On 02/06/2007 03:47 PM, Tatsuhiro Nishioka wrote:
> I calculated the position of CG with the equation obtained at:
> http://www.paragonair.com/public/docs/FAA-Handbooks/8083-01_WnB/
> 8083-01_ch08.pdf
> According to this document, the distance from the nose to the CG is
> calculated as:
>
> CGoffset = D - (F*L) / W [1] ????
>
> where D is the distance between the front wheel and the main wheel, F
> is the weight of the front wheel,
> L is the distance between the nose and the main wheel, and W is the
> total weight of the aircraft.
That's a misquotation or misinterpretation of the relevant
formula, as you can easily see by considering the case
where F=0, i.e. all the weight on the main wheels, in which
case the center-of-mass is located at the main wheels.
In that case, equation [1] reduces to
CGoffset = D [2] ????
or in my notation
(Xs - Xc) = (Xf - Xm) [3] ????
or
(Xs - Xc) = (Xf - Xc) (since Xc = Xm)
which will not be true except in some exceedingly unusual
special case.
Here the subscripts have the following meaning:
s stands for spinner
c stands for center-of-mass
f stands for front wheel
m stands for main wheels
For details, including some of the algebra worked out
correctly, see
http://www.av8n.com/physics/cm-calc.htm
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