Re: Aerodynamic question for you engineers

On Jan 25, 12:22 am, Pete Brown <p...@xxxxxxx> wrote:
If a conventional aircraft is in stable level flight and the stick is
pulled back, all of the texts I have read indicate that the aircraft
pitches up, rotating through  the CG.

Is this exactly correct or is it a very useful approximation good for
all practical purposes?

Most aircraft have the CG located slightly forward of the center of
pressure ( CP or center of lift) for positive pitch stability. I was
wondering if the actual point of rotation is displaced somewhat aft of
the CG, someplace close to the CG but in fact some  small distance
towards the CP.

When the aircraft is subject only to  the force of gravity, any
displacement will cause it to rotate around the cg but in flight its
subject to gravity as well as the aerodynamic forces which act through
the CP, suggesting to me that the point of rotation is not quite on the CG..

Thanks

--
Peter D. Brown

I am not an engineer, so I am going add to your question. Imagine
that you had a couple of tall jack stands that you could place under
the wings to elevate the airplane a foot or so off the ground. Let's
say you place the stands under the wings just back from the CG such
that you have to press down on the tail to keep the nosewheel off the
ground. This is similar to the condition of flight since the center
of lift is aft of the center of gravity. Now if you push down on the
tail, the airplane will rotate about the center of lift. Wouldn't it
work the same way in the air?

Phil
.

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  • Re: Aerodynamic question for you engineers
    ... all of the texts I have read indicate that the aircraft ... subject to gravity as well as the aerodynamic forces which act through ... suggesting to me that the point of rotation is not quite on the CG.. ...
    (rec.aviation.piloting)
  • Re: Aerodynamic question for you engineers
    ... all of the texts I have read indicate that the aircraft ... Is this exactly correct or is it a very useful approximation good for ... subject to gravity as well as the aerodynamic forces which act through ... suggesting to me that the point of rotation is not quite on the CG. ...
    (rec.aviation.piloting)
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