MSFS2020 New [FLAPS] Section parameters

[donstim]

With the latest update to MSFS2020, there seem to be a number of new parameters and values not documented (of course) in the SDK. For example in the A320 flight_model.cfg file [FLAPS] section,

[FLAPS.0]
Old: flaps-position.1 = 10, 215, 0.25
New: flaps-position.1 = 10, 215, 0.25, 1, 1, 0, 1.5

Anyone have any idea of what the 4 new values at the end of this line represent?

 

[B21-soaring]

I can't find any explanation of what the 2nd & 3rd parameters are for, let alone the "new" ones... any clues would be appreciated.

The first parameter is: degrees of flap, positive is flaps down.

 

[donstim]

Good point, haha!

The second number is the maximum speed for the flap setting, i.e, VFE
The third number appears to be an additional factor applied in some way to the drag coefficient to be used for that flap setting.

 

[donstim]

I guess I'll answer my own question:
1st number: Flap deflection in degrees
2nd number: Max speed in knots (VFE)
3rd number: Drag coeff
4th number: Lift coeff
5th number Area Coeff
6th number: Added Camber
7th number: Aft center-of-lift displacement

 

[B21-soaring]

Wow well done! I have no idea how you managed to find this information. Decrypted a secret Asobo data vault? Contracted with the NSA?

These parameters are really important for the tuning of high-performance flaps (in my case, for sailplanes) - thank you very much for taking the trouble to post.

 

[jcomm]

Thank YOU so much Donstim !!!

One question, since Sebastian mentioned they will add further detail to flap aerodynamics in the next SIM update - are these entries already available, or are these in part the new ones to be added ?

 

[Roy Holmes]

The flight_model.cfg for the A320 covers Flaps.0 which are type 1, trailing edge and Flaps.1 which are type 2, leading edge. The additional 4 numbers only appear on the trailing edge flaps.
The third number for both is the fraction for lift and drag added according to angular position. 0 to 1 for positions 0 to 4.
The remaining numbers are unlikely to be lift or drag coefficients. Typically flaps add less than 1.0 to the wing lift coefficient and drag coefficients are rarely above 0.1. However that is if they are applied as additional to the wing lift coefficient and airplane drag coefficient as in the previous sims. Also they could be non dimensional. I do not know enough about this one to be definite on that or the remaining numbers on the trailing edge. An issue is that 1 and 0 can be values or an indication of parameter validity.
Note the leading edge flaps positions 2 and 3 have the same 22 degrees depression which is most likely an error.
Roy

 

[bstolle]

Note the leading edge flaps positions 2 and 3 have the same 22 degrees depression which is most likely an error.

22 for 2 and 3 is correct. 1 = 18° and full is 27°, at least IRL on the CEO.

 

[Roy Holmes]

Bernt,
Could be something else changes for the last positions. The F-4 I flew years ago had bleed air blowing on the leading edge slats when down and also on the trailing edge flaps in the full down position. The air was bled from the compressor stage of the engines.
Roy

 

[donstim]

For the NEO, the correct slat/flap deflections are:
Conf 1: 18/0
Conf 1+F: 18/10
Conf 2: 22/15
Conf 3: 22/20
Conf Full: 27/40
(Note: This isn't exactly how they are to be put into the FLAPS section in MSFS since MSFS includes some special stuff to allow realistic differentiation between 1 and 1+F based on speed)

As for finding out what the meaning of the additional 4 numbers, you can see this for yourself if you open a project in dev mode and go to the aircraft editor debug screen under the flaps tab. One can speculate all you want about whether or not it's possible for a number to be a certain parameter type. All I'm doing is relating what Asosbo has labeled them. Whether they are actually coefficients (as labeled for 3, 4, and 5), factors or whatever, and exactly how they are applied is not revealed by the labels themselves. I've done some investigating on how they are actually applied, but I haven't finished yet. At least one of the parameters, the last one (concerning center-of-lift movement) I don't think has been implemented yet. At least at the time I tried using it when it first appeared, I found it did not make any difference what value was assigned to it. I believe it is this set of new parameters that they referenced as upcoming improvements at about 7:20 in the latest aerodynamics video, so I would not be surprised if they have not yet been fully implemented.

 

[bstolle]

...MSFS includes some special stuff to allow realistic differentiation between 1 and 1+F

Haven't checked with the latest MSFS version, but until the previous version, 1 is only a fake indication. Concerning aerodynamics there's no difference in the MSFS A320 between 1 and 1+F.
The main flight model problem is that MSFS doesn't simulate slats at all and it's impossible to realistically simulate slatted wings.

 

[donstim]

Haven't checked with the latest MSFS version, but until the previous version, 1 is only a fake indication. Concerning aerodynamics there's no difference in the MSFS A320 between 1 and 1+F.
The main flight model problem is that MSFS doesn't simulate slats at all and it's impossible to realistically simulate slatted wings.

