Re: YASim prop discing and turboprop engine

----- Original Message ----- 
From: "Berndt, Jon S" <[email protected]>
To: <[email protected]>
Sent: Wednesday, March 22, 2006 6:08 PM
Subject: RE: [Flightgear-flightmodel] YASim prop discing and turboprop 
engine

    I had considered modeling the change in lift/stall speed for an AC520 
twin in MSFS.
     Full power stall: 40 mph
     Idle power stall: 60 mph.

    Losing one powerplant on a short field approach at 50 mph would clearly 
be catastrophic!

    FS has one 'spoiler' surface.  One can set CL_ds, Cd_ds, and Cm_ds.  By 
controlling spoiler defection with a 'gauge', the Lift could be increased as 
Prop Thrust increased.  Note that would be appropriate only for symmetrical 
throttle settings.

    JSBSim is more tractable than MSFS.  As Jon mentioned below, perhaps the 
new Markup Language would enable setting two independent flap-like surfaces 
which have a virtual deflection dependent on individual Prop Thrust.

    Some time ago I mentioned there is a NASA report on 'Performance of 
Light Twins'.  It goes into a lot of detail on prop effects.  Much more than 
one would want.

    Ron



>   I see. The effect we actually would like to demonstrate to
> the students is that when the airplane flies with power on at
> the near stall condition, the lost of a single engine at the
> low altitude is more dangerous, then the lost of both
> engines, because the single engine lost would result in a
> single wing stall from which the airplane is very hard to
> recover. Do you think thrusters approach may help in this situation ?

> If not, do you or anyone else may be know if the effect of
> the prop flow on lift can be simulated with JSBSim ?
>
> Oleksiy

"Oleksiy,

I don't think anyone has tried this with JSBSim, yet. I've been looking
into this lately, and have been writing an extensive paper on modeling
aircraft with JSBSim. I _believe_ that prop effects on the wing can be
modeled using the newest version of JSBSim-ML (JSBSim Markup Language),
v2.0, due to the inclusion of function specifications. The idea would be
to create both a function for a lift delta due to prop wash for each
engine, and also a function for roll moment delta due to prop wash for
each engine.
.....
Jon"




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