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Marc320

FA50/ Localiser & crosswind & AP

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Posted (edited)

Hello Guys, Happy New Year

Each approach under AP with crosswind, aircraft drift and AP doesn't correct it. if i let the AP do i land beside the runway (LHBP 011500Z 20006KT 9999 -RA BKN023 02/01 Q1021 NOSIG) landing 31R

What is the crosswind limitation under AP ?

Cheers!!!

Marc

Edited by Marc320

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Posted (edited)
4 hours ago, Marc320 said:

Hello Guys, Happy New Year

Each approach under AP with crosswind, aircraft drift and AP doesn't correct it. if i let the AP do i land beside the runway (LHBP 011500Z 20006KT 9999 -RA BKN023 02/01 Q1021 NOSIG) landing 31R

What is the crosswind limitation under AP ?

Cheers!!!

Marc

I have noticed this as well. If you are comfortable with editing (with Notepad or Notepadd++) the Falcon50 aircraft.cfg file you can try the below and see if it improves the ILS crosswind issue:

Under the [autopilot] heading in the aircraft.cfg file (which is in the Falcon 50 folder, e.g., C:\......\P3Dv4\SimObjects\Airplanes\FLYSIM Falcon 50\ aircraft.cfg) , make the following two changes by commenting out the original values with // and replace them as shown below

1. change the nav_proportional_control value from 13.0 to 12.0

2. Change the nav_integrator_control value from 0.05 to 0.25

After doing this you will have the following (along with all the other unchanged values).

  [autopilot]
........
nav_proportional_control=12.0 //13.0
nav_integrator_control=0.25 //0.05

...........

After doing this save the aircraft.cfg and restart the sim, or at least reload the a/c. 

If you try this, let us know if you saw an improvement ( I think I did ).

Thx,

Al

Edited by ark

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Posted (edited)

I did a severe 36 Kts 60 degree crosswind test and it fine to me. I was slightly offline compared to no wind. But it held a smooth line and when reached the runway i was at the side of the runway which i would suspect as your constantly being blown off course.

If you increase values it will correct faster but then it will try to keep over correcting. We use these type of numbers so a 45 degree intercept is smooth and not too fast where it constantly over corrects and causes the turn to be late.

AL and I are going to do some more tests and we will update this thread soon!

Edited by Flysimware

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Posted (edited)

As Mark points out above, there is a tradeoff when selecting the AP parameter values.

For the nav_integrator_control value, the higher values eliminate errors more quickly, but this can also lead to 'overshooting' the target (course) somewhat. Typical sim values are about 1.7 to 2.5.

For the nav_proportional_control value, larger values typically mean you get a faster response, but too large a value can lead to instability and oscillations. Typical sim values are about 9 to 16.

Examples:

Airbus A321( nav_proportional_control=12.00, nav_integrator_control=0.25 )
Boeing 747-400( nav_proportional_control=16.00, nav_integrator_control=0.17 )
Bombardier CRJ 700( nav_proportional_control=11.00, nav_integrator_control=0.20 )
The FSW Lear35 ( nav_proportional_control=12,  nav_integrator_control=0.1)
The FSW Falcon50 (nav_proportional_control=13,  nav_integrator_control=0.05)

If as a test case we use a 45 degree intercept of a VOR radial at a speed of 250 Kts, then the smaller nav_integrator_control values of 0.05 and 0.1 do the best job of intercepting the radial with a minimum overshoot. On the other hand, when flying down an ILS at 130 Kts, the larger values do a somewhat better job of eliminating deviations due to a strong crosswind.

The sim default AP code implements some form of a PID (Proportional Integral Derivative) controller, and we are usually 'stuck' with this implementation and its limitations. All we can typically do is select the parameter values made available through the aircraft.cfg file.

I have tried nav_integrator_control values from 0.05 up to 3.0.  If one is willing to live with some initial intercept overshoot at cruise altitudes and speeds, and perhaps use something like 30 degree (vice 45 degree) intercepts of the localizer, then you may want to use nav_integrator_control values in the 1.5 to 2.5 range. On the other hand, if you would prefer to eliminate initial intercept overshoots at the cost of somewhat larger steady state errors (such as during a crosswind ILS), then the smaller values in the 0.05 to 0.1 range would be the way to go. So you can tailor the AP values according to how you fly. To each his own.

It is easy to change the  nav_proportional_control and nav_integrator_control values in the aircraft.cfg file if you are inclined to experiment. The default values can be commented out with a // . For example, to try values of 12.0 and 0.1 for the Falcon 50 we would have under the [autopilot] section:

nav_proportional_control=12.0  // 13.0
nav_integrator_control=0.1  // 0.05

After saving the aircraft.cfg file, you need to reload the a/c.

Finally, it is worth noting the nav_proportional_control and nav_integrator_control AP values have to do with lateral control. There is a similar set of values, such as gs_proportional_control and gs_integrator_control, that have to do with the glide slope, or vertical, control. So if you experiment, make sure you are changing the 'right' values.  😉

More information available here under the autopilot section:

https://docs.microsoft.com/en-us/previous-versions/microsoft-esp/cc526949(v=msdn.10)

Al

Edited by ark

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