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MSFS Do most of the legacy aerodynamics fields not work in the modern FM?

A

Anthony31

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australia
This has been keeping me occupied for the last couple of days.

There are lift, drag, side_force, pitch_moment, roll_moment and yaw_moment fields in the [AERODYNAMICS] section of the flight_model.cfg. As most will know these were the main parameters in the old FSX .air files.

In my experiments I have found none of these will work in the modern flight model used in MSFS. Except for one. pitch_moment_delta_elevator will work. Simply flipping this from a negative number to a positive will invert your elevator controls so I know it works (just make sure pitch_moment_delta_elevator_aoa_table is set to =0.0:1.0, if it is 0.0:0.0 then pitch_moment_delta_elevator will not work and it seems to revert to a default behaviour). Oddly, the roll_moment_delta_aileron and yaw_moment_delta_rudder parameters do not have any effect at all. Trying the same trick of changing from a negative to a positive number has no effect (even after checking their respective tables).

Does anyone else have any thoughts on this? I can understand that none of these should work if you are using the modern flight model and they are included for legacy compatibility but the fact that the pitch_moment_delta_elevator does work is making me question things. Was that a deliberate decision or is it just an oversight?
 
D

Delta558

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wales
Quite frankly, they have been reducing the amount of 'legacy' fields that work each time they introduce a new update and it's ruining any ability we may have to adjust aircraft behaviour. I received a list from Asobo recently of the parameters they use to adjust the handling after the geometry side does its stuff, we're down to eight of the original forty in the [aerodynamics] section. This would be fine if the geometry-based side were accurate enough, but try defining anything other than a perfect cylinder for the fuselage . . .

I get they want to move away from tables. I get that they need to rebuild the flight model from what has gone before. However, to be told directly that the geometry is not precise enough but at the same time not all the tables used to push the behaviours in the right direction work any more - that suggests that we will end up with most aircraft sharing a very generic flight model and we have lost any ability to build in known behaviours. If they had built the geometry based side AND maintained our ability to adjust all parameters, I would think that flight modelling has a future in this sim. As it stands, it really feels like a total waste of time and I would not blame any company for ignoring the core flight model and developing an external flight model if they can.
 
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Anthony31

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Thanks Delta. Any chance you can share that list? I think it probably only contains the drag_coef fields. It seems that at least drag_coef_zero_lift still works. I don't think any of the roll_moment or yaw_moment parameters work anymore. I've put some outrageous numbers in there and it's had no noticeable affect.

Perhaps MSFS will just keep adding more flight tuning parameters if they continue moving away from the old legacy tables.
 
Lagaffe

Lagaffe

Resource contributor
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france
Hi,
It seems that Asobo is working on the flight model (posts on S-O-H) in view of the upcoming release of the Reno race addon, I think to improve a number of points that might blow up in our face with overpowered planes on this kind of races.
Hopefully we'll get some significant improvements for once.
 
D

Delta558

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wales
A couple of points first - this is the ones I have been told they use. I am not saying that the others definitely do not work, but these are the sections under the [Aerodynamics] tab which they adjust and therefore definitely have an effect. The [Flight Tuning] section appears to be where most of the adjustment is made.

lift_coef_flaps
lift_coef_spoilers
fuselage_lateral_cx
elevator_lift_coef
rudder_lift_coef
aileron_up_drag_coef
aileron_down_drag_coef
drag_coef_zero_lift
drag_coef_flaps
drag_coef_gear
drag_coef_spoilers
compute_aero_center
aero_center_lift
lift_coef_aoa_table
 
A

Anthony31

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australia
Thanks Delta

The aileron drag coef can also be edited in the FLIGHT_TUNING section as aileron_up_drag_scalar and aileron_down_drag_scalar but then there is also flap_induced_drag_scalar in FLIGHT_TUNING
 
L

L3M0N

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27
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canada
Delta558 said:
A couple of points first - this is the ones I have been told they use. I am not saying that the others definitely do not work, but these are the sections under the [Aerodynamics] tab which they adjust and therefore definitely have an effect. The [Flight Tuning] section appears to be where most of the adjustment is made.

