negative dihedral

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!

In article ,
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!

Don't know why, but don't those transports with negative dihedral also have
wings above the hull? So those aircraft have the CG below the wings.

--
Bob Noel
(goodness, please trim replies!!!)

Bob Noel wrote:
In article ,
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!

Don't know why, but don't those transports with negative dihedral also have
wings above the hull? So those aircraft have the CG below the wings.



And large transport aircraft are amongst the most aerodynamically stable
aircraft to fly.

Frank Olson wrote in
news:3Wk1k.4381$C12.2615@pd7urf3no:

Bob Noel wrote:
In article
,
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!

Don't know why, but don't those transports with negative dihedral
also have wings above the hull? So those aircraft have the CG below
the wings.



And large transport aircraft are amongst the most aerodynamically
stable aircraft to fly.


Actually, that's not the case in every sense. They're not very speed
stable, for instance and thye have other problems with two diferent
kinds of dutch roll, related to sweep, mostly.

Bertie

"Bertie the Bunyip" wrote in message
...

Actually, that's not the case in every sense. They're not very speed
stable, for instance and thye have other problems with two diferent
kinds of dutch roll, related to sweep, mostly.

Bertie

Keep guessing wannabe, got a link?

"Maxwell" luv2^fly99@cox.^net wrote in news:9aF1k.1876$nD3.800
@newsfe15.lga:


"Bertie the Bunyip" wrote in message
...

Actually, that's not the case in every sense. They're not very speed
stable, for instance and thye have other problems with two diferent
kinds of dutch roll, related to sweep, mostly.

Bertie

Keep guessing wannabe, got a link?




Nope. Don't need one.



Bertie

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!


"Negative dihedral" may have more to do with keeping the landing gear
legs shorter. I know that's how they solved the problem they
encountered with the longer gear legs required on the Avro Arrow. On
the original mock-ups, when they first tried to retract the main gear
legs, they "crunched together" with each other at the point where they
entered the fuselage.

Dihedral (whether "positive" or "negative") does tend to *add*
stability, not take it away. Fighter jets and large airliners use "fly
by wire" because the stick forces required to move the control surfaces
may be too much for the average pilot (or might cause a good deal of
fatigue which, on longer flights, could be detrimental to the safe
operation of the aircraft). "Fly by wire" does little toward enhancing
the overall stability of an aircraft. "Stability" has more to do with
the overall design of the aircraft (and it's intended use).

On Jun 3, 7:56 pm, Frank Olson
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!

"Negative dihedral" may have more to do with keeping the landing gear
legs shorter. I know that's how they solved the problem they
encountered with the longer gear legs required on the Avro Arrow. On
the original mock-ups, when they first tried to retract the main gear
legs, they "crunched together" with each other at the point where they
entered the fuselage.

Dihedral (whether "positive" or "negative") does tend to *add*
stability, not take it away. Fighter jets and large airliners use "fly
by wire" because the stick forces required to move the control surfaces
may be too much for the average pilot (or might cause a good deal of
fatigue which, on longer flights, could be detrimental to the safe
operation of the aircraft). "Fly by wire" does little toward enhancing
the overall stability of an aircraft. "Stability" has more to do with
the overall design of the aircraft (and it's intended use).

well what occurred to me is, with negative dihedral, as one wing lifts
it generates MORE lift, while the wing going down generates less. I
thought that would encourage the roll, but maybe the wing design
itself somehow takes that into account..

"Tina" wrote in message
...

well what occurred to me is, with negative dihedral, as one wing lifts
it generates MORE lift, while the wing going down generates less.


Why did that occur to you?

On Jun 4, 12:30*pm, Tina wrote:
On Jun 3, 7:56 pm, Frank Olson



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!

"Negative dihedral" may have more to do with keeping the landing gear
legs shorter. *I know that's how they solved the problem they
encountered with the longer gear legs required on the Avro Arrow. *On
the original mock-ups, when they first tried to retract the main gear
legs, they "crunched together" with each other at the point where they
entered the fuselage.

Dihedral (whether "positive" or "negative") does tend to *add*
stability, not take it away. *Fighter jets and large airliners use "fly
by wire" because the stick forces required to move the control surfaces
may be too much for the average pilot (or might cause a good deal of
fatigue which, on longer flights, could be detrimental to the safe
operation of the aircraft). *"Fly by wire" does little toward enhancing
the overall stability of an aircraft. *"Stability" has more to do with
the overall design of the aircraft (and it's intended use).

well what occurred to me is, with negative dihedral, as one wing lifts
it generates MORE lift, while the wing going down generates less. I
thought that would encourage the roll, but maybe the wing design
itself somehow takes that into account..

To pionts: The swept wing also add roll stability and for heavy low CG
airgraft with high swept wings the anhedral may be large to reduce
excessive stability.

Cheers