Archaeopteryx paper in Naturwissenschaften online

[bh480@scn.org]

There's a new paper out about flight in Archaeopteryx in 
Naturwissenschaften, available online in advance of 
publication: 
Sankar Chatterjee &  R. Jack Templin, 2003. The flight of 
Archaeopteryx
Naturwissenschaften online
 Abstract The origin of avian flight is often equated with 
the phylogeny, ecology, and flying ability of the 
primitive Jurassic bird, Archaeopteryx. Debate persists 
about whether it was a terrestrial cursor or a tree 
dweller. Despite broad acceptance of its arboreal life 
style from anatomical, phylogenetic, and ecological 
evidence, a new version of the cursorial model was 
proposed recently asserting that a running Archaeopteryx 
could take off from the ground using thrust and sustain 
flight in the air. However, Archaeopteryx lacked both the 
powerful flight muscles and complex wing movements 
necessary for ground takeoff. Here we describe a flight 
simulation model, which suggests that for Archaeopteryx, 
takeoff from a perch would have been more efficient and 
cost-effective than from the ground. Archaeopteryx may 
have made short flights between trees, utilizing a novel 
method of phugoid gliding. 

Here's a highlight from the full text:

Phugoid gliding 
Archaeopteryx may have innovated a novel method of gliding 
between trees to save energy. Flying squirrels travel 
through a forest by climbing the trunks of trees and 
gliding between trunks (Norberg 1990). When crows take off 
from a tree, they do not seem to use excess power; they 
lose height at first and then swoop up to swing between 
two perches. This occurs whenever any winged object 
(aircraft, model glider, or flying animal) finds itself in 
a non-equilibrium situation, such as when launched without 
sufficient wing lift to balance weight (Feduccia 1993 ). 
The result is an initial loss of height at an increasing 
speed. Lift increases as speed squares (if controls are 
not moved) and the subsequent motion is an undulation, 
known as phugoid oscillation, with potential and kinetic 
energy being periodically exchanged (Templin; see Fig. E). 
In gliding flight, the motion is eventually damped to a 
steady glide and, in fact, the rate of damping is 
inversely proportional to the lift/drag (L/D) ratio. 
Objects with high L/D configuration, such as modern 
aircraft, have low phugoid damping, but because the period 
of motion is proportional to speed, control is not 
difficult. Archaeopteryx probably used a similar strategy 
to move from tree to tree, using phugoid gliding without 
expending much energy.