|
|
 | | From: | Julian Scarfe | | Subject: | Computing performance increase due to CG shift? | | Date: | Fri, 17 Dec 2004 14:12:24 -0800 |
|
|
 |
> My club has a Piper Arrow with an aftermarket 3-blade prop. We're
> thinking of putting the original 2-blade prop back on. The 2-blade prop
> weighs 11 lbs less than the 3-blade one.
>
> Ignoring for the moment the aerodynamic attributes of the prop change,
> and the gross weight change, is there any easy way to calculate the
> performance increase due to the aft CG shift? Moving the CG aft means
> less down-force on the horizontal stabilizer. I'm guessing 11 lbs on
> the nose means 3-4 lbs on the tail to balance it out.
Can't you simply estimate it based on the mainplane needing to lift 3-4 lbs
(approx) less? Performace vs weight is presumably documented, so the CG
shift is equivalent to a change in weight.
In general the weight-equivalent of a CG shift would be the change in moment
divided by the moment arm of the tailplane about the centre of pressure of
the mainplane.
Julian Scarfe
|
|
|
