Re: Pterosaur wings

["James R. Cunningham" <jrccea@bellsouth.net>]

Chris Bennett wrote:
> Well, it could fly, but I am not sure it could fly.  By which I mean that it
> was demonstrated that it could glide and flap its wings at the same time,
> but I am not sure that it was demonstrated that it could maintain and gain
> altitude by flapping its wings.

It was known that it didn't.  Since then, Jim DeLaurier of the
University of Toronto, a team at the University of Florida, and I have
all independently done flapping kinematics calculations that both
confirm that and are in fairly close agreement with one another. The QN
replica had a very narrow window that would have allowed level flight
with little margin, but it was not flown within that window, and as a
practical matter, I'm not sure that it could have been. 

>  Everytime it flew it was towed up to a good
> height before release, and so it may have just been a sailplane that flapped
> its wings up and down a little.

Yes.  Actually, the plunge amplitude was adequate for the job, but the
wing did not have some of the other characteristics that would have
allowed the kinematics required to maintain level flight. Also, its
primary motors were a pair of Astroflight 60's, and they had enough
power to do the job, but could not accelerate fast enough to maintain
the appropriate beat frequency.  I wish they had used two pair of
twinned 40's for the primary instead, because the 40's accelerate faster
and can reach a greater rpm.  As an aside, there were additional smaller
Astroflight motors for wingsweep and suppination/pronation.  These
motions were all applied at the shoulder.  There were no provisions for
active mobility further out along the semi-span.  Though the original
design did allow for active modulation of the spanwise twist, it didn't
get implemented.  Paul has courteously provided me with much of the
internal documentation they generated while designing and building the
model, and it is impressive to say the least.  They did an extraordinary
job and should be proud of it.  It was quite a few years later before
any mid-sized ornithopters flew successfully, and insofar as I know, no
ornithopter the size of the QN replica (18 feet, 5.5 meters) has yet
successfully flown.  I think Jim DeLaurier's Big Bill (UTIAS) which has
a 13 meter span and carries a human pilot is getting close.  It has
actually lifted off at about 57 mph, but has not flown yet.  The first
liftoff resulted in a structural failure in one of the wing struts and
it did a half roll and landed inverted.  At the time, the pilot
(Patricia Jones-Bowman) was the only licensed ornithopter pilot in the
world.  I think there are now two.  Brave folks, both of them.

> 
> Interestingly, its untimely demise was not a result of the wing failure that
> Jim Cunningham worries about, but rather neck failure.  I happened to be in
> D.C. for its first and only public flight and was just getting ready to take
> its picture when the head felloff.  So somewhere I have a slide of the
> tumbling body slowly following the plummeting head.

Chris is correct.  The replica had severe problems with divergent yaw
instability which the head/neck mechanism attempted to minimize, and the
head/neck articulation failed.  The real animals had a similar problem
but handled it somewhat differently.

Jim