J Rollon's Mentor

[Murmur 3,941]

My scientific conclusion :smile: The vertical tail and rudder, are overpowering "torque", with prop wash. Even though torque is enough to easily roll the plane, once we add some other forces, it's overrun. And we haven't even added the lift of the wing, yet. In flight, this prop wash, as a slip stream, will be hitting the top of the right wing, the bottom of the left, and left side of the vertical tail. In addition to lift on the wing, these forces will be offsetting torque, that just the slip stream hitting left rudder, was doing itself.

 

NIce experiments and I agree with the conclusions.

 

If we take e.g. an RV-6 with 180 hp at 2700 rpm, at full power the engine will produce a left-rolling torque equivalent to putting a 30 lbs weight on one of the _tips_ of the wing.

 

If you'd try to do that, I'd assume that, despite the lift of the wings and other forces, the left rolling tendency would be significant? So if this is the case, the reason you don't feel the engine torque must necessarily be because the propwash differentially hits the various surfaces (plus probably engine cant effects) and compensates the original torque.

[jcomm 5,919]

Guys,

 

further to my last post about using, in that particular e4xample, artificial stability to lessen the effects of torque in the X-Aviation MU2-J, without using counter-rotating props ( which is unrealistic ) or messing around with the troque fix ( I couldn't even do it in this aircraft, because it uses sophisticated LUA scripts through Gizmo! ) I would like to add that the best results so far were obtained by setting:

 

 

 

The aircraft when it loads on ground automatically sets aileron trim tab and flaps. You should neutralize the aileron trim before starting your takeoff run.

 

Once airborne, you may use a bit of aileron trim, just a bit, and the aircraft will fly pretty much wings level.  Also, when you neutralize aileron trim and reduce thrust to start your descent, there isn't going to be any tendency for left banking, and the descent will be made wings level!

 

This is, for me, a good compromise....

[Old_As_Dirt 160]

Thanks for your second post Jcomm.  I thought I was doing something wrong as I was all over the place with your first one.  The second one has tamed the MU-2 and, for that matter the B-25 I downloaded from .org today.  Now I can fly without wrestling with the controls.

 

Thanks again for your usual attention to detail.

 

John

 

 

This is, for me, a good compromise....

[jcomm 5,919]

The second one has tamed the MU-2 and, for that matter the B-25 I downloaded from .org

 

Good to know John ;-)  Thx for the thumbs up :-)

 

It's really very easy to edit any prop aircraft and use the Art Stab section of Plane Maker to set those corrections we would be forced to constantly operate on the yoke / aileron trim, to be done automatically for us.

 

Just like with this particular aircraft, the MU2-J, we just have to pay attention to the possibility of the authors having set trim tabs by default, or a script that sets the ailon trim "magically" before you start flying. In the Mu2 the aileron and rudder trim tabs are neutral ( Control Geometry section of PM ) but the LUA script automatically sets flaps and a bit of left trim when you load the aircraft in the RW! I have a couple of keys assigned to center aileron trim and rudder trim, so I neutralize the aileron trim before starting my takeoff roll in the MU2.

 

I uusally try to use values that still require the use of some aileron trim, within what I consider plausible, having no RW experience on the aircraft.

 

I came back to this method, after trying the usual "fix" of setting CW, CCW on multi-engine aircraft, or applying the "TorqueFix" because I really don't like the feel provided by the first or the effects on engine performance of the later.

 

Using the Art Stab you can set above which speed the system starts working ( in this case I chose it to be above 95 Kias so that it would be effective just a bit bellow Vmc, which is 99 KIAS for this twin ).

 

You can try to set your default Art Stab sliders, those found under Settings / Joystick & Equipment / Nullzone, on the left, for pitch, roll and yaw, between 0% ( full left ) and 100% ( full right ). I am using them at 50%. The linearity sliders on the right side of the screen I set them all full left - Linear.

[Old_As_Dirt 160]

All of the "Twins" I have gone there to modify have the same settings, which leads me to believe that the authors do not alter them at all - just leaving the defaults.  I might be wrong, but that's what it looks like.

 

John

[jcomm 5,919]

All of the "Twins" I have gone there to modify have the same settings, which leads me to believe that the authors do not alter them at all - just leaving the defaults.  I might be wrong, but that's what it looks like.

 

John

 

Yes John, true that most authors chose to use realistic parameters. This is maybe the best solution because if some day Austin corrects whatever is still not totally correct, their aircraft will not behave in a weird way.

 

Other authors use the CW . CCW tweak too.

 

But the Mu2 is peculiar in that it uses Gizmo to automatically set a few degrees of left aileron trim ( the two powerful turboprops are CCW on this one ) when you select it from the Aircraft menu and start at the rw. It also automatically sets 2 points of flaps. With the Art Stab tweak you should not forget to neutralize the aileron trim before the takeoff run.

