The problem with joysticks is not the length, nor the shape (stick or yoke), but the fact that the springs pull the controls to the middle of the axes. This is a hardware design issue and can't be corrected with software. But I think this is the main reason why some virtual pilots say they have to fight with their joystick against the torque, and why they think it doesn't exist in their real plane

 

Ah! Now I see your point, but there's a problem...

 

Most GA aircraft don't have aileron trims, so, if the pilots felt such a pronnounced bank/roll tendency like in XPX say, during climb, they would deflect their ailerons to counter it, but the moment they let go, the control surfaces would return to neutral because no other force would keep them deflected. Again, after a while they'd have to deflect them again because the bank/roll would have restarted.

 

Seen from the cockpit, and admiting no other external forces are moving the control surfaces, like gusts & turbulence (  well, guys, btw - one of the reasons I really liked MS FLIGHT, who so many make a joke of, is that it does simulate the effects of such forces in the controls, and you can actually see them moving from outside views but also looking at the yoke / rudder...), the yoke would be centered again.

 

If, on the other hand, the aircraft was equipped with aileron trim, then for a given setting, power, AoA, that would keep the control wheel dflected and it would be seen from the cockpit, but since X-Plane has no such force feedback to the controls, Austin programmed it so that the control ( yoke / rudder ) always returns to neutral, even though it is actually deflected and in RL you would be able to notice it!

 

To test it, pick the default C172, go to 3d panel view so that you can watch the yoke, and use 8 and 0  or your aileron trim joysitck assignements to move the aileron trim tabs. The aircraft will start banking, because the trim makes the corresponding aileron deflect, but your yoke will be still. In RL your yoke would move, just as when you use pitch trim, unlexss you have a stabilizer type trim control like in most airliners...

 

See? Problem is X-Plane does not translate trim settings to yoke / rudder deflection, although the corresponding control surfaces do "internally" deflect, and you can see that in the data output on your screen by chosing the appropriate fields.

 

Even worse, and this woud be great to be added graphicaly, also because it would be realistic - the control surfaces will stay still seen from the outside views of your aircraft.

 

Place yourself behind the Cessna staring at one of the ailerons. Now deflect the aileron trim. Do you see the aileron moving? No!...  But you should...

 

I don't recall how this is modelled in FSX / P3D, but I 'll try to find out latter at home ( although I believe it is modelled in the exact same way... ) , but I do know that both in MS FLIGHT and in DCS World these move realistically, as well as the aircraft controls in the cockpit!

Hopefully a more permanent fix gets implement -- the danger is it doesn't because it would make existing 3rd party AC no loner work because they already compensate for the problem.

 

Thanks for the tip.

See? Problem is X-Plane does not translate trim settings to yoke / rudder deflection, although the corresponding control surfaces do "internally" deflect, and you can see that in the data output on your screen by chosing the appropriate fields.

 

Even worse, and this woud be great to be added graphicaly, also because it would be realistic - the control surfaces will stay still seen from the outside views of your aircraft.

 

Not sure if I understand you correctly, but...

 

X-Plane does move the control surfaces with trim. Take one of the default Vans aircraft and you will see.

 

And with airplane that use 3d objects (.obj) for its visuals, It's just a matter of using the right dataref.

Take the Carenado Archer for example, its control surfaces move with trim. The yoke doesn't, but again it would just need another dataref.

Hmmm, I only used the default C172 :-/

 

But still, the controls stay put ( yoke, rudder...)

 

EDIT:

 

You're right marcus11 - my eyes were not focused ... :-)

 

Anyway, I now think they shouldn't, at least in the C172, stopped on the tarmac, with zero wind.... You should be able to deflect the aileron trim tab (mechanically) but the ailerons themselves shouldn't move - no wind at all....

 

 

Anyway, I now think they shouldn't, at least in the C172, stopped on the tarmac, with zero wind....

 

Ah,

yes, servo tabs / flettner control tabs are not modelled, the trim controls seem to directly deflect the control surfaces.

Ok, I experimented a bit, and here is my procedure to test the effect of the torque parameter on an aircraft:

 

1) In cruise (low altitude cruise works fine), max power, precisely center the ball on the turn coordinator with rudder trim, and precisely level wings with aileron trim.

2) Cut the power, try to keep the ball centered and adjust the rudder trim accordingly. There should be no tendency to roll right (when the ball is centered).

3) Let the speed go down while keeping altitude and ball centered if needed. You should not observe any roll tendency.

3) At low speed (but not too low!) add full power again, adjust rudder trim, and start to climb to maintain the speed low. There should be no roll tendency.

