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Re: vaulting pterosaur launch, questions
I think the physical requirements for a standing/leaping launch are
greater than a running launch.
Do you have any particular mechanical parameters in mind? I don't
think the physical requirements are actually greater.
While it may be easier for a bird with the neccesary adaptations, I
would think a standing launch would be a more derived form of
flight, and the basal launch technique would either be running into
the wind, down a slope, or dropping from a high perch.
Dropping from a perch (i.e. gravity assisted launch) seems plausible
as a basal launch strategy, assuming arboreal, gliding ancestry.
Running into the wind or down slopes strike me as much less likely, as
the specific requirements of terrain and conditions seem unlikely to
be met with enough regularity. And, if wind was truly required, then
leaping into the wind would be just as good as running into it.
But archeaoptyrx could sustain flight, the problem was getting
airborne and the trouble it would have flapping its wings on the
ground, right? a running start into a head wind could be sufficient
to get airborne to allow for weak flapping to do the rest.
It's ability to sustain flight is not certain, though it should have
been able to cruise for a bit. The problem is indeed largely with
launch, and that is likely best solved by leaping for an animal with
its build. The running start into the wind might do the trick, but
jumping into the wind would probably do even better.
True, but I think any animal that does a leaping takeoff from the
ground, is already adapted for flight, I have a hard time beleiving
it is the basal launch technique
Well, running launch is only present as a derived state in living
birds. Granted, the basal state in neornithines is already heavily
flight adapted, but I still don't see why leaping should not be the
basal launch technique. For an animal with long hindlimbs, like
Archaeopteryx, a leaping launch provides similar launch velocity, with
greater clearance for the wings, over less launch distance, in a
shorter period of time (as compared to a running launch).
I'm not talking shear here (30 knots consistent straight in is at
my limit, if not just above it), but smooth laminar flow over
elevated coastal terrain.
If you're not experiencing gusts or shear, then where are you
extracting your energy? I was under the impression that you were
referring to deflected air at ridge features, which would be a form of
Coastal lift is the most consistent lift I know of, and presents in
my view the lowest barrier to controlled flight. This doesn't mean
thats how it happened, but I wouldn't be surprized if controlled
flight arose from pterosaurs or therepods living near the beach, or
Not a bad thought.
Of course birds do that as well, and it isn't a requirement.
However, as with the Wright brothers, you can't very well have
powered flight until you can have controlled flight.
The transition form has to be viable, and I think a coastal soaring
unpowered flight form is viable.
At least more viable than something clumsily flapping to extend its
glide between trees.
I don't entirely disagree, but for sake of argument I do note that
extended, controlled marine soaring among modern birds is actually a
fairly derived and control-intensive exercise.
Among human foot launched flight, a lot of the time all you need to
do is walk to the edge of a coastal dune with a neutral/negative
angle of attack, and then increase angle of attack at the edge, and
away you go- no leaping or running required at all. It should get
even easier as it is scaled down.
A an early bird or pterosaur need not neccesarily run or leap at at
all, just waddle up to the edge and unfold its wings
Indeed; a gust over a ridge is a powerful source of energy. I doubt
that pterosaurs launched bipedally (see earlier posts in the thread)
so I rather imagine that pterosaurs didn't waddle up to cliffs and
unfold the wings in quite that manner, but a bipedal or quad leap off
a ridge into a strong gust would be a decent way to get airborne,
presuming that the aforementioned incipient flight was not intended as
a method of escape (since reliance on ridges for your getaway is
unlikely to be sustainable).
Michael Habib, M.S.
Center for Functional Anatomy and Evolution
Johns Hopkins School of Medicine
1830 E. Monument Street
Baltimore, MD 21205