Been playing with my 3 civil flight sims yesterday, trying to find out more about this prop-effects subject...

 

1) ELITE is  ( IMO ) way ahead of either MSFS or X-Plane when it comes to relisticaly modelling the prop effects. While ground handling in this sim is rather poor, and once airborne most X-Plane users will certainly classify it with a big "On-Rails" tag, ELITE excels in replicating the prop effects for the different aircraft included in the package. They all react differently, but with very acceptable plausibility to a high power / high AoA situation, requiring foot ( right foot because they're all CW rotating...)  Only if you do not correct on time and let that yaw develop into a yaw-induced-roll will aileron be required.

Also, among the three simulators, ELITE is the one that  by far better represents the lesser effects as you gain speed / dynamic pressure / lower AoA.

 

2) MSFS has the torque bug, just as X-Plane, although it includes CFG parameters for tuning of:

 

- roll due to torque

- yaw due to p-factor (there is no slipstream factor in MSFS, only propwash, but it is not used for this sort of calculations/ effects...)

- thrust axis orientation (vertical / lateral) just like X-Plane - more about this one ahead...

 

Yet, playing with this tuning parameters reveals a very weak / plausible effects in the aircraft performance. I played with the default aircraft and with a payware, and used Hervé Sors tools to monitor the "datarefs" and make sure there was now invisible aileron / trim being commanded in order to cause that much roll.

 

It's true that the aircraft also yaw, and you have to use rudder to counter it, but the pronnounced/overdone roll due to torque is there, even above stall speed - and even at cruise it can still be pronnounced on some aircraft models!

 

Contrarily to X-Plane, MSFS using the above mentioned tuning parameters is far from being effective, and the thrust axis orientation is a joke - I believe it is there because it was planned to be used but probably wasn't even correctly integrated in the final FDM calculations...

 

3) X-Plane. with the "TorqueFix", which I learned in this thread should probably not be used because we can loose it one of these days if LR decided to discontinue it's availability ( it's a legacy parameter from v7 ), can be tweaked to exhibit probably the best prop effects, but not on all prop aircraft!

The excellent XPFR DR-400 which I've been using for my tests clearly has prop effects beyond torque roll. You can clearly watch the yellow (side force) vector on the rigght side of the empenage, due to slipstream effects.

 

Strangely when I try to tweak for instance the Van's RV6, I can't observe any "yellow" vector on the empenage ( fin ) with throttle being increased. What happened to the slipstream on this model? What factors in the design of a prop aircraft in X-Plane make available these effects, or simply clip them?

 

 

I wonder where / how X-Plane 10 models p-factor and slipstream though, and if there are any datarefs that can be used to "tweak" those prop effects?

The thruth is that I have been able to achieve very plausible prop effects with this wonderful, also graphicaly, DR-400 model from XPFR. I truly recommend it!!!!

Sometimes a picture is worth a thousand words...  I will also try to record a movie in ELITE showing the prop effects in action :-)

 

Ths to the "TorqueFix", when this picture was taken, I was almost not dflecting the manche, while on the default DR-400 a lot of right manche would have been required to keep the wings level!  The red circles are "proofs" of the asymmetric slipstream effects calculated by X-Plane.

Mate, you're an inspiration .. no doubt about it! :good:

Thx !  :-)

Strangely when I try to tweak for instance the Van's RV6, I can't observe any "yellow" vector on the empenage ( fin ) with throttle being increased. What happened to the slipstream on this model? What factors in the design of a prop aircraft in X-Plane make available these effects, or simply clip them?

 

These X-Plane Van's models date back to at least X-Plane 8. I don't know why they still include them. Since I'm quite familiar with the real Van's..............I can say that I never enjoyed these particular models whatsover. The (FSX) RealAir Marchetti SF260 & Lancair Legacy are much more like flying an actual RV6. And someday, with a new CPU, I'll have to check out the X-Plane (Tom Kyler's)Falco again. It was also much better than those old RVs.

 

 

 

 

 

 

X-Plane (Tom Kyler's)Falco again

 

Hmmm, don't know what that one is - I'll have to check!

Thx!

These X-Plane Van's models date back to at least X-Plane 8. I don't know why they still include them.

 

As far as I remember, Austin introduced them in X-Plane 9! I still have an v8 install and the Van's aircraft are not part of it. I recently updated my v8 install to 8.64 (the last version of XP8) using the installers which are still available at x-plane.com.

 

The Vans aircaft folder contains a text document where Austin explains his thoughts on them.

