right rolling tendency - XP 11.10 prop aircraft...

[jcomm 5,909]

EDIT ( additional stuff... ): In order to properly diagnose this right rolling moment one should clear first each and every compensation previously in use to counter the prop effects, of course

making sure a backup of the original ACF is saved...

 

- Most of the default or add-on prop aircraft have trim tab set by default in Plane Maker Control Geometry ( aileron and rudder ), which should be changed to 0.000

- Some of the aircraft also have their prop axis canted sideways ( to the right in the case of CW rotating props ). One should bring this side cant to 0.000

- Some of the aircraft ( for instance the default C172s ) have the totality or part of their tail fin also "canted" and in the wings section of Plane Maker, under Vert Stab, the incidences of the various components of the vert stab should also be made 0.000

- Some ( not many ) aircraft also use the Stability Augmentation System in Plane Maker, which should preferably be set to NILL values for testing

- Finally, make sure that when running XP11, in the joystick configuration menu / sensitivity, the Artificial Stability sliders are full left!

 

After all the compensations for the "left turning tendencies" on prop aircraft with CW rotating props have been zeroed, one should try again and see if there's still a right rolling tendency at mid to high / full power settings inflight, at any AoA...

If instead the aircraft tends to start turning left at higher power settings, then we can edit it again in Plane-Maker and poor in, one by one, followed by testing, some compensations, preferably based on RL data.

Pitching moments due to flap deflection are still parametric in XP11 - there's a place where one can define how much the aircraft tends to pitch up / down due to flap deployment - not yet calculated automatically by the FDE.

[Murmur 3,941]

Good post. After making the C172 completely symmetric (except for the CW propeller of course), I set it in cruise at 3000 feet on autopilot and set the rudder trim so that the aircraft was coordinated. At that point, I disengaged the autopilot (centering the controls, but not the rudder trim) and firewalled the throttle.

Result: the ball goes to the right (correct), but it still rolls to the right, while it should roll the other way round (I still remember the old video of Austin where he did this exact maneuver on his aircraft. :-) ).

 

[jcomm 5,909]

Well,just ran the test, displaying wing lift and propwash for checking how they're being calculated. Weather set to preset CAVOK.

There's a good difference between the wing lift from the left to the right wings ( higher overall in the left wings ), at higher power settings, but I did notice a left banking tendency when I :

- Set higher than cruise ( 75 % ) power ;

- Level the wings and try to trim for level flight

- use rudder to bring the ball to the center - here, since the turn coordinator isn't very precise graphically I prefer to start by using SHIFT W and watch the turn coordinator triangle cue in the HUD.

With the aircraft coordinated ( the default C172 "fully symmetric ), I do see a progressive left turning tendency.

EDIT: But running the same test with the C400, the Baron 58 and the C90 results alwys in HUGE right rolling tendency.

It can also be observed on these aircraft that the asymmetry in lift between the left and right wings, inflight it's a lot bigger than in the C172....

 

 

[strider1 575]

2 hours ago, jcomm said:

Well,just ran the test, displaying wing lift and propwash for checking how they're being calculated. Weather set to preset CAVOK.

There's a good difference between the wing lift from the left to the right wings ( higher overall in the left wings ), at higher power settings, but I did notice a left banking tendency when I :

- Set higher than cruise ( 75 % ) power ;

- Level the wings and try to trim for level flight

- use rudder to bring the ball to the center - here, since the turn coordinator isn't very precise graphically I prefer to start by using SHIFT W and watch the turn coordinator triangle cue in the HUD.

With the aircraft coordinated ( the default C172 "fully symmetric ), I do see a progressive left turning tendency.

EDIT: But running the same test with the C400, the Baron 58 and the C90 results alwys in HUGE right rolling tendency.

It can also be observed on these aircraft that the asymmetry in lift between the left and right wings, inflight it's a lot bigger than in the C172....

 

 

It sounds like Austin has some work to do !

I would really like to use my rudder peddles in x-plane some day !

[Murmur 3,941]

I think a flight cycle dump (to the log file) would be needed to check what's going on in the different flight surfaces (wings, stabs, etc.)

[t4murphy 24]

3 hours ago, strider1 said:

It sounds like Austin has some work to do !

I would really like to use my rudder peddles in x-plane some day !

Another topic, but what rudder pedals do you use. I have the saitek combat pedals and they work great.

[Colin Ware 2]

On 10/16/2017 at 9:50 AM, jcomm said:

EDIT ( additional stuff... ): In order to properly diagnose this right rolling moment one should clear first each and every compensation previously in use to counter the prop effects, of course

making sure a backup of the original ACF is saved...

 

- Most of the default or add-on prop aircraft have trim tab set by default in Plane Maker Control Geometry ( aileron and rudder ), which should be changed to 0.000

- Some of the aircraft also have their prop axis canted sideways ( to the right in the case of CW rotating props ). One should bring this side cant to 0.000

- Some of the aircraft ( for instance the default C172s ) have the totality or part of their tail fin also "canted" and in the wings section of Plane Maker, under Vert Stab, the incidences of the various components of the vert stab should also be made 0.000

- Some ( not many ) aircraft also use the Stability Augmentation System in Plane Maker, which should preferably be set to NILL values for testing

- Finally, make sure that when running XP11, in the joystick configuration menu / sensitivity, the Artificial Stability sliders are full left!

 

After all the compensations for the "left turning tendencies" on prop aircraft with CW rotating props have been zeroed, one should try again and see if there's still a right rolling tendency at mid to high / full power settings inflight, at any AoA...

If instead the aircraft tends to start turning left at higher power settings, then we can edit it again in Plane-Maker and poor in, one by one, followed by testing, some compensations, preferably based on RL data.

Pitching moments due to flap deflection are still parametric in XP11 - there's a place where one can define how much the aircraft tends to pitch up / down due to flap deployment - not yet calculated automatically by the FDE.

 I would add, make sure you have nose wheel steering enabled....half the time my sim starts up and it isn't...

[strider1 575]

21 hours ago, t4murphy said:

Another topic, but what rudder pedals do you use. I have the saitek combat pedals and they work great.

Crappy Saitek pedals.