Re: four winged Archaeopteryx

["Jaime A. Headden" <qilongia@yahoo.com>]

Graydon (oak@uniserve.com) wrote:

<Really immobile fixed wings for aircraft didn't work; it was only when
somebody figured out (at a minimum) wing warping and (much better) ailerons
than powered flight was a success, and that had to be accompanied by the
ability to design aircraft as a whole for flight stability.>

  It is possible to construct a glider that functions pretty well without wing
warping, camber, or even ailerons. Certainly a good deal paper airplanes can
fly decently this way.

<What I should probably have said was something like "expecting a immobile tail
surface to work for bird flight is a very strong claim"; a fixed frond tail
would have uniform drag and be a uniform contribution to flight stability.>

  Yet what I brought up in my post had a lot to do with exapting feather form
from a running animal, not a flying or even gliding one, which would only need
the feathers to form a planform on which to extert control of windflow. Sifakas
do this without feathers, or even the ability to MOVE the membrane or their
integument, just their arms themselves.

  The claim that an immobile feather is useless in a wingform would even be
true, save for the issue that the feather itself is only one piece in a series,
and that the wing itself is mobile with a controllable slat at the front
(alula) that the first digit (thumb) could have approximated (and indeed,
*Microraptor* has such a structure on its first manual digit). Very, very few
birds (if any) have the ability to independantly move their wing feathers (they
are bound at the base in spaced areas that, if messed with, would make it
difficult to fold the wing during flexion of the arm and thus the flight
stroke) and the tail feathers are controlled by muscles, not ligaments, in the
tail stock.

<So you either have an Archie that can't fly with lost feathers/feather damage
to the tail, maybe can't turn without heroic effort, and is in serious trouble
with gusty winds (or anything else which applies an assymetric airflow to the
tail), or you've got an Archie with some ability to adjust the tail surface to
cope with conditions.>

  Many birds can fly while moulting or with predator/prey damage to their wings
and tails. Just the other day, I saw three gulls with only half their flight
feathers present flying pretty well. Mark, however, that the missing feathers
were closer to the body wall than the wingtips, which were more or less intact.
Not so the tail, which was ragged and irregular. A bird can fly without tail
feathers, though, and there are a great number of volant birds which have the
tiniest remiges, from dippers to some sparrows/finches. For maneuvering, tail
feathers are king, but Archie, as a ur-vogel, did not particularly require such
aerodynamic mastery, and even *Confuciusornis*, like dippers, sports only the
tiniest tial feathers save for the "males" with their veyr long vexillae-like
remiges.

  Cheers,

Jaime A. Headden
http://bitestuff.blogspot.com/

"Innocent, unbiased observation is a myth." --- P.B. Medawar (1969)

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