
for each.  Thus I understand they claim that the 777 is less efficient
than the A330 in the medium-range role, since the former has to carry the
structural/landing gear/etc. weight for a long-range capability.  I'm
sure Boeing will dispute this...

Cheers,  Mike.

-----------------------------------------------------------
Mike Hore          mikeh@zeta.org.au
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