Well I have checked and that is what I am reporting. 1 is not a fake indication. Above a certain speed, if you are in 1+F, it retracts to 1. If you are in the air and go from flaps up to 1, you get 1. If you go from 2 to 1in the air, you get 1+F below the auto-retract speed and 1 if above it. If you are on the ground, you get 1+F.

The issue of slats not being simulated correctly is a different issue, and that issue is still there. Slat are treated the same as flaps, just located at the leading edge. If we're lucky, maybe that will change in the future.

 

[bstolle]

1 is not a fake indication.

It's definitely fake. Just tested. There's no difference between 1 and 1+F.

 

[donstim]

It's definitely fake. Just tested. There's no difference between 1 and 1+F.

Maybe you should try changing the value for the lift scalar for the slats, which would affect 1. They have basically placed all the lift on the flaps, negating the effect of the slats. It is there, though, and if you change the values you can see that 1 is indeed different than 1+F. Or, try it in the FBW mod, where the distribution of the lift between 1 and 1+F has been changed and the ECAM config symbol has been changed to be consistent with the actual configuration the airplane is in. Bottom line: It is NOT Fake.

 

[bstolle]

Bottom line: It is NOT Fake.

Looks like you are talking about something different. I'm not talking about any modifications. On the original MSFS A320 there's simply no difference between 1 and 1+F.
Identical pitch attitude and thrust setting with 1 and 1+F = fake, since only the E/WD indication changes.

 

[donstim]

Yes, we must be talking about different things alright. But you were commenting on a statement I made as if my statement was false. That statement was true, i.e, that Asobo included some automatic flap retraction and flap deployment inhibition logic to allow realistic behavior in the selection and use of CONF 1 and CONF 1+F. The configuration are different regardless of whether Asobo chose in the default airplane not to distinguish them as being aerodynamically different by way of the lift and drag scalars they used in the FLAPS section. In fact, their decision to do that turned out to be a good idea because their auto-flap retraction logic does not work right and causes the F portion to retract to -1 radian (-57.3 degrees) deflection angle. If they had assigned the correct proportion of lift to the flap, ti would have caused the airplane to stall immediately and go into an unrecoverable dive. (Who knows, maybe that was the reason behind their decision to not assign the correct proportion of lift and drag to the flaps.)

By the way, it isn't the slat, i.e., CONF 1, that is the "fake," indication in the default airplane. It is the "F" portion that is "fake." If you look at the flight_model.cfg file and the lift and drag scalars used in the FLAPS sections, you will see that Asobo assigns nearly all of the lift and drag to the slats rather than the flaps. So the F (flaps) portion adds nothing to the 1 (slats) lift and drag.

 

[bstolle]

By the way, it isn't the slat, i.e., CONF 1, that is the "fake," indication in the default airplane. It is the "F" portion that is "fake." If you look at the flight_model.cfg file and the lift and drag scalars used in the FLAPS sections, you will see that Asobo assigns nearly all of the lift and drag to the slats rather than the flaps. So the F (flaps) portion adds nothing to the 1 (slats) lift and drag.

Nope. You can't 'fake' the flaps and Asobo can't assign lift and/or drag to the slats, because there are no slats in MSFS!
If you go from conf 0 to 1, the pitch attitude unrealistically decreases due to the greatly increased flaps lift.

 

[jcomm]

Nope. You can't 'fake' the flaps and Asobo can't assign lift and/or drag to the slats, because there are no slats in MSFS!
If you go from conf 0 to 1, the pitch attitude unrealistically decreases due to the greatly increased flaps lift.

Have a - careful - look into the FBW A32NX MOD "flight_dynamics.cfg", namely :

[FLAPS.0] ; drag, pitch
type = 1 ;

[FLAPS.1] ; lift only
type = 1

[FLAPS.2] ; drag, pitch
type = 2 ;

[FLAPS.3] ; lift only
type = 2 ;

 

[Roy Holmes]

Slats or leading edge flaps are used to allow the wing to go to higher angles of attack (AOA) without boundary layer breakaway. The can delay the stall by quite a lot depending on the wing design. Lack of slats is one of the biggests issues in the sim when designing a swept wing fighter which can be flown to 30 AOA and still be controllable.
If there are no slats in MSFS it is the same as all previous sims, all you can do is assign an increase in the flap CL and Cd. You can get it to start to lose lift at 30 degrees, but the CL/AOA relationship is incorrect at lower angles such as those used in landing. I thought MSFS was supposed to overcome all such issues.
Roy

 

[donstim]

Yep, as I stated earlier, the issue of incorrect simulation of the effects of a leading edge slat remains. You can either obtain the correct Clmax, or the correct CL/AOA, but not both through the cfg file. Flybywire intentionally chose to prioritize CLmax for the takeoff configurations to preserve lift margin at V2. The pitch angles will be incorrect. For the full landing configuration, a different balance was struck so as to preserve proper pitch on final approach. Because the flap provides a higher percentage of the CLmax in that configuration, the lift margin loss for prioritizing pitch is not as great there. The assumption (perhaps wrong) is that with Asobo working more closely with developers than Microsoft ever did, this issue will actually get addressed in MSFS. But I doubt if it will be anytime soon.