Devices for avoiding VNE?

Arnold Pieper wrote:

The CG is ahead of the Aerodynamic Center of the wing

No ;-)

Although this is one of the most common misconception it's not true.
Except at very forward CG position, the glider CG is *behind* the
aerodynamic center of the wing.

If you don't believe me, check the CG range on your flight manual. And
compare with the mean aerodynamic chord (the aerodynamic center in all
common profiles is at 25% of the chord)

Frankly, that must have come from someone who hadn't finished
reading the whole aerodynamic book yet, and started jumping to conclusions.

You perhaps read the whole book, but unfortunately many books are wrong
(especially those destined to student pilots), in an effort to explain
the stability issue simplier, pretending that the CG must be ahead of
the wing AC...

Anyway we are well out of the subject of this thread ;-)

--
Denis

R. Parce que ça rompt le cours normal de la conversation !!!
Q. Pourquoi ne faut-il pas répondre au-dessus de la question ?

Denis,

Since you're not helping move things in the right direction, I'll explain it
in a bit more detail.

I referred to the Aerodynamic Center, which applies to the isolated wing
analysis, because people were referring to the Center of Pressure, that also
applies to the isolated wing analysis.
The AC does not move, the CP does, however, is the AC that is used for
stability analysis, not the CP.

Anyway :
When you consider the glider as a whole, as opposed to the isolated wing,
there is something called the "Neutral Point", which is the point where the
Lift vector acts considering all aerodynamic forces acting on the glider,
and it too does not move with AOA.
The CG must be always ahead of this Neutral Point, and the Horizontal
Stabilizer/elevator is what keeps them balanced.


"Denis" wrote in message
...
Arnold Pieper wrote:

The CG is ahead of the Aerodynamic Center of the wing

No ;-)

Although this is one of the most common misconception it's not true.
Except at very forward CG position, the glider CG is *behind* the
aerodynamic center of the wing.

If you don't believe me, check the CG range on your flight manual. And
compare with the mean aerodynamic chord (the aerodynamic center in all
common profiles is at 25% of the chord)

Frankly, that must have come from someone who hadn't finished
reading the whole aerodynamic book yet, and started jumping to
conclusions.

You perhaps read the whole book, but unfortunately many books are wrong
(especially those destined to student pilots), in an effort to explain
the stability issue simplier, pretending that the CG must be ahead of
the wing AC...

Anyway we are well out of the subject of this thread ;-)

--
Denis

R. Parce que ça rompt le cours normal de la conversation !!!
Q. Pourquoi ne faut-il pas répondre au-dessus de la question ?

Arnold Pieper wrote:

When you consider the glider as a whole, as opposed to the isolated wing,
there is something called the "Neutral Point", which is the point where the
Lift vector acts considering all aerodynamic forces acting on the glider,
and it too does not move with AOA.
The CG must be always ahead of this Neutral Point, and the Horizontal
Stabilizer/elevator is what keeps them balanced.

Yes. Now I better agree ;-)

The CG must be always ahead of this Neutral Point (the whole glider
Aerodynamic Center) - although the CG may be *behind* the Aerodynamic
Center of the wing (and is actually behind, except in far forward CG
position - or in tailless designs)

--
Denis

R. Parce que ça rompt le cours normal de la conversation !!!
Q. Pourquoi ne faut-il pas répondre au-dessus de la question ?