On Jun 4, 12:03 pm, Bertie the Bunyip wrote:
Tina wrote :

On Jun 4, 11:23 am, Bertie the Bunyip wrote:
Tina wrote
innews:4cc0ec37-d80c-4006-9190-





m:

On Jun 4, 4:49 am, HARRY POTTER wrote:
Tina wrote:
I understand how positive dihedral helps dynamic stability in
airplanes, but some big ones, like the Russian An 124 Condor,
has a pronounced negative dihedral -- the wings have a
noticeable downward slope.

Q1: Do those airplanes need active fly by wire controls to
maintain stability, or is something else at play that keeps them
right side up?

Q2: Does anyone have a design rationalization for such a
configuration, as opposed to just zero dihedral? I can
appreciate why fighters have it -- they exploit lack of
aerodynamic stability for rapid maneuvers -- but transports
that spend their whole life being straight and level are another
issue.

Note: I have not morphed into an Mx clone!

The AN124 does not have negative dihedral. It just looks that way
when it's on the ground because the weight of the engines bends
the wings so they look drooped down. Once it's in the air, the
fuselage bends the wings the other way, so it actually does have
dihedral.

--http://onlinelogbook.net

Thanks -- didn't realize it was simply wing droop when they are not
developing lift. That's what happens when you fly in stiff winged
little airplanes, you start overlooking something as obvious as
that.

http://www.youtube.com/watch?v=WJscAaKfr7A

Bertie

OK, I see some of the downslope was washed out in flight, but it was
still obvious there. Thanks

I expect more is washed out when the airplane is at gross weight, but
your point is made, Bertie.

Um, washout is probably not the best term, being share with another
important wing feature, but yeah, it's still there even when the
airplane is very heavy. I've seen the 225 fly and it's the same. There'a
also the little BAe 146 and the C5 and the C141 and the other little bay
antonov etc. I also mentioned I had seen some striaght wing airplanes
with anhedral but couldn't remember where. Most of the turboprop
antonovs have anhedral, but not nearly as much as the jets. He obviously
liked his airplanes to be manueverable!
Even a lot of the low wing jets had anhedral. The IL 62, for
instance.and IIRC some of the Tupovlevs also had it.

There was a country music guy who had a Mitsubishi twin with what I
remember looked liked pronounced anhedral, but I did a web search and
couldn't find a photo of it. What I am remembering might have been in
the 1970s.

There's little doubt in my mind that a high wing configuration with
negative dihedral would be more stable than a low winged one -- the cg
being way under the center of lift would see to that -- but still
don't have a 'model' to explain why wing sweep is a factor: when I
have some time I'll think about that, or I suppose I could ask
Anthony.

As for new stuff in aviation? I'd say GPS, released to the general
public during the RR presidency because of the Koran jet shootdown in
Russia, is fairly new. And let us not forget the new and improved FAA.

I'm doing my part to add to the recreation in rec.aviation (and trying
to not have it be wreck.aviation).