[Old_As_Dirt 160]

Correction on the above... When I opened the Carenado C-340, I found that the Art Stab had been tweaked. They had seemed much better than the others anyway, but I was just looking around and left them the way the author had designed them.

 

John

[jcomm 5,919]

Correction on the above... When I opened the Carenado C-340, I found that the Art Stab had been tweaked. They had seemed much better than the others anyway, but I was just looking around and left them the way the author had designed them.

 

John

 

I don't have the C340, but if it's similar to the Baron 58, Dan did use Art Stab for pitch only.

 

In the 64 bit update he also introduced the Torque Fix in the "avionics.lua" file.

 

While this is a nice finding, I have arrived to the conclusion that the "Torque Fix" has negative impact on engine performance figures and if an author designs an engine with certain parameters in mind and latter on applies the torquer fix, the resulting performance can differ significatively from what was initially designed.

 

Also, since today we learned that Austin is dedicated to find a better solution for the prop effects, I guess we should wait for it, and then all aircraft that presently suffer from the overdone rolling tendencies will most probably behave in a more realistic fashion.

[Old_As_Dirt 160]

I agree and hope that Austin will see fit to "fix" these things, but, in the interim, I appreciate the suggestions you have made in Art Stab and all your efforts in the direction of torque control.  It has been one of the most frustrating aspects during my move to XPX.  I can however, see issues with those aircraft whose authors have worked out these problems.

 

Thanks again,

 

John

[jcomm 5,919]

Yes John, I also looking forward for what Austin is going to bring us :-)  Bright times ahead on X-Plane's land ;-)

 

I've been running a lot os tests with my 3 main GA sims - fsx, xp10 and elite.  I was able to finally figure out why there was one add-on for fsx that had so much "torque effect" resulting in pronnounced bank to the left at higher power settings, but also on a more or less consistent requirement for using right rudder, not common to most fsx add-ons (?) - the Aerosoft DR-400.

 

Well, after more than 1 yr with that aircraft in my hangar, I finally found out what was happening behind the scenes, and why it was so... torki :-)

 

On that model a tweak is used to overcome fsx's inexistent slipstream modelling ( just p-factor and torque ). The "plugin" that comes with the aircraft automatically adds rudder and aileron trim ( aileron trim is not even available in the real and model aircraft, but it's added "in the dark"...) to cause that yaw and roll. Since I have two joystick buttons assigned to neutralize rudder and aileron trim, hitting one of them revealled the trick :-)

 

It's triggered whenever you use some throttle settings, and indeed that DR-400 shows a lot of roll and yaw, and even consistently asks for rudder inputs during turns like described on  aprecious article Larry posted here a couple of days ago ( MANDATORY READ POSTED BY LARRY ), such as on most prop aircraft more rudder being need for left than for right turns, with "outside rudder" sometimes being required on a left turn, and left ( cross-controlled ) aileron on a right turn, to get coordinated.  This effect while present on X-Plane prop aircraft ( even if mild ) is almost absent from FSX prop aircraft, but that DR-400 had it!

 

A trick was used, just as my suggested "antoi-torque" tricks, actually not mine but rather pointed out to me long ago by Goran from LES!!!

 

I'd rather have a trickless sim :-), where we're not forced to use art stab and other strategies, like those hidden trim settings in FSX's Aerosoft DR-400 or the puffers on the XPFR Sbach 400, and I look forward for Austins modifications to the spriraling slipstream and and other factors playing their role on prop aircraft :-)

[Old_As_Dirt 160]

Jcomm,

 

Today I applied the same "fix" numbers to Art Stab for the LES DC-3.  Same stable effect.

 

Thankfully, I can now fly one of my favorite aircraft again - without having to fight what is, by design, a very stable aircraft in RL.  I flew from Keflavik, Iceland to a remote area in upper Iceland in one (It was a R4D) and, even with Iceland's strong winds, the flight was relatively smooth.

 

The Basler - BT67 in FSX is also a great plane to fly as it was a modified DC-3.

 

Thanks again for this "fix" until Austin can get his out.

 

John

[jcomm 5,919]

Thx for the report John :-)

 

You can adjust the "fix" to each aircraft just by setting two of the fields as close as possible to RW data. This is plain guessing of course in as far as most aircraft I have tweaked go :-/

 

 

 

In the "fraction deflection per degree..." adjust the value if you notice that the art stab is doing it's job too agressively ( decrease it ) or not efectivelly ( increase it ).

 

I really look forward for Austin's fixe - that's going to be THE FIX!! :-)