I have discovered that on takeoff with C172 the plane tends to turn slightly to the right so I need to apply slight left rudder. In other sims like X Plane it is the opposite. C172 plane turns to the left and I need a significant amount of right rudder to stay on the centerline. Same thing in P3D with A2A Cherokee.

I think the latter is the correct and realistic behaviour right ?  

Right!

Well, this could bring a long "conversation" up 🙂

In MSFS 2024 the prop effects of a Clockwise rotating prop surely pull the aircraft left during the takeoff run and in flight whenever you're away from the reference speed for the default riogging of the aircraft (including the default trim tabs ground set for the aileron and rudder).

What probably happened to you, just as it can happen IRL, is that you experienced a significant crosswind component from your starboard side (right) and it was enough to overcome the "left turning tnedencies" induced by the engine of your Cessna and the associated prop.

In X-Plane 12, at present, it actually happens that inflight most aircraft, specially the twins like the default Baron 58 and above all the default C90 behave rather unrealistically, showing in flight and over a wide range of speeds and AoAs, a tendency to bank and yaw to the right, actually requiring a quite counter-intuitive need to trim left... It's due, IMO, to a limittation on how X-Plane 12 presently models the effects of propwash over wing surfaces behind the prop, and as I said above it is particularly noticeable in the C90, even if you edit it in Plane-Maker and zero the trim tabs for aileron and rudder !

Now, strangely the Standard version of MSFS 2024, which includes a Kingair 350, also has this problem. It is probably due to a setting that ASOBO introduced to allow for the modelling of default trim tabs, "aileron_trim_neutral" and "rudder_trim_neutral", and are probably set too high, thus causing those right rolling tendencies, as if it was the C90 and other props in X-plane 12 🙂

Unfortunately these default aircraft in MSFS can't have their fm CFG file edited because they're "cloudy encrypted" 🙂 so we can't fix it.

But MSFS 2024 does model prop effects acceptably IMO. It's not DCS World, but it's good enough, and at least right now a lot more consistent than X-Plane 12 !

Edited May 9May 9 by jcomm

Excellent assessment from @jcomm 👍

 @jfri, you're not doing anything wrong. It's just an odd artifact of the flight modelling. I see it a lot too, even where there is little to no crosswind.

5 hours ago, JYW said:

Excellent assessment from @jcomm 👍

 @jfri, you're not doing anything wrong. It's just an odd artifact of the flight modelling. I see it a lot too, even where there is little to no crosswind.

Will Asobo fix this unrealistic behaviour ? MSFS is supposed to be as real as it get

1 hour ago, jfri said:

Will Asobo fix this unrealistic behaviour ? MSFS is supposed to be as real as it get

Well, every sim is, at most, as real as it can...

But overall MSFS, specially with the new CFD in MSFS 2024, the sim does a pretty convincing job regarding the modelling of prop effects.

The default C172 appears to have them very acceptably modelled, as some rw C172 drivers have stated, and as I posted above I guess your problem was that you were probably not aware of a considerable crosswind component from the right.

 

Edited May 9May 9 by jcomm

4 minutes ago, jfri said:

Will Asobo fix this unrealistic behaviour ? MSFS is supposed to be as real as it get

Did you have a crosswind? 

1 hour ago, jfri said:

Will Asobo fix this unrealistic behaviour ? MSFS is supposed to be as real as it get

I would recommend repeating the test, and set the weather up with a Clear skies profile, with no wind.  The 'opposite side torque' effect is not as bad as perhaps you experienced, when a crosswind is taken out of the equation.

1 hour ago, jcomm said:

The default C172 appears to have them very acceptably modelled

Are you sure? I tested the 172 not too long ago, in zero wind, and as I recall, I didn't see any left-turning tendencies - it went practically straight. 

11 hours ago, jcomm said:

a setting that ASOBO introduced to allow for the modelling of default trim tabs, "aileron_trim_neutral" and "rudder_trim_neutral", and are probably set too high, thus causing those right rolling tendencies,

I'm curious about the entries aileron_trim_neutral and rudder_trim_neutral. I haven't found any references to them in the SDK. I am somewhat familiar with the SDK and use it to adjust different aircraft for more realistic results. Having official documentation would be very helpful for tuning the flight models. Any guidance or links to official resources would be greatly appreciated.

Thank you.

3 hours ago, weaklink said:

Are you sure? I tested the 172 not too long ago, in zero wind, and as I recall, I didn't see any left-turning tendencies - it went practically straight. 

Well, it's the second time I apologize today :-/

I seldom use props in MSFS these days, and mostly fly the buses , so, it had been a while since I fllew the default C172, and other models, so, after reading a few messages in this thread I loaded MSFS 2024 SU5 and went for LPMT, manual weather, wind 0 kt (no gusts ofc...), and I was puzzled to verify that indeed somethin weird happened to most of the default prop aircraft including the C172.

The prop effects during the takeof run are practically inexistent and indeed sometimes there's even a tendency to head right !!! This is completely unexpected to me because in the past I did test this, and although I didn't think it was enough for my liking it was still there for sure.

I will further investigate, and probably open a reqeust at the main forum.

 

 

14 hours ago, LRBS said:

I'm curious about the entries aileron_trim_neutral and rudder_trim_neutral. I haven't found any references to them in the SDK. I am somewhat familiar with the SDK and use it to adjust different aircraft for more realistic results. Having official documentation would be very helpful for tuning the flight models. Any guidance or links to official resources would be greatly appreciated.

Thank you.

