Re: YASim prop discing and turboprop engine

I was first intended to use YASim due to the fact that we don´t have the
airdynamical coefficients from the manufacturer, and YASim allowes
building a model based upon the geometry instead.

However, availability of the scripting in JSBSim looks like an important
point too.


> 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.

John, would markup language of JSBSim support the direct increase of the
lift, or at least the mentioned above differential flaps extention as a
workaround ?

We do have the flight data recordings form the airplane we are going to
simulate. From experience, is it generally possible to guess the
airdynamical coefficients from the flight data recordings ?

Thanks a lot !

Regards,
Oleksiy

>
> ----- 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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