Re: 2 vs 4 engines: R&D costs too much ?

Date:         16 Sep 99 16:42:57 
From:         "Geoff Jones" <geoff@burnell.demon.co.uk>
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JF Mezei wrote in message ...
>A recent post mentioned the R&D mega expenditures required to produce
>the engine for the next 777 which is a big reason only one manufacturer
>will build one.

The big reason for this, as far as I understand, is purely political.
The big three manufacturers had all developed engines which were
suitable, but for some reason, Boeing decided to sign an exclusive
agreement with the manufacturer of the worst and most expensive of the
three.

>Are we not getting to a point where conventional jet engines are
>reaching the top of the bell curve and any improvements will cost more
>and more ?

In respect of going towards twin engined craft, there are a few
considerations.  Not the least of these is sheer size. As bypass ratios
become higher, the ground clearance for the engines reduces.

Thinking about development costs, using two engines rather than four
immediately means that you halve your sales, pushing up the unit R&D
costs.  Then, it is also the case that R&D expenditure is rising for
each engine design, as higher efficiencies, lower emissions and higher
thrusts are desired.

>On the other hand, by using 4 engines (or even 3), it allows you to use
>much more conventional technology which is not only cheaper  for R&D but
>has greater market and hence more competition.

If you want the same emissions and efficiency, the development costs are
still high. Using more engines means that each aircraft has to have
(roughly) double the number of expensive components such as turbine
blades. The cost of these is quite largely in the materials and the
manufacturing, so a small reduction in development costs will far from
offset this.

Geoff Jones