I'd like to be able to give you a positive answer, but unfortunately I  can't 😕

And I honestly feel real dumb right now after having read sometime ago about the use of these old / legacy parameters from P3D (maybe even FSX) times that are apparently dead in MSFS although they're accepted by the FM engine 😞

I did see it being used in a few aircraft in FS 2020, and I saw mention of it being used in a youtube video sometime ago by a simmer who mentioned using these, but apparently they aren't actually assimilated by the FM in MSFS...

No prop effects in SU5? - Bug Reporting Hub / Aircraft & Systems - Microsoft Flight Simulator Forums

But since this two old parameters aren't used anymore, this means that MSFS isn't actually able to model a rather basic stuff, at least in the most aerodynamics correct way - trim tabs that are set on ground like in many GA and WW2 aircraft IRL...

In X-Plane it has been possible since AGES! Same in DCS, and in IL-2, and in my presently preferred action sim - Aces of Thunder, which even has a way to help the user adjust those fixed trim tabs by doing test flights, where they can be adjusted even if the aircraft doesn't have pilot adjustable trim on a given axis, and saved for the non-test / combat missions.

I'd say, this is a major limitation in MSFS's FM, specially now they've gone CFD mostly, and none of teh alternative ways to overcome it are satisfactory from an aerodynamics pov !!!

(this is the moment that in the past would make me uninstall a sim in a blink of the eyes 🤣, but I use MSFS mostly for the airliners, and overall I find it so amazing scenery wise that I can't erase it from my disks...)

Edited May 10May 10 by jcomm

4 hours ago, jcomm said:

I'd like to be able to give you a positive answer, but unfortunately I  can't 😕

And I honestly feel real dumb right now after having read sometime ago about the use of these old / legacy parameters from P3D (maybe even FSX) times that are apparently dead in MSFS although they're accepted by the FM engine 😞

I did see it being used in a few aircraft in FS 2020, and I saw mention of it being used in a youtube video sometime ago by a simmer who mentioned using these, but apparently they aren't actually assimilated by the FM in MSFS...

No prop effects in SU5? - Bug Reporting Hub / Aircraft & Systems - Microsoft Flight Simulator Forums

But since this two old parameters aren't used anymore, this means that MSFS isn't actually able to model a rather basic stuff, at least in the most aerodynamics correct way - trim tabs that are set on ground like in many GA and WW2 aircraft IRL...

In X-Plane it has been possible since AGES! Same in DCS, and in IL-2, and in my presently preferred action sim - Aces of Thunder, which even has a way to help the user adjust those fixed trim tabs by doing test flights, where they can be adjusted even if the aircraft doesn't have pilot adjustable trim on a given axis, and saved for the non-test / combat missions.

I'd say, this is a major limitation in MSFS's FM, specially now they've gone CFD mostly, and none of teh alternative ways to overcome it are satisfactory from an aerodynamics pov !!!

(this is the moment that in the past would make me uninstall a sim in a blink of the eyes 🤣, but I use MSFS mostly for the airliners, and overall I find it so amazing scenery wise that I can't erase it from my disks...)

 

Thank you. 

 

If those effects are unsatisfactory, they can be adjusted only on those third-party airplanes. As we know, ASOBO did such a great job (again) in hiding/protecting their aircraft files. 

Anyhow, here are the entries that can be adjusted. There is another issue with how the prop rotation direction is coded. Additionally, some entries have no effect. The situation with these guys is a total mess in many ways. 

 

[piston_engine] 

p_factor_on_yaw = 

 

 

and [turboprop_engine]

torque_on_roll = 

 

Values can range from 0.5 to 2.5 to yield results.

1 hour ago, LRBS said:

 

Thank you. 

 

If those effects are unsatisfactory, they can be adjusted only on those third-party airplanes. As we know, ASOBO did such a great job (again) in hiding/protecting their aircraft files. 

Anyhow, here are the entries that can be adjusted. There is another issue with how the prop rotation direction is coded. Additionally, some entries have no effect. The situation with these guys is a total mess in many ways. 

 

[piston_engine] 

p_factor_on_yaw = 

 

 

and [turboprop_engine]

torque_on_roll = 

 

Values can range from 0.5 to 2.5 to yield results.

Yep I was aware of those, but when CFD is enabled a lot of stuff must happen "behind the curtain"....

What is truly a serious innacuracy is not being able to feel the prop effects even in the c172 which is suposedly the pinnacle of their CFD default creationa 🥴

12 minutes ago, jcomm said:

Yep I was aware of those, but when CFD is enabled a lot of stuff must happen "behind the curtain"....

What is truly a serious innacuracy is not being able to feel the prop effects even in the c172 which is suposedly the pinnacle of their CFD default creationa 🥴

100%, although the correct CFD works wonders and makes up for many shortcomings. To me, it's a paradox: it seems like there are two groups involved in these aerodynamic developments—one that made significant mistakes and another, well-qualified, that understands all the dynamics and develops new solutions to compensate for the errors. 

2 hours ago, jcomm said:

Yep I was aware of those, but when CFD is enabled a lot of stuff must happen "behind the curtain"....

What is truly a serious innacuracy is not being able to feel the prop effects even in the c172 which is suposedly the pinnacle of their CFD default creationa 🥴

I have now tested with some planes with zero crosswind. It seem payware single prop planes at least get the left turning tendency direction correct (JF Piper PA28 Anthony AN-2 Sting ) the default C172 went almost straight with a very small left tendency. So it seem crosswing first played a role

Question is how much right rudder should we need to apply in order to get it realistic ? In X Plane very much is needed almost full rudder input.