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RE: 4 winged dino NOVA




Jim Cunningham wrote:

> Also, folks seem to overlook the substantial contribution of a set of fixed 
> trailing airfoils to increasing the thrust coefficient of the flapping wings 
> in front of them.  The hindlimbs may have developed to enhance flapping 
> flight rather than gliding flight.  For that purpose, there is no particular 
> requirement for a splayed horizontal positioning of the posterior airfoils.


How does this accord with Chatterjee and Templin's biplane model of phugoid 
gliding?  Does the same principal hold for your flapping-flight scenario?


Chatterjee, S. & Templin, R. J. (2007). Biplane wing planform and flight 
performance of the feathered dinosaur _Microraptor gui_.  PNAS 104: 1576–1580.


Abstract: "Microraptor gui, a four-winged dromaeosaur from the Early Cretaceous
of China, provides strong evidence for an arboreal-gliding
origin of avian flight. It possessed asymmetric flight feathers not
only on the manus but also on the pes. A previously published
reconstruction shows that the hindwing of Microraptor supported
by a laterally extended leg would have formed a second pair of
wings in tetrapteryx fashion. However, this wing design conflicts
with known theropod limb joints that entail a parasagittal posture
of the hindlimb. Here, we offer an alternative planform of the
hindwing of Microraptor that is concordant with its feather orientation
for producing lift and normal theropod hindlimb posture.
In this reconstruction, the wings of Microraptor could have resembled
a staggered biplane configuration during flight, where the
forewing formed the dorsal wing and the metatarsal wing formed
the ventral one. The contour feathers on the tibia were positioned
posteriorly, oriented in a vertical plane for streamlining that would
reduce the drag considerably. Leg feathers are present in many
fossil dromaeosaurs, early birds, and living raptors, and they play
an important role in flight during catching and carrying prey. A
computer simulation of the flight performance of Microraptor
suggests that its biplane wings were adapted for undulatory
‘‘phugoid’’ gliding between trees, where the horizontal feathered
tail offered additional lift and stability and controlled pitch. Like
the Wright 1903 Flyer, Microraptor, a gliding relative of early birds,
took to the air with two sets of wings."


Cheers

Tim
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