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Re: Quetzalcoatlus could not jump into the air

Rescued from truncation:


Great example.  And as an additional point, it's worth noting that relative
flapping amplitude tends to *decrease* with increasing animal size and
speed (the former is mostly a result of wing shape scaling with size).  So,
a bigger animal, launching faster, would need less flapping clearance than
a smaller animal launching slowly.  Thus, Chatterjee and Alexander have
compounded their own problem: citing clearance as a concern, they have then
given the animal less height (by forcing the feet to be in contact with the
ground during the launch) and making it launch slowly at a light mass.

And of course, there is the additional little issue that size and running
launch aren't correlated - unlike airplanes, a long taxi does not help
bigger animals take off.  Some birds do taxi to launch, but it's not a
matter of total mass.  In fact, of the two heaviest flying animals alive
today, one takes a very short run/hop to launch, and the other launches
almost vertically from a standing leap.  Most albatrosses, which C&A use as
one of the poster children for "big things run to launch" aren't even all
that big - about 2 kg or so in mass, compared with 15 kg or more for a Kori
Bustard (which is the one that hops or runs a short distance).  Even
California Condors, which are comparatively weak launchers, use leaping:
https://www.youtube.com/watch?v=Bmwr52divKI  [You'll note that the animal
uses the slope to help built speed *in flight*, after launching. Whether
or not this is required for them is unknown, but likely helps.  The launch,
however, is a simple leap off the ground].


--Mike H.

On Thu, Nov 8, 2012 at 2:58 PM, Jeff Hecht <jeff@jeffhecht.com> wrote:

Good point, This summer a pair  of swans raised seven cygnets nearby,
> and I watched the young ones take early flights over the water with
> fully-grown wings. Their bodies were barely a foot above the water,
> but their long wings stayed clearly above the surface as they flew.
> Obviously bird flight differs in detail, but the big water birds
> suggest the big pterosaurs could have gotten off the ground (or
> water).
> --Jeff Hecht