 

Partial quote of it:

 

OK so what are these planes?

And why are they all gray?

 

Here is the deal: Vans (www.vansaircraft.com) makes very popular homebuilts.

 

So, we have the complete line of Vans aircraft here.

 

Why?

 

I give you these files for 2 reasons:

1: For people BUILDING Vans aircraft to practice flying their birds on the sim BEFORE first flight so they can build proficiency in the sim and be SAFER on your first flight in YOUR RV!

2: For people already flying RV's so they can practice crosswinds, poor weather, formation, and IFR flying in the sim to make them more proficient when they tackle these jobs in the air (as RV pilots often do).

So, with this in mind, I give you these RV files to keep build proficiency in the sim if you are building, or flying, a real RV, for the purposes of preparing for first-flight and maintaing proficiency.

Now, of course, I have one WARNING!

These planes are very GENERIC instances of each RV!

I DON'T KNOW what the V-speeds will be, exactly, for your particular RV.

I DON'T KNOW what the engine will be, exactly, for your particular RV.

I DON'T KNOW what the prop will be, exactly, for your particular RV.

I DON'T KNOW what the weights will be, exactly, for your particular RV.

I DON'T KNOW what the paint will be, exactly, for your particular RV.

So, these planes are the complete line of RV craft (in the tail-dragger config where appropriate), with very 'average' engine, prop, weight, and V-speed configuration, and simple gay primer for paint.

You, as an RV builder or flyer, must now MODIFY any of these craft in Plane-Maker to be the same as YOUR ACTUAL RV! That way, you can use these 'default starting-point' craft to get to your particular RV in no time flat.

...

 

These Van's RV's are updated to v10 file format and even if they were not, wouldn't make them act strange in XP10.

They might not fly exactly like in XP9, but that's because XP10's core FDM is not exactly the same as XP9's, as Austin made some minor updates/refinements for XP10.

 

Hm..,

I get the yellow vectors with the RV6:

 

 

 

 

Yes marcus, got that too even in flight...

 

Thx!

 

 

Ths to the "TorqueFix", when this picture was taken, I was almost not dflecting the manche, while on the default DR-400 a lot of right manche would have been required to keep the wings level!  The red circles are "proofs" of the asymmetric slipstream effects calculated by X-Plane.

So jcomm, you did apply the " torque fix" to the DR-400?  I am a little confused, sorry not an expert here. So do we apply the fix or not? I have heard somewhere that the torque issue is going to be fixed by LR in 10.30. I hope it's true.  Of course not being a RL pilot does not help either  but I found the plane much easier to fly in X-Plane.  Many people told me that it's easier to fly real aircraft than the simulated one.  However, I don't have the resources nor time to fly the real one.  LOL

Hi Vu,

 

yes I applied it to the XPFR DR-400, with great success :-)

 

It now behaves a lot better than one I have for P3D, which is plagued by torque roll just as normally x-plane prop aircraft are :-/

 

I look forward for an official fix, because this one we're using is based on a legacy dataref type... and can change at any moment if LR decided to implement it differently.

 

On a RW DR-400 depending on being or not equipped with trim tabs ( rudder ), there can be a lot of right foot work required almost during all flight, unless you dn't mind flying in a sideslip. Bank will not be a factor!

 

Meanwhile Austin replied with a very plausible answer to the fact of not being available, just as we have in FSX / P3d ( even if somehow useless) modifiers for tuning of p-factor and other prop effects.

 

I'm overall very satisfied with the results achieved with the TorqueFix :-)

 

 

3) X-Plane. with the "TorqueFix", which I learned in this thread should probably not be used because we can loose it one of these days if LR decided to discontinue it's availability ( it's a legacy parameter from v7 ), can be tweaked to exhibit probably the best prop effects, but not on all prop aircraft!

 

Hi, jcomm. I read about torquefix recently, and was wondering if its application was limited to Carenado airplanes. The post I'd read referred to Carenado airplanes needing torquefix to correct their roll problem. If I can in fact use it for my freeware airplanes it would help to end the mildly frustrating roll tendencies in most of my propjobs.

 

 

APUtech

Just to add........ I talked to a friend today, who flew the 2700 horse power Douglas Skyraider in Vietnam. It's just a big single engine radial powered aircraft. The second largest piston engine, used by the US military, and the same that was used in the B-29 bomber (Wright 3350). I asked him about aileron use for engine torque roll in the climb. He said that was the wrong control. It's rudder that's needed.