FSX Lua or gauge to perform trim inputs under few conditions

[Leghorn]

Hello, community. I was trying to modify an aircrat's flight dynamics so it would be able to pitch down once thrust is cut during the flare. Unfortunately, i wasn't able to achieve the desired effect. I then decided to cheat fsx by creating a lua or a gauge that will trim nose down by several units only when:
1. Aircraft is 0.1 to 100ft agl
2. thrust is set to idle

So, is this possible and where do i start? Have someone done something similar? I have no knowledge in writing lua nor creating dummy gauges. Any advices are welcome

Best regards,
Vic

 

[gapeters]

Not sure if this will work because of not knowing if the airplane has spoilers in real life or not but....

you could code an XML gauge that if the throttle position is below X and a Y amount of feet above ground level, the spoilers would 'deploy'. You then could adjust the FDE to pitch down when deployed. If the airplane actually uses spoilers, then this will not be a good route.

There might be an easier method by adjusting the FDE as well, but I will let someone else chime in on that.

Greg

 

[Leghorn]

Hi, Greg. Your idea is very good. Unfortunately, i have a 60ton jet in mind that is already equpped with spoilers.. I guess back to the drawing desk.. Thank you though.

 

[EduHir]

I wrote an autoland gauge in XML in FS9. During Roll out trim will be set to neutral.

This is an excerpt of the gauge. Of course you have to adapt it to your conditions.

<!-- Trim Neutral -->
      (A:AIRSPEED INDICATED,knots) 80 &lt;
      17 18 (L:AP_AutoLnd_Status,number) rng      <!-- is used by my gauge ** define you own -->
      &amp;&amp;
      if{
        1 (&gt;L:DSD_TECH_TrimShort_SD,number)
        35 (&gt;L:ThrQ_Stab_Trim_ACT,percent)                                                                       <!-- this is the neutral position -->
        (L:ThrQ_Stab_Trim_ACT,percent) /-/ 163.84 * (&gt;K:AXIS_ELEV_TRIM_SET)                 <!--  and will be set here -->

        (L:AP_AutoLnd_Status,number) 1 + 19 min (&gt;L:AP_AutoLnd_Status,number)
        }
      }

Edi

 

[Roy Holmes]

If your aircraft pitches nose down when thrust is reduced then, under those conditions, the thrust must be creating a nose up moment prior to reduction.
You could probably achieve what you wanted in the flare if you set up the thrust such that it created a nose-up moment.
In practice this is most likely with pod mounted under-wing engines. So I would start working on that and see what happens.
Remember though that the stock Record 400 increases CL through ground effect and that could mask the pitch down. You might try reducing 400 a little
Roy

 

[Leghorn]

Many many thanks, guys.

Edi, i'll definitely check out the gauge you created. Definitely a start for me.

Roy, you are absolutely correct. The moment the engines are creating though isn't strong enough. I have to "move" the engines far below their real position in order to have the desired effect. I played with 400 a lot but unfortunately, it doesn't affect the pitch. Only rate. The only plausible feel i get is when the aircraft is below trim, hence my gauge/lua script idea.. Maybe i'm missing something though...

Thank you again,
Vic

 

[Roy Holmes]

Vic,
If the thrust is insufficient to create the desired nose-up moment, the it may be that the drag is too low.
On the approach the induced drag is quite high especially with a swept wing.
And you can easily increase the flap drag. More realistic I think that artificially altering the engine position.
Have a look at Yves's excellent document "Flight Dynamics in MSFS". Page 36 deals with pitch moments due to propulsion, drag is on page 24 with Appendix 2 covering induced drag.
Roy

 

[Leghorn]

Vic,
If the thrust is insufficient to create the desired nose-up moment, the it may be that the drag is too low.
On the approach the induced drag is quite high especially with a swept wing.
And you can easily increase the flap drag. More realistic I think that artificially altering the engine position.
Have a look at Yves's excellent document "Flight Dynamics in MSFS". Page 36 deals with pitch moments due to propulsion, drag is on page 24 with Appendix 2 covering induced drag.
Roy

Wow. Just wow. How could i miss that?! Thank you for providing me my new bible, Roy! I hope it will answer a lot of questions

Best Regards,
Vic