Is setting the stall speed directly still possible?

[MSFS 2020] Questions & Community Discussions Aircraft
1

I’ve been asked to look at an aircraft on which the clean stall speed is too
low, by a significant amount. The geometry is all correct and accurate to the
manufacturer’s information as far as I can see, my next check would be to
adjust the lift v AoA table (in previous sims this was THE primary adjustment
for stall speed, and the table is still present in the flight_model.cfg and
editable in Aircraft Editor). Testing was at sea level (okay, just a touch
above it!) and standard ISA, clear skies. I was not seeing much of a result,
if any, so I made what I would call a drastic alteration - peak was 1.39, I
lowered it to 1.09 and adjusted the entire curve by the same amount. The
aircraft’s behaviour was unaltered, stall speed identical. Questions resulting

  • Should the Lift v AoA table still work, and if not is there anything else we
    can use to directly adjust the stall speed when the correct geometry gives a
    stall speed that is incredibly wide of the mark?
2

Hi, Can you post a screenshot of the Cl/AoA polar graph screen from the
aircraft debug, before the change, and after the change? Thanks, Matt

3

I’m kind of running into the same problem. After experimenting, it seems that
setting the flaps_up_stall_speed seems to control the stall speed, even if
there is more CL available from the CL vs AOA curve. On the other hand, if
there is not enough pitch authority, the plane will stall at a lower AOA than
stall AOA.

4

So after more testing, I confirm that the stall speed will the highest of: -
the reference flaps up stall speed, - the speed corresponding to stall AOA as
defined in the CL vs AOA curve - the speed at which there is no more pitch
authority (no really a stall in that case) So, to have the stall speed
corresponding to your CL vs AOA curve, you can just set the reference stall
speed to 0.

5

Brilliant find - thank you.

6

The REFERENCE SPEEDS section stall speed are not considered at all for stall
computation in the sim so I’m really surprised you see any influence of it.
It’s only used for display and AI/autopilot.
@GrimPhoenix9349 Did you witness this as
well?

7

Yes, by setting the two stall speeds to zero and with no other adjustments,
the stall speed went where I would expect it to with the adjusted lift v AoA
curve. This was checked by at least two other members of the team
independently. You may also have seen reference to certain aircraft suddenly
‘dancing’ in the hangar? This was the only other noticeable change, though
again it did not affect all aircraft that were adjusted to zero.

8

@GrimPhoenix9349 I ran some tests with the
SDK Da62 sample and didn’t notice any influence of those parameters (set to 0)
on the actual stall speed. Curves in the stall debug view are exactly the same
and the Simulated stall speed in the tracking debug panel is always 64-66 for
clean config and 60-64 with full flaps. I don’t repro the hangar bouncing
issue. If you have a package that can repro those behaviours, we’d be
interested to have a look. Regards, Sylvain

9

SWS-Alex Vletsas is the person to talk to, Sylvain - the product we were
looking at was the RV14. Best wishes, Paul.