Re: Prop mass and bsfc figures for YASim

On Tuesday 08 February 2005 02:35, Andy Ross wrote:
> Jim Wilson wrote:
> > I am assuming now you are suggesting that we should apply
> > the weight of the prop in kg to the above simplified formula
> > to get a starting number.
>
> Yes.  Mass in kg, radius in meters.
>
> > What sort of effect would this setting have on YASim
> > specificly? Would this be limited to things like the speed
> > at which RPM increases/decreases?  Should I worry about
> > trying to find a better number for the P-51D?
>
> It would also affect the gyroscopic inertia of the prop, which
> is what causes the nose to yaw slightly at high pitch rates
> (and pitch slightly at high yaw rates).  A *very* high number
> would make the plane difficult to fly and the prop would take
> forever to get to change RPMs -- so much energy would be
> stored in it that it would spool more like a jet.
>
> But I'd expect the numbers would have to be way off to produce
> any real problems.  The steady state flight characteristics
> don't care about this value at all.  When in doubt, aim low,
> I'd guess.
>
> Andy

Thanks to all for the input/comments - at least I should be able 
to come up with some numbers that are in the ball park...

...instead of the car park:)

LeeE

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