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question

donstim avatar image
donstim asked FlyingRaccoon commented

Stall warning activation point

I don't see any information in the SDK about how the stall warning activation point is determined. I assume it is based on AOA, but how is this triggering AOA determined? Can this AOA be specified, or adjusted?

I did notice that the stall warning activation point is affected by whether or not the airplane has a stall protection system enabled, but I could not find any information on why or how the new stall warning activation point is determined.

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FlyingRaccoon avatar image
FlyingRaccoon answered FlyingRaccoon commented

Hello @donstim

By default, it's computed as 70% of the stall angle of attack.
The stall AOA is itself being computed from the lift_coef_aoa_table, as the AoA that gives the most lift in the [10°;20.5°] range.

If the stall protection is enabled, the stall warning will be triggered if your AoA is above the value provided with the on_limit parameter.

Does that answer the question?

Regards,
Sylvain

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Ahh, so that confirms the results I got from my own testing. For example, where the stall AOA is 15 degrees, the stall warning initiated at an AOA of 10.5 degrees. With stall protection enabled, it was much higher, but did not realize it was associated with the on limit parameter.

Can this be made configurable in some way? I don't know about GA airplanes, but a stall warning at 70% of the AOA for CLmax is inappropriate for transport category airplanes. For transport category airplanes, the regulatory requirement is that stall warning occur at a speed at least 3 knots or 3%, whichever, is higher, above the speed for Clmax. Since MSFS AOA is directly proportional to CL, and CL is proportional to speed squared, the stall warning should be at about a 6% lower AOA than CLmax, not 30% lower. As it is now, the stall warning activates at AOAs well within the normal flight envelope and well away from a potential stall.

The transport category airplane regulations also require the stall warning to occur 5 knots or 5%, whichever is greater, before the actual onset of stall (which occurs after CLmax). This has implications for airplanes with stick pusher systems. The activation of the stick pusher is considered an indication of stall, so the stall warning must occur 5 knots or 5% before the stick pusher activation point.

Regards,

Don

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Hello.


Thanks for your feedback :)
I'll forward your suggestions.

Regards,
Sylvain

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