Re: Prop mass and bsfc figures for YASim

Andy Ross <[email protected]>
Newsgroups gmane.games.flightgear.flightmodel
Message-ID <[email protected]>
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

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