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Re: pteros have lift-off

----- Original Message ----- From: "David Peters" <davidpeters@att.net>

Do your figures take into effect 'ground effect' flying?

Yes. That's why the numbers I quoted the other day specified 5' HAG. That together with the span and the Biot-Savart rule specify the ground effect drag reduction.

I mapped sequential photos of a pelican taking off (I can send this via a non DML email). Although the pelican is airborne immediately, the acceleration over a half dozen frames is easy to measure while flying in ground effect. Maybe, like pelicans and herons the availability of ground effect means pterosaurs don't have to reach cruise speed within a second after take-off?

Pelicans, herons, and pterosaurs don't have to reach cruise speed at any time, if they don't want to. That choice has nothing to do with the Biot-Savart law (ground effect drag relationship). I took the pterosaur to cruise speed during the terrestrial part of the launch simply because that gives the most extreme terrestrial loading.

Perhaps a trajectory in big pteros lower than 30º would be equivalent (i. e. ultimately ading to flying at cruise speed)?

As I have said over and over again, launch is at about 25 to 35 degrees. 25 degrees is lower than 30 degrees. 35 degrees is higher. The animals can adjust the launch angle at will, though larger animals do tend to go out at a lower angle. I suggest that birds of any species are not necessarily a particularly close analogy for terrestrial pterosaur launch since they do it so differently.

Looks like: 1) crouch simultaneous with wing unfolding and upbeat. 2) hindlimb extension simultaneous with first downbeat. No surprises. Probably common to most birds.

And mostly irrelevant to pterosaurs.

So, I'm gathering from the video that a large amount of thrust is generated by the wings along with thrust from the hind limbs. Which seemingly relieves the hindlimbs of a large amount of duty -- which was a major concern of yours.

Of who's ? Birds generate as much as roughly 90% of their launch power with the hindlimbs, depending upon species.

And this is incompatible with small and large pterosaurs because...?

It's not at all incompatible with pterosaurs -- it just has nothing much to do with them.