 

Tweak the torque parameter until you can achieve the procedure above. Then, try to find the best value for the aileron trim tab in planemaker.

I you can't get a stable roll for both variable power and variable speed, chose which one you need. Variable power is good for landing the aircraft. Variable speed is good if you don't want to trim when aircraft when accelerating to cruise speed.

 

Do not tweak other parameters. Keep it simple. You never know what the author of the aircraft tried to achieve, and the possible side effects.

 

Pascal

Great Pascal, it makes sense...

 

As she says - "Tengo el presentimiento que empieza la acción" - and this torque fix which sounds a lot like - "Un error convertido en acierto"... - "Creo que empiezo a entender"...

 

I leave you with the beautiful and "Torky Shakira"... certainly an inspiring "Musa" for future uses of this Torque Fix :-)

 

 

http://www.youtube.com/watch?feature=player_detailpage&v=GKlpL4FhzUs

The problem with joysticks is not the length, nor the shape (stick or yoke), but the fact that the springs pull the controls to the middle of the axes. This is a hardware design issue and can't be corrected with software. But I think this is the main reason why some virtual pilots say they have to fight with their joystick against the torque, and why they think it doesn't exist in their real plane.

In the real plane, the stick will just sit there, because of the force of airflow around each aileron. There will (hopefully) be no slop, and no null zone. The spring is doing the same, and doesn't need to be corrected. Built in delays in the software will provide a sense of heavy or light stick forces.....to a degree, but it works. The desktop stick doesn't have to correspond to actual trim settings. Unless the airplane is horribly out of rig, the ailerons wouldn't have enough deflection to worry about, when trimmed.

 

If the simulated airplane rolls into a bank, once the wheels leave the ground, or just starts banking with power changes, then you'd have to move the stick to correct, and feel the springs resistance at the same time. That's where I sense, that I'm making too much adjustments for torque. In reality, depending on power versus weight, you can get a "heavy" wing dip from torque, as the wheels leave the ground, if your flying speed is just enough to get airborne. You would just quickly level the plane with aileron. And unless you're on the verge of a stall, which is going to give a continual wobble, that sense of torque roll, should dissapear. If the sense of the (real)plane wanting to roll continues, then I'd be checking rig, or feel that it's hopeless, and add some draggy trim tabs to compensate. There are companies, that actually re-rig airplanes to perfection, to get rid of unwanted aysemetric trim. Anytime the ailerons are deflected to stay level, you're getting additional drag. Some planes just have crooked wings, flaps, or ailerons....as well as the fuselage itself. Even wheel pants & gear leg fairings that are out of alignment, can cause yaw & roll problems.

 

2) Cut the power, try to keep the ball centered and adjust the rudder trim accordingly. There should be no tendency to roll right (when the ball is centered).

 

 

In the real world, a C-172 will roll to the right when you chop the power to idle.

In the real world, a C-172 will roll to the right when you chop the power to idle.

It should just yaw to the right. Just like my RV6. Both have fixed rudder tabs.

 

edit: Some early radio controlled aircraft had only one channel connected to the rudder. They put enough dihedral into the wings to create some bank with just rudder deflection. Yaw can have a slight effect, with roll, but it wouldn't be enough to normally notice. So take the 172 up, let go of the yoke, and see what happens , I suppose.

It should just yaw to the right. Just like my RV6. Both have fixed rudder tabs.

 

edit: Some early radio controlled aircraft had only one channel connected to the rudder. They put enough dihedral into the wings to create some bank with just rudder deflection. Yaw can have a slight effect, with roll, but it wouldn't be enough to normally notice. So take the 172 up, let go of the yoke, and see what happens , I suppose.

I did, I went flying on saturday ! When i reduced the power to idle and let go of the yolk the nose dropped, and the plane rolled to the right.

 

Edit: I did not bother looking at the turn/slip indicator. But i wonder what it would have indicated. Maybe yawing movement to the right, or an uncoordinated turn the right ?

I did, I went flying on saturday ! When i reduced the power to idle and let go of the yolk the nose dropped, and the plane rolled to the right.

Some other factors to think about. Cessna uses adjustable cam bolts for the rear spars in each wing. They take it up for a test flight, and adjust for any roll at cruise speeds, which could be right or left. An older worn airplane may get periodic adjustments too. With power pulled back, the roll is going to be opposite. One of those companies that re-rigs aircraft, that I mentioned earlier, specializes in Cessnas. They go to the trouble of getting everything straight & corrrect, so that the wings will fly level when symetrical. And when they do, cruise speed is increased because of less drag, that you'll get from tabs, or changing the wing incedence with those cam bolts.

