This has been asked for, and I took it upon myself to make a post about it so others can be informed and read the facts behind the wind modelling in X-Plane.

Please take the time to read it and watch the video, as there is quite a lot of information, and some of it may be a little too advanced for some people, but Austin always does his best to explain things in an easy to follow manner.

I don't think anyone can debate the accuracy of the wind modelling in X-Plane after taking all of this in.

Dare I say it, but no other sim gets the wind effects this comprehensive and accurate.

Enjoy:

https://developer.x-plane.com/2019/09/experimental-flight-model-changes-in-x-plane-11-40/

https://developer.x-plane.com/2018/05/better-fuselages-through-science/

https://forums.x-plane.org/index.php?/forums/topic/162794-xplane-aerodynamics-and-wind-models/

 

Edited June 14, 20214 yr by GoranM

meanwhile. in xplane

->aircraft altitude drives the windsock.

So while the theory is nice, no one has been reporting the bugs they should have been.

Also, even tho that has now been reported, since that one is obvious (no windsock movement with 13kt winds at 10m) I think it is safe to assume there are many many more that are not so obvious.

2 hours ago, mSparks said:

->aircraft altitude drives the windsock.

It is a known bug.

I am not here to defend any specific Sim, but the phrase "Dare I say it, but no other sim gets the wind effects this comprehensive and accurate." is just not correct.

- MSFS2020 is able to model Wind Interference from Terrain and Structures, as has been appointed in the other thread already

- DCS and IL-2 goes further and models how the PropWash moves the Control Surfaces from being dropped due to gravity to Streamlined with the rest of the stabilizer when you add power.

- Aerowinx PSX simulates Polar / Tropical JetStreams, where you can clearly know when you have entered one Corridor, and your GS will jump like you passed over a Turbo in MarioKart.

So, imo, X-Plane does the Basic right, but feature wise, it's the Sim which has the most ground to cover in the area of Wind / Turbulence simulation. The Turbulence slider in special is just horrible in X-Plane. That thing just makes the Aircraft unflyable, Even Austin has confirmed to me in an e-mail some years ago that is just not correct and needs to be redone.

Not trying to take sides here, all Sims also have serious Flaws, but the crown just can't be given to X-Plane in this area.

 

 

 

 

Edited June 14, 20214 yr by Alec

3 hours ago, Alec said:

I am not here to defend any specific Sim, but the phrase "Dare I say it, but no other sim gets the wind effects this comprehensive and accurate." is just not correct.

- MSFS2020 is able to model Wind Interference from Terrain and Structures, as has been appointed in the other thread already

- DCS and IL-2 goes further and models how the PropWash moves the Control Surfaces from being dropped due to gravity to Streamlined with the rest of the stabilizer when you add power.

- Aerowinx PSX simulates Polar / Tropical JetStreams, where you can clearly know when you have entered one Corridor, and your GS will jump like you passed over a Turbo in MarioKart.

So, imo, X-Plane does the Basic right, but feature wise, it's the Sim which has the most ground to cover in the area of Wind / Turbulence simulation. The Turbulence slider in special is just horrible in X-Plane. That thing just makes the Aircraft unflyable, Even Austin has confirmed to me in an e-mail some years ago that is just not correct and needs to be redone.

Not trying to take sides here, all Sims also have serious Flaws, but the crown just can't be given to X-Plane in this area.

 

 

 

 

Did you even watch the video?

Edited June 14, 20214 yr by GoranM

3 hours ago, Alec said:

- DCS and IL-2 goes further and models how the PropWash moves the Control Surfaces from being dropped due to gravity to Streamlined with the rest of the stabilizer when you add power.

I agree with your whole post, but this one needs clarification. I've already discussed it with Jcomm multiple times in the past.

The control surfaces being moved by propwash/airflow looks cool, but it's fundamentally just aesthetic.

All flight simulators model (in flight) what is known as fixed-stick behaviour. That is because of limitations of pc flight controls (that have no feedback in 99% of cases) compared to real life flight controls. In fixed-stick behaviour, the controls do not move with airflow.

