Re: New refs

["James R. Cunningham" <jrccea@bellsouth.net>]

bh480@scn.org wrote:

> Primitive wing aspect
> ratio morphotypes were elliptical ones,

Interesting.  For an uncranked wing, that's the most efficient shape.
Of course, bird wings are cranked, but elliptical is still a good
starting point.

> Aerodynamic theory provides ecologists with a
> useful tool for understanding the basic physics of flight,
> but analysing flapping flight aerodynamics in birds is
> difficult,

Why?

> For take off from the ground, proavis would have needed to
> reach a sufficiently high forward speed on the runway
> [which is given by the minimum power speed of the power
> curve (Box 1)].

Now, this ain't necessarily so.  May have been, but there is more than
one way to skin the cat.

> The main problem is that the estimated
> top running speed of Archaeopteryx is 2 ms-1, whereas the
> speed required for take off is at least 6 ms-1,

Is it?  Were there no wind gusts when these animals were evolving?
Might they have been smart enough to takeoff into a headwind like people
do?  That speed also makes some implicit assumptions about flapping
kinematics and tail lift that I'd want to see more detail on.  Also,
what CLmax does it presume, and does it allow for non-steady lift?

> thus
> making it impossible for Archaeopteryx to have been able
> to take off from the ground [18].

I wouldn't want to bet on that side of that argument.

> The wings also generate lift force, but,
> during running, this is residual lift, because it does not
> act on the bird,

Hunh, what was that again?

> there is a `horizontal force
> migration' from hind limb propulsion to increasing wing
> thrust during the taxiing run (Fig. 2).

I'm sure they did 'taxi' (otherwise called walking about).  Do you think
these guys may have meant 'takeoff run' rather than 'taxiing run'?  If
so, did they really need to run to takeoff?  Assuming they weren't
arboreal of course.

> , this aerodynamic model shows that Archaeopteryx could have used
> powered flight and was probably quite an advanced flyer.

Though I don't agree with how they got there, I do agree with the part
about powered flight and advanced flyer.

> One can also envisage that feathered and winged dinosaurs
> [21] could have likewise increased their running speed by
> using wing thrust,

I'd tend to bet that that's not the case.

> and that bird flight therefore evolved from the ground up.

Could it have been a mixed bag, with birds getting better at several
options at about the same time, as their mechanical ability improved?