 

I built, what I considered to be the perfectly aligned airplane. Smart level for setting the wings & tail surfaces. Flaps & ailerons were perfectly level from end to end. For the first flights, it actually rolled to the right, which is opposite this "torque roll" factor. Turns out the left aileron had a slightly thicker trailing edge radious than the right. Even my aileron trim tab at full deflection wouldn't stop the bank. However, the stick pressure to level the plane was un-noticeable. And what I mean by that, is that I didn't even notice it, on the three first laps around the airport for the first test flight. On the second flight, I let go of stick pressure. That's when I noticed. It would just bank, but not want to actually keep rolling.

 

Once the aileron radious was matched, the plane would climb out with both ailerons at the same angle, which matches the wing tips & flaps while in the up position. The aileron trim tab also trails straight. The only time, there is a bit of aileron deflection, is for fuel or passenger weight corrections. Rudder does use a tab, because rudder pressure is VERY noticeable, to correct for yaw. This plane has an offset engine (to the right), and no built in offset on the vertical stab.

All of these behaviours can now be replicated in X.Plane 10 too, as they could in the past.

 

MS FLIGHT prop aircraft, mainly the Maule, had roll and yaw to the right on descent when engine is throttled back. So do most of the ELITE models :-) and DCS's P51d, which uses a visibly canted tail fin (kust like the real P51d, it has it's tail rotated CCW relative to the aircraft longitudinal axis)

 

In X-Plane 10  this has always been there, either due to the use of trim tabs to compensate for power at cruise, canted engines with their axis oriented to the right, fins with an incidence, or due to the sometimes called "negative torque" resulting from an inversion of the source of the force that generated that other opposing force. With a prop being moved by the airmass and transmiting that force to the engine crank, there will be an opposing force, only this time the result on the fixation points of the engine to the aircraft ceel will be opposite. On a CW rotating prop, it'll rotate the cell exactly CW... and hence the right roll / yaw

All of these behaviours can now be replicated in X.Plane 10 too, as they could in the past.

 

MS FLIGHT prop aircraft, mainly the Maule, had roll and yaw to the right on descent when engine is throttled back. So do most of the ELITE models :-) and DCS's P51d, which uses a visibly canted tail fin (kust like the real P51d, it has it's tail rotated CCW relative to the aircraft longitudinal axis)

 

In X-Plane 10  this has always been there, either due to the use of trim tabs to compensate for power at cruise, canted engines with their axis oriented to the right, fins with an incidence, or due to the sometimes called "negative torque" resulting from an inversion of the source of the force that generated that other opposing force. With a prop being moved by the airmass and transmiting that force to the engine crank, there will be an opposing force, only this time the result on the fixation points of the engine to the aircraft ceel will be opposite. On a CW rotating prop, it'll rotate the cell exactly CW... and hence the right roll / yaw

Adding more to the discussion.... Since I once again brought this up at Sunday's breakfast with a few pilots, a friend mentioned that he was giving someone some training in his RV. Not enough right rudder was being used to maintain the runway centerline, the plane would drift to the left side, and when they rotated, the wing would dip to the left. Note....with enough right rudder pressure, it doesn't dip. So-- back to this right roll on descent & power pulled back--- are the controls just being let go, and no right rudder added, to compensate for an offset tail, or fixed rudder tab? There really wouldn't be a reason to roll right, unless it's an effect of yaw, and dihedral, etc. Other than that, the real life effect of any right roll, wouldn't be noticeable enough to have to deal with it. There is no sensation of a dipping pull to the right, which needs to be compensated with aileron trim, as long as you're using rudder. And it's rudder.... to compensate for the vertical stab offset or fixed rudder trim tab.

Well, at least theoretically, and assuming:

 

1) The aircraft has no assembly problems - let's assume it's new and perfect!

2) There are no trim tabs being used, aileron or rudder

3) there is no cant built into the engine axis or tail fin

 

then, the "negative torque" on a descent performed with throttle back ( full back and hot air....), can cause a right roll because the opposite force, now applied on the prop by the airmass flowing through it and actually pushing it, wil force the engine to rotate at a higher speed than it "wanted" to, and this wil cause an opposite reaction that will tend to turn the fuselage right.

 

There being no noticeable slipstream forces ( the prop is not really producing thrust, and in the limit can even produce negative thrust - it's acting like an airbrake), some of the forces that could couter the rolling tendency are indeed helping it...