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boufogre avatar image
boufogre asked MrTommymxr edited

My aircraft won't go above 11.8° AOA


The stall AOA is set to 15° in the lift_coef_aoa_table, the stall protection system is disabled, the simulated stall speed is around 140 kts and the estimated stall speed is 157 kts. The aircraft is not fly-by-wire.

However, as soon as incidence is reaching 11.8°, a nose down command is given (clearly visible on the FD) and the aircraft enters a gentle descent, but doesn't stall and doesn't even get close to the stall AOA of 15°.

Test conditions are ISA, 15.000ft, AP engaged in ALT HLD and HDG HLD, A/T off and thrust to idle.

There is plenty of pitch authority left as the trim is not reaching 100% deflection.

Any idea of what could be causing such a behaviour?


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You are trying to do stalls with the autopilot engaged? I suspect there is something inherent in the autopilot design that prevents it from going to an AOA much above stall warning. If you want to go farther, you will need to turn off the autopilot. If you must use the autopilot, you can get it to a higher AOA, by enabling the stall protection system, but setting the activation parameters far beyond the actual stall AOA. This should get the stall warning activation out of the way (, which may then allow the autopilot to drive the airplane to a higher AOA.

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Thanks for the feedback. The objective was not to stall with the AP engaged, but to understand why the plane would stall before the CLmax as defined in the CL vs AOA curve. I'm using the autopilot as it is better than my manual skills with an XBox controller.
From what I understood, the stall protection system is used only in fly-by-wire aircraft.
Anyway, I think the sim induces the stall when the flaps up reference stall speed is reached and regardless of the stall AOA in the CL vs AOA curve, and it was consistent with the AOA until I set this speed to 0. With the speed set to 0, the plane will stall at the AOA specified in the CL vs AOA curve.

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You will need to test this scenario with the autopilot disabled, so as to rule out either a misconfiguration of the stall protection system or a bug where the stall protection system setting is being ignored.

Could you try that and report back what you get as your stall AoA?



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Krazycolin avatar image
Krazycolin answered

We have no AP on and it's still happening @Mattnischan

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MrTommymxr avatar image
MrTommymxr answered MrTommymxr edited

What's your elevator up limit, also chord angle scalar and CG? Check the pitch debug menu.

Also, Stall flutter is gone, it disappeared a few months ago and hasn't been fixed.

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