Jump to content

Sign in to follow this  
Marc320

FA50/ Localiser & crosswind & AP

Recommended Posts

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

Share this post


Link to post
Share on other sites
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

Share this post


Link to post
Share on other sites

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

Share this post


Link to post
Share on other sites

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

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
Sign in to follow this  

  • Tom Allensworth,
    Founder of AVSIM Online


  • Flight Simulation's Premier Resource!

    AVSIM is a free service to the flight simulation community. AVSIM is staffed completely by volunteers and all funds donated to AVSIM go directly back to supporting the community. Your donation here helps to pay our bandwidth costs, emergency funding, and other general costs that crop up from time to time. Thank you for your support!

    Click here for more information and to see all donations year to date.
  • Donation Goals

    AVSIM's 2020 Fundraising Goal

    Donate to our annual general fundraising goal. This donation keeps our doors open and providing you service 24 x 7 x 365. Your donation here helps to pay our bandwidth costs, emergency funding, and other general costs that crop up from time to time. We reset this goal every new year for the following year's goal.


    39%
    $9,930.00 of $25,000.00 Donate Now
×
×
  • Create New...