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Re: More on Argentavis
If this research was done in the same manner as Chatterjee's pterosaur
work (which is what it sounds like), then they are applying helicopter
momentum theory as the framework for flight ability estimates. It is
essentially a particular model for estimating how momentum is imparted
to the air for a flyer of a given size and wing shape. It can get
rather complex, but the previous applications of the technique to
pterosaurs were pretty simplistic, to the best of my recollection.
Unfortunately, Chatterjee's estimates and assumptions regarding
pterosaur launch and cruising ability had a number of problems,
including some estimates of body mass that are probably impossible
(like 70 kg for Quetzalcoatlus northropi).
I'll have to look at that actual paper before I form any opinions or
critiques. Chatterjee has done a lot of good work, but I rather doubt
the accuracy of some of his conclusions regarding pterosaurs (including
body weights, relative muscle composition, and launch kinematic). This
work may have fewer errors, but from the review article I am concerned
that the launch model may be inappropriate. Specifically, launching
for birds with low wing loadings is as much a leaping problem as a
flapping one (especially for the early launch phase). The hind limb
mechanics are critical in avian launch, and I noticed a lack of mention
of any hind limb analysis in the review. That might just be an
oversight of the Nat. Geo writer, though, so I don't want to jump to
I'll grab the full paper tonight, and perhaps toss out some thoughts
soon. I'd be quite interested to hear what others here think of the
paper and the methods.
On Tuesday, July 3, 2007, at 03:14 PM, Mark Hallett wrote:
Guy, Interesting news. I'm curious as to how the
researchers determined that A. couldn't, or would have
had trouble flying-- perhaps I'm remembering this
incorrectly or incompletely, but wasn't there an
aeronautics engineer who stated many years ago that
according to the laws of flight dynamics, a bumblebee
should in theory be incapable of flight? --Mark
--- Guy Leahy <firstname.lastname@example.org> wrote:
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