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Re: BCF related -Reply



LESLIE F NOE wrote:
> 
> Hi!
> 
> All this talk of aerofoils and aerodynamics of modern aircraft seems a
> little off the mark to me.

Perhaps.  I just see it as a way to illustrate specific points about
bird and pterosaur flight and flight control using a visual image
familiar to all.  The discussion of camberlines and chord load
distributions and such is certainly pertinent to the analysis of bird
and pterosaur flight, and I wake up in the night thinking about it as a
part of my ongoing study of Quetzalcoatlus.  I'm glad that Patrick,
George, and Matt are interested in it.  I think we are actually carrying
on most of our discussion off-list, and posting only that which might be
of some interest to others.  I know this thread has brought out some
points I'm going to be sure to pass along to my students in my fluid
mechanics class this coming year.

> However, the point is birds fly in a totally different way to
> aeroplanes -

Not really.  Airplanes use a subset of the mechanisms available to
birds. In general, birds make far more use of unsteady effects, and
small birds can more than double their lift by doing so, but large birds
and large pterosaurs occupy an envelope very similar to small aircraft,
and many of the flight mechanisms and computational procedures are
identical.  Propeller momentum theory can be directly used in
calculations pertaining to bird launch.  Also, modern aircraft design is
making more use of unsteady mechanisms modeled after biological flight. 
I think there is a valid cross-over in discussion of the physics
involved, though I don't think this is the place for extended
discussions of aircraft flight.

> they have a level of control over their flight surfaces a
> pilot can only dream of (as indeed I suspect do the gliders in the
> animal kingdom).

Speaking as a pilot -- You got that right!!!

> Just watching a bird in flight, even when gliding, it
> uses incredible precision movements of its wings, changing their
> position in three dimensions in space, adjusting the surface area,
> angle of attack etc. etc.

Well said, and a good part of why we all think they are so lovely.

> All of these ideas can then be tested against the fossil  record (poor
> as it is at the moment, but getting better all the time), and more
> importantly should be thought of in terms of falsification - what
> evidence will I accept as DISPROVING this idea (and not then shifting
> ground to accomodate the new data should it come in!).

I think this is the key to all science.  Form a hypothesis and then look
HARD for evidence to disprove it and modify it to incorporate such
evidence.  Or toss it and formulate another hypothesis.
                                Jim