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Re: four winged Archaeopteryx




Graydon wrote:

> > As an aside, airplanes will also fly fine
> > if you remove the aileron from one wing, leaving it totally fixed, and just
> > use the aileron on the other wing.  Cuts the roll rate, but it still flies
> > fine.
>
> But you wouldn't try it with *none*, would you?

Most planes will fly OK and are landable with any one of the three primary 
control
axes out of commision (rudder, ailerons, stabilator).  It helps if the pitch 
trim
is still functioning, but it isn't usually mandatory.  That said, insurance 
isn't
valid if one deliberately flys with a non-functional control surface, so it
wouldn't be advisable to do so.

> I might quibble that a design that ended production in 1948 doesn't
> qualify as "modern".

The type is still in production.  Look at the Legend Cub for one of several
examples.

> It's also a design with a max speed under the landing speed of the
> stuff with the flaps and slats,

I think you're kidding again, but am not sure.  The one I fly tops out at about
108 mph, while General aviation aircraft are required to be capable of landing 
at
no more than 61 mph (if I remember correctly -- I may be wrong about that, but 
not
more than a few mph).

> which is more the point -- a relatively
> immobile wing works because the scope of the flight regime is
> relatively narrow.

108/38 is almost 3.  That is considered to be a fairly wide flight regime.  In a
dead calm, I can get the plane down and stopped in 200 feet if I try hard, 300
feet if I don't.  On a 98 degree day with no wind, I get off the ground in 190
feet.  That is considered good performance even by today's standards.

> But they couldn't have flown with a wing that was immobile as an
> aerodynamic surface,

I've flown scale models of pterosaurs with immobile surfaces.  There is nothing
about immoble surfaces that prohibits flight.

> couldn't have flown without the ability to alter
> the airflow over the wings,

See above.

> The talk I saw was about a proof-of-concept radio controlled model, that
> had a ~10 foot wingspan, in the early nineties, and I had to google to
> confirm the name, but yup, that's the fellow.

The 10 foot model was called Little Bill, so everybody started calling the big 
guy
Big Bill -- a name that JimD dislikes.  They both use a Scotch Yoke flapping
mechanism and shear flexing for wing twist.  There is no mechanism for creating
roll control in the wings. The only axes that are controllable, are pitch and 
yaw.

> .....looking at
> http://www.ornithopter.ca/Publications/AnOrnithopterWingDesign.pdf
> sugguests that this is a size constraint that wouldn't apply to
> bird-sized wings.

I'm not sure what you're saying in the sentence above.  I may have lost 
something
in the translation.....

> Less maintenance, given the recent stuff on preening/parasite
> suppression demands on bill evolution, isn't a small thing.

I never said that small developments aren't important -- I'm simply making the
point that they are not mandatory.

> Given a theoretical, hypothetical bird in still air with a fixed frond
> tail, what's going to alter the drag from the tail?

Flapping, turning motions, pitching motions, yawing motions, etc.

> > I don't buy into that statement at all, though I personally do think
> > Archie had the ability to manipulate its tail adequately for its
> > purposes.
>
> That's almost a tautology, isn't it?  Especially given a reasonably
> long species existence?

Of course it is.  I intended for it to be.

> That presumably has limits, though; passerines vary a lot in this
> respect, but losing all the tail feathers on one side can certainly
> keep them from flying.

And many birds can fly with the tailfeathers entirely removed. I suspect that if
you remove half the tailfeathers only, the bird will likely fly again once it 
gets
hungry enough.