Designers learned that offsetting the engjinr to the right, for clockwise prop rotation from the cockpit view, is good way to offset torque tendencies with varying amounts of engine power. Most single engine planes have this offset built into the mount. Some Reno racers keep a straight mount to use left roll as an advantage, since turns are always to the left.

 

Ok, this is interesting information. In this case, a step is effectively taken to help propwash compensate for torque. Now we have to understand why this engine deaxing helps.

 

 

 

We're getting off the right track here, if we start thinking that designs need a different portion of airfoil design to compensate for torque.

 

You're confusing the effect in reality, and what can be done in X-Plane to simulate it. Given the idea to change the wing angle locally, I suggested tweaking the airfoils, because I'm not sure the wing's chord can be locally tweaked.

 

 

Just remember, that what you design in, to compensate for an engine under power, will have the opposite effect, when power is pulled back, and airspeeds will now cause a roll in the opposite direction. This is not good.

 

And this is exactly why we have this discussion. Torque, induced by a spinning prop, physically exists, this is a given fact. So, something has to compensate for it, and compensate relatively to the power deployed by the prop. More prop power = more torque = more compensation needed. The only aerodynamic effect that can be related to power IS propwash ! Furthermore, propwash effect on the plane has to be optimised, in a way or another, in order to fully compensate for torque.

 

We can put me on the attacking side of the line. It's not a case of "feeling" that torque induced roll is unrealistic. It IS unrealistic. I've flown enough airplanes to know different, and so many other pillots I've disussed this with, agree. Austin even talks about eliminating any roll during the test phase of his Lancair. And a real pilot of a XPlane simulated turboprop twin commuter aircraft , certainly made it known that the torque roll, and need to aileron trim, shouldn't be present. This was at X-pilot. The need to trim, irratated him, as it does me. It shouldn't be termed as a "pilot challenge", and then many XP users come to believe that the effect is real.

 

It's difficult to debate with you, you always confuse the symptoms and the causes. The object of this thread is not to object that real aircrafts don't generally have the roll tendency. The object of this thread is to understand how to mimic in X-Plane models what you as a pilot, observe in reality. We see that in reality, builders have to tweak the airframe, or as you said offset the engine to the right. So, we have to do this kind of tweaking in X-Plane as well, because a perfectly symmetric aircraft will have the roll tendency.

For Pascal. I read that the explination for engine offset...... is to move more airflow over the inboard left wing, which of course creates more lift on the left. Lift would also change with power changes. I like that explanation

For Pascal. I read that the explination for engine offset...... is to move more airflow over the inboard left wing, which of course creates more lift on the left. Lift would also change with power changes. I like that explanation

Great, that would explain it very well !

I always misinterpreted engine cant as a change in axis angle, but apparently there's a real shift. Apparently the figures given above by Jcomm, from planemaker, are an angle.

@Jcomm: what happens if we actually shift the engine axis in planemaker ? Does X-Plane take this into account ?

Just an observation. The only reason I stayed with xplane 10 initially is that the Carenado aircraft flew so well (yes never perfect in a sim but good enough for training purposes, and actually nicer imho than most in fs). Something happened about 6 months later that caused this horrible rolling and non ability to trim, so much so that I had to leave the sim. Then something happened after 10.20 that again made them fly great.....

 

I just did a flight in the Carenado V35-calm winds-and was able to trim the aircraft (pitch only) and watch it fly stabilized for about 10 seconds before needing minor corrections-very realistic.

 

I also downloaded a freeware aircraft today-twitchy controls, non stability, and it was retired no sooner than downloaded.

 

Therefore I can only conclude whatever Carenado is doing is the right approach, along with the changes to some of the default aircraft that has also improved them considerably. 

Great, that would explain it very well !

I always misinterpreted engine cant as a change in axis angle, but apparently there's a real shift. Apparently the figures given above by Jcomm, from planemaker, are an angle.

@Jcomm: what happens if we actually shift the engine axis in planemaker ? Does X-Plane take this into account ?

 

Yes, it does Pascal. This was actually the tecnique we used in MSFS some years ago :-) because in that sim, and derivates, there is simply no way to cant the thrust axis... In X-Plane we can do a lot more, including variable thrust axis ;-)

Yes, it does Pascal. This was actually the tecnique we used in MSFS some years ago :-) because in that sim, and derivates, there is simply no way to cant the thrust axis... In X-Plane we can do a lot more, including variable thrust axis ;-)

oh great ! I'll have to dive into planemaker one day

Yes, it does Pascal. This was actually the tecnique we used in MSFS some years ago :-) because in that sim, and derivates, there is simply no way to cant the thrust axis... In X-Plane we can do a lot more, including variable thrust axis ;-)

Not actually true... and let's not get into a long debate of one sim vs another... just want to clarify this...

In FSX you can define the x/y/z position (which will locate the engine) as well as the p/b/h (which will rotate the engine).  There is also variable thrust axis, though I believe its use is in turbines and not props.

 

Now, back to your discussion. :smile:

 as well as the p/b/h (which will rotate the engine).  

 

You're ABSOLUTELY RIGHT!  As a matter of fact, just found an old post of mine, on a thread where, among others, I and my great friend and "teacher" ( RIP ) Ron Freimuth, were debating this and other aspects new to FSX :-) where I wrote:

 

- The cant subject I am referring to is...ThrustAnglesPitchHeading.0 = 0,0 //Thrust pitch and heading angles in degrees (+pitch down, +heading right)a new Engine parameter one can use to align the thrust axis in directions other than the usual long axis of the aircraft.If you make the 2nd parameter equal, say 90.0, you're defining a thrust axis perpendicular to the aircraft longitudinal (z in MSFS) axis.We could use a bit of XML, or even better, "C" programming to make the engine interact with collective setting in the helicopters, for better torque yaw effects.

 

(memories.... I'm getting old... that's what it is...)

 

Here it is :-)