X-Plane 11.10 release candidate 1

[jcomm 5,890]

Thx Mario,

I didn't see that one, but indeed I reported it myself and it was assigned the code:XPD-8408

but the betas ( all ) since 7 didn't actually fix it - is still very present.

Emailed Austin about it yesterday and he told me - maybe for 10.20... this and a couple more issues...

 

[MarioDonick 752]

9 minutes ago, jcomm said:

but the betas ( all ) since 7 didn't actually fix it - is still very present.

Emailed Austin about it yesterday

Maybe refer to that bug number and write it again (maybe also to Ben), because if they _think_ they fixed it already, they might overlook it for 10.20 ;)

[jcomm 5,890]

Mario, 

a friend pointed me to a Baron 58 mod available at the .ORG, freeware:

https://forums.x-plane.org/index.php?/files/file/39597-beechcraft-baron-58-double-trouble-hd-flight-model/

and decided to try it out. 

 

First I should point out that at least one aircraft I tested after this new propwash model was introduced didn't suffer from the right rolling tendencies, and always behaved rather plausibly, namely the VFlyteair Grumman AA5.

Now, this modified Baron 58, provided we turn it's aileron ground adjustable trim tab to 0.0158 up to but not exceeding 0.020, also behaves plausibly.

I noticed the author created the wings using as much wing "slices" as he could ( three WING1, 2, 3 + 3 Misc WING ) probably distributting the propwash effects in a way that ballances whatever causes the "new" right rolling tendencies on most aircraft with a CW-rotating prop ( correspondingly  left rolling tendencies for CCW rotating props... ).

Probably most aircraft require the same approach, redesigning the wings and other lift / drag generating surfaces  in order to create the proper interaction between these and the new propwas model calculations ( ? )

[JGregory 76]

1 hour ago, jcomm said:

I noticed the author created the wings using as much wing "slices" as he could ( three WING1, 2, 3 + 3 Misc WING ) probably distributting the propwash effects in a way that ballances whatever causes the "new" right rolling tendencies on most aircraft with a CW-rotating prop ( correspondingly  left rolling tendencies for CCW rotating props... ).

Jose,  multiple wings are mainly available to accommodate the wing and control surface shapes and sizes.  Having "more" doesn't automatically equate to "better".

[jcomm 5,890]

31 minutes ago, JGregory said:

Jose,  multiple wings are mainly available to accommodate the wing and control surface shapes and sizes.  Having "more" doesn't automatically equate to "better".

Yes, but aparently when these fall in the propwash of an engine, being able to set them better proportioned does apparently play a role on the end effect of the new propwash model... At least this is the description available with that Baron 58 mod.

• Smaller wing segments to improve accuracy of prop wash forces

[strider1 575]

20 hours ago, jcomm said:

That one strider, but as far as I can tell, it isn't fixed at all, at least on my tests with the default C172, Baron 58 and the C90...

All of the three still right roll at cruise or higher power settings :-(

I also didn't see any mention of it in the release notes.

I am not seeing the roll to the right anymore on the takeoff climb or the cruise phase of flight in the 172. It will roll to the right or left slightly after a bit, but thats normal in my real world flying experience. The air is in constant motion like the ocean. If you are using a cheap plastic yolk that could be part of it.    

[Susu986 76]

1 hour ago, strider1 said:

I am not seeing the roll to the right anymore on the takeoff climb or the cruise phase of flight in the 172. It will roll to the right or left slightly after a bit, but thats normal in my real world flying experience. The air is in constant motion like the ocean. If you are using a cheap plastic yolk that could be part of it.    

I guess that has nothing to with the quality of the joystick. One just cannot expect to let go of your controller and fly in a straight line, not even in FSX. If you don't touch the controls for a minute, you'll probably enter into a pretty nasty turn. I guess that is normal (but I'm not real world pilot unfortunately). What wasn't normal is that during takeoff your aircraft wanted to weer off the runway unless you've apllied almost full rudder and had screetching tyres, almost drifting while trying to stay to keep the aircraft straight. And that has been fixed, at least on the Cessna, I don't know the others.