lift_coef_flaps
lift_coef_spoilers
fuselage_lateral_cx
elevator_lift_coef
rudder_lift_coef
aileron_up_drag_coef
aileron_down_drag_coef
drag_coef_zero_lift
drag_coef_flaps
drag_coef_gear
drag_coef_spoilers
compute_aero_center
aero_center_lift
lift_coef_aoa_table
Click to expand...

pitch_moment_aoa_table does something. If the value is changed to 10 then the wing will be moved really far forward. I guess its simulating changes in pitching moment by moving the wing location with aoa.
 
B21-soaring

B21-soaring

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244
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unitedkingdom
I'm puzzled - in my flight_model.cfg I have modern_fm_only = 1 and my plane flies fine. My MSFS UI Options setting is also for "Flight Model: Modern".

BUT if I simply comment out a listed "legacy" parameter lift_coef_pitch_rate then MSFS crashes-to-desktop when I "resync" the plane, and also CTD's when I try and relaunch MSFS. All returns to normal if I remove the ; which is commenting out that legacy parameter.

So I'm not 100% sure my plane is flying on my computer with the "Modern" flight model or maybe I'm hitting an MSFS bug that affects everyone - any clues appreciated.
 
D

donstim

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unitedstates
B21-soaring said:
I'm puzzled - in my flight_model.cfg I have modern_fm_only = 1 and my plane flies fine. My MSFS UI Options setting is also for "Flight Model: Modern".

BUT if I simply comment out a listed "legacy" parameter lift_coef_pitch_rate then MSFS crashes-to-desktop when I "resync" the plane, and also CTD's when I try and relaunch MSFS. All returns to normal if I remove the ; which is commenting out that legacy parameter.

So I'm not 100% sure my plane is flying on my computer with the "Modern" flight model or maybe I'm hitting an MSFS bug that affects everyone - any clues appreciated.
Click to expand...
I thought they had previously said that these parameters are still used in some way by the autopilot. I will try to get an answer to this.
 
A

Anthony31

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1,009
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australia
B21-soaring said:
I'm puzzled - in my flight_model.cfg I have modern_fm_only = 1 and my plane flies fine. My MSFS UI Options setting is also for "Flight Model: Modern".

BUT if I simply comment out a listed "legacy" parameter lift_coef_pitch_rate then MSFS crashes-to-desktop when I "resync" the plane, and also CTD's when I try and relaunch MSFS. All returns to normal if I remove the ; which is commenting out that legacy parameter.

So I'm not 100% sure my plane is flying on my computer with the "Modern" flight model or maybe I'm hitting an MSFS bug that affects everyone - any clues appreciated.
Click to expand...
I have all the old parameters like that still in the flight_model.cfg but based on my experiences of changing those parameters to see what effect they had I'd say most of them don't work in the modern flight model which is as the SDK now states (they have updated the SDK since my original post).

The fact that MSFS crashes if you leave any of them out isn't surprising really. This is Asobo after all and random crashes are just part of the fun. Or is it because you are using ; to comment out the line? What happens if you just delete the whole line?
 
B21-soaring

B21-soaring

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244
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unitedkingdom
Thanks guys - the SDK docs do mention the autopilot in a different 'legacy' param but not lift_coef_pitch_rate. CTD occurs both with the semi-colon 'comment' and when the line is deleted.

I actually hit the bug because I removed ALL the 'legacy'/'not used by modern flight model' parameters from my flight_model.cfg (diligent me) and MSFS crashed, so I reverted to the old file and randomly commented out only the first legacy aerodynamics parameter lift_coef_pitch_rate and the crash immediately recurred, so I'd suspect the sim will crash if any of the 'required' legacy parameters are removed. I'd have expected to see that clearly reported elsewhere though and Google didn't help me - with a bit if luck it'll find this thread for other dev's.
 
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