On Jun 4, 11:23 am, Bertie the Bunyip wrote:
Tina wrote :



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.