[mjrhealth 820]

Far easier ti stear all planes now. Big improvement but still have to get that wind sorted out.

[jcomm 5,890]

5 hours ago, strider1 said:

I am not seeing the roll to the right anymore on the takeoff climb or the cruise phase of flight in the 172. It will roll to the right or left slightly after a bit, but thats normal in my real world flying experience. The air is in constant motion like the ocean. If you are using a cheap plastic yolk that could be part of it.    

Unfortunately for me it's still there, very pronnounced on all of the default props, and certainly noticeable in the default C172.

Even setting the aileron trim tab to 0.000 ( it's set at 0.008 by default, thus causing a right rolling moment which was meant to counter pro effects ) and the engine side can to 00.0º ( it's set at 00.2º right by default also to overcome prop effects ), the right rolling moment is there as you start your climb at climb power.

The default Baron 58 is even worst but the mod whose link I posted above, provided the aileron trim tab is set to no higher than 0.018, will behave plausibly at any power settings, banking right only when the power is brought back for descent - but that's plausible too...

 

 

[strider1 575]

17 hours ago, jcomm said:

Unfortunately for me it's still there, very pronnounced on all of the default props, and certainly noticeable in the default C172.

Even setting the aileron trim tab to 0.000 ( it's set at 0.008 by default, thus causing a right rolling moment which was meant to counter pro effects ) and the engine side can to 00.0º ( it's set at 00.2º right by default also to overcome prop effects ), the right rolling moment is there as you start your climb at climb power.

The default Baron 58 is even worst but the mod whose link I posted above, provided the aileron trim tab is set to no higher than 0.018, will behave plausibly at any power settings, banking right only when the power is brought back for descent - but that's plausible too...

 

 

Ok I tried the default Baron and it is rolling to the right at cruise. I am not seeing the roll in the 172 for some reason.

[Janov 2,383]

Erm, I didn´t read the whole discussion about rolling word for word - but my simple understanding of aerodynamics and Newton´s mechanics would make me think that in a system with rotating propellers there will always be some roll, in one flight regime or power setting or the other. Engines put out torque, propellers create slipstream effects... trimtabs have different effect depending on speed. It would surprise me if there was NO rolling with different powersettings, airspeeds and prop speeds.

Now I know we are all obsessed with one aspect of this simulator or the other - but I think airplanes have trim wheels for a reason and this is becoming a bit of a witch hunt in my view.

Jan

[jcomm 5,890]

1 hour ago, Janov said:

Erm, I didn´t read the whole discussion about rolling word for word - but my simple understanding of aerodynamics and Newton´s mechanics would make me think that in a system with rotating propellers there will always be some roll, in one flight regime or power setting or the other. Engines put out torque, propellers create slipstream effects... trimtabs have different effect depending on speed. It would surprise me if there was NO rolling with different powersettings, airspeeds and prop speeds.

Now I know we are all obsessed with one aspect of this simulator or the other - but I think airplanes have trim wheels for a reason and this is becoming a bit of a witch hunt in my view.

Jan

Janov,

once, by the time of the "unfamous" torque bug - that Austin finally recognized as a bug when Murmur found the culprit with his methodic / scientific approach to the problem (and I should say this new one is almost as intense as it was), Austin replied to a message I sent him saying more or less the same ... "Use the trim..."

The question here is that something is causing an anti-natural rolling moment, just as the torque bug caused a similar one - it isn't perfectionism, but rather, plausibility - and as Austin himself puts, X-plane offers a plausible simulation of the World and the laws of Physics / Aerodynamics...

This being said, I believe that while Austin will probably have to fine tune his new approach to the effects of propwash, truth is that authors that care about designing detailed aircraft using the real potential of X-Plane's sophisticated FDM, should try to adapt their models to the way this effects are presently being simulated. There's a difference between this "bug" and the "torque bug" which is the fact that some aircraft are less prone to it, or even do not at all exhibit it ( the VFlyteAir AA5, and the Baron 58 mod whose link I posted above are examples... ) which proves that in this case, design of the aircraft can really make a difference...

