Re: Trailing edge wedge?

Date:         29 Apr 99 22:10:36 
From:         James Matthew Weber <jmweber@goodnet.com>
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At 02:22 AM 4/19/99 +0000, you wrote:
>
>lou@cadence.com wrote:
>> IIt seems surprising there are still relatively easy 7% improvements laying
>> around.
>
>I have a running argument with a former boss of mine.  Now, neither of
>us are professional aerodynamicists, he is an EE, I a physicist, and we
>specialize in avionics. So I suppose both of our opinions are worth as
>much as we are paid for them  :-)  But we both study aero avocationally.
>
>Anyway, he contends that almost all that can ever be known about airfoil
>and wing design performance is already known, and that only the
>onesy-twosey percent improvements can be hoped for now.  I maintain we
>still, in this day and age of numerical models and supercomputers still
>do not completely understand how to make air do exactly what we want it
>todo.  There may be revolutionary designs that could give big jumps in
>performance yet to be discovered.

I think the failure to produce any product at this point that is
dramatically better than any other product, and the extreme difficulty Airbus
is having in producing A3XXX with a 15% direct operating cost improvement
over the 747-400 is almost prima facia evidence of
the truth in the above statements.

If you look at the current generation of 747 engines, RB211-524G/H, PW4056
and CF6-80C2, there isn't much difference among them in price, thrust,
weight or fuel consumption.

I'd be reluctant to say that it is ALL known, but I think events of the
last decade suggest that within the current materials and
regulatory envirornment, there is not a lot of room left for improvements.

While there have been some fairly dramatic improvements, like the GE90,
they were achieved by making trade offs that are relatively well known and
well understood (The GE90 weighs about 1500kg more than  the big Trent ).

I suppose the corollary to that is that most of the designs are produced
using computer assisted designs, and the underlying codes
are probably surprisingly similiar. This tends to limit creativity
considerably. It means no really bad designs get out the door, but probably
no inductive leaps forward either.....
James Matthew Weber  1 602 315 6520   Fax 1 602 638 1316