Control surfaces drooping due to gravity and moving with airflow then becomes an aesthetic feature which is just nice to see during takeoff replays.

When the aircraft is actually flying, in DCS (at least last time I tried, and I suppose it's the same in IL2) control surfaces do not react to airflow, because it reverts back to fixed-stick.

It's theoretically possible that some flight sim could model free-stick behaviour in flight, but I think it's unlikely, since that would make aircraft less stable, and decouple surface control movements from pc flight controls movements.

IIRC, XP also introduced control surfaces drooping and reacting to airflow a few releases ago, but I wasn't particularly excited by that. I don't think it increases realism, and could even create issues if it's not implemented correctly.

 

4 hours ago, Murmur said:

I agree with your whole post, but this one needs clarification. I've already discussed it with Jcomm multiple times in the past.

The control surfaces being moved by propwash/airflow looks cool, but it's fundamentally just aesthetic.

All flight simulators model (in flight) what is known as fixed-stick behaviour. That is because of limitations of pc flight controls (that have no feedback in 99% of cases) compared to real life flight controls. In fixed-stick behaviour, the controls do not move with airflow.

Control surfaces drooping due to gravity and moving with airflow then becomes an aesthetic feature which is just nice to see during takeoff replays.

When the aircraft is actually flying, in DCS (at least last time I tried, and I suppose it's the same in IL2) control surfaces do not react to airflow, because it reverts back to fixed-stick.

It's theoretically possible that some flight sim could model free-stick behaviour in flight, but I think it's unlikely, since that would make aircraft less stable, and decouple surface control movements from pc flight controls movements.

IIRC, XP also introduced control surfaces drooping and reacting to airflow a few releases ago, but I wasn't particularly excited by that. I don't think it increases realism, and could even create issues if it's not implemented correctly.

Perfect! Even with a FFB Stick, does it not float free in DCS? I thought I remembered that it did, and when you trimmed the plane, you would see the Stick actually moving.

6 hours ago, GoranM said:

Did you even watch the video?

This is a video I saw a long time ago when Austin launched on his channel. I like watching his presentations, full of enthusiasm and cool theories. But from what I know, most of what he describes there is already implemented also in other Sims. What differs is the way they choose to implement the Prop Effects, PropWash affecting the Tail, etc. But I haven't watched the video now, maybe I'm missing something.

Mostly all Sims nowadays, other than the Legacy FSX/P3D Code, are using some kind of Real Time Flight Model Simulation, the days of Tables for defining all the characteristics of the plane are long gone. That is good, but can be bad in some cases where you loose control over the outcome and have to deal with weird behavior and almost no tools to tweak that.

Edited June 14, 20214 yr by Alec

I'd say, from memory, that the most satisfying model of control deflection due to trim tabs and the effect of dynamic pressure / propwash is the one on IL2 ( at least last time I tested it... ) (*)

Since a few versions ago XP11 with it's experimental fm also started doing it. You can set the trim tabs on your rudder and elevator and whatch teh control deflections on ground, fully braked, as you apply power and your prop is ahead of the fuselage.

Strangely in all of the three sims though, they adhere to a "fixed stick" approach in the end, so, as Murmut pointed out, it's a bit disconcerting to see the end effect, at least for me who never owned a FFB stick.

(*) yet the Spitfires in IL-2 completely fail to model the typical elevator deflection in cruise due to the nose heavy pitch settings used for that phase of flight. The elevator always appears aligned with the horizontal stab 😕 while in the DCS Spitfire it can be seen deflected in cruise... Never checked on Spitfires for XP11.

On 6/14/2021 at 8:45 AM, mSparks said:

meanwhile. in xplane

->aircraft altitude drives the windsock.

So while the theory is nice, no one has been reporting the bugs they should have been.

Also, even tho that has now been reported, since that one is obvious (no windsock movement with 13kt winds at 10m) I think it is safe to assume there are many many more that are not so obvious.

Do you have the "Experimental Flight Model" on?

On 6/14/2021 at 12:19 PM, Alec said:

- MSFS2020 is able to model Wind Interference from Terrain and Structures, as has been appointed in the other thread already

 

 

 

 

 

This is absolute Garbage and has been explained by a ton of add-on dev's who dont shill for the game, It is not modelled it is just a value entered and the sim gives you a bouncy castle effect based on that value, not modelled one bit, pure rubbish!

2 hours ago, a321 said:

Do you have the "Experimental Flight Model" on?

I dont have it checked, the VSKYLABs R44 forces it from planemaker

It also happens in the C172 that doesn't

It also happens with it checked

Did you expect something different? Daniela (does the fmod sounds for LR) got a recreate and submitted the bug report, I guess fixing it just didn't make it onto their todo list (I work around it with a replacement windsock obj with a custom dref)

 

Edited August 9, 20214 yr by mSparks

3 hours ago, a321 said:

This is absolute Garbage and has been explained by a ton of add-on dev's who dont shill for the game, It is not modelled it is just a value entered and the sim gives you a bouncy castle effect based on that value, not modelled one bit, pure rubbish!

The way FS2020 is moving the aircraft around the CG to make it "look like" it is affected by "wind", is particularly nausea inducing in VR like shown in this video:

[BUG/FEATURE] FS2020 is breaking the VR golden rule: don't move the camera, the user is - Virtual Reality (VR) / VR Wishlist - Microsoft Flight Simulator Forums

15 hours ago, RXP said:

The way FS2020 is moving the aircraft around the CG to make it "look like" it is affected by "wind", is particularly nausea inducing in VR like shown in this video:

[BUG/FEATURE] FS2020 is breaking the VR golden rule: don't move the camera, the user is - Virtual Reality (VR) / VR Wishlist - Microsoft Flight Simulator Forums

I don't think all of it is just "random" ...

MFS uses a fancy terrain-induced model, just like XP10 and XP11, but when it comes to turbulence settings, both simulators do a rather poor job...

Experiment with either and set through the "turbulence gui" various amounts of turbulence. It is more detailled / professional in MFS, using the same concept we use in our aviation weather systems, but the ende result on both sims is pretty much the same "hysterical" bouncing ... Laughable

4 hours ago, jcomm said:

but the ende result on both sims is pretty much the same "hysterical" bouncing ... Laughable

This is not my experience at all with XP11, and even less so in VR though. To me, FS2020 is trying to simulate some form of turbulence above ground features, XP11 is not (or not as much if ever it does). However XP11 is trying to modelling the medium the aircraft is flying through and moving with, but FS2020 is modelling the aircraft movement in the medium as perceived on a 2D screen. Switch to VR and you can't help noticing a huge difference between the two, where XP11 is making the aircraft moving around up/down left/right (and rotating PBH according to wind forces on the surfaces), whereas FS2020 is making the aircraft rotating around its CG only (or at least mostly).

If I drop the power suddenly on the PA28 in XP11, I can not only feel in VR the gyroscopic forces acting on the aircraft, but the sudden drop of lift making the aircraft falling, whereas in FS2020 it is flying on rails and doesn't react as "violently" to the change.

Edited August 10, 20214 yr by RXP

I actually wrote a turbulence app for P3D a few years ago.  It worked well but was limited by P3D's flight model.  In P3D the airplane doesn't get lift from its wings...it gets it from tables and works on a central point of the aircraft.  What I did was surround the airplane in up and down thermals that were based on the wind, weather, clouds, aircraft location, etc.  Very light thermals when the wind was light, add some heat and they get stronger, flying into a cloud...stronger.  P3D's API for creating and destroying thermals is extremely efficient and handled it very well.  It was a lot of math and it was cool, even with the table-based flight dynamics.  It wasn't like the "jerking plane around" turbulence you get in the sims...it was the plane responding to moving air...big wide thermals and small tight thermals.  I dreamed of X-Plane and, now, FS2020 having a thermal API that would allow me to try it on those platforms...two sims that have real lift.  Alas, no. X-Plane doesn't have the API and FS2020 is a closed system.  I keep the code around...just in case...cuz, wow, it was cool.  🙂

Edited August 10, 20214 yr by Gregg_Seipp