Austin also told me he will revise this and other items - I mentioned to him some inconsistency in the turboprop ( free-running ) model - maybe for 11.20

 

P.S.: Roll trim with which some twin GA are equipped is seldom used IRL. Instead, rudder trim, when not fyling with A/P, is required at various stages / regimes of operation, unless it's a CW - CCW twin... The roll trim inputs which are called for in X-Plane now, and during the "torque bug era", are unplausible... They're used IRL for non-normal operations due to fuel imballance, engine failure, ... In XP11 if we try to keep wings level on most CW-rotating props, and at the same time "center the TC ball" to avoid any sideslip, we enter a pronnounced right roll ( left roll in the case of CCW-rotating props )...

[Janov 2,383]

Hi Jose,

I think you may be right - the aircraft need to be tuned for the new aerodynamics in 11.10. If there is something fundamentally wrong with the flight-model, it should be fixed. I believe that while Austin may have the "basics" right in theory, it is impossible to really quantify the effect and his calculations may be too crude to really yield plausibel results except for some special cases. I don´t think it is possible to really calculate the spiralling slipstream force on a complex shape like an aircraft, at various angles of attack, airspeeds, powersettings. This is beyond the regime of a desktop flightsimulator and I sometimes think it would be better to err on the conservative side instead of adding some new effect that is throwing everything off...

Its correct that the aileron-trim is not really used much in light aircraft, instead the mechanincs will try to "rig" the aircraft so that it flies hands-off wings level in the cruise regime. This may be something that needs to be done to the .acf files to make the planes fly better in 11.10.

However, when using the rudder trim in real life to offset a roll, the result will not always be zero-sideslip flight. Rudder trim is not only used to stop yaw. If the cause of the roll was a genuine roll inbalance (engine torque, asymmetrical load, fuel imbalance, etc.), stopping the roll with rudder will produce a slight sideslip.

Cheers, Jan

 

[Murmur 3,941]

I think the problem here may be multi-faceted.

For one thing, the modeling of propeller slipstream appear to be somewhat stronger than it should, producing a right roll in an untrimmed symmetrical aircraft.

Secondly, as Jcomm said, maybe using coarse wing elements for the aerodynamic surfaces hit by prop slipstream, could exacerbate the problem. So this one is probably not an issue of XP flight model, but something that the aircraft creator must correctly design in Plane-Maker.

Thirdly, from my past experiments, the aircrafts in XP tend to have less dihedral effect compared to RL (although still higher than most aircrafts in MSFS/P3D, where the dihedral effect is usually very weak or absent). The effect of this is that, while in real life a bit of rudder deflection would compensate an opposite rolling tendency with only a small ball deflection (as Janov said), in XP the needed rudder deflection to compensate for opposite rolling is higher, and produced a significantly ball deflection and uncoordinated flight.

This third issue is in theory due to XP flight model, but accurately predicting dihedral effect is not easy, because it involves factors such as the modified flow over wing roots due to fuselage (high wing vs low wing), so this is also something that the aircraft creator should tweak for each specific aircraft in Plane-Maker.

 

[60North 120]

2 hours ago, Murmur said:

Secondly, as Jcomm said, maybe using coarse wing elements for the aerodynamic surfaces hit by prop slipstream, could exacerbate the problem. So this one is probably not an issue of XP flight model, but something that the aircraft creator must correctly design in Plane-Maker.

Right, on a single engine prop, the left and right side wing will have slightly different aoa depending on if the prop in front of it is moving up or down, so different lift.

Quote

This third issue is in theory due to XP flight model, but accurately predicting dihedral effect is not easy, because it involves factors such as the modified flow over wing roots due to fuselage (high wing vs low wing), so this is also something that the aircraft creator should tweak for each specific aircraft in Plane-Maker.

Also correct, a low wing aircraft will have less dihedral effect than a high wing

https://www.dropbox.com/s/o9arneiwo13uvy4